qid int64 1 4.65M | metadata listlengths 3 3 | prompt stringlengths 31 25.8k | chosen stringlengths 17 28.2k | rejected stringlengths 19 40.5k | domain stringclasses 28
values |
|---|---|---|---|---|---|
7,036 | [
"https://stats.stackexchange.com/questions/7036",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/2775/"
] | This question may have been asked before, but I couldn't find it. So, here goes.
From about 3000 data points that can be characterized as "wins" or "losses" (binomial), it turns out that there are 52.8% dumb luck wins. This is my dependent variable.
I also have some additional data that may help in predicting the... | I wonder what it means to be "99% sure."
The code seems to equate "dumb luck" with $p$ = 52.8% probability of wins. Let's imagine conducting $N$ trials, during which we observe $k$ wins. Suppose, for instance, $N$ = 1000 and you observe $k$ = 530 wins. That's greater than the expected number $p N$ = 528, but it's s... | <pre><code>numtri[c(min(which(perwin <= 0.55)),max(which(perwin >= 0.55)))]
</code></pre>
| https://stats.stackexchange.com |
456,247 | [
"https://physics.stackexchange.com/questions/456247",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/193832/"
] | I am currently looking at the theory of find the viscosity of and object through damped harmonic motion, and tho it can be done there is obviously a limitation with regrades to the medium. If the medium is too viscous then critical dampening will occur and we lose the ability to find the viscosity.
I was looking at t... | The solution to <span class="math-container">$m \ddot{x} + k x + c \dot{x} = 0$</span> can be characterized with the following parameter substitutions
<ul>
<li><span class="math-container">$ k = m \omega_n^2 $</span></li>
<li><span class="math-container">$ c =2 \zeta m \omega_n $</span></li>
</ul>
<blockquote>
<sub... | I assume it is a mechanical system that you are using and possibly a spring-mass system?
Having made the assumption that the resistive force is proportional to the speed of the mass, the equation of motion for a system undergoing free oscillations is <span class="math-container">$m\ddot x + b\dot x + kx =0$</span>.
... | https://physics.stackexchange.com |
3,616,655 | [
"https://math.stackexchange.com/questions/3616655",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/770166/"
] | I want to know whether it is analytic - and if so, to find <span class="math-container">$ f´(z)$</span>
What I do:
I use the polar form.
<span class="math-container">$ z= x + iy \\ |z|=r \\ \bar z= (cos (\phi) + isin(\phi))$</span>
then: <span class="math-container">$ f(z)= r^2(cos (\phi) + isin(\phi)) = r^2cos ... | Put <span class="math-container">$z=r.e^{i\theta}$</span> for polar coordinates then <span class="math-container">$f(r.e^{i\theta})=r^2(cos\theta-isin\theta)$</span>.
You can see that the real part <span class="math-container">$u(r,\theta)=r^2.cos\theta$</span> and imaginary part <span class="math-container">$v(r,\the... | <strong>Hint</strong> If <span class="math-container">$f(z)$</span> would be analytic on any disk, then so would be
<span class="math-container">$$g(z)=zf(z)=|z|^3$$</span>
Now, it is trivial to show that this function is nowhere analytic. This follows immediately from CR, or via many other simple methods.
| https://math.stackexchange.com |
108,642 | [
"https://cs.stackexchange.com/questions/108642",
"https://cs.stackexchange.com",
"https://cs.stackexchange.com/users/94919/"
] | Given a sorted array of distinct integer <span class="math-container">$A[1,2.....n]$</span> the tightest upper bound to check the existence of any index <span class="math-container">$I$</span>, for which <span class="math-container">$A[I]=I$</span> is equal to _______________ ?
<hr>
I thought here answer that mean ti... | If the array had <span class="math-container">$A[i]=i, \forall{i}$</span>, then the complexity would have been <span class="math-container">$\theta(1)$</span> as then all we need to check whether the length of the array is greater than the element or not. If it's greater we have the element, else we haven't.
But the ... | Take the hints. The integers can be positive or negative, but they are <em>distinct</em>. The array is sorted, which usually means a1 ≤ a2 ≤ a3 ... But the are distinct, so a1 < a2 < a3 < ... And they are integers, so they are at least 1 apart. So we have a2 ≥ a1 + 1, a3 ≥ a2 + 1, a4 ≥ a3 + 1 and so on. What d... | https://cs.stackexchange.com |
726,572 | [
"https://physics.stackexchange.com/questions/726572",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/345077/"
] | So I have an issue with the following classical problem:
<blockquote>
Let's say you are on a swing of length <span class="math-container">$l$</span> hanging downwards, and you get pushed in a horizontal direction with speed <span class="math-container">$v_0$</span>. How large should this speed be so that you'll swing a... | <blockquote>
Clearly, some force due to the swing acts on the object at its end (otherwise the object wouldn't go up in the first place).
</blockquote>
Yes, but that force does no work since at each point the force is perpendicular to the velocity. In this problem the only force which has a component that is not perpen... | If you perform this experiment in a room-sized vacuum chamber, energy is ideally conserved.
The loss of energy in an open environment will be due to air friction, there will be a drag force in the direction of the velocity vector
<span class="math-container">$$F_D=\frac{1}{2} \rho v^2 C_D A$$</span>
<span class="math-c... | https://physics.stackexchange.com |
88,590 | [
"https://cs.stackexchange.com/questions/88590",
"https://cs.stackexchange.com",
"https://cs.stackexchange.com/users/84965/"
] | I am trying to learn the Big O notation through the example below, can you help?
Let S be a set of n vertexes of a graph G and R be a set that the set of edges of G. Specify an upper bound of the size m of R with the big O notation. The bound shall be as tight as possible.
Are upper bound of the size m and runtime tw... | you can prove it by taking some set of vertices say four (v1,v2,v3,v4).
Now you are asking of Big Oh(greatest upper bound ...tightest most precisely )
note:this prove is for simple graph(see wiki)
now place the vertices like:
<h2>v1 v2</h2>
<h2>v4 v3</h2>
{in shape like rectangle}
just think what will be maximum... | <blockquote>
Are upper bound of the size m and runtime two different concept?
</blockquote>
The concept is just upper bounding. It doesn't matter whether you're bounding the number of vertices in a graph, the number of steps a program takes to execute, or the number of elephants in India – it's just an up... | https://cs.stackexchange.com |
625,238 | [
"https://physics.stackexchange.com/questions/625238",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/243431/"
] | I found a problems where a particle was moving under a potential <span class="math-container">$V(r) = kr^2$</span> and with a wave function <span class="math-container">$ \psi(r,t) $</span>. If the wave function is changed to <span class="math-container">$ \psi(ar ,t) $</span>, the ratio of average kinetic energy of f... | I think to answer your question, the point of the <span class="math-container">$V(r) = kr^2$</span> is not to distract, but because in one of the integrals you will need to make a change of variables <span class="math-container">$R = ar$</span> and you will get an <span class="math-container">$a^{-2}$</span> factor fro... | Try writing out the S.E.
<span class="math-container">\begin{equation}
\frac{-\hbar^2}{2m} \Delta\psi+kr^2\psi=E\psi
\end{equation}</span>
although cumbersome, it may be helpful to just solve the equation outright. In general it is not a good idea to assume the wavefunction is linear (this would usually make the wavefu... | https://physics.stackexchange.com |
4,441,169 | [
"https://math.stackexchange.com/questions/4441169",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/338164/"
] | This is a broad question which might not have a clear answer. I am aware that the incompressible NS equations can be used to approximate the compressible when the Mach number is low, and that this approximation is validated by results in functional analysis.
However, I am currently wondering what the 'use' is for this ... | There are several points that Wraith1995 made that experts in incompressible flows would take exception with.
While it is true that the incompressible assumption circumvents challenging aspects such as shocks and reduces the number of unknowns, it introduces a host of other issues. In my opinion, these can often be jus... | The incompressible case is easier; I don't think it is stated in any source directly (because it is just known), but it is well known and I can tell you why. The incompressible case simplifies the physics and the space of degrees of freedom by assuming that <span class="math-container">$\nabla\cdot u = 0$</span>. Physi... | https://math.stackexchange.com |
595,572 | [
"https://stats.stackexchange.com/questions/595572",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/137303/"
] | I am following a book which states that the diagonal elements of <span class="math-container">$C = (X'X)^{-1}$</span> are called the variance inflation factors:
<span class="math-container">$$
VIF_j = C_{jj} = \frac{1}{1-R^2_j}
$$</span>
where <span class="math-container">$R^2_j$</span> is the coefficient of determinat... | Yes, it is correct.
To put the discussion under the measure-theoretic conditional expectation/probability framework, first let's clarify the exact meaning of the notation <span class="math-container">$P(G = 1 | Z = 1, \eta)$</span>. As <span class="math-container">$P(G = 1 | Z, \eta)$</span> is <span class="math-conta... | Using the antecedent conditions in your post you have:
<span class="math-container">$$\begin{align}
\mathbb{E}(G \times \eta|Z=1)
&= \int \eta \cdot p(\eta,G=1|Z=1) \ d\eta \\[6pt]
&= \int \eta \cdot \mathbb{P}(G=1|\eta,Z=1) \cdot p(\eta|Z=1) \ d\eta \\[6pt]
&= \int \eta \cdot p(\eta|Z=1) \ d\eta \\[10pt]
... | https://stats.stackexchange.com |
653,703 | [
"https://electronics.stackexchange.com/questions/653703",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/8534/"
] | I am looking at thick film chip resistors. If a 2512 resistor has a 2W power rating, can I parallel two to get 4W total power rating?
Will the heating of the resistors increase resistance so as to automatically balance the current?
| This is fairly commonly done; two identical resistors can be put in parallel or in series to equally share power between them. If you use four (two series, two parallel), you can even have each one be the same resistance as the desired overall resistance, which may be convenient.
Most materials have a positive temperat... | Yes, you can do this. However, it’s best to put them in series, in case one resistor overheats and fails open it will disconnect the second one. That won’t be the case if they’re parallel: one would fail, then the next would be taking the entire load and would eventually fail as well.
The series case where one fails is... | https://electronics.stackexchange.com |
1,490,678 | [
"https://math.stackexchange.com/questions/1490678",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/215665/"
] | Let $X$ be a matrix with 2 rows and 2 columns.
Solve the following equation:
$$ X^2 = \begin{pmatrix}
3 & 5\\
-5 & 8
\end{pmatrix} $$
Here is what I did:
Let $ X = \begin{pmatrix}
a & b\\
c & d
\end{pmatrix} $. After multiplying I got the following system:
$$ \left\{\begin{matrix}
a^2 + bc = 3\\ ... | We have the following criteria which you already stated correctly, but you missed one more information $(5)$ - still, you can solve this root problem without this additional knowledge by plugging in recursively - which comes from the determinant, we get then
\begin{align}
a^2 + bc &= 3 \tag1\\
ab + bd &= 5\tag... | A nonsingular $n \times n$ matrix $M$ will have some square roots that are polynomials in $M$ of degree $\le n-1$. Thus in this case we can look for solutions of the form $X = s M + t I$. By the Cayley-Hamilton theorem,
a matrix satisfies its characteristic polynomial: in this case the characteristic polynomial is $p... | https://math.stackexchange.com |
174,655 | [
"https://electronics.stackexchange.com/questions/174655",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/61608/"
] | I've a doubt about clock domains and synchronization FF. I'm working on a FPGA and I've two clock domains. In the firs clock domain there is a clock frequency of 125 MHz, in the second the frequency is generated by a PLL that has in input the 125Mhz and it generates a 12.5 MHz.
Are syncronization FFs, between the clo... | Since you use a PLL to generate your 12.5MHz clock, the phase relationship will be kept by the synthesis tool, whatever it is. This means the timing analysis will properly report any path between the two clocks and will tell you if it can't satisfy the setup/hold relationship. The clocks will also likely be edge-aligne... | This is going to depend on the delay which the PLL produces. If the PLL produces zero delay, that is, a 12.5 MHz clock edge is perfectly aligned with a 125 MHz clock edge, then there should be no problem. If you are transferring data from the 12.5 MHz domain to the 125 MHz domain (for example), and the 125 MHz clock la... | https://electronics.stackexchange.com |
43,013 | [
"https://cs.stackexchange.com/questions/43013",
"https://cs.stackexchange.com",
"https://cs.stackexchange.com/users/34069/"
] | I know when I compile my C program to machine code it gets compiled into something that specific computer can understand
But I thought computers can only understand 1's and 0's (high/low) so why doesn't my program look like a bunch of strange symbols and not 1's and 0's?
ie: "UHâÂHÉÏHç=7∞Ë1…âE¸â»HɃ]√êˇ%¶LçïASˇ%ÖêhÈÊ... | This is a result of the program that opened the file.
All files on the system are in binary. What matters is how you interpret it.
The editor you used has displayed the digits in their common form:
"UH...." is the equivalent hexadecimal "5548...." which is binary "101010101001000...."
Thus you need a Hex or Binar... | Machine/object code is specific to the interpreter/parser. What you mean to say by "1's and 0's" is binary code, which is what is presented to the machine when the interpreter/parser receives the machine/object code as input.
| https://cs.stackexchange.com |
30,448 | [
"https://physics.stackexchange.com/questions/30448",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/8449/"
] | A question kept bothering me about the Non-Equilibrium Statistical mechanics, can somebody give a simple description of how one approaches this subject? Is there a exact formalism, as we have for Equilibrium Statistical Mechanics, or is it some kind of an approximation? I would also like to know the promising efforts i... | There exist an exact formalism to treat non equilibrium statistical mechanics. You start to write down the Hamiltonian for the N interacting particles. Then you introduce the distribution function in the phase space $f(r_1,r_2...r_n,p_1,p_2,...p_n,t)$.The time evolution of this distribution function is generated by the... | In principle, nonequilibrium statistical mechnaics is exact like quantum theory in general. But to do actual computations in realistic systems you need to resort to approximations.
For modern expositions, I'd recommend the books ''The theory of open quantum systems'' by Breuer and Petruccione and ''Beyond equilibrium... | https://physics.stackexchange.com |
1,603,991 | [
"https://math.stackexchange.com/questions/1603991",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/23139/"
] | This is problem 5.44 in Rotman's "An Introduction to the Theory of Groups", 3rd edition.
<blockquote>
If $G$ is nilpotent of class $2$ and $a \in G$, then the function $[a,\,\,\,]:G \to G$ defined by $b \mapsto [a,b]=aba^{-1}b^{-1}$ is a homomorphism.
</blockquote>
What we want to show is that for a fixed $a \in G$... | $[a,xy]=a.xy.a^{-1}.(xy)^{-1}=a.xy.a^{-1}.y^{-1}x^{-1}$. In middle of the last word, there is term $ya^{-1}y^{-1}$, so before $y$ if we insert $a$, we get a commutator and since $G$ is class $2$, commutator is in center, hence it can be moved anywhere in product; so
$$[a,xy]=a.xy.a^{-1}.y^{-1}x^{-1}=a.x.a^{-1}\underb... | You should use commutator identity;
$$[x,zy]=[x,y]\cdot [x,z]^{y}$$
As $G/Z(G)$ is abelian $G'\leq Z(G)$ hence $[x,z]\in Z(G)$. Thus, $[x,z]^y= [x,z]$.
As a result $$[x,zy]=[x,y]\cdot [x,z]$$
| https://math.stackexchange.com |
543,271 | [
"https://physics.stackexchange.com/questions/543271",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/248372/"
] | I know what anti-ferromagnetism is. But in a paper I came across "short-range antiferromagnetic order". Can someone please explain to me what it is or suggest me the book/(or any material).
| Provided that the first two equations hold true at the initial condition, they are redundant for the time evolution, because
<span class="math-container">$$\nabla \cdot \frac{\partial \mathbf{E}}{\partial t} = \frac{1}{c^2} \nabla \cdot \nabla \times \mathbf{B} = 0$$</span>
and hence <span class="math-container">$\nabl... | Maxwell equations are <em>partial differential equations</em>, so much of the intuition that one have from dealing with the systems of linear equations or the ordinary differential equations is not applicable here.
More specifically: the solution of the divergence equations are defined up to a curl, i.e.
<span class... | https://physics.stackexchange.com |
455,571 | [
"https://electronics.stackexchange.com/questions/455571",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/52563/"
] | P = sqrt(3)*U * I * cos(f) is the real power for a symmetric load (U and I are RMS values of voltage and current of a single load), but what about generators?Do they have to have equal electromotive forces too?
| Don't know if this will help as your question is still very vague to me, but you can let me know.
Remember the general power equation measured in Watts, (P= voltage x current), where the total power P is a product of the voltage and the current. This can be applied to find the power PRODUCED by a voltage source e.g. a... | Neither loads nor generators "have to have" symmetric or equal electromotive forces, but it is desirable for economic utilization of equipment for the loads and sources to be symmetric. It is also less complicated to calculate power is everything is symmetric. The formula cited in the question applies only to balanced ... | https://electronics.stackexchange.com |
560,655 | [
"https://physics.stackexchange.com/questions/560655",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/140404/"
] | If I consider the last equation of Maxwell,
<span class="math-container">$$\oint_\gamma \mathbf{B}\cdot d\boldsymbol{\ell}=\mu_0\left(I_C+\epsilon_0\frac{d\Phi(\mathbf{E})}{dt}\right) \tag 1$$</span>
where <span class="math-container">$I_C$</span> indicates the conduction current generated by a potential difference, an... | The other questions you asked were inspired by an animated movie. A lot of what you see there is not explainable by physics - Many of the things you see just couldn't happen that way. So specific calculations might not be as useful as understanding some ideas. And you have extracted a reasonable physics question from i... | The punch <strong>itself</strong> doesn't collide and is as such not an object indeed. A punch has no mass and no velocity. It's a short force delivered by some object to another object (and vice-versa), so it <strong>is</strong> something physical.<br />
This force has the value of <span class="math-container">$F=\fra... | https://physics.stackexchange.com |
157,710 | [
"https://electronics.stackexchange.com/questions/157710",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/68949/"
] | I read how MOSFETs work, although there is this thing I can't understand. To make things simpler let's take only n-channel MOSFETs into account. Normally, the load is connected on the drain side, like this:
<img src="https://i.stack.imgur.com/z6QZC.png" alt="Drain side load">
When \$V_{GS}\$ is above \$V_{thres}\$ an... | The difference between the gate voltage and the channel voltage needs to be above the threshold voltage for the MOSFET to conduct well. If the load is between the mosfet and ground, then the more current you push through the mosfet, the more voltage drops over the load and the less gate-source voltage there is.
In the ... | The reason you are seeing the effect is as follows:
When you put the load between the source and GND then when the N-FET starts to turn on there is voltage drop across the load. This voltage drop is due to the current through the load and the resistance of the load. This voltage drop effectively pushes the source term... | https://electronics.stackexchange.com |
218,265 | [
"https://softwareengineering.stackexchange.com/questions/218265",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/89095/"
] | A colleague of mine came up with a rule-of-thumb for choosing between creating a base class or an interface.
He says:
<blockquote>
Imagine every new method that you are about to implement. For each of them, consider this: <strong>will this method be implemented by more than one class in <em>exactly</em> this form, with... | I don't think that this is a good rule of thumb. If you are concerned about code reuse, you can implement a <code>PetEatingBehavior</code> which role is to define the eating functions for cats and dogs. Then you can have <code>IEat</code> and code reuse together.
These days I see less and less reasons to use inheritan... | <blockquote>
Is it worth following this rule-of-thumb?
</blockquote>
It is a decent rule of thumb, but I know of quite a few places where I violate it.
To be fair, I use (abstract) base classes a lot more than my peers. I do this as defensive programming.
To me (in many languages), an abstract base class adds th... | https://softwareengineering.stackexchange.com |
86,192 | [
"https://mechanics.stackexchange.com/questions/86192",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/69011/"
] | My largest car maintenance cost is exhaust pipes, mostly catalytic converters. I do not think this is the case for most people. What am I doing wrong?
I tend to buy cheap cars (<£500), change the oil myself, get the brakes changed when they squeak and change the car if there are any repairs that cost more than the... | Another cause of rapid exhaust system rusting is driving patterns which don't warm up the vehicle thoroughly. In this case, a "thorough" warmup means the entire exhaust is hot enough to cause all moisture within to evaporate. Depending upon the vehicle, this might take 10 miles of driving, the sort of distanc... | 3 in 4 years?
That sounds like the engine mounts were loose or broken and putting undue strain on the pipe.
Another possibility is hitting the exhaust on sleeping policemen - are the roads in good condition - lots of potholes etc can also cause flexing damage.
Making sure all the mounting points and rubbers are in good... | https://mechanics.stackexchange.com |
471,090 | [
"https://stats.stackexchange.com/questions/471090",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/287831/"
] | <span class="math-container">$X_1$</span> and <span class="math-container">$X_2$</span>, one accurate than the other, are subject to the standard deviations, <span class="math-container">$\sigma$</span> and 1.25<span class="math-container">$\sigma$</span>
respectively. <span class="math-container">$X_1$</span> occurred... | To see if an estimator, <span class="math-container">$\hat{\theta}$</span> is unbiased for <span class="math-container">$\theta$</span> you need to calculate the bias:
<span class="math-container">$$b = bias(\theta) = E(\hat{\theta}) - \theta $$</span>
If <span class="math-container">$b=0$</span> then the estimator i... | <span class="math-container">$$
E \bar{x}_1 = E[\frac{1}{6}\sum X_1^j] =
\frac{1}{6} 6 E[X_1] = E[X_1],
$$</span>
and in the same way,
<span class="math-container">$$
E \bar{X}_2 = E[\frac{1}{10}\sum X^j_2] =
\frac{1}{10} 10 E[X_2] = E[X_2].
$$</span>
Since the expectation of the estimators are equal to the expected... | https://stats.stackexchange.com |
239,432 | [
"https://security.stackexchange.com/questions/239432",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/227162/"
] | You have a <code>User</code> table:
<pre><code>UserID (auto-incrementing Integer)
Password hash
LastLogin
</code></pre>
All related tables are linked by the UserID.
You also have a <code>Username</code> table:
<pre><code>Username
Salt
IncorrectLoginCount
LockedUntil
etc.
</code></pre>
A user creates an account. You tak... | Before getting into the analysis of the process to slow down cracking the hashes, I want to address something far more important first:
If I log in, and my hash happens to match some other user, I will get authenticated to that user. So your whole "look in the Users database to blindly find <em>any</em> match beca... | After some thinking, I will suggest that there is no significant security improvement.
Let's put the standard account protection: salting the password with a time-consuming algorithm (bcrypt, and so one). What a attacker can do :
<ul>
<li>Reverse the hash: almost impossible</li>
<li>Bruteforce the hash: almost impossib... | https://security.stackexchange.com |
172,400 | [
"https://electronics.stackexchange.com/questions/172400",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/77295/"
] | I know this is a very stupid question.
Lm35 has 3 pins: Vcc, Analog output voltage, Gnd.
Is it ok to measure between analog output voltage and gnd? Im asking because Vcc and Gnd is a dc.
| That's how the IC works: it outputs an analog voltage proportional to the temperature in °C. Output is 10 mV/°C, so at 20 °C you'll get 200 mV.
Connect one pin of your voltmeter (analog or digital, doesn't matter) to the output, and the other to the ground pin, because that's the reference against which you want to me... | Yes you definitely can because the analog pin is set by the IC with respect to ground.
You probably know this but if you are going to use a voltmeter, don't touch the leads of the LM35 with the voltmeter probes directly, because if you short it, you will experience the all too familiar smell of burning electronics.
| https://electronics.stackexchange.com |
386,737 | [
"https://mathoverflow.net/questions/386737",
"https://mathoverflow.net",
"https://mathoverflow.net/users/143361/"
] | Please can someone help me? I have tried to find the Laplace transform of the form:
<span class="math-container">$$\int_{0}^{+\infty} (v+1)^{\nu}(2v+1)^{k}v^{\alpha} \exp(-pv), \mbox{ where }\alpha,\nu, k \mbox{ are integers }$$</span>
I have searched on the two Books "Erdelyi. <em>Tables of integral transforms</e... | <span class="math-container">$$
\ln\frac{(a+1)^2}{4a}\ln\frac{(b+1)^2}{4b}
=\ln\left(1-\left(\frac{a-1}{a+1}\right)^2\right)\ln\left(1-\left(\frac{b-1}{b+1}\right)^2\right)\\=
\left(\sum_{n=1}^\infty\frac1n \left(\frac{a-1}{a+1}\right)^{2n}\right)\times
\left(\sum_{n=1}^\infty\frac1n \left(\frac{b-1}{b+1}\right)^{2n}\... | <em>Remarks</em>: @Fedor Petrov's proof is very nice. Here we give an alternative proof.
<hr>
Using the identity
<span class="math-container">$$\ln (1 + u) = \int_0^1 \frac{u}{1 + ut}\, \mathrm{d} t,$$</span>
the desired inequality is written as
<span class="math-container">$$\int_0^1 \frac{(1 - a)^2}{t(1 - a)^2 + 4a}\... | https://mathoverflow.net |
16,352 | [
"https://electronics.stackexchange.com/questions/16352",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/1950/"
] | I have two PIC18F4620 connected via SPI + Slave Select + additional IRQ line. Both controllers are driven from the same crystal oscillator using the same clock settings. The master sends one byte and then waits until the slave toggles that additional IRQ line. The duration of the toggling is 4 instruction cycles. All t... | The actual reason was me being a moron. My <code>DisableInterrupts</code> macro did <code>INTCONbits.GIE=1</code>.
I found this by toggling a pin during busy waiting:
<pre><code>while(!PORTBbits.RB1)
{
LATBbits.LATB0 = 0;
LATBbits.LATB0 = 1;
}
</code></pre>
I noticed that the toggling stopped in regular inte... | The last instruction it's an unconditional branch, right? Usually branches and memory accesses (made on the first instruction, right?) take about 2-3x more time to execute, so in you're case those instructions could take about 16 cycles to execute, which is 400ns (on the best case scenario).
| https://electronics.stackexchange.com |
4,104,160 | [
"https://math.stackexchange.com/questions/4104160",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/777827/"
] | I know the elements of <span class="math-container">$\frac{R}{J}$</span> are like <span class="math-container">$r+J$</span> when <span class="math-container">$r \in R$</span>. So I have to show that there is some <span class="math-container">$s \in R$</span> that <span class="math-container">$r+J = s+I$</span>. But I d... | In general is not true that for every <span class="math-container">$r$</span> there is <span class="math-container">$s$</span> such that <span class="math-container">$$r+J=s+I$$</span> for example, take <span class="math-container">$r\in J$</span>, then the equation became <span class="math-container">$J=s+I$</span>, w... | First, on a the level of equality what you are asking for isn't generally going to happen. To see why, let's look at an example. Let <span class="math-container">$R= \mathbb Z$</span>, <span class="math-container">$I = 4\mathbb Z$</span>, and <span class="math-container">$J = 2\mathbb Z$</span>. Let's look at <span cla... | https://math.stackexchange.com |
440,475 | [
"https://softwareengineering.stackexchange.com/questions/440475",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/419284/"
] | Does "primitive obsession" as a poor design practice apply to development in Python? I have seen a lot of examples and discussion in the context of statically typed languages (like Java, C#), but there are also dynamically typed languages like Python. Do solutions to primitive obsession look different in Pyth... | The simple answer here is 'yes': primitive obsession is still an issue in dynamically typed languages. The longer answer is that the issue is somewhat different in a dynamically typed language than a statically-typed one. I'm going to use Python as an example.
So the first bit of nuance is that in Python and similar ... | Primitive obsession is about failing to design a dedicated type that would abstract a concept and instead trying to force an existing type into the role. If the language in question has customizable types then the smell applies.
The whole static vs dynamic thing is just about where you declare the type. Has nothing to... | https://softwareengineering.stackexchange.com |
73,626 | [
"https://dba.stackexchange.com/questions/73626",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/42188/"
] | I gotta problem with connecting Jira 6 to Pgpool-II which is responsible for load balancing and replication in Postgresql bases(2 instances).
<img src="https://i.stack.imgur.com/5bqdA.png" alt="enter image description here">
Pgpool is started on port 9999, I just want to connect to it in this (Jira)installation step... | I have three suggestions
<h1>SUGGESTION #1 : Rewrite the query</h1>
You should rewrite the query as follows
<pre><code>SELECT http,
COUNT( http ) AS count
FROM reqs
WHERE date >= ( DATE(NOW() - INTERVAL 1 DAY) + INTERVAL 0 SECOND )
GROUP BY http
ORDER BY count;
</code></pre>
or
<pre><code>SELECT * FROM
(
SELEC... | Change your date column type to an integer. Store the date as a Unix date in integer. Timestamp Is a lot larger than an int. You'd get some bang out of that.
| https://dba.stackexchange.com |
261,496 | [
"https://electronics.stackexchange.com/questions/261496",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/114174/"
] | I'm working on a project based on NXP accelerometer MMA8653.
This is a I2C, 3-axial accelerometer with 10-bit resolution.
Actually I can read the accelerometer registers and I'm able to configure it.
I configured the accelerometer with full scale equal to 2G and the sensitivity associated to this full scale is 256 co... | As far as I understand, you will get the acceleration in [g] on each axis by dividing each of the 3 values you obtained by 256 (because your sensitivity is 256 counts/g).
To avoid any problems with the division of integer numbers, I suggest you to do in this order, for each value:
<ul>
<li>Convert the number into a s... | You can usually figure out conversions like these by examining the units. If you divide the ADC reading with units of <em>counts</em> by the sensitivity with units of <em>counts/g</em> then the units of <em>counts</em> in the numerator and denominator of the division will cancel each other out leaving you with <em>g</... | https://electronics.stackexchange.com |
39,037 | [
"https://mathoverflow.net/questions/39037",
"https://mathoverflow.net",
"https://mathoverflow.net/users/8994/"
] | Hey guys,
I have a slightly imprecise question. I would like say something about a whole set of binary strings evaluated by a binary function by just looking at some type of average. The easiest example I can think of is probably a binary function $f: \{0,1\}^n \rightarrow \{0,1\}$ that is linear with $f(0) = 0$. Now ... | Assuming that your sums run over the nonnegative integers,
$$\sum_{n \ge 0} n!^s$$
is convergent if and only if $s < 0$. (Apply the ratio test.)
It's easy to evaluate both sides at $s = -1$. In that case, the left-hand side is just
$$ \sum_{n \ge 0} {1 \over n!} = e$$
and the left-hand side is $1 + 2 \sinh 1$... | write $A(s)=\sum_{n} n!^s$ and $B(s)=1+2\sum_n (2n+1)!^s$. Numerically we get
$$
\lim_{s\to-\infty}\frac{A(s)}{B(s)} = \frac{2}{3}
$$
another evidence that they are not identically equal...
Other numerical evidence suggests:
$$
\lim_{s\to-\infty} B(s)-A(s) = 1;\qquad
\lim_{s\to0-} B(s)-A(s) = \frac{1}{2}.
$$
| https://mathoverflow.net |
2,451,455 | [
"https://math.stackexchange.com/questions/2451455",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/464054/"
] | Prove that $\frac{a}{b+c} +\frac{b}{c+a}+\frac{c}{a+b} \ge \frac{3}{2}$
My steps
A= $\frac{a}{b+c}$,B= $\frac{b}{c+a}$ &C=$\frac{c}{a+b}$
A.M$\ge$H.M
$\frac{A+B+C}{3} \ge \frac{3ABC}{AB+BC+AC}$
I am struck after this step
${A+B+C} \ge \frac{9}{\frac{a}{c}+\frac{c}{a}+\frac{b}{a}+\frac{a}{b}+\frac{c}{b}+\frac{b... | To write the equation of a plane you need a normal vector $\vec n=(a,b,c)$ and a point
The equation is $ax+by+cz+d=0$
A normal vector is surely the cross product of $\vec n=\vec u\times \vec v=(3, -5, -5)$
The plane has equation $3x-5y-5z+d=0$
Knowing that it passes through $R(0,1,-1)$ we plug the coordinates and ... | The problem is worded somewhat oddly, but I interpret it as asking for the plane through $R$ parallel to $\vec u$ and $\vec v$.
An approach to these sorts of problems that’s somewhat similar to the way you’ve started is to work in homogeneous coordinates (i.e., use projective geometry). The homogeneous equation of a ... | https://math.stackexchange.com |
2,455,117 | [
"https://math.stackexchange.com/questions/2455117",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/487008/"
] | I was trapped by this question at least for two hours. I negated the definition of limit first, and then try to prove $$\lim_{x \to 0}\cos\left(\frac1x\right)$$ not exist.
| Have you looked at the graph of this function? If you have, it should be intuitively obvious that no limit exists: the function oscillates wildly as $x \rightarrow 0$, approaching no single limit. It's not immediately clear how this helps you prove it though.
A handy tool to have is sequential continuity: if $f$ is co... | Assume the limit is some number $L$, and derive a contradiction. If the limit exists, then for all $\epsilon > 0$, there exists a $\delta > 0$ such that $|\cos(1/x) - L| \leq \epsilon$ for all $x$ satisfying $ 0 < |x| < \delta$. In particular, there exists some $\delta$ for $\epsilon = 1/2$.
Now, let $n$ b... | https://math.stackexchange.com |
2,357,395 | [
"https://math.stackexchange.com/questions/2357395",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/-1/"
] | I am trying to find the coefficient of $x^{n}$ where $n \in[0, \infty)$ in the expansion
$(x^0 + x^1 + x^2 + x^3 + x^4 + x^5 ... +x^{\infty}$)$^{t}$, where $t$ is an integer.
I haven't been able to distinguish a pattern between the coefficients and the value of $t$, but the sum $\sum_{i = 0}^{\infty} x^i$ is the Tay... | Assuming $|x| < 1$ use GP sum and the expression reduces to,
$$(1-x)^{-t}$$
Coefficient of $x^n$ in $(1-x)^{-t}$ equals $\binom{n+t-1}{t-1} = \binom{n+t-1}{n}$.
Check out the binomial expansion of $(1+x)^m$ when $m$ is negative.
| $\left(x^0 + x^1 + x^2 + x^3 + x^4 + x^5 ... +x^{\infty}\right)^t=\dfrac{1}{(1-x)^t}=(1-x)^{-t}$
The binomial expansion gives
$$(1-x)^{-t}=\sum _{n=0}^{\infty } (-1)^n x^n \binom{-t}{n}$$
For $t=10$ for instance we have
$$\left(x^0 + x^1 + x^2 + x^3 + x^4 + x^5 ... +x^{\infty}\right)^{10}=1 + 10 x + 55 x^2 + 220 x^3 +... | https://math.stackexchange.com |
56,415 | [
"https://cs.stackexchange.com/questions/56415",
"https://cs.stackexchange.com",
"https://cs.stackexchange.com/users/1152/"
] | I've defined the identity function in <code>Agda</code> as follows:
<pre><code>idd : (∀ {ℓ} {A: Set ℓ}) → A → A
idd a = a
</code></pre>
I want to ask you if the following reasonings are correct:
<ul>
<li>The type of this function is <code>A -> A</code>.</li>
<li><code>idd</code> is a polymorphic function, where ... | Your code does not work. I would suggest that you forget about the universe levels for the time being (the $\ell$ thing) and focus on simpler things first. Here is working code:
<pre><code>idd : (A : Set) → A → A
idd A a = a
</code></pre>
The type of <code>idd</code> is <code>(A : Set) → A → A</code>. It is a depende... | I'll use the following code for answer your questions:
<pre><code>idd : (A : Set) → A → A
idd A a = a
</code></pre>
Is <code>idd</code> a polymorphic function? No. Agda (without universe polymorphism) is a monomorphic language. The <code>idd</code> function is only defined on small types, i.e. <code>Set</code>. The f... | https://cs.stackexchange.com |
301,868 | [
"https://mathoverflow.net/questions/301868",
"https://mathoverflow.net",
"https://mathoverflow.net/users/102390/"
] | The Brown-Comenetz dualizing spectrum $I_{\mathbf{Q/Z}}$ is not detected by very many spectra: it is $BP, \mathbf{Z}, \mathbf{F}_2, X(n)$ for $n\geq 2$, and even $I_{\mathbf{Q/Z}}$-acyclic. However, if $X$ is any nontrivial finite spectrum, then $X\wedge I_{\mathbf{Q/Z}}$ is not contractible. This motivates a natural q... | Your question appears to be equivalent to the 'dichotomy conjecture' of Hovey, which I believe is still open.
First, note that any finite spectrum has a type, and all finite spectrum of type $n$ have the same Bousfield class, usually denoted $F(n)$. In Hovey and Strickland's memoir (Appendix B) they conjecture that ... | I don't think that the answer is known. However, here are some comments. I will work everywhere with $p$-local spectra, for some fixed prime $p$, and write $I$ for the $p$-local Brown-Comenetz spectrum, so that $[W,I]=\text{Hom}(\pi_0(W),\mathbb{Q}/\mathbb{Z}_{(p)})$.
I first claim that $I\wedge W=0$ iff $[W,S_p]_*=... | https://mathoverflow.net |
338,735 | [
"https://softwareengineering.stackexchange.com/questions/338735",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/257611/"
] | So this is all hypothetical and theoretical really. This isn't a real system I'd have to architect, but its a good question.
A company stores and reproduces contracts. Contracts can have many documents associated with them. There are up to 200 types of these documents that can be assigned to any single contract.
T... | As Niklas H wrote in a comment while I was typing this:
You have one table for contracts.
Then you have a table for documents including a foreign key to the contracts tables for the contract the document belongs to.
You then have a document type table where your document types are. From your document table you have ... | One could just store the document itself in the database and not bother with any other tables around types etc. Most popular document systems have properties and meta data associated with it, so use that instead of a predefined system of tables.
You question is kind of broad, but let's assume that all the documents w... | https://softwareengineering.stackexchange.com |
609,485 | [
"https://physics.stackexchange.com/questions/609485",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/283157/"
] | Why does a flowing fluid in a venturimeter rise in the vertical tubes? Why does it need to rise anyway?
| When the air speeds up in flowing through the throat of the venturi, it pulls a partial vacuum on the walls of the venturi and a tube leading off the throat will therefore experience a suction pressure. That pressure is less than that of the surrounding atmosphere, and if there is fluid inside the tube, that pressure d... | Multiple venturi tubes are commonly used for adjusting multiple carburetors on an engine so they will all have the same air flow rate at idle. The engine pulls a partial vacuum on its side of a venturi that is limiting its air flow. A partial vacuum on one end of a tube with the other in water open to atmospheric press... | https://physics.stackexchange.com |
370,315 | [
"https://softwareengineering.stackexchange.com/questions/370315",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/162307/"
] | What are the cons and the pro for handling CORS in infrastructure or application ?
I mean is it better to setup CORS on my nginx/apache/tomcat ?
or to handle it by coding in my application ?
I have three API REST running with their own language (java spring, express and php) behind a nginx reverse proxy. I have acces... | I don't think there is a general answer to this question.
If you have a web api that should offer differing subsets of functions to differing clients then you may wish to use CORS coupled with authorisation configuration information to implement this. This may especially be the case if for some reason you do not full... | Complementing the answer from @sentinel, seems that there isn't a wide-convention for placing the CORS headers.
I'd say that:
I'd place the logic in <strong>the server</strong> if:
<ul>
<li>The infra relies on a different team within the company and I prefer not to delegate it.</li>
<li>I need to build dynamic white... | https://softwareengineering.stackexchange.com |
739,265 | [
"https://physics.stackexchange.com/questions/739265",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/327258/"
] | So I wanted to derive the total energy for an elliptical orbit, <span class="math-container">$E = -GmM/2a,$</span> and while I was doing it, I ran into this hurdle. So at the closest point to the focus, the orbiting object is at a distance of <span class="math-container">$a(1-e)$</span> from the focus, where a is the s... | The expression you use for centripetal force, <span class="math-container">$F = mv^2/r,$</span> is only valid for circular orbits. For a planet in an elliptical orbit at its closest approach to the star it is orbiting, it will have a higher speed than that given by equating the centripetal and gravitational force. The ... | Using the nearest and farthest points in the orbit, you can find the total energy(kinetic plus potential) at each point and they must be equal, giving you one equation for the two velocities. You can then equate the angular momentum at each point giving you a second equation for the velocities. Solve the two equation... | https://physics.stackexchange.com |
487,803 | [
"https://physics.stackexchange.com/questions/487803",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/235013/"
] | I found that capillary tubes in refrigeration system are tubes with very small diameter and very long length. Pressure drops down suddenly due to very small diameter of the capillary and length. The smaller the diameter and longer the length of the capillary, more the drop in pressure.
I am not from mechanical stream,... | Just as a film of oil changes friction, so does a layer of adsorbed gas from the atmosphere. No surface is really clean, until such material is driven off of the surface, usually by a vacuum bake cycle. At least, afterward the surface is
cleaner, if not absolutely clean.
If surface composition is important, one c... | With all respect to Feynman, I think he has got confused here. He seems to be <em>assuming</em> that there <em>ought</em> to be an "exact" law of friction like <span class="math-container">$F = \mu N$</span> and then complaining that you can't do an experiment that actually produces that result, however hard you try to... | https://physics.stackexchange.com |
2,147,278 | [
"https://math.stackexchange.com/questions/2147278",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/410481/"
] | I'm doing a problem involving combinations as follows:
Consider a house with $n$ room-mates. Each weekend, one or more of the room-mates form a group to drive to a party. Of the group, one is the designated driver. How many ways can this be done? Do the calculation two ways:
The two ways are
<ol>
<li>where you... | For the first case you have done it correctly that is $\binom{n}{1} \times \binom{n-1}{k-1}$ ways.
For the next you have $\binom{n}{k}$ ways to form a group and then choose a driver amng them in $k$ ways. So the total ways is $k \times \binom{n}{k}$.
Now see that $$\binom{n}{1} \times \binom{n-1}{k-1} = n \times \fra... | For #1. First we pick the designated driver. There are ${n \choose 1}=n$ ways to do this. Then from the remaining $n-1$ roommates, we want to find all subgroups that are in the group. There are $2^{n-1}$ to do this. Therefore, the total number of ways to form this group is $n2^{n-1}$.
For #2. We first pick the groups ... | https://math.stackexchange.com |
250,203 | [
"https://softwareengineering.stackexchange.com/questions/250203",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/142904/"
] | <strong>Background</strong>
I've run across this problem as I am currently an intern at a large company's local software division. I have been given the task of extending a project that several previous interns have worked on (not collectively but sequentially). The project is written in C# and is a relatively simple ... | There are two things of note here: you seem to know quite a bit about good practices and the project is meant to disappear "soon" (though not right after you leave).
As Telastyn mentions, make the most out of this experience to learn what works and what doesn't and how to apply best practices in a real-world environme... | The point of an internship is to learn. I would refactor the code to be better and ignore the assumed limitations of people you don't know. For all you know, the company will move that project to an internal team rather than interns soon.
| https://softwareengineering.stackexchange.com |
418,242 | [
"https://softwareengineering.stackexchange.com/questions/418242",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/365689/"
] | I'm writing a small utility class to create an abstraction for addEventListener (JavaScript/DOM)
Let's say I have to test for these features:
<ol>
<li>Single event target with a single event</li>
<li>Multiple events</li>
<li>Multiple event targets</li>
<li>Delegated events</li>
<li>Once</li>
</ol>
Now if I understand u... | To decide what makes most sense, it can be helpful to know about the inner code structure, and which coverage your tests will create (code and branch coverage).
<ul>
<li>If there are features which are completely independent of others, and their code is fully decoupled from each other, their is no need to write tests w... | It depends
There is no strict rule, so choose what suits you best.
<ol>
<li>In doubt, test : If the effort is not that big and reassure you then go for it and add the combinated test</li>
<li>Rely on End to End tests : If each case is well tested independently, and the combination should work (e.g. by design) you can r... | https://softwareengineering.stackexchange.com |
239,728 | [
"https://security.stackexchange.com/questions/239728",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/244356/"
] | I do know the difference between brute force attack and DOS.
What if a web server doesn't have account lock out in place and a few brute force attacks is being started in parallel, and these attacks will keep web server CPU intensively busy. Will these attacks in the end reduce the abilities of web server to serve othe... | <h1>YES INDEED</h1>
I used to own a shared hosting business and, while being at a party on a weekend night, I received an automated monitoring notification triggered by a resource exhaustion. I immediately left to the office and when I arrived I found out a bruteforce attack against a client's WordPress admin panel was... | Yes. If the server cannot keep up with repeated failed login attempts, it will result in a loss of service... aka a DoS if the requests are from ones source, a DDoS if the attack comes from multiple sources.
| https://security.stackexchange.com |
25,229 | [
"https://mathoverflow.net/questions/25229",
"https://mathoverflow.net",
"https://mathoverflow.net/users/6031/"
] | For example, I take differentiability, analyticity, and algebraicity(of a function).
All(more or less) imply continuity. So when we define a differentiable function on $\mathbb R^n$ or an analytic function on $\mathbb C^n$, or a regular map on an affine space, we do not explicitly require that the functions are continu... | As Andrea hints, if you start with sheaves then you need continuity to even begin talking about morphisms of sheaves.
However, if you're interesting in just defining, say, a smooth map between manifolds then you can simply write "$f \colon M \to N$ is smooth if, whenever $c \colon \mathbb{R} \to M$ is a smooth curve t... | Let $M,N$ two manifolds and $f : M \to N$ a (set-theoretic) map. Then there are (at least) two definitions for $f$ to be smooth:
(1) For every ball $B \subseteq N$ the preimage $f^{-1}(B)$ can be covered with balls $C \subseteq M$ such that the induced maps $C \to B$ are smooth.
(2) $f$ is continuous and for every ba... | https://mathoverflow.net |
493,131 | [
"https://math.stackexchange.com/questions/493131",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/91732/"
] | Let $X$ be a projective scheme, $X_1, X_2$ be closed subschemes of $X$. Let $f:X \to S$ be a flat morphism for some scheme $S$. Denote by $i_1$ and $i_2$ the natural inclusion maps from $X_1$ and $X_2$, respectively to $X$. Assume that the composition maps $f \circ i_1$ and $f \circ i_2$ are flat. Is it then true that ... | No, the fiber product is not always flat over $S$:
Let $k$ be a field of characteristic $\neq 2$ and take for $f$ the first projection $f:X=\mathbb A^2_k=\operatorname {Spec}k[x,y]\to S=\mathbb A^1_k=\operatorname {Spec} k[x]$, for $i_1$ the closed immersion of $X_1=V(x-y^2)$ into $X$ and for $i_2$ the closed imme... | In the spirit of Georges's philosophy of recording useful (counter)examples, let me offer another:
Consider the projection $X = \mathbb A^2 \to S = \mathbb A^1$ given by $(x,y) \mapsto x$.
Now let $X_1$ be the line $y = 0$ and $X_2$ be the line $x + y = 0$. Both map
isomorphically to $\mathbb A^1$ (and an isomorphi... | https://math.stackexchange.com |
709,582 | [
"https://physics.stackexchange.com/questions/709582",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/335973/"
] | Suppose we want to send a spaceship to Alpha Centauri and calculate the minimum possible time it will take for us here on Earth to have the spaceship back. We <em>are not</em> interested in how fast the time will pass for the people in the spaceship, but rather how long it will take for us here on Earth to have the spa... | <blockquote>
As the spaceship accelarates, at which point the time dilation added due to the incrase of speed starts to increase the total time of the journey measured on Earth?
</blockquote>
Never. If the ship can accelerate, it will reduce the time measured on earth. There are diminishing returns, but it is never ... | The minimum time, as measured on Earth, for anything to travel to Alpha Centauri and back is 8.74 years or thereabouts, if the something was massless. For something massive like a spaceship the time would be greater, and would depend on the mass of the object, upon how much energy you were prepared to expend in acceler... | https://physics.stackexchange.com |
1,211,690 | [
"https://math.stackexchange.com/questions/1211690",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/117251/"
] | Suppose a and b are vectors such that $a \times b = 2i + j - k$ and
$a+b= i - j + k$. The least value of magnitude of vector $a$ is ?
Here $i$, $j$ and $k$ are unit vectors in direction of $x$, $y$ and $z$ axes and $\times$ symbolizes cross product.
Any help would be appreciated.
| Let $x,y$ be two random numbers, each is either $0$ or $1$.<br>
Let $A_1$ be the event $x=1$, $A_2$ is the event $y=1$ and $B$ the event $x+y$ is even. $B$ is independent of both $A_1$ and $A_2$ but not their union.
| If the $A_k$ are mutually disjoint, then "yes", because in that case
$$P(B\cap(\cup A_k)) = P(\cup (B \cap A_k)) = \sum P(B \cap A_k) = \sum P(B)P(A_k) = P(B) P(\cup A_k)$$
and hence $B$ and $\cup A_k$ are mutually independent.
(Others have posted counterexamples in the non-disjoint case.)
| https://math.stackexchange.com |
228,085 | [
"https://softwareengineering.stackexchange.com/questions/228085",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/73675/"
] | Is it ever justifiable to write production-code without also writing tests for it when doing Test Driven Development?
| Strict TDD? Absolutely not. How can you write a test, make it fail, make it pass, without writing a test?
In the real world, very few people do strict TDD. It's an ideal that shouldn't be allowed to get in the way of common sense. Every rule has a scenario where it's justifiable to break it, and that's fine. But we sh... | Depending on your definition of "also writing tests", it may be acceptable :
<ul>
<li>At the Refactor step. Refactoring doesn't require writing new tests (but does imply a test suite already in place)</li>
<li>When you make adjustments in purely cosmetic UI code or other non directly testable code. </li>
<li>Also, I w... | https://softwareengineering.stackexchange.com |
8,946 | [
"https://datascience.stackexchange.com/questions/8946",
"https://datascience.stackexchange.com",
"https://datascience.stackexchange.com/users/13578/"
] | In my machine learning class these two methods were discussed and mentioned that both should be used. I have a couple questions about this:
1) Can I mix and match these two approaches? e.g. Feature Scale x1 and Mean Normalize x2?
2) How do you determine which of these options to apply? It seems that either could acco... | I agree with the existing answer that <em>feature scaling</em> is a superset into which techniques like mean normalization, residual normalization, etc falls under.
So, assuming that by <em>feature scaling</em>, you mean the techniques other than mean normalization, I would attempt to answer your questions:
<blockquo... | Mean normalization is a form of feature scaling, so these are not really two different approaches. Feature scaling is just a more general term. What kind of feature scaling, e.g. mean normalization, you need to use ultimately depends on the data.
| https://datascience.stackexchange.com |
3,648 | [
"https://mechanics.stackexchange.com/questions/3648",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/1100/"
] | I have a 1.3L Skoda Felicia, (carburetter engine without catalytic nor other gimmicks). Since past 1-2 months I would hear the exhaust sound has changed, it became more and more audible and at full throttle it sounded like a spitting with your tongue between lips (kind of like buzzing?). Recently, in past several days ... | You can block one end while engine running and see if you can detect smoke coming out somewhere in the pipe/box (remember that the exhaust gets hot and if blocked for too long the engine will stop).
Other way is to visually inspect each element and see if they are fitted correctly, you should look for parts that can b... | Raise the vehicle on to jack stands or drive on ramps. With the engine running have a friend hold a rag over the tailpipe. Crawl under the vehicle. Move your hands around the exhaust system while listening and feeling for the leak. Be careful how close you get your hands to the exhaust system as it will get hot. If no ... | https://mechanics.stackexchange.com |
43,131 | [
"https://stats.stackexchange.com/questions/43131",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/16649/"
] | I have a question about the parameter optimization when I use the 10-fold cross validation.
I want to ask that whether the parameters should fix or not during every fold's model training , i.e. (1) select one set of optimized parameters for every fold's average accuracy.
or
(2) I should find the optimized parameter ... | Let us firstly distinguish between two sets of parameters: model parameters (e.g. weights for features in regression), and parameters to the learning algorithm (and hyperparameters). The purpose of cross-validation is to identify learning parameters that generalise well across the population samples we learn from in ea... | I think the currently accepted answer is incomplete in an unfortunate way. I do not agree with the sentence
<blockquote>
The purpose of cross-validation is to identify learning parameters
that generalise well across the population samples we learn from in
each fold.
</blockquote>
This is indeed one very import... | https://stats.stackexchange.com |
57,413 | [
"https://quant.stackexchange.com/questions/57413",
"https://quant.stackexchange.com",
"https://quant.stackexchange.com/users/46156/"
] | I am currently trying to calculate a volatility by using the EWMA model because it is said to yield better results than just using an equal weighted calculation approach. However I am a bit confused when it comes to using or choosing the lambda term.
According to various sources, in finance (especially risk management)... | The weights generated by EWMA do not have to sum to 1. Page 81 of the RiskMetrics 1996 document where EWMA was introduced shows an example with 22 observations, similar to yours, that uses the same value for lambda, and their weight series sums to 0.71.
Instead of worrying if this could underestimate the resulting vola... | In fact, you can use the historical data to estimate the lambda, see the paper at "https://www.sciencedirect.com/science/article/abs/pii/S0304407617301926".
| https://quant.stackexchange.com |
137,354 | [
"https://mathoverflow.net/questions/137354",
"https://mathoverflow.net",
"https://mathoverflow.net/users/4707/"
] | Suppose $A$ is an abelian variety, $X, Y$ are subvarieties of $A$ of complementary dimension,
<blockquote>
<blockquote>
Does every component of $X \cap Y$ contribute non-negatively to the intersection number?
</blockquote>
</blockquote>
| The following answer expands on my comment.
We use Fulton's definition of the intersection product. Consider the diagonal embedding $\Delta$ of $A$ in $A \times A$ (which is regular) and intersect this with $X \times Y$. Since $A$ is an abelian variety, the normal bundle $E$ of $\Delta$ is trivial. The normal cone $C... | Can't you always find a geometric point $T\in A$ such that the intersection of $X$ and the translation $Y+T$ is either empty or 0-dimensional? Since $X\cdot Y$ is numerically equivalent to $X\cdot(Y+T)$, that should give you the desired non-negativity, as per Damian's comment.
| https://mathoverflow.net |
163,742 | [
"https://dba.stackexchange.com/questions/163742",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/89015/"
] | I have created a login for an AD group:
<pre><code>CREATE LOGIN [MYDOMAIN\Development Admins] FROM WINDOWS WITH DEFAULT_DATABASE=[master]
</code></pre>
One of the members of that AD group is a user named DBGuy. I can see the DBGuy user in this AD group if I execute
<pre><code>xp_logininfo 'MYDOMAIN\Development Admi... | I noticed similar issue and I was locked out of SQL Server after install. So I started SQL Server 2014, in single user mode with -m option and logged into server SQL Management studio. I verified that AD group is correctly configured but didn't do any modifications. I logged out of the SQL server and tried again with a... | This is an old thread, but it was the first hit on Google when I encountered the same issue.
My two cents:
In my case it turned out that the AD group was a Distribution group, instead of a Security group, hence it could not be used to grant access to SQL Server.
| https://dba.stackexchange.com |
11,957 | [
"https://stats.stackexchange.com/questions/11957",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/1291/"
] | I have a dataset with 1500 patients with data on recurrence of a disease. Follow-up time varies between 1 and 15 years. Approx 10% have recurrence. What I´d like to do is create a predictive model for recurrence into n similar groups that share the same temporal recurrence risk. This so that I could advise on an optima... | <em>NOTE: this is not the easiest question to understand exactly what it is that you are after, just my take on what I think you mean. Hopefully it is close to what you are looking for, seeing as it is quite long</em>
This sounds like a straight-forward (in principle) application of decision theory. So you have your... | What kind of control are you talking about? Some kind of treatment that would move people between those n groups? Isn't it natural to start with additive effect (think mgcv:gam)? If the estimate of the effect turned out to be concave, you would have a ready candidate for a solution with its derivative.
| https://stats.stackexchange.com |
31,972 | [
"https://engineering.stackexchange.com/questions/31972",
"https://engineering.stackexchange.com",
"https://engineering.stackexchange.com/users/17181/"
] | The lower viscosity of water reduces friction. Besides, the water can transfer heat way better than oils. So why not use water as a lubricant in wind or hydro turbines, especially on equipment which is operating in the ocean ...
It seems to be a perfect material. It's the most abundant liquid on Earth, and it cause... | The whole point of lubrication is to keep the two surfaces almost apart.
Water has low viscosity in comparison to oil-based lubricants, which means that it forms a thinner film (electrohydrodynamic film thickness) between the two surfaces; the thinner the film, the greater the chance of direct physical contact between... | Sea water is about the worst thing in the world to put in a metallic mechanical device. As noted , corrosion would be horrendous ; dissimilar metals, stray currents , etc. Wind turbine gearing is an exceptionally demanding application ; EP ( extreme pressure ) lubes are needed with graphite and/or moly sulfide, etc. I ... | https://engineering.stackexchange.com |
274,558 | [
"https://physics.stackexchange.com/questions/274558",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/121464/"
] | I could be doing something quite stupid here; this is a tad over my head, so I apologize if this is a stupid question, and if requested to delete it, I will do so.
I know that Boltzmann's formulation of entropy is $S = k \log W$ where $k$ is Boltzmann's constant, $S$ is the entropy of the given system, and $W$ is the... | Both $S=k_B\ln W$ and $S=\ln W^{k_B}$ are mathematically equivalent and equally valid, so you're not wrong in shifting the constant $k_B$ into the logarithm. You can even express the microstates $W$ as a function of the entropy $S$ if you want, i.e.
\begin{align}W=e^{S/k_B}~,
\end{align}
as it is all the same.
Regardi... | The expression $W^k$, where $k$ is Boltzmann's constant, does not make sense mathematically because $k$ is not a number but has dimension of Energy/Temperature. So its numerical value depends on the units you choose. For example if you measure it in Joule/Kelvin then its value is about $1.38 \times 10^{-23}$ but if you... | https://physics.stackexchange.com |
100,615 | [
"https://softwareengineering.stackexchange.com/questions/100615",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/12063/"
] | Assuming:
<ul>
<li>The employee and company are parting on good terms</li>
<li>The new company is OK with a little contract work as long as it doesn't distract from the new job</li>
<li>The former company wants the help and the employee is willing to work a few hours a week</li>
</ul>
Is it a good idea to do contract... | Lots of people do this. We have two people that I know of doing it right now for our company. The key is to keep the work separate from the new job and make it clear you will be working on this only after hours and that you are not available for questions during hours when you are at your new job. Whatever you do, you ... | I've done this and not particularly well. Here's some tips from experience:
1) Don't go dark. HLGEMs answer of checking in every day is a great one. Also bill promptly or on a pre-established schedule. In many cases the trust you've established as an employee erodes quickly as a contractor, you want to be as tran... | https://softwareengineering.stackexchange.com |
8,701 | [
"https://chemistry.stackexchange.com/questions/8701",
"https://chemistry.stackexchange.com",
"https://chemistry.stackexchange.com/users/4625/"
] | I am not sure if this is a chemistry question; however, I was wondering:
In my desk I have two plastic, zip-lock bags. One contains cinnamon tea, the other contains nuts.
After about a week of these bags being next to each other, the flavor of the cinnamon somehow leached through both bags and now the nuts taste lik... | Cinnamon tea is most likely flavoured with cinnamalaldehyde (<strong>1</strong>) and eugenol (<strong>2</strong>), the main components in cinnamon oil. The latter compound also gives cloves the characteristic aroma.
<img src="https://i.stack.imgur.com/ZDUL6.png" alt="cinnamon aroma">
To my knowledge, ziplock bags are... | Cinnamaldehyde dissolves in and diffuses through most polymers within sensory threshold. Use glass containers with lined metal caps. Isn't ground up tree bark amazing?
| https://chemistry.stackexchange.com |
355,363 | [
"https://softwareengineering.stackexchange.com/questions/355363",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/277654/"
] | I have several classes that looks like: (some of them have dozens of cases)
<pre><code>function __construct($value) {
switch ($value){
case "1":
$value = Values::One;
break;
case "2":
$value = Values::Two;
break;
case "3":
$value =... | This kind of mapping logic is very easy to make mistakes in either when you initially write it or when an update is done.
You should have some test that verifies that the correct mapping is performed, including what happens if a value that can't be mapped is passed. If you have that as part of the tests for the parent... | If you do testdriven development one working example and a non-working axample is enought.
If you want an automatted test (with full coverage) writing the test is much more work than the actual implementation and you can never be shure if your test cover all aspects: i.e. if you later introduce a <code>Values::Fifteen... | https://softwareengineering.stackexchange.com |
18,794 | [
"https://chemistry.stackexchange.com/questions/18794",
"https://chemistry.stackexchange.com",
"https://chemistry.stackexchange.com/users/9475/"
] | Considering a general amphiprotic substance NaHA. I know that the maximum concentration of the specie $HA^-$ is found at $pH = \dfrac{pKa1+pKa2}{2}$. Why? How i can confirm this statment?
The equations are:
$$ \ce{HA^- + H_2O <=> A^{2-} + H_3O^{+}} \quad Ka2$$
and
$$ \ce{HA^- + H_2O <=> H_2A + OH^{-}} \qu... | Let's take an aqueous solution of a salt $\ce{NaHA}$ with the initial concentration $C$ when added to water. It will completely dissociate according to the eaquation: $\ce{NaHA(s) \rightarrow Na^+ +HA^-}$.
$\ce{HA^-}$ will participate in three equilibria:
$\ce{2HA^- \leftrightarrows H2A +A^{2-}\quad \quad \quad }$ ... | The usual answer for this kind of problem is to write down all species ($HA, A^-, H_2A^+, H_3O^+, OH^-$) and all equations for the various equilibria (don't forget autoionization!) and then find the maximum concentration of $HA$.
Try it! Try also various approximations. The exercise will increase your understanding ... | https://chemistry.stackexchange.com |
306,388 | [
"https://electronics.stackexchange.com/questions/306388",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/148869/"
] | I am working on converting an old ATX PSU to a lab bench power supply, and the guide I follow is putting a 5 ohm 10 watt dummy load resistor on the 5 V supply line. I don't have resistors of this value right now, can I instead put two 10 ohm 5 watt resistor instead? Or do I need a dummy load resistor at all?
| Yes, that would be fine.
The goal is to draw 1A from the 5V bus as a "dummy load". Each of your 10Ω resistors will draw 0.5A, dissipating 2.5W in the process. The two of them in parallel constitute the desired load.
| Yes. Putting the two resistors in parallel will share the power evenly between the two, as long as they're both the same resistance.
| https://electronics.stackexchange.com |
73,393 | [
"https://electronics.stackexchange.com/questions/73393",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/11120/"
] | I know two ways in which a VHDL variable is synthesized by synthesis tool:
<ul>
<li>Variable synthesized as Combinational logic</li>
<li>Variable synthesized as a Latch unintentionally (when an uninitialized variable is assigned to a signal or another variable)</li>
</ul>
What are the other ways in which a VHDL varia... | I would distinguish three possibilities:
<ol>
<li>A VHDL variable has no hardware representation at all. Assume the following example
<pre><code>signal a,b,c : integer;
...
process ( clk ) is
variable var : integer := 0;
begin
if ( rising_edge(clk) ) then
var := a + b;
c <= var;
end if;
end proc... | If you use the value in a variable before you store it, you get the value that was stored last time the process stored it (in a clocked process, the value from a previous clock cycle). That is synthesised as a register or FF.
Of course, in the first clock cycle you get garbage, unless you initialised the variable in a... | https://electronics.stackexchange.com |
58,067 | [
"https://mechanics.stackexchange.com/questions/58067",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/17522/"
] | It seems a lot of the questions regarding car storage are for prior to storage. I did not think ahead much and thus my question is for what to do after storage.
Context:
Car stored in non air conditioned but enclosed self storage unit in the Northeast US for around 2.5 months. No fuel stabilizer was added but tank was... | Start it and be done with it. 2.5 months sitting isn't really a big deal. You may need to charge the battery, but probably not. Just run it at idle until it warms up, check for leaks, drive it to the gas station and fill it up with fresh gas. You really shouldn't have any issues with it which weren't there before you p... | I agree with @Paulster2, save his advice to idle the motor until it warms up. Instead, minimize the time the engine is running but not yet warmed up (when the most engine wear occurs) by starting the engine and driving the vehicle. Still, don't abuse the machinery with heavy throttle application or high revs until the ... | https://mechanics.stackexchange.com |
428,790 | [
"https://electronics.stackexchange.com/questions/428790",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/216210/"
] | I have a question regarding the PI controller.
Lets say I have an actuator via which I control
some plant. The control signal at the output of
the PI controller is at its maximal realizable
value. So the actuator supplies 100% power
into the plant. Despite this fact the time
response of the control loop is sluggish. ... | If the control signal is at maximum and you are still not getting the system performance you want than the problem would be an under sized actuator.
Consider a controls engineer sitting in their car at a stop light that just turned green. The engineer would like to reach a speed of 40 Mph as soon as possible. So the... | <blockquote>
Does it mean that the actuator has been chosen in wrong manner for a
given plant?
</blockquote>
If the actuator is at a point where it cant give additional energy its called a saturation point. Saturation points are bad because:
<ul>
<li>it makes the system hard to analyze because it no longer behave... | https://electronics.stackexchange.com |
98,548 | [
"https://softwareengineering.stackexchange.com/questions/98548",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/12828/"
] | <strong>The debate:</strong> Should all development, including refactoring work, be accompanied by a tracking issue? (in our case, Jira)
<strong>The common ground:</strong> Our primary goal is quality. A working product, every release, is more important than anything else. Our codebase is old and automated tests are l... | Perhaps I'm missing something here, but how does creating a ticket for work you are doing that doesn't fall within the scope of your other tickets a 'resistance layer'?
Have you recently implemented using a ticket tracking system? If so, then sit down and make your rules for using it and let the team know that they a... | I think that if you can't describe the refactoring more specifically than "refactoring", you're doing it wrong. Refactoring should have a definite purpose and scope. Tracking the refactoring tasks separately in JIRA not only makes auditing, review and testing easier, but also forces the refactorers to focus their minds... | https://softwareengineering.stackexchange.com |
1,368,815 | [
"https://math.stackexchange.com/questions/1368815",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/135843/"
] | Let $U\subset\mathbb{R}^n$ be an open set. I proved that
$$
H^0_{DR}(U):=\frac{\text{closed forms}}{\text{exact forms}}=\{f\in C^{\infty}(U):\,f\,\,\text{is locally constant} \}
$$
I have to show that $\dim H^0_{DR}=\text{number of connected components of}\,\, U$.
Here is my incomplete proof.
Let's write $U=\bigcu... | A function $f : U \to \mathbb{R}$ is <em>locally constant</em> if for each $x \in U$, there is an open neighbourhood $V$ of $x$ such that $f|_V$ is constant.
Note that for any $y \in \mathbb{R}$, $f^{-1}(y)$ is open, so for any $A\subseteq \mathbb{R}$, $f^{-1}(A) = \bigcup_{y\in A}f^{-1}(y)$ is open. In particular, $... | Hint: Suppose $X$ is a non-empty connected open set, and that $f:X \to \mathbf{R}$ is locally constant. Pick an arbitrary point $x_{0}$ in $X$, and let $U = \{x \in X : f(x) = f(x_{0})\}$.
Use local constancy of $f$ to prove $U$ is open and closed in $X$.
| https://math.stackexchange.com |
13,883 | [
"https://astronomy.stackexchange.com/questions/13883",
"https://astronomy.stackexchange.com",
"https://astronomy.stackexchange.com/users/10948/"
] | When an object in the space comes close to a massive body (like a black hole or a neutron star), we see from Earth that its speed significantly increases while it is close to the body. As we know, this is due to space distortion around massive objects known as gravity. But also, gravity causes time dilation, so an obse... | If you jump out an aeroplane, do you experience high speed? Many people would say you do, since your velocity relative to the ground increases.
Note the importance of the phrase "relative to the ground" since to describe speed you always need to say what you are measuring the velocity relative to.
A simple choice i... | If we move around the black hole speed of the end will become more than initial point because time remains stretched near it.relatively we don't see much difference but in other frame of reference it seems quite stationary .
| https://astronomy.stackexchange.com |
13,261 | [
"https://dsp.stackexchange.com/questions/13261",
"https://dsp.stackexchange.com",
"https://dsp.stackexchange.com/users/4831/"
] | I understand FIR & IIR digital filters are often implemented in fixed point DSP hardware. I have also seen them implemented in software. Do companies make special purpose digital filtering chips that use floating point precision (float) and (double)? When fixed point hardware is used, what are the choices for the b... | Almost all such programming is done in C, which means that 16 bits (shorts) and 32 bits (ints) make sense. I doubt it will surprise you that most chips support those bit widths, with 16 bits being a particular favorite because it is wide enough to be useful and narrow enough to be power efficient, small, and fast.
I ... | Most higher-end DSP chips have single-cycle multiply floating point hardware. Examples are Analog Devices Sharc or Texas Instruments C6X.
Audio processing is an interesting case for fixed point. 32-bit is overkill, while 16-bit is really not enough for processing. 24-bit is therefore a good choice, and the Motorola (... | https://dsp.stackexchange.com |
178,534 | [
"https://electronics.stackexchange.com/questions/178534",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/80263/"
] | I'm quit new one PIC microcontroller, and i'm stuck with a new problem.
I was using the A/D converter of my PIC18F46j50 to catch 4 push buttons on 1 PIN (RB2), and it worked well. But since I soldered a 32.768kHz oscillator for Timer1, it doesn't work anymore.
<pre><code>unsigned int HAL_SWITCH_GetValADC(void){
A... | <code>ADCON1bits.ACQT = 0b111</code> <- that's not 12 Tad, but 20 Tad (according to datasheet), which translates roughly to 20us. Try using 0b101, for the value you are trying to achieve. Try setting bit 6 of ADCON1 register (ADCAL, responsible for automatic calibration) to 1 and running your code again.
You have al... | One way I know of acknowledging whether the conversion is complete is reading the GO/DONE bit of ADCON0. The bit goes low once the conversion is complete. So you can use
<pre><code>ADCON0bits.GO=1;
while(ADCON0bits.GO);
</code></pre>
If you still want to go with ADIF, you should make sure you have enabled the ADC int... | https://electronics.stackexchange.com |
641,927 | [
"https://electronics.stackexchange.com/questions/641927",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/320521/"
] | What I get is that, considering a 2 stage OTA, we have 2 effects that limit the amplitude and frequency of the amplified signal:
<ul>
<li>Bandwidth of the amplifier: as the frequency of the input signal gets higher exceeding the bandwidth, the gain at which it is amplified gets lower</li>
<li>Slew rate of the amplifier... | Slew rate limiting occurs when the input signal amplitude (the difference voltage between the inputs) gets large enough to result in all the input stage tail current being sunk alternately down one side of the input differential pair and then down the other over 1 complete cycle of the input signal.
When this occurs th... | <blockquote>
<em>so how are they different in their effect?</em>
</blockquote>
<ul>
<li>The bandwidth of the amplifier affects small signals as well as large signals</li>
<li>The slew rate limit affects large amplitude output signals and may not affect smaller amplitudes</li>
</ul>
Basically, what you implied (to me) i... | https://electronics.stackexchange.com |
20,455 | [
"https://physics.stackexchange.com/questions/20455",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/4877/"
] | A common analogy for gravity is the ball-on-a-rubber-sheet model. In this model, mass distorts spacetime and creates a 'valley' into which other mass can fall. Is this same principal valid for magnetic fields as well (proton-electron)? If so, then how is the repulsion effect modelled?
I ask because the underlying prop... | Two things:
First, it is more intuitive to treat gravitational force as equivalent to electrostatic force, due to the existence of monopoles (and gravitational field lines do not form closed loops). There is a magnetic analogue to gravity, known as gravetomagnetism, frame-dragging, or the Lense-Thirring effect.
Ok, no... | It's fine to think of both the gravitational and electromagnetic fields as geometric objects. Once we have physics, interpretation is left up to the individual; however clearly some interpretations are better then others.
There are some analogies between gravity and E&M, but they don't last very long. Maybe one ... | https://physics.stackexchange.com |
335,191 | [
"https://electronics.stackexchange.com/questions/335191",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/166202/"
] | I have a question regarding the following situation:
Some poultry farm has taken some serious losses when their diesel generator died, only being able to provide backup for 45 minutes and killing several ten of thousand of chickens. The reason they had to switch to the generator was because the power grid voltage was ... | When current flows in a coil there's a magnetic field being generated, this magnetic field has more or less a shape of a donut. It doesn't matter where it starts or ends, as long as the current generating the magnetic field is always strengthening the "donut".
| Certainly, and it's often done with commercial power transformers. But.
It is critical that you guarantee that each layer of windings is isolated from the others. This is usually done with a layer of Kraft paper or something like Teflon tape.
| https://electronics.stackexchange.com |
78,233 | [
"https://dsp.stackexchange.com/questions/78233",
"https://dsp.stackexchange.com",
"https://dsp.stackexchange.com/users/58882/"
] | In my setting, I have different microphones recording a same speech signal. For each microphone recording, I can feel a slight difference in the playing sound. I am calling this property of a particular microphone as its texture.
Is there a way to eliminate this texture so that when I mix the recordings, I get one clea... | So, first of all, a filter in signal processing is analogous to a filter that you'd use on liquids. A coffee filter passes through the stuff you want (liquid coffee), and holds back the stuff you don't want (coffee grounds). It does this because the coffee grounds are bigger than water molecules, and all those yummy ... | <blockquote>
What features from them do I need to know in order to determine a strategy to remove them ?
</blockquote>
Likely the most important feature you need to know about these noises is their <em>spectral content.</em> In other words, you need to know how the energy of each of noise is spread out across different... | https://dsp.stackexchange.com |
465,828 | [
"https://physics.stackexchange.com/questions/465828",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/164488/"
] | Can someone explain what is the meaning of single particle states? I found this on Huang's book on statistical mechanics while writing distribution functions (e.g, Bose-Einstein or Fermi-Dirac). We were dealing with states of the full system in the partition function and suddenly why did we need single particle states?... | A single-particle state is the eigenstate of a single-particle hamiltonian, i.e., a hamiltonian describing a single particle, usually without interactions with other particles.
| A single particle state is defined as that which belongs to a vector space associated with an irreducible representation of the Poincare algebra and other internal symmetries. Please refer to The Quantum Theory of Fields, Volume 1, Chapter 2 by Steven Weinberg.
| https://physics.stackexchange.com |
187,934 | [
"https://electronics.stackexchange.com/questions/187934",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/84291/"
] | Let's say I have a single-phase facility and I plug in a piece of 3-phase equipment, what happens?
<ol>
<li>Is it dangerous?</li>
<li>Is it less efficient (if so, approximately how many percent less in efficiency)?</li>
<li>What kind of adjustments, if any, would I have to make to make this setup work?</li>
<li>Would ... | If you have a single-phase facility, you can't just plug in a piece of 3-phase equipment. You will need to find a way to adapt it for single-phase power. That will probably not be particularly easy and might not be possible at all. It could be done with no loss in efficiency and performance, but is more likely to be le... | Most single-phase equipment will work fine on three-phase, assuming all other necessary specs are met. You just connect two of the three legs. The load doesn't know there's a third leg and two more phases running around the universe somewhere, any more than your 110V blender knows there's a 220V outlet that your dryer ... | https://electronics.stackexchange.com |
13,429 | [
"https://electronics.stackexchange.com/questions/13429",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/1319/"
] | Can I use an AC solid state relay to control a DC current as long as the DC voltage doesn't exceed the rated AC voltages?
I want to control a solenoid but I'm concerned about the inductance problem of the device. Will a solid state relay survive the back EMF of the solenoid when turned off by itself?
| It depends on the relay. Many solid state relays use a thyristor as their main switching component, and a thyristor can't be turned off simply by removing the trigger voltage. They rely on the reverse-bias portion of the AC cycle to switch off. Other solid state relays use FETs as their switching component and those re... | The answer is no! There is a diode in reverse on most MOS devices a which will allow the current to run backwards into your circuit.
A thyristor will block the reverse current, but cannot be turned off while the current is positive.
Thyristor regulators turn on part of the cycle and turn off when the voltage goes to ze... | https://electronics.stackexchange.com |
18,352 | [
"https://electronics.stackexchange.com/questions/18352",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/659/"
] | I would like to make a good surge protector for a device that will have a hardwired mains connection. The protected electronics will consist of a ~10W SMPS and a low-power AC load (<100W) controlled with a triac.
I plan to use a mains filter (nothing fancy) behind some combination of GDTs (Gas Discharge Tubes), MOV... | A MOV is an essential part of your mains-side safety circuitry (despite what user886922 says). 300V MOVs are commonly used to protect universal input (85-264VAC) power supplies. The MOV is sized such that the energy it can crowbar safely is more than enough to blow the mains fuse, which will provide the necessary disco... | MOVs/TVSs/etc on mains lines are mostly useless. Ask yourself if you can picture a combnination of MOV/TVSs etc being effective agaisnt all the power available at the mains.
Any effective suppression will work by disconnecting the mains from the load, which complicates the design significantly as you need both a means... | https://electronics.stackexchange.com |
400,072 | [
"https://physics.stackexchange.com/questions/400072",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/117996/"
] | The fermi temperature is defined as
$$ k_BT_f = E_f$$
But the fermi energy is the energy at $T=0$, where the energy level is the highest occupied for electrons. So, why is the fermi temperature defined as $\neq 0$?, What temperature $T_f$ is measured? Over who is T measured?
| With the car falling off the cliff there is a downward gravitational attractive force on the ball due to the Earth and yet the ball (the system) does not move relative to the car.<br>
So there is a fictitious force on the ball which equal in magnitude and opposite in direction (upwards) to the downward gravitational at... | <blockquote>
But now let's say this car with the person inside fell off a cliff. If he let go of a ball in his hand, the ball will not go to the back of the car.
</blockquote>
First of all, there is <strong>not</strong> equivalence between a car accelerating at $9.8m/s^2$ and a car falling down the cliff.
The equi... | https://physics.stackexchange.com |
327,078 | [
"https://electronics.stackexchange.com/questions/327078",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/161494/"
] | I have came across a question while working on assembly language. Here is the question:
Assume that bit P2.2 is used to control an outdoor light and bit P2.5 a light inside a building. Show how to turn on the outside light and turn off the inside one.
Solution given:
<pre><code>SETB C ; CY = 1
ORL C, P2.... | You are right in that it appears the code you show is silly. Perhaps whatever machine this runs on can't do immediate operations to set bits on I/O ports, and that that's why something like SETB P2.2 isn't possible.
Still setting the CY bit to 1, then ORing anything into it is just plain silly. The same goes for se... | The code is almost certainly for a processor using the 8051 instruction set. On that processor, the code variation you give would have the same effect as the original except that it would run faster. Executing "ORL C,P2.2" when carry is set will have no observable effect except to waste some number of cycles (two CPU... | https://electronics.stackexchange.com |
66,585 | [
"https://dba.stackexchange.com/questions/66585",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/29717/"
] | I have two columns in my table a <code>varchar(8)</code> titled <code>Trans_Time</code> which holds data in an <code>XX:XX:XX</code> time format and a <code>DateTime</code> column named <code>Trand_Date</code> which holds just a the date component in <code>XX-XX-XXXX</code> format.
I am trying to combine the two colu... | You can use ISNULL or COALESCE in T-SQL to replace a null value:
<pre><code>SELECT
Trand_Date + ' ' + COALESCE(Trans_Time, '00:00:00') AS Trand_DateTime1,
Trand_Date + ' ' + ISNULL(Trans_Time, '00:00:00') AS Trand_DateTime2
FROM MyTable
</code></pre>
Both columns above should return the same value. Note that if ... | Try using isnull to replace the null value.
<pre><code>select isnull(null, '00:00:00')
</code></pre>
| https://dba.stackexchange.com |
4,157 | [
"https://mechanics.stackexchange.com/questions/4157",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/2095/"
] | I have a curved area on fibreglass with a dent in it. I have filled it with body filler but when I sand it back there is still an obvious ridge where the filler meets the body. I have sanded it down and repeated this many times but still get the same result. I have tried course and fine sand paper but each time I apply... | Years ago we used something called "red putty" it is made by 3M available at autobody supply shops.. It was applied over the bondo. It acted like a thick primer that came in a can. It was smoother and thinner than filler so the edges feathered smoother.
| I got a tip from a friend that was also helpful: wet the sand paper and use a wide circular motion over the area with light to medium pressure. Keep dipping the sand paper in the water to remove build up of grit. Repeat with varying degrees of course to fine sand paper.
| https://mechanics.stackexchange.com |
218,887 | [
"https://electronics.stackexchange.com/questions/218887",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/101270/"
] | I am making a PCB with Eagle and I need to place some leds SMD size 1206. Looking components, I see two different types of LEDs in this size: SML and SMT. Eagle components are LEDSML1206 and LEDSMT1206. Could anyone tell me the difference between them exactly?
Also happens something similar with resistors. In this cas... | Don't waste time on the libraries that come with Eagle. They were created by various different people, don't follow any coherent conventions, and won't likely work with your conventions for BOM information, generating the assembly drawing, parts locator, in-house part numbers, etc.
When in doubt, go make your own lib... | SML appears to be a Lumex specific acronym or part number. I wouldn't put much faith in the library parts you've found.
Instead, read the data sheet for the PCB layout and compare it to the pad layout of the various parts that should fit in the library, or create your own.
Chances are good that you could choose eithe... | https://electronics.stackexchange.com |
287,458 | [
"https://softwareengineering.stackexchange.com/questions/287458",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/184367/"
] | When applying the interface segregation, should you have separate interfaces for a straightforward setters and interfaces that perform an operation before setting? For example, say you have a class:
<pre><code>class FooClass:
public GettableFoo,
public SettableFoo
{
virtual int getRelevantData();
... | There are a number of reasons why you want to store you lookups in a database.
<ol>
<li>Referential integrity. If you set up the database correctly you CANNOT insert a row unless the lookup exists (foreign key constraint). There is currently nothing stopping me inserting integer 0 or 9999 and your array lookup will fa... | You are suggesting a <strong>client-side join</strong>: Fetch some data from the database via a query, and then in code you perform further joins via lookup tables loaded from files.
This is almost certainly going to be slower, and definitely more complex than just doing the join in the database. Think about it - why... | https://softwareengineering.stackexchange.com |
30,572 | [
"https://mathoverflow.net/questions/30572",
"https://mathoverflow.net",
"https://mathoverflow.net/users/1916/"
] | Sorry if this is an easy one, I'm a little rusty on my group theory. My first guess was that it's simply the inverse limit of the Aut($\mathbb{Z}/p^i\mathbb{Z})$, with the map when $i\leq j$ given by taking $\sigma\in$ Aut$(\mathbb{Z}/p^j\mathbb{Z})$ to the map $\tilde{\sigma}:\mathbb{Z}/p^i\mathbb{Z}\rightarrow\mathbb... | First the <span class="math-container">$p$</span>-adic integers are finitely generated (actually cyclic) pro-<span class="math-container">$p$</span> group therefore from a result of Serre all automorphisms are continuous. Now as it cyclic it is enough to see what happens to <span class="math-container">$1$</span>. It h... | Any automorphism of $\mathbb{Z}_p$ preserves whether an element is divisible by $p^k$, so it is Lipschitz (in particular, continuous) with respect to the $p$-adic norm. <strike>On the other hand, any automorphism must preserve $\mathbb{Z}$, which is dense in $\mathbb{Z}_p$.</strike>
What I should've said is that any ... | https://mathoverflow.net |
311,972 | [
"https://softwareengineering.stackexchange.com/questions/311972",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/212019/"
] | Memory (and resource locks) are returned to the OS at deterministic points during a program's execution. The control flow of a program by itself is enough to know where, for sure, a given resource can be deallocated. Just like how a human programmer knows where to write <code>fclose(file)</code> when the program is don... | Take this (contrived) example:
<pre class="lang-c prettyprint-override"><code>void* resource1;
void* resource2;
while(true){
int input = getInputFromUser();
switch(input){
case 1: resource1 = malloc(500); break;
case 2: resource2 = resource1; break;
case 3: useResource(resource1); us... | RAII is not automatically the same thing, but it has the same effect. It provides an easy answer to the question "how do you know when this cannot be accessed any more?" by using <em>scope</em> to cover the area when a particular resource is being used.
You might want to consider the similar problem "how can I know my... | https://softwareengineering.stackexchange.com |
53,615 | [
"https://chemistry.stackexchange.com/questions/53615",
"https://chemistry.stackexchange.com",
"https://chemistry.stackexchange.com/users/31006/"
] | I'm currently removing rust on some bike parts so decided to use electrolysis. It's working fine, but the solution has turned a deep/dark blue whilst in most online videos it turns orange with the rust. My sacrificial anodes aren't stainless or chromed, and I dont believe they're galvanized either.
Is the blue colour ... | If your anode/cathode are from copper, then the blue chemical in the solution is copper chloride (<strong>CuCl2</strong>). Copper chloride can be toxic. So you should have safety equipment.
As for rust removal in general, I'd recommend you to use Citric acid (Squeezing lemons for the lemon juice isn't efficient sinc... | I recommend using citric acid
Burn it with blowtorch later so it does not get rust.
| https://chemistry.stackexchange.com |
421,657 | [
"https://softwareengineering.stackexchange.com/questions/421657",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/367979/"
] | Lately I got in a discussion with my colleague whether the appsettings.Development.json should be added to the git repository or not.
My considerations are: when a developer clones a repository to his development machine and builds the application, he should be able to run the application without any tweaking of the se... | <blockquote>
when a developer clones a repository to his development machine and builds the application, he should be able to run the application without any tweaking of the settings
</blockquote>
In an ideal world, it would indeed be the case. Moreover, some open source projects, including very large and complex ones,... | There's a situational case to be made for either approach.
I generally side with you here, but it's the use of absolute paths that's mostly the issue here. Using absolute paths directly negates the ability to have the same codebase work on different machines.
If the absolute paths are unavoidable, you can't really have... | https://softwareengineering.stackexchange.com |
275,168 | [
"https://mathoverflow.net/questions/275168",
"https://mathoverflow.net",
"https://mathoverflow.net/users/112089/"
] | In homotopy type theory, or dependent type theories more generally, there is a "top-level" type called the universe, generally denoted $\newcommand{\type}{\mathtt{Type}}\type$. So for a concrete example, I could describe having 3 types: $\mathtt{Nat}$, $\mathtt{Real}$, $\mathtt{Complex}$ and the type of those types wou... | This question is about type theory in general and is not specific to homotopy type theory. $\newcommand{\Type}{\mathtt{Type}}$
The thing you are missing is that <strong>a universe $\Type_k$ contains very many types</strong>, not just one as you claim. Each $\mathtt{Type}_k$ is closed under type forming operations $\ti... | We usually assume that universes are closed under all type constructions. So, Type$_0$ contains Nats, Reals, Complex; Type$_1$ contains Nats, Reals, Complex, and Type$_0$; Type$_2$ contains Nats, Reals, Complex, Type$_0$, and Type$_1$; and so on.
Even if we define a type theory, where the only term of type Type$_{k+1}... | https://mathoverflow.net |
138,245 | [
"https://electronics.stackexchange.com/questions/138245",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/18851/"
] | I have this simple circuit. And from what I calculated the output impedance seen from the OUT node comes to about \$138.765 \Omega\$.
$$ X_c = \frac{1}{2\pi * 890*10^3 * 10^{-9}} = 178.8257\Omega $$
$$ Z_{out} = R2||X_c = \frac{220 * 178.8257}{\sqrt{220^2 + 178.8257^2}} = 138.765\Omega$$
<img src="https://i.stack.imgu... | I finally understood what was wrong.
Without the load resistor, the impedance seen at the OUT node is a complex number.
$$\dfrac{1}{Z_{out}} = \dfrac{1}{R2} + \dfrac{j}{X_c} $$ Thus,
$$ Z_{out} = 87.527 - j107.678\Omega$$
With that Load resistor of 138.765 \$\Omega\$, the total impedance of the circuit becomes,
$$ Z_... | The output impedance can be calculated from 1/(1/Xc + 1/R)
Xc = \$1 \over j\omega C \$
R = 220\$\Omega\$
The admittances add in quadrature since one is imaginary and the other is real-
It is easy to show(tm) that the magnitude of the impedance Z is as follows:
|Z| = \$ R \cdot (\frac {1}{\omega C}) \over \sqr... | https://electronics.stackexchange.com |
16,812 | [
"https://physics.stackexchange.com/questions/16812",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/3953/"
] | By comparatively examining the operators
<img src="https://i.stack.imgur.com/Ox5jp.png" alt="">
a student concludes that `Energy is actually the momentum in the direction of time.' Is this student right? Could he be wrong?
| The student is right in that energy is the analog of momentum in the "time direction" but I wouldn't go so far as to call it "momentum in the direction of time".
It's analogous in two ways that I can think of off the top of my head:
<ol>
<li>It is the time-component of the 4-dimensional energy-momentum vector in spec... | Energy is very momentum-like in Relativity theory. For a photon, which has zero rest mass, its energy is the absolute value of its momentum. But not for the reason your student puts forward. What your student said has to be reinterpreted quite a bit.
The first technicality, and it is important, is that $H$ does no... | https://physics.stackexchange.com |
14,790 | [
"https://bioinformatics.stackexchange.com/questions/14790",
"https://bioinformatics.stackexchange.com",
"https://bioinformatics.stackexchange.com/users/-1/"
] | Here is the input file for nab:
<pre><code>molecule m;
m = arna( "gcuucuucuucuucgc" );
putpdb( "lr16.pdb", m, "-wwpdb -nocid -tr");
</code></pre>
I am trying to run nab to create the pdb file with this command :
<pre><code>$AMBERHOME/bin/nab lr16.nab\./a.out
</code></pre>
But it comes out ... | Here is a bash/awk solution:
<pre><code>awk -F'\t' 'NR==1{print}; NR>1{N=0;for(i=2; i<(NF+1); i++){if($i >= 0.0001) N++}; if(N>0.1*NF) print}' input.tsv
</code></pre>
We make sure the input field separator is tab, then we loop on the number of fields (NF) and add to the tally the <code>N</code> of fields ab... | Assuming you have this stored in a matrix called <code>m</code>, where the pathway labels are row names:
<pre><code>IDX = apply(m, 1, function(x) sum(x > 0.0001)/length(x) >= 0.1)
m_subset = m[which(IDX),]
</code></pre>
| https://bioinformatics.stackexchange.com |
59,849 | [
"https://dba.stackexchange.com/questions/59849",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/34932/"
] | I try to select the period of employment for the members in a Company.
Example:
Date of join: 01.01.2001
Today: 27.02.2014
Now, I want this:
13 years, 1 month and 27 days
I have a Statement which works on MSSQL, but I cant translate it to firebird-SQL.
Could anybody help me?
Thx
Erik
| Relatively green Firebird n00b here w/a fair PostgreSQL background, although specialized GIS work focused mostly to DB design and the sourcing/cleaning/making spatial multi-source data sets (usually of dubious quality) and then querying for map-able results in answer to specific location riddles. Toolbox is light, ther... | <pre><code>YEARS=DATEDIFF(YEAR FROM :BEGIN_DATE TO :END_DATE);
MONTHS=DATEDIFF(MONTH FROM :BEGIN_DATE TO :END_DATE);
DAYS=DATEDIFF(DAY FROM :BEGIN_DATE TO :END_DATE);
</code></pre>
| https://dba.stackexchange.com |
71,099 | [
"https://electronics.stackexchange.com/questions/71099",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/24610/"
] | Apologies if this is a dumb question. I don't have any training in electrical engineering, so I can't gauge for myself how ridiculous this sounds.
Would it be possible to modify a commercial CPU so that it does not have to be directly in contact with the motherboard?
That is, with the right conducting medium, would ... | I'm not sure why you'd want to do this, but with the socketed processors you could build an extender that lets you move the CPU a short distance off the motherboard.
You can't move it a <em>long</em> way off the motherboard because the increased signal propagation time becomes signifigant. A 1GHz signal has a cycle ti... | Not in the conventional meaning of terms such as "motherboard", but in effective functional terms then yes.
For example, you could take a smartphone, and connect it to a simple desktop computer via wifi or bluetooth. Have a program actually run on the phone's CPU, but use the desktop display, keyboard, and mouse for ... | https://electronics.stackexchange.com |
64,931 | [
"https://mathoverflow.net/questions/64931",
"https://mathoverflow.net",
"https://mathoverflow.net/users/2177/"
] | Given a finite-dimensional semisimple complex Lie algebra $\mathfrak{g}$, the Bernstein-Gelfand-Gelfand category $\mathcal O$ is the full subcategory of $\mathfrak g$-modules satisfying some finiteness conditions. It contains all finite-dimensional modules as well as all highest-weight modules, it's Noetherian and Arti... | I'd add to what Ben says the observation that people have found a number of different module categories valuable for different purposes within this same Lie algebra context. (And some Lie theory people don't really find category $\mathcal{O}$ to be all that important in their own work.) Even two people close to th... | It's actually not the minimal category with those properties. For example, the subcategory of category O where the center of $U(\mathfrak{g})$ acts semi-simply is smaller and satisfies all of those. It does become essentially minimal (I think you also want to impose closed under passing to sub- or quotient objects) if... | https://mathoverflow.net |
327,135 | [
"https://electronics.stackexchange.com/questions/327135",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/161705/"
] | I am writing some RTL for IPs for personal learning. Right now, they don't implement any bus interfaces for communicating between each other. I was looking around and thought about implementing the Wishbone bus protocol as it is doesn't look to complicated.
I have a question regarding what exactly master/slaves means ... | Yes, I think that all your comments are correct.
A master requests data (or sends data) to the slaves.
A slave cannot originate a bus transaction. It must wait until the master communicates to it. In a bus with many slaves, the master can communicate with all of them but the slaves cannot communicate between them.
Fo... | A 'master' makes requests and a 'slave' responds to requests. Similarly, a slave cannot make requests and the master cannot respond to requests. The master device may drive (possibly shared) control (clock, chip select, read enable, write enable, address latch enable, etc.) and address lines. Usually both the master... | https://electronics.stackexchange.com |
170,368 | [
"https://electronics.stackexchange.com/questions/170368",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/75908/"
] | I am new to electronics and am trying to wrap my head around the various tools used for producing various digital components.
My <em>understanding</em> of HDL languages like VHDL and Verilog is that they describe the behavior of chips/ICs and are ultimately used to fabricate FPGAs and ASICs.
My <em>understanding</em>... | <blockquote>
are my assertions above correct?
</blockquote>
Everything you have written above that line is correct.
This is a multipart question. At the very top system level, you will find surprisingly heavy use of Word and Visio to produce a series of block diagrams. The different specialisations will then be han... | What you really want is a suite of tools that are integrated (from the same vendor) that allow you to go from design capture (schematic and/or hardware description language) all the way through to PCB design and perhaps automatic routing of the PCB, to output of files which can then be delivered to a PCB manufacturer.
... | https://electronics.stackexchange.com |
221,720 | [
"https://softwareengineering.stackexchange.com/questions/221720",
"https://softwareengineering.stackexchange.com",
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] | Our teamlead said that many files much worse than a single, despite of we are working on a big project.
He argued that our customers could more easily send logs to us if there will be just a single file.
To understand our log-file he wants to develope our own log-analyzer which will analyze a single log-file separati... | Please note that "best practice" questions are discouraged, because they are too easily answered as if there were a single way of doing something that is superior to all others. Almost always, there isn't such a way.
When deciding whether to use one log stream or different ones simultaneously, you have to weigh what t... | I think I would even prefer a logfile with everything in it.
My experience so far is that logfiles are especially useful for bugs where there is a problem in the communication between your subsystems. If they all log to the same file, it makes the problem easier to diagnose, because you can see the timeline of what i... | https://softwareengineering.stackexchange.com |
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