text stringlengths 1 1.11k | source dict |
|---|---|
c, shell, posix
00331 static inline dns_rdatalist_t *
00332 newrdatalist(dns_message_t *msg) {
00337 if ( ... ) { ...
00339 goto out;
00340 } ...
00355 out:
00356 if ( ... )
00357 dns_rdatalist_init(rdatalist);
00358
00359 return (rdatalist);
00360 } | {
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newtonian-gravity, estimation, solar-system, tidal-effect, milky-way
So if our $\Delta r = 2 R_{E}$ and $r \sim 4 \times 10^{13} \ R_{E}$, then $\tfrac{ \Delta r }{ r } \sim 5 \times 10^{-15}$, i.e., we're getting into the rounding error level of small.
Even if we changed $\Delta r$ to correspond to Earth's orbit about the Sun (i.e., ~2 AU), $\tfrac{ \Delta r }{ r }$ only increases up to $\sim 10^{-9}$. | {
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"tags": "newtonian-gravity, estimation, solar-system, tidal-effect, milky-way",
"url": null
} |
reference-request, time-complexity, turing-machines
Is base conversion known to be computable in better than essentially quadratic time?
This question has been asked many times but every reference I can find is in a practical context. I have seen claims that it can be accomplished in quasilinear time, but I can't understand how this is supposed to work, in part because assumptions about the model are often unstated in such discussions. Base conversion can be done in time $O(M(n)\log n)$, where $M(n)$ is a bound on the time complexity of multiplication of two $n$-bit integers. (We assume that $M(n)$ satisfies usual regularity conditions: it is monotone, and $2M(n)\le M(2n)$.)
The standard divide-and-conquer algorithms are described e.g. in Brent&Zimmermann, Modern computer arithmetic, and go as follows: | {
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"tags": "reference-request, time-complexity, turing-machines",
"url": null
} |
python, parsing, python-2.x
tagname, tagdata = separate_tags(tag)
if tagname == PASSAGE_TAG:
# Create text string to be available for concatenating to later.
tagdata['text'] = ''
try:
data[tagname].append(tagdata)
except KeyError:
data[tagname] = [tagdata]
else:
if tagname in data:
raise ValueError(MULTIPLE_TAG_ERROR.format(tagname))
data[tagname] = tagdata | {
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"tags": "python, parsing, python-2.x",
"url": null
} |
ros, package
Title: ROS Answers SE migration: remove package
Hi
How can I remove a certain package which I just downloaded?
Soe
Originally posted by soetommy on ROS Answers with karma: 47 on 2011-04-19
Post score: 2
If you installed it using a Debian Package, just remove it using the same tool you used to install it (Synaptic, apt-get, aptitude...). If you checked out code from a version control system (Git, SVN...) or just downloaded it, you can just safely delete the directory.
Originally posted by Martin Günther with karma: 11816 on 2011-04-19
This answer was ACCEPTED on the original site
Post score: 6 | {
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organic-chemistry, physical-chemistry, biochemistry, alcohols
I noticed first of all that urine is not at all as sterile as people say that it is. The rate of growth of bacteria is relatively slow, but as a precaution, I found the need to use additional measures to prevent the growth of bacteria. I settled on the following method: I have two bottles and I add to each bottle about enough salt as can be soluble in the urine and sometimes maybe a little more. The one bottle then fills up throughout the day and is emptied, washed, and refilled with salt. The salt helps to kill the bacteria which would be lingering in the empty bottle. The next day, the bottle stays empty and the other is used.
I would add that I discovered that the bacteria (without the salt) does not usually grow unless the bottle is left with urine for two days. After this, however, that same bottle (without the salt) would retain the bacteria and immediately grow, if used again. | {
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homework-and-exercises, electric-circuits, capacitance, voltage
FYI - for some figures:
Before connection ($Q=CV$):
$C1=8μF$, $V1=200V$, $Q1=1600 μC$
$C2=4μF$, $V1=800V$, $Q2=3200 μC$
After connection: (charge redistributes according to each capacitance):
$Q1=3200 μC$
$Q2=1600 μC$
Potential difference across the combination (according to textbook, which doesnt make sense to me as per the above question I asked): $V=Q/C=3200/8=400V$
Whereas I thought the potential difference across the combination would be = potential difference across capacitor $1$ + potential difference across capacitor 2 = $400+400=800V$ When you connect two capacitors in parallel, two things happen:
(1) the capacitances $C1$ and $C2$ and the charges $Q1$ and $Q2$ add, i.e., $$C_p=C1+C2$$ and $$Q_p=Q1+Q2$$ | {
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c#, object-oriented
Title: Cats and Dogs at the Petshop I had a test before and had to do this task:
Create classes: Cat, Dog and Petshop. Types Cat and Dog have fields Name and Breed and method Introduce() which prints text "I'm (Name) of (Breed). I'm a cat (or dog)".
The class Petshop collects different pets in its container.
We may add new pet to container using method AddPet(), and we may display information about all pets by calling method IntroduceAll().
Which hierarchy of classes is the best solution of this problem?
Write short code to demonstrate your solution. Your code should include class (interface) aggregation, inheritance, should use .NET BCL collections or generics, and should implement exception handling.
My answer:
using System;
using System.Collections.Generic;
namespace ConsoleApplication1
{
interface IPet
{
string MyName { get; set; }
string MyBreed { get; set; }
void Introduce();
} | {
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c++, game-of-life, sfml
gol.hpp
#ifndef GOL_HPP_
#define GOL_HPP_
#include <stack>
#include <utility>
#include <SFML/Graphics.hpp>
typedef struct {
int live;
sf::RectangleShape shape;
} Cell;
typedef std::pair<int, int> CellChange;
typedef std::stack<CellChange> CellChanges;
class GameOfLife {
Cell* cells;
CellChanges changes;
int width, height, size;
int n_getIndex(int x, int y);
int n_countNeighbors(int x, int y);
int n_wrapValue(int v, int max);
public:
GameOfLife(int width_, int height_, int cellWidth, int cellHeight);
~GameOfLife();
void m_drawCells(sf::RenderWindow& window);
void m_drawCellChanges(sf::RenderWindow& window);
void m_updateCells();
void m_flipCell(int x, int y);
void m_randomizeCells();
void m_clearCells();
};
#endif
gol.cpp
#include <cstdlib>
#include <ctime>
#include "gol.hpp"
int GameOfLife::n_wrapValue(int v, int max) {
if (v == -1) return max - 1;
return v % max;
} | {
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newtonian-mechanics, forces, momentum, collision
However I can't figure out how to calculate a Force vector instead of a new velocity.
How do you get the force impressed by the wall upon the collision? Most formulas need a Dt parameter, the time the impact lasted: I don't know that, it should be obtainable with the ball characteristics. Given the mass m of the ball, the incident normal speed v, and the coefficient of restitution $\rho$, Then the integral of F over the duration of the collision $\Delta t$ is $$\int_0^{\Delta t} F dt = \frac{m(1 + \rho)v }{\Delta t}$$ assuning no rotational effects are incurred.
This follows from the fact that at any instant the acceleration of the ball away from the wall is F/m, so the integrated acceleration over the duration of the collision is the total change in normal velocity of the ball. Since the post-bounce velocity is simply the approach velocity times the coefficient of restitution, the total velocity change is as indicated. | {
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hand words - What you may need to know In this practice, you will use your Middle finger left, Index finger right, Ring finger right, Ring finger left, Index finger left, Thumb (left or right hand), Pinky right, Middle finger right and Pinky left to practice some randomly defined characters. Series Practice Exam w/ Answers (Answers are on. Absolute Ratio Test Let be a series of nonzero terms and suppose. Basic AC Circuits, Second Edition is a step-by-step approach to AC circuit technology for the beginning student, hobbyist, technician, or engineer. A similar analysis gives the result for f0; when x= 5, the series converges using the alternating series test. So, for example, page 73 will have a series of problems and blank space for the students to write in the solutions. org are unblocked. At , the series is. Just like alternating sequences, the terms of such a series usually have a factor of (-1) n or (-1) n + 1 or something like that. Then to find our approximation, we need to find n | {
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statistics, microarray, p-values
Combining microarrays and RNASeq is complicated, because the data have different dynamic ranges, and different biases. I think the best thing to do is to process the microarray data separately from the RNASeq data and generate two lists of biologically-interesting genes, then look at the set relationships (e.g. intersection, exclusion). | {
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civil-engineering
Title: What is this construction site jacuuzi for There is a large drilling crane or something, which is connected by a giant hose to a skip full of water (central skip, blue). It looks like a jacuuzi but I suspect they are using it for something else.
Perhaps it is not a jacuuzi? What is it for if not? It is likely to be tanks for drilling fluid (aka 'mud').
This is a slurry of various substances, such as bentonite clay suspended in oil or water which serves various functions. In particular it provides cooling and lubrication for the drill head and helps to clear debris created by drilling.
When drilling into pressurised oil and gas wells it also provide a hydrostatic head which resists the well pressure.
Typically it will be pumped down the centre of the drill pipe and returns up through the gap between the drill pipe and the bore.
Drilling fluid is usually made up on site as needed by mixing dry ingredients with oil or water plus any additional additives. | {
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quantum-mechanics, operators, conservation-laws, hamiltonian, time-evolution
To answer the second question we'll dive into the formalities. To any self-adjoint operator $A$ we can associate an one parameter group of unitary transformations $U_A(t)=e^{itA}$. For the Hamiltonian, we get $e^{itH}$ and this gives the time evolution of the system. That is, if in the time $0$ a system was in a state $\psi_0 \in \mathcal H$, the in a time $t$ the system will be on the state $\psi(t)=e^{-iHt}\psi_0$.
Now, suppose that $\psi_0$ is an eigenvector of $A$ and that $A$ commutes with $H$. We know that $[A,e^{-iHt}]=0$, so that $A$ commutes with $e^{-iHt}$ for all $t$. Now, note that
$$A(\psi(t))=A(e^{-iHt}\psi_0)=e^{iHt}A\psi_0= \lambda e^{-iHt}\psi_0=\lambda\psi(t).$$
Thus we conclude that the time evolution of eigenvectors of $A$ continue to be eigenvectors of A with the same associated eigenvalues. More generally, the probability of a measure of $A$ to lie on some subset $E \subset \mathbb R$ will not change over time. | {
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complexity-theory, turing-machines, reductions, satisfiability, nondeterminism
So my question is does $CNFSAT\equiv_PCNFFAL$? No, $CNFFAL\le_P CNFSAT$ doesn't appear to imply $CNFSAT\le_P CNFFAL$, as far as we know.
As you say, we know that $CNFFAL\le_P CNFSAT$ is true. However, $CNFSAT\le_P CNFFAL$ is true if and only if $P = NP$.
Consequently, the claim $CNFFAL\le_PCNFSAT\implies CNFSAT\le_PCNFFAL$ is logically equivalent to the claim that $P=NP$. There is no known proof that $P=NP$ (and many would consider it surprising if that is true). | {
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algorithm, swift
where Data is your data type containing a close property (which I
assume to be of type Double).
The next step is to define the up/downward movements as arrays
and to use a for-loop:
// Upward Movements and Downward Movements
var upwardMovements: [Double] = []
var downwardMovements: [Double] = []
for idx in 0..<15 {
upwardMovements.append(data[idx + 1].close > data[idx].close ? data[idx + 1].close - data[idx].close : 0)
downwardMovements.append(data[idx + 1].close > data[idx].close ? data[idx + 1].close - data[idx].close : 0)
}
The difference calculation can be simplified by using the max() function:
for idx in 0..<15 {
let diff = data[idx + 1].close - data[idx].close
upwardMovements.append(max(diff, 0))
downwardMovements.append(max(-diff, 0))
} | {
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fft, signal-analysis, noise, sampling, signal-detection
For this a 20 bit ADC is not really helpful: the quantization noise of the ADC as a noise density in a good receiver with appropriate front-end gain, will be significantly below the receiver front-end noise floor. However it can facilitate shifting receiver functionality such as gain control from the analog to the digital (so consideration to high number of bits is driven by the dynamic range requirements- what is the ratio of strongest signal to minimum discernable signal and how much of that gain control (AGC) is done in the analog?), but that isn't the driver here for optimizing the minimum discernable signal. A target minimum SNR must be specified (this could be derived directly from the minimum acceptable RMS error on the estimate of the amplitude for example), and from that the minimum number of bits is derived with consideration to sampling rate and the averaging details further described below. Any additional bits can then be used in place of analog gain control for varying | {
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"tags": "fft, signal-analysis, noise, sampling, signal-detection",
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computer-architecture, cpu, threads
Given a piece of sequential code, if we run N instances of it in parallel on N cores (on real, modern, typical, and not-particularly-high-end CPU models), should we expect any slowdown versus running only a single instance of that program on a single core? | {
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homework-and-exercises, rotational-kinematics
What I did was use the fact that $a = r\omega^2 = r[(2.44)(1.82)+8.35]^2 = 164r$. This answer is correct, however, I was just wondering about something.
Isn't the translational acceleration also defined as $a=r\alpha$, which follows from $v=r\omega$ by taking the time derivative of both sides. In this case, $a = 2.44r$, as $\alpha$ is a constant angular acceleration. So then is the answer $a = 164r$ or $a=2.44r$? Am I seriously overlooking something here? Neither result is correct, but both are part of the solution!
The angular motion is given by ($r$ is the radius and $\theta$ is a function of time):
\begin{align*}
\vec r &= r \begin{pmatrix} \cos(\theta) \\ \sin(\theta) \end{pmatrix}
\end{align*} | {
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electrons, quantum-spin, magnetic-moment, orbitals
Has anyone tried to incorporate the electrons magnetic dipole moment into the atomic orbital theory?
YES. They've tried and they've succeeded. The electron's spin magnetic dipole is a standard part of atomic physics and quantum chemistry. Anybody attempting to claim that this isn't the case is simply describing their own ignorance about atomic physics rather than the subject as it is known.
Also, to be crystal clear:
The effects are perfectly well-known and have been described for the past 80+ years, but still
The effects are weak, and they are secondary to all sorts of other interactions that happen in atoms, including: | {
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c++, template, signal-processing
Value operator()(Value sample) {
if (count_ != time_constant_) {
// branch avoids distortions for the first time_constant samples
sum_ += sample;
++count_;
} else {
// Main running branch: once system is "primed" with time_constant number of samples
// provides "approximately exponential damping" with the given time constant
// correct, and well defined, even with unsigned types
// but there remains is potential for overflow, if user choses a Sum type which cannot
// hold sample avg * time_constant
sum_ += sample - damped_value_;
}
// first static_cast suppresses -Wimplicit-int-conversion about very small types being
// implicitly promoted to integer then demoted back again to be assigned to a small Value
// type. | {
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c#, meta-programming, roslyn
var statement = root.FindNode(diagnosticSpan);
context.RegisterCodeFix(
CodeAction.Create(VSDiagnosticsResources.SwitchDoesNotHandleAllEnumOptionsCodeFixTitle,
x => AddMissingCaseAsync(context.Document, (CompilationUnitSyntax)root, statement),
SwitchDoesNotHandleAllEnumOptionsAnalyzer.Rule.Id), diagnostic);
}
private async Task<Solution> AddMissingCaseAsync(Document document, CompilationUnitSyntax root, SyntaxNode statement)
{
var semanticModel = await document.GetSemanticModelAsync();
var switchBlock = (SwitchStatementSyntax)statement;
var enumType = (INamedTypeSymbol) semanticModel.GetTypeInfo(switchBlock.Expression).Type;
var caseLabels = switchBlock.Sections.SelectMany(l => l.Labels)
.OfType<CaseSwitchLabelSyntax>()
.Select(l => l.Value)
.ToList();
var missingLabels = GetMissingLabels(caseLabels, enumType); | {
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and when to use it? You can verify the result using the numpy.allclose() function. Base object if memory is from some other object. \begin{bmatrix} I_{4} = Subtract 2.4 * row 2 of A_M from row 3 of A_M Subtract 2.4 * row 2 of I_M from row 3 of I_M, 7. $$In case you’ve come here not knowing, or being rusty in, your linear algebra, the identity matrix is a square matrix (the number of rows equals the number of columns) with 1’s on the diagonal and 0’s everywhere else such as the following 3×3 identity matrix. Python matrix determinant without numpy. Use the “inv” method of numpy’s linalg module to calculate inverse of a Matrix. See if you can code it up using our matrix (or matrices) and compare your answer to our brute force effort answer. I love numpy, pandas, sklearn, and all the great tools that the python data science community brings to us, but I have learned that the better I understand the “principles” of a thing, the better I know how to apply it. , T. Returns the transpose | {
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"url": "https://collegemajor.la/diana-chan-yzvutp/archive.php?id=inverse-of-a-matrix-in-python-without-numpy-f80b64"
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homework-and-exercises, tensor-calculus, vectors
Consider for example a 2D circular motion where $\vec{X}=(\cos t,\sin t)$. Given an instant of time, you can find the position uniquely. But given the position, you cannot find $t$ uniquely.
Also, note that $\mathbf{A}=\frac{\mathbf{V}\cdot\mathbf{V}}{\mathbf{V}}$ makes no sense (at least not in the usual sense of vector algebra), because the inverse of a vector is not a vector. In other words, vector division is not defined (again, not in the usual sense of vector algebra.) | {
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motor, mechanism
PS: I'm still designing this and I still need to start implementing Matlab or Simulink simulations. So I don't really know which rated torque will be required. I just need to decide on an actuation method to finish the design and move forward. Welcome to Robotics, kingKong. The problem you're facing is a common one - you need to specify the motors, but the motors you specify will add to the load and require larger motors, which add to the load, etc.
The general approach is to add some "headroom" to your design, such that each actuator is capable of meeting your performance requirements with maybe 60% or 75% of its rated capacity. This makes the process of iterative design go a little easier. | {
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motor, power, circuit, driver
A voltage clamp is a circuit used with a motor controller to divert excess energy away from the control circuitry and power supply to prevent damage. In the two applications discussed below a MOSFET is used as switch to divert excess power through a power resistor where it’s dissipated as a heat.
...
The primary purpose of a voltage clamp is to protect a motor
controller’s power supply from the regenerative power created when a
motor is stopped or slowed down quickly. A motor spins when power is
applied to it however it also acts as a generator when slowing down or
suddenly stooped. This energy opposes the flow of current to the motor
and is directed back to the motor controller and power source.
Switching power supplies are not designed to handle this power surge
and some batteries will also not tolerate the sudden inrush of
current. A voltage clamp detects this power surge as a rise in voltage
and sends the excess current to a resistor where it’s turned in to
heat. | {
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javascript, react.js, redux
usernameError={usernameError}
passwordError={passwordError}
passwordConfError={passwordConfError}
emailError={emailError}
disButton={isEnabled}
/>
</Fragment>
);
} | {
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energy, electricity, everyday-life, power, angular-velocity
Linear Torque - The segment CD is characterized by $ \boxed{T = T_C \left(1 - \frac{\omega-\omega_C}{\omega_D-\omega_C}\right)}$. Starting from $\omega_C$ and $t_C$ as calculated above the elapsed time is $$ t=t_C + \int_{\omega_C}^\omega \frac{I}{ T_C \left(1 - \frac{\omega-\omega_C}{\omega_D-\omega_C}\right) }\,{\rm d}\omega = \frac{I ( \omega_B^2+\omega_C^2)}{2 T_A \omega_B} + \frac{I (\omega_C - \omega_D)}{T_C} \ln \left( \frac{\omega-\omega_C}{\omega_D - \omega_C} \right) $$ Note that due to constant power $T_C = T_B \frac{\omega_B}{\omega_C}$.
The time to reach $\omega_D$ is infinite due to the fact that $
\ln \left( \frac{\omega-\omega_C}{\omega_D - \omega_C} \right) |_{\omega \rightarrow \omega_D} = \infty$ | {
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c#, wpf, mvvm, xaml
It Might Make more sense to create a:
MenuItem CreateMenuItem(string resourceName,Type type, AvailMenus item){}
then in your add and insert can both use it. Why bother? Well say you want to add a setting to each and every one of them later, or you change the way you construct one e.g change out the resource file call. it should be abstracted.
In the interest of saving you having a lot of messy constructors also using the Property initializer syntax might be cleaner.
new MenuItem
{
Title = resourceFile.GetString(Submenu4String),
Menu = typeof(Menus.MenuItems.Submenu4String),
AvailMenus = AvailWSMenu.Menu2
}; | {
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molecular-biology, dna, homework, cancer
prevented by not allowing the formation of a phosphodiester bond.
Cancer cells grow much more rapidly than most cells in the body. What would be the consequence of "inhibiting enzyme-mediated DNA ligation" and why might this be particularly deleterious in cancer cells?
I am really unsure on this one.
I have looked at the Wikipedia answers to this question and they are wrong. First question: | {
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S~ A ~9u.~p. Excel provides two worksheet functions for calculating correlation â and, they do exactly the same thing in exactly the same way! Excel CORREL function. Some of the worksheets displayed are The correlation coefficient, Grade levelcourse grade 8 and algebra 1, Work 15, Scatter plots, Scatter plots work 1, Scatterplots and correlation, Scatter plots and correlation work name per, Work regression. The correlation coefficient r is given by: r =. Four things must be reported to describe a relationship: 1) The strength of the relationship given by the correlation coefficient. yes because the plots on the data would be very close to each other almost creating a perfect line. O-Md . Test for the significance of the correlation at the .05 level of significance. Compute the correlation coefficient . Scatter Plot And Correlation Coefficient Quiz. Those are the two main correlation functions. The correlation coe cient ris given by: r= n P (xy) ( P x)( P y) q n P x2( P x)2. q n P y ( | {
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} |
matlab, filters, bandpass
However, even once you fix this problem, you still may run into trouble. You are specifying transition bands that have a width of less than 0.01% of your sampling rate. This is not going to be practical, especially as an FIR filter. I recommend that you consider a good low-pass filter followed by lots of down sampling. Then you will be able to realistically extract the band of interest. | {
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quantum-mechanics, statistical-mechanics, entropy, degrees-of-freedom, ground-state
Title: Ground state degeneracy Today, I have learned from Prof. Cramer's (univ. of minnesota) lecture that the ground state can have degeneracy.
and he showed entropy $S = k_{b} ~ ln_{}~ \bf{n}$ , if ground state is $\bf{n} $ - fold degenerate.
Since I started learning this newly, I couldn't resist myself from asking, | {
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refraction, geometric-optics
$$
\vec{v}=(v_x,v_y,v_z) \\
=v_x\hat{x}+v_y\hat{y}+v_z\hat{z} \\
=v_x\hat{i}+v_y\hat{j}+v_z\hat{k} \\
=v_x\hat{e}_1+v_y\hat{e}_2+v_z\hat{e}_3
$$ | {
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electromagnetism, waves, magnetic-fields, electric-fields, maxwell-equations
Title: Using "Maxwell's curl equations" to get $H_y = \dfrac{j}{\omega \mu} \dfrac{\partial{E_x}}{\partial{z}} = \dfrac{1}{\eta}(E^+ e^{-jkz} - E^- e^{jkz})$ I am currently studying the textbook Microwave Engineering, fourth edition, by David Pozar. Chapter 1.4 THE WAVE EQUATION AND BASIC PLANE WAVE SOLUTIONS says the following: | {
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classical-mechanics, lagrangian-formalism, action, variational-calculus, functional-derivatives
Given that a system with Lagrangian $\mathcal{L}(\mathbf{q}, \dot{\mathbf{q}}, t)$ has the coordinate $\mathbf{q}_1$ at time $t_1$, and the coordinate $\mathbf{q}_2$ at time $t_2$, there exists a unique 'extremal path' $\gamma(t_1, \mathbf{q}_1, t_2, \mathbf{q}_2; t)$ which makes the action functional
$$
\mathcal{S}[\mathbf{q}(t)] = \int_{t_1}^{t_2} \mathcal{L}(\mathbf{q}, \dot{\mathbf{q}}, t)\text{d}t
$$
stationary. In other words, $\gamma$ satisfies the Euler-Lagrange equations,
$$
\left.\left(\frac{\partial \mathcal{L}}{\partial q} -\frac{\text{d}}{\text{d}t}\frac{\partial \mathcal{L}}{\partial \dot{q}} \right)\right|_{q(t) = \gamma(t)} = \mathbf{0},
$$
and has $\gamma(t_1, \mathbf{q}_1, t_2, \mathbf{q}_2; t_1) = \mathbf{q}_1$ and $\gamma(t_1, \mathbf{q}_1, t_2, \mathbf{q}_2; t_2) = \mathbf{q}_2$.
Moreover, the existence of this function allows the velocity, momentum etc. to be defined at the endpoints, e.g. the momentum at $(t_2, \mathbf{q}_2)$ is
$$ | {
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and fun math activities use sigma notation uses the sigma notation to represent Finite Geometric series, used. Step ( 2 ) has a simple, yet sophisticated little proof limit! Online cool math has free online cool math games and fun math activities math... The original summation. ) is vital that you undertake plenty of practice exercises so that become! Establish some useful rules of practice exercises so that they become second nature closed under countable..... And series than changing the order and grouping of the sum is often 1 to Top page... Provides worked examples of typical introductory exercises involving sequences and series however, a sequence is listed using the n. Way: the summation notation is being used a natural break point in the expression of functions can into... Of page i would cheerfully read an article talking about the topic, i.e x is the first number the! Interpreting this notations, a sequence is a method used to write sets, often with... That your teacher | {
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"url": "http://zonasantos.com/bohai-sea-pflcbgm/sigma-notation-examples-e0b873"
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java, beginner
We are working on Java 8. Is there a better/shorter way to write it? OK, since it was requested in the comments, here goes
You can replace the for loop with a java 8 stream() of the EntrySet() collection of the properties map.
You can replace all the nested if statements with a filter() you can have your choice of separate filter()s for each if statement, or just concatenate all of them together with && operator.
after the filter(), you need to tell the stream to end (aka Short-circuit) by finding the first item that matches the filter.
The filter() operation returns an Optional since it is possible that no item satisfies the filter's predicate. in the question, it is required to take an action only if a match is found, so you can add an ifPresent() that takes a Consumer which does something to the matched item and returns void. ifPresent() does nothing if no item satisfies the filter's predicate. | {
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modulation, frequency-modulation, radio, interference
$$V_{out} = K_{0} + K_{1}V_{in} + K_{2}V_{in}^2 + K_{3}V_{in}^3$$
If you put signals into the system where
$$V_{in} = A_{1}\sin(\omega_1t) + A_{2}\sin(\omega_2t)$$
Then part of the third order outputs are:
\begin{align}3K_{3}A_{1}^2A_{2}\sin(\omega_1t)^2\sin(\omega_2t) = \frac{3}{2}&K_{3}A_{1}^2A_{2}\{[\sin(\omega_2t) \\&- \frac{1}{2}\big[\sin(2\omega_1 + \omega_2)t + \sin(2\omega_1 - \omega_2)t\big]\}\end{align}
and another
Generally it's explained that term $\sin(2\omega_1 - \omega_2)t$ accounts for intermodulation distortion that is difficult to filter because it is close to the desired signal. Also they show that if there is any amplitude variation on signal 1, that it can amplitude modulate signal 2, because
$$\frac{3}{2}K_{3}A_{1}^2A_{2}\sin(\omega_2t)$$
But I never see a discussion of an FM signal being cross-modulated onto another FM signal. It seems to me that if signal 2 is an FM signal as: $\sin\big((\omega_2 \pm \Delta\omega) t\big) $. then the cross modulating term: | {
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observational-astronomy
Title: What study profiles could land me the job of astronomer? I realize there are very few to none universities that offer direct specialization of astronomy. If I aspired to be make astronomy my career choice, I'd likely have to pick something like physics and specialize later - or something similar - but that's just my hunch, and I'd prefer to know for sure.
What educational and professional paths optimize one's education and skill set for the occupation of astronomer? How do I become one? What you need would be at least the following:
Physics: astronomy is physics in the end, and you'll need strong basis in physics;
Math: as for any good education in physics, you'll need a reasonable amount of math to be able to become an astronomer;
Programming: it's almost impossible nowadays to get away from it. Being an astronomer today implies lots of data processing (to reduce the data, to interpret it etc.), and it involves a lot of coding. | {
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java, algorithm, graph
public void bfs(int s, int v) {
Node[] N = new Node[row.length];
for (int i = 0; i < row.length; i++) {
N[i] = new Node(indexForName(row[i].vertexName), null);
N[i].color = "white";
N[i].d = 1000;
N[i].p = null;
}
N[s].color = "gray";
N[s].d = 0;
N[s].p = null;
Queue Q = new LinkedList();
Q.add(s);
while (Q.isEmpty() != true) {
int u = (Integer) Q.remove();
for (Node nbr = row[u].head; nbr != null; nbr = nbr.next) {
if (N[nbr.vertexNum].color == "white") {
N[nbr.vertexNum].color = "gray";
N[nbr.vertexNum].d = N[u].d + 1;
N[nbr.vertexNum].p = N[u];
Q.add(nbr.vertexNum);
}
N[u].color = "black";
}
}
System.out.println("Printing distances of nodes"); | {
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Incidentally, all of the above carries over beautifully to surfaces $M$ enclosing volumes in $\mathbb{R}^3$:
$$V(M + \epsilon N) = V(M) + \epsilon A(M) + \epsilon^2 \int_M H\,dA + \frac{\epsilon^3}{3} \int_M K\,dA$$ Where $V$ is enclosed volume, $A(M)$ is the surface area of $M$, and $H$ and $K$ are mean and Gaussian curvature. By the Gauss-Bonnet theorem, the integral in the last term is always a multiple of $4\pi$ and depends only on the topology of $M$.
Start off with a first principle proof that $\lim_{x\to 0}\frac{\sin x}{x}=1$ is true
(we only need to know that the derivative of $sin(x)$ at $0$ is equal to 1).
Using the notation from there, you divide the circle into a $2^n$-gon and approximate the area with $2^n$ times the area of the small isosceles triangle wedges, each with a vertex angle of $\frac{2 \pi}{2^n}$ radians:
$\tag 1 2^n .5 \; a \sqrt{r^2 - (.25) a^2}$ | {
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MATLAB. 1 Introduction to Monte Carlo Simulaion Monte Carlo Option Price is a method often used in Mathematical - nance to calculate the value of an option with multiple sources of uncertain-ties and random features, such as changing interest rates, stock prices or exchange rates, etc. Take, for example, the abstract to the Markov Chain Monte Carlo article in the Encyclopedia of Biostatistics. Monte Carlo -- a bit of history •Credit for inventing the Monte Carlo method often goes to Stanislaw Ulam, a Polish born mathematician who worked for John von Neumann on the United States Manhattan Project during World War II. Let us take a look at how this works with a simple Monte Carlo simulation. The algorithm, however, is very complicated, and the output does not appear to follow a predictable pattern. The higher probability is 15,000, but it can be somewhere between. Monte Carlo Monte Carlo is a computational technique based on constructing a random process for a problem and carrying out a | {
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convolutional-neural-networks
Title: Using CNN to identify buildings from aerial images I want to train a CNN (Vggnet) to identify different types of buildings from aerial images.
However seeing that a CNN "ignores" size, e.g. the same type of dog in one image can be large and small in another image but will still be classified as a dog.
My issue is that non-residential buildings are mostly larger than residential houses, now I want to use this property to distinguish between residential and non residential. Is this even possible? | {
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string-theory, supersymmetry, conformal-field-theory, compactification
Doesn't supersymmetry somehow constrain the possible interaction terms? And of course it is a CFT, so we know in principle how correlation functions look like, don't we? Do we know primary fields?
How does one compactify such theory on for example 3D manifold like $S^3$? As you have mentioned, it is widely believed that the 6d (2,0) theories do not admit a conventional description in terms of fields and an action. Therefore, it doesn't really make sense to ask about their "field content" or their "interaction terms." Rather, like any abstract CFT, the (local) data defining such a theory consists of a list of local operators organized in unitary representations of the conformal algebra $\mathfrak{so}(6,2)$ and their OPE coefficients. Since the (2,0) theories are in fact superconformal (the result of combining supersymmetry and conformal symmetry), their local operators must actually organize into unitary representations of the larger superconformal algebra $\mathfrak{osp}(6,2|4)$. | {
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of degree nif – f(αx,αy)=αnf(x,y)f(\alpha{x},\alpha{y}) = \alpha^nf(x,y)f(αx,αy)=αnf(x,y) where α is a real number. Learn more. Homogeneous definition, composed of parts or elements that are all of the same kind; not heterogeneous: a homogeneous population. homogeneous function (Noun) a function f (x) which has the property that for any c, . A function is said to be homogeneous of degree n if the multiplication of all of the independent variables by the same constant, say λ, results in the multiplication of the independent variable by λ n.Thus, the function: Definitions of homogeneous, synonyms, antonyms, derivatives of homogeneous, analogical dictionary of homogeneous (English) Step 1: Multiply each variable by λ: The idea is, if you multiply each variable by λ, and you can arrange the function so that it has the basic form λ f(x, y), then you have a homogeneous function. Homogeneous functions are frequently encountered in geometric formulas. Watch this short video for more examples. | {
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"url": "http://brumleysouth.com/i4gjwll/ccb615-homogeneous-function-definition"
} |
\bbox[yellow]{\#(\text{outcomes containing }HH\text{ in }3\text{ trials ending with }T)} \end{align*} Observe $$\bbox[pink]{\#(\text{outcomes containing }HH\text{ in }3\text{ trials ending with }HH)} = 2^1$$ and \begin{align*} \bbox[lightskyblue]{\#(\text{outcomes containing }HH\text{ in }3\text{ trials ending with }TH)} &= \#(\text{outcomes with }HH\text{ in }1\text{ trials}) \\ &= \#(\text{all outcomes in }1\text{ trials}) \cdot P(1) \\ &= 2^1 \cdot 0 \\ &= 0 \end{align*} and \begin{align*} \bbox[yellow]{\#(\text{outcomes containing }HH\text{ in }3\text{ trials ending with }T)} &= \#(\text{outcomes with }HH\text{ in }2\text{ trials}) \\ &= \#(\text{all outcomes in }2\text{ trials}) \cdot P(2) \\ &= 2^2 \cdot \frac{1}{4} \\ &= 1 \end{align*} So $$P(3) = \frac{\#(\text{outcomes containing }HH\text{ in }3\text{ trials})}{\#(\text{all outcomes in }2\text{ trials})} = \frac{3}{8}$$ | {
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python, c++, c++11, iterator, reinventing-the-wheel
Title: Python reversed in C++11 I was playing with some of the wonderful new C++11 features and tried to reimplement a function reversed that would behave just like the one in Python to allow reverse iteration on bidirectional iterables.
And to clarify since I'm been told that I was unclear, that reverse function would be used in range-based for loops. Also, I define an iterator as whatever satisfies the functions std::begin and std::end (ForwardIterator concept). I don't think I've got to explain what a bidirectional iterator is... :D
Here's my code:
template<typename BidirectionalIterable>
class ReversedObject
{
private:
BidirectionalIterable& _iter;
ReversedObject(BidirectionalIterable&& iter):
_iter(iter)
{}
public: | {
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java, comparative-review, exception
Title: One try with multiple catch blocks vs nested try I am creating program which will parse .csv file and I am using FileReader and Scanner classes from java API.
FileReader throws FileNotFoundException, IOException.
Scanner's method hasNextLine() and nextLine() throw IllegalStateException and NoSuchElementException.
Should I use 1 try and 4 multiple catch blocks? Or try block nested in another try block(which has 2 catch blocks) with 2 catch blocks?
Code 1:
import java.io.*;
import java.util.Scanner;
import java.util.NoSuchElementException;
import java.lang.IllegalStateException; | {
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astronomy, weather
In writing simulations to evaluate the effectiveness of different algorithms, I need to generate simulated seeing values. I have global statistics for the seeing at the site, but determining how the seeing changes over time is important. I'm not sure if this directly answers your question, but the Greenwood Frequency defines the speed at which the atmosphere changes substantially enough on a small scale that an adaptive optics system needs to adjust. Typical Greenwood frequencies are around 20Hz, meaning that the conditions in an isoplanatic patch of the sky change substantially enough to cause seeing problems around 20 times per second. | {
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is useful when discussing the characteristic of a ring used for credit recovery should you to. Given date 0 = 0 x 0 = 0 x 0 = [! Works for all modulus of 3 we make a clock with numbers 0, 1,.. Equivalence is written a ⌘ b ( mod 9 ) designed for independent learners the fourth of... Problem for which all known efficient algorithms use modular arithmetic programming languages ) is the fourth part the..., comprised of multiple elements interacting with each other, can be represented as networks “ odd/even ” rules this... Result in 7 + 8 = 15, but clocks wrap around '' every 12 hours to up. Discrete Math Differential Geometry Differential Equations number Theory Statistics & Probability Business Math Challenge Problems Math.. Discussing the characteristic of a Hida family once and for all to calculate within. A Hida family once and for all members of a Hida family once and for members. 22 modulo 4 is called our mod New from used from Hardcover please retry$! Definition of congruence also | {
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"url": "http://mongegant.cat/7zlvvxkk/jnclacc.php?id=modular-systems-math-d23313"
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142
Cha pter 3
Dete rminants last remaining clement. Thus there arc 11(11 - 1)(11 - 2)·· · 2· I = II! (II fac torial) permutations of S; we denote the set of all pennutations of S by S" .
EXAMPLE 1
Let S = (1. 2, 3) . The set S3 of all permutations of S consists of the 3! = 6 permutations 123, 132,213, 23 I. 3 12, and 321. The diagram in Figure 3. I(a) can be used to enumerate all the permutations of S. Thus. in Figure 3.I(a) we start out from the node labeled I and proceed along one of two branches, one leading to node 2 and the other leading to node 3. Once we arrive at node 2 from node I, we can go only to node 3. Si milarl y, o nce we arrive at node 3 from node I, we can go onl y to node 2. Thus we have enumerated the pcnnutfltions 123. 132. The diagram in Figure 3.1 (b) yields the permutations 213 and 231, and the diagram in Figure 3.1 (c) yields the pennutations 3 12 and 321
2~3
FIGURE 3 . 1
1~3
1 ~2
,II,
,I I,
,II,
('l
(b)
«l | {
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"url": "https://silo.pub/elementary-linear-algebra-with-applications-9th-edition.html"
} |
fluid-dynamics, vector-fields
The constitutive law of Newtonian fluids writes the viscous stress $\mathbb{S}$, as a linear function linear of the first-order space derivative of the velocity field,
so that, for homogeneous isotropic fluids, viscous contribution reads
$\mathbb{S} = 2 \mu \mathbb{D} + \lambda (\nabla \cdot \mathbf{u})\mathbb{I}$,
being $\mu$ and $\lambda$ the two viscosity coefficients, and $\mathbb{D}$ the velocity deformation tensor
$\mathbb{D} = \dfrac{1}{2}\left[ \nabla \mathbf{u} + \nabla^T\mathbf{u}\right]$.
We can manipulate the expression of the viscous stress to write it as the sum of its isotropic (proportional to the identity tensor) and deviatoric (trace free) contributions, as
$\mathbb{S} = 2 \mu \mathbb{D}^d + \left( \dfrac{2}{3}\mu + \lambda \right) (\nabla \cdot \mathbf{u})\mathbb{I}$,
being
$\mathbb{D}^d = \mathbb{D} - \dfrac{1}{3}(\nabla \cdot \mathbf{u})\mathbb{I}$.
This expression can be further simplified in two cases: | {
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c++, arduino
bool acceptNextPress,currentState,previousState,hiLoTransition,loHiTransition;
uint8_t pin;
uint32_t currentTime,previousTime;
const uint32_t DEBOUNCE_INTERVAL{10000}; // 10ms
};
CapSwitch.h
class CapSwitch
{
public:
// constructor requires touch-enabled pin number
CapSwitch(uint8_t _pin) : pin(_pin),THRESH(200){}
~CapSwitch(){}
void update(void)
{
int val = touchRead(pin);
static int idx{0};
buf[++idx%BUFLEN] = val; // update ring buffer
if (accept) { // queue empty
accept = false;
double avg = get_avg();
if (val - avg > THRESH) { bstate = false; } // cap. increasing
if (avg - val > THRESH) { bstate = true; } // cap. decreasing
hilo = prev_state && !bstate; // falling edge
lohi = bstate && !prev_state; // rising edge
}
prev_state = bstate;
} | {
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bond, theoretical-chemistry, orbitals, reference-request
The most prominent examples for $\pi$ bonds are probably ethylene, $\ce{C2H4}$, and acetylene, $\ce{C2H2}$.
A $\delta$ orbital has two nodal planes between the bonding partners. These are perpendicular to each other. The bond orbital is asymmetric with respect to both of them. As a result, it is $C_\mathrm{s}$ symmetric with respect to the bisecting mirror planes. The point group of this orbital is $D_\mathrm{2h}$. Therefore it has shares features with a $d$ orbital, hence $d$elta, $\delta$.
One example is the $\ce{[Re2Cl8]^{2-}}$ ion, see Wikipedia's quadruple bond.
I imagine two $f$ orbitals aligning with the bonding axis being simultaneously a $C_3$ symmetry axis, giving it an overall $D_\mathrm{3h}$ point group. Since there is no greek letter starting with an $f$, I think the logical thing would be to choose $\phi$ as it sounds a like. (I cannot be the only one thinking that.) | {
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electromagnetism, mass, charge, field-theory, point-particles
Is there any experimental evidence to support or suspect that the center of mass and charge of an electron must coincide?
Is there any mathematical proof that says the center of mass and charge of an electron must coincide? Or are they permitted to be separated? (By electric field equation from EM, it didn't give enough evidence to separate $E$ field with $G$ field. But I don't think it's the same case in quantum or standard model, i.e. although electrons are leptons, consider $uud$ with $2/3,2/3,-1/3$ charges.)
What's the implication for dynamics if the expectation of centers does not coincide?
Can the center of charge and center of mass of an electron differ in quantum mechanics? | {
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functional-programming
or can you use some trick so that you always have an identity value even if you don't know what it should be? | {
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black-hole, collision
[Space] is dragged into motion by the orbital movement of the black holes, and by their gravity and by their spins. This motion of space is depicted by silver arrows...
Just before things become quiescent, regions of space around the merging black holes extrude upward. (Actually, the extrusions seem to begin sometime before things get chaotic.) If "space" here is being represented like the rubber sheet analogy, what do these extrusions mean?
If gravitational forces create depressions in the sheet, then it seems to follow that those extrusions are anti-gravitational, which can't be right. Could they be regions where the equations modeling the black holes' interactions spit out nonsense? | {
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graph would look and what would be the new (transformed) function? Note how we had to take out the $$\displaystyle \frac{1}{2}$$ to make it in the correct form. Chart functions. For example, for this problem, you would move to the left 8 first for the $$\boldsymbol{x}$$, and then compress with a factor of $$\displaystyle \frac {1}{2}$$ for the $$\boldsymbol{x}$$ (which is opposite of PEMDAS). Domain: x-values, left-to-right, Independent variable Range: y-values, bottom-to-top, dependent variable. Even when using t-charts, you must know the general shape of the parent functions in order to know how to transform them correctly! And remember if you’re having trouble drawing the graph from the transformed ordered pairs, just take more points from the original graph to map to the new one! $$\begin{array}{l}x\to -\infty \text{, }\,y\to 0\\x\to \infty \text{, }\,\,\,y\to 0\end{array}$$, $$\displaystyle \left( {-1,-1} \right),\,\left( {1,1} \right)$$, $$\displaystyle y=\frac{1}{{{{x}^{2}}}}$$, | {
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to such a covariance matrix. – vak Jun 24 '09 at 12:27 | show 1 more comment. Sign in to answer this question. pdClasses, In that case, if S in the above decomposition is positive definite, then A is said to be a Cartan matrix. An integer in R consists of the whole number that can be positive or negative whereas a floating-point number includes real numbers. See help("make.positive.definite") from package corpcor. | {
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navigation, turtlebot
to
obstacle_layer: observation_sources: bump laser_scan
Originally posted by tjadhav with karma: 68 on 2017-09-15
This answer was ACCEPTED on the original site
Post score: 1 | {
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neural-networks, convolutional-neural-networks, tensorflow, datasets, optical-character-recognition
Title: Generate credit cards dataset for locating number region Currently I'm working on a project for scanning credit card and text extraction from cards. So first of all I decided to preprocess my images with some filters like thresholding, dilation and some other stuff. But it was not successfully for OCR of every credit cards. So I learned a lot and I found a solution like this for number plate recognition that is very similar to my project.
In the first step I want to generate a random dataset like my cards to locate card number region, and for every card that I've generated I cropped two images that one of them has numbers and another has not. I generated 2000 images for every cards.
so I have some images like this:
(does not have numbers)
(has numbers)
And after generating my dataset I used this model with tensorflow to train my network.
model = models.Sequential()
model.add(layers.Conv2D(8, (5, 5), padding='same', activation='relu', input_shape=(30, 300, 3))) | {
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thermodynamics, reversibility, adiabatic
When dealing with the Joule expansion, why is it now legal to use the first principle in the form $dU = \delta Q - P dV$ ? The Joule expansion is also associated with creation of entropy, meaning the term $\delta S_{creation}$ is not zero, and you cannot say $dU = 0$ if you start from the first principle with $T dS$.
Edit 2: I think all my problems boil down to what is explained in this post, provided by Chemomechanics (it is in a comment, I cannot accept it as best answer...) Adiabatic isn't enough, but full reversibility isn't necessary (although, in practice, it's usually the assumption people go for and it's fine).
You need $dU=-P\,dV$. The starting point is, for an adiabatic process:
$$dU=\delta W+\delta Q=\delta W$$
Assuming that work comes only from pressure forces this becomes:
$$\delta W=-P_\text{ext}\,dV$$ | {
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homework-and-exercises, general-relativity, metric-tensor, coordinate-systems
i.e. the line element in terms of the coordinate system $x'^a$.
I compared this to the general expression for the line element in Riemanniam manifolds
$$ds^2=g_{ab}(x)dx^adx^b$$
and realised that in my previously obtained expression for $ds^2$, terms like $g_{12}(x')dx'^1dx'^2+g_{21}(x')dx'^2dx'^1 $ are grouped into a single term which is $8x'^2x'^1dx'^1dx'^2$.
Is there a rule that states how I should distribute the $8x'^2x'^1$ term between the metric functions $g_{12}(x')$ and $g_{21}(x')$? It's simple: the metric is symmetric. $g_{12}$ and $g_{21}$ are equal, and each is equal to half the coefficient of $dx^1 dx^2$ in $ds^2$. In your example, to be extra clear you could write the relevant part of the metric as
$$8 x^1 x^2 dx^1 dx^2 = 4 x^1 x^2 dx^1 dx^2 + 4 x^1 x^2 dx^2 dx^1 = g_{12} dx^1 dx^2 + g_{21} dx^2 dx^1.$$
But we normally write just one combined term, because we know that the metric is symmetric. | {
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ros, rosservice, service, message
Title: service problem
Hi,
I defined a server called DetectsObs.srv
float32 x
float32 y
float32 theta
float32 threshold
---
Points obstacles
bool obs
bool processFinished
and two msg type
Point.msg
float32 x
float32 y
and Points.msg
Point[] points
I have a service whose response is obstacle_detection::DetectsObs::Response &res (obstacle_detection is my package) I want to set the field obstacles of my response but if I do
obstacle_detection::Point obstacle;
obstacle.x = 0;
obstacle.y = 0;
res.obstacles[0] = obstacle;
I get this error
error: no match for ‘operator[]’ in ‘res->obstacle_detection::DetectsObsResponse_std::allocator<void >::obstacles[0]’
What should i do to fix it.
Thank you in advance | {
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python, object-oriented, python-3.x, role-playing-game, abstract-factory
def inspect(self):
print(self.character.name)
print(self.character.attack_dmg)
print(self.character.health)
print("\n")
def attack(self, target):
target.character.health = target.character.health - self.character.attack_dmg
#Observable or so
class GameState:
def __init__(self):
self.characters = []
def register_character(self, character):
self.characters.append(character)
def show_characters(self):
list(map(lambda x: x.inspect(), self.characters))
class Orc:
def __init__(self,name):
self.name = name
self.attack_dmg = 50
self.health = 100
class Human:
def __init__(self,name):
self.name = name
self.attack_dmg = 45
self.health = 105
def Main():
game_state = GameState()
orc = CharacterFactory(Orc("Karcsi"),game_state)
#orc.inspect()
#orc.attack() | {
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particle-physics, kinematics, large-hadron-collider
I attach below a useful sketch from the PDG review on kinematics. As one can see, the min/max values at X/Y axes of the Dalitz plot are fully determined by the masses of the parent and children particles. | {
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java, mergesort, rags-to-riches
private static final double toMS(long nanostart) {
return (System.nanoTime() - nanostart) / 1000000.0;
}
private static final void testInt(String name, long count) throws IOException {
Path data = Paths.get("testSort" + count);
long start = System.nanoTime();
buildIntFile(data, count);
double buildTime = toMS(start);
start = System.nanoTime();
FixedRecordSortFile.sort(data, INTPARSER);
double sortTime = toMS(start);
start = System.nanoTime();
FixedRecordSortFile.checkSorted(data, INTPARSER);
double checkTime = toMS(start);
System.out.printf("Built %10d in %8.3fms, Sorted in %8.3fms, checked in %8.3fms%n", count, buildTime, sortTime, checkTime );
} | {
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"tags": "java, mergesort, rags-to-riches",
"url": null
} |
machine-learning-model, k-nn, self-study, non-parametric
Title: Logic behind the Statement on Non-Parametric models I am currently reading 'Mastering Machine Learning with scikit-learn', 2E, by Packt. In Lazy Learning and Non-Parametric models topic in Chapter 3- Classification and Regression with k-Nearest Neighbors, there is a paragraph stating-
Non-parametric models can be useful when training data is abundant and you have little prior knowledge about the relationship between the response and the explanatory variables. kNN makes only one assumption: instances that are near each other are likely to have similar values of the response variable. The flexibility provided by the non-parametric models is not always desirable; a model that makes assumptions about the relationship can be useful if training data is scarce or if you already know about the relationship. | {
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control-engineering, control-theory, signal-processing, frequency-response, nonlinear-control
So that leaves us with the Arduino issues. Most notably, a problem between 2 and 3. I dont know which Arduino you use, but something like an Uno might be troublesome. See suppose you want to measure at 1kHz (which might be fair), the USB transfer protocols might harm this sampling rate and make it impossible to continuously send data. Therefore, it is advisable to store the data in the Arduino and send it afterwards. Which leaves us with point 3: memory. The arduino is fairly limited in memory so how long can you actually measure and still store it?
Hope these provided some insights. Any questions are always welcome. | {
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acid-base, extraction
The question is:
Why does a weak base 'prefer' to deprotonate a stronger acid? Is it because, being a stronger acid, the carboxylic acid will have more anions in solution compared to the weaker acid, so the (relatively few) cations of the weak base will be more likely to find carboxylates than phenoxides? | {
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c++, template, cache
Is it really necessary for objects to remove themselves from the cache? What if you just let them destroy themselves naturally, and leave the empty weak pointer in the cache. Then your lifetime worries fade away. From time to time you can purge the cache of entries where expired() == true if you really want, and other functions of the cache will have to take into account expired entries (like size() for example). It even makes your cache more flexible, because if you're not using the deleter you allow the possibility of users providing their own.
I also question the wisdom of keeping the "creator" function object in the cache, for a couple of reasons: | {
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domain and range for functions, particular attention has to be paid on functions involving square root Question 6 PDF. The line is the graph of f (x) = mx + n. To find the domain, I need to To find the range is a bit trickier than finding the domain. The ranges of (f g)(x) in (g) and (h) are hard to nd because the functions produce graphs you may not have covered previously. Th e set of all inputs for a function is known as the domain of the function. The relations in Example 3 are a special type of relation called a function. Alternative: A function is one-to-one if and only if f(x) f(y), whenever x y. Explain why. • Answer all questions. Opening – The teacher will define a piecewise function, and go over Key Idea p. Worked examples and illustrations. Express answers in interval notation. We will prove this later on using the moment generating function. If you're in the mood for a scary movie, you may want to check. 51: Domain and Range 1 Name: _____ www. • Diagrams are NOT accurately | {
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c#, datetime, asp.net, entity-framework, asp.net-mvc
var firstitem = ctx.Logging.Where(x => x.Datatype == Datatype.Start).AsEnumerable().FirstOrDefault();
var midnight = new DateTime(firstitem.CurrentDateTime.Year, firstitem.CurrentDateTime.Month, firstitem.CurrentDateTime.Day, 00, 00, 00);
TimeSpan difference = (firstitem.CurrentDateTime - midnight);
var difference_after_midnight = (int)difference.TotalMinutes;
items.Add(new HeatMapViewModel
{
Latitude2 = firstitem.Latitude,
Longitude2 = firstitem.Longitude,
Difference = difference_after_midnight,
Date = firstitem.CurrentDateTime
}); | {
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Suppose the lottery sells $10,000,000$ tickets and draws two numbers as winners. The probability of any given ticket winning is then $\frac 1{5,000,000}$ but two tickets will win. The fallacy in your computation is assuming that the events of each ticket winning are independent. They are not. You are assuming they take each ticket and independently decide whether it wins. The probability of a winner is $1$. The probability that a given ticket will win is $\frac 1{5,000,000}$. You need to be careful with the question you are asking and the independence.
If two winners are guaranteed, the chance of exactly one in the first 9M is $\frac {9M\cdot 1M}{10M \choose 2}$ But if you don't know whether there is zero, one, or two in the first 9M it doesn't change the odds on the last 1M tickets. What new information do you have from the fact that 9M have been sold? – Ross Millikan Sep 1 '13 at 4:29 | {
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java, role-playing-game
So I've written a field class and a base class for all the entities that can appear on the field. It was a little bit more complex than I expected. I'd like to know if these two classes can be used as a starting point for representing the environment objects of the game, or if my code is inappropriate and should be improved, or even a completely different concept should be implemented.
Entity.java
public class Entity {
public String name;
public char symbol;
public boolean walkable;
// decides if entity can appear on several positions simultaneously
public boolean multifarious; | {
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that in our original graph, was at zero, zero. Now it is going to be at negative two, comma, five. So let's look for it, and it also should be flipped. So on the left hand side, we have the top part and on the right hand side, we have the part that goes lower. So let's see. So A, C, and B all have the left hand side as the higher part and then the right hand side being the lower part, but we wanted this point to be at negative two, comma, five. A doesn't have it there. B doesn't have it there. D we already said goes to the wrong direction. It's increasing. So let's see, negative two, comma, five, it's indeed what we expected. This is pretty close to what we had drawn on our own, so choice C. | {
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"url": "https://pl.khanacademy.org/math/algebra2/x2ec2f6f830c9fb89:transformations/x2ec2f6f830c9fb89:radical-graphs/v/graphing-square-and-cube-root"
} |
php, mysql
if($query){
echo "<meta http-equiv=\"refresh\" content=\"0;URL=test1.php\">";
}
}
?>
</body>
</html>
Revise 1: This is a extracted part of my program, however here is the definition of this function:
Having 3-5000 contact, to send emails them easier to group them to Distribution list.
So this part of the program provide 3 tables:
Distribution list | Members of selected group | People
you can make group names and can add people into it.
So basic functions that I wrote for this part:
new distribution list can be added
By clicking on any Distribution list you'll get the Members table ($_GET)
Also by clicking on Distribution list should be BOLD (class="bold") as highlighted
Selecting any members in the member list can be deleted (checkbox2_del())
From people list anyone can be added to the list | {
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Substituting $B=1-A$ we get \begin{align} A & = \frac12 + \frac12(1-A)\\ &= \frac12+\frac12-\frac A2 \\ \frac{3A}2 & = 1 \\ A & = \frac23 \end{align}
We get the same answer as the geometric series approach, but without the geometric series. And this approach works even when the sequence of events is too complicated to write the geometric series explicitly. For example, you can easily use this method to analyze the chance of winning a game of craps, but to sum an explicit series whose terms are the chance of winning on the $n$th throw would be very difficult.
- | {
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"url": "http://math.stackexchange.com/questions/834344/a-fair-coin-is-tossed-until-a-head-comes-up-for-the-first-time-the-probability"
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scattering-cross-section, weak-interaction
In your answer I see an analog. Although in the quantum world particles cannot be localized, nor their momenta measured with the same precision, something analogous happens. It is well known that wavelength plays an important role in collisions. Neutrons of low energy can scatter on atoms much like balls, and the more their energy approaches the keV range, at which their wavelengths are comparable to nuclear scales, the more they excite the nuclear energy levels and get captured, where nuclear resonances appear in the spectra.
So in the case of electron, only at energies high enough, and wavelengths small enough could it interact with the quarks. This also means that the appropriate timescales became relevant at these energies, since quarks are supposed to have a large momenta distribution inside protons, and at lower speeds the interaction would be similar to the fan blades example. | {
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human-biology, immunology, bacteriology, pathology, immune-system
This means that you can still experience some mild symptoms due to the invading pathogen.
The important take-away from all this, though, is that your immune response relies on structural "markers" on pathogens in order to recognize them. This is true for both innate and adaptive immune responses. If the physical/structural properties of a pathogen change (due to antigenic processes and mutations as mentioned above) your immune system will be slower (and possibly ineffective) in responding to an attack.
The result, then, could be another one of those sore throats...
Citations | {
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python, algorithm, graph
The crucial part here is adding a node when you see it the first time (even just as a target of a connection) and getting the same node back again when it already exists. For this I used dict.setdefault, which is functionally equivalent to:
if name not in graph:
graph[name] = Node(name)
node = graph[name] | {
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plant-physiology, ecology
Literature Cited
Coder, K.D. 2011. Trees & cold temperatures. Environmental Tolerance Series WSFNR11-12, Warnell School of Forestry and Natural Resources, University of Georgia, USA.
Tognetti, R. et al. 2011. Fifth international poplar symposium: Poplars and willows: From research to multipurpose trees for a bio-based society.
Whittaker, R.H. 1975. Communities and Ecosystems. MacMillan Publishing, New York, USA. | {
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graph-theory
Indeed, vertices in a sub-path induces an interval subgraph. So you can use standard interval models (the endpoints of the interval for a vertex $v$ are the indices of leftmost and rightmost bags that contain $v$) to construct the tight example easily. The graph given above have intervals:
[1,1], [1,2], [1,3], [2,4], [3,4],[4,4]. Likewise, you can construct for a subpath of length n: the basic idea is that each interval either starts from 1 or ends at n. | {
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ros, c++, c++11, ros-indigo
Following are the errors for reference -
In function ‘void diagnosticCallback(const DiagnosticArrayPtr&)’:
/home/default_ws/src/err_pack/src/errors_node.cpp:52:21: error: invalid use of ‘boost::detail::sp_array_access<diagnostic_msgs::DiagnosticArray_<std::allocator<void> > >::type {aka void}’
if (diags_msg[0].level == diagnostic_msgs::DiagnosticStatus::ERROR)
^
/home/default_ws/src/err_pack/src/errors_node.cpp:54:7: error: ‘errorcode’ was not declared in this scope
errorcode = NodeToErrorCode[diags_msg[0].name];
^
/home/default_ws/src/err_pack/src/errors_node.cpp:54:19: error: ‘NodeToErrorCode’ was not declared in this scope
errorcode = NodeToErrorCode[diags_msg[0].name];
^
/home/default_ws/src/err_pack/src/errors_node.cpp:54:47: error: invalid use of ‘boost::detail::sp_array_access<diagnostic_msgs::DiagnosticArray_<std::allocator<void> > >::type {aka void}’
errorcode = NodeToErrorCode[diags_msg[0].name]; | {
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The Euler numbers appear in the Taylor series expansion of the secant trigonometric function, and they also occur in combinatorics.
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Kings Park, New York ... and 23.4% are non-families. 20.1% of all households are made up of individuals and 10.6% have someone living alone who is 65 years of age or older. The average household ... | {
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} |
• Well, that is a nice observation, thanks for the answer @ParamanandSingh. – onurcanbektas Jul 17 '18 at 3:31
L'Hôpital's rule.
If you take a solution, with given initial conditions, for a differential equation where the two roots of the characteristic polynomial differ, and let one root approach the other, then the limit (using L'Hôpital) has that term like $xe^x$ in it.
Example. The differential equation $$y'' - (1+a)y'+ay=0,\quad y(0)=0, y'(0)=1\tag{$$1} $$with a \ne 1 has characteristic equation r^2-(1+a)r+a with zeros 1,a. The solution is$$ y = \frac{-e^x+e^{ax}}{a-1}\tag{$2$} $$Now set a=1 in (1) ... the differential equation$$ y'' - 2y'+y=0,\quad y(0)=0, y'(0)=1\tag{$1'$} $$has characteristic equation r^2-2r+1 with zeros 1,1. The solution is$$ y = xe^x\tag{$2'$} $$Note that, using L'Hôpital's rule, the limit of (2) is (2').$$ \lim_{a \to 1} \frac{-e^x+e^{ax}}{a-1} = xe^x . | {
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filters, audio, python, real-time
# Initiate PyAudio
self.pa = pyaudio.PyAudio()
# Open stream using callback
self.stream = self.pa.open(format=np_to_pa_format[self.input_array.dtype],
channels=1,
rate=self.sample_rate,
output=listen_output,
input=not listen_output,
stream_callback=self.pyaudio_callback,
frames_per_buffer=frame_count)
# Start the stream
self.stream.start_stream()
def processing(self):
'''
Returns true if the PyAudio stream is still active in non blocking mode.
MUST be called AFTER self.start_non_blocking_processing.
'''
return self.stream.is_active() | {
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It is worth to remark that the $\gamma$ term above is computed from the identity $\gamma = -\int_{0}^{\infty} e^{-x}\log x \, dx$, which you are already aware of. From this,
\begin{align*} \int_{\epsilon}^{\infty} \frac{1}{x^a + 1} \, \frac{dx}{x} - \int_{\epsilon}^{\infty} e^{-x} \, \frac{dx}{x} &= \frac{1}{a}\int_{\epsilon^a}^{\infty} \frac{1}{x + 1} \, \frac{dx}{x} - \int_{\epsilon}^{\infty} e^{-x} \, \frac{dx}{x}\\ &= \gamma + o(1) \end{align*}
and taking $\epsilon \to 0^+$ gives the result.
Using the quantity $c(f)$, you can compute various integrals (including all the integrals you have asked) together with some tabulated results for $c(f)$:
\begin{align*} c\left\{\frac{1}{(1+x)^\alpha}\right\} &= -H_{\alpha-1}, & c\{e^{-x}\} &= -\gamma, \\ c\left\{\frac{x}{e^x-1}\right\} &= 0, & c\{\cos x\} &= -\gamma, \end{align*}
where $H_n$ is the harmonic numbers. For instance, if $a > 0$ then | {
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Area of sector formula and examples- The area of a sector is the region enclosed by the two radius of a circle and the arc. Arc length . Area of a sector formula. Sector is the portion of a disk enclosed by two radii and an arc. Arc Length Formula - Example 1 Discuss the formula for arc length and use it in a couple of examples. The volume of the box is 300 cm3. C2 Trigonometry: Arc Length & Sector Area PhysicsAndMathsTutor.com Edexcel Internal Review 3 (a) Show that the surface area of the box, S cm . What is the formula to find the perimeter of a sector of a circle? The Area of a Segment is the area of a sector minus the triangular piece (shown in light blue here). So the length of the arc of the sector = 2 (pi)r* (theta/360). Therefore 360º = 2 PI radians. Arc Length = θr. Example: a) What is the length of the arc intercepted by an angle of 15° on a circle with radius 20 meters? Problem 7 : Find the radius of sector whose perimeter of the sector is 30 cm and length of the arc is 16 | {
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07 Yamaha R6
2. Where're the bounds?
3. Originally Posted by 07 Yamaha R6
hey, guys and gals,
just wanted to see if any of you can direct me towards the correct way of
approaching this problem.
the problem asks to find the arc length of y=e^2x
now ive obtained the derivative dy/dx to be
2e^2x and when I use the formula for finding the
arclength, I then have the integral:
√(1+(2e^2x )²) dx
next I use
u=√(1+(2e^2x )²)
so that if I square both sides I get:
u²=1+4e^4x then, to get du:
2udu=16e^4x dx
now i noticed that above in "u²=1+4e^4x " i could solve for
e^4x to =(u²-1)/4 so that in the equation,
2udu=16e^4x dx, i could also solve for e^4x dx=1/8udu, then substituting
the e^4x=(u²-1)/4 into e^4x dx=1/8udu to become
(u²-1)/4 dx=1/8udu then solving for dx, I found
dx=u/2(u²-1) du
so my question is what do you do next? I substituted back u and du
into the integral and get u²/2(u²-1) du but I dont know where to go from here. Can somebody please help? | {
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"lm_q1_score": 0.9744347905312772,
"lm_q1q2_score": 0.8162060335154897,
"lm_q2_score": 0.8376199633332891,
"openwebmath_perplexity": 2180.5133829531483,
"openwebmath_score": 0.9286529421806335,
"tags": null,
"url": "http://mathhelpforum.com/calculus/40415-arc-length-help.html"
} |
electrical-engineering, motors
The high startup current occurs because the wires in the armature windings appear almost as a short until they set up a magnetic field (become energized). The momentary high current doesn't last long enough to cause the breaker to trip or fuse to blow. There's a pretty good explanation here. So...the momentary high current causes a like momentarily high voltage drop which in turn causes the light to dim. | {
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electricity, plasma-physics
Humans and other assorted bags of ionic fluids are an odd case. Salt water does conduct, but most of the conduction takes place via large and heavy ions, rather than super light electrons. So, radio waves do affect us, but the ions move so little in most cases that there's no real signal above background heat vibrations. In contrast to plastics, however, this mechanism makes us very much susceptible to microwave oven levels of radio waves, which are powerful enough to cause strong heating via those vibrations.
Fluorescent compounds are another curious case, but in a quite different ways. They are mostly akin to plastics in that the majority of their electrons are very tightly bound. | {
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c#, performance, algorithm
return plNoBlobsOfIntersections.ToArray();
}
private Pixel[] FindBlob(Pixel StartingPixel, Pixel[] PixelArray)
{
List<Pixel> plBlob = new List<Pixel>() { StartingPixel };
List<Pixel> plPixelsToCheck = new List<Pixel>(plBlob);
while (plPixelsToCheck.Count > 0)
{
List<Pixel> plTempList = new List<Pixel>();
foreach (Pixel pixel in plPixelsToCheck)
{
Pixel[] paSurroundingPixels = GetSurroundingPixels(pixel, PixelArray);
foreach (Pixel p in paSurroundingPixels)
{
if (p != null && !plBlob.Any(bp => bp.X == p.X && bp.Y == p.Y) && !plTempList.Any(bp => bp.X == p.X && bp.Y == p.Y) && !plPixelsToCheck.Any(bp => bp.X == p.X && bp.Y == p.Y))
plTempList.Add(p);
}
plBlob.Add(pixel);
}
plPixelsToCheck.Clear();
plPixelsToCheck.AddRange(plTempList);
}
return plBlob.ToArray();
} | {
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"tags": "c#, performance, algorithm",
"url": null
} |
quantum-mechanics, hilbert-space, quantum-entanglement
To put it differently, the only quantum mechanics without entanglement is single-particle quantum mechanics. This has some interest - you can describe quantum cryptography, band theory, the hydrogen atom, and a few other things - but in essence, you have to impose that quantum mechanics does not apply any more once you have two particles which interact, which would be a rather artificial cutoff and, more importantly, make quantum mechanics a theory with rather limited applicability. | {
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"url": null
} |
a + ib = r eiθ , Exponential formwith r = √ (a2 + b2) and tan(θ) = b / a , such that -π < θ ≤ π or -180° < θ ≤ 180°. Get the free "Convert Complex Numbers to Polar Form" widget for your website, blog, Wordpress, Blogger, or iGoogle. Every complex number $$z$$ can be represented as a vector in the Gaussian number plane. The x is the real number of the expression and the y represents the imaginary number of the expression. Below is an interactive calculator that allows you to easily convert complex numbers in polar form to rectangular form, and vice-versa. Table of Contents. To enter the complex number in polar form you enter mcisa, where m is the modulus and a is the argument of number. Determine polar form of complex number without a calculator. Furthermore, the values of elementary complex … We can convert the complex number into trigonometric form by finding the modulus and argument of the complex number. This rectangular to polar form conversion calculator converts a number in | {
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"url": "http://diagramma.com.br/amish-oak-vlnacm/ec2dee-complex-number-to-polar-form-calculator"
} |
javascript, typescript, rxjs
Title: A custom RxJS operator which emits (and completes) once a condition has been satisfied for all previous values of the source The code is written in TypeScript.
export function waitFor<T, R> (
reducer: (acc: R, value: T) => R,
initial: R,
condition: (accumulated: R) => boolean,
): OperatorFunction<T, R> {
return (source$: Observable<T>) => {
return new Observable<R>((subscriber) => {
let accumulated: R = initial
return source$.subscribe({
next (value) {
accumulated = reducer(accumulated, value)
if (condition(accumulated)) {
subscriber.next(accumulated)
subscriber.complete()
}
},
error (error) {
subscriber.error(error)
},
complete () {
subscriber.complete()
},
})
})
}
} | {
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"id": 41463,
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"lm_name": null,
"lm_q1_score": null,
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"lm_q2_score": null,
"openwebmath_perplexity": null,
"openwebmath_score": null,
"tags": "javascript, typescript, rxjs",
"url": null
} |
below. The line is called the "directrix"; the point is called the "focus". Then from the definition of eccentricity, Figure 2-11. Here is a simple online Directrix calculator to find the parabola focus, vertex form and parabola directrix. . ax. A parabola is defined in terms of a line, called the directrix, and a point not on the directrix, called the focus. Students who took this test also took : Wintringham probability slightly harder Propability quiz (spinners, die, & dots) Wintringham sequences - rules Free Parabola Directrix calculator - Calculate parabola directrix given equation step-by-step This website uses cookies to ensure you get the best experience. Conic Sections: Parabolas, Part 5 (Focus and Directrix) Find the equation for a parabola given the vertex and given the focus and/or directrix. The focal chord is equal to 4a, where a is the distance from the vertex to the focus. If the hall below is 140 feet in length with 30 feet tall ceiling at its highest point. Finding | {
"domain": "true-fish.ru",
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"lm_name": "Qwen/Qwen-72B",
"lm_q1_score": 0.9830850906978876,
"lm_q1q2_score": 0.8336244549881283,
"lm_q2_score": 0.8479677526147223,
"openwebmath_perplexity": 373.28047375649123,
"openwebmath_score": 0.507796049118042,
"tags": null,
"url": "http://true-fish.ru/d1yul/directrix-and-focus-problems.html"
} |
ros-kinetic
Originally posted by Paul Sebastian with karma: 41 on 2019-10-08
This answer was ACCEPTED on the original site
Post score: 2 | {
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"id": 33856,
"lm_label": null,
"lm_name": null,
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"lm_q2_score": null,
"openwebmath_perplexity": null,
"openwebmath_score": null,
"tags": "ros-kinetic",
"url": null
} |
electric-circuits, electrical-resistance, batteries, light-emitting-diodes, short-circuits
Title: Why does the LED turn off if the high current is going through the short? None of the other questions related to short circuits seems to answer my question.
I understand how short circuits work theoretically, that if there is a path with no resistance in a circuit then all of the current would flow through the short, and not the rest of the circuit.
Applying Ohm's law V=IR:
5 Volts = Infinite Amps * 0 Ohms
- or -
5 Volts / 0 Ohms = Infinite Amps | {
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"tags": "electric-circuits, electrical-resistance, batteries, light-emitting-diodes, short-circuits",
"url": null
} |
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