text stringlengths 1 1.11k | source dict |
|---|---|
quantum-algorithms, programming, qiskit, qaoa
There are great tutorials solving interesting problems with qiskit, but all the approaches are how to solve one specific problem using one specific algorithm. For example, the max-cut tutorial doesn't use the QAOA, but it should be able to solve the problem just as well as VQE which is used. Are there no tutorials/resources on the general use of qiskit Aqua algos? (e.g. how to implement each algorithm, explanations on the required inputs, what happens to the underlying quantum computing structure, and the math behind it?) That tutorial was recently updated. In it you'll find a more familiar way to declare and execute algorithms.
ee = ExactEigensolver(qubitOp, k=1)
result = ee.run() | {
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quantum-field-theory, quantum-electrodynamics, renormalization, propagator
The four components of a Dirac fermion are associated with particles and anti-particles of both helicities but these are states of external particles. The propagator has to do with the field itself and there's only one Dirac field in your action. Said another way, the propagator has two indices which both run from 1 to 4 so the effects of particles and anti-particles are both captured. In other reading you might come across some "anti-propagators" but these refer to anti-time ordered fields and do not play a role in this formalism. You can try computing the Fourier transform of
\begin{align}
\left < T \left [ \psi_\alpha(x) \bar{\psi}_\beta(y) \right ] \right > = \left < T \left [ \bar{\psi}_\beta(y) \psi_\alpha(x) \right ] \right >.
\end{align} | {
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Then we have that
$b_{n+1} = \frac{1}{k} \left(b_{n} + \frac{{k-1}}{b_{n}}\right) < \frac{1}{k} \left(b_{n} +{{k-1}}\right)$
provided that $b_{n} > 1$. This is certainly true for $n=1$, and we would like to keep it that way.
So we have an upper bound $b^+_n$ given by the recursion
$b^+_{n+1} = \frac{1}{k} \left(b^+_{n} + {{k-1}}\right)$.
Clearly, if $b^+_{n} > 1$, so is $b^+_{n+1} > 1$, so our condition $b^+_{n} > 1$ holds for all $n$, starting with $b^+_{1} > 1$, and we can work with that upper bound.
Now apply again the contraction theorem. Convergence is globally established since the slope is $\frac{1}{k} <1$, and the fixed point can immediately by computed as $b^+_\infty= 1$.
Hence upper and lower bound converge globally to the same value $b_\infty= 1$, which establishes that the original series also converges, from any starting point, to $b_\infty= 1$. $\quad \Box$ | {
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"url": "https://math.stackexchange.com/questions/2419165/convergence-of-recursive-sequence-a-n1-frac-1k-lefta-n-frack"
} |
ros, navfn, global-planner
Originally posted by KruseT with karma: 7848 on 2012-10-10
This answer was ACCEPTED on the original site
Post score: 3 | {
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python, pathfinding, dijkstra
Title: Implementation of Dijkstra's algorithm in Python I have implemented Dijkstra's algorithm for my research on an Economic model, using Python.
In my research I am investigating two functions and the differences between them. Every functions takes as input two parameters:
F(a,b) and Z(a,b).
Every cell of the matrix is defined as: $$M[a][b]=|F(a,b)-Z(a,b)|$$
The purpose of this is to find the path of minimal difference between the equations that will be correct for every input a
Online implementations of Dijkstra's algorithm were all using weighted edges whereas I have weighted vertices.
Pseudo-code:
function Dijkstra(Graph, source):
create vertex set Q
for each vertex v in Graph:
dist[v] ← INFINITY
prev[v] ← UNDEFINED
add v to Q
dist[source] ← 0
while Q is not empty:
u ← vertex in Q with min dist[u]
remove u from Q | {
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java, object-oriented
private final ArrayList<Rent> database = new ArrayList<>();
/**
* Returns the element at the specified position in this list.
*
* @param index index of the element to return
* @return the element at the specified position in this list
* @throws IndexOutOfBoundsException if the index is out of range
*/
@Override
@NotNull
public Rent get(int index) { return database.get(index); }
/**
* Adds an object to the end of the database
* @param item the object to add
* @return index of the object
*/
@SuppressWarnings("UnusedReturnValue")
public int add(Rent item)
{
database.add(item);
return database.lastIndexOf(item);
}
/**
* Replaces an item on the specified index
* @param index index to replace the item at
* @param item item to replace to
*/
public void set(int index, Rent item) { database.set(index, item); } | {
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c#, async-await
Title: Running tasks in parallel I've just started writing asynchronous methods for the first time having watched some tutorials.
I have a method where I run two tasks in parallel (notifySales, insertDownload):
Task insertDownload = _downloadService.InsertDownloadRequestAsync(model, Request.UserAgent);
if (product.NotifySalesByEmail)
{
Task notifySales = _downloadService.EmailDownloadRequestAsync(model);
await Task.WhenAll(insertDownload, notifySales);
}
else
{
await insertDownload;
} | {
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slam, navigation, ros-kinetic, stereo-camera, rtabmap
<remap from="left/camera_info" to="/stereo_camera/left/camera_info_throttle"/>
<remap from="right/camera_info" to="/stereo_camera/right/camera_info_throttle"/>
<remap from="rgbd_image_raw" to="/stereo_camera/rgbd_image"/>
<remap from="odom_info" to="odom_info"/>
<remap from="odom" to="/stereo_odometry"/>
<remap from="mapData" to="mapData"/>
</node>
</group>
<!-- Visualisation RVIZ -->
<node if="$(arg rviz)" pkg="rviz" type="rviz" name="rviz" args="-d $(find rtabmap_ros)/launch/config/demo_stereo_outdoor.rviz"/> | {
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is obtained by exchanging the rows and columns. In linear algebra, the transpose of a matrix is an operator which flips a matrix over its diagonal; that is, it switches the row and column indices of the matrix A by producing another matrix, often denoted by A T (among other notations). That is, $$L^{T} = U$$ and $$U^{T} = L$$. In this section we have seen how to find out transpose of a matrix by using two methods one is by using the operator and the other one is by using transpose command. In other words, transpose of A[][] is obtained by changing A[i][j] to A[j][i]. D = diag(v) returns a square diagonal matrix with the elements of vector v on the main diagonal. In this Video we Find the Transpose of a Matrix Using Excel. where S † is a diagonal matrix whose elements are the reciprocal of the corresponding diagonal elements of S; except when the elements of the latter are zero or very close to zero where the elements of S † are equated to those of S. When A is not a square matrix, then | {
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This algorithm takes log n steps in the worst case. Computer Science. Non-recursive algorithms I always knew that non-recursive algorithms are faster than recursive ones, so I was quite excited when, on an old CD I found a non-recursive algorithm. In C++ a function may be defined in terms of itself in the same way. From Wikibooks, open books for an open world < A-level Computing Recursion is a key area in computer science that relies on you being able to solve a problem by the cumulation of solving increasingly smaller instances of the same problem. The a1 is basically going to be "2" no matter what number you put in for n because it's always the first number in the list to sum for that particular F(n) formula. In the other cases, we follow the three-step recursive procedure we already described for disk 5. Recursive depth-first search (DFS) Depth-first search (DFS) is an algorithm that traverses a graph in search of one or more goal nodes. Dry Run of the Program. Do the above process | {
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particle-physics, parity
\tag{4}
$$
Why the different sign?
Apparently, the parity of the two-proton system is $p_{12}=+1$, whereas the particle exchange considerations lead me to $p_{12}=-1$.
I could not resolve this by considering the spin as well.
Could someone give me a pointer what I am doing wrong here?
Thank you! Action of the parity operator on a state is not determined only by intrinsic parities of the particles at hand, but also by the state itself. For example, if you have a one-particle state $\Psi_p$ with impulse $p$, then $P\Psi_p=\pm\Psi_{-p}$, and such a state does not even have a definite parity (it is not an eigenstate). | {
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ros, ros-melodic, rosdep, ros-kinetic, github
it's probably in the neighborhood of 5000 invocations daily from my employer's office
can you say anything about what you're actually doing that requires that many rosdep updates?
there are some that I can't eliminate --- notably the one issued by bloom-release when I bloom my projects. | {
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# Legendre Polynomial Orthogonality Integral | {
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c#, .net
new Customer(){Email = "mail5@mail.com", FullName = "Jack Jacksson",CreatedDateTime = DateTime.UtcNow.AddMonths(-2)},
new Customer(){Email = "mail6@mail.com", FullName = "Dope Jake",CreatedDateTime = DateTime.UtcNow.AddDays(-5)}
};
} | {
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qiskit, circuit-construction, pauli-gates, hadamard
$$
\begin{pmatrix} \cos(\frac{\pi}{4}) & -\sin(\frac{\pi}{4})\\
\sin(\frac{\pi}{4}) & \cos(\frac{\pi}{4})
\end{pmatrix}|0\rangle =\ \begin{pmatrix} 0.707 & -0.707\\
0.707 & 0.707\end{pmatrix} \begin{pmatrix} 1 \\ 0 \end{pmatrix} =\ \begin{pmatrix} 0.707 \\ 0.707 \end{pmatrix}
$$
Reason for this question is that I am trying different circuits to classify IRIS for comparison, and I am seeing much better accuracy when using my basic Y-Rotation based circuit in comparison to qiskits ZZFeature and RealAmplitudes circuit. While Hadamard gate is defined as
$$
H= \frac{1}{\sqrt{2}}
\begin{pmatrix}
1 & 1 \\
1 & -1
\end{pmatrix},
$$
$y$-rotation by $\pi/2$ leads to gate
$$
Ry(\pi/2)= \frac{1}{\sqrt{2}}
\begin{pmatrix}
1 & -1 \\
1 & 1
\end{pmatrix}.
$$
So, there is a difference in position of -1 in the second column. Application of the $X$ gate returns the -1 in $Ry(\pi/2)$ to right place to obtain Hadamard gate. | {
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homework-and-exercises, field-theory, calculus
Title: Vector Integrals: can I take out the vector outside of the integral? Question:
Solution:
The notation used is: $(x,y,z)$ is for rectangular coordinates, $(\rho,\varphi,z)$ for cylindrical coordinates and $(r,\theta,\varphi)$ for spherical coordinates. ${ { \hat { a } } }_{ ρ }$ represents the unit vector for $\rho$ (same applies to $x, y, z$ and other coordinates).
In part a, can't you take out ${ { \hat { a } } }_{ ρ }$ from the integral? I'm having trouble understanding how ${ { \hat { a } } }_{ ρ }$ depends on ϕ. ${ { \hat { a } } }_{ ρ }$ is defined as ρ=1, ϕ=0 and z=0. Aren't all of these constants that do not rely on ϕ? No you can't do that. The unit vector $\hat{a}_{\rho}$ does not mean: $\rho=1$, $\phi=0$, $z=0$. $\hat{a}_{\rho}$ actually depends on $\phi$ as it's $\left( cos\phi,sin\phi,0 \right)$. | {
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c++, object-oriented, embedded, device-driver
{{DigitalInputsDriverCfg::FaultPinActivationSrc::kFaultPinActivationCrc,
DigitalInputsDriverCfg::FaultPinActivationSrcUsage::kUsed},
{DigitalInputsDriverCfg::FaultPinActivationSrc::kFaultPinActivationPor,
DigitalInputsDriverCfg::FaultPinActivationSrcUsage::kUsed},
{DigitalInputsDriverCfg::FaultPinActivationSrc::kFaultPinActivationFault2,
DigitalInputsDriverCfg::FaultPinActivationSrcUsage::kUsed},
{DigitalInputsDriverCfg::FaultPinActivationSrc::kFaultPinActivationAlarmT2,
DigitalInputsDriverCfg::FaultPinActivationSrcUsage::kUsed},
{DigitalInputsDriverCfg::FaultPinActivationSrc::kFaultPinActivationAlarmT1,
DigitalInputsDriverCfg::FaultPinActivationSrcUsage::kUsed},
{DigitalInputsDriverCfg::FaultPinActivationSrc::kFaultPinActivation24VL,
DigitalInputsDriverCfg::FaultPinActivationSrcUsage::kUsed},
{DigitalInputsDriverCfg::FaultPinActivationSrc::kFaultPinActivation24VM, | {
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java, game, community-challenge, rock-paper-scissors
The array must be sorted (as by the sort(byte[]) method) prior to making this call. If it is not sorted, the results are undefined
Your code does not guarantee that the items are sorted. (It might work correctly anyway since your arrays only contains two items, but it still feels wrong) The values for Lizard are not sorted in the same way the others are.
You are using htotal and ctotal, hscore and cscore, Move computer and Move human. Assuming htotal stands for "Human Total", player classes would be useful here.
2 and 3 are very Magic numbers.
The variable names htotal and hscore is a bit confusing.
Your main method is quite long and does a lot of things. Some of these things could be extracted into other methods/objects. Your main method currently is responsible for:
Keeping score
Keeping score (of a single "best of three")
Randomize a computer move
Determine who wins a game | {
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renormalization, effective-field-theory
Is it obvious how this follows from the earlier flow equations?
Thanks! Ah, I think I've sorted it out. I share the key steps here.
For simplicity, let me write $t = \ln \Lambda$ so that $d/dt = \Lambda (d/d\Lambda)$. I further use the shorthand where $\dot\lambda = d\lambda/dt$.
For question 1, I believe an explanation is to annotate Polchinski's figure as follows: | {
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c++, object-oriented, game, console, pong
Map.h
#pragma once
#include <vector>
#include <iostream>
#include"EnumsAndStructs.h"
class Map {
private:
std::vector<std::vector<Objects>> m_map; //matrix which holds map
public:
Map();
void print();
std::vector<std::vector<Objects>>& getMap() { return m_map; }
};
Map.cpp
#include "map.h"
#include<Windows.h>
#include"consoleFunctions.h"
#include<sstream>
extern const int MAP_HEIGHT{ 25 };
extern const int MAP_WIDTH{ 100 }; | {
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in your worksheet to confirm that it represents a circle. Question from Shawna, a student: I am having problems finding the parameterization of a parabola. Typically, a physics problem gives you an angle and a magnitude to define a vector; you have to find the components yourself using a little trigonometry. On the other hand, the unit normal on the bottom of the disk must point in the negative \(z$$ direction in order to point away from the enclosed region. parametric graphing. (a) Find the cosine of the angle BAC at vertex A. Also you have titled this "parameterization of an ellipse" yet there is no ellipse in your post. We could also write this as. A while back I got curious about how certain text effects could be achieved, and one of the things I explored was warping text along a curve to achieve a kind of sweeping effect. The figure below shows a surface S and the vector field F at various points on the surface. Your answer should be independent of one of the two parameters -- | {
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c#, calculator, wpf
<Button Content="4" Margin="2" Grid.Column="0" Grid.Row="3"
FontSize="20" Click="NumberButton_Click"/>
<Button Content="5" Margin="2" Grid.Column="1" Grid.Row="3"
FontSize="20" Click="NumberButton_Click"/>
<Button Content="6" Margin="2" Grid.Column="2" Grid.Row="3"
FontSize="20" Click="NumberButton_Click"/>
<Button Content="-" Margin="2" Grid.Column="3" Grid.Row="3"
FontWeight="bold" Click="OperationButton_Click"/> | {
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For each $i=1,2,3,\cdots$ and each $j=1,2,3,\cdots$, consider the following collection:
$\mathcal{V}_{i,j}=\left\{W_{B,j} \times \overline{B}: B \in \mathcal{B}_i^* \right\}$
Each element of $\mathcal{V}_{i,j}$ is a closed set in $X \times Y$. Since $\mathcal{B}_i^*$ is a locally finite collection in $Y$, $\mathcal{V}_{i,j}$ is a locally finite collection in $X \times Y$. Define $V_{i,j}=\bigcup \mathcal{V}_{i,j}$. The set $V_{i,j}$ is a union of closed sets. In general, the union of closed sets needs not be closed. However, $V_{i,j}$ is still a closed set in $X \times Y$ since $\mathcal{V}_{i,j}$ is a locally finite collection of closed sets. This is because a locally finite collection of sets is closure preserving. Note the following:
$\overline{V_{i,j}}=\overline{\bigcup \mathcal{V}_{i,j}}=\overline{\bigcup \left\{W_{B,j} \times \overline{B}: B \in \mathcal{B}_i^* \right\}}=\bigcup \left\{\overline{W_{B,j} \times \overline{B}}: B \in \mathcal{B}_i^* \right\}$ | {
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"url": "https://dantopology.wordpress.com/category/metrizable-spaces/"
} |
Definition 2 Let $$f : \mathbb R^n \to \mathbb R$$ be a real-valued function. Then the $$\mathbf{i^{th}}$$ partial derivative at point $$\mathbf{a}$$ is the real number
\begin{align*}
\frac{\partial f}{\partial x_i}(\mathbf{a}) &= \lim\limits_{h \to 0} \frac{f(\mathbf{a}+h \mathbf{e_i})- f(\mathbf{a})}{h}\\
&= \lim\limits_{h \to 0} \frac{f(a_1,\dots,a_{i-1},a_i+h,a_{i+1},\dots,a_n) – f(a_1,\dots,a_{i-1},a_i,a_{i+1},\dots,a_n)}{h}
\end{align*} For two real variable functions, $$\frac{\partial f}{\partial x}(x,y)$$ and $$\frac{\partial f}{\partial y}(x,y)$$ will denote the partial derivatives.
Definition 3 Let $$f : \mathbb R^n \to \mathbb R$$ be a real-valued function. The directional derivative of $$f$$ along vector $$\mathbf{v}$$ at point $$\mathbf{a}$$ is the real $\nabla_{\mathbf{v}}f(\mathbf{a}) = \lim\limits_{h \to 0} \frac{f(\mathbf{a}+h \mathbf{v})- f(\mathbf{a})}{h}$ Continue reading Differentiability of multivariable real functions (part1) | {
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will see in later classes is of prime importance. Quadratic Applications -. An object is launched at 17. Agbaji, Eucharia O. The emphasis here is placed on results about quadratic forms that give rise to interconnections between number theory, algebra, algebraic geometry and topology. 10 MAT 080: Applications of Quadratic Equations Homework Problems Answers to Homework Problems are on page 19 a Applications involving rectangles 1. Problems to work out together in class. T1 - A martingale decomposition for quadratic forms of Markov chains (with applications) AU - Atchadé, Yves F. GHCI Grade 11 Functions and Applications: Home Quadratic Functions Quadratic Expressions Quadratic Representations Writing Vertex Form of a Parabola Given Vertex and Another Point (Part 1) ws1-12_quadratic_applications. Substitute the given information into the equation. T1 - A limit theorem for quadratic forms and its applications. Here's the questions I have on my modelling worksheet: APPLICATIONS OF | {
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beam
Title: Beam for shop gantry I have a small machine shop and need to size a beam for a gantry crane. The design is a 4 post fixed design with 2 horizontal beams running parallel across the shop ends with 1 beam to be mounted perpendicular on trolleys on top of the two parallels making a crane that can traverse x and y travel with an electric hoist rasing and lowering loads.
The span is approximately 28 feet and the biggest hoist I have is a mere 1 ton but would like to size it so that I have 3000-4000lbs load capacity. Also consider that the x and y axis trolleys are not motorized so a small dynamic/torsional load will be imparted in the x and y when the payload is pulled around.
I'm thinking a wide flange 12*45 would be a decent size. I'm unsure though if in beam calculators they account for the weight of the beam or if it is just the payload. With a centered load and 4000lbs the deflection shows .311" over 28 feet which seems reasonable enough if I understand what I'm looking at. | {
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gazebo
Originally posted by beartrap on Gazebo Answers with karma: 16 on 2016-10-24
Post score: 0
Original comments
Comment by chapulina on 2016-10-24:
How are you moving it? Make sure you're dragging the blue arrow. The more perpendicular your view angle is to the arrow, the more detailed movements you'll be able to make. You can also try making use the the align or snap tools.
Comment by beartrap on 2016-10-24:
I was not dragging the blue arrow, rather I was trying to move it as if it were a Power Point object. It is working for me now. Thanks for your help.
I needed to drag the arrows -- blue arrow for z movement. I was trying to drag the body of the object instead.
Originally posted by beartrap with karma: 16 on 2016-10-24
This answer was ACCEPTED on the original site
Post score: 0 | {
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beginner, sql, homework, sqlite
CREATE TABLE flight (
flight_id character(8) NOT NULL,
flight_days character(12),
from_airport character(3),
to_airport character(3),
departure_time numeric(4),
arrival_time numeric(4),
airline_flight character(20),
airline_code character(2),
flight_number numeric(4),
aircraft_code_sequence character(11),
meal_code character(4),
stops numeric(1),
connections numeric(1),
dual_carrier character(3),
time_elapsed numeric(4),
PRIMARY KEY (flight_id)
); If the question is only asking for fares, you select the first result row of the fares allowing one-way tickets where the from airport is in Boston and the to airport is in Baltimore, sorted ascending by one way cost.
Since this is tagged homework, I'll let you translate that to SQL. :-) | {
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EDIT: Actually, no, it's not much more difficult. Multiply the number with a big $a^{k!}$ number. For example, for the solution $11378$ above, multiply it by $2^{24}$. The expressions are now $(2^8)^3 + (9 \cdot 2^8)^3 + (22 \cdot 2^8)^3$ and $(2^6)^4 + (3 \cdot 2^6)^4 + (6 \cdot 2^6)^4 + (10 \cdot 2^6)^4$; the $1$s are no longer equal.
- 5 years, 3 months ago
Okay, I gotta tip my hat to your response to this one. Have you tried solving Pandya's posted problem related to this one? I think I'll try using your technique to solving this one.
- 5 years, 3 months ago
I agree, with the condition that all the numbers must be distinct positive integers, this problem becomes insane. That's the reason I filed that other question under Computer Science but this under number theory.
- 5 years, 3 months ago
Nope, I don't agree; I already stated how to fix through that condition above. | {
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ros, pose, ros-indigo
Title: How to publish a pose in quaternion?
I have all the values for point(x, y, z) and quaternion (w, qx, qy, qz). Do I just make a dict and publish it as a Pose topic?
Originally posted by paul_shuvo on ROS Answers with karma: 45 on 2019-02-27
Post score: 0
You need to create a publisher and publish a geometry_msgs/Pose message.
#!/usr/bin/env python
import rospy
from geometry_msgs.msg import Pose
def publisher():
pub = rospy.Publisher('pose', Pose, queue_size=1)
rospy.init_node('pose_publisher', anonymous=True)
rate = rospy.Rate(2) # Hz
while not rospy.is_shutdown():
p = Pose()
p.position.x = 0.5
p.position.y = -0.1
p.position.z = 1.0
# Make sure the quaternion is valid and normalized
p.orientation.x = 0.0
p.orientation.y = 0.0
p.orientation.z = 0.0
p.orientation.w = 1.0
pub.publish(p)
rate.sleep() | {
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pharmacology, structural-biology, medicinal-chemistry
Title: Do drugs' levo isomers have a better interaction with the receptors in our body than dextro isomers? Examples of levo drugs include levothyroxine, levocitrizine, and levodopa. Is there any specific reason why the receptors in our body exhibit this stereoisomerism and hold a high preference for the levo isomer form of any drugs? This is purely coincidental. The term levo simply means the direction that the pure enantiomer of the compound rotates plane polarized light at a specific wavelength and has no direct bearing on the interactions with biological systems. A quick search of the Dictionary of Drugs database gave 6845 compounds with optical rotation >0 (dextro-compounds) and 8406 compounds with optical rotation <0 (levo-compounds). So there are plenty of chiral drugs that rotate plane polarized light each direction. | {
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python, python-3.x, rest
return self._request(json={**kwargs, **{"command": "check"}})
def preorder(self, **kwargs):
required = ["order"]
if not any(arg in required for arg in kwargs):
raise InvalidParameters("Missing object of types: " + ", ".join(required))
return self._request(json={**kwargs, **{"command": "preorder"}})
def order(self, **kwargs):
required = ["order"]
if not any(arg in required for arg in kwargs):
raise InvalidParameters("Missing object of types: " + ", ".join(required))
return self._request(json={**kwargs, **{"command": "order"}})
def usage(self, **kwargs):
required = ["broadband", "sim", "voip"]
if not any(arg in required for arg in kwargs):
raise InvalidParameters("Missing object of types: " + ", ".join(allowed))
return self._request(json={**kwargs, **{"command": "usage"}})
def availability(self, **kwargs):
required = ["broadband"] | {
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virology, phylogenetics, blast, coronavirus
Title: Why would a 2019-nCoV protein sequence in the NCBI database match a protein submitted in 2018? There seems to be a bit of a conspiracy theory brewing over some data in the NCBI database, and I don't have the necessary knowledge to make sense of it.
It basically goes like this:
Go to NCBI BLAST
Click on the big Protein BLAST button
Enter AVP78033 in the main search box and click BLAST
Click on the first result that shows a 100% match and click "See 5 more title(s)" in the first entry | {
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genetics, entomology
VandenBrooks, John M., Elyse E. Munoz, Michael D. Weed, Colleen F. Ford, Michael A. Harrison, and Jon F. Harrison. “Impacts of Paleo-Oxygen Levels on the Size, Development, Reproduction, and Tracheal Systems of Blatella Germanica.” Evolutionary Biology 39, no. 1 (March 1, 2012): 83–93. https://doi.org/10.1007/s11692-011-9138-3. | {
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c#
var answer = peopleInOrder.First();
foreach (var person in peopleInOrder)
{
if (comparer.Compare(person.AgeDifference, answer.AgeDifference))
{
answer = person;
}
}
return answer;
}
private IEnumerable<IPersonBirthdayDifference> PopulateListInOrder()
{
IList<IPersonBirthdayDifference> peopleInOrder = new List<IPersonBirthdayDifference>();
for (var i = 0; i < this.people.Count - 1; i++)
{
for (var j = i + 1; j < this.people.Count; j++)
{
var isYounger = this.people[i].BirthDate < this.people[j].BirthDate;
var youngerPerson = isYounger ? this.people[i] : this.people[j];
var elderPerson = isYounger ? this.people[j] : this.people[i];
peopleInOrder.Add(PersonBirthdayDifference.Create(youngerPerson, elderPerson));
}
} | {
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fluid-dynamics, coordinate-systems, flow, calculus, differential-equations
\end{aligned}\end{equation}
and
\begin{equation}
\psi(r,\theta) = \sum_n \dfrac{d_n}{\gamma_n} r^{\gamma_n} \sin(\gamma_n(\pi-\theta)) \ .
\end{equation}
This expression is the superposition of infinite solutions that satisfy all the condition prescribed so far, but many of them are not-physical, as depicted in the picture below. | {
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the crank nicolson method for approximating solutions to the heat conduction diffusion equation week 5 14 3 matlab …. The tool used here is MATLAB, it is a programming language used by engineers and scientists for data analysis. Runge–Kutta methods for ordinary differential equations. You are constructing the Taylor polynomial around the point x with increment x-a, that is, you are computing an approximation for f (x+ (x-a))=f (2*x-a) Now as a=0, this means that as observed, you get f (2*x). The Delta Method gives a technique for doing this and is based on using a Taylor series approxi-mation. Etter does not discuss the approximate nature of the process and the possibility of plausible but incorrect contours. Writing a taylor series function for e^x. matlab taylor-series Updated Dec 3, 2021; MATLAB. Assuming the step h is small then Ο(h) may be ignored and Equation 3 represents an approximation to ƒ′(x) at x. m should be like, function yp = yprime(y,t) yp = y + t; Solve it by | {
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general-relativity, quantum-gravity
PS. I have seen this question and this one, which are obviously in the same direction I describe. They discuss the related question of whether GR can be derived from other principles, which is definitely a more consistent take on the unification problem. I suppose this means that part of my question is: why must Einstein's spacetime be replaced? Why can't the pseudo-Riemannian geometry picture be the fundamental one?
Edit: I have now also seen this question, which is extremely similar, but the main answer doesn't satisfy me in that it confirms the existence of the problem I'm talking about but doesn't explain why it exists. | {
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java, authentication, servlets
case "client3":
if(PASSWORD.equals(password)) {
request.getSession(true).setAttribute("username", username);
response.sendRedirect("app3/apk-3-index.html");
}
break; | {
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has exactly three.! Only three distinct eigenvalues graphs ( Harary 1994, pp regular … strongly regular graph not. Μ = 0 and k = 2 with parameters ( 4,2,0,2 ) n respectively is always equal to.. Of view, a strongly regular … strongly regular graphs is an eigenvector of both a and j eigenvalues! The simplest to explain on less than 100 vertices for which the existence non-existence... 5,2,0,1 ), the degree of every vertex of equals vertices have μ common neighbours tried to summarize the results! J is an important subject in investigations in graphs theory in last three.... The known results on strongly regular graph ' in English- > Croatian dictionary graphs ( 1994. 1994, pp therefore 3-regular graphs, we provide statistics about the size of the existence of graph. Un gráfico fuertemente regular con parámetros srg ( 13,6,2,3 ) called cubic graphs ( 1994. Discon- nected, and primitive otherwise 1994, pp defined as follows one is ( 99,14,1,2 ) it! We assume that´ in this paper we have | {
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} |
motors, electromagnetism
Title: Are stator magnets in brushed DC motors radially magnetised? In an electric motor like this one, are the stator magnets radially magnetised, as in, each of the two magnets has opposite poles on the inside and outside diameter? You should be able to find a picture on the web, but -- yes. One is north on the inside and south on the outside, the other is south on the inside and north on the outside (so pay attention if you have a pile of taken-apart motors that you're reassembling!). The steel can of the motor helps to convey the flux between the outside poles of the magnets, which increases the motor's torque -- this is why some of the larger "can" motors have an extra ring around the outer case right where the magnets are located. | {
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the-sun, magnetic-field, plasma-physics
$$\frac{\mathrm{d}P}{\mathrm{d}r}=\frac{B_z}{4\pi}\left(\frac{\mathrm{d}B_r}{\mathrm{d}z}-\frac{\mathrm{d}B_z}{\mathrm{d}r}\right)$$
where $r$ and $z$ are the radial and vertical coordinates (note the change of coordinate system - $r$ is along the surface, and $z$ is perpendicular to it!). The force from the magnetic field implies a lower gas pressure and a greater depression. | {
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c++, game, console, makefile
private:
void draw_spaces(unsigned num_spaces = 1) const;
unsigned num_slashes(unsigned disk_size) const;
unsigned num_chars(unsigned disk_size) const;
unsigned center_of(unsigned disk_size) const;
void draw_disk_row(unsigned disk_index, const Tower&) const;
void draw_rod_row(const Tower&) const;
void draw_rod_top(const Tower&) const;
void draw_tower_row(unsigned row, const Tower&) const;
unsigned pole_height_;
};
#endif
TowerDrawer.cpp
#include "TowerDrawer.h"
#include "Tower.h"
#include <cassert>
#include <iostream>
#include <climits>
TowerDrawer::TowerDrawer(unsigned pole_height): pole_height_(pole_height)
{}
unsigned TowerDrawer::pole_height() const { return pole_height_; }
size_t TowerDrawer::draw(const Tower& T) const
{
std::vector<Tower> tempTowerVector;
tempTowerVector.push_back(T);
return draw(tempTowerVector);
} | {
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ros, catkin, ros-comm, generate-messages
-- signals
-- filesystem
-- system
-- roscpp: 1 messages, 3 services
CMake Error at /home/rosuser/catkin_ws/build/ros_comm/clients/roscpp/cmake/roscpp-genmsg.cmake:53 (add_custom_target):
add_custom_target cannot create target "roscpp_generate_messages_cpp"
because another target with the same name already exists. The existing
target is a custom target created in source directory
"/home/rosuser/catkin_ws/src/rqt_common_plugins/rqt_image_view".
See documentation for policy CMP0002 for more details.
Call Stack (most recent call first):
/opt/ros/groovy/share/genmsg/cmake/genmsg-extras.cmake:280 (include)
ros_comm/clients/roscpp/CMakeLists.txt:35 (generate_messages) | {
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tensor-calculus, notation
Title: Anti-symmetrization brackets break Einstein summation convention How does one properly evaluate something of the form
$$
g_{a}^{\, [b} R_{c] b}~?
$$
when I try to expand using the definition of anti-symmetrization brackets the Einstein summation seems to break:
$$
g_{a}^{\, [b} R_{c] b} = \frac{1}{2} \bigg[ g_{a}^{\, b} R_{c b} - g_a^{\,c} R_{bb}\bigg]
$$
the second term should be summing over the $b$ index except now I have two lower indices which breaks convention. Is there some implied index raising that's built into the anti-symmetrization brackets? Because I don't see any reason why I should have introduced a metric factor into the second term. It also seems a little fishy since $b$ is a dummy index When contracting $b$ with $d$, you should have raised the index that was not being covariantly antisymmetrized. For example, instead of the term you showed, write it as $g_{a[b}{R_{c]}}^b$. | {
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quantum-field-theory, mathematical-physics, supersymmetry, topological-field-theory
Title: Supersymmetric generalisation of the bosonic $\sigma$ model in QM I am reading some lecture notes which demonstrate how various models in SUSY QM can be used to obtain topological invariants such as the Euler characteristic from the Witten Index.
The following lagrangian has been used directly, said to be the supersymmetric generalization of the bosonic $\sigma$ model. What is the motivation to consider this Lagrangian? How do I obtain the lagrangian? What is the sigma model being considered and how does it generalise?
Please provide a direct answer or references as deemed necessary.
(I googled to learn more, but most of the reviews start from lagrangians in TQFT which I have no knowledge about. I would like a more elementary explanation for the lagrangian. )
$\phi^i(t)$ are maps from $R$ or $S^1$ to a Riemannian manifold $M$ with metric $g_{ij}$.
$$L = | {
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organic-chemistry, nomenclature, amino-acids
P-14.3.4.1 Terminal locants are not cited in names for mono- and dicarboxylic acids derived from acyclic hydrocarbons and their corresponding acyl halides, amides, hydrazides, nitriles, aldehydes, amidines, amidrazones, hydrazidines, and amidoximes, when unsubstituted or substituted on carbon atoms.
Simple substituent groups that are named by means of prefixes (such as ‘amino’ and ‘formyl’) are arranged alphabetically. | {
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} |
human-biology, evolution
Title: How does Oedipus complex fit in the evolutionary theory? This is somthing that really makes me curious. How is posible that trough a evolution process the best posible candidate is the one that falls in love whith his progenitor? It doesn't. The Oedipus complex is one of Freud's theories to explain human behavior, not something that is endorsed by the fields of psychology or psychiatry. Freud had a lot of interesting theories, some of which remain core concepts in psychology, and some of which have been marginalized or rejected.
There are some professionals who feel it has merits for consideration, to one degree or another, but if you look at publications by the APA (American Psychological Association) and Psych.org (American Psychiatric Association), you won't see in their practice guidelines.
APA: http://psycnet.apa.org/journals/pst/32/4/535/
Wikipedia: http://en.wikipedia.org/wiki/Oedipus_complex#Criticism | {
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classical-mechanics, rotational-dynamics, friction, variational-calculus
This sounds like a rather elementary problem in classical mechanics but I haven't found a proof of this fact in any of the classical mechanics texts that I have read.
Note 1: I assume that the distribution of mass is uniform across the wheel so comparable wheels will have equal mass.
Note 2: Dry friction is assumed to be present. A complication arises as the shape gets further from circular symmetry. When it gains sufficient angular velocity, any non-circular object can 'jump' off the incline. See A jumping cylinder on an inclined plane. On leaving the plane the object becomes a projectile. Whether this speeds the descent or not might be difficult to determine. | {
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c#, linq, xml
static void Main(string[] args)
{
paramList = new List<Param>
{
new Param("paramA",1),
new Param("paramB",.5),
new Param("paramC",.01)
};
/* For testing, this XDocument is hard coded here. */
UpdateParams(XDocument.Parse("<root><paramA>121</paramA><paramB>100</paramB><paramC>197</paramC></root>"));
foreach(Param param in paramList)
{
Console.WriteLine("Name: {0} Value: {1}", param.xmlName, param.Value);
}
Console.Read();
}
}
Let's focus on UpdateParams. So I have an XDoc that has a root and values. Looks like this:
<root>
<paramA>121</paramA>
<paramB>100</paramB>
<paramC>105</paramC>
...
</root> | {
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classical-mechanics, poisson-brackets
\begin{equation}
\{R \hat{x},\vec{l}\cdot\hat{z}\}=R \hat{y}=\hat{z}\times(R\hat{x})
\end{equation}
which is consistent with your formula.
Incidentally, you might be worried that I started off by setting $\vec{c}=\vec{r}$. I think in the framework you are working in--particle mechanics--the vectors should all start from the same origin. If you want to start taking poisson brackets of vectors with different origins, I think you really need to generalize this discussion to field theory (which will complicate the story a bit because in addition to rotating the direction of the vector you need to rotate the origin, so you will end up with an additional term). So I think that may be what you have in mind but that is a more complicated story. | {
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clifford-algebra
So by using #1 and #4, we can immediately find that for vector $x$ and bivectors $A,\,B$,
$$
\langle A\cdot \left(x\wedge\left(x\cdot B\right)\right)\rangle=\langle Ax\left(x\cdot B\right)\rangle
$$
And then by #2 and #3, we can swap the order to give us,
$$
\langle Ax\left(x\cdot B\right)\rangle=\langle\left(B\cdot x\right)xA\rangle
$$
In order to swap the inner and geometric product, we use #3 again,
$$\langle\left(B\cdot x\right)xA\rangle=\langle\frac{1}{2}\left(Bx-xB\right)xA\rangle=\langle\frac{1}{2}\left(BxxA-xBxA\right)\rangle
$$
Then by swapping the orders of the products on the right term, we find,
$$\langle\frac{1}{2}\left(BxxA-xBxA\right)\rangle=\langle\frac{1}{2}\left(BxxA-BxAx\right)\rangle=\langle Bx\frac{1}{2}\left(xA-Ax\right)\rangle=\langle Bx\left(x\cdot A\right)\rangle.
$$
The final result is then obtained by removing the projection operator by inserting the inner and outer products that were removed in the first line. | {
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java, object-oriented, swing, game-of-life
* changed before other cells have been checked against the rules. Need board to change as one.
*/
newCells[i][j] = setCellStatus(cells[i][j],newCells[i][j],neighbours);
}
}
createNewBoard();
} | {
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memory-management, game-of-life, cellular-automata
So it is best to do this in main(). In your application you are doing this once for each game object. This may not seem like a big thing. But of your code get's re-used by another application that does not realize you are doing this. You mess up other people's code.
You should also note. This old random number generator is considered pretty bad. You should probably start looking at the new ones provided by C++11. They are much better and can be used in ways that don't interact (so you don't screw over other people's random numbers).
Move Platform specific code to its own function.
Sleep(500);
system("cls");
You should probably put this in its own function. So when people come to port your code to another platform they just need to provide an alternative implementation to a couple of specific functions and the rest of the code can stay the same. | {
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computability, physics, cellular-automata
My conjecture is that such isolated regions are impossible.
My intuition stems from the fact that Turing-complete reversible CA can be considered very simple models of physical reality (and proponents of the digital physics hypothesis argue that the physical world is actually a cellular automaton). If I understand correctly, totally isolated physical systems can't exist, thus I conjecture by analogy that this should also apply to all Turing-complete reversible CA.
(Turing-incomplete or irreversible CA can have isolated regions, but they are probably not good models of fundamental physical reality)
Has anybody already proved or disproved this assertion? Or do you have any thoughts about it?
UPDATE:
As Shor pointed out in the comments, the conjecture as stated above is false, since it is possible to use some states which are not required for Turing-completeness to achieve isolation. | {
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electromagnetism, momentum, classical-electrodynamics, textbook-erratum
$$
or
$$
\frac{d}{dt}\bigg(\sum_a m_a\mathbf v_a - \frac{1}{c}\mathbf d\times \mathbf B\bigg) = \nabla \bigg(\mathbf d\cdot \mathbf E + \boldsymbol \mu \cdot \mathbf B\bigg).
$$
The redefinition does not in any way follow from 4.22; it is a conscious decision of the physicist doing so; it is merely allowed by the fact that part of the EM force expression 4.22 is a total time derivative.
Of course, the purpose of this redefinition is not clear from that text. | {
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ros, ros-melodic, ardrone-autonomy
Title: How to make ardrone_autonomy work on ROS Melodic?
I need to control an AR Drone from a Jetson Nano which has Ubuntu 18 (ROS Melodic), and I can not compile the ardrone_autonomy package, because when I try, it gives me the next errors:
Base path: /home/jetson/ardrone_ws Source space: /home/jetson/ardrone_ws/src Build space: /home/jetson/ardrone_ws/build Devel space: /home/jetson/ardrone_ws/devel Install space: /home/jetson/ardrone_ws/install
####
#### Running command: "make cmake_check_build_system" in "/home/jetson/ardrone_ws/build"
####
####
#### Running command: "make -j4 -l4" in "/home/jetson/ardrone_ws/build"
#### [ 1%] Performing update step for 'ardronelib' [ 2%] Performing configure step for 'ardronelib' No configure [ 2%] Built target
_ardrone_a | {
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c#, rubberduck, localization
[XmlIgnore]
public string Name { get { return _name; } }
[XmlIgnore]
public bool Exists { get { return _exists; } }
public override bool Equals(object obj)
{
var other = (DisplayLanguageSetting) obj;
return Code.Equals(other.Code);
}
public override int GetHashCode()
{
return Code.GetHashCode();
}
}
}
So the "general settings" tab is only loading the instances where the Exists getter is returning true. I'm particularly not fond of what I did in the LoadLanguageList method... would there be a better way?
namespace Rubberduck.UI.Settings
{
public partial class GeneralSettingsControl : UserControl
{
private readonly IGeneralConfigService _configService;
private readonly DisplayLanguageSetting _currentLanguage; | {
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machine-learning, dimensionality-reduction, visualization
I'm just very largely confused why people make such a big deal about some of these visualizations. I take Natural Language Processing as an example because that's the field that I have more experience in so I encourage others to share their insights in other fields like in Computer Vision, Biostatistics, time series, etc. I'm sure in those fields there are similar examples.
I agree that sometimes model visualizations can be meaningless but I think the main purpose of visualizations of this kind are to help us check if the model actually relates to human intuition or some other (non-computational) model. Additionally, Exploratory Data Analysis can be performed on the data.
Let's assume we have a word embedding model built from Wikipedia's corpus using Gensim
model = gensim.models.Word2Vec(sentences, min_count=2) | {
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Moment of inertia of the equilateral triangle system - Duration: 3:38. The material is homogeneous with a mass density ρ. Today we will see here the method to determine the moment of inertia for the triangular section about a line passing through the center of gravity and parallel to the base of the triangular section with the help of this post. The moment of inertia of any triangle may be found by combining the moments of inertia of right triangles about a common axis. Because there is some frictional torque in the system, the angular acceleration of the system when the mass is descending isn’t the same as when it is ascending. Own work assumed (based on copyright claims). 6-1 Polar moment of inertia POINT C (CENTROID) FROM CASE 5: (I P) c 2 bh. What is the moment of inertia of this rigid body about an axis that is parallel to one side of the triangle and passes through the respective midpoints of the other two sides? a. Thank you User-12527562540311671895 for A2A The moment of | {
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"lm_q2_score": 0.8740772351648677,
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# Is this true? euclidean metric <= taxicab metric
1. Oct 8, 2009
### Mosis
given sequences $$\left\{x_n\right\}, \left\{y_n\right\}$$, is it true that
$$\sqrt{ \Sigma_{n=1}^{\infty} (x_n - y_n)^2} \leq \Sigma_{n=1}^{\infty} |x_n - y_n|$$
this isn't a homework problem. it's just something that came up - I think it's pretty clear that it's true, but I don't know how to show this.
edit: the sequences are square summable, of course.
Last edited: Oct 8, 2009
2. Oct 8, 2009
### D H
Staff Emeritus
Square both sides. The left hand side is obvious. Squaring the right hand side will yield the square of the left hand side plus another series, each of whose terms is non-negative.
3. Oct 8, 2009
### Mosis | {
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java, email, gui, javafx
private String mto, mhead, msub, cTYPE, cTEXT;
@FXML
protected void handleSendButton(ActionEvent e) throws IOException {
cTYPE = cmbTYPE.getValue();
mto = tto.getText();
mhead = thead.getText();
msub = tsub.getText();
cTEXT = ttext.getText();
Mail(mto, msub, cTEXT);
if(!mto.isEmpty() || !cTEXT.isEmpty() || !msub.isEmpty()){
transitionScene("Sent Email", "laysent.fxml", 500, 260);
}
}
public void Mail(String to, String sub, String cont) {
try { | {
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python, algorithm, combinatorics
This works, except the fact I am not sure it's the smartest way: when updating the Counter, I am relooping over the elements of l.
EDIT: I should probably clarify that the elements in the list are not necessary chars but Python objects. I have used single letters only for faster typing. Consider the following potential row in your data:
'abbbbbbbbbbbbbbb'
The bare minimum amount of work necessary would be to add 15 to both results - but with your loop as written, you'd add 15 to result['a']['b'], but then add 1 to result['b']['a'] 15 times. That's less than ideal.
So let's first condense the row into a counter - and then add the counter itself:
result = collections.defaultdict(lambda: collections.defaultdict(int))
for row in data:
counts = collections.Counter(row)
for key_from, key_to in itertools.permutations(counts, 2):
result[key_from][key_to] += counts[key_from] * counts[key_to] | {
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• I think your example may be precisely the kind of counter-example the OP was thinking of. If you go to the bank and ask to withdraw \$20, and the bank says it's not there, it's actually still possible that you have \$20 and they simply made a mistake. It can and does happen. So the contradiction is solved by learning there was a mistake, but it wasn't a mistake in your assumption of having \$20. Rather, it was a mistake in the bank's ability to count. If assuming A leads to contradiction, ¬A may not be the answer if the mistake was assuming B instead of ¬B. Which may mean A and ¬A contradict – MichaelS Feb 23 '16 at 9:00 • Nice illustration, but perhaps you should stress one aspect: this is a contradiction with already proven facts. You can well have propositions contradicting one another, but you can only reject one of them after you have proven the other. – MvG Feb 23 '16 at 19:41 • I was being general (actually I was being snarky and impatient; I have no idea why people like my | {
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special-relativity, kinematics
$$ v = c\,\tanh\frac{a\tau}{c} \tag{1} $$
$$ d = \frac{c^2}{a} \cosh\frac{a\tau}{c} \tag{2} $$
where $\tau$ is the time measured by the occupants of the rocket. NB due to time dilation this is not the same as time measured by the people watching the rocket decelerate. If you're interested the article also gives the equations for $v$ and $d$ in terms of the time for the external observers.
These equations assume you're starting at rest, but you just use them backwards. So if you're starting at some velocity $V$ just use equation (1) to work out the time needed to accelerate from rest to $V$ and this will be the same as the time needed to decelerate from $V$ to rest. Then put this time into equation (2) and it will give you the distance. | {
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thermodynamics, temperature, atmospheric-science, air, gas
Title: Why less temperature at high altitude? Why there is always cold at high altitudes. e.g. at peak of mountains. Also as we go high from sea level, temperature starts decreasing. Why is it? I'd like to add to the answers already given. Indeed, the atmosphere is transparent to shortwave radiation from the Sun, but absorbs a lot of the longwave radiation from the Earth; that's why we have the greenhouse effect, that's why the Earths has a liveable climate and that's part of the reason why we have the lapse rate we observe. But why is it colder at the Tibetan plateau, which is a large, flat area at roughly 4 km elevation? Aren't we equally close to the local surface there as when we are at sea level? | {
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"tags": "thermodynamics, temperature, atmospheric-science, air, gas",
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java, swing, collision
Title: Check for collision with side of screen I thought of a program where you move a square with the arrow keys. I created it and asked a question about it on Stack Overflow.
I copied the last code block of the accepted answer and tried to understand it. I think I do now. Now I wanted to add something that would check if the square would move off the screen. I added that myself as seen here:
Code inside Square class that replaces the move method of the copied code:
public void move(Direction dir) {
if(!(x + step * dir.getIncrX() > GamePanel.getWIDTH() - w) && !(x + step * dir.getIncrX() < 0))
x += step * dir.getIncrX();
if(!(y + step * dir.getIncrY() > GamePanel.getHEIGHT() - h) && !(y + step * dir.getIncrY() < 0))
y += step * dir.getIncrY();
} | {
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php, performance, zephir
$records++;
}
$stop = microtime(true);
$split_time = $stop - $start;
$start = microtime(true);
$a = unpack('L*',$Ldata);
$b = unpack('f*',$fdata);
$c = unpack('I*',$Idata);
$stop = microtime(true);
$unpack_time += ($stop - $start);
$measured_time = $fread_time + $split_time + $unpack_time;
echo "... fread time: $fread_time<br>\n";
echo "... split_time: $split_time<br>\n";
echo "... unpack time: $unpack_time<br>\n";
echo "... total measured time: $measured_time<br>\n";
echo "... records: $records<br>\n";
ob_flush();
flush();
}
This provides a much better time.
Running unpack on binary file (preload, split into 3 streams, unpack each stream)...
... fread time: 0.013000011444092
... split_time: 0.29400014877319
... unpack time: 0.54299998283386
... total measured time: 0.85000014305115
... records: 265533
Hopefully this is a bit more useful. | {
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"tags": "php, performance, zephir",
"url": null
} |
3), this solution is valid. a less than) is very different from solving an inequality with a > (i.e. The graph of an absolute value function will intersect the vertical axis when the input is zero. In this final section of the Solving chapter we will solve inequalities that involve absolute value. LEARN. ABSOLUTE Value = ABS(number) Where number is the numeric value for which we need to calculate the Absolute value. In other words, that equation was the one and only "nice" case of having two or more absolute values. Steph85: View Public Profile for Steph85: Find all posts by Steph85 # 2 06-29-2012 ctsgnb. Create a table of values for an absolute value function. So keep this other method in the back of your head, for in case you need it later. You can also use the absolute value symbol in the Desmos keyboard. The absolute value of a number is always positive. The function converts negative numbers to positive numbers while positive numbers remain unaffected. To get around this failure | {
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gazebo, gazebo-model
<geometry>
<mesh>
<uri>model://cube_20k/meshes/cube_20k.stl</uri>
<scale>0.5 0.5 0.5</scale>
</mesh>
</geometry>
</visual>
</link>
</model>
</sdf> | {
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} |
c#, multithreading, thread-safety, task-parallel-library
Both of the extension methods are completely unnecessary. If you just added using System.Linq;, both would work by themselves.
if (myThread == null)
myThread = StartThread(threadName);
This is not thread-safe. If two threads call this method at the same time, StartThread() will be called twice and two threads will be created.
Also, why is the thread started here and not in the constructor?
if (!myThread.IsAlive)
I don't think this is the right check here. Checking quit would be better, because that means enqueuing stops working as soon as the scheduler is disposed.
I don't like that your fields are in the middle of the class. If you put them at (or near) the top, they will be easier to find. | {
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c#, asp.net, generics, wcf
var user = service1Client.GetUserByUsername(User.Identity.Name);
var result = service2Client.HasDebts(user.Id);
service1Client.SafeClose();
service2Client.SafeClose();
return result;
}
There is a code repetition. Again.
How do people solve this problem? What is the best way to wrap a WCF proxy call and close it properly? You should let the Service1Client and Service2Client (and the remaining clients) implement the IDisposable interface and let the Dispose() method take care about the closing of the proxy.
This would lead the UserController looking like
public class UserController
{
public JsonResult HasDebts()
{
using (var _service1Client = new Service1Client())
using (var _service2Client = new Service2Client())
{
var user = _service1Client.GetUserByUsername(User.Identity.Name);
return Json(_service2Client.HasDebts(user.Id));
}
}
} | {
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} |
quantum-mechanics, wavefunction, pauli-exclusion-principle, identical-particles
Anyway, this is a long-winded way of saying that all multi-electron wavefunctions are always antisymmetrized, no matter how far away they are. (Although it turns out that you can't use this antisymmetrization to send information faster than light, so special relativity is safe.) But recall that in quantum mechanics, only inner products are physically observable, not the wavefunctions themselves. (Actually, only the norm-squared of an inner products is physically observable.) If the particles don't have any spatial overlap, then it turns out that if we want to evaluate $\langle \hat{X} \rangle$, we'll get the same answer whether or not we use the correct, antisymmetrized wavefunction, or a hypothetical unsymmetrized wavefunction. So even though the unsymmetrized wavefunction doesn't even lie in the Hilbert space and doesn't make any sense physically, we can get away with using it even though it's "wrong." Try it! Write down two non-overlapping wavefunctions and calculate $\langle | {
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machine-learning, modelling, social-networks, knowledge-representation
Title: How to represent the interests of a Facebook user I'm trying to figure out a way I could represent a Facebook user as a vector. I decided to go with stacking the different attributes/parameters of the user into one big vector (i.e. age is a vector of size 100, where 100 is the maximum age you can have, if you are lets say 50, the first 50 values of the vector would be 1 just like a thermometer). | {
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java, project-euler, java-8
Maybe I've gotten a bit over excited with the new options in Java 8, my main concern is readability, and for the rest just general advice. So a fair amount of Java8 is new to me, including the Stream API, which is, in essence, why this review is useful to me too. Bear with me...
Readability
You say "my main concern is readability". Now that I have spent some time looking in to what you are doing, what you are using, and reading up on some documentation, the answer is: yes!
The code does look strange, but that is only because the language structures are new. You are using them right, conforming to what few 'standards' there are... and it is fine.
General
RestrictedGenerator
public abstract class RestrictedGenerator<T> implements Iterator<T> { | {
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matlab, audio, audio-processing
Title: Use of "Audacity"for teaching undergraduate labs of digital signal processing for electrical engineering students? Can we use"audacity"for teaching undergraduate labs/practicals of digital signal processing? or only MATLAB/Octave should be used?
Weblink of "audacity"
https://www.audacityteam.org/ That depends on a lot on your learning goals for the lessons and the lab.
Audacity is primarily an audio editor designed for music recording and production. It has a lot of signal processing baked in, but it's only exposed to the user to the extent as it requires to make the music sound good. Signal Processing is just a means to an end here.
Matlab/Octave are scientific programming languages. They are specifically designed to develop and apply digital signal processing and they come with a lot of libraries that help do this. They are not great for large interlinked projects, since they are primarily designed to tackle fairly well defined scientific problems. | {
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python, beginner, role-playing-game, battle-simulation
def weaponReturn(weapon): # to test return variables // probably unnecessary?
print("Let's see if your " + weapon.lower() + " can defeat your adversary. Good luck!")
def battleSequence(enemy, player, weapon):
ambushChance = random.randint(0,1)
if ambushChance == 0:
print("The " + enemy["Name"] + " launched an attack on you from behind!")
print (player + " loses 10hp.")
else:
print("You get the first attack. You swing your " + weapon + "!")
#time.sleep(1)
print(player + " does 5 damage to the " + enemy["Name"] + "!")
playAgain = 'yes'
while playAgain == 'yes' or 'y':
enemyName, characterName = introduction()
time.sleep(1.5)
battleWeapon = weaponSelection()
weaponReturn(battleWeapon) | {
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• FACTS: And the proabiltiy of hitting a bomb at any non-neighbouring tile is... (depending on the setting). Might be lower still... – BmyGuest Apr 13 '17 at 12:39
• @BmyGuest I agree that the lowest probability of hitting the mine would probably be in a corner, but I wanted to elaborate on a more interesting case in which you want to continue with the region you already uncovered. – oleslaw Apr 13 '17 at 13:03
Facts and trivial observations/calculations:
Game area is 30x16 = 480 tiles and there are 99 mines. On average a bit above 1 bomb per 5 tiles.
You see 5 mines and have uncovered 25 tiles.
You know there are 9-12 mines in the total 38 tile area you see or adjacent.
This means you still have about 20% of hitting a mine if you randomly select a tile far away. Sounds pretty reasonable strategy, better than probability next to any mine - bottom 3 has 4 for 25%.
But ... | {
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"Driving from Dallas towards Memphis, JoJo averages 50mph. She figured that if she had averaged 60mph the driving time would have decreased by 3 hours. How far did she drive?"
I thought this would have been a simple D=R/T problem.. but somewhere I am not plugging the variables in correctly.. or setting the problem up the correct way. Please help.. this assignment is due in a few hours. Thanks!
1. Let d denote the covered distance and t the elapsed time. Then you know:
$\dfrac dt = 50$
and
$\dfrac{d}{t-3}=60$
2. Solve for d.
Spoiler:
You should come out with d = 900
3. I'm drawing a huge blank on how to make the two work together in one equation. The instructions note that I should set up and write a "rational equation", then solve AND answer the problem.
Unless I'm missing something.. I'm unsure of how I should incorporate the two to solve them. | {
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php, wordpress, twitter-bootstrap
$contentClass = 'site-content';
$containerClass = 'container-fluid';
if (!is_page_template( 'landingpage.php' )) {
if (is_single()) {
$contentClass .= ' pt-4';
}
else {
$containerClass = 'container';
}
}
?>
<div id="content" class="<?= $contentClass; ?>">
<div class="<?= $containerClass; ?>">
<div class="row"> | {
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window-functions
$$
Where $w$ is the window and $W$ is the window DFT
$$
\omega_{1/2} =\frac{\pi}{NT}
$$
Guess the value you are after is really $1-SL$
EDIT: I believe the left hand side of the equation is enough to answer @Shaggi's question, but to clarify a bit the notation of the rest, Harris defines DFTs as functions of $\omega_k$, so
\begin{align}
W(\omega_k) & = W\left(\frac{2\pi k}{NT}\right) = \\
& = \sum_n w(nT) e^{-j\omega_k nT}\\
& = \sum_n w(nT) e^{-j 2\pi kn/N}\\
W(\omega_{1/2}) & = \sum_n w(nT) e^{-j \pi n/N}\\
W(0) &= \sum_n w(nT)
\end{align} | {
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or the acute angle denoted by θ. tanθ=±(m 2-m 1) / (1+m 1 m 2) Angle Between Two Straight Lines Derivation. In this video learn how to find angle between two lines Subscribe to my channel by going to this link https://goo.gl/WD4xsf Use #kamaldheeriya … Therefore, the given lines are (2x – y) = 0 and (x-3y) = 0. Page Comments Email, Please Enter the valid mobile Two straight lines are parallel when the angle between them is zero and hence the tangent of this angle is zero. If θ is the angle between two intersecting lines defined by y1= m1x1+c1 and y2= m2x2+c2, then, the angle θ is given by. The given equation is 2x2 – 7xy + 3y2 = 0. If one of the line is parallel to y-axis then the angle between two straight lines is given by tan θ = ±1/m where ‘m’ is the slope of the other straight line. Now, the angle between pair of straight lines does not depend upon the value of the constant terms. (iii) bisector of the angle which contains (1, 2). Franchisee | If the two lines are a 1 x + b 1 y + | {
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genomics, scaffold
-- Looking for stddef.h - found
-- Looking for stdint.h
-- Looking for stdint.h - found
-- Looking for stdlib.h
-- Looking for stdlib.h - found
-- Looking for string.h
-- Looking for string.h - found
-- Looking for strings.h
-- Looking for strings.h - found
-- Looking for sys/types.h
-- Looking for sys/types.h - found
-- Performing Test HAVE_INLINE
-- Performing Test HAVE_INLINE - Success
-- Performing Test HAVE___INLINE
-- Performing Test HAVE___INLINE - Success
-- Performing Test HAVE___INLINE__
-- Performing Test HAVE___INLINE__ - Success
-- Performing Test HAVE___DECLSPEC_DLLEXPORT_
-- Performing Test HAVE___DECLSPEC_DLLEXPORT_ - Failed
-- Performing Test HAVE___DECLSPEC_DLLIMPORT_
-- Performing Test HAVE___DECLSPEC_DLLIMPORT_ - Failed
-- Check size of uint8_t
-- Check size of uint8_t - done
-- Check size of int32_t
-- Check size of int32_t - done
-- Looking for PRId32
-- Looking for PRId32 - found
-- Configuring done
-- Generating done | {
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conservation-laws, terminology
$$
g(\mathbf r,t)=g_0 \cos^2(\omega t)e^{-(\mathbf r-\mathbf r_1)^2/\sigma^2}
+
g_0 \sin^2(\omega t)e^{-(\mathbf r-\mathbf r_2)^2/\sigma^2}
$$
where $\mathbf r_1$ and $\mathbf r_2$ are in principle far apart. Here $G$ stays constant, but between $t=0$ and $\pi/2\omega$, all of the $G$ near $\mathbf r_1$ has disappeared without there being any flux through the plane between it and $\mathbf r_2$. Here $G$ obeys a global conservation law, but not a local one.
For clarity, I should note that your statement that "A local conservation law is the result of writing that the integrand of the global law are equal" is incorrect, and depending on exactly what you mean by it, there may be exceptionally few systems that obey that. | {
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python
Title: Mastermind game in Python I am a C#/.Net developer and have decided it is time to branch out and really learn Python. I started with a simple implementation of a Mastermind-esque game. Any comments about the code would be greatly appreciated. I already know the gameplay isn't perfect, but it was just a quick attempt. I also am aware that there isn't much user input checking, but again, quick attempt.
import random
class Game(object):
def run(self):
guesses = []
game_states = []
length = int(input("Choose length of code to break: "))
code = [random.randint(0, 9) for i in range(length)] | {
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particle-physics, mass, speed-of-light, neutrinos
$$ E_i t - |\vec p_i||\vec x| \approx \frac{m_i^2c^2|\vec x|}{2|\vec p_i|} \approx \frac{m_i^2c^3|\vec x|}{2 E_i} $$
The differences in masses cause differences in phases. As the different components of the neutrino gain different phases, they become a different mixture, a different flavor. That's why a neutrino that was produced as an electron neutrino after some time may be detected as a muon neutrino or a tau neutrino.
If you do wait long enough the neutrinos with different masses will get separated. At that point they no longer interfere with each other, and they won't oscillate - instead, a neutrino of a fixed mass has fixed chances of being detected as having one of the three flavors, and these chances do not change. | {
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ros, microcontroller, pr2, controller-manager
rosrun pr2_controller_manager pr2_controller_manager start MyControllerPlugin
The controller successfully loads in and starts in Terminal but nothing is happening in Gazebo. I did exactly as the tutorial said except I changed my_controller_name to MyControllerPlugin. Did I do something wrong?
The warning reflected after trying to run MyControllerPlugin is
[ WARN] [1349677273.168201399, 243.496000000]: The deprecated controller type MyControllerPlugin was not found. Using the namespaced version my_controller_pkg/MyControllerPlugin instead. Please update your configuration to use the namespaced version.
I'm running ubuntu 12.04 and Fuerte.
Thanks.
EDIT:
I managed to get rid of the warnings by
rosparam set my_controller_pkg/MyControllerPlugin/type my_controller_pkg/MyControllerPlugin
&
rosparam set my_controller_pkg/MyControllerPlugin/joint_type r_shoulder_pan_joint | {
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catalysis, proteins
Most molecular chaperones are ATPases (enzymes that catalyze ATP
hydrolysis), which bind to unfolded polypeptides and apply the free
energy of ATP hydrolysis to effect their release in a favourable
manner.
It is also made evident in the way some of them function (they possess some ATPase activity), it suggests they’re kind of catalysts enzymes:
They function in an ATP-driven process to reverse the denaturation and
aggregation of proteins (processes that are accelerated at elevated
temperatures), to facilitate the proper folding of newly synthesized
polypeptides as they emerge from the ribosome, to unfold proteins in
preparation for their transport through membranes.
Two classes of molecular chaperones have been well studied. Both are found in organisms ranging from bacteria to humans.
The heat shock proteins 70 (Hsp70) | {
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python, tkinter, sqlite
Instead, group widget creating and widget layout separately. The layout of one widget can affect the layout of others. Those sorts of problems are much easier to solve when all of the layout is together.
My rule of thumb is to group all widgets that share the same master together, though that rule can be broken when it makes the code more readable to do it slightly differently.
For example:
self.pathentry = ttk.Entry(master )
self.catentry = ttk.Entry(master )
self.tableentry = ttk.Entry(master )
self.pathentry.grid(row = 1 , column = 0 ,columnspan = 6, sticky = 'we')
self.catentry.grid(row = 2 , column = 1 , sticky = 'we')
self.tableentry.grid(row = 2 , column = 4 , sticky = 'we')
Don't use variables when calling grid on the same line
Code like this doesn't do what you think:
self.clearbutton = ttk.Button(...).grid(...) | {
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$C = \bigcap\limits_{i\in I} (A_i \cup T_i)$, where each $A_i$ is Euclidean-closed, and each $T_i \subseteq S$. Let $A = \bigcap\limits_{i\in I} A_i$; certainly $A$ is Euclidean-closed. Where must any point of $C \setminus A$ be?
Another approach is via local bases. For $n \in \omega$ and $x \in \mathbb{R}$ let $$B(x,n) = \begin{cases} \{y \in \mathbb{R}:\vert y-x\vert < 2^{-n}\},&\text{if }x \ne 0\\ \{y \in \mathbb{R}:\vert y-x\vert < 2^{-n}\}\setminus S,&\text{if }x = 0. \end{cases}$$
Show that $\mathscr{B} = \{B(x,n):n \in \omega \land x \in \mathbb{R}\}$ is a base for a topology, and that the topology that it generates is $\mathcal{T}$. (Thus, $\mathcal{T}$ differs from the Euclidean topology only at $0$.)
@Srivatsan: You’re right about the typo: I was originally going to define $B(x,n)$ in-line, separately for the two cases, and forgot to change the lead-in when I shifted to the case display. – Brian M. Scott Sep 19 '11 at 0:14 | {
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"openwebmath_score": 0.938724160194397,
"tags": null,
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catkin-make, cmake
Originally posted by SystolicDrake on ROS Answers with karma: 1 on 2017-07-02
Post score: 0
Original comments
Comment by SystolicDrake on 2017-07-02:
also i did try
sudo apt-get install python-catkin-pkg
Comment by gvdhoorn on 2017-07-02:\
Using PYTHON_EXECUTABLE: /usr/local/bin/python
this seems strange: did you install Python from sources or are you using some alternative Python interpreter? If so: catkin_pkg has probably not been installed for that, which would explain why you get the error.
Comment by SystolicDrake on 2017-07-02:
I installed Python from sources
Comment by gvdhoorn on 2017-07-03:
I've updated your question's title to better reflect your issue.
I installed Python from sources | {
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c++, template-meta-programming, sfinae
For example, my type may be designed to check for a stream inserter for pair<X, Y>, which the user could provide if they want custom behaviour, and if one doesn’t exist, do a default output format instead. Since your test framework adds a stream inserter for all pair<X, Y> (that don’t already have one), that means my type will never have to use its default output format. That means my type behaves differently depending on whether it’s being tested or not… which is absolutely not what you want. | {
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c++, beginner, calculator
Use range-based for loops
You can use the new range based for loops instead of the old style loops e.g.
for (const auto &s : students) { instead of for (int s = 0; s < students.size(); s++) {
Adjust the next line accordingly: cout << "Grades for " << s << endl;
Make constants constant
The assignments variable is never changed and should therefore be declared as a constant.
Use functions
You are already scoping the code which is good but as @RichN pointed out you might as well use functions instead.
Prefer using over typedefs
As Scott Meyers suggests in his book Effective Modern C++, you should prefer the new using directive over typedefs. For example:
using vec_size = vector<string>::size_type; | {
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ros, navigation, fixed-frame, robot-localization
<rosparam param="process_noise_covariance">[0.05, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0.05, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0.06, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0.03, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0.03, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0.06, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0.025, 0, 0, 0, 0, 0, 0, 0, 0, | {
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Exercise 3.III.2. 1. Decide if each vector lies in the range of the map from R 3 to R 2 represented with respect to the standard bases by the matrix. (a)(b) 2. Describe geometrically the action on R 2 of the map represented with respect to the standard bases E 2, E 2 by this matrix. Do the same for these:
Download ppt "3.III.1. Representing Linear Maps with Matrices 3.III.2. Any Matrix Represents a Linear Map 3.III. Computing Linear Maps."
Similar presentations | {
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"openwebmath_score": 0.9505565166473389,
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"url": "http://slideplayer.com/slide/4993308/"
} |
reaction-mechanism, atmospheric-chemistry, ozone
From this fact I expect four molecules of ozone from ethene, but in my own formulated reaction mechanism I get only three ozone molecules:
How many ozone molecules can be created by one ethene molecule and if my proposed mechanism is wrong what is the correct one? I think this question cannot be answered so easily - your proposed reaction mechanism, however, looks good. A detailed explanation and "main reaction mechanism" can be found here, page 192 (just search for "ethene" in the book). As you already indicate ethene reacts with a hydroxyl radical, followed by the addition of oxygen. The reaction with NO generates the HOCH$_2$CH$_2$O radical which can either dissociate or react with another oxygen molecule.
Further reactions of the oxidized products occuring during this pathway can also be found in the above reference, see page 372 (unfortunately only some parts of the book are available for free). | {
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mutations, cancer
References:
Two-hit hypothesis
Tumor Suppressor (TS) Genes and the Two-Hit Hypothesis
Cancer immunoediting: from immunosurveillance to tumor escape.
The Immunobiology of Cancer Immunosurveillance and Immunoediting | {
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compressible-flow
I also do not understand what happens after the flow reaches M = 1. The textbooks I've skimmed generally say "if there is still pipe length left or heat addition past the point of M = 1, then the inlet conditions must spontaneously change such that the flow reaches M = 1 at the end of the pipe." But they do not explain what these changes are or what mechanism enforces them. What if I am controlling the inlet conditions to be a certain pressure? Then what happens at the end of a rough walled pipe if the flow reaches M = 1 in the middle? Or what if I forcibly add more heat past the M=1 point (in an initially subsonic flow) where the inlet pressure is fixed? Physically, what will happen?
TL;DR: Entropy is maximized when a fluid flow velocity through a pipe reaches the speed of sound. So why aren't all our natural gas pipelines carrying gas at the speed of sound? Or why not even our water pipes? These are good questions to ask yourself. | {
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performance, beginner, php, object-oriented, array
if ($limit_counter <= 0) {
$limit_counter = self::NUMBER_OF_STOCKS_PER_REQUEST;
array_push($mother, $child);
$child = array();
}
}
return $mother;
}
public static function allEquitiesSignleJSON()
{
$equity_arrays = EquityRecords::getSymbols();
$base_url = self::BASE_URL . self::TARGET_QUERY;
$current_time = date("Y-m-d-H-i-s");
$all_equities = array();
// ticker: AAPL, GE, AMD
foreach ($equity_arrays as $ticker_arr) {
$ticker = array_column($ticker_arr, 0);
$equity_url = $base_url . implode("%2C", $ticker) . self::END_POINT;
$raw_eauity_json = file_get_contents($equity_url);
$raw_equity_array = json_decode($raw_eauity_json, true);
$all_equities = array_merge($all_equities, $raw_equity_array);
}
$all_equities_json = json_encode($all_equities); | {
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quantum-mechanics, photons, quantum-spin, quantum-electrodynamics, probability
Title: Does light with opposite spins cancel out the probability of an event? I'm an A level student and as i was reading QED by Richard Feynman, I came across something really interesting, that light can be reflected from all parts of the mirror according to the quantum theory. However, in normal conditions the probability amplitude of the event occurring at the edges of the mirror cancels out.
Could it possible that photons with opposite spin cancel out the probability of an event? Be careful with your use of the term 'spin' here: Feynman is talking about a sort of phase associated with a photon (the arrow which rotates in time). This is not analogous to the quantum concept of spin.
That said, it is true that two probability amplitudes with the same magnitude but opposite direction (phase) will cancel eachother out. Here's an example: | {
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