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 |
|---|---|---|---|---|---|
37,826 | [
"https://quant.stackexchange.com/questions/37826",
"https://quant.stackexchange.com",
"https://quant.stackexchange.com/users/31458/"
] | I know that if you short a stock you borrow it from a broker, immediately sell it, and then buy it back at (hopefully) a lower price.
But I don't understand how it impacts the leverage of a portfolio. E.g.,
Suppose you have a \$100 initial capital, and ABC is trading at \$10 per share. If you decide to short 5 ABC sh... | One way of looking at it is how much stock is in your control.
The calculation that I have seen most frequently in Long-Short portfolios for the leverage calculation is (Longs + Shorts)/Equity.
In your example, assuming the $100 is invested in a long position:
($100 Long + $$50 Short) / $100 = 1.5 or 150%
| Leverage depends on the security you are shorting and what your brokerage will offer. Typically for retail investors leverage will be lower (2-4x). For institutional clients a brokerage can offer significantly higher leverage. Also it will depend on the security, generally speaking leverage is higher on low volatility ... | https://quant.stackexchange.com |
249,458 | [
"https://softwareengineering.stackexchange.com/questions/249458",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/29289/"
] | I've run into a problem where I have a set of inputs, as well as a couple known input-output pairs. I am interested in the output, but in order to get that, I need to figure out how the input is used to generate the output.
So for example, I might have the following input strings along with a few known output strings
... | This is a classic machine learning problem. It's an example of regression. You'd want to split your set of "knowns" into two groups, one to train with, and one to test against. Set up the appropriate machine learning algorithm* and train with part of your knowns. Then input the other set of inputs to check the reliabil... | You should definitely get more experience in theoretical computer science. This function is trivial to define. Say you have pairs <code>p_i = (I_i, O_i)</code> of input/output pairs, then you can define <code>f(I)</code> by a simple chained if-else, in which you test whether <code>I == I_i</code> and then return <code>... | https://softwareengineering.stackexchange.com |
174,458 | [
"https://dba.stackexchange.com/questions/174458",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/5068/"
] | I would like to create a table on the master, whose data are not replicated to the slave.
I'm temporarily inserting many millions of rows in this table a part of a batch job; the data in this table can be re-created on demand, hence do not need to be replicated on the (slower) slave.
I don't want to use <code>TEMPORA... | First this is a horrible idea,
<pre><code>team_a int REFERENCES players (pid),
</code></pre>
This will make everyone hate you. If there is no difference between a <code>team</code> and a <code>player</code> -- use the same name. Pick or have a difference.
<blockquote>
I want to make a query so i can also be able t... | I tried this in Sql Server,it should work in PostgresSql .
<blockquote>
I want to show playerid, playername, total wins and total matches
played in 1 table
</blockquote>
<pre><code>;with CTE as
(
select m.winner ,count(m.winner)TotalWin from @matches m
group by m.winner
)
,CTE1 AS(
select pid,count(pid)TotalPlaye... | https://dba.stackexchange.com |
96,482 | [
"https://security.stackexchange.com/questions/96482",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/83109/"
] | If my neighbor (whom I have allowed to connect to my router) is sharing my internet via Bluetooth tethering, is there a way to prevent anyone else from sharing my internet via his or my Bluetooth without cutting him off?
| Basically, anyone allowed to connect to your router/wifi access point can in turn make their computer (or whatever device) into a router of their own. They can then, without your router even knowing, create their own little network and share internet amongst themselves, then relaying the traffic through one device.
Y... | Bluetooth does not create a strong internet signal so anyone connecting to it would have to pair to his device that is tethered. They would have to be in a 60 foot radius of that device in most cases. I don't think there is anything on your home consumer based router that will allow you to block him. Since he connects ... | https://security.stackexchange.com |
37,334 | [
"https://electronics.stackexchange.com/questions/37334",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/8698/"
] | I wounder what is the format of the serial data stream that usually is sent from computer to arduino through serial connection .
my project use serial connection with arduino to send data from python(pyserial) to arduino , and when I send a string and I try to print it on LCD it appears but the first character change... | Strings need to be terminated in a '\0' character (typically 0x00) to indicate where the end of the string is.
e.g if you initialise a string like this:
<pre><code>char message[] = "hello";
</code></pre>
It will store 'h' 'e' 'l' 'l' 'o' '\0' in the memory.
Then in a routine like 'print', the code loops through the... | This is the Python function I use for configuring Arduino serial ports. Give it a try:
<pre><code>def configure_port(port_id):
ser = serial.Serial()
ser.port = port_id
ser.baudrate = 9600
ser.rtscts = True
ser.dsrdtr = True
return ser
</code></pre>
Usage:
<pre><code>port = configure_port("/de... | https://electronics.stackexchange.com |
631,133 | [
"https://physics.stackexchange.com/questions/631133",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/289125/"
] | Suppose we have two rockets, A and B, and they are initially close together and on the same axis but facing in opposite directions. Their masses are <span class="math-container">$m_A$</span> and <span class="math-container">$m_B$</span> respectively, excluding fuel. Rocket
A has fuel of total mass <span class="math-con... | This is a great question.
The normal path integral formula is
<span class="math-container">$$
\langle q_f | e^{- i H T} | q_i \rangle = \int_{q(0) = q_i}^{q(T) = q_f} \mathcal{D}q(t) e^{i S[q(t)]}.
$$</span>
I won't type out the proof of this formula, but it involves breaking up <span class="math-container">$T$</span> ... | I think that a better way of thinking about Euclidean vs Lorentzian path integrals is not by making time imaginary but by changing the signature of the timeline metric. Let me explain myself.
The variables over which we are integrating in the path integral can be thought of as maps <span class="math-container">$q:[t_0,... | https://physics.stackexchange.com |
378,207 | [
"https://mathoverflow.net/questions/378207",
"https://mathoverflow.net",
"https://mathoverflow.net/users/169985/"
] | Consider the vertices of an <span class="math-container">$n$</span>-dimensional cube. The distance between two vertices is measured as the minimum number of edges between the two vertices. Now consider a subset of these vertices.
If we call the total set of vertices as <span class="math-container">$T$</span> and the su... | Partial answer: the minimal dimension is at least
<span class="math-container">${n-2 \choose 2} + 1$</span>, with equality if <span class="math-container">$n-1$</span> is a power of <span class="math-container">$2$</span>.
For example, if <span class="math-container">$n=5$</span> the minimum is <span class="math-contai... | One more exact answer: for <span class="math-container">$n=8$</span> the minimal dimension is <span class="math-container">$22$</span>,
again attaining the "easy" bound <span class="math-container">${n-1 \choose 2} + 1$</span>
and the same as the value for the next dimension <span class="math-container">$n=9$... | https://mathoverflow.net |
645,625 | [
"https://electronics.stackexchange.com/questions/645625",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/213323/"
] | Let's say we set the com-port settings on the PC side with double stop-bit. And then we set the com-port settings on the device side with single stop-bit.
<ol>
<li>Can we detect stop-bits mismatching with software?</li>
<li>Can we detect stop-bits mismatching with software in Windows?</li>
<li>Can we detect stop-bits m... | The Arduino MCU ATmega328P datasheet says that
<blockquote>
The Receiver and Transmitter use the same setting. Note that changing the setting of any of these bits will corrupt all ongoing communication for both the Receiver and Transmitter. An FE (Frame Error) will <strong>only be detected in cases where the first stop... | Possible, yes, but it depends on the hardware, and maybe on drivers. It is very unlikely though. Not many hardware chips even verify both stop bits, just one.
The receiver also cannot detect the difference between 1 and 2 stop bits if there is a pause between the frames.
If the hardware checks both stop bits, then only... | https://electronics.stackexchange.com |
302,342 | [
"https://physics.stackexchange.com/questions/302342",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/52332/"
] | A claim is made in Sean Carroll's GR book multiple times that goes along the following lines:
<em>Given a problem in relativity, we can find a solution with ease if we choose a convenient reference frame (for instance, a frame co-moving with an object we're interested in, or if we're in curved spacetime, we could go ... | This can't happen, because if a tensor is zero in one frame it is zero in any frame. Suppose you have some expression which works in a specific frame, and you know that the tensor $T$ reduces to that in your frame. Now suppose that the tensor $S$ also reduces to your expression. Then the tensor $T-S$ is zero in our spe... | This is a great question and as per usual the answer is that Sean Carroll is absolutely right. :) Javier has given a great reason why this is sort of the obvious expectation but I sometimes find that these questions point to a much deeper conceptual confusion so I will try to tell you how it works out "the hard way" in... | https://physics.stackexchange.com |
16,159 | [
"https://softwareengineering.stackexchange.com/questions/16159",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/691/"
] | We're outsourcing some work to an external developer, so I'm busy writing up a contract about what constitutes a deliverable.
So far I require that the code is shipped with automated tests.
But, what is a reasonable way to specify the detail of tests up-front in the contract in a measurable way?
I'm loathe to say "... | When subcontracting out, it is up to you to ensure the code being written at least <em>works</em> the way you need it to. For that reason, your team will need to write some automated acceptance tests. Provide those tests to your subcontractor, so they can make sure their code works with it.
Anytime you require perce... | You can come up with more specific measure. E. g. 100% coverage for methods with cyclomatic complexity >= 5. Etc...
| https://softwareengineering.stackexchange.com |
447,009 | [
"https://physics.stackexchange.com/questions/447009",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/75502/"
] | Imagine water molecules inside a water pipe is moving due to difference in pressure, this pressure can be due to difference in gravitational potential or external force like somebody squeezing at one end. In the case of a piece of wire, how can the electrons inside knows that there is a voltage potential diff between t... | To define the four-velocity, we need to specify a worldline. This is evident from the definition <span class="math-container">$U^\mu=dx^\mu/d\tau$</span>, which involves a derivative with respect to proper time <span class="math-container">$\tau$</span>. The proper time is defined only for a given worldline.
The metri... | The metric <span class="math-container">$g_{\mu\nu}$</span> is a symmetric, <strong><em>nondegenerate</em></strong>, positive definite 2-tensor, which should have eigenvalues <span class="math-container">$(\pm1,\mp1,\mp1,\mp1)$</span> in every coordinate system you choose.
The symmetric outer product of a time-like f... | https://physics.stackexchange.com |
134,445 | [
"https://electronics.stackexchange.com/questions/134445",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/24251/"
] | I am charging my capacitor with a binary pulse train (either 1V or 0V). I notice that when the voltage stays at 0V, the capacitor discharges itself.
As shown, the green curve signal is connected to one terminal of the capacitor, and the blue curve signal is the voltages across the capacitor.
<img src="https://i.stack.i... | <blockquote>
Is this expected? Previously, I thought the voltage will rise when 1V
but never fall when 0V. So I am expecting voltage across the capacitor
to be a "staircase" waveform.
</blockquote>
What you are looking to achieve is called an integrator. With an integrator, the output stays where it formerly rea... | The discharge is expected. The idea is simple: When the charging voltage is +1, the capacitor tries to reach that value and you see the wave rising. Later, when the charging voltage changes to zero, the capacitor does the same: it tries to reach the value == 0. So you see the wave going down. The easiest way to prevent... | https://electronics.stackexchange.com |
285,344 | [
"https://stats.stackexchange.com/questions/285344",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/122361/"
] | I have a three-way 2x2x3 ANOVA, which initially showed a significant AxBxC interaction
(but no significant two-way or main effects)
I've broken this down into two-way ANOVAs to try to interpret the result, however:
1) Splitting it by variable "A", doing two two-way ANOVAs (i.e. for each of two levels of "A"), gave n... | If your data set is quite large, you could consider fitting a 5%- and a 95%-quantile regression, e.g. representing the functional relationship by splines.
| One possibile procedure to consider:
A) First fit the data normally, perhaps to a spline.
B) Add an offset to the fitted equation, perhaps iteratively, until 95% of the points are below the now-offset equation. This would be the upper bound.
C) Subtract an offset from the fitted equation, perhaps iteratively, until ... | https://stats.stackexchange.com |
238,991 | [
"https://security.stackexchange.com/questions/238991",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/243462/"
] | i got till moment when i do not know if it is secure!
If SQL injection is inserted into <code>myTableTwo</code> via safe PDO query will it make my query below SQL injection open? Is the query below safe?
<code>$mysfield</code> returns SHOW COLUMNS FROM <code>myTable</code>
<code>myTable</code> columns match <code>myTab... | The way I solved this is by editing an already present dynamic config in john the ripper jumbo. I opened dynamic.conf and edited dynamic_1029 to look like this:
<pre><code>[List.Generic:dynamic_1029]
Expression=sha256($p.$s) (hash truncated to length 32)
Flag=MGF_FLAT_BUFFERS
Flag=MGF_SALTED
SaltLen=16
MaxInputLen=110
... | I'm not aware of an attack tool that will currently do this without at least some external processing (which means reduced speed):
<ul>
<li>hashcat supports the format (-m 22300), but doesn't check for truncation</li>
<li>JtR appears to support the format (with a dynamic mode), but doesn't check for truncation</li>
<li... | https://security.stackexchange.com |
192,859 | [
"https://dba.stackexchange.com/questions/192859",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/46876/"
] | I have designed my tables in below manner.
<strong>Countries Table:-</strong>
<pre><code>PkId --- + Country Name --- + StatusFlag
1 | India | L
2 | China | L
3 | Sri Lanka | L
</code></pre>
<strong>StateNames Table:-</strong>
<pre><code>PkId --- + CountryFkId --- + ... | The table structure that your colleagues have suggested might be appropriate for a data warehouse, but it would typically not reduce I/O in an OLTP database.
Consider this--if you run a query for all of the customers in a city that returns 1,000 rows, with the denormalized table, the database engine will have to read ... | Your previous solution is much better. If you need to UPDATE the Mumbai tu Mumbay for example, you do only one operation in the enumeration table and no UPDATEs in the Fact table. And such a easy JOINs are not so expensive. Use correct INDEX and everything will be OK :-)
| https://dba.stackexchange.com |
110,933 | [
"https://chemistry.stackexchange.com/questions/110933",
"https://chemistry.stackexchange.com",
"https://chemistry.stackexchange.com/users/75725/"
] | what is meant by reporting result to the nearest 0.01 mg/L?
The test result in certificate show 7 mg/L showing no decimal point.
| Reporting to the nearest quantity means that you report as many decimal places of the quantity as suggested. This is a common analytical chemistry expression given in procedures or analytical protocols. For example, if we say weigh <span class="math-container">$\pu{5 g} \; \ce{KOH}$</span> to the nearest <span class="... | If the quoted value is 7 mg/l and there is no other information given, this means that we must assume that the value has been rounded and is thus between 6.5 and 7.5 mg/l, i.e. <span class="math-container">$7\pm 0.5$</span> mg/l.
If a result <span class="math-container">$X$</span> is given to nearest 0.01 mg/l or 1% t... | https://chemistry.stackexchange.com |
402,407 | [
"https://physics.stackexchange.com/questions/402407",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/65278/"
] | Consider two spacetimes with the same manifold $M$ but distinct metric $g,g'$. How do I identify a point $p \in M$ in two spacetimes? Specifically, if I give the coordinates of the point in one spacetime, can I find it in the other spacetime?
E.g. Let $M=\mathbf{R}^4$, If a point $p\in \mathbf{R}^4$ in Minkowski spa... | Both the quora answers are incorrect. The idea that "nothing happens" is incorrect for reasons I explain in great detail below. The idea that somehow Jupiter spreads itself across the surface of the Sun or directly influences the luminosity of the Sun by doing so is wrong on many levels as pointed out by Victor Toth on... | I would definitely lean towards "nothing" happening.
The "goes dark for 200 years" answer makes an awful lot of assumptions, some of which seem unfounded to me. In particular, it assumes that Jupiter will evenly spread over the surface of the sun, and will remain on top without mixing with the bulk of the sun.
At one... | https://physics.stackexchange.com |
245,488 | [
"https://physics.stackexchange.com/questions/245488",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/-1/"
] | I used to think that the padlock design of using many layers of metal stacked to form the main body was a cost-cutting consideration. This was my assumption before I came across the idea that it was really a way to make the lock stronger. It might have been from a TV commercial which showed a bullet penetrating a lock ... | The multi-layered structure protects against impact fracture.
If you hit an object very hard, you can create a crack; stresses will concentrate at that crack, and make it easier for the crack to propagate (think of the little notch in the ketchup packet: that's where you can tear the plastic...)
Now if you have a sol... | @Floris answer is great, but there is another characteristic of a laminated lock, compared to a solid lock, to consider.
A laminated lock, has as few as 4 pins (6 or 8 on larger locks) holding the laminations together. The pins are basically rivets that run from the top of the lock, through all the laminations to the ... | https://physics.stackexchange.com |
130,363 | [
"https://physics.stackexchange.com/questions/130363",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/56687/"
] | $E$ = $mc^2$
And also
$E$ = $hf$ (f - frequency)
And hence Einstein said $m$ = $hf\over c^2$
And so photons have mass
But later he also said
$M$ = $M_0\over \sqrt {1-v^2/c^2}$
Where if we put $v = c$ we get
$M = M_0/0 \leftrightarrow M=\infty$
And so photon travelling at the speed of light ($c$) have undefined... | <blockquote>
$E$ = $mc^2$
</blockquote>
A much better expression is $E^2 = (mc^2)^2 + (pc)^2$, where $m$ is the "mass" (also known as "intrinsic mass", also known "rest mass", but most physicists nowadays just use "mass") of the particle and $p$ is the particle's momentum. This reduces to $E=mc^2$ in the special cas... | <blockquote>
And so photons have mass
</blockquote>
No - photons don't have mass - they have momentum. And energy. But just because energy is equivalent to mass, doesn't mean they have mass. And they can only travel at the speed of light. A photon cannot travel at any other speed - so you cannot apply the Lorentz tr... | https://physics.stackexchange.com |
3,773,077 | [
"https://math.stackexchange.com/questions/3773077",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/804051/"
] | Let X be a rv such that <span class="math-container">$P(X = 2) = 1/4$</span> and its CDF is given by
<span class="math-container">$$F_{X}(x) =
\begin{cases}
0,& x< -3\\
\frac{3}{4}(x+3),& -3\leq x <2 \\
3/4,& 2 \leq x <4\\
\frac{3}{64} x^2,& 4 \leq x < \frac{8}{\sqrt{3}} \\
... | Just expand the determinant using the first column. You see quickly that you get a sum of <span class="math-container">$3$</span> odd integers. Hence the determinant is an odd integer.
For example one term would be <span class="math-container">$[(10)^{30}+5] [((10)^{8}+7)((10)^{15}+9)-((10)^{10}+2n)((10)^{6}+4)]$</spa... | To put it algebraically: you have a map <span class="math-container">$q$</span> from <span class="math-container">$\Bbb Z$</span> to the field <span class="math-container">$\Bbb F_2 = \{0,1\}$</span> sending even numbers to <span class="math-container">$0$</span>, odd numbers to <span class="math-container">$1$</span> ... | https://math.stackexchange.com |
53,609 | [
"https://dba.stackexchange.com/questions/53609",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/9461/"
] | I have a simple ksh script that executes db2 queries, such as
<pre><code>#!/bin/ksh
#some initialization
#step1,2,3
set -e
db2 -x "select * from table a "
#step4
</code></pre>
The main issue seems to be caused by the db2 command. If the query returns records the shell script works perfectly fine. But if the query re... | You should be able to create a stored procedure that executes your query to get the table names. Then you loop over the results and execute your effective date query for each table individually.
You might even be able to do this without wrapping it into an stored procedure.
| As Pointed by @PeterSchuetze,
In later versions of DB2 you might be able to use <strong>return_VARCHAR</strong> to inline DYNAMIC SQL directly in SQL
I tried in DB2 9.7, not working thought
<pre><code>--#COMMENT
--#COMMENT ----------------------------------------------
--#COMMENT --- ... | https://dba.stackexchange.com |
629,376 | [
"https://physics.stackexchange.com/questions/629376",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/295393/"
] | Till now I was silent because I thought the SI unit of pole strength to be Ampere-Second and due to everything in analogy with electrostatic, it was ok, but when I looked closely, it changed to Ampere Meter, so my question is the expression at that time,<strong>WHY?</strong>
| First off: <strong>there are no magnetic (mono)poles</strong>. As such, specifying units for quantities that don't exist is a rather futile (and not particularly well-defined) exercise.
That said, <em>if</em> there were magnetic monopoles, then you would expect that if you had two opposite magnetic monopoles of strengt... | I never came across this quantity, but I read that one can derive the units of pole strength by assuming that the magnetic force to have a form similar to Coulomb's Law:
<span class="math-container">\begin{equation}
F = \frac{\mu_0}{4\pi}\frac{m_1 m_2}{r^2}
\end{equation}</span>
where <span class="math-container">$m_1$... | https://physics.stackexchange.com |
35,678 | [
"https://electronics.stackexchange.com/questions/35678",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/10456/"
] | I'm studying digital electronics where the components ALU and multiplexer appear. To me the ALU seems like a multiplexer but it's not specifically mentioned that this is the case. Is it so, or why not?
| No, it's not a multiplexer. A multiplexer would select one of both inputs, in an ALU both inputs may be used simultaneously, depending on the pending operation.
ALU stands for Arithmetic and Logic Unit, and those are the types of operations it performs.
If the operation calls for a left shift of register R1, then t... | <blockquote>
To me the ALU seems like a multiplexer ...
</blockquote>
An ALU performs many tasks.<br>
A multiplexer essentially performs one task.
An ALU could be given a multiplexer function as one of it's features if desired.<br>
ie a multiplexer's capabilities <strong>may</strong> be a small subset of an ALU's... | https://electronics.stackexchange.com |
107,811 | [
"https://security.stackexchange.com/questions/107811",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/45880/"
] | I just started reading about cookies and all the ways I can get them wrong and allow cookies to be hijacked which allows attackers to do things like impersonate a logged in user.
I don't understand why this can't be solved by simply having the server add to each cookie a signature determined by the rest of the cookie,... | If the cookie gets stolen inside a public Wifi Hotspot all users of the Hotspot have usually the same public IP address. This means binding to an IP would not help against an attacker in the same local network.
Apart from that if the public IP of users changes like it is the case with moving between networks (Mobile,... | Steffen Ullrich is right about the dubious security gain. The reason we don't implement it in practice is due to the former prevalence of multi-homed NAT boxes where X computers would be reduced to N IP addresses (where X >> N). The side effect in the way this worked was the next request would come from a different IP ... | https://security.stackexchange.com |
211,908 | [
"https://stats.stackexchange.com/questions/211908",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/91762/"
] | My understanding of LATE was that it was the effect of a treatment on individuals who were induced to be treated by the experiment. That is, the effect on compliers. My understanding of Treatment-on-the-treated (TOT) is that it is the effect of individuals who are in the treatment group (which can include both indivi... | Writing out the estimands may help. With <span class="math-container">$Y$</span> as the observed outcome, <span class="math-container">$A$</span> is the treatment of interest, <span class="math-container">$Z$</span> is the instrument, and <span class="math-container">$Y^a$</span> is the potential outcome under treatmen... | LATE is a subset of TOT....I quote from Mastering 'Metrics by Angrist and Pischke:
"Researchers and policy makers are sometimes interested in average causal effects for the <strong>entire treated population, as well as in LATE</strong>. This average causal effect is called the treatment effect on the treated (TOT for ... | https://stats.stackexchange.com |
183,799 | [
"https://softwareengineering.stackexchange.com/questions/183799",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3660/"
] | Or more generally: to trigger compiler errors in test projects if something that can be checked at compile time is wrong?
| In principle, why not. A failed test is a failed test regardless of whether it happens at compile time or runtime. Compile time failures can also occur without an explicit static assertion.
On the other hand, if your unit tests are only executed infrequently (shame on you), say every few dozen check-ins, then a compil... | <strong>Yes, it is okay to use static/compile-time assertions in unit tests</strong>
In my experience, many developers don't the unit tests enough, although they may compile them. In a complex environment, it is not necessarily possible to run the unit tests on the build machine (environment setup, etc) but you could ... | https://softwareengineering.stackexchange.com |
103,766 | [
"https://physics.stackexchange.com/questions/103766",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/35595/"
] | For example, take a water bottle. Fill it with water and then turn it upside down.
Instead of flowing steadily downward, it gulps down in parts. Why?
| The gulping you describe is due to air being sucked into the bottle and temporarily halting the flow through the nozzle. When the bottle is filled with water, it is at a particular pressure. When you turn it over and some water leaves, the pressure is now lower in the bottle.
Once the pressure in the bottle is lower ... | The "gulping" is due to the sucked-in air forming a bubble on its way up and by this briefly blocking the bottleneck. The shape of the bottle is important here. You wont see any "gulping" using a top sealed tube.
| https://physics.stackexchange.com |
96,847 | [
"https://electronics.stackexchange.com/questions/96847",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/4096/"
] | I'm having trouble assigning variables to structs, particularly making an array of structs, with the XC8 compiler.
Example code below:
<pre><code>typedef struct p{
int id;
dateStamp start;
dateStamp stop;
int parent_id;
} period;
period p1 = {1, {0, 0, 0, 1, 1, 14}, {20, 0, 0, 1, 1, 14}, 1};
period p2 = {1, ... | This is a C problem.
<pre><code>period periods[3] = {p1, p2, p3};
</code></pre>
is invalid in C, as <code>p1</code>, <code>p2</code> & <code>p3</code> are struct variables, and not constants known at compile-time, therefore you cannot use them as initializers.
You may use macros to substitute the same constant v... | It seems changing the code to:
<pre><code>period periods[3];
periods[0] = p1;
...
...
</code></pre>
solves the problem - XC8 must not be able to deal with the shorthand.
| https://electronics.stackexchange.com |
3,994,060 | [
"https://math.stackexchange.com/questions/3994060",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/875689/"
] | Suppose we have that <span class="math-container">$\cos(\theta) = \sqrt{3} / 2$</span>. Now I know that I can find the value of <span class="math-container">$\theta$</span> easily by referring to a trigonometric table but I want to ask is there any other way to find it's value without the table ? A sort of relationship... | Without using the table you have to derive the values.
In general, you can build a construction of geometric shapes that demonstrate that the angle is a certain proportion of the angle swept out by a full revolution. Keeping in mind that the angle of a full revolution is known to be 360 degrees or 2π radians you can ob... | I think for your purposes,series expansion of <span class="math-container">$\cos^{-1}(x)$</span> would do :
<span class="math-container">\begin{align}
\cos^{-1}(x) &= \frac{\pi}{2} - \sin^{-1}(x)\\
&=\frac{\pi}{2} - \sum_{n=0}^{\infty} \frac{2n!}{(2^nn!)^2}\frac{x^{2n+1}}{2n+1}; |x|\leq 1
\end{align}</span>
Obv... | https://math.stackexchange.com |
615,522 | [
"https://math.stackexchange.com/questions/615522",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/17474/"
] | I have the sentence at the moment
<blockquote>
Notice that for all $c \in \mathbf{C}$ such that $W(cx) = |c|^{2} Wx$.
</blockquote>
which I do not like.
I mean to say that for all $c \in \mathbf C$ the equation is true.
Probably simply
<blockquote>
Notice for all $c \in \mathbf C, W(cx) = |c|^{2} Wx.$
</block... | My offer would be
<blockquote>
Note that $W(cx) = \lvert c\rvert^2 Wx$ for all $c \in \mathbf{C}$.
</blockquote>
| How about the following?
Notice that $A=B$ holds for all $C$.
| https://math.stackexchange.com |
352,791 | [
"https://softwareengineering.stackexchange.com/questions/352791",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/253350/"
] | Assume that I wish to perform an action on a string (e.g., print the string) if, and only if, the string first passes several tests. The tests are diverse (and may even be complex functions themselves), and "passing" a test may mean different things depending on the specific test. For example, some tests can be discret... | Time-to-market (TTM) is indeed an important factor for many businesses, especially startups. When it comes to software products, TTM translates into <em>continuous integration</em> and <em>continuous deployment</em>. The idea here is not that you ship buggy code, but that you ship fully working software on very regular... | CI/CD is indeed a fail-fast approach. I take slight issue with this:
"<em>he thinks it's ok to ship buggy code</em>"
I suspect what he actually means, is that it is <em>known</em> that the software may have defects but deploying it quickly means that issues will be found, reported and fixed far faster than traditiona... | https://softwareengineering.stackexchange.com |
200,029 | [
"https://electronics.stackexchange.com/questions/200029",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/49115/"
] | Something I was wondering about: Why is one still using transformers for vacuum tubes? I know that they need higher voltages than usual, but do they really need AC voltages? Or can't one simply use DC/DC converters to generate this high voltage? That would remove those ugly transformers, and just leave the tubes on the... | To complete Nils’ answer, in audio applications, transformers are needed to adapt the low speaker impedance (generally between 4 or 16 ohms) into a load suitable to power tubes (generally several kilo ohms). As the output power raise, the biggest transformers need to be. In the case of a single ended output stage, they... | Remember that the anode voltage is only a part of the voltages you'll need to supply a typical tube circuit.
Along with the anode voltages you'll also need a beefy supply for the heaters (usually 6.3V, several amperes) and often a second high voltage for the screen grids.
If you're designing with DC/DC converters you... | https://electronics.stackexchange.com |
8,838 | [
"https://astronomy.stackexchange.com/questions/8838",
"https://astronomy.stackexchange.com",
"https://astronomy.stackexchange.com/users/5504/"
] | First of all, I'm studying orbits for a hobby: world building. Unfortunately, my mathematical abilities approach a ridiculous low threshold, which means I am stuck with reading the simplest explanations, which in turn leave me asking tons of fairly basic questions.
Allow me to start with a simple point. I know that Ke... | You've been given an answer, and it's perfectly valid, but here's something from a different perspective (less strict).
A circle is really just a particular case of an ellipse. Take an ellipse, and change it, by moving its focal points closer together. When those two points coincide, what you get is a circle. It's sti... | <blockquote>
Why is it impossible for any planet (or moon, by the way) to orbit another body in a perfectly circular path?
</blockquote>
One way to look at it is from the perspective of probability and statistics. Think of position and velocity as random variables drawn from some continuous probability distributions... | https://astronomy.stackexchange.com |
547,063 | [
"https://physics.stackexchange.com/questions/547063",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/262240/"
] | If an object falls from <span class="math-container">$32.9184 m$</span> and a mass of <span class="math-container">$212.281 kg$</span> how hard does that object hit the ground? I somehow got <span class="math-container">$68,481.92N$</span> by using this formula I found: <span class="math-container">$$\frac 12 m v^2 = ... | Take <span class="math-container">$x = a\sin(\omega t +\phi)+x_0$</span> and differentiate once:<span class="math-container">$$ \dot{x} = —\omega a\cos(\omega t+\phi).$$</span>
Kinetic energy is <span class="math-container">$\frac{1}{2} m\dot{x}^2$</span> so it’s the same with or without shift.
Potential energy is <s... | The potential energy is <span class="math-container">$\frac{k}{2}(x-x_o)^2$</span> , the maximum x value is <span class="math-container">$'a+x_o'$</span> , this would suggest that maximum potential is still <span class="math-container">$\frac{k}{2} a^2$</span>
| https://physics.stackexchange.com |
1,472,495 | [
"https://math.stackexchange.com/questions/1472495",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/-1/"
] | I want to prove that $(x^q)' = qx^{q-1}, \quad \forall q \in \mathbb{Q}$ and $x \geq 0$.
Proving that $(x^n)' = nx^{n-1}, \quad \forall n \in \mathbb{N}$ and $x \in \mathbb{R}$ was an easy proof by induction.
But induction does not apply to this one. Hint is given that we can use the identity: $$u^m - v^m = (u - v)(... | \begin{align*}
\frac{x^{\tfrac nm}-a^{\tfrac nm}}{x-a}&=\frac{\Bigl(x^{\tfrac nm}-a^{\tfrac nm}\Bigr)\Bigl(x^{\tfrac{n(m-1)}m}+x^{\tfrac{n(m-2)}m}a^{\tfrac nm}++x^{\tfrac{n(m-3)}m}a^{\tfrac {2n}m}\dots+a^{\tfrac{n(m-1)}m}\Bigr)}{(x-a)\Bigl(x^{\tfrac{n(m-1)}m}+x^{\tfrac{n(m-2)}m}a^{\tfrac nm}+x^{\tfrac{n(m-3)}m}a^{\... | Consider writing $q=\frac{m}{n}$ for $m,n$ integers.
Define $y = x^{\frac{m}{n}}$. Then $y^n = x^m$
$\frac{d}{dx}(y^n) = ny^{n-1}\frac{dy}{dx}$ (since you know power rule it's true for integers), and similarly, $\frac{d}{dx}(x^m) = mx^{m-1}$.
Equating these two since they're the same:
$mx^{m-1} = ny^{n-1}\frac{dy}{... | https://math.stackexchange.com |
298,333 | [
"https://dba.stackexchange.com/questions/298333",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/114929/"
] | Running Oracle 11.2.0.4.0 on CentOS and discovered the hard drive filled up, giving error in alert log:
<pre><code>ORA-19815: WARNING: db_recovery_file_dest_size of 64424509440 bytes is 99.98% used, and has 10141696 remaining bytes available.
</code></pre>
The database was then issued a shutdown command and the alert l... | I would do something like the below example. Keep an integer (or bigint if you need it) as an identity column and the clustering key. This will keep the table neatly ordered with most recently added rows at the end, preventing fragmentation of your largest part of the table (the clustered index).
Then create a unique... | Generate new <em>sequential</em> GUIDs on the client end. This will reduce the frequency of page splits to a more manageable level.
In C# on Windows, the following will generate 100 sequential UUID values:
<pre><code>using System;
using System.Runtime.InteropServices;
namespace GUIDtest
{
class Program
{
... | https://dba.stackexchange.com |
168,414 | [
"https://physics.stackexchange.com/questions/168414",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/74571/"
] | Suppose a container is fitted with a massless and frictionless piston lying on a table such that pressure due to gas is greater than pressure due to external atmosphere. Hence piston will move.
Now the molecular motion of gaseous molecules inside container exert forces that will do "work" on the piston and correspondi... | Consider the forces acting on the piston. Since there is no friction, the only forces are $F_{\text{gas on piston}}$ and $F_{\text{atmosphere on piston}}$. So the net force on the piston is $F_{\text{piston, net}} = F_{\text{atmosphere on piston}} + F_{\text{gas on piston}}$.
Since the piston is massless, Newton's 2... | The keywords are <em>massless</em> and <em>frictionless</em>. A massless and frictionless piston is an idealization. When the atmosphere exerts a force on it, it is perfectly transferred to the gas, which isn't true with a massive piston. We can then calculate the work <strong>due to</strong> (but not <strong>from</s... | https://physics.stackexchange.com |
127,940 | [
"https://physics.stackexchange.com/questions/127940",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/56026/"
] | There have been quite a few plane crashes the past week and this question popped into my head of which I need a good explanation in science about the possibility of survival or not and why.
Assuming I am on a plane that is quickly losing altitude, just before the plane hits the ground I jump off the plane.
<ol>
<li>... | You can't jump very quickly. The average vertical jump of NBA players is 28 inches. How fast are they going at max?
$$v^2 = 2 a x$$
$$v = \sqrt{2 g (0.71m)}$$
$$ v = \sqrt{13.95m^2/s^2}$$
$$ v = 3.7 m/s$$
That's not very fast. It means that at a maximum you can remove less than 4m/s of your impact speed. Since a ... | You cannot jump from an object in free fall. The reason is this:
If you are standing on an object in free fall this means you are yourself in free fall. In that case the Normal force experienced by you is $0$ N. If the Normal force is $0$ N then you cannot exert a force on the object (hence the object cannot exert a f... | https://physics.stackexchange.com |
555,263 | [
"https://physics.stackexchange.com/questions/555263",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/236573/"
] | In the framework of relativistic quantum mechanics (not QFT) the Dirac equation in presence of external electromagnetic field is obtained by means of the minimal coupling, i.e. the substitution:
<span class="math-container">$$p_{\mu} \rightarrow p_{\mu}-eA_{\mu}$$</span>
This substitution is often motivated by saying... | You are missing the phase transformation of <span class="math-container">$\psi$</span>.
The Dirac equation is indeed not invariant to the
gauge transformation
<span class="math-container">$$A_{\mu}\rightarrow A_{\mu}+\partial_{\mu}\Lambda$$</span>
alone.
But it is invariant to the combined gauge/phase transformation
... | <blockquote>
What am I missing?
</blockquote>
You are missing the fact that a gauge transformation transforms <span class="math-container">$\psi$</span> as well. It changes the complex phase of the spinor at each point in spacetime. See if you can figure out how much of a phase change will leave the equation unchang... | https://physics.stackexchange.com |
279,984 | [
"https://electronics.stackexchange.com/questions/279984",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/135769/"
] | I am searching an suitable input and output capacitor (for example MLCC) for following Low Dropout Regulator (LDO): Analog ADP151.
The datasheet says that the ESR of the caps should be between 0.001 and 0.2 Ω.
I know the ESR vs. Frequency graphs on the capacitor manufacturer pages, but at which frequency do I have to... | Specification says, p.12
<blockquote>
"A minimum of 1 µF capacitance with an ESR of 1 Ω or less is
recommended to ensure the stability of the ADP151"
</blockquote>
and
<blockquote>
"Any good quality ceramic capacitor can be used with the ADP151, as
long as it meets the minimum capacitance and maximum ESR r... | ADP151 is an excellent regulator. Low noise, high PSRR...
I did transient response and impedance tests to check for output caps:
<ul>
<li>1µF MLCC X7R will work fine, like datasheet says.</li>
<li>10µF MLCC does offer improved transient response at minimal extra cost.</li>
<li>Going higher is only necessary for paran... | https://electronics.stackexchange.com |
633,440 | [
"https://physics.stackexchange.com/questions/633440",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/298007/"
] | I have a quick, silly question. If <span class="math-container">$\psi(x):=\langle x|\psi\rangle$</span>, does the bra <span class="math-container">$\langle x|$</span> 'go through' the <span class="math-container">$\partial_x$</span> operator, as in <span class="math-container">$$\langle x|\partial_x|\psi\rangle=\partia... | Sort of, yes. The correct expression is
<span class="math-container">$$
\langle x| \hat p|\psi \rangle= \frac{\hbar} {i} \partial_x \langle x |\psi \rangle,
$$</span>
which lots of people use the mnemonic <span class="math-container">$\hat p_x =\frac{\hbar} {i} \partial_x$</span> for, knowing what we all mean: the mom... | Just in case you find it useful, I'll give you an alternative way to do it. You have to use a bunch of book-keeping relations. Namely:
<ol>
<li>Completeness relation (for <span class="math-container">$p$</span> will suffice)
<span class="math-container">$$
I=\int dp\left|p\right\rangle \left\langle p\right|
$$</span>
(... | https://physics.stackexchange.com |
331,316 | [
"https://electronics.stackexchange.com/questions/331316",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/159021/"
] | If for example I have a 200VDC capacitor and I need to fully charge it to 200VDC. Can I do so with a 5VDC power supply and if I can how would I do this?
| One way I can think of is:
<ol>
<li>Use the 5 VDC power supply to build an oscillator.</li>
<li>Step up the resultant AC voltage using a 400:5 transformer.</li>
<li>Rectify the resultant output.</li>
</ol>
You'll now have a 200 VDC supply, which is capable of providing a lot less current than your original power supp... | Charge up 40 Caps to 5V with the supply while they are all in parallel with the supply, then disconnect them and put them in series. The voltages will add and 5V*40 = 200V
| https://electronics.stackexchange.com |
521,341 | [
"https://math.stackexchange.com/questions/521341",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/38296/"
] | I am having some trouble trying to find the single logarithm for the following:
$$\frac{1}{3} \ln(x+2)^3 + \frac{1}{2}[\ln x - \ln (x^2+3x+2)^2]$$
I understand that I have to use the addition and subtraction rules but the coefficients are confusing me. These are some of the steps I took:
$$\begin{align}
\frac{1}{3}... | $$\frac{1}{3} \ln(x+2)^3 + \frac{1}{2}[\ln x - \ln (x^2+3x+2)^2]$$
$$=\ln(x+2)+\frac{1}{2} \ln(x)-\ln(x^2+3x+2)$$
$$=\ln\frac{(x+2)(\sqrt x)}{x^2+3x+2}$$
$$=\ln \frac{\sqrt{x}}{x+1}$$
Properties of $\ln(x)$ that have been used :
$$a \ln(b)= \ln (b^a), ln(a)+ln(b)=\ln(ab)$$
| Hints: $a\ln b=\ln b^a$, $\ln a + \ln b = \ln ab$, $x^2+3x+2=(x+1)(x+2)$.
| https://math.stackexchange.com |
60,521 | [
"https://dba.stackexchange.com/questions/60521",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/27046/"
] | I have <code>table1</code> and <code>table2</code> in MySQL. Both have a primary <code>auto_increment</code> key <code>id</code>.
If the table schemas match and I do <code>INSERT INTO table1 (SELECT * FROM table2)</code> what happens with regards to the new rows inserted in to <code>table1</code>? Do they keep their ... | You can insert into an auto-increment column and specify a value. This is fine; it simply overrides the auto-increment generator.
If you try to insert a value of NULL or 0 or <code>DEFAULT</code>, or if you omit the auto-increment column from the columns in your INSERT statement, this activates the auto-increment gene... | The id from the select will be the same value inserted into the table. This will result in an error if you're trying to duplicate existing rows.
<blockquote>
<strong>Bill Karwin:</strong> Before you ask, there is no syntax in SQL for "select * except for one column".
</blockquote>
This can be achieved with some cr... | https://dba.stackexchange.com |
423,816 | [
"https://physics.stackexchange.com/questions/423816",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/-1/"
] | Why not free electrons in atom doesn't radiates em waves\photons, although they move with acceleration? Like 1s electron of Titan, it doesn't emits em waves, yes? Why?
| It's because the classical model of an atom as a little solar system simply doesn't work for atoms. That was the message of the quantum physicists starting with Bohr (1913) and Heisenberg et al (1925).
We don't know what an atom "looks like" inside. Hard little balls going in orbits? Um, we cannot watch them. Some qua... | The free electrons you refer to, are free electrons in a vacuum, not bount to atoms.
Now electrons in an atom are bound to the nucleus. These electrons exist as per QM at a certain energy level around the nucleus. Their wavefunction describes the probability distribution of their position for all of space. They do not... | https://physics.stackexchange.com |
249,258 | [
"https://physics.stackexchange.com/questions/249258",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/-1/"
] | I am a physics undergraduate student currently studying electromagnetics. I have previously studied electrostatics and magnetostatics yet the concept of scalar potential, $V$ and the vector potential, <strong>A</strong> have eluded me.
I understand Maxwell's equations and relevant formulas to calculate them in certain... | A wave function is a complex-valued function $f$ defined on ${\mathbb R}^1$ (if your electron is confined to a line) or on ${\mathbb R}^2$ (if your electron is confined to a plane) or ${\mathbb R}^3$ (if your electron ranges over three-space), and satisfying $$\int |f|^2=1$$ (where the integral is defined over the enti... | The wave function is the solution to the Schrödinger equation, given your experimental situation. With a classical system and Newton's equation, you would obtain a trajectory, showing the path something would follow: the equations of motion. For a quantum mechanical system you get a wave function, and the rules it obey... | https://physics.stackexchange.com |
308,762 | [
"https://softwareengineering.stackexchange.com/questions/308762",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/202968/"
] | My professor gave this example in a lecture:
<blockquote>
Example: Given an integer N, print out the values 1…N.
for (int i=1; i<=N; i=i+1) { System.out.print(i); }
</blockquote>
The professor said that the loop was O(n) because it printed the values 1 to N. However I thought that Big O Notation was a refer... | Your argument is totally wrong in an interesting way.
The time used is proportional to N. The input is N. But what is the size of N? For a 32 bit integer the size is 32 bits. For a 64 bit integer the size is 64 bits. For a k bit integer with a size of k bits, the value N can be as large as 2^k (almost) so the time is... | You've got two things going on here - You have a loop (the <code>for</code> statement) and you've got the inner statement of the loop (<code>System.out.print(i);</code>).
<pre><code>for (int i=1; i<=N; i=i+1) {
System.out.print(i);
}
</code></pre>
You want to start at the inner and work out. For this, <code>... | https://softwareengineering.stackexchange.com |
591,657 | [
"https://stats.stackexchange.com/questions/591657",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/369748/"
] | Disclaimer: not a statistics student, I am a civil engineering undergrad currently writing my thesis. And, I have never done a multiple regression analysis before.
Half of my study is cost estimation of a retrofitting project. I have a data set to use, albeit with just about 35 data points. My main adviser told me to u... | I would agree with your supervisor. That's good enough for the data you have and your knowledge.
However, its easy enough to run a multiple linear regression (even in excel if you enable/download the analysis toolpak)
then you would check for the significance of each coefficient (but would have to do some multiple tes... | <strong>One small tip here:</strong> Two of your variables (<code>total floor area</code> and <code>number of floors</code>) have a direct causal relationship that will make them strongly correlated. In order to reduce this collinearity I recommend you change the first variable to look at <code>average area per floor<... | https://stats.stackexchange.com |
258,060 | [
"https://softwareengineering.stackexchange.com/questions/258060",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/38616/"
] | I am writing a C API for retrieving data from a hardware device. The data will be returned as a string with approximately 30 bytes of text per item. The problem is there may any number of items. Could just 10 or there could be 10,000. So the returned data could range from 10 x 30 = 300 to 10,000 x 30 = 300,000 byte... | The cleanest way to do this is to essentially expose an iterator which the caller can use to pull one fixed-size item out at a time.
In C, this can be done like the <code>opendir</code>/<code>readdir</code>/<code>closedir</code> POSIX interface.
The first call allows the library to allocate some opaque iterator contex... | I'd recommend a look on your OSes APIs how to handle this. For the following example, I refer to the Windows API.
A number of functions with variable buffer outputs follow these rules:
<pre><code>int GetSomeString( char * pBuf, int nSize);
</code></pre>
Return value:
<ul>
<li>If called with <code>pBuf == NULL</cod... | https://softwareengineering.stackexchange.com |
61,536 | [
"https://physics.stackexchange.com/questions/61536",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/23328/"
] | So I have taken an introductory level quantum physics and am currently taking an introductory level probability class. Then this simple scenario came up:
<blockquote>
Given a fair coin that has been tossed 100 times, <em>each time landing heads</em>, would it be more likely that that the next coin flip be tails or h... | The physics aspect of your question is answered by saying that quantum mechanics doesn't change anything in this situation. The conclusions you get from basic statistics continue to be valid.
Now, as for <em>why</em> that is:
<blockquote>
I have a feeling that: $P(h | 100 h) < P(t | 100 h)$ because of the push t... | As you mention in your question, this is the definition of an independent event. If the coin is indeed fair, then it is irrelevant what has happened in the past in order to determine the probability of future events.
This does not change in quantum mechanics. In fact, QM gives us the first concept of truly random even... | https://physics.stackexchange.com |
40,327 | [
"https://dba.stackexchange.com/questions/40327",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/22150/"
] | <strong>Background:</strong>
I am programming a database in Ms-Access and using SQL-server as the Back-end. But since my database will be a multi-user platform I need to make sure that whenever a user is posting data into the back-end that their computer time is the same as the SQL-server time to ensure that record lo... | Unfortunately, you're trying to solve a problem with an inherently broken design: relying on a user-editable client-side variable to determine object version is never going to work perfectly.
Forcing time synchronization on the domain may <em>help</em>, but clients can still be out-of-sync, either because of clock dri... | The answer to your question is that yes, you can, provided that the users will have the necessary rights to update the time on their local machine. In your access front end, you would write some code to get the date/time from the SQL Server as in "select getdate()" and then you could use that to update the local time.
... | https://dba.stackexchange.com |
332,551 | [
"https://electronics.stackexchange.com/questions/332551",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/164632/"
] | In a car or motorcycle, the starter motor is switched by a relay. The relay coil is switched by a key switch or small pushbutton. All of it is a 12 volt DC system.
Is it correct to think of the relay coil as having a very large resistance, and the starter motor as having very low resistance?
I'm trying to build my (s... | You are correct.
The coil in the relay has many turns of thin wire and, as such, has higher resistance and draws much less current than the motor which has a few turns of fat wire with low resistance.
The relay is used so the switch can be smaller and won't burn out due to arcing. ALso so you don't have to run 1/4 i... | The electrical circuit which energizes the relay isn't the same electrical circuit which feeds the starter motor. The starter relay closes the contacts which complete the circuit which sends electricity to the starter solenoid. The starter solenoid is the bigger relay which closes contacts which feed electricity to the... | https://electronics.stackexchange.com |
285,607 | [
"https://physics.stackexchange.com/questions/285607",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/132722/"
] | If it were possible to fire a single Electron through a slit of exactly the same size, would there be zero interference at the detector?
| The first possibility is that the response of the probe is non-linear?
Another possibility is that there is an error in the way that you have interpreted the distance you measured between the led and the probe.<br>
What I mean is that is that there may possibly be a constant error at the probe end because you do not e... | LEDs can be pretty directional, so right there they are not point sources. A small incandescent filament should be a pretty good point source if the detector isn't too close and the glass around it doesn't add distortion.
I wouldn't expect the brightness vs distance to change that much because of this, but having str... | https://physics.stackexchange.com |
34,887 | [
"https://engineering.stackexchange.com/questions/34887",
"https://engineering.stackexchange.com",
"https://engineering.stackexchange.com/users/22829/"
] | I might be wrong here. The solid modeling done in CAD like Catia, NX, Solidworks,etc can be taken as input in CNC and the desired shape and size of piece can be obtained.The CAD itself convert the model into G -code.So why do we need to learn CNC programming if CAD can do it? Stay safe.
| Because some programs for some operations can be written quicker than the time it takes to produce the equivalent CAD file.
Also use of variables makes the program more useful ie a program to produce a cylinder can be written to take diameter as the controlling argument while producing many CAD files for various diff... | Well if engineers didn't learn G-code, why even learn what tool will be operated? Does it matter if its a lathe or mill or multi-axis something? It just produces a part that's an exact match of the CAD model, right?
I think however this assumes too much perfection and reality in the abstraction of a CAD model.
At th... | https://engineering.stackexchange.com |
60,406 | [
"https://chemistry.stackexchange.com/questions/60406",
"https://chemistry.stackexchange.com",
"https://chemistry.stackexchange.com/users/35151/"
] | I recently learned about orbitals in class, and I am really confused.
I am very confused about what the orbitals look like, what the signs (such as $-2s, ---2p$ etc.) mean and how they work.
What they taught us was how there are little spaces that the electrons can fit through, because they want to get to the center ... | First thing you need to understand is that orbitals are not actual physical things that exist. Simply put, an orbital is a function that describes the probability of finding the electron with certain energy at certain distance from the nucleus. The shapes of the orbitals are just the boundaries of space where you can f... | The hard part of quantum mechanics is that you can't know how everything is laid out. Elections fit into some distribution about the nucleus defined by the mathematical functions that are the orbitals. You can't practically know where they are per se, just where they are likely to be.
The traditional orbits you learn ... | https://chemistry.stackexchange.com |
69,078 | [
"https://softwareengineering.stackexchange.com/questions/69078",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/23071/"
] | I'm having a asp.net website running live with its specific style and specific content. From that site we've built another site with the same logic (in other projects) but with different style and different content (and different files) in the same solution. We've changed the start options from Default.aspx to the root... | Vim is a really good tool once you familiarize yourself with it.
It starts up faster than any IDE or text editor I've used, and it has syntax highlighting and it indents the code correctly in most cases.
It also helps you focus on the coding process itself, you won't be using the mouse at all to deal with it, that'll... | A programmer should not necessarily learn a lot of tools, but learn a few and learn them well.
Emacs and vim each have their distinct strengths but unless you use them a lot on a regular basis you will not benefit enough from them, I think. Especially not if you are a learning programmer.
You <em>will</em>, however ... | https://softwareengineering.stackexchange.com |
478,342 | [
"https://stats.stackexchange.com/questions/478342",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/292007/"
] | The regression model is:
<pre><code>y = b0 +b1x1 + b2x2 + b3x3 + e
</code></pre>
I want to test if <code>b1 + b2 > 0</code>.
the R package <code>car</code> has a function <code>linearHypothesis</code> that can test if <code>b1 + b2 = 0</code> by
<pre><code>linearHypothesis(lm_model, "b1 + b2 = 0")
</code><... | Doubtless there are packages to do it, but you could also try using the bootstrap, which will work for nearly arbitrary contrasts. Here's a simple implementation that gets a bootstrap sampling distribution for b2 + b1, from which the p value can be computed by asking what proportion of estimates are positive. To change... | You could bootstrap this. Example:
<pre><code>fit <- lm(Sepal.Length ~ Petal.Length + Petal.Width, data = iris)
sum(coef(fit)[c("Petal.Length", "Petal.Width")])
library(boot)
bootfun <- function(DF, ind, origfit) {
#bootstrap residuals:
DF$Sepal.Length <- fitted(origfit) + residuals(o... | https://stats.stackexchange.com |
219,956 | [
"https://security.stackexchange.com/questions/219956",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/55509/"
] | VPN companies tell us you're not safe if you're not using a VPN.
What I'm trying to understand is why, as a home user using the internet at large, a VPN into some VPN hosting company and from there out into the internet is any better (security wise) than going out into the internet from my ISP?
I understand that if I... | The assumptions here is that the VPN provider is running from a country that are one or more:
<ol>
<li>have more freedom than your own, especially if you live in oppressive or very conservative countries, your local internet provider or government may block content/site to materials that they do not want you to have ... | Most reputed VPN organizations have a "no log" policy and generally will encrypt your traffic.
If your ISP was hacked, your data such as Internet history would be directly traceable back to you, which is not the case if you use a VPN to browse the internet. Some countries even take torrenting seriously, so if you're ... | https://security.stackexchange.com |
129,505 | [
"https://softwareengineering.stackexchange.com/questions/129505",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/43243/"
] | Going by the general principle of data abstraction, I normally abstract data in a serialized format(JSON) and pass it as a parameter to the Business Logic(BL) modules such that the BL module always see a consistent format of the data irrespective of the underlying data storage layer. Even if I use a ORM, I use the seri... | A lot depends on your intention. Data serialization in this manner just to pass on to the business logic of a single application, seems wasteful, when you should be passing a native object from the ORM to the object encapsulating BL which will modify state and return the object to the ORM for persistence.
On the other... | Databases already provide a standard format for their responses and database drivers already know how to interpret/use them. The JSON marshalling and unmarschalling steps are therefore superfluous if the result in its format won't be transferred to another system.
In my opinion you should move more towards encapsulati... | https://softwareengineering.stackexchange.com |
7,118 | [
"https://physics.stackexchange.com/questions/7118",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/2609/"
] | This might be stupid, but is gravity a form of energy? And, if so, couldn't we use it for power?
| Gravitation is something that gives rise to a force. Like most forces, it can be put to work, just like in dams.
But gravitation is not energy: it's an interaction between physical bodies with mass.
NB: presence of mass warps space which affects the way massless things like light propagate. That does not mean that li... | Gravity is a FORCE (not ENERGY) that is very similar to that of mechanical spring and magnet!!! Here, we shall compare gravitational force with force exerted by mechanical spring as magnetic force can also be generated via electrical current.
Work has to be done on an object to lift it up and thus gaining potential en... | https://physics.stackexchange.com |
189,623 | [
"https://physics.stackexchange.com/questions/189623",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/70392/"
] | Consider the diagram below:
<img src="https://i.stack.imgur.com/yGI4V.png" alt="enter image description here">
It is 3 Stern-Gerlach apparatus along with some 'lenses' (illustrated here by lines).
<strong>Question</strong>
What would the output at A and B be?
<strong>Additional information</strong>
The problem w... | $\newcommand{\ket}[1]{\left| #1 \right>}$
Assuming that the lenses are some sort of a beam combiner and the vertical direction is $z$ (for convenience) and the I did the following:
After the second SG device the upper beam is in the state $\ket {x+}$ and the lower beam is in the $\ket{x-}$. Combining these two wit... | We should expect an output in both A and B. This is because (if I understand correctly what your "lenses" do) the first apparatus prepares a pure state spin-y-up, then the second SG produces output in both the positive and negative value for the spin along the x axis (because the two observables do not commute) and the... | https://physics.stackexchange.com |
31,317 | [
"https://engineering.stackexchange.com/questions/31317",
"https://engineering.stackexchange.com",
"https://engineering.stackexchange.com/users/22959/"
] | Example an aluminium tube reinforced with steel tube inside.
100*50*2mm thick aluminium with 80*40*3mm MS tube
| If we talk about quality and 6-sigma (which roughly means 1 ppm defects), the 1 ppm refers to test escapes, not test rejects.
Even if a part only costs \$1, if testing fails to catch a bad part and we accidentally send it to a customer, where it fails in the field, the eventual cost (in failure analysis, corrective a... | 1ppm is 4 times better than 4ppm. If 4ppm of parts are indicated it means that 0.0004% of these parts have to be discarded.
It is always better to have a lower number of discarded parts which means that 0.0001% of defects is better than having 4 times more. Lower ppm (in this case) means less costs and higher product... | https://engineering.stackexchange.com |
337,985 | [
"https://softwareengineering.stackexchange.com/questions/337985",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/256574/"
] | my question would be can age be considered a composite attribute? Because name is a composite attribute and it can be divided into first name, middle name and last name. And therefore can age be a composite attribute since you can divide it into years, months and then days?
| Can <em>age</em> be a composite attribute? No. age is a function of birthdate and now.
<pre><code>age = now - birthdate
</code></pre>
So, what about birthdate? Can it be a composite attribute?
Yes, it can, but it only makes sense to store dates as a composite in data warehousing situations.
Often, when warehousin... | Yes, you <em>can</em> store Age as a composite of year, month, date, hour, minute, second in the database if you want to.
However this is probably not a good idea in most cases, because Age can be derived from other values that are usually preferable to have stored in the database. The main reason is that it is better... | https://softwareengineering.stackexchange.com |
302,011 | [
"https://physics.stackexchange.com/questions/302011",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/129789/"
] | Let's talk about $Q = m c \Delta T$. Let's say I didn't know this equation by heart, but I naturally deduce it. How do I know which units to use (if I hadn't made myself clear, I mean units like Celsius or Fahrenheit)?
| The key to harmonic oscillation is starting with an equilibrium position (in your case, where the torsion balance is untwisted), and noticing that any displacement from that equilibrium produces a restoring force that is linearly proportional to the displacement. In your case, the displacement is the angle of twist, a... | Any dynamic system whose acceleration is negatively proportional to displacement will exhibit simple harmonic motion. Mathematically, harmonic motion is seen in any system with $$ \ddot{x} = -\alpha^2 x $$ where $\alpha$ is a constant (and I am using squares here to make sure the coefficient in front of $x$ is positive... | https://physics.stackexchange.com |
413,489 | [
"https://physics.stackexchange.com/questions/413489",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/139359/"
] | I am in a room which is heated up duringg day, in night outside temp is quite low, but my room with a ceiling fan running still feels hot as it was in day if I step outside door its cold. There is only one door and window to room.
Why room is not getting cold like outside?
Wont ceiling fan throw air and it will move o... | The perception of temperature is determined to air temperature but also by radiation temperature. The roof and walls of your room are heated up by absorption of sunlight during the day to a high temperature. This could easily reach 80 celsius. On the inside they will emit infrared radiation corresponding to this temper... | The structural components of the room (walls, floors, etc.) and, to a lesser extent, furniture and appliances, store heat. It could take quite some time for all this heat to go away. In the meantime, it'll keep the air in the room warm.
| https://physics.stackexchange.com |
382,632 | [
"https://physics.stackexchange.com/questions/382632",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/182869/"
] | Aside from the second law of thermodynamics it seems physics just doesn't care about the direction of time.
So does time really matter? What if instead of 3 spacial and one time dimension. 3+0 or 3+2. How would this affect physics?
| Using the Lie algebra valued function:
$$e_{\alpha} = e_{\alpha}^AT_A$$
We can write the covariant derivative components
$$D_{\alpha} = \partial_{\alpha} + \mathrm{ad}(e_{\alpha})$$
where, $ \mathrm{ad}(X) = [X, .]$ is the adjoint representation. Please notice that it is linear in the components of $e_{\alpha}$
Thu... | <blockquote>
The covariant derivative is defined as
<span class="math-container">$$
\begin{equation}
D = d+[e, \quad]\end{equation}
$$</span>
What shall I put in the commutator ? A random 1-form ?
</blockquote>
For the sake of generosity, let's look at an <strong>n-form</strong> <span class="math-container">$X$... | https://physics.stackexchange.com |
232,107 | [
"https://softwareengineering.stackexchange.com/questions/232107",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/43137/"
] | I see that some software have the version number included as a part of their file name, while others do not. I am more used to the latter type, and I think that is more popular, but I see the former type sometimes in javascript libraries. For example, jQuery's file name is like <code>jquery-2.1.0.js</code> instead of <... | <ol>
<li>It makes sense to specify the version you require. Behavior you may rely on could have changed, so newer is not always better. First, test whether a new version of a library works for you. Then, update explicitly.</li>
<li>In the case of web resources, having the version be part of the filename is important in... | (Excluding the situation of web caching mentioned by @amon): I assume you make a local copy of a third-party library for your program's use, otherwise the need for a version number would be obvious. The usage scenario of such a third party library within the software system you are developing may be one of these two:
... | https://softwareengineering.stackexchange.com |
83,159 | [
"https://dsp.stackexchange.com/questions/83159",
"https://dsp.stackexchange.com",
"https://dsp.stackexchange.com/users/59893/"
] | I'm doing an multichannel audio equalizer system on a chip, which is parametric EQ, usually implemented in cascaded biquad IIR filters.
My problem is that I use a lot of IIR filters due to multiple frequency bands (such as 10 bands), and I'm wondering if I should truncate the impulse response of IIR filters as an FIR a... | For a simple 10-band equalizer, it would be very hard to beat the IIR implementation. For most HW architectures the break-even point between direct FIR convolution and Overlap Add/Save (OLA) is somewhere between 64 and 128 taps and you seem to be still below this threshold.
The exact number of the break even point is ... | For medium-sized convolutions, the fastest algorithm is usually Karatsuba convolution.
This is essentially the same algorithm as Karatsuba multiplication, but with elementwise operations (add, subtract, shift) on vectors rather than normal operations on multi-digit numbers. Karatsuba convolution works with real numbers... | https://dsp.stackexchange.com |
278,507 | [
"https://math.stackexchange.com/questions/278507",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/51285/"
] | I am given 2 linear maps: $T,S$, both from $V$ to $V$, satisfying $T^2 = S^2$.
$T,S \ne id$, and $T,S \ne 0$.
The question given is: Does it necessarily mean that $T=S$ or $T=-S$? (or not both?). Prove!
I think that this is not necessarily true, but I can't find a counterexample to support my claim.
Any ideas? th... | It's not true. Let $V=\mathbb R^3$ and consider $T(x,y,z) = (x,-y,z)$, $S(x,y,z)=(x,y,-z)$. Now $S^2=T^2=I$, but $S\neq T$ and $S\neq -T$.
| No.
<strong>Hint:</strong> Think of operators defined by $Tv=Av,Sv=Bv$ for diagonal $A,B$ with $\pm1$ on the diagonal. Can you construct a counter example ?
| https://math.stackexchange.com |
471,980 | [
"https://physics.stackexchange.com/questions/471980",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/227934/"
] | I've been thinking about ways to cloak ships in space, since they all are warmer than their background they can be seen in the IR spectrum (given a large enough telescope).
So I was thinking, could you direct the waste heat in one direction, using a laser? For example, drive a heat pump where the hot side is a ruby cr... | <blockquote>
If microwaves only penetrate up to a few cm of food in a household
appliance
</blockquote>
It's important to understand <em>why</em> this is true.
Microwave ovens work because they are very carefully tuned to a very specific resonant frequency of water, 2,450 MHz. The microwaves generated by the magn... | Communication via microwaves doesn't necessarily take place on the same <span class="math-container">$2.5Ghz$</span> as our microwaves use, but use a multitude of different frequencies for different forms of communications. No communication takes place on a spectral line where there is a strong <span class="math-contai... | https://physics.stackexchange.com |
370,978 | [
"https://stats.stackexchange.com/questions/370978",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/223029/"
] | I have a (probably) biased coin. I want to make a Bayesian inference on <span class="math-container">$\lambda=p(coin=\text{heads})$</span>. I define my prior <span class="math-container">$p(\lambda)\sim Beta(\lambda; a=1,b=1)$</span>. I toss the coin and update my posterior by simply increasing hyperparameters of the B... | You can perform the Bayesian updating of the parameters as you would with an unconstrained <span class="math-container">$\lambda$</span>, then adjust the posterior to reflect the constraints by limiting the range of <span class="math-container">$\lambda$</span> to <span class="math-container">$[0.2,0.7]$</span> and ren... | '
The standard way to estimate <span class="math-container">$\lambda$</span> would be to just use the estimator, would it not? <span class="math-container">$p(\mbox{heads}) = \frac{\mbox{# of heads}}{\mbox{# of flips}}$</span>
"I toss the coin and update my posterior"
Or are you trying to come up with an update to yo... | https://stats.stackexchange.com |
1,401,353 | [
"https://math.stackexchange.com/questions/1401353",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/96627/"
] | According to <A HREF="http://mathworld.wolfram.com/En-Function.html" rel="nofollow">exponential integral</A> eqn. (8)
$\; E_{1}(x) \;$ can be represented by:
$$ E_1(x)= - \gamma - \ln(x) - \sum _{n=1}^{\infty } \frac{(-1)^n x^n}{n n!} $$
where $\gamma$ is the <A HREF="http://mathworld.wolfram.com/Euler-MascheroniC... | Let $A=\{1,2\}$ and $B=\{1,2,3\}$. Let be $f:A\to B$ and $f(x)=x$ for $x\in A$. A left inverse $g$ of $f$ must hold $g(1)=1$ and $g(2)=2$, but $g(3)$ can be $1$ or $2$. This gives exactly two possibilities for $g$.
Of course, if $A$ and $B$ are bigger, there can be many more possibilities. Note, nonetheless, that $f$ ... | Why not try $A$ as a single point and $B$ as something bigger? Then you should be able to mess around with $g$ some and not change anything about $g \circ f$.
| https://math.stackexchange.com |
378,879 | [
"https://physics.stackexchange.com/questions/378879",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/181020/"
] | In photoelectric emission,
"The number of photoelectrons emitted per unit area per unit time is directly proportional to the intensity of light used."
Is this true if the frequency is not held constant? If yes, please explain how.
If a light of frequency f and intensity I emits n photoelectrons from a metal surface(of ... | Yes, the number of photoelectrons is proportional to the light intensity. At a fixed frequency.
The rest of this question is impossible to answer. The workfunction threshold is given by the OP as $f/4$, so $f$ should be in the far UV. It is then likely that the photoelectric yield is higher at $f/2$. And that it woul... | <blockquote>
The number of photoelectrons emitted per unit area per unit time is directly proportional to the intensity of light used.
</blockquote>
is a correct statement. The frequency of the light is proportional to the energy of the light (through $E=hf$) and therefore only affects the kinetic energy of the phot... | https://physics.stackexchange.com |
427,186 | [
"https://physics.stackexchange.com/questions/427186",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/-1/"
] | Using Einstein's equation we can calculate the space-time curving(but I'm too stupid to do this). Hence, why everybody say that electron has no form\scale (although has spin at the same time)?
| The basic reason why, is that if you do this, and calculate the Schwarzschild radius of an electron, you discover that it's about $10^{-22}$ Planck lengths, if I'm remembering that right. Now the problem is that we understand that physics must be different at just one Planck length, because any photon with that wavelen... | First, not really mass, but <em>energy and momentum</em> curves spacetime.
Second, we'd have seen in the news if an electron's mass distribution (or charge distribution, for that matter) had revealed anything but point-like properties.
| https://physics.stackexchange.com |
166,697 | [
"https://electronics.stackexchange.com/questions/166697",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/73214/"
] | I'm looking at buying a new soldering station and trying to figure out what would be the right wattage. I'm going to soldering everything from electronic components (not much SMD, if any) to 16mm2+ cables.
Everywhere I look for recommendations everyone keeps warning about getting an iron thats too powerful. What I don... | At work, I have been using a solder station from Weller. It had a 80W iron, which was still very handy: Not longer that 18cm, a not too thick handle, and the heater was as thick as a pencil. The tip was exchangable, we had fine, needle-like tips for soldering SMDs as well as more bold ones for thicker cables like 2.5mm... | I'm afraid you won't be able to use the same tool to solder electronic components and a 16mm² cable.
For electronic components, any small soldering station like those from Weller or even a 30W iron without temperature control is enough.
For a 16mm² cable you will need a more powerfull iron, something like 100W, 150W.... | https://electronics.stackexchange.com |
46,558 | [
"https://mechanics.stackexchange.com/questions/46558",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/13825/"
] | I used to have a car (2011 Toyota Yaris) that had electronic headlight level adjustment with a knob on the dashboard. However, my 2016 Toyota RAV4 hybrid apparently has automatic adjustment, so there's no knob.
How can this automatic adjustment work? I mean, if it's based on gravity, the lights would be completely inc... | On some cars there is a sliding reference mechanism on the front suspension to recognise how much weight is added to the car behind the front wheels (as the front weight is effectively constant) - that is then used to drive the headlamp adjuster motors appropriately up or down.
| As far as I know, they work just as you surmised. A sensor detects the angle of the car body and electric motors adjust the headlights up or down to compensate.
| https://mechanics.stackexchange.com |
395,377 | [
"https://softwareengineering.stackexchange.com/questions/395377",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/342220/"
] | We have a large number of classes that is generated by JAXB. There are a couple that have identical fields and I want to see if there is a clean way to map class A to class B.
Example:
<pre class="lang-java prettyprint-override"><code>public static class ParentA implements ... {
public static class A implements... | <blockquote>
I consider an heresy to create a function, class, or attribute type, since they wouldn't be at the same logic-level than data types. This would also imply to have type type, which is even more confusing.
</blockquote>
Yet a <code>Type</code> type is a staple of almost all object-oriented languages, and ... | Many functional languages have simple solutions for describing function types. The most common is a syntax rougly like the following, which is used to describe the type of any expression:
<code>expr: a</code> where <code>a</code> is the type of the expression. If the expression has a type that is a function, it wil... | https://softwareengineering.stackexchange.com |
104,633 | [
"https://cs.stackexchange.com/questions/104633",
"https://cs.stackexchange.com",
"https://cs.stackexchange.com/users/99631/"
] | Let's say our Σ is 0 and 1. I want to disprove the following:
<blockquote>
There can be Turing Machines that accept only 1's, i.e. 1, 11, 111,
etc. Therefore, all languages that have strings of 1's are
recognizable.
</blockquote>
My first step to proving this is by providing a language such as <span class="math... | (I would post this as a comment but I need 50 reputation to comment... so...)
I think this might be solved using cardinality,<br>
You have <span class="math-container">$2^{\aleph_0}$</span> languages of such property (power set of <span class="math-container">$\{ 1^n | n>0 \}$</span>).<br>
While <span class="math-c... | <blockquote>
It isn't recognizable because it is infinite, therefore it'll loop infinitely. Does this work?
</blockquote>
No, because that claim is false. And your writing isn't at all clear, here. Recognizability is a property of languages, so your first two "it"s must refer to languages; but "loops infinitely" is ... | https://cs.stackexchange.com |
203,733 | [
"https://stats.stackexchange.com/questions/203733",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/40582/"
] | I’m trying to project new data into a space I created with icafast. The R package ica does not come with it's own predict function. Here is my attempt to do so. This is in vein of what I can do with principle component analysis (PCA).
<pre><code>########## PCA #############
library(stats)
data = replicate(10, rnorm(20... | <pre><code>predict.ica = function(new.data, ica.model) {
new.data <- scale(as.matrix(new.data), scale = FALSE)
Q = ica.model$Q
Y = tcrossprod(new.data, Q)
Y %*% ica.model$R
}
</code></pre>
You need to scale the data. I found this out by looking at the actual source for icafast
| The function above doesn't work correct! When you predict you should scale using the original data, not the data you're tring to predict ('new.data' in your case).
One simple example. Let assume that you want to get prediction for just one observation (i.e. one row). What would be the prediction?
<pre><code>> scal... | https://stats.stackexchange.com |
568,354 | [
"https://physics.stackexchange.com/questions/568354",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/236734/"
] | When we write kinetic energy for orbital mechanics, we usually write
<span class="math-container">$$ K= \frac{1}{2} m \dot{r}^2 + \frac{1}{2}m r^2 \dot{\phi}^2$$</span>
I understand the first term is the tangent velocity along the ellipse but what is the second term? My direct interpretation of it would be the energy ... | It's a consequence of expressing the speed, <span class="math-container">$v$</span>, in polar coordinates: <span class="math-container">$$v = \dot{r} \hat{r} + r \dot{\phi} \hat{\phi} \implies v^2 = \dot{r}^2 + r^2 \dot{\phi}^2.$$</span> If you want to make intuitive sense of what either term means, think of how positi... | If you write a position vector using polar coordinates like <span class="math-container">$$\vec{u}(t) = r(t) \left( \hat{x}\cos\phi(t) + \hat{y} \sin\phi(t) \right)$$</span> then the magnitude of the squared velocity is
<span class="math-container">$$
\begin{eqnarray}
||\dot{\vec{u}}||^2 & = & ||\dot{r} \left( ... | https://physics.stackexchange.com |
815 | [
"https://cardano.stackexchange.com/questions/815",
"https://cardano.stackexchange.com",
"https://cardano.stackexchange.com/users/1877/"
] | It's obviously a lot less than Ethereum's, but 0.17 ADA isn't insignificant. What are the main reasons it can't be 0.00017 ADA?
I understand that the parameters are configurable over time, but has it really changed since 1 ADA = $0.10 until now? How exactly have IOHK determined that 0.17 is the right amount for now? If... | If you have fixed market cap (45 Billion out of which 31 B in circulation) you need to have transaction fees to cover the cost of running the network (Stake Pool Operators and all people who are delegating their coins to the SPOs).
If you don't have fixed market cap you can afford to cover all the costs by fixed/dynami... | The transaction fee is a network parameter and is subjected to governance in the future. There is a cost for maintaining the network. Currently, there are more than 2500 stake pools that are providing the infrastructure for running Cardano.
Cardano also has a treasury that is powering innovation. Treasury is also paid ... | https://cardano.stackexchange.com |
3,697,095 | [
"https://math.stackexchange.com/questions/3697095",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/792106/"
] | Let S = Steve is happy, G = George is happy
<span class="math-container">$1. (S \lor G) \wedge (\lnot S \lor (\lnot G)) $</span>
One of Steve or George is happy and other is sad
<span class="math-container">$2. [S \lor (G \wedge (\lnot S)] \lor (\lnot G)$</span>
George is happy when Steve is sad or George is sad
<... | As we define that not happy if and only if sad, we have <strong><span class="math-container">$1.$</span> traslated correctly</strong>. But there are some ambiguity for the second one, for example
<blockquote>
(George is happy when Steve is sad) or George is sad <strong><span class="math-container">$($</span>Correct ... | <h1>1</h1>
Your answer is correct.
<h1>2</h1>
<span class="math-container">\begin{align} [∨(∧¬)]∨¬ & \equiv [(∨)∧(∨¬)]∨¬ \\ & \equiv [(∨)∧\top]∨¬ \\ & \equiv (∨)∨¬ \\ & \equiv ∨(∨¬) \\ & \equiv ∨\top \\ & \equiv \top \end{align}</span>
The... | https://math.stackexchange.com |
2,792,448 | [
"https://math.stackexchange.com/questions/2792448",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/458544/"
] | I'm having
<blockquote>
$$ f(x)=\frac{x-3}{(x+3)(\sqrt{x^2-4})} $$
</blockquote>
Now, if I want to find its <strong>domain</strong>,
I should write:
<blockquote>
$$ x+3 ≠ 0 \ \ \ \ \ \ \ \text{AND} \ \ \ \ \ \ \ \ \ (x+2)(x-2) >0
$$
</blockquote>
$ \text{as the denominator must be non-vanishing} \\ $
<ul... | Note, in the denominator :
$x \not = -3$ and the expression under the root must be positive, i.e.
$(x-2)(x+2)>0.$
1) The product is positive if both factors are positive:
$x-2 >0$ and $x+2 >0,$
$x>2$ and $x>-2$, hence $x>2.$
2) The product is positive if both factors are negative:
$x-2<0$ an... | Recall that
$$x^2-4>0 \iff (x-2)(x+2)>0 \iff \begin{cases}x-2>0 \land x+2>0\\\\x-2<0 \land x+2<0 \end{cases}$$
| https://math.stackexchange.com |
421,990 | [
"https://physics.stackexchange.com/questions/421990",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/150379/"
] | If I have a simple setup of a open circuit with a battery (constant battery) , resistor, and uncharged capacitor, and then I close the switch of circuit, and keep it closed until the capacitor is fully charged, what will happen with I open the circuit after a long time? Will charge be stored on the capacitor even after... | The previous answer is not correct, so I thought I'd correct it. While we often phrase naturalness in terms of the size of coupling constants, as these are what we usually work with mathematical, we could rephrase everything in terms of physical measurable quantities and the same considerations would still arise. So th... | The way I understand this both are just constraints for making a theory more appealing.
Dirac Naturalness:
Dirac naturalness basically describes the fact that we only keep the strongest couplings and then rescale the action by a choice of units such that the strongest coupling is unity. If the other couplings are much... | https://physics.stackexchange.com |
27,587 | [
"https://quant.stackexchange.com/questions/27587",
"https://quant.stackexchange.com",
"https://quant.stackexchange.com/users/22125/"
] | Let us assume that we have a foreign asset with volatility $\sigma_{ASSET}$. Now, I know that when pricing this under the foreign measure, I need to do a drift adjustment, namely $\sigma_{ASSET NEW}^2 = \sigma_{ASSET}^2 + \sigma_{FX}^2 +2\rho\sigma_{ASSET}\sigma_{FX}$.
On the other hand, I know that this can be FX hed... | Typically one only thinks about inflation delta in the context of an inflation derivatives portfolio. Then it is the sensitivity to a 1bp change in the zero coupon inflation rate for each maturity.
As others have mentioned, regular bonds are sensitive to inflation. However we typically describe that risk as a risk... | Inflation delta is typically used in the field of fixed income and is defined as sensitivity of the the present value of cash flows to the changes in the inflation curve. In business it is used to measure the inflation risk in the portfolio relative to the liabilities.
| https://quant.stackexchange.com |
164,334 | [
"https://mathoverflow.net/questions/164334",
"https://mathoverflow.net",
"https://mathoverflow.net/users/1302/"
] | Let us consider $X$ to be an Ornstein–Uhlenbeck process, i.e. the solution of $\text{d}X_t = \text{d}W_t - X_t \text{d}t$. We define $Y$ by
$$\mathbb{P}(Y\in \cdot):= \lim_{t\to+\infty}\mathbb{P}(X\in \cdot|\forall_{s\leq t}X_s \geq 0).$$
I expect that random variable $Y_t$ is well-concentrated, for example
$$\math... | One way to do it in a computational way is to use a representation as time changed Brownian motion $\{W_t\}$ and known results concerning Brownian motion.
Write $X_t=xe^{-t}+e^{-t}W_{u(t)}$ where $u(t)=e^{2t}-1$ and $x$ is your starting point, which of course you need to assume $>0$ (the result is not true for stat... | Started from a non-zero point, because the OU process started from 0 is symmetric about 0, I think it must enjoy a reflection principle about 0 only which should allow easy estimation of the probabilities.
| https://mathoverflow.net |
901 | [
"https://security.stackexchange.com/questions/901",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/426/"
] | Is it considered a <em>best practice</em> to alternate the vendor used to perform penetration tests? For example if it is your policy to conduct a third-party penetration test semi-annually you would have vendor A conduct the penetration test in the first half of the year and vendor B conduct another penetration test i... | Many (maybe most?) people consider rotating providers a best practice.
The most worthwhile benefit I typically hear is it enables you to compare the quality and value.
I also think there is room for you to be creative; for example, hiring a firm specializing in application penetration testing for one round followed ... | @Tate's answer is good on the benefit of rotating, but I'll point out another important point:
The disadvantage of rotating is that you lose a lot of the context and knowledge that your provider already built up. Both knowledge of your business context, requirements, custom rules, how the app works, etc, and histori... | https://security.stackexchange.com |
40,870 | [
"https://mechanics.stackexchange.com/questions/40870",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/15761/"
] | I just had the valves replaced on a cylinder head for a j20a DOHC interference engine.
I'm trying to align the camshaft sprocket to the markings on the cylinder head, but they snap back to where they were once I let go.
It's from .5 to 1 tooth off.
The question is, how many teeth is acceptable before you see valve... | In my experience, you get at least one or two teeth out before the engine is physically damaged. However, I would suggest you look into whether or not your engine should be temporarily fitted with a cam locking tool during timing belt replacement.
I'd also strongly advocate turning the engine over by hand prior to at... | given the word "interference" then I would assume that there is little or no room for error on the timing. Interference for engines tends to mean that the valves occupy the same space as the pistons at different times moving out the way as the other arrives. The springs closing the valves can cause the cam to rotate aw... | https://mechanics.stackexchange.com |
18,521 | [
"https://dba.stackexchange.com/questions/18521",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/9077/"
] | I have a database layout that is realy a mess and needs to be optimized. <strong>Does the layout of the database and some queries that are executed cause other queries to be slow too?</strong>
For example, an insert into table that has about 100 000 rows takes 9 seconds to execute. Could it be caused by a bad databas... | Yes, slow queries will cause other queries to be slow.
Server has only finite amount of IO it can do, if it busy doing heavy LIKE operation, like in your case, it can NOT use index it will make other queries slow.
| Yes, you need to rethink your schema and your queries.
foo LIKE '%...' -- cannot use an index on foo
9 seconds to INSERT one row -- other queries were hogging the table. (There are many possible explanations for how/why.)
Consider FULLTEXT instead of LIKE
Consider having a separate table with "tags". It will be m... | https://dba.stackexchange.com |
263,712 | [
"https://stats.stackexchange.com/questions/263712",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/150543/"
] | Can anybody please clarify what a surrogate loss function is? I'm familiar with what a loss function is, and that we want to bring about a convex function that is differentiable, but I don't understand the theory behind how you can satisfactorily use a surrogate loss function and actually trust its results.
| In the context of learning, say you have a classification problem with data set <span class="math-container">$\{(X_1, Y_1), \dots, (X_n, Y_n)\}$</span>, where <span class="math-container">$X_n$</span> are your features and <span class="math-container">$Y_n$</span> are your true labels.
Given a hypothesis function <span... | On a very general note, this function is used to penalize the misclassifications.
In the end, your aim is to classify the data in correct classes and to evaluate your results. To train the model you develop the loss functions and most frequently Mean Squared Error. But in MSE the accuracy may not reflect the true accur... | https://stats.stackexchange.com |
447,539 | [
"https://electronics.stackexchange.com/questions/447539",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/143383/"
] | Between the stator windings and rotor is a small air gap. What would happen if this gap were larger than it is? Surely the magnetic field set up by energizing the stator windings would still cut the rotor and induce an emf across it. So what effect does this air gap have on the performance of the motor?
| Air has a much higher reluctance (the magnetic equivalent of resistance) than the magnetic materials used in the motor. The smaller the air gap is, the lower that reluctance, and thus the higher the magnetic flux (which is the magnetic analog of current), allowing the motor to work more efficiently and at a higher powe... | Let's say you design a motor to operate at a given field strength. Most of the magnetic path reluctance comes from the air-gap. Therefore the larger the air-gap, the more H field and therefore length of magnetic material you need to establish the field, so the more expensive the motor is to make. The size and weight al... | https://electronics.stackexchange.com |
12,969 | [
"https://security.stackexchange.com/questions/12969",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/8612/"
] | I've bought something from an online store, and when entering the card details, it sent the details to their server through a HTTPS connection, which I then assume they forwarded to their provider - who that is I don't have a clue.
I've since read on their site and they do say that they'll store card details, but:
<o... | As far as I'm aware PCI-DSS doesn't cover permission of the user for storing data (depending on where you live something like the Uks Data Protection Act might). That said if a company is storing full track data (inc CVV2) they wouldn't be compliant with DSS. They may only store card details for the purposes of tracki... | PCI Requirement 3.1 requires card holders to keep card storage data to a minimum...
If it isn't a service that requires reoccurring charges or the like I think it would fall under more data than they should retain (for charge back tracking they can keep other data, hashes, partials, etc).
| https://security.stackexchange.com |
131,985 | [
"https://mathoverflow.net/questions/131985",
"https://mathoverflow.net",
"https://mathoverflow.net/users/7206/"
] | Is there a way to axiomatize [non-abelian] free groups in first-order logic using the language of groups (which contains the binary operation symbol $\cdot$, and the constant symbol $e$)?
Is there one particular axiom, or even a schema, from which we can prove that $G$ is a free group? (Regardless to the cardinality o... | The free groups cannot be axiomized by first order axioms. If the free groups were axiomatizable by first order axioms, then the ultraproduct of free groups would be a free group. However, the group $\mathbb{Z}$ is free, but for every non-principal ultrafilter $\mathcal{U}$ on $\mathbb{N}$, the ultrapower $\mathbb{Z}^{... | The surface group of genus $\ge 2$ has the same elementary theory as any free non-Abelian group. That follows from results of Kharlampovich-Myasnikov and Sela on the Tarski problem. In fact one can completely describe all finitely generated groups that are elementary equivalent to free non-Abelian groups. That class do... | https://mathoverflow.net |
193,827 | [
"https://stats.stackexchange.com/questions/193827",
"https://stats.stackexchange.com",
"https://stats.stackexchange.com/users/24515/"
] | I am reading a text on survival analysis (Smith's 2002 Analysis of Failure and Survival Data). All concepts like hazard function, survival function, density of survival variable $Y$ are rigorously defined. However, in an exercise (p.14) it says "Suppose that the death rate of a person that smokes is at each age twice t... | A rate has a specific definition of $\frac{\# \mbox{events}}{\# \mbox{person-years}}$. A risk on the other hand refers to a particular individual's risk of experiencing an outcome of interest, and it is risk which is intrinsically related to the hazard (instantaneous risk). The language the question uses is consistent ... | By "death rate", they essentially mean hazard rate. Death rates are often reported as deaths per 100,000 subjects per year, making the death rate proportional to the hazard rate, so they are not necessarily <em>exactly</em> alike.
In regards to the book, part "i" of the problem <em>is</em> quite easy as you said. Usin... | https://stats.stackexchange.com |
14,694 | [
"https://dba.stackexchange.com/questions/14694",
"https://dba.stackexchange.com",
"https://dba.stackexchange.com/users/7303/"
] | Let's say I have table of cars and table of car manufacturers. Each car references one manufacturer.
Furthermore, each car that has manufacturer <em>x</em> requires an extra field. Say, cars from that manufacturer have an extra feature that needs configuring that no other manufacturer provides.
Where does this field ... | What you are proposing is an entity subtyping approach. This would be one common solution to your design problem. Another would be Entity-Attribute-Value (EAV).
Type "subtype" or "EAV" into the search box in the top right hand corner of the page and you'll see many questions describing and discussing the relative pi... | The features data should really exist in a separate table. Normalize your data for maintainability and scalability. For instance, you could implement something like this:
<pre><code>create table Manf
(
pkManf int identity(1, 1) not null primary key clustered,
Name varchar(256) not null
)
create table Car
(
... | https://dba.stackexchange.com |
514,195 | [
"https://physics.stackexchange.com/questions/514195",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/141093/"
] | If A is a property of the fluid, then in a steady flow is <span class="math-container">$\frac{dA}{dt} = 0$</span> or <span class="math-container">$\frac{\partial A}{\partial t} = 0$</span> ? My professor says it's <span class="math-container">$\frac{dA}{dt} = 0$</span> but I don't see how that makes sense. Isn't a flow... | I think you are correct if temperature is constant.
<strong>Time Independent Fluids</strong>
<blockquote>
This class of fluids is characterized by the fact that, provided the temperature of the fluid remains constant, the shear rate depends only on the shear stress and is a single valued function of it. Newtonian f... | I would argue that <span class="math-container">$\frac{\partial A}{\partial t}=0$</span> should be giving you time-independence in all fluid properties.
My idea here is that you can find a system in which the <span class="math-container">$v \partial_x v$</span>-part of the co-moving time-derivative <span class="math... | https://physics.stackexchange.com |
4,083 | [
"https://mechanics.stackexchange.com/questions/4083",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/2073/"
] | Twice now my car engine has stopped cranking mid start. It doesn't seem to be a power problem as the radio, wipers ... all seem to work. The ignition key simply doesn't do anything anymore.
In once case waiting a few seconds resolved the problem and it started right up. In another case I had to roll it down a hill ... | As starter motors get old they can require higher current in order to turn successfully, so despite you having no obvious power problem I would first check your battery - also because this is a simple thing to replace if necessary.
It could indeed be the starter solenoid, so having a look at both this and the starter ... | A loose battery terminal can exhibit the same symptom. Carefully check both ends of your main (thick) battery cables to ensure that they're tight and not overly corroded, etc.
| https://mechanics.stackexchange.com |
1,632,435 | [
"https://math.stackexchange.com/questions/1632435",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/309017/"
] | Given two assets that have expected excess returns of 7 and 4.
Also, given their expected co-variance matrix
$$
\begin{bmatrix}
2 & 1 \\
1 & 1 \\
\end{bmatrix}
$$
What is the maximum expected Sharpe ratio that you can achieve by combining two assets into a portfolio?
I appreci... | For fixed $i$,
$\begin{eqnarray}
\frac{(i+1)^3-i^3-1}{3}&=&\frac{i^3+3i^2+3i+1-i^3-1}{3}\\
&=&\frac{3i^2+3i}{3}\\
&=&i(i+1)
\end{eqnarray}$
So
$\begin{eqnarray}
\sum_{i=1}^ni(i+1)&=&\sum_{i=1}^n\frac{(i+1)^3-i^3-1}{3}\\
&=&\frac{1}{3}\sum_{i=1}^n[(i+1)^3-i^3-1]\\
&=&\... | $\sum_{k=1}^n k(k+ 1) = \sum_{k=1}^n \dfrac{(i+1)^3-i^3-1}3=$
$1/3[\sum_{k=1}^n (i+1)^3- \sum_{k=1}^n i^3 - \sum_{k=1}^n1]=$
$1/3[\sum_{k=2}^{n+1} i^3- \sum_{k=1}^n i^3 - n]=$
$1/3[(n+1)^3- 1^3 - n]=$
$1/3[n^3 + 3n^2 + 3n - n]=$
$1/3[n^3 + 3n^2 + 2n]=$
$n/3[n^2 + 3n + 2]=$
$\dfrac{n(n+1)(n+2)} 3$
| https://math.stackexchange.com |
2,231,720 | [
"https://math.stackexchange.com/questions/2231720",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/436248/"
] | $$f(x)= \frac{x^9 + 4 \exp(0.6 x)}{3 x^{12} + 2 \exp(0.6 x)}$$
At first, I took out the dominant terms and reduced to $2\exp(0.6x)$ and assumed the limit going to negative infinity was zero and positive infinity was infinity. However, when graphing I can see that the limit going to positive infinity is 2. How can I fi... | I'm not sure if there is a good answer to this question. Both definitions have their merits. Your definition is just a special case of the definition of the standard metric on $\mathbf{R}^n$. Namely,
$$ d_E(x,y)=\sqrt{\sum_{i=1}^n(x^i-y^i)^2}$$
where $x=(x^1,\ldots, x^n)$ and $y=(y^1,\ldots y^n)$. In this case, $\lver... | The definition for $|x|$ is naturally stated in terms of diferent conditions, depending whether $x \geq 0$ or $x<0$ because $|x|$ is distance from $0$ to $x$ and we agree that distance is always $\geq 0$.
The definition $|x|=\sqrt {x^2}$ is also fine because when we talk about square root we agree that square root ... | https://math.stackexchange.com |
64,239 | [
"https://mathoverflow.net/questions/64239",
"https://mathoverflow.net",
"https://mathoverflow.net/users/14574/"
] | Hello,
I have a trivial question, but I hope that you don't mind helping. I often get confused with basic definitions.
Let F be a p-adic field. Then (from what I understand) $C_c^{\infty}(F)$ is the set of functions $f: F \to \mathbb{C}$ such that $f$ is locally constant and $f$ has compact support. Is the locally c... | A function $f : F \to \mathbb{C}$ is said to be smooth provided that $f$ is invariant under translation by some open subgroup of $F$ (hence by some compact open subgroup). Notice that when $f$ has compact support, this is equivalent to requiring that $f$ be locally constant. I don't have time to cook up a counterexampl... | Smooth in this setting by definition means locally constant.
| https://mathoverflow.net |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.