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 |
|---|---|---|---|---|---|
322,793 | [
"https://stats.stackexchange.com/questions/322793",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/191180/"
] | My data set contains the percentage cover of various plant species, on a rocky substrate. The problem I am having is that the substrate was often completely bare of any plant life. Due to this, a large proportion of the quadrats that I used contained zero percentage cover, which leads me to having heavily right-skewed ... | Asking the user to <strong>label</strong> faces means that it is <strong>supervised</strong>.
I don't see an explicit requirement to, e.g., cluster images and ask the user to label only clusters (which probably is too hard to do). I also do not see any reinforcement, or active / semi-supervised things (yes, the user w... | I highly doubt that the purpose of such a system would be "to find similar faces", this doesn't make any sense. Its purpose is to classify <em>known</em> individuals that appear on <em>unseen</em> photos, i.e. identify the same pattern (face) in unseen data. The act of asking the user for the names of individuals in so... | https://stats.stackexchange.com |
52,900 | [
"https://physics.stackexchange.com/questions/52900",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/-1/"
] | Suppose I have surface A in contact with surface B, if I apply Fourier's law of heat transfer, which $K$ should I use, $K_a$ or $K_b$?
Essentially asking whether the same block of material heats faster in 300 degree water or 300 degree air or the same.
| I'm going to add some mathematical detail to what akhmeteli has said.
Let's restrict the discussion to one dimension with coordinate $x$, then Fourier's law in differential form says
$$
q(x) = -k(x) T'(x)
$$
where $q(x)$ is the local heat flux, $k(x)$ is the conductivity, and $T(x)$ is the temperature gradient. N... | You should use the Fourier law in its differential form and use the actual temperature in each point. In your case, it is not important that temperature, strictly speaking, is not unambiguously defined at the contact surface (initially). You can still solve the equation of heat transfer (using distributions).
| https://physics.stackexchange.com |
6,867 | [
"https://dba.stackexchange.com/questions/6867",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/4241/"
] | I know shrinking the log is counter-indicated and has been covered many times, but I just encountered the following, baffling scenario:
We had a run-away query attempt to delete so many records that the transaction log file grew to 30GB on a Windows Server 2008-R2 machine running SQL Server 2008 with the database set ... | "<strong>Shrinking</strong>" the log is actually "<strong>clearing</strong>" the log.
The log is basically a list of operations that have been performed, and is used as a reference for rollbacks, restores, checkpoints, etc.
The space wasn't "unused" but it contained transactions that had been committed and were refle... | Shrinking the log does not loose any <em>uncommited</em> log data, i.e. the log file after truncation can still be used to recover the current state of the database, from its most recent backup and from the log file (Assuming FULL recovery mode).
Shrinking the log is merely a matter of "repacking" the useful data tow... | https://dba.stackexchange.com |
67,969 | [
"https://dsp.stackexchange.com/questions/67969",
"https://dsp.stackexchange.com",
"https://dsp.stackexchange.com/users/50184/"
] | I have audio samples with three classes :
<pre><code>100 audio samples : class 'A'
100 audio samples : class 'B'
100 audio samples : class 'C'
</code></pre>
<code>Class 'A'</code> and <code>Class 'B'</code> audio samples are recorded from one phone mic with same setting ( distance, volume etc ) but <code>class 'C'</c... | We can't tell you what your classifier does, sorry.
But yes, you have a systematic bias in your data, and your classifier will cling to whatever is the strongest discriminator if it works as hoped. I will rename your classes to make this clearer:
<ul>
<li>100 audio samples : class 'Microphone 1 subclass 1'</li>
<li>1... | Two techniques are useful to increase robustness of your model: Normalization and
Data Augmentation.
<em>Normalizing</em> the inputs to the models can be used to remove the difference in audio level between classes, samples, distance from-source, or device the data comes from. A common method with spectrogram as featur... | https://dsp.stackexchange.com |
295,228 | [
"https://softwareengineering.stackexchange.com/questions/295228",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/194164/"
] | I am trying to figure out recursive backtracking, i have good understanding of recursion and till some extent the concept of backtracking too but i am having difficulty understand the chronological order of how things are working when for loop is being used in following code.
<pre><code>public static void diceRolls(i... | You may imageine backtrack as if you were walking through a dungeon and you must explore all the paths in the dungeon (the dungeon is acyclic - you will never come back to the same place regardless the path you choose). When you come to a place which forks to multiple paths, you choose only one and follow it. Only afte... | Try running the following:
<pre><code>public static void diceRolls(int dice) {
List<Integer> chosen = new ArrayList<Integer>();
diceRolls(dice, chosen);
}
// private recursive helper to implement diceRolls logic
private static void diceRolls(int dice,List<Integer> chosen) {
System.out.p... | https://softwareengineering.stackexchange.com |
89,034 | [
"https://mechanics.stackexchange.com/questions/89034",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/72437/"
] | I have a Land Cruiser 2010. It's the third time this is happening. Any USB stick that's connected to the Audio USB/AUX port gets super hot and stops working after a few seconds. Yesterday I connected a bluetooth receiver in this port as well and it was killed the same way. I'm sure this USB port is for music and not ch... | <strong>The port is badly broken, stop using it until you get it fixed.</strong>
If it has always been like this, chances are the port is miswired so that the +5V and ground pins are swapped (perhaps an internal cable plugged in the wrong way round). The reverse polarity would almost certainly destroy any devices plugg... | If you have a multimeter, you can check what is going on. Find an old usb cable you have lying around, and strip it until you get 4 wires. Then, find which wires are 5V and Ground by using the continuity test and a usb pinout online.
After you have identified these wires, plug the cable in and test the 5V and Ground wi... | https://mechanics.stackexchange.com |
666,357 | [
"https://physics.stackexchange.com/questions/666357",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/208833/"
] | In flat space, the motion of freely falling particles given by the parametrized path <span class="math-container">$x^\mu(\lambda)$</span> is given by the geodesic equation
<span class="math-container">$$\frac{d^2x^{\mu}}{d\lambda^2}=0.$$</span>
Why is this not a tensorial equation?
From my understanding, <span class="m... | <span class="math-container">$A^\mu(\lambda) \equiv \frac{dx^\mu}{d\lambda}$</span> are the <strong>components</strong> of a <span class="math-container">$(1,0)$</span>-tensor <span class="math-container">$\mathbf A = A^\mu \left.\frac{\partial}{\partial x^\mu}\right|_{x(\lambda)}$</span> attached to the point <span cl... | Your equation will only be a tensor if you are in flat Minkowski spacetime with an affine coordinate system. The reason is that the partial derivative is simply not a tensor.
The velocity of a point moving along a curve <span class="math-container">$x^\mu (\lambda)$</span> is given by
<span class="math-container">$$\ma... | https://physics.stackexchange.com |
37,551 | [
"https://mathoverflow.net/questions/37551",
"https://mathoverflow.net",
"https://mathoverflow.net/users/8755/"
] | I'm trying to understand the necessity for the assumption in the Hahn-Banach theorem for one of the convex sets to have an interior point. The other way I've seen the theorem stated, one set is closed and the other one compact. My goal is to find a counter example when these hypotheses are not satisfied but the sets ar... | Here is a simple example of a linear space and 2 disjoint convex sets such that there is no linear functional separating the sets. Note that the notions of convexity and linear functional <em>do not</em> require any norm or whatever else. You can introduce them, if you want, but they are completely external to the prob... | Take $K_1$ to be a proper dense subspace and $K_2$ the translate of $K_1$ by a vector not in $K_1$.
| https://mathoverflow.net |
2,032,977 | [
"https://math.stackexchange.com/questions/2032977",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/389772/"
] | Let $T:X\to Y$ be linear operator.
I want to show that
$$
Tu = Tv \quad \text{for} \quad u,v \in Domain(T) \Rightarrow u=v
$$
if and only if
$$
Tu=0 \Rightarrow u=0.
$$
I saw this in a functional analysis book without any explain. But I'm a newbie so I could not prove this statement. Help me please.
| You put a tag <code>functional-analysis</code> for your question though, this is actually a general (very basic) fact in linear algebra (this could be the reason why you wouldn't see any explanation for the fact in a Functional Analysis textbook which assumes one knows basic linear algebra):
<blockquote>
Suppose $X$... | $(\implies)$ Note that $Tu=0=T(0)$. So by the hypothesis, $u=0$.
$(\impliedby)$ $Tu=Tv$ implies $T(u-v)=0$, so that $u-v=0$. Then $u=v$.
| https://math.stackexchange.com |
249,329 | [
"https://physics.stackexchange.com/questions/249329",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/114246/"
] | In constant accelaration and linear (1D) motion, we can show that relationship between velocity and position is quadratic (parabola) by<br>
We can write $v$ in the form of $v=v(x(t))$
\begin{equation}
a=\frac{dv}{dt} = \frac{dv}{dx} \cdot \frac{dx}{dt} \\
a=v\cdot\frac{dv}{dx}\\
\int a\text{ }dx = \int v\cdot\frac{dv}{... | If your textbook actually derives $(2)$ as the motion of a thrown object, throw it away.
The general trajectory of an object thrown from $(0,0)$ at angle $\theta$ is
$$ y(x) = x\tan(\theta) - \frac{gx^2}{2v^2}(1+\tan(\theta)^2)\tag{1}$$
and now you say you "impose $\Delta = 0$". Let's analyse that "imposing" a bit mor... | Equation (2) causing the confusion is just the bounding parabola: the limitation of points which could be hit (setting the angle of trajectory to 45° which gives the furthest limits of possible targets and also is the set of points which have only one angle to reach them (contrary to the false statement by Soren).
| https://physics.stackexchange.com |
250,589 | [
"https://dba.stackexchange.com/questions/250589",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/192628/"
] | I have been banging my head on this for a while...
I am using mysql to track results from a race - we have racers and categories (beginner, intermediate, Pro - for example) -- and each race has multiple timed segments, and a total time. The DB table looks as follows (not all columns shown)...
<pre><code>Name | C... | <code>CHAR(185)</code>, being VARCHAR data and using an 8-bit code page, can be a different character depending on the code page being used (which is determined by the collation of the current database when using the <code>CHAR()</code> function). In many code pages, including the common Windows-1252 (Latin1_General), ... | In case anyone wants to know - the issue was collation. When I wrote the question I didn't realize the #temp table I was using had a different collation than the default for the database I was working within. It was a simple solution and honestly something I shouldve thought of long before coming here with questions.
| https://dba.stackexchange.com |
225,475 | [
"https://dba.stackexchange.com/questions/225475",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/1754/"
] | I have a Powershell module that I've written and uploaded to my SQL Server at <code>C:\Program Files\WindowsPowerShell\Modules</code>.I have a SQL Agent job with a powershell step that calls the module. This all works and has been working.
However, I recently made a change to the way the Powershell module works. I u... | I figured it out. I had somehow renamed the folder from Get-ServerAudit to Get_ServerAudit, so powershell was treating the updated module as a new module.
Deleting the incorrectly named folders from the server, fixing the folder names, and copying over the updated files worked.
| <blockquote>
Do I need to tell SQL Server or Powershell to "refresh" the module somehow? How can I do that?
</blockquote>
You can use <code>import-module yourModuleName -Force</code>.
| https://dba.stackexchange.com |
166,312 | [
"https://physics.stackexchange.com/questions/166312",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/73685/"
] | I would like to know whether the speed of an electron depends on energy.
If yes then in a circuit when electrons flow out of a resistor the energy decreases by a considerable amount, leading to the charge per electron decrease and eventually to the decrease in current in a series circuit.
How is that possible?
| If you have current flowing one way through a resistor, then the electrons flow through the other way. Since current flows from the high voltage end of a resistor to the low voltage end, then the electrons come in at the low voltage end and come out at the high voltage end.
When electrons (which are negatively charge... | There may be a confusion between enery and power. While the current, which is the number of charges per second, and the energy of the ,electron do'nt change at the output of the resistor, the power does. Power is the amount of energy per unit time, and that does not affect the current which, again, is the amount of c... | https://physics.stackexchange.com |
203,644 | [
"https://softwareengineering.stackexchange.com/questions/203644",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/83269/"
] | On software company websites I visit the first time, I often open the "Contact us" page and try to submit the contact form with all fields empty. I am just curios if they validate the user input.
If it is just submitted or only validated poorly (e.g. only Javascript validation), I often hear myself thinking
<blockquo... | <h2>From UX point of view</h2>
<blockquote>
and try to submit the contact form with <strong>all</strong> fields empty<br>
[...]<br>
If they only want to enter a message and leave the <strong>other</strong> fields empty, why should I care?
</blockquote>
You and your friend are not talking about the same scenario... | Validation is important for two reasons:
<ol>
<li>If you don't have any validation, you may end up with your
database/inbox full of useless messages (Messages that have no
content or messages whose sender info is missing or makes no sense).</li>
<li>SQL injection. Not having any validation may compromise your
database... | https://softwareengineering.stackexchange.com |
364,643 | [
"https://mathoverflow.net/questions/364643",
"https://mathoverflow.net",
"https://mathoverflow.net/users/9833/"
] | Is there an isometric embedding of the modular surface <span class="math-container">$X(1)=PSL(2,\mathbb{Z})\backslash \,\mathbb{H}$</span> into the Euclidean 3-space? For all I know this may be an open problem but I am also curious if anyone studied
it numerically or maybe even made a physical model of it. (Which would... | There is no isometric immersion, let alone embedding, of <span class="math-container">$X(1)$</span> into Euclidean <span class="math-container">$3$</span>-space. Here is a sketch of an argument:
First, let <span class="math-container">$\mathbb{H}\subset\mathbb{C}$</span> be the upper half plane endowed with the standa... | Correction: The following idea doesn't work as stated, because (as Robert points out) the cusp and cones allow points where mean curvature is not defined.
If you could isometrically and smoothly embed the modular surface, you would smoothly and locally isometrically immerse the hyperbolic plane, which is impossible by ... | https://mathoverflow.net |
510,513 | [
"https://electronics.stackexchange.com/questions/510513",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/256735/"
] | <strong>Application</strong>
<ol>
<li>output - 100V 10mA
</li>
<li>Input - single cell lipo 3.7V 5000mAh
</li>
<li>overall efficiency > 85% required.
</li>
</ol>
I tested Texas instruments power bench.
Texas instruments power bench cannot generate circuit for 2.8V-4.2V input to 100V 10mA output
my idea is to use two... | <span class="math-container">$$\color{red}{\boxed{\text{You are focusing too much on efficiency as a parameter}}}$$</span>
Consider the stage 1 circuit that you say can produce 9 volts at 2 amps with 92% efficiency. Consider how much current the stage 1 circuit needs to supply stage 2. Stage 2 delivers 100 volts at 10 ... | Beat frequencies from different or slightly clocks. Can be dealt with through filtering with caps and ferrites or synching oscillators. This is also an issue in parallel converters as well.
| https://electronics.stackexchange.com |
282,696 | [
"https://physics.stackexchange.com/questions/282696",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/129194/"
] | According to Newton's third law of motion, if there is a beaker with 100g water, the normal force exerted by the bottom of the beaker would be equal to the force by the weight of the water in it..
What would happen if a wooden block is now half submerged into the beaker? Is the new normal force going to be the sum of ... | If the block is floating then the upthrust on the block due to the water is exactly equal in magnitude but opposite in direction to the weight of the block.
The block must therefore exert a force on the water equal but opposite to the upthrust.
That force causes the water in the container to rise and hence the pr... | The bottom of the beaker supports the whole weight of the water, plus the weight of anything floating in the water or resting entirely on the bottom (ie not touching the sides of the beaker). If you push down on the block, this is equivalent to making the block heavier.
Upthrust is an internal action-reaction force b... | https://physics.stackexchange.com |
3,886,331 | [
"https://math.stackexchange.com/questions/3886331",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/781945/"
] | I want to prove <span class="math-container">$x\delta'(x)=-\delta(x)$</span>. What I did was integrating the right side around 0 (since both sides are equals when <span class="math-container">$x \neq 0$</span> trivially):
<span class="math-container">$$\int_{-\varepsilon}^{\varepsilon}x\delta'(x)dx=\left[x\delta(x)\rig... | Answering your question requires that we answer the following: if we have a (generalized) function <span class="math-container">$d(x)$</span>, then how do we know that <span class="math-container">$d(x)$</span> is the delta-function? In other words, what is the definition of the delta function?
One definition is that c... | As in @BenGrossman's comments and answer, your computation does capture the essence of the issue, though your concern about pointwise values is heading off into trouble.
For that matter, although the manipulation of integrals (as in your heuristic or in BenGrossman's explanation) tells the story, it is also possible to... | https://math.stackexchange.com |
142,779 | [
"https://softwareengineering.stackexchange.com/questions/142779",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/9078/"
] | About a year and a half ago, I entered a workplace that claimed to do Agile development. What I learned was that this place has adopted several agile practices (such as daily standups, sprint plannings and sprint reviews) but none of the principles (just in time / just good enough mentality, exposing failure early, ric... | <blockquote>
I've been assured that I have complete buy-in from the devs and the business team [...] I have no access to the end users [...]
</blockquote>
One thing to be quite clear on is the difference between being <em>verbally</em> assured that you "have buy-in", on one hand, and on the other hand <em>the actual... | Agile isn't for everyone, it sounds like your business just likes saying agile because its the hottest buzzword. First of all it probably would have been a good idea to push for a brand new project or smaller maintenance projects to start making their process more like true agile methodologies. Trying to redesign a me... | https://softwareengineering.stackexchange.com |
6,327 | [
"https://dba.stackexchange.com/questions/6327",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/2319/"
] | I have 2 SQL Server 2008 instances installed on the same server. They have same table structures with same data. I have a stored procedure deployed on both of them. The stored procedure performs differently on them. It takes 5 seconds on one instance and 50 seconds on the other to execute the procedure. I think the pos... | Are the two instances indentically configured?
One thing to check is if the instances have the same memory allocation.
| Use <code>with(recompile)</code> on the stored procedures to ensure they are both starting from scratch when it comes to the execution plans.
| https://dba.stackexchange.com |
1,424,920 | [
"https://math.stackexchange.com/questions/1424920",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/268581/"
] | Suppose that chips for an integrated circuit are tested and that the probability that they are detected if they are defective is $.95$. The probability that they are declared sound if in fact they are sound is $.97$. If $5\%$ of the chips are faulty, what is the probability that a chip that is declared faulty is sound?... | Bayes' Rule states, when expanded with total probability, that:
$$P(A \mid B) = \frac{P(B \mid A)P(A)}{P(B \mid \neg A)P(\neg A) + P(B \mid A)P(A)}$$
Let's designate $A$ as the event that a chip is sound, and $B$ as the odds that it is declared faulty. Note that $P(B \mid A)$ is $1 - P(\neg B \mid A) = 1 - 0.97 = 0.0... | I will deliberately use a "solution" that is excessively sloppy, and does not use Bayes's Rule. For a formal argument, I prefer to use the <em>definition</em> of conditional probability.
Imagine testing a large number of chips, say $10000$. Then "roughly" $5\%$ of these, so about $500$, are defective, and the remaini... | https://math.stackexchange.com |
299,223 | [
"https://mathoverflow.net/questions/299223",
"https://mathoverflow.net",
"https://mathoverflow.net/users/-1/"
] | Suppose that an inverse limit of finite flat morphisms $X_k\to S$ of qcqs schemes, with affine transition maps, is $X\to S$, such that a closed fiber of $X\to S$ is finite.
Is $X\to S$ finite?
| No (in general).
Take $S = \mathrm{Spec}(A)$ and $X_k = \mathrm{Spec}(A[T]/(T^2))$, with affine transition maps given by $T \mapsto f T$ for some $f \in A$. The limit $X$ is the spectrum of $A \oplus A[f^{-1}] T$ (with $T^2 = 0$). Then $X \rightarrow S$ is an isomorphism (hence finite) over the closed subscheme $V(f)$ ... | A different counterexample is given by taking $S = \operatorname{Spec} \mathbb F_p \coprod \operatorname{Spec} \mathbb C$, and letting
$$X_k = \operatorname{Spec} \mathbb F_{p^k} \coprod \operatorname{Spec} \mathbb C.$$
Then $X = \operatorname{Spec} \bar {\mathbb F}_p \coprod \operatorname{Spec} \mathbb C$, which is no... | https://mathoverflow.net |
212,731 | [
"https://physics.stackexchange.com/questions/212731",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/95647/"
] | Imagine two concentric rings with different diameters. One is spinning within the other. There is a small gap between the outer diameter of the inner ring and the inner diameter of outer ring.
From the frame of reference of the outer ring, the inner ring is spinning and tends to expand radially outward, <em>closing</... | To solve a non homogeneous wave equation you need to use Green's function. The Green function of the inhomogeneous wave equation is defined as
$$
(\nabla^2-\frac{1}{c^2}\partial_t^2)G(x,x';t,t') =\delta(x-x')\delta(t-t')
$$
It means that $G$ is the solution of the wave equation for a Dirac source localized at the posit... | The source term $q$ just adds to the canonical solutions $A \cos(k(x-ct)+\phi)$ or $A \exp(\pm k(x-ct))$ a polynomial term of degree 2 in x and t (more precisely, $a x^2 +b t^2 +c x t +d x +e t +f$, with $2(a+b)=q$).
| https://physics.stackexchange.com |
83,081 | [
"https://security.stackexchange.com/questions/83081",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/69664/"
] | I've recently changed SpiderOak password on computer A. Because I have SpiderOak installed on computer B as well, I thought I will have to update the password on it so the application can connect to the server.
I was quite surprised when I found out the password updated itself automagically.
So I sent a question to S... | Disclaimer: I have never tried using spider oak so I'm only by going what they claim they do, what they told you they do and what the end result looks like.
Given that they claim to be storing your data encrypted and never being able to access it, I would assume the only thing they ever have access to is really the en... | Well, they can encrypt the new password by the old password or by some key exchanged between the machines prior the password change. This is the way they could do that.
However, I don't have the source code and don't surely know that.
| https://security.stackexchange.com |
456,323 | [
"https://physics.stackexchange.com/questions/456323",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/99217/"
] | It is known that - given in Sakurai, ch2.2, p83 - in Heisenberg's picture, for a Hamiltonian, <span class="math-container">$H$</span>, independent of time, the time evolution of any operator <span class="math-container">$\hat A$</span> is given by
<span class="math-container">$$i\hbar \frac{d \hat A }{d t} = [\hat A... | Your argument is completely correct.
Consider an operator <span class="math-container">$A$</span> which is not explicitly time-dependent (it is constant in the Schrödinger picture) and the time-evolution with a possibly time-dependent Hamiltonian <span class="math-container">$H(t)$</span>.
Then, the time-evolution is
... | If you plug in your time dependent <span class="math-container">$H(t)$</span> for <span class="math-container">$A(t)$</span> in the evolution equation, you get <span class="math-container">$\frac{dH(t)}{dt}=0$</span>, so the set of equations
<span class="math-container">$i\hbar \frac{d \hat A }{d t} = [\hat A (t_0), ... | https://physics.stackexchange.com |
452,230 | [
"https://electronics.stackexchange.com/questions/452230",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/228397/"
] | To calculate power loss using P=I^2R, we cannot use I=V/R, to find current and plug it into P=I^2R, instead we must use P=IV to find current, is there a reason why?
| There is one, I=V/R is only valid for resistors, so as a general definition of power it is better to go with P=IV which applies regardless of component.
a schematic or an explanation of the actual situation would get you better answers.
That said, defining power with P=IV is more general so it is better in most situ... | Sure. If you plug I = V/R into P = IV, you just get P = V^2 / R. You could calculate the value of I and then plug it in, or you can solve it symbolically and possibly save a few steps.
| https://electronics.stackexchange.com |
62,368 | [
"https://mathoverflow.net/questions/62368",
"https://mathoverflow.net",
"https://mathoverflow.net/users/10333/"
] | It is known that if $f:M\rightarrow N$ is a homotopy equivalent, then the the process of pullback gives a one-one correspondence between bundles over $N$ and $M$ up to isomorphism. Is the converse( that if $f$ gives a 1-1 correspondence between them, then $f$ is a homotopy equivalence)true? Or any counterexample?
By t... | If you are liberal enough as to what you consider to be "a bundle", then this is true. The reason is that the symmetric product
$$ G := SP^\infty(S^{n-1}) \simeq K(\mathbb{Z},n-1)$$
is a topological abelian group, and principal $G$-bundles are classified by maps to $BG \simeq K(\mathbb{Z}, n)$. Thus if $f : X \to Y$ in... | It all depends on which bundles we are considering. If we take topological vector bundles with structure group a Lie group $G$, then there aren't any non-trivial bundles over the 3-sphere: we have $\pi_3(BG)=\pi_2(G_0)=0$ where $G_0$ is the connected component of the unit of $G$.
| https://mathoverflow.net |
3,229,984 | [
"https://math.stackexchange.com/questions/3229984",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/675029/"
] | We know <span class="math-container">$e:= \lim_{n\to \infty}(1+\frac{1}{n})^n$</span>
We also know <span class="math-container">$x^n$</span> is continuous. Why is there a contradiction in the following?
<span class="math-container">$e=\lim_{n\to \infty}(1+\frac{1}{n})^n=(\lim_{n\to \infty}(1+\frac{1}{n}))^n=1$</span>... | You can't move a limit that depends on <span class="math-container">$n$</span> "inside" the function if the outside function depends on <span class="math-container">$n$</span>. For example, it is clearly true that
<span class="math-container">$$\lim_{n \to \infty} 2^n= \infty .$$</span>
However, if you move the limit... | The actual problem is you can't write <span class="math-container">$(\lim_{n\to\infty}f(n))^n$</span>, or anything else that uses <span class="math-container">$n$</span> outside the limit, because it's a dummy variable that exists only inside the limit. The role of <span class="math-container">$\infty$</span> is irrele... | https://math.stackexchange.com |
62,608 | [
"https://mathoverflow.net/questions/62608",
"https://mathoverflow.net",
"https://mathoverflow.net/users/14595/"
] | Let $1 \to N \to G \to H \to 1$ be a short exact sequence of topological groups. Such an exact sequence is said to be topologically split if $G$ is $N \times H$ as a
topological space.
Can someone give me an example of a topologically split short exact sequence of non-discrete connected topological groups. Of course I... | I think something like the real $ax+b$ group (a.k.a. the affine group of ${\mathbb R}$) ought to do the trick.
The following is not the full $ax+b$ group but may be easier to handle here. Take
$$ G = \left\{\left( \matrix{ a & b \\ 0 & 1 } \right) \colon a >0, b \in {\mathbb R} \right\} $$
and take $N$ to ... | Let me elaborate on the example of the 3-dimensional Heisenberg group, pointed out by Mark, which indeed provides the desired example. It is the group
$$G=\{\left(
\begin{array}{ccc}
1 & x & z \\
0 & 1 & y \\
0 & 0 & 1
\end{array} \right):x,y,z\in\mathbb{R}\}$$
Let $N$ be its centre:
$$N=\{\lef... | https://mathoverflow.net |
324,332 | [
"https://softwareengineering.stackexchange.com/questions/324332",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/197872/"
] | Imagine we have a administrative system that is designed to be as fast and lean as possible, without too much fancy CSS or JS. The UE is not that great, but still it is pleasing on the eyes and gets the job done.
But my question is, is in such situation AJAX and the added overhead in form of JS worth it to save few HT... | I understand your concern that you want to keep JS code to bare minimum and rely on HTML and plain HTTP for all server calls.
If your purpose is solved by doing so you can well keep out of AJAX.
But it will be wrong to say that AJAX is useful only in content rich environments.
Asynchronous requests not only provide a... | Yes it is. AJAX requests the HTTP too, but what's the best you can do it without reloading page. In example a system where you need to delete single users one-by-one it's more effective to delete them without reloading page, because you don't have to wait until page is loaded when choosing more users to delete. AJAX is... | https://softwareengineering.stackexchange.com |
234,376 | [
"https://physics.stackexchange.com/questions/234376",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/72921/"
] | When we short-circuit a voltage source, the current will be very high. The voltage across the wire is <span class="math-container">$0\rm\ V$</span>. If we apply Kirchhoff voltage law, also the voltage across the voltage source is <span class="math-container">$0\rm\ V$</span>. How can it be <span class="math-container">... | Even if you put a superconductor across the terminals of a voltage source the current would be finite as all real voltage sources have a resistance. A circuit with a voltage source with no resistance does not exist.
| The fundamental problem is that the Ohm's law is a simple mathematical approximation, neglecting the V-A characteristic of a real source, resistance of wires, or even nonlinear physical response of materials under extreme conditions.
Using this approximation outside of its scope leads to a "0/0" problem, which is obv... | https://physics.stackexchange.com |
2,237,097 | [
"https://math.stackexchange.com/questions/2237097",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/429401/"
] | Let $A =
\begin{pmatrix}
e^{2x} & -1 \\
0 & e^{2x}-1 \\
\end{pmatrix}
$. Compute $A^7$.
I've tried the obvious way of multiplying $A$ with $A$, then $A^2$ with $A^2$, but I arrived at a messy result in the top right member of the matrix. Is there a general form to be noticed ... | Let $P=\pmatrix{0&1\\ 0&1}$. Note that $P^k=P$ for every $k\ge1$. Therefore
\begin{align}
A^7
&=(e^{2x}I-P)^7\\
&=\sum_{k=0}^7\binom{7}{k}e^{2x(7-k)}(-1)^kP^k\\
&=e^{14x}I+\sum_{k=1}^7\binom{7}{k}e^{2x(7-k)}(-1)^kP^k\\
&=e^{14x}I+\sum_{k=1}^7\binom{7}{k}e^{2x(7-k)}(-1)^kP\\
&=e^{14x}(I-P)+\s... | Let $A=\pmatrix{a&b\\0&d}$ instead, to avoid clutter. It's plain then that
$$A^n=\pmatrix{a^n&b_n\\0&d^n}$$
for some $b_n$. Then $b_1=b$ and in general $b_{n+1}=ab_n+b d^n$.
So $b_2=(a+d)b$, $b_3=(a^2+ad+d^2)b$, $b_4=(a^3+a^2d+ad^2+d^3)b$ etc. A pattern seems to emerge.
Is
$$b_n=(a^{n-1}+a^{n-2}d+\cdots... | https://math.stackexchange.com |
78,351 | [
"https://electronics.stackexchange.com/questions/78351",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/27251/"
] | I'm new to this site and I'm pretty "noobish" to electrical engineering coming from a software engineering background I was hoping someone could help me understand this design a bit. I've highlighted two part of the diagram that obviously aren't gates.
I'd like some help understanding what it is and how it could be i... | It's a Multiplexer.
Inputs A,B,C select what input goes to output.
Example: ABC = 011 (binary) = 3 (decimal) in that case D3 will be set as output.
| It's a multiplexer. It selects which function the ALU outputs, by selecting which set of gates gets routed to the output. If OP[2:0] == 0, for example, then <code>OUT = A xor B</code>. If OP == 3, then <code>OUT = A + B + carryin</code>.
| https://electronics.stackexchange.com |
368,197 | [
"https://softwareengineering.stackexchange.com/questions/368197",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/199068/"
] | When I have a class with multiple constructors where one constructor calls another one (constructor chaining), which constructor should be the one that all the other constructors call eventually?
Here's an example where the "all args" constructor calls the "no args" constructor:
<pre><code>class Goblin {
// alway... | I would advocate for preferring the second approach, as this allows you to declare both members as <code>final</code> and make the class formally immutable.
| In general, it doesn't matter. The important thing is to chain the constructors so you're not repeating code. But if the no-arg one calls the one with arguments, or the one with args calls the no-arg one, they both accomplish the same thing - creating a (valid) object with no code repetition.
| https://softwareengineering.stackexchange.com |
3,158,841 | [
"https://math.stackexchange.com/questions/3158841",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/612702/"
] | Is there an identity for <span class="math-container">$\frac{K'(k)}{K(k)}=?$</span> where <span class="math-container">$K(k)=\int_0^{\frac{\pi}{2}}\frac{1}{\sqrt{1-k^2\sin^2(x)}}dx=\int_0^1\frac{1}{\sqrt{(1-t^2)(1-k^2t^2)}}dt$</span> is the Complete Elliptic Integral of the First Kind and <span class="math-container">$... | Let <span class="math-container">$W_k$</span> be the event of drawing a white marble on the <span class="math-container">$k$</span>-th draw, and <span class="math-container">$B_k$</span> the complementary event.
So your solution should look somewhat like:
(a) <span class="math-container">$$\begin{align}\mathsf P(W_1\... | Let <span class="math-container">$P(W) = {4\over13}$</span> be the prob that the first draw is white
Then there will be 3 whites and 11 blacks
So if <span class="math-container">$P(WW)$</span> is the probability that both first and second draws are white , then <span class="math-container">$P(WW)= \frac 4{13}\times \... | https://math.stackexchange.com |
348,932 | [
"https://stats.stackexchange.com/questions/348932",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/165909/"
] | In univariate regression, the standardized coefficient is equal to the Pearson correlation coefficient. When the two variables are ranked variables,
Spearman correlation would be appropriate. Is it possible to derive Spearman correlation coefficient from a univariate regression? It may be useful under the condition wh... | Here is an example using data on gallons per 1000 miles and weight in pounds for 22 foreign cars (meaning, cars made outside the United States) from Stata's <code>auto</code> data (and before that from Chambers, J.M., W.S. Cleveland, B. Kleiner and P.A. Tukey. 1983. <em>Graphical Methods for Data Analysis.</em> Belmon... | You cannot derive Spearman coefficients from linear regression (on the unranked variables). The Spearman correlation summarizes the monotonic trend. They are related but it's not a bijective relation. At best, you only if one is non-zero, the other is non-zero.
| https://stats.stackexchange.com |
338,959 | [
"https://mathoverflow.net/questions/338959",
"https://mathoverflow.net",
"https://mathoverflow.net/users/123432/"
] | If <span class="math-container">$X$</span> is a based connected topological space, it is well-known what the homology of <span class="math-container">$\Omega\Sigma X$</span> is: according to the Bott-Samelson theorem, it is a tensor algebra over reduced homology of <span class="math-container">$X$</span>. (Some assumpt... | <span class="math-container">$\newcommand{\E}{\mathbf{E}} \newcommand{\co}{\mathcal{O}} \newcommand{\free}{\mathrm{Free}} \newcommand{\H}{\mathrm{H}}$</span>Here's one way of seeing the Bott-Samelson theorem. The James splitting gives an equivalence
<span class="math-container">$$\Sigma \Omega \Sigma X \simeq \bigvee_{... | Your space <span class="math-container">$D_1(X)$</span> is equivalent to Ioan James' space <span class="math-container">$JX$</span> investigated in the 1950's. It is quite easy to directly show that the homology of this is the tensor algebra on the reduced homology of <span class="math-container">$X$</span>, in parall... | https://mathoverflow.net |
207,910 | [
"https://math.stackexchange.com/questions/207910",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/34083/"
] | Prove that if $\lim_{n \to \infty}z_{n}=A$ then:
$$\lim_{n \to \infty}\frac{z_{1}+z_{2}+\cdots + z_{n}}{n}=A$$
I was thinking spliting it in: $$(z_{1}+z_{2}+\cdots+z_{N-1})+(z_{N}+z_{N+1}+\cdots+z_{n})$$
where $N$ is value of $n$ for which $|A-z_{n}|<\epsilon$
then taking the limit of this sum devided by $n$ , and ... | It seems like Homework problem, hence I'll just give hint:
$$\frac{z_1+z_2+\cdots +z_n}{n}-A=\frac {(z_1-A)+(z_2-A)+\cdots +(z_n-A)}{n}$$
Now use the defn of limit that for every $\epsilon > 0$ there exists $N_0 \in \mathbb N$ such that $|z_m-A| < \epsilon \ \forall m \geq N_0$
Also remember triangle inequality ... | Let <span class="math-container">$\epsilon >0$</span>
We have that <span class="math-container">$\lim_{n \rightarrow \infty}z_n=A$</span> thus <span class="math-container">$\exists n_1 \in \mathbb{N}$</span> such that <span class="math-container">$|z_n-A|< \epsilon, \forall n \geqslant n_1$</span>
<span class=... | https://math.stackexchange.com |
784,245 | [
"https://math.stackexchange.com/questions/784245",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/115780/"
] | I have spent well over an hour trying to solve this equation:
$$\int\cos^4{x}\sin^3{x}\, dx$$
I have tried substituting u as $\cos{x}$, $\sin{x}$, $\cos^4{x}$, and $sin^3{x}$ to no avail. How can I solve this?
| $$
\int \cos^4 x\sin^3 x\mathrm{d}x=-\int\cos^4x\sin^2x\mathrm{d}(\cos x)=-\int\cos^4x(1-\cos^2x)\mathrm{d}(\cos x)\\
=-\int(\cos^4x-\cos^6x)\mathrm{d}(\cos x)=-\int\cos^4x\mathrm{d}(\cos x)+\int\cos^6x\mathrm{d}(\cos x)\\
=-\frac{1}{5}\cos^5x+\frac{1}{7}\cos^7x+C,\ C\ \text{is an arbitrary constant}
$$
| Write $ \sin^3 x = \sin x (1-\cos^2 x)$
| https://math.stackexchange.com |
212,241 | [
"https://physics.stackexchange.com/questions/212241",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/58717/"
] | Louis de Broglie suggested that for microparticles like electrons, wave-like properties can be applied in order to explain some phenomena. Schrodinger wrote down an equation, a wave equation, describing these waves. What I do not understand is why is Schrodinger's contribution so important; if the concept of wave-like ... | There is a big difference between a wave equation and a wavefunction... What de Broglie postulated was that the probability distribution of various observable quantities of a particle can be described by a wavefunction (sometimes called a wave packet) at <strong>any fixed time</strong>. What Schrodinger did was to post... | Erwin Schrodinger developed wave mechanics on the basis of de Broglie's hypothesis of wave-particle duality. The concepts which de Broglie introduced to relate dynamical variables connected with corpuscular motion(e.g. momentum) with characteristics of the waves(e.g. wavelength) were extended by Schrodinger in a more g... | https://physics.stackexchange.com |
67,255 | [
"https://electronics.stackexchange.com/questions/67255",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/10345/"
] | Hello I have made Spartan 6 board and now I'm trying to get it work, I have successfully managed to get programming of SPI flash working so I can upload bitstreams, but I have problem that some of IO pins doesn't stay at their desired state.
For example I have 4 IO used to control relays of attenuators (used in oscill... | I finally found that problem was that I have been loading the same design over and over.. So I thought that I have design that light the led but there was none.. Now it works as expected. because I thought that *.MCS files are generated only once not that I have to generate MCS file from BIT file every time I change bi... | So I'm assuming commandData is some SPI register from a micro-controller? If this is a new board (and not a proven development board hooked up to some other circuitry), I would start by doing some sanity checks. For example, do you have spare pins? Can you combinatorically (that is, outside of the state machine) do so... | https://electronics.stackexchange.com |
111,582 | [
"https://mathoverflow.net/questions/111582",
"https://mathoverflow.net",
"https://mathoverflow.net/users/6936/"
] | I'll begin with the question, which is intrinsically interesting:
<blockquote>
Let <em>M</em> be a manifold with some submanifold <em>Y</em>. Suppose that $W \rightarrow M$ is a smooth, proper map. Does there exist another map $W \rightarrow M$ homotopic to the original that is ALSO proper and transverse to the subm... | Regarding the coboundary map in complex cobordism, I think that this was done by Dold in "Geometric Cobordism and the Fixed Point Transfer" (at least for oriented cobordism) in 2.10.
| The comments explain how to prove the fact.
If you want to put a formal wrapping around it, consider the strong (Whitney) $C^\infty$ topology on the space of maps $W\to M$. The strong $C^0$ topology on $C(M,\mathbb R)$ can be defined as follows: for every function $h:M\to\mathbb R$ which is positive and locally bounde... | https://mathoverflow.net |
88,999 | [
"https://stats.stackexchange.com/questions/88999",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/36564/"
] | I wonder how I can modify the K-means algorithm so that the cluster volumes are not equal to each other. The K-means objective is to minimize within cluster sum of squares $\sum_{i=1}^{p} {\parallel \mathit{X}_i-\mathit{L}_{\mathit{Z}_i} \parallel}_2^2$, and this objective assumes that all cluster variances are the sam... | In one medical research paper, Proitsi et al. (2009) write:
<blockquote>
"The WLSMV is a robust estimator which does not assume normally
distributed variables and provides the best option for modelling
categorical or ordered data (Brown, 2006)".
</blockquote>
For your convenience, I'm including the cited refere... | The most obvious reason for choosing one over the other would be the kind of fit indices you need. The WLSMV will give you CFI, TLI and RMSEA, which will help you evaluate the fit of a given model. If you need to compare non-nested models, you would need AIC and/or BIC, which aren't available with WLSMV and categorical... | https://stats.stackexchange.com |
401,278 | [
"https://mathoverflow.net/questions/401278",
"https://mathoverflow.net",
"https://mathoverflow.net/users/333818/"
] | If I start with a, say, 3-CW complex <span class="math-container">$X$</span> which can be embedded in <span class="math-container">$\mathbb{R}^5$</span>, I can get a neighbourhood <span class="math-container">$U$</span> of <span class="math-container">$X$</span> which has the same homotopy type of <span class="math-con... | Take <span class="math-container">$X=S^3$</span>. Then no closed manifold of dimension at least 6 has the same homotopy type.
| More generally, suppose <span class="math-container">$n \le m$</span> are non-negative integers,
<span class="math-container">$X$</span> is a CW complex of dimension <span class="math-container">$\le n$</span>, <span class="math-container">$M$</span> is a non-empty, closed <span class="math-container">$m$</span>-manifo... | https://mathoverflow.net |
17,063 | [
"https://quant.stackexchange.com/questions/17063",
"https://quant.stackexchange.com",
"https://quant.stackexchange.com/users/15700/"
] | I have a conceptual question that I haven't managed to grasp yet and is most likely a econometrics 101 question by here it goes:
If we estimate a GARCH model for a time series, how do we then use this in my model for the returns? For example; I have the return data of an index. I know that I have volatility clustering... | You first fit a ARIMA model to the returns data and then a GARCH model to the residuals.
| Any ARCH type model always requires an additional model for the mean of the time series. If nothing is said about the mean model, then usually is simply a time average plus residual. So, if $y_t$ is your stationary time series, the mean model would be
$$ y_t = \bar{y} + \epsilon_t $$
where $\bar{y}$ is the average valu... | https://quant.stackexchange.com |
90,332 | [
"https://stats.stackexchange.com/questions/90332",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/11609/"
] | Here's my understanding of the kernel trick. The motivation is to find a linear separator in a higher dimensional space than what you have (because the data are not currently linearly separable.) You take the dot product, and then apply the transformation to the result, saving you the time of applying the transformat... | You were very very nearly there and got caught by a subtle issue in working with matrices in R. I worked through from your <code>final_data</code> and got the correct results independently. Then I had a closer look at your code. To cut a long story short, where you wrote
<pre><code>row_orig_data = t(t(feat_vec[1,]) %*... | I think you have the right idea but stumbled over a nasty feature of R. Here again the relevant code piece as you've stated it:
<pre><code>trans_data = final_data
trans_data[,2] = 0
row_orig_data = t(t(feat_vec[1,]) %*% t(trans_data))
plot(row_orig_data, asp=T, pch=16)
</code></pre>
Essentially <code>final_data</code... | https://stats.stackexchange.com |
114,458 | [
"https://mathoverflow.net/questions/114458",
"https://mathoverflow.net",
"https://mathoverflow.net/users/29401/"
] | I have heard that derived category of coherent sheaves $\mathrm{Coh}(X)$ on any Fano varieties $X$ may be realized as derived category $\mathrm{Coh}(\mathrm{Rep}(Q,W))$ of representation of quiver $Q$ with relations $W$. I wonder for what kind of varieties their derived category of sheaves are realized by quiver. For e... | Any variety with a strong exceptional collection that generates the derived category of coherent sheaves will work. This goes back in some form to Bondal and is a consequence of Rickard's derived Morita equivalence. (This is sufficient, but not necessary. For non-compact varieties, for example, you can get derived equi... | The question is the mother of all confusions. For the starters, a quintic threefold is not Fano but rather Calabi-Yau, and there you are doomed as Aaron has explained.
In general, a triangulated category may have three types of nice gadgets:
<ol>
<li>strong exceptional collection,</li>
<li>exceptional collection,</li... | https://mathoverflow.net |
262,741 | [
"https://mathoverflow.net/questions/262741",
"https://mathoverflow.net",
"https://mathoverflow.net/users/105141/"
] | Let $\lambda$ be a partition. Suppose that $\lambda$ is both $2$- and $3$-decomposable, in the sense that $\lambda$ admits a total decomposition by both $2$-rim hooks (aka dominos) and $3$-rim hooks. Equivalently, assume that the $2$-core and $3$-core of $\lambda$ is zero. Then what can be said about the $6$-core of $\... | Let me comment a bit further on the fact that there are other 6-cores with trivial 2 and 3-core, in fact infinitely many of them. The fundamental paper of Garvan, Stanton, Kim, "Cranks and T-cores", gives a bijection between t-cores and integer tuples $(n_0,n_1,\dots,n_{t-1})$ which satisfy $\sum_{i=0}^{t-1}n_i=0$. Und... | I believe a partition of 12 answers your 3rd question in the negative: Consider (6,2,2,2). Each hook length is in the set $\{1,2,3,4,8,9\}$, so it is 6-core. One can check that the partition admits total decompositions into both 2- and 3-rim hooks.
No answers for your more interesting questions. Initially I thought... | https://mathoverflow.net |
4,339,381 | [
"https://math.stackexchange.com/questions/4339381",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/981951/"
] | Let <span class="math-container">$\mathcal{A}$</span> be a <span class="math-container">$C^\ast$</span>-algebra finitely generated by <span class="math-container">$n$</span> elements <span class="math-container">$\{a_1,\dots,a_n\}$</span>.
Elements in the center <span class="math-container">$Z(\mathcal{A})$</span> comm... | Let <span class="math-container">$a \in \mathcal A$</span> be an element commuting with all the generators. The centralizer of <span class="math-container">$a$</span> is defined as :
<span class="math-container">$$Z_\mathcal A(a) = \{b\in A | ab = ba\}$$</span>
It a sub-<span class="math-container">$C^*$</span>-algebra... | I have accepted another answer while I was writing this answer. I am not sure about this polynomial *-algebra <span class="math-container">$B$</span> being dense in <span class="math-container">$\mathcal{A}$</span>.
The generators generate a polynomial *-algebra <span class="math-container">$B$</span> and if <span clas... | https://math.stackexchange.com |
45,926 | [
"https://quant.stackexchange.com/questions/45926",
"https://quant.stackexchange.com",
"https://quant.stackexchange.com/users/41282/"
] | When calculating a portfolios total exposure, should the value of the cash accounts be included?
My high level view on exposure is that it should be related to the possibility of loss, usually as a result of exposure to financial markets.
This doesn't match with bank accounts as I see it, and so I would not want to i... | I assume you are referring to the calculation of Gross Exposure and Net Exposure, which are commonly used by Hedge Funds.
These funds typically have long and/or short positions in stocks (hence they are called Long Short Funds); these positions vary over time (and can also be quite different among different funds). Th... | I am adding on to @noob2 answer -- which, is correct if expressing exposures as a value of the fund's base currency. E.g., Fund XYZ has $1M of short equity exposure.
<blockquote>
When calculating a portfolios total exposure, should the value of the
cash accounts be included?
</blockquote>
For exposures expressed ... | https://quant.stackexchange.com |
44,844 | [
"https://dba.stackexchange.com/questions/44844",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/6096/"
] | I am testing the AlwaysOn feature of SQL Server 2012. I have 2 servers set up and can successfully create availability groups and fail them over between servers. However, any databases that DO NOT belong to an availability group are stuck in a status of "Restoring" on the secondary server. I have started from scratch s... | I have a half-answer at least. My first attempt at creating an Availability Group consisted of every database. I later decided to only try a few databases in a group. So I deleted the databases on the secondary after removing them from the AG. Subsequent attempts to create availability groups with a limited set of data... | How did you setup your Availability Group? It sounds like what happened is you blanketed the backups and restores from the primary replica server to the secondary replica server.
In other words, you did a:
<pre><code>backup database <DatabaseName>
to disk .... <so on and so forth>
</code></pre>
to all d... | https://dba.stackexchange.com |
39,147 | [
"https://dba.stackexchange.com/questions/39147",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/18257/"
] | I have a database that is close to filling the hard drive that it lives on. I'd like to expand the database on to another hard drive to deal with this.
I see there's a Files option in the database properties under SSMS that I could add to but I don't really want to go adding files without knowing what comes next. ... | <blockquote>
Do I need to add a new entry to Filegroups and then add to Files?
</blockquote>
You can do one of two things here:
<ol>
<li>Add a new filegroup and at least one new data file</li>
<li>Add a new data file to an existing filegroup (PRIMARY in this case)</li>
</ol>
<blockquote>
Is the PRIMARY type only... | In addition to Thomas's answer, you could do it simply using T-SQL.
This sample code adds a new file to the Primary file group. In your case I don't really see the need for a new file group. But see Thomas's comment on that.
<pre><code>USE [master]
GO
ALTER DATABASE [Test]
ADD FILE (
NAME = N'NewDataFile',
FI... | https://dba.stackexchange.com |
36,418 | [
"https://security.stackexchange.com/questions/36418",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/26352/"
] | So I completely understand that routers and local networks need to be kept locked down, etc. What real security threats can come about from an attacker who has remotely accessed (telnet or web gui) your home router?
Out of personal interest, I have set up a few test scenarios on my personal network where an attacker m... | The impact will always be severe, but a lot of the specifics depend on the individual router. If the device runs embedded Linux (e.g. DD-WRT) it may be possible to remotely enable SSH and add a public key to <code>auth_keys</code>, giving full remote shell access.
Without SSH, I can see the following issues:
<ul>
<li... | Your router processes all your traffic, so someone with control of your router could see everything you do by acting as a man in the middle. They could direct you to any site they choose by NATing the destination. They could also use NAT to open a direct connection to your computer, allowing them to attack it directly.... | https://security.stackexchange.com |
1,008,623 | [
"https://math.stackexchange.com/questions/1008623",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/190309/"
] | Im working on practice problems that the instructor gave us yesterday and Im stuck with this question..
the question is: if $f\circ g $ is one to one, then is $g$ one to one?
Im not sure how to solve this problem.. Detailed explanation will be very much appreciated
Thank you
| if $f\circ g$ is one-one, this means g is one-one, because if $g(x_1)=g(x_2)\implies f(g(x_1))=f(g(x_2))$ which makes $f\circ g$ many-one.
| Suppose $x\neq y$. Then, $f(g(x))\neq f(g(y))$ preventing the possibility that $g(x)=g(y)$. So $g$ must also be one-to-one.
| https://math.stackexchange.com |
180,580 | [
"https://electronics.stackexchange.com/questions/180580",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/51680/"
] | What is the typical resistance between two points on a "typical" PCB? Let's say the points are 1mm apart and let's assume a normal office environment.
I've noticed that resistors come in many values, but resistors larger than 10 megaohm are rare or hard to find.
I suppose that a circuit with a 10 gigaohm resistor wou... | A clean PTFE circuit board could be as high as 10^17 ohms between a couple small pads spaced by a mm or two. If the board has contamination (especially ionic contamination) it could be much less. A clean FR board should be > 10G ohms. If you really need high impedance for fA measurements, PTFE standoffs or air connecti... | The resistance between any two <i>points</i> is infinite.
In the real world, you can't make a true point contact. It will always have some diameter or other finite dimensions. Those dimensions relative to the separation distance are required to determine the resistance between, given the resistivity of the material.... | https://electronics.stackexchange.com |
51,729 | [
"https://dba.stackexchange.com/questions/51729",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/-1/"
] | The software company I work for is planning to migrating our infrastructure into the cloud. Our current focus is to find the best database replication method.
Current Servers:
SQL Server 2008 SE - Located in NY (In house - Master)
SQL Server 2012 SE - Located in Chicago (Rackspace - Slave)
We have been considering ... | In my opinion, log shipping has those advantages:
<ol>
<li>I understand the direction is only one-way (master to slave). Replication is a complex solution better suited to two-way data replication or replication to multiple sources.</li>
<li>Log shipping doesn't need a special design of the database (e.g. primary keys... | <strong>Log Shipping</strong> essentially involves three jobs. The first job backs up the log on the primary server and stores those backups in a local folder. The second job copies those files across the network to the secondary server. The third jobs restores those backups using the WITH STANDBY option. Log Shipping ... | https://dba.stackexchange.com |
355,170 | [
"https://softwareengineering.stackexchange.com/questions/355170",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/263132/"
] | An interviewer asked me this question:
<blockquote>
Given a function f(ar[]) where ar[] is an array of integers, this
functions claims to sort ar[] and returns it's sorted version ars[].
Determine if this function works correctly.
</blockquote>
I approached this question as:
<blockquote>
<ol>
<li>First che... | As already mentioned by @Dipstick, step 3 can fail if there are duplicates in the input array. To resolve this and improve the time complexity, one can use a dictionary with the array elements as keys and their number of occurrence as values. Such a dictionary can be created from the sorted and the unsorted array as we... | Your method is only testing that the original and sorted arrays contain the same values, not that they contain the same number of each value; e.g. 1112 would pass for 1221
In step 3 you could, for example, mark that a particular value in the sorted array has already been matched (removing from the array would be too t... | https://softwareengineering.stackexchange.com |
2,927,035 | [
"https://math.stackexchange.com/questions/2927035",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/595918/"
] | <blockquote>
Two complex numbers <span class="math-container">$z_{1}$</span> and <span class="math-container">$z_{2}$</span> are taken such that
<span class="math-container">$|z_{1} + z_{2}| = |z_{1} - z_{2}|$</span> and <span class="math-container">$z_{2}$</span> is not <span class="math-container">$0$</span>.
... | Hint: <span class="math-container">$$|z_1 + z_2| = |z_1 - z_2| \implies \left|\frac{z_1}{z_2}+1\right| = \left|\frac{z_1}{z_2}-1\right| \tag{1}$$</span>
if <span class="math-container">$z_2 \neq 0$</span>. In other words, <span class="math-container">$z_1/z_2$</span> is equidistant from <span class="math-container">$1$... | We have that
<span class="math-container">$$|z_1 + z_2| = |z_1 - z_2| \iff \left|\frac{z_1}{z_2}+1\right| = \left|\frac{z_1}{z_2}-1\right|\iff \left|\frac{z_1}{z_2}+1\right|^2 = \left|\frac{z_1}{z_2}-1\right|^2$$</span>
and by <span class="math-container">$w=\frac{z_1}{z_2}$</span>
<span class="math-container">$$|w+... | https://math.stackexchange.com |
378,996 | [
"https://physics.stackexchange.com/questions/378996",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/152620/"
] | In the film Passenger the spaceship was flying at half light speed so I was thinking was it even possible that like chris pratt one can go out of such fast moving ship with just the rope tied not even dragged by it.I know its not possible for half light speed in first place but just a thought.
| The speed is irrelevant. Astronauts do space walks around spaceships and space stations regularly. In the reference frame of the ship, the astronauts have very small velocities. The speed of the ship itself is only relative to some other reference frame.
| As others have pointed out, speed itself is irrelevant. Astronauts would not notice their speed in any way; there will be no drag on the rope.
However, there is another way in which speed is very relevant. As the astronauts are moving at $0.5c$ it means that all other matter they encounter will strike them with that s... | https://physics.stackexchange.com |
42,584 | [
"https://electronics.stackexchange.com/questions/42584",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/13698/"
] | I'm trying to send ASCII characters from Arduino UNO to a computer serial port. I'm using a cable with a male COM connector, attached to the computer's serial port, and three wires (TX, RX and Ground) on the Arduino side.
I used pins 12, 13 and Gnd as shown in the picture:
<img src="https://i.stack.imgur.com/evEA6.png... | The Arduino UART produces TTL level signals, that is 5V for high and 0V for low. A PC's RS232 port expects full RS232 voltages which can be -9V to +9V and are inverted.
Either use a TTL level serial adapter (such as those from FTDI) to interface to the PC. Or use a level converter like the MAX232.
| Like Toby says you need an EIA-232 (the name RS-232 is obsolete) transceiver. The Arduino's UART will output +5 V when idle and for a logical "1", and 0 V for a logical "0". EIA-232 works with inverted levels, so the +5 V becomes typically -12 V, and the 0 V becomes +12 V.
If you connect the UART directly to the PC's... | https://electronics.stackexchange.com |
269,289 | [
"https://physics.stackexchange.com/questions/269289",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/124212/"
] | I've been thinking about infrared radiation and noticing more and more how the human skin seems actually pretty sensitive to it.
You can easily feel a bonfire from several meters away, far away from where any convection would heat your skin.
When you open the hood of your car you can feel the heat from the engine eve... | I don't see how the existence of insulanium violates any of the laws of thermodynamics :
The 1st Law is a statement that energy is conserved. But there is no suggestion that energy is being created or destroyed here.
The 2nd Law states that the entropy of an isolated system only increases, never decreases. This is ... | I dont think it is possible to make anything 100% reflective although we can get arbitrarily close. The reason may be explained by tunneling by photons. Also,the entropy of an isolated piece of insulanium must increase with time. I think you can see now why such a thing is very very unlikely.
| https://physics.stackexchange.com |
276,522 | [
"https://physics.stackexchange.com/questions/276522",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/127740/"
] | The reason why you have to tune differently the atomic clocks in GPS is because the GPS is higher or because there is less gravity there, or both? In other words in a constant gravitational field which doesn't differ with height, will time dilation still occur?
They say that the reason why people on the first floor ag... | The time dilation is due to a difference in the gravitational potential energy, so it is due to the difference in height. It doesn't matter whether the strength of the gravitational field varies, or how much it varies, all that matters is that the two observers comparing their clocks have a different gravitational pote... | Quite simply:
1) you know from special relativity that accelerated frames experiences a time dilation effect (time is slower for them), and that the more accelerated, the slower the time,
2) strong equivalence principle tells you that standing still on earth or at a constant height with respect to the ground means yo... | https://physics.stackexchange.com |
438,492 | [
"https://electronics.stackexchange.com/questions/438492",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/37683/"
] | I have a boost converter that converts 1.5v to 3v, and I have a ESP32 that takes a USB input of 5V and uses a regulator to convert it down to 3v.
If I provide 3v to the 5v input that goes via the regulator, is it the same as skipping the regulator and connecting it directly.
| Attempting to pass through 3V through the 5V to 3V regulator may result in erratic behavior by the regulator as it attempts to regulate below its drop out voltage, and possibly a lower voltage at the output. The regulator will also take some power for itself. It's not a straight forward option. You are better off bypas... | No, giving 3 from a source that has less loss than the build in converter will save you some power.
As Christian B states you will not use a buck converter to convert from 1.5 to 3v
| https://electronics.stackexchange.com |
3,332,707 | [
"https://math.stackexchange.com/questions/3332707",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/287593/"
] | Let <span class="math-container">$u = (u_1, u_2)$</span> and <span class="math-container">$x=(x,y)$</span> a rotation of u by an angle θ. Then <span class="math-container">$\left\lVert u \right\rVert = \left\lVert x \right\rVert$</span>
We know:
<span class="math-container">$$cosθ = {{u \cdot x}\over \left\lVert u \ri... | Suppose that <span class="math-container">$u_1,$</span> <span class="math-container">$u_2,$</span> and <span class="math-container">$\theta$</span> are given.
First solve for <span class="math-container">$y$</span> in Equation <span class="math-container">$(2)$</span>:
<span class="math-container">$$ y = \frac1{u_2}(u_... | Using complex numbers :
<span class="math-container">$$\begin{array}{lcl}
x + i y & = & (u_1 + i u_2) e^{i\theta} \\[3mm]
& = & (u_1 + i u_2)(\cos \theta + i \sin \theta) \\[3mm]
& = & u_1 \cos \theta - u_2 \sin \theta + i (u_1 \sin \theta + u_2 \cos \theta)
\end{array}$$</span>
Hence :
<span cl... | https://math.stackexchange.com |
502,673 | [
"https://physics.stackexchange.com/questions/502673",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/224051/"
] | There are three sources of heat in the Earth's core, impacts of the planet when it was created (impacts made heat), radioactive decay of elements, and the extreme amounts of pressure and friction created from rocks pressing down on each other because of gravity. The last of which creates heat only because of gravity. T... | While we can look at Newtonian physics and see that an object with escape velocity greater than <span class="math-container">$c$</span> would give rise to many of the properties of what we now know as blacks holes, the behavior of black holes is more complicated than what is visible from a Newtonian perspective. The f... | As long as it never crosses the event horizon, sure. Once it crosses the event horizon, it's gone forever. Gravity isn't <em>really</em> a force. It's a side effect of the curvature of space. Once you cross the event horizon, space becomes so curved there is simply no path out anymore. All worldlines point towards... | https://physics.stackexchange.com |
62,990 | [
"https://mechanics.stackexchange.com/questions/62990",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/37765/"
] | What type of Fuel does a 2007 f150 v6 4.2L take? The vehicle did not come with a manual, and I need to refuel.
I contacted the Ford dealership they say they will get back to me. They have not yet. I also contacted the Ford company via Facebook and sent me to a generic place with generic information about f150s for the... | A bit of hunting round Google suggests that they're tuned for 87 octane unleaded. You mention unleaded/leaded in your comment - it will have to be unleaded as leaded petrol has been banned for nearly 20 years (unless you live in Algeria, where it was phased out in 2017)
I don't know if it's the same in North America, ... | You MUST USE UNLEADED FUEL ON ANY VEHICLE WITH A CATALYTIC CONVERTOR. ANY car or truck (or motorcycle) uses regular unleaded except for performance vehicles like Corvette, performance Mustangs, new HP Mopars, Ferraris, and so on. Harley Davidson motorcycles also use premium as the Motor Company requires.
| https://mechanics.stackexchange.com |
566,536 | [
"https://physics.stackexchange.com/questions/566536",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/207673/"
] | In Physical Chemistry by Peter Atkins and Julio de Paula, the exponential factor <span class="math-container">$e^{-E_{a}/RT}$</span> indicates the fractions of particles/molecules that have at least the energy <span class="math-container">$E_{a}$</span>. I'm slightly confused because from what I've learnt in statistica... | (a) The title of your question. The concept of coefficient of restitution is useful for macroscopic bodies, but not for microscopic bodies like atoms. The exception is those head-on collisions between atoms when no kinetic energy is lost (elastic collisions). The relative velocity of separation is then equal and opposi... | Yes, we can find the remaining energy distribution by applying conservation of momentum to the problem. Remembering the energy used to change the energy level of the atom.
| https://physics.stackexchange.com |
38,758 | [
"https://security.stackexchange.com/questions/38758",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/22425/"
] | By multi-level authentication, I am referring to the fact that the user makes use of a primary username password keypair to log into his account. Then, to perform some other actions, such as authorize a transaction, he is required to reauthenticate himself by providing a secondary password or passphrase.
So, what are... | If all authentication is done by typing passwords into the same device (your desktop client) - then, yes, <strong>key stroke loggers</strong> are still going to be an issue. Keep in mind that when you separate authentication systems, you open up options to go to multifactor authentication, as well - if not now, then i... | This would not protect you if the attacker managed to get the password, just like any other types of password protected authentication.
It does add a nice extra check, I like these kinds of checks when thing like purchases are made. The PSN (Playstation Network) has this as an option to prevent other people making pu... | https://security.stackexchange.com |
535,561 | [
"https://physics.stackexchange.com/questions/535561",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/191644/"
] | Consider a real scalar field, <span class="math-container">$$\phi(x)=\int\frac{d^3k}{(2\pi)^{3/2}}\left(a_{\vec{k}}v_{\vec{k}}(t)e^{i\vec{k}\cdot\vec{x}}+a_{\vec{k}}^\dagger v^*_{\vec{k}}(t)e^{-i\vec{k}\cdot\vec{x}}\right),$$</span> here the function <span class="math-container">$v_{\vec{k}}(t)$</span> satisfies the no... | Build a simple beam balance: a stiff wire about a foot long, perhaps bent a little at the center for stability, supported in the middle by a piece of string hanging from something, two identical plastic lids hanging from the ends of the wire by three strings. Adjust the balance by a moving support positions or adding a... | There are many ways to create a balance of great sensitivity by mechanical methods, but the main issue for your application is ease of use, I think, and a sensitive mechanical balance would not be quick to use. Therefore I would certainly recommend buying an electronic balance with the required sensitivity. I believe t... | https://physics.stackexchange.com |
79,091 | [
"https://electronics.stackexchange.com/questions/79091",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/27529/"
] | I'm trying to write an electrical engineering paper about different I/O on mobile phones. The inputs, such as the camera, microphone, accelerometer, GPS, can be considered sensors. What's the equivalent word for the outputs, such as display, speakers, vibration, etc? I thought it might be haptic, but haptics are only f... | The commonly accepted term for this is "actuator," although technically that only applies to outputs which generate motion (for example, an LED is not an actuator).
A more general term for both inputs and outputs is "transducer," which is a device that converts one form of energy into another. For example: An LED c... | You might consider using the term " output indicator" or just "indicator". Thus the display is a visual indicator, the speaker is an audio indicator, and the vibrator is a mechanical indicator, etc.
| https://electronics.stackexchange.com |
155,885 | [
"https://chemistry.stackexchange.com/questions/155885",
"https://chemistry.stackexchange.com",
"https://chemistry.stackexchange.com/users/97620/"
] | Usually change is indicated as the difference between some initial and final state. However, for ΔG there seem to be multiple definitions and I am a bit confused. For example, at equilibrium, ΔG = 0 but I am confused as to what the initial and final state between which this 'change' is measured since equilibrium is jus... | Planckton seems to forget that the Gibbs energy is a value that changes with concentration. Let's consider a reaction <span class="math-container">$\ce{A + B <=> C + D}$</span>. In their pure state, the Gibbs energies of formation of <span class="math-container">$\ce{A, B, C}$</span> and <span class="math-contain... | <pre><code>Enthalpy, entropy and Gibbs energy are extensive properties and also state functions.
</code></pre>
Any <em>difference</em> can also be defined as:
Reactants<span class="math-container">$\ce{->}$</span>Products; <span class="math-container">$\Delta_r H = \Sigma H_{\text{Products}} - \Sigma H_{\text{Reacta... | https://chemistry.stackexchange.com |
142,698 | [
"https://softwareengineering.stackexchange.com/questions/142698",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/29020/"
] | As far as I understand it is a wide-spread opinion within the C++ community that certain features of C++ (including some features inherited directly from C), while still usable in themselves, do not fit well with the most recent C++ <em>best practices</em>.
For example, I read a comment on this site stating that new / ... | If I understand correctly your position (from the question and the comments under VJovic's answer), you'd have preferred instead of a mostly compatible C++11, a new language based (I'll call it NC++) on C++03 but source incompatible with it but linkable with it.
Here are some points to consider:
<ul>
<li>it isn't pos... | Bjarne Stroustrup wanted to build a useful language based on C because it was
<ol>
<li>Already popular within s/w community</li>
<li>Supported low level programming as well as some high level features</li>
<li>Lots of code was already written in C</li>
</ol>
There was no plans to have aggressive marketing budget to ... | https://softwareengineering.stackexchange.com |
246,525 | [
"https://electronics.stackexchange.com/questions/246525",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117033/"
] | how can you know the voltage of a circuit, after passing through a resistor? for example there is a 5 volt supply and a resistor of 120 ohms, what will be the voltage after passing through this resistor?
| Answering your question exactly as asked, the voltage will be 5v. That's for a resistor with nothing loading the output.
If you measure the voltage with a real DMM, having an input impedance of 10M or so, then the voltage will drop very slightly to 4.999... something (not the right number of 9s, I haven't done the exa... | Given a complete description of any circuit made up of linear resistors, independent DC current and voltage sources, and linear dependent current and voltage sources, you can exactly calculate the voltage at every node and the current through every branch in the circuit. Two of the best known ways of doing this are cal... | https://electronics.stackexchange.com |
216,900 | [
"https://electronics.stackexchange.com/questions/216900",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/35276/"
] | This is probably a really silly question, but I still want to know...
Given a standard off-the-shelf FM radio alarm clock, what is to stop it from transmitting radio waves when physical motion causes the speaker to move?
The theory is that if FM waves can come in to the antenna, through any tuning circuit, and be spi... | If you shine a torch on an incandescent lamp will voltage come out - no it won't. If you heat up a resistor will DC voltage come out - no but you'll get more noise voltage (a few micro volts maybe).
The back stage of a receiver is an audio power amp and you might see a few microvolts of signal at its input when you sh... | <blockquote>
In the perfect laboratory scenario, would I see any RF output from doing this?
</blockquote>
If the receiver is a "Superheterodyne receiver" (as many COTS FM radios are) there is a local oscilator (LO) which operates at a similar frequency to the frequency the radio receives. Some of the output from the... | https://electronics.stackexchange.com |
132,528 | [
"https://electronics.stackexchange.com/questions/132528",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/54849/"
] | I'm not sure if I am in the good site but here's my question :
I was questionning myself, what would be comparable(execution speed) between a 32bit and 64bit processor. Like what would be the clockrate of a 32bit processor to be as the same speed as a 64bit processor.
Ps : English is not my first language.
Wood
| Assuming that you're talking about the x86 and x64 instruction sets, there's not a whole lot of difference as the x64 set is backwards compatible with x86, meaning that a 32-bit operating system will easily run on 64-bit hardware. However, being designed around 32 bits, it will only be able to access 2^32 bytes = 4GB ... | <em>Unless</em> the code is handling values bigger than 2^32, there is unlikely to be any measurable difference for a similar Instruction Set Architecture (ISA), with similar cache and memory interface.
However 32bit processors usually have a smaller cache than a 64bit processor, just because of the generation of tech... | https://electronics.stackexchange.com |
5,389 | [
"https://chemistry.stackexchange.com/questions/5389",
"https://chemistry.stackexchange.com",
"https://chemistry.stackexchange.com/users/1743/"
] | This is balanced equation of fermentation of glucose:
<span class="math-container">$$\ce{C6H12O6(aq) -> 2C2H5OH(aq) + 2CO2(g)}$$</span>
I know that the result of glucose fermentation is ethanol (<span class="math-container">$\ce{C2H6O}$</span>). What represented in the aforementioned equation is slightly different... | It is better to write <span class="math-container">$\ce{C_2H_6O}$</span> as <span class="math-container">$\ce{C_2H_5OH}$</span>, because there is more than one compound with the same overall formula, and emphasising the <em>hydroxyl group</em> <span class="math-container">$\ce{-OH}$</span>, which is what characterizes ... | I confused compound formula with the actual formula of ethanol. Compound formula is $\ce{C2H6O}$. But the actual molecular structure is $\ce{CH3CH2OH}$. The oxygen is attached to hydrogen which it in turn is attached to Carbon.
| https://chemistry.stackexchange.com |
349,968 | [
"https://mathoverflow.net/questions/349968",
"https://mathoverflow.net",
"https://mathoverflow.net/users/69849/"
] | This might be a trivial question, but I am trying to prove equi-coerciveness of some family of functions on the space of Probability measures on some space. I could reduce the problem to showing that <span class="math-container">$$\{\nu:\mathcal{W}_2^2(\mu, \nu)\le t\}$$</span> is compact (or is at least contained in s... | Yes, it is true. It follows from Prokhorov's theorem that in order to prove (pre-)compactness, it suffices to prove tightness. However, if we define <span class="math-container">$K$</span> to be the compact set such that <span class="math-container">$\mu(\mathbb{R}\setminus K)<\varepsilon$</span>, and <span class="m... | Since we care about probability measures, a sufficient condition for compactness is that the supports of the respective probability measures are compact. Here is the reasoning:
<ol>
<li>Let <span class="math-container">$X$</span> be a compact subset of <span class="math-container">$\mathbb{R}^d$</span>. Denote by <spa... | https://mathoverflow.net |
39,056 | [
"https://mathoverflow.net/questions/39056",
"https://mathoverflow.net",
"https://mathoverflow.net/users/9292/"
] | Can someone please tell me some introductory book on symplectic geometry? I have no prior idea of the subject but I do know about Lagrangian and Hamiltonian dynamics (at the level of Landau-Lifshitz Vol. 1). Thanks in advance. :-)
| If you are physically inclined, V.I.Arnold's <em>Mathematical methods of classical mechanics</em> provides a masterful short introduction to symplectic geometry, followed by a wealth of its applications to classical mechanics. The exposition is much more systematic than vol 1 of Landau and Lifschitz and, while mathemat... | You can find a very nice introduction to the subject in these notes by Ana Cannas da Silva:
www.math.princeton.edu/~acannas/symplectic.pdf
| https://mathoverflow.net |
414,514 | [
"https://physics.stackexchange.com/questions/414514",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/198107/"
] | Considering that the gravitational field of a spherical shell is rectified in its interior, can I consider that even then the time inside it is dilated with respect to a distant clock?
Imagine the following situation:
A massive spherical shell located in the cosmos away from everything. Inside it has a watch (A). On ... | The solution to your question is time A = time B < time C.
The reason is that since there is no mass inside the hollow region, the Schwarzschild radius is zero.
The metric in the hollow region is flat Minkowski space.
Time ticks still differently inside the shell then outside the shell.
Because where <span class... | As was pointed out by @Arpad Szendrei gravitational time dilation depends on the gravitational potential. To answer the question we make use of Newton’s Shell Theorem according to which the mass <span class="math-container">$M$</span> of the shell can be thought as to be concentrated at its center for any point outside... | https://physics.stackexchange.com |
235,573 | [
"https://electronics.stackexchange.com/questions/235573",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/63846/"
] | Majority of the assembly factories are asking for SMT jobs. My gut tells me through hole would be a better option for a high voltage application.
Before the high voltage project is started, we need to make a call on SMT or Through hole parts.
Is there a study on this?
High Voltage application I mean : 3Phase 480v s... | Most SMT components have small clearance between the pads. Which is why for higher voltage thay not fit. Google "trace clearance calculator", it will help. In addition, resistors will have to be rated to higher power, capacitors will be bigger, so SMT will not fit mechanically.
On the other hand, some components may ... | First: 400V is not technically "high voltage". High voltage is generally defined as starting at 1000V.
That being said, there is absolutely nothing wrong in general with using surface-mount parts in a device running at these voltages, so long as the parts you are using are rated for voltages you are using them at. Kee... | https://electronics.stackexchange.com |
661,361 | [
"https://physics.stackexchange.com/questions/661361",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/261490/"
] | I read the FLP vol. 2 and in the chapter 1, section 1.4 Feynman states from the physical point of view to form the intuition
<span class="math-container">$$c^2(\text{circulation of B around the curve} \ C)=\frac{d}{dt}(\text{Flux of E through the surface}\ S)+\frac{\text{Flux of electric current through}\ S}{\varepsilo... | The flux of the electric field through a surface <span class="math-container">$\mathcal{S}$</span> is defined as:
<span class="math-container">\begin{equation}
\Phi_E=\int_{\mathcal{S}}\boldsymbol{E}\cdot d\boldsymbol{a}
\end{equation}</span>
Thus
<span class="math-container">\begin{equation}
c^2\oint_{\Gamma}\boldsymb... | You correctly write the equation in the <strong>integral</strong> form as
<blockquote>
<span class="math-container">$$c^2(\text{circulation of B around the curve} \ C)=\frac{d}{dt}(\text{Flux of E through the surface}\ S)+\frac{\text{Flux of electric current through}\ S}{\varepsilon_0}$$</span>
</blockquote>
which writ... | https://physics.stackexchange.com |
206,127 | [
"https://physics.stackexchange.com/questions/206127",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/60715/"
] | I was reading about COM and forces and came upon this in my book.
<blockquote>
If a projectle explodes in air in different paths,the path of the centre of mass remains unchanged.This is because during explosion no external force (except gravity ) acts on the COM.
</blockquote>
My question is, even though the author... | Because gravity was acting on the projectile before it exploded, it was already taken into account. It wasn't turned on at the time of the explosion.
The phrase "the path remains unchanged" is referring to the gravity-induced parabola that the object was on prior to the explosion, not to a straight line that it would... | The passage means that the center of mass follows the same parabolic trajectory it would have followed had there been no explosion. This includes the effect of gravity.
| https://physics.stackexchange.com |
635,781 | [
"https://physics.stackexchange.com/questions/635781",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/260493/"
] | In the Gamov model of alpha decay they use the WKB approximation to find the magnitude of the stationary state wavefunction of an alpha particle with a given fixed energy <span class="math-container">$Q$</span> that has tunnelled through the potential barrier of the nucleus, then say the rate of alpha decay <span class... | <ol>
<li>There is no difference in potential from A to C, so there can be no acceleration of electrons.
</li>
<li>Either <span class="math-container">$n$</span> (which I’m assuming is the charge carrier density) or <span class="math-container">$A$</span> (which I’m assuming is the cross sectional area of the resister) ... | <blockquote>
Why does current not increase on passing through a zero-resistance
wire?
</blockquote>
Because the charge theoretically would not experience any force in a zero-resistance wire due to the voltage between any two points in the wire being zero.
The force <span class="math-container">$F$</span> experienced by... | https://physics.stackexchange.com |
367,483 | [
"https://physics.stackexchange.com/questions/367483",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/82505/"
] | I am trying to find the eigenvectors of the operator:
$$
S_{u}=\frac{\hbar}{2}\left(
\begin{matrix}
\cos{\theta} & e^{-i\phi}\sin{\theta} \\
e^{i\phi}\sin{\theta} & -\cos{\theta}
\end{matrix}
\right)
$$
I have already found that the eigenvalues are $+\frac{\hbar}{2}$... | Your goal is a little bit excessive: you want to rephrase things in terms of the half-angle $\theta/2$, but $\phi$ should be left as-is. With that in mind, then, you simply see $\sin(\theta)$ and $\cos(\theta)$ as double-angle trigonometrics applied to $\theta/2$, and use the standard trigonometric identities with this... | Normalizing the kets and using trigonometric identities : $\cos\theta=\cos^2\frac{\theta}{2}-\sin^2\frac{\theta}{2}$ and $\sin\theta=2\sin\frac{\theta}{2}\cos\frac{\theta}{2}$. You can write the eigenkets as :
$$|+\rangle_{u}=\begin{pmatrix}e^{-i\frac{\phi}{2}}\cos\frac{\theta}{2} \\e^{i\frac{\phi}{2}}\sin\frac{\theta... | https://physics.stackexchange.com |
519,184 | [
"https://physics.stackexchange.com/questions/519184",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/249453/"
] | Suppose we have an object which the mass is <span class="math-container">$m$</span> kg. If we lift up the object and the object moves with constant upwards velocity, the force we're applying on it will be equal to <span class="math-container">$mg$</span>, and say if the object moved a distance of <span class="math-cont... | The issue is that if you are taking into account the change in gravitational potential energy, then you have also already taken into account the work done by gravity.
For any conservative force, the work done by that force over some path <span class="math-container">$C$</span> is equal to the negative change in potent... | My insight after 2 years is that potential energy is stored in the gravitational field, so the work done by us is taken by the negative work done by the field.
| https://physics.stackexchange.com |
176,970 | [
"https://softwareengineering.stackexchange.com/questions/176970",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/73485/"
] | I am in the planning process for a new application, the application will be written in PHP (using the Symfony 2 framework) but I'm not sure how relevant that is. The application will be browser based, although there will eventually be API access for other systems to interact with the data stored within the application... | I would start by defining a core API that you think that you can support across all of your providers. Later you can extend with optional methods, and checks to let you know which actions particular providers support. But that is definitely a stage 2.
That core API needs to be asynchronous because some of the provid... | I recommend to think in use cases. A use case for example is "Activate SIM Card". Create a interface like ActivateSimCardController or ActivteSimCardInteractor. Implementations of this interface are specific for every SIM card provider. To create the right implementation you need an identification for the provider, so ... | https://softwareengineering.stackexchange.com |
100,511 | [
"https://dba.stackexchange.com/questions/100511",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/65659/"
] | I am moving from one server to another and I want to backup all databases + users/privileges/passwords from my MySQL Server. I found to backup a database using <code>mysqldump</code>, but I cannot figure out, how to backup all users and the given privileges. Is there a way to achieve this or do I have to set this newly... | The 'mysql' database contains users/privileges/passwords. So take the dump of mysql database along with other databases
<pre><code>mysqldump [options] --all-databases > all_databases_dump.sql
mysqldump -u root -p mysql user > user_table_dump.sql
</code></pre>
These mysql database tables contain grant informati... | This PHP script was inspired by the need to do the same thing as the original question where the servers in question were running different version of MariaDB. Since it's PHP it should work on any platform that supports PHP (version 7.3 or higher).
<pre><code><?php
ini_set('display_errors','1');
ini_set('display_st... | https://dba.stackexchange.com |
200,392 | [
"https://stats.stackexchange.com/questions/200392",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/60947/"
] | Suppose I empirically estimate the standard error of some statistic to be 10% (perhaps I do this by bootstrapping).
Now, I want to know how much I need to increase the sample size to reduce the error to 5%. The estimate and sample are arrived at through complex procedures, and theoretically determining the relationsh... | <blockquote>
regardless of the estimate and the sampling procedure?
</blockquote>
No, you will not have a "root-n" effect <em>regardless</em> of those things, since at least some standard errors do not scale with $\sqrt{n}$.
Many do -- quite possibly all the ones you will be likely to use -- but that's not all of t... | Yes, generally, more samples would lead to smaller standard error. However, since adding more data is generally a random process, the decrease in standard error is not monotonic.
Consider the special case of Monte Carlo. Suppose you draw i.i.d samples from a distribution $F$, $X_1, X_2, \dots, X_n$. Suppose $Var_F(X_... | https://stats.stackexchange.com |
510,433 | [
"https://math.stackexchange.com/questions/510433",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/75699/"
] | If x=1 and y=1, what is the theta and why?
I know for a fact that the answer is pi/4 but I do not get why.
| Given $(x,y)\in \Bbb R^2$, you can find $\rho\in \Bbb R^+$ and $\theta \in [-\pi,\pi]$ such that $(x,y)=\rho (\cos (\theta), \sin (\theta))$, where $\rho=\sqrt {x^2+y^2}$ and, with $\tan$ defined on $ \left[-\pi , -\frac \pi 2\right[\cup \left]-\frac \pi 2, 0\right]$ (so that $\theta \in [-\pi,\pi]$), $$\theta =\begin... | $$x = r\cos \theta = 1\;\text{ and }\;y = r\sin\theta = 1$$ $$\tan\theta = \dfrac {\sin\theta}{\cos \theta} = \dfrac xy = 1$$
$$\theta = \arctan 1 = \dfrac \pi 4 $$
$r$ is simply $\sqrt{1^2 + 1^2 } = \sqrt 2$. Recall, the radius is equivalent to $r$ where $$x^2 + y^2 = r^2$$
So $(x, y) = (1, 1)$ in Cartesian Coordi... | https://math.stackexchange.com |
60,792 | [
"https://electronics.stackexchange.com/questions/60792",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/20131/"
] | This concerns hardware that does weighs little, because a (fat cat sized, 6 legs with 3 DOF) walking robot should carry it around. Because of that walking it'll need to do a lot of trigonometry (using matrix math or not i'm not sure yet) and this is where this question comes from.
PIC, Arduino or cheap AVR is not fast... | It does not sound like your application is really all that compute intensive. A dsPIC, for example, can execute 400 k instruction for each one of your iterations. That's a lot. It will be useful, however, to have good low level I/O capability, PWM generators, timers, and the like.
Sine and cosine is really not that... | You're going to deal with a lot of input signals. You don't necessarily need a CPU with a high throughput; a lot of signals can be processed in parallel. This is typical DSP territory. Of course, you do want general CPU functionality as well. This is no problem. There are plenty of CPU's with integrated DSP's.
A typi... | https://electronics.stackexchange.com |
21,142 | [
"https://mathoverflow.net/questions/21142",
"https://mathoverflow.net",
"https://mathoverflow.net/users/5316/"
] | To assuage my conscience over an unsourced statement in a paper I'm writing:
I am looking for an example of a commutative algebra over the complex numbers having a maximal ideal of codimension >1, or a statement of inexistence.
| If the codimension is finite, then there is no such thing. If the codimension can be infinite, then yes, because there are infinite dimensional complex division algebras which are simple, like $\mathbb C(t)$.
| By codimension you just mean as a $\mathbb{C}$-vector space? Take the rational function field $\mathbb{C}(t)$.
(Note: by the Nullstellensatz, it is not possible to do so with a finitely generated $\mathbb{C}$-algebra.)
| https://mathoverflow.net |
351,527 | [
"https://stats.stackexchange.com/questions/351527",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/189452/"
] | <strong>Ms. A selects a number $X$ randomly from the uniform distribution
on $[0, 1]$. Then Mr. B repeatedly, and independently, draws numbers
$Y_1, Y_2, ...$ from the uniform distribution on $[0, 1]$, until he gets a number
larger than $\frac{X}{2}$, then stops. The expected sum of the number Mr. B draws, given $X = x... | Although, you didn't include <code>self-study</code> tag, I first give you two hints and then full solution. You may stop reading after first or second hint and try youself.
<strong>Hint 1</strong>:
For $a \in (0,1)$ we have $$\sum_{m=0}^{\infty} ma^m = \frac{a}{(1-a)^2}$$
<strong>Hint 2</strong>:
Let $K$ be number... | Another angle of solution (summing not with P(K=k) but P(K>=k)):
$$\begin{array}\\
E(\sum Y_k) = \sum E(Y_k) & = \sum_{k=1}^\infty E(Y_k|K>=k) \cdot P(K>=k) \\
& = \sum_{k=0}^\infty \frac{1}{2} \cdot \left(\frac{x}{2} \right)^k \\
& = \frac{1}{2-x}
\end{array}$$
| https://stats.stackexchange.com |
709,480 | [
"https://physics.stackexchange.com/questions/709480",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/335923/"
] | Suppose a car with electrical engine moves uniformly with friction between wheels and the ground (neglect air resistance, energy loss, etc.). So why the car's engine power must be equal to friction's power for the car to move uniformly?
| If the engine produces more power, that has to go somewhere, and in the situation you describe, it will go into kinetic energy, meaning to accelerate the car.
If it produces less power, the friction will get its missing power from kinetic energy, thus decelerating the car.
Only if the engine power matches the friction ... | You loos energy by heating the surrounding by friction. Your engine has to produce (at least) that energy every second, and energy=power times time.
| https://physics.stackexchange.com |
76,881 | [
"https://electronics.stackexchange.com/questions/76881",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/7624/"
] | I need to cover up a line of text on the silkscreen of some PCBs and I'm not sure of the best way to do it. I've read that removing the printed text with a chemical will likely damage the boards, so covering it up seems like the best option.
Can something like a Sharpie permanent marker be used on a PCB's silkscreen ... | Yes. Some PCB fabs even use markers to mark good and tested boards.
| Permanent marker ink is non-conductive and won't damage the traces or the solder mask. It can however act as etch resist, so don't use it on a board you want to etch unless this is desired.
| https://electronics.stackexchange.com |
674,286 | [
"https://physics.stackexchange.com/questions/674286",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/284150/"
] | In my book, it's given that:
<blockquote>
”Principle of Capacitor: In the capacitor arrangement, the increase in capacitance of a conductor is due to the decrease in potential V (charge Q remains constant) when another conductor is brought near to it. Suppose a metallic plate A fitted to an insulated stand is given the... | This may be to do with definitions. Stress is force per unit area and I think for this there is just this definition and it is unambiguous. Strain is extension divided by length, but now there is room for confusion because one has to specify the extension compared to what. That is, if we write
<span class="math-contain... | If an isotropic material is not under stress and its temperature is changed, then the linear strain within the material is the same in all arbitrary directions, and equal to <span class="math-container">$\alpha \Delta T$</span>, where <span class="math-container">$\alpha$</span> is the linear coefficient of thermal exp... | https://physics.stackexchange.com |
33,371 | [
"https://scicomp.stackexchange.com/questions/33371",
"https://scicomp.stackexchange.com",
"https://scicomp.stackexchange.com/users/32745/"
] | For a performance-sensitive problem, I need to compute the pseudoinverse of a skinny matrix (#rows = 1000–10000, #cols= 10–20).
I already employ the traditional SVD econ method. For some problem sizes, this takes up most of my computational time. Is there any faster method?
The matrix is dense, and usually (<span clas... | If <span class="math-container">$A$</span> is of full column rank and <span class="math-container">$A^{T}A$</span> is non-singular and well-conditioned, then you can compute the pseudoinverse as:
<span class="math-container">$ A^{\dagger}=(A^{T}A)^{-1}A^{T} $</span>.
This will be faster than computing a QR or SVD f... | You can "frontend" the SVD of a tall/skinny matrix using a QR decomposition, then just SVD the remaining small/square matrix R. Here's a snippet of matlab code that computes the pseudoinverse based on this idea:
<pre><code>clear all
close all
% Make input.
I = 10000;
J = 20;
A = rand(I,J);
% Pseudoinverse B := pinv(... | https://scicomp.stackexchange.com |
4,340,448 | [
"https://math.stackexchange.com/questions/4340448",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/1008043/"
] | Let's consider a <span class="math-container">$2\times 2$</span> rotation matrix <span class="math-container">$R_\theta \in SO(2,\mathbb{R})$</span>, and the following matrix obtained by repeatedly applying <span class="math-container">$n-1$</span> times the Kronecker product of <span class="math-container">$R_\theta$<... | This is just about the <span class="math-container">$n=2$</span> case.
If <span class="math-container">$e_1,e_2$</span> is the standard basis of <span class="math-container">$V=\mathbb{R}^2$</span>, then the matrix of <span class="math-container">$R_\theta\otimes R_\theta$</span> on <span class="math-container">$V\otim... | Let <span class="math-container">$c=\cos \theta, s=\sin \theta$</span>. We have
<span class="math-container">$$Q_{\theta}=\begin{pmatrix} c^2& -cs& -cs& s^2\\
cs & c^2& -s^2& -cs\\
cs & -s^2& c^2& -cs\\
s^2 & cs & cs& c^2\end{pmatrix}$$</span>
Due to the fact t... | https://math.stackexchange.com |
23,376 | [
"https://physics.stackexchange.com/questions/23376",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/8348/"
] | As it is, what is currently and seemingly incomplete in M-theory?
One example I can give is explaining dark matter proportions
and.. how do we perceive the world as 4-dimensional.
Thanks everyone.
| A major list of incomplete things in M-theory (I will ignore those that are not M-theory specific, which you can find in generic string theory questions):
<ul>
<li>2-brane constructions--- if you make a 2-brane stack, this is described by Schwarz Chern-Simons theory, under certain conditions. Making the general AdS/CF... | One basic thing that's incomplete about M-Theory is that the theory isn't even completely defined. One can talk about M-Theory in certain limits where it reduces to string theory, or one can talk about the low energy (non-quantum) supergravity theory which M-Theory reduces to, but there is no definition of what M-Theo... | https://physics.stackexchange.com |
66,371 | [
"https://physics.stackexchange.com/questions/66371",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/24860/"
] | If $D$ is critical dimension of Bosonic strings, a particular derivation goes like the following, where we arrive finally at
$$ \frac{D-2}{2}\sum_{n=1}^\infty n + 1 = 0. $$
Now mathematically this is clearly a divergent series, but using zeta function regularization here we are taking
$$ \sum_{n=1}^\infty n = \zeta(-... | I know some derivations in which one can track the emergence of the concrete value, without having to buy that the second order contribution in the Euler-MacLaurin formula (see other answer) is $-\frac{1}{2!}$ times the second Bernoulli number $B_2$.
<hr>
The limit $\lim_{z\to 1}$ of the sum
$0+1\,z^1+2\,z^2+3\,z^3+... | A way to do this is using regularization by substracting a continuous integral, ,with the help of the Euler-MacLaurin formula:
You can write :
$$ \sum_{Regularized} =(\sum_{n=0}^{+\infty}f(n) - \int_0^{+\infty} f(t) \,dt) = \frac{1}{2}(f(\infty) + f(0)) + \sum_{k=1}^{+\infty} \frac{B_k}{k!} (f^{(k - 1)} (\infty) - f... | https://physics.stackexchange.com |
431,432 | [
"https://softwareengineering.stackexchange.com/questions/431432",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/172973/"
] | For some more type safety I wanted to introduce a <code>PageId</code> type in my application. However, I am not totally sure what the best option to do so is.
I want the IDs to be GUIDs, so I thought I just create a <code>PageId</code> class which inherits from the <code>Guid</code> class. Unfortunately the <code>Guid<... | As you already mentioned for newer C# version you can wrap <code>Guid</code> value with the <code>record</code> type. You will get required equality functionality for "free".
<pre><code>public record PageId(Guid Value);
</code></pre>
For older C# versions you can wrap <code>Guid</code> with the dedicated stru... | The use of a GUID as a unique Identifier is not necessarily user friendly. For example test automation would have to identify the GUID in the object, copy it and place into the test. This is why we see IDs in often look more like "AccountsReceivable" as they are just are better suited for readability.
If you... | https://softwareengineering.stackexchange.com |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.