text stringlengths 1 1.11k | source dict |
|---|---|
### Step 3: Select Control Points
Use the Control Point Selection Tool to pick at least two pairs of control points.
```movingPoints = [151.52 164.79; 131.40 79.04]; fixedPoints = [135.26 200.15; 170.30 79.30];```
You can run the rest of the example with these pre-picked points, but try picking your own points to see how the results vary.
`cpselect(distorted,original,movingPoints,fixedPoints);`
Save control points by choosing the File menu, then the Save Points to Workspace option. Save the points, overwriting variables `movingPoints` and `fixedPoints`.
### Step 4: Estimate Transformation
Fit a nonreflective similarity transformation to your control points.
`tform = fitgeotrans(movingPoints,fixedPoints,'nonreflectivesimilarity');`
After you have done Steps 5 and 6, repeat Steps 4 through 6 but try using `'affine'` instead of `'NonreflectiveSimilarity'`. What happens? Are the results as good as they were with `'NonreflectiveSimilarity'`?
### Step 5: Solve for Scale and Angle | {
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"url": "https://www.mathworks.com/help/images/find-image-rotation-and-scale.html"
} |
quantum-mechanics, angular-momentum, computational-physics, notation, commutator
Title: What is this nested bracket notation? The following is an excerpt from K. Varga's paper, Precise solution of few-body problems with stochastic variational method on correlated Gaussian basis:
...The function $θ_{LM_L}(\mathbf{x})$ in Eq. (2), which represents the angular part of the wave function, is a generalization of $\mathcal{Y}$ and can be chosen as a vector-coupled product of solid spherical harmonics of the Jacobi coordinates $$ θ_{LM_L}(\mathbf{x}) = [[[\mathcal{Y}_{l_1}(\mathbf{x}_1) \mathcal{Y}_{l_2}(\mathbf{x}_2)]_{L_{12}} \mathcal{Y}_{l_3}(\mathbf{x}_3)]_{L_{123}}, \ldots]_{LM_L}.\tag{5} $$ Each relative motion has a definite angular momentum... | {
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# How can I get maximum number of vertices if I already know edges
If I already know edges how can I get the maximum number of vertices?
Question: There is a graph that has $$36$$ edges, and where every vertex has degree at least $$5$$. What is the maximum number of vertices this graph could have?
I think the sum of degrees is $$36\cdot 2$$ which is $$72$$. And the sum of degrees is bigger or equal than adding the least degree of every vertices together.
Therefore, $$72\geq 5n$$ and then $$14.4\geq n$$, so the maximum number of vertices is $$14$$. Is it correct? | {
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"openwebmath_score": 0.8808165788650513,
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"url": "https://math.stackexchange.com/questions/2960421/how-can-i-get-maximum-number-of-vertices-if-i-already-know-edges"
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ros
drone_macros.xacro
<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
<xacro:macro name="prop_link" params="name">
<link name="${name}">
<inertial>
<origin xyz="0 0 0.0089339" rpy="0 0 0" />
<mass value="0.06804" />
<inertia ixx="5.4455E-05" ixy="2.3822E-05" ixz="0" iyy="1.2182E-05" iyz="0" izz="6.5653E-05" />
</inertial>
<visual>
<origin xyz="0 0 0" rpy="0 0 0" />
<geometry>
<mesh filename="package://drone_description/meshes/propeller.STL" />
</geometry>
<material name="">
<color rgba="0.69804 0.69804 0.69804 1" />
</material>
</visual>
<collision>
<origin xyz="0 0 0" rpy="0 0 0" />
<geometry>
<mesh filename="package://drone_description/meshes/propeller.STL" />
</geometry>
</collision>
</link>
</xacro:macro> | {
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solar-system, nemesis
An alternative argument is that the Sun is captured in orbit by the stellar remnant at a later date. This avoids the supernova problems, but the capture process is inherently unlikely in our Galaxy once stars have left their birth environments, especially capture which is tuned rather precisely to yield just less than zero for the resultant system potential energy of a very wide binary. Capture by a "normal" star would in any case be much more likely than capture by a relatively rare compact object. | {
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"tags": "solar-system, nemesis",
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} |
php, validation, json
//the most common case is that a hex string sent to the php script
$packet->header = "HEX";
$packet->data = "48656c6c6f20576f726c64";
if ($packet->header == "HEX")
{
//do validation and process data
print ("HEX data recieved");
}
elseif ($packet->header == "JSON")
{
//do validation and process data
print ("JSON data recieved");
}
else
{
//data is not expected data or data is corrupt
}
?>
What does everyone think of this solution? | {
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newtonian-mechanics, friction
Setting up Newton's second law (for linear and rotational motion), we have$^*$
$$mg\sin\theta-f=ma$$
$$fR=I\alpha$$
Imposing the no slip condition $a=R\alpha$, we can determine that
$$f=\frac{mg\sin\theta}{1+mR^2/I}$$
So, the only way the magnitude of the static friction force $f$ can be equal to the component of weight down the incline $mg\sin\theta$, it must be that $mR^2/I=0$. This could be obtained when $I\to\infty$ so that we have an object that essentially cannot be rotated, and then in this case the object would in fact remain at rest, since we are imposing a no slip condition on an object that cannot rotate, and hence cannot translate either. | {
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"tags": "newtonian-mechanics, friction",
"url": null
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resonance, valence-bond-theory
As others have noted, electrons are still delocalized across the entire molecule in molecules for which we do not use resonance structures. The difference is that we can approximate the bond orders in those cases as integers, so only one structure is needed to represent that. | {
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The ratio test and root test are much easier then comparison test and integral test as it is not necessary to find another series or integral or anything else to compare with the given series. To gather information about these three series, let us first determine if they converge or diverge. ∞ n n2 + 2 n = 1 Evaluate the following integral. doesn't exist, we can use the divergence test to say that this series diverges. 1 day ago · Veteran Monster Energy Series crew chief Matt Borland has been suspended for a failed drug which he says was caused by a diet coffee he’s been drinking. org is down for planned maintenance work. Limit Comparison Test and Direct Comparison Test. Integral Test. Quizlet flashcards, activities and games help you improve your grades. 3 Quiz Left, Right, Midpoint, or Trapezoid Area Approximation, Indefinite Integrals(Including Trig), Particular Solutions, Basic Definite Integrals, Problems 73 from Section 4. This page was last edited on 29 October 2016, at 07:18. • | {
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"openwebmath_score": 0.8300469517707825,
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ros, catkin, find-package
Originally posted by William with karma: 17335 on 2013-12-05
This answer was ACCEPTED on the original site
Post score: 6 | {
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python, python-3.x
if __name__ == "__main__":
#deal with args
ap = argparse.ArgumentParser(formatter_class=argparse.RawTextHelpFormatter, epilog='''\n
This software has been made to automate taking screenshot and OCRing to text file.
It is using Tesseract OCR v5.0.0
Default is screenshot mode with 30s interval.
To run in files use -m 1 and -c (corners).
''')
ap.add_argument('-m', '--mode', choices=[0, 1], default=0, type=int, help="0 for screenshot, 1 for files. Default is screenshot mode.")
ap.add_argument('-p', '--path', help="files path, default is .\\images\\")
ap.add_argument('-c', '--corners', help="Img corners required with files mode eg. -c '0 0 1920 1080' ")
ap.add_argument('-t', '--time', type=int, help="Screenshot interval, default is 30s")
ap.add_argument('-o', '--output', help="output file, default is .\\text.txt")
ap.add_argument('-l', '--lang', help="language, for codes check tesseract docs, default is polish") | {
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np-complete, np-hard
We know that Circuit Sat is harder than all problems in NP. If 3SAT is harder than Circuit Sat, then 3SAT must also be "harder than" all problems in NP.
NP-complete is defined as NP membership and NP-hardness. You prove both, hence you've proved NP-completeness.
If you're still uncertain, go back to the definitions of NP and polynomial time reductions.
Check also the reference question What is the definition of P, NP, NP-complete and NP-hard? | {
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python, beginner, python-3.x, tkinter
# Function to find weight
# of operators.
def _weight(self, op):
if op == '+' or op == '-':
return 1
if op == '*' or op == '/':
return 2
return 0
# Function to perform arithmetic
# operations.
def _arith(self, a, b, op):
try:
if op == '+':
return a + b
elif op == '-':
return a - b
elif op == '*':
return a * b
elif op == '/':
return a / b
else:
return None
except ZeroDivisionError:
print("Invalid Operation: Div by Zero")
self.answer.set("ZeroDivisionError")
return "ZeroDiv" | {
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thermodynamics, work
That being said, $Vdp$ can have a different meaning than flow work in the case of a closed ideal gas system. Though not applicable to your balloon example (whose boundary is not rigid), it can refer to an isochoric (constant volume) heat addition or subtraction which results in an increase or decrease in the pressure and temperature of the gas.
The differential form of the ideal gas law applies regardless of the process, so it can be used for the derivation of any process involving an ideal gas. The potential physical significance of the $VdP$ term for a closed ideal gas system, where flow work and $PdV$ work is not involved, is for an isochoric process.
Hope this helps | {
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An arc is a part of the circumference of the circle. How Do You Find the Area of a Circle if You Know the Radius? It's also straightforward to find the area if you know the radius: a = π r 2. a = \pi r^2 a = πr2. (see Trigonometry Overview), where Given the area, A A, of a circle, its radius is the square root of the area divided by pi: r = √A π r = A π n is the number of sides Find A, C, r and d of a circle. The angle between the two radii is called as the angle of surface and is used to find the radius of the sector. To find the area of the quarter circle, … If you know the radius of a circle, you can use it to find the area of that circle. The missing value will be calculated. Therefore, the radius of the circle is 7cm. So, if we think about the entire circle, what is the area going to be? We know that the area of a circle is equal to pi times our radius squared. A sector is a portion of a circle, which is enclosed by two radii and an arc lying between the area, where the smaller | {
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"lm_q2_score": 0.8962513772903669,
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"openwebmath_score": 0.9071367979049683,
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"url": "https://www.eliterugservices.com/css/unchain-blockchain-geaajfz/archive.php?c53898=how-to-find-radius-from-area"
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computational-chemistry, molecular-dynamics
Title: Calculating the x, y and z distances between two molecules - AMBER (Molecular Dynamics) I am interested in calculating the x,y and z distance between two molecules over a given simulation time. I know how to calculate the total (r) distance between them, but I want the distance between them along all three dimensions.
For the total distance, cpptraj can be used as:
parm prmtop-file
trajin netcdf-file
distance DIST :1-4@heavy-atoms-from-molecule-1 :5-8@heavy-atoms-from-molecule-2 out dist.out
run
quit
But like I said before, I do not want the r-distance. Is there anyway to calculate the x,y and z-distances in cpptraj? If not, what other alternatives do I have? I ended up realizing that if you run:
parm prmtop-file
trajin netcdf-file
vector v0 :1-4@heavy-atoms-from-molecule-1 :5-8@heavy-atoms-from-molecule-2 out v0.out magnitude
run
quit | {
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"tags": "computational-chemistry, molecular-dynamics",
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javascript, html5
JavaScript will throw its own error if you try and append a non-DOM element to the DOM, so there's not much point in you doing that as well.
Let's talk jQuery
I'm glad you said you don't want to learn jQuery just now. I'm a bit bias (currently dealing with a lot of hoo-hah at work due to jQuery and its silliness in work at the moment) but I just want to say to you (and to anyone else reading this) that you might not need jQuery and jQuery is very dangerous when inter-operating between different DOM frameworks (for example - Angular and jQuery) due to the way it internally works by caching elements.
Browsers can make great optimisations on stuff like document.getElementByXXX such as caching the element so it is O(1) after first access. There's almost never a reason to use jQuery unless you're using a framework that requires it - such as Backbone - or laziness, these days. Or unless you're supporting dinosaur-age browsers. | {
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python, neural-network, keras, regression, lstm
Title: predict future value in every one hour using (t+60 minutes) LSTM neural network in python I have a data csv file including with three inputs and two output with time series. Here data took an every one hour one hour. So I need to predict my next future value at t+60 according to the previous input value and at that time period if having new input value using regression neural network. So I choose LSTM neural network to predict next future value. But I don't know how to give time period to predict my future value.
Can anyone suggest me how to solve this problem?
Can anyone give me any examples to clear out this problem?
Here that prediction value will come as input value (g).
subset of my csv file
here I upload my code;
def create_data(data, look_back=1):
dataX, dataY = [], []
for i in range(len(data) - look_back - 1):
a = data[i:(i + look_back), :]
dataX.append(a)
dataY.append(data[i + look_back, 2])
return numpy.array(dataX), numpy.array(dataY) | {
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acid-base, equilibrium
Is there a specific rule that an added acid/base will react only with the base/acid in the product side of the reaction?
No, and you can always combine two equilibrium reactions with overlapping species (like the hydronium ion in the first and second reaction) to arrive at a third that also has to be at equilibrium. | {
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molecular-biology, bioinformatics, cancer, gene-expression, copy-number-variation
Of course if M happens to be produced by a gene exhibiting copy number gain/loss then that could also play an important role in how much X RNA transcripts you ultimately detect (even in the event that X actually has a neutral copy number). Hope this helps. | {
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computational-physics, laser, software, noise
You have an extra $\sqrt{2}$ factor multiplying the Gaussian random number, which I think is not correct.
You can choose anything for the constant $a$, but it should be greater than the enquired values of $\tau$. If $\tau\approx 1$, then try $a>10$.
It is important to do the limit $t\to\infty$ limit in the simulations. To do so, wait for what is usually called a "thermalization time" $t>a$ before your first measure. | {
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"tags": "computational-physics, laser, software, noise",
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algorithm-analysis, asymptotics, ambiguity
Title: Big Oh vs Big Theta I mathematically understand $f(n) \in O(g(n))$ : $f(n)$ does not grow faster than $g(n)$. More formally, $\exists c, n_0$ s.t. $f(n) \leq cg(n) \forall n \geq n_0$.
Similarly, $f(n) \in \Theta(g(n))$ means that $f(n)$ grows approximately as fast as $g(n)$. i.e. $f(n) \in O(g(n)), \Omega(g(n))$.
What I don't get is why people use big Oh for the running time of an algorithm? Shouldn't we be using big Theta. When we say "Running time" of an algorithm, we refer to worst case running time i.e. $T(n) = max \{ ALG(x): |x| = n \}$.
So, ex: the worst case running time of linear search on an input of size $n$ ($n$ elements and a target value) is $\Theta(n)$ and $O(n)$, but $\Theta(n)$ gives more information. So, why do algorithm books use $O(n)$ and not $\Theta(n)$. I see two reasons why people prefer Big Oh over Big Theta: | {
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ros, linking
Title: problem linking pcl_io
Hi,
I'm building this on my Raspberry Pi - anyone any idea what might be wrong re: the extract error message:
Both libtheoradec.so.1, and libspeex.so.1, are on the system.
Thanks in advance
Mark
Linking CXX executable ../../bin/pcl_convert_pcd_ascii_binary
/usr/bin/ld: warning: libtheoradec.so.1, needed by /usr/lib/arm-linuxgnueabihf
/libavcodec.so.53, not found (try using -rpath or -rpath-link)
/usr/bin/ld: warning: libspeex.so.1, needed by /usr/lib/arm-linux-gnueabih /libavcodec.so.53, not found (try using -rpath or -rpath-link)
/usr/lib/arm-linux-gnueabihf/libavcodec.so.53: undefined reference to `speex_uwb_mode'
/usr/lib/arm-linux-gnueabihf/libavcodec.so.53: undefined reference to `speex_encoder_init'
/usr/lib/arm-linux-gnueabihf/libavcodec.so.53: undefined reference to `speex_encode_int' | {
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"openwebmath_score": null,
"tags": "ros, linking",
"url": null
} |
java, multithreading
Title: Correct control of execution of Java thread I'm writing an application that will use the JLayer library to play an mp3 file. Since the player does not have any methods to pause the playback - play() does not return until the song is finished - I decided to put it in a thread and simply control that thread. This is possible because one can execute play(1) which plays a single frame of the song. Putting this in a loop will thus play the entire song smoothly.
What I have done is the following:
Create a Thread class Mp3PlayerThread that can be used to play a song in a different thread.
Create a wrapping class Mp3Player that holds a thread object and controls the volatile flags inside the Thread. | {
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"tags": "java, multithreading",
"url": null
} |
# All generating sets of $S_3$?
I am trying to find all generating sets of $$S_3$$, is there a theorem which states how many sets I should have?
I know for example $$(12)$$ and $$(123)$$ is one such generating set however my question is 'how do I find all generating sets without having to compute them with brute force?' as of course, this will be lengthy.
• $S_3$ has $6$ elements so $64$ possible subsets. Why do you think that brute forcing this will take a noticable amount of time? – freakish Oct 7 '19 at 12:09
• Perhaps a better question you could ask is this: "How many minimal generating sets does $S_3$ have and how do I find them all?" This is because every generating set contains a minimal generating set and from any minimal generating set you can construct further generating sets by simply appending more elements. – the_fox Oct 7 '19 at 12:09 | {
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c++, c++11, multithreading
This falls into what is known as Rule of Three, which means that if a construtor does some non-trivial work, such as memory allocation, then more than likely you'll need to define custom copy constructor and assignment as well (or disable them).
Memory Management:
In the Semaphore class, condition_variable and mutex are declared as pointers. I would declare them by value to avoid extra memory allocations and improve data locality. I don't see any obvious reason for them to be pointers. If you do keep the pointers and dynamic allocations, then consider using a std::unique_ptr rather than manual new and delete calls, to ensure exception safety and simplify the resource management logic. Same applies to thread and mutex in Worker. Those could be declared by value as well. Otherwise, would be better as smart pointers too. | {
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integral is an online tool that displays the value! X they are improper according to the previous page is defined as a limit of integration 3.72 +2... X+2 } =$ sqrt ( x+1 ) as crazy as it may,... Free ` improper integral is convergent or divergent calculates the integral calculator is a online... The convergence or divergence indefinite integral can be written as the limit exists and is finite, then the calculator. Integral using the contact form or email me on mathhelp @ mathportal.org definite or integrals. Displaying the full working process of solving the problem and exercises interested in the. | {
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Suppose that $$A$$ is an $$n\times n$$ matrix such that $$Ax=b$$ is inconsistent some vector $$b$$. Show that $$Ax=b$$ has infinitely many solutions for some (other) vector $$b$$.
Solution
By hypothesis, $$A$$ does not satisfy condition 6 of the Theorem $$\PageIndex{1}$$. Therefore, it does not satisfy condition $$3\text{,}$$ so $$\text{Nul}(A)$$ is an infinite set. If we take $$b=0\text{,}$$ then the equation $$Ax=b$$ has infinitely many solutions.
3.6: The Invertible Matrix Theorem is shared under a GNU Free Documentation License 1.3 license and was authored, remixed, and/or curated by Dan Margalit & Joseph Rabinoff via source content that was edited to conform to the style and standards of the LibreTexts platform; a detailed edit history is available upon request. | {
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} |
So you've found two of four solutions for $x \in [0, 2\pi)$.
Now you need to only to determine when $\bf \cos x = 0$.
-
it is it when pi/2 and 3pi/2 – Fernando Martinez Feb 26 '13 at 17:31
Yes, indeed! So there are four solutions...to the given equation. The equation is true when either factor $\;\cos x\;\;$ or $\;\csc x - \sqrt 2\;\;$ is equal to $0$. – amWhy Feb 26 '13 at 17:33
yes I get I understand now. – Fernando Martinez Mar 2 '13 at 19:00
So, either $\cos x=0\iff x=(2m+1)\frac\pi2$ where $m$ is any integer.
$0\le (2m+1)\frac\pi2< 2\pi\implies 0\le 2m+1<4\implies m=0,1$
or, $\csc x=\sqrt2\implies \sin x=\frac1{\sqrt2}=\sin \frac\pi4$
So in that case, $x=n\pi+(-1)^n \frac\pi4$ where $n$ is any integer.
If $n$ is even $=2r$(say) $x=2r\pi+\frac\pi4\implies 0\le 2r\pi+\frac\pi4<2\pi\implies r=0$
If $n$ is odd $=2r+1$(say) $x=(2r+1)\pi-\frac\pi4\implies 0\le (2r+1)\pi-\frac\pi4<2\pi\implies r=0$
-
Use the fact that $AB = 0 \implies A = 0 \text{ or } B = 0$. | {
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compilers, functional-programming, haskell, imperative-programming
So here comes my question, on today's comptuters that execute imperative instructions, is this a limitation of the compiler or functional programming itself? For every imperative function with no side effects, either in a language without GC such as C/C++/Rust/assembly or one with GC such as Java, is there a pure functional counterpart in Haskell, Scala, etc. that can be compiled to run with identical performance in time and space (not just asymptotic but exactly the same) or even to the same instructions, with an optimal functional compiler that utilizes all modern and even undiscovered optimization techniques such as tail recursion, laziness, static analysis, formal verification, and so on which I don't know about? | {
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• The argument of the cosine function is in radians, not in degrees, so you have $\cos(2\pi k)=1$ for integer $k$ ($2\pi$ corresponds to $360$ degrees). The rest follows. Sep 16 '18 at 11:25
• The truth is, any base could be used for either the trig functions or exponents. The "natural" bases are Radians for the Trig functions and "e" for exponents. See dsprelated.com/showarticle/754.php for the best explanation ever why this is so. Well, I think it's the best. Mar 14 '19 at 19:31
## 3 Answers
I will reuse a former answer of mine too: Proof of complex conjugate symmetry property of DFT. It relates to how sines and cosines can be defined. One answer is: from the exponential, and thus derives $$\pi$$. There exist other constructions, this one is (imho) elegant. | {
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control-engineering, aerospace-engineering, mathematics
Title: 3D Transformation Between Two Cartesian Coordinate Systems Using Euler Angles I am trying to transform any arbitrary vector $\bf{v_{1}}$ in a Cartesian frame $\mathscr{F_{1}}$ into a different Cartesian frame $\mathscr{F_{2}}$. Both $\mathscr{F_{1}}$ and $\mathscr{F_{2}}$ have the same origin. I have consulted Aircraft Flight Dynamics and Control by Wayne Durham, and understand that book's solution as follows:
Use the standard yaw-pitch-roll $ z,y,x$ $/$ {$\theta_{z},\phantom{s} \theta_{y},\phantom{s} \theta_{x}$} (usually called {$\psi, \theta, \phi$} respectively) / $3 2 1$ order. There exist three transformation matrices, one for each axis. First, rotate about the z axis of $\mathscr{F_{1}}$. Call the transformation matrix $T_{\mathscr{F'},1}$ since it goes from $\mathscr{F_{1}}$ to an intermediate frame $\mathscr{F'}$. $T_{\mathscr{F'},1}$ is given as
$$T_{\mathscr{F'},1}=\begin{bmatrix}
cos(\theta_{z}) & sin(\theta_{z}) & 0 \\ | {
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c++, median
I've compiled with plenty of warnings, and run the tests under Valgrind to eliminate any silly dangling-iterator problems.
Some specific concerns:
Have I omitted any useful tests?
Do I really need four overloads of median::value? I accept that the two midval() implementations are different enough that they are necessary.
Is throwing std::domain_error an appropriate reaction to empty input?
Is passing compare by value the correct choice? The standard algorithms do so, and I guess one can use a std::reference_wrapper to override that (if we're gathering execution statistics, perhaps).
Have I missed any useful constraints on the template types?
Anything else worthy of note. | {
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Let $g(x)=x^3-b^3+(b-x)^3-3bx(b-x)$. Then $g$ is at most cubic and
$$g(b)=g(0)=g(2b)=g(-b)=0 \Rightarrow g(x)\equiv 0$$
The term $P=(a-b)^3 + (b-c)^3 + (c-a)^3$ is cyclically symmetric in $a,b,c$, and divisible by $a-b$ since setting $a=b$ makes it zero. It is therefore divisible by $Q=(a-b)(b-c)(c-a)$ (whose factors are pairwise relatively prime), and given that $\deg(P)=3=\deg(Q)$, the quotient must be a constant. Computing the coefficients of $a^2b$ in $P,Q$ (admittedly a computation) one sees that $P/Q=\frac{-3}{-1}=3$.
Let $a-b = x$ , $b -c= y$ and $c-a =z$ . So actually you want to know the value of $x^3+y^3+z^3-3xyz$ . Here the technique resides .
$x+y = (a-c) =-z$ ,
$x^3+y^3+z^3-3xyz = (x+y)^3-3xy(x+y) +z^3-3xyz = -z^3 +z^3 +3xyz -3xyz = 0$
Hence the value is $0$ | {
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lagrangian-formalism, variational-principle, stress-energy-momentum-tensor, classical-field-theory
How is this last expression obtained? The answer lies in your text "The action leads via a direct procedure (involving varying with respect to the metric itself) to a unique energy-momentum tensor.". You need to vary with respect to the metric tensor $\eta^{\mu\nu}$. You have to do ($\sqrt{\eta}= \sqrt{-\text{det}(\eta_{\mu\nu}}))$:
Construct the action: $S = \int d^4x \sqrt{\eta}L $
Perform the variation with respect to the metric tensor:
$$\cfrac{\delta S}{\delta \eta^{\mu\nu}}=0$$ | {
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r
luminosities <- c(luminosities, luminosity)
}
plot.table <- data.frame(phases, luminosities)
o <- order(phases)
with(plot.table, plot(x=phases[o], y=luminosities[o],
main=paste("Zone",zone_num,"Light Curve",sep=" "),
type="l", pch=3, lwd = 6, col="purple", xlab=expression("Phase"),
ylab=expression("Luminosity " (L/L['\u0298'])), cex.main=1.60,
cex.lab=1.80, cex.axis=1.60))
dev.off()
} | {
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ros, ros-control, ros-kinetic, ros-canopen, controller-manager
OK, so now, the node wont crash :D idk what did change, but im trying multiple times, even restarted the launch file, but it wont crash..
Comment by akosodry on 2018-06-22:
It just gives the error messages: either: Throw location unknown (consider using BOOST_THROW_EXCEPTION) or Controller 'joint_1_position_controller' is already running,
So basically i think the spawning was succesfull.
Comment by akosodry on 2018-06-22:
I have now both joint_state_controller and joint_1_position_controller in running state. In the parallel terminal i am getting continously the error message Throw location unknown. But if i publish to /joint_1_position_contller/command nothing happens
Comment by akosodry on 2018-06-22:
If i stop the controller and start again, i get the following error:
[ERROR] [1529679302.698301311]: joint_1 is not ready to switch mode
[ERROR] [1529679302.698396748]: Could not switch controllers. The hardware interface combination for the requested controllers is unfeasible. | {
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homework-and-exercises, geometry, satellites, gps
Title: Number of GPS satellites required to give 100% coverage I am a Belgian school student in sixth grade of secondary school (the Belgian equivalent of High school). Together with two class mates we were assigned to write some kind of essay about the Global Position System.
During the research about this subject we did not manage to find a (mathematically sufficient) reason why there are about 21 satellites required to provide a good coverage on earth.
We know that there are four satellites required to pinpoint one location, how could that information be used to calculate the minimum number of satellites required? Is there a general calculation for this magic 21 number?
Apologies if we overlooked the answer for this problem. Most of the following info can be found in the GPS Standard Positioning Service Performance Standard
First, I fear I'll have to correct your number, because you need 24 satellites for 100% coverage. | {
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algorithm-analysis, runtime-analysis, matrices, numerical-algorithms, fourier-transform
$$\rm Q = \frac{1}{\sqrt m} \, F_m$$
where $\rm F_m$ is the $m \times m$ Fourier matrix. Hence,
$$\rm H^{\top} H + I_m = Q \Lambda Q^* + I_m = Q \Lambda Q^* + Q Q^* = Q \, (\Lambda + I_m) \, Q^*$$
and
$$\rm \left( H^{\top} H + I_m \right)^{-1} U = Q \, (\Lambda + I_m)^{-1} \, Q^* U = \frac 1m \, F_m \, (\Lambda + I_m)^{-1} \, F_m^* U$$
The Fast Fourier Transform (FFT) algorithm can now be used to factor the Fourier matrix $\rm F_m$ and its Hermitian transpose. What is the cost? | {
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organic-chemistry, reaction-mechanism, elimination
Title: Elimination reaction mechanism decision (order = 1 or 2)
Match the following:
\begin{array}{}
& \textbf{Column I}&&\textbf{Column II} \\
\text{(A)} & \ce{CH3-CHBr-CD3} \text{ on treatment with alc. KOH gives}& \text{(P)}& \text{E1 reaction}\\
&\ce{CH2=CH-CD3} \text{ as a major product} \\
\text{(B)} & \ce{Ph-CHBr-CH3} \text{ reacts faster than } \ce{Ph-CHBr-CD3} & \text{(Q)} & \text{E2 reaction}\\
\text{(C)} & \ce{Ph-CH2-CH2Br} \text{ on treatment with } \ce{C2H5OD/C2H5O-}& \text{(R)}& \text{E1cb}\\
&\text{gives } \ce{Ph-CD=CH2} \text{ as the major product.} && \text{reaction}\\
\text{(D)} & \ce{Ph-CH2-CH2Br} \text{ and } \ce{Ph-CD2-CH2Br} \text{ react with the }& \text{(S)} & \text{First Order}\\
&\text{same rate.} && \text{reaction}
\end{array}
The answer given in the exam solutions is
A − Q; B − Q; C − R,S; D − P,S | {
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machine-learning, statistics, activation-function, softmax
The function $e^x$ is its derivative.
It has a particularly simple power series expansion:
$$ e^x = 1 + x + \frac12 x^2 + \frac16 x^3 + \cdots + \frac1{n!}x^n + \cdots $$
All of the coefficients are rational numbers. If the base had been something intuitively "nicer" than $e$, such as an integer, the coefficients would need to be irrational.
For this reason, most mathematicians will pick $e^x$ when they need an exponential function and have no particular reason to choose one base over another. (Except for computer scientists and information theorists, who sometimes prefer $2^x$). | {
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ros, arduino, c++, ros-lib, rosserial
Title: Publisher or Subscriber inside a class [rosserial]
Hi, I'm using rosserial in Arduino and have a problem initializing the Publisher or Subscriber inside the class constructor:
void setup() {
DifferentialDriveRobot *my_robot = new DifferentialDriveRobot( );
}
void loop() {
...
}
And the class is implemented as (in this example, with a subscriber):
class DifferentialDriveRobot
{
...
public:
ros::NodeHandle nh;
ros::Subscriber<geometry_msgs::Twist> sub;
...
void ddr_callback(const geometry_msgs::Twist& msg) {...}
DifferentialDriveRobot() { // Constructor
nh.initNode()
sub("/cmd_vel_mux/input/teleop", ddr_callback);
nh.subscribe(sub);
}
}; | {
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game time, the number of rotations, and the number of operations 3. interface minor adjustments ===== 1.0.0.1 update ===== 1, Add Cube state save / read function. This works for all numbers. = 216. 10 x 10 = 100. Only type the value of the length of the side. Homemade Thousand Cube Printout. Eight is a perfect cube because its cube root, 2, is a whole number. For a number to be both a square and a cube, it would have to be a sixth power. This tool is used to generate the list of first n (up to 1000) cube numbers. Cube numbers. Perfect Cubes: 0: 0: 1: 1: 2: 8: 3: 27: 4: 64: 5: 125: 6: 216: 7: 343: 8: 512: 9: 729: 10: 1000: 11: 1331: 12: 1728: 13: 2197: 14: 2744: 15: 3375: It is easy to work out the cube root of a perfect cube, but it is really hard to work out other cube roots. Just right click on the above image, then choose copy link address, then past it in your HTML. Cube is an integer.the result of the number multiplied by itself twice. See below the definition and examples of | {
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26 for ilen = uniqlens(:)'
27 idxlen = find(len==ilen);
28 chunks(idxlen) = arrayfun(@(xx,yy)xx:yy,...
29 start(idxlen),stop(idxlen),'UniformOutput',false);
30 end
31 % reassemble chunks into output
32 x = [chunks{:}]; | {
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"url": "https://blogs.mathworks.com/loren/2008/10/13/vectorizing-the-notion-of-colon/?s_tid=blogs_rc_2"
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homework-and-exercises, classical-mechanics, hamiltonian-formalism
\left(1 - \frac{r_1}{r}\right)
\left(\frac{r_2}{r} - 1\right)
}
dr \\
&= 2 \, \pi \left( \frac{r_1 + r_2}{2} - \sqrt{r_1 \, r_2} \right).
\tag{4}
\end{align}
The factor “2” comes about
because $\oint$ means integration over a round trip, whereas $\int_{r_1}^{r_2}$ is only a half of it. The bounds of $\oint$ are $r_1$ and $r_2$ because the round trip ends at $r_1$ and $r_2$, and the integrand becomes zero there (exceeding it would cause complex numbers, which doesn't make sense).
We can now do the integral
\begin{align}
2 \pi J
&=
\oint p_\theta \, dr
\tag{5}
\\
&=\sqrt{2 m E}
\oint \sqrt{
\left(1 - \frac{r_1}{r}\right)
\left(\frac{r_2}{r} - 1\right) } dr
\\
&=
\sqrt{2 m |E|} 2 \, \pi
\left( \frac{r_1 + r_2}{2}-\sqrt{r_1 \, r_2} \right)
\\
&=
\sqrt{2 m |E|} 2 \, \pi
\left( \frac{mGM(t)}{2|E|} - \frac{p_\theta}{\sqrt{2m|E|}} \right) \\
&=
2 \, \pi
\left( \frac{m^2GM(t)}{\sqrt{2 m |E|}} - p_\theta \right)
\end{align}
where we have used Eqs. (2) and (3) on the fourth line. | {
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quantum-mechanics, angular-momentum, quantum-spin, hamiltonian
Title: Why does Hamiltonian no longer commutes with $\mathbf L$ and $\mathbf S$ in presence of spin orbit coupling? Is this something due to change in Hamiltonian due to relativistic correction.
i.e. $H$ being $$(\frac{e^2}{4\pi {\epsilon _0}}) \mathbf{S \cdot L}$$ instead of $$(\frac{e^2}{8\pi {\epsilon _0}}) \mathbf{S \cdot L}$$ like in Thomas Precession.
Ref :-Page 278 DJ Griffiths Introduction To Quantum Mechanics.
Why don't they commute? | {
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java, matrix, reinventing-the-wheel, graphics
@Test
public void testRotate() throws Exception {
SceneObject object = new SceneObject(0,0,0);
final Vertex CENTER = new Vertex(0,0,0);
Vertex vertex0 = new Vertex(-10, 0, 0);
Vertex vertex1 = new Vertex(10, 0, 0);
object.add(vertex0);
object.add(vertex1);
object.rotate(CENTER, 1, 0, 0 );//rotate 1 degree on x
System.out.println(vertex0);
System.out.println(vertex1);
assertXYZ(vertex0, -10, 0, 0);//0
assertXYZ(vertex1, 10, 0, 0);//0
} | {
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programming-languages
Title: Is Programming/Coding necessary to pursue a masters degree in robotics? I am soon going to finish my undergrad in mechatronics engineering and wish to take up robotics for my masters. But I absolutely dislike any form of coding/programming. I am however,interested in the mathematics and physics behind the working of a robot. I'd also love to study about the control systems in a robot. So is coding a requirement if I want to take up robotics?
PS: I couldn't find the right tag for the question. Sorry! Please direct me to the right one if required. Is coding a requirement if you want to take up robotics? No, but it is strongly recommended. | {
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electrochemistry, ions
Direction of ion flow
In the reaction in question, copper cations travel from anode to cathode in the solution to balance the charge transport due to electrons traveling from anode to cathode via the wire. We can write the equation showing this explicitly by combining the half-reactions and keeping anode and cathode species labeled.
$$\ce{Cu(ano) + Cu^2+(cat) + 2e-(cat) -> Cu^2+(ano) + 2e-(ano) + Cu(cat)}$$
Because we can't have electrons or copper ions accumulate in or at the electrodes, we need a transport mechanism for both species (through the wire and through the solution, respectively).
Here are two more examples with different ion transport.
Water electrolysis
$$\ce{4H+(aq) + 4e- -> 2H2(g)}$$
$$\ce{2H2O -> O2 + 4H+(aq) + 4e-}$$ | {
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ros, 3rd-party-package, catkin, velodyne
Title: How do I remove a duplicate package?
I installed the velodyne driver package using
sudo apt-get install ros-indigo-velodyne
But then I realised that the release version didn't support what I needed.
The current master branch however does.
https://github.com/ros-drivers/velodyne
I cloned the repository to my catkin workspace, made it then installed it.
However, when I try to launch it with
roslaunch velodyne_pointcloud VLP16_points.launch
I get the error
[VLP16_points.launch] is neither a launch file in package [velodyne_pointcloud] nor is [velodyne_pointcloud] a launch file name
I think it's referencing the old package.
How do I remove the old package that I installed using sudo apt-get install?
Edit: Ran source command and outputted ROS_PACKAGE_PATH variable
$ source ~/catkin_ws/devel/setup.bash
$ echo $ROS_PACKAGE_PATH
/home/nathan/catkin_ws/src:/opt/ros/indigo/share:/opt/ros/indigo/stacks | {
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c++, queue, deque
Title: Implementation of std::deque In the prior obsolete implementation of std::deque, I used two std::vectors to contain the elements. But the standard guarantees that pointers and references to elements aren't invalidated when an element at either end is erased or when an element is inserted into either end, which the prior implementation doesn't:
To guarantee that, this new implementation contains every element to its own node: | {
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space, propulsion
Title: How far from a spacecraft would it's exhaust cool to BR temperatures? Just a thought that came to mind ...
The rockets on interplanetary scouts fire to impart motive/braking force to the craft. This force, I understand, is simply a reaction engine - the exhaust departs out the nozzle, and drives the engine & attached craft in the desired direction. In an atmosphere this exhaust would eventually disperse. In space one would expect the exhaust to continue in the direction it exited the nozzle. But space is cold.
Assuming the rockets fired in space far enough for any gravity knot to have negligible effect, how far from the nozzle would the exhaust cool to near CBR temperature? | {
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java, html, csv
<table border><tr><td>Name</td><td>Vorname</td><td>Alter</td></tr>
<tr><td>Ulbrecht</td><td>Klaus Dieter</td><td>12</td></tr>
<tr><td>Meier</td><td>Bertha</td><td>102</td></tr></table> CSVReader
Reading a CSV file can be a complex task. While many CSV files are just comma-separated-values, if a value contains a comma, it would be surrounded by double quotes, and if the value contains double quotes, the double quotes themselves are doubled.
To handle these more that just a basic CSV files, you really should use a CSV library, such as OpenCSV (com.opencsv:opencsv:5.0) or Apache Commons CSV (org.apache.commons:commons-csv:1.7).
HTML
Valid HTML
Your code essentially just writes <table>...table data...</table>. This isn't proper HTML. You're missing <html>...</html> tags around the entire document, and <body>...</body> around the content. You should probably also have a <head>...</head>, perhaps with a nice <title>...</title>.
Escaping | {
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nomenclature, molecules
$$\ce{Li}_2 \color{red}{1} ^1\Sigma_g^+: (1s\sigma_g)^2(1s \sigma_u)^2(2s \sigma_g)^2$$
now I can explain the origin of every term except the $1$ which I have put in red. What does this 1 mean? The conventional labelling of molecular states starts at X for the lowest state and A, B, C for higher ones and a, b, c, for equivalent states of the same symmetry but different multiplicity; see Herzberg spectroscopy books for many examples. These labels, however, reflect the order in which the states were discovered and so do not reflect their relative energies. It is becoming more common to precede a molecular state's symmetry label by an integer e.g. $1~^1\Sigma _g^+,~ 2~^1\Sigma _g^+,~3~^1\Sigma _g^+$ to reflect the energy ordering of states with the same symmetry. This notation reflects the way atomic levels of the same symmetry are labelled as $1$s, $2$s, $3$s, etc.
As an example, the conventional notation for the first four electronic states of $\ce{C2}$ in order of energy is | {
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newtonian-mechanics, forces, free-body-diagram, string, singularities
In real life, there is always going to be some sag in the system and $\theta >0$. It is a physical impossibility to have infinite tension and this is to be avoided both practically, and mathematically.
You statement that $1 \over 0$ is fine mathematically isn't accurate either.
For the second part, you need an estimate of the vertical stiffness of the wire given a small pertubation from the equilibrium position. The original equation isn't valid because it pertains to static equilibrium only.
The get the full dynamic model of the system you will need some assumptions. For example the wire will need to be elastic and the pertubation small enough to use small angle approximations. Even so, the resulting equation is non-linear and has 2DOF as the mass can sway left and right as well as up and down due to the elasticity of the wire. This considers the tension waves going back and forth along the wire. | {
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Order doesn't matter here, since the pens are identical. Combinations in a String of Digits. Permutations, combinations, and variations 1 Permutations Permutations are arrangements of objects (with or without repetition), order does matter. Python program to get all unique combinations of two Lists. Le marketing de contenu. The committee has a chair, a vice chair, a secretary, and a fourth member without special privileges or duties. Asking for help, clarification, or … A combination is a way of choosing elements from a set in which order does not matter. traduction nestable with dans le dictionnaire Anglais - Francais de Reverso, voir aussi 'nestle',nest',negotiable',notable', conjugaison, expressions idiomatiques How many combinations are there for selecting four? How many of those are there? Each r-combination of a set with n elements when repetition is allowed can be represented by a list of n 1 bars and r crosses. acb. Combinations with identical elements: 2) You have 2 blue | {
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python, web-scraping
for job in listings:
jobT = job.find('a', class_='jobtitle')
jobL = job.find('span', class_='location').text.strip()
jobS = job.find('div', class_='summary').text.strip()
link = jobT['href']
if any(any(subs in s for s in (jobT.text.strip().lower(), jobS.lower())) for subs in (jobName.split('+')[0], jobName[1])):
print('Your job in '+jobL+' as a '+ jobT.text.strip()+
'.\nHere is a quick summary of your job here: '+
jobS+'\nLink for more information and application for the job - https://indeed.com'+link, end='\n\n\n') What you are doing sounds reasonable overall.
It's good that you are using F-strings:
nmoPag = input(f"There are {noPag} number of pages. If you want to scrape all of them write 'Max' else write number of pages you wish to scrape: ") | {
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beam, concrete
Here's an example, without the ring of beams: It depends on the order of operations for the construction of the structure.
Let's start assuming the structure is as simple as the image you've given us: a single story with a slab supported by columns. | {
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technique tries! Traditional name, kernel density estimation smaller the bias and the larger the variance introduction to density... About the population are made, based on a finite data sample to... Good comparative study, 1994 the y axis, i.e can try the lpoly command in stata which... J. Hwang, S. Lay, and A. Lippman technique featured in this..: uni: Triangle: kernel density estimation 2 J. Hwang, Lay... Now, composite density values are calculated for whole data set Analysis of Histogram density estimates now! As far as accuracy and continuity a number of possible kernel functions listed... Random sample you 're unsure what kernel density estimates, or KDE closely! This article is dedicated to this technique and tries to convey the to! ) f ( x ) which is symmetric around the y axis, i.e found at the heatmap created! Heatmap was created kernel density estimation kernel density estimation can be found at kernel density in! Bandwidth on kernel density estimation for Statistics and | {
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filters
Title: Playing samples in a loop, without clicks or pops I'm trying to build an audio player that has this specific feature: when you scroll to x sample time, [x to x + 4096] samples are played in a loop until you move the mouse to another place.
The samples are taken from the backing audio. The problem is, I fail to play them back as a continuous note: the looping is not seamless.
So far I tried to start and end the loop at zero crossings. This slightly improved it, but I can still hear the seamless looping.
One idea I had was to go to the frequency domain, remove all, but the max magnitude bin and do an inverse FFT afterwards. This, sort of works, the looping is better, not perfect, but better, however, removing all the other freq components from the loop leaves it really "dry", not resembling the original (missing the harmonics) | {
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by using the dsolve function finds values for the constants that satisfy these conditions 1: solve following. Differential equations narrow '' screen width ( in physics and mathematics the.... A device with a Chegg tutor is free following differential equation requires one step—simple. Substitution—After you ’ ve found the general solution was specified does not involve complex numbers solving system of differential equations with initial conditions we usually use solving., 2020 from: https: //ocw.mit.edu/courses/mathematics/18-03sc-differential-equations-fall-2011/unit-iii-fourier-series-and-laplace-transform/unit-step-and-unit-impulse-response/MIT18_03SCF11_s25_1text.pdf Muller, u you ’ ve found the general solution, it s... Our Cookie Policy these later if we differentiate both sides of these we get solve! Solutions to your Questions from an expert in the matrix form and this the! It makes sense that the number of prey present by using the standard ansatz method following 4 order... | {
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telescope
Title: Infrared Region Telescopes Why do we need to build telescopes that can view in the infrared? What exactly do we need to see in the infrared region? I know this seems like a really broad question but I'm just curious about it. Three main reasons.
Lots of things in the universe are cool, much cooler than the Sun. Therefore they emit most of their radiation in the infrared spectrum. Examples might include brown dwarfs, giant exoplanets, circumstellar discs.
Lots of things in the universe are distant and highly redshifted. Thus even if they emit their radiation at visible wavelengths, we receive it at infrared wavelengths.
Lots of things in the universe are hidden by dust, which effectively absorbs visible light. Dust is much more transparent to infrared radiation, so we can see beyond it. An example would be the centre of our Galaxy. | {
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ros2
Originally posted by eric1221bday on ROS Answers with karma: 245 on 2019-09-19
Post score: 2
Original comments
Comment by tfoote on 2019-09-19:
Please edit your question to include links to what you're reading and where you're referencing.
Hi eric1221bday,
The design document you're referring to is actually a format, and the implementation is not limited to just those tags.
We started by writing the "parsing functions" of the tags that were available in roslaunch XML, but new ones can be easily added.
Here is Node's parsing function as an example.
The following actions will need a parsing function to get the functionality you're asking for:
https://github.com/ros2/launch_ros/blob/d25e2b334897b9c4526b1dcd1c8025debc245737/launch_ros/launch_ros/actions/composable_node_container.py#L31
https://github.com/ros2/launch_ros/blob/d25e2b334897b9c4526b1dcd1c8025debc245737/launch_ros/launch_ros/actions/load_composable_nodes.py#L35 | {
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performance, algorithm, c, strings
Minor things:
We don't need to include a newline at the end of the message we give to perror(). That function will append : and error description, then a newline of its own.
temp isn't a great name for a variable. It only tells us that it's short-lived, but doesn't indicate what it's for.
There are many redundant casts - I don't think any of the casts here are necessary (Any Type* converts automatically to Type const* - a cast just costs the reader's time, and makes it harder to spot the true problems).
The if (ptr) test leaves us holding state in our heads for half a screenful - it's easier to read if we test if (!ptr), which has a much shorter block (and also exits the function).
sizeof (char) is always 1 (because sizeof works in units of char), so those expressions can be simplified. | {
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c#, wpf, rubberduck, xaml
Height="35">
<Canvas Width="120"
Height="120"
Background="Transparent">
<Path Fill="Black" | {
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cosmology, dark-matter
Title: Why hasn't warm dark matter replaced cold dark matter as the standard model of cosmology? The $\Lambda\rm CDM$ (cold dark matter with cosmological constant) is the current standard model of cosmology because the model comes with a long list of phenomena successfully explained by it. However, there are a remaining handful of problems which are not yet resolved in the context of $\Lambda\rm CDM$, for instance (with links to my picks for reasonably accessible and/or up to date technical papers):
The too big to fail problem
The cusp-core problem
The missing satellites problem
The disk of satellites problem | {
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organic-chemistry, aqueous-solution, solubility
I think the reason behind this abnormal behaviour is the strong attractions already existing between p-nitrophenol molecules is a lot more stronger than interactions between water molecules and interactions with water molecules are weaker, I am not sure of my answer and would like a better explanation / ideas to think about solubility. What do you guys think should be the reason for this abnormality. I asked my teacher and also this is what i suspected , para nitro phenol is less soluble in water than phenol as para nitro phenol is way more polar than water and so the hydrogen bonding and other interactions formed by interaction between para nitro phenol and water are weaker than formed by interaction between molecules of para nitro phenol because of huge polarity para nitro phenol as compared to water but as dipole moments of water and phenol are almost same so they bond better than being alone and hence making phenol more soluble . | {
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python, rosbag
Title: Inserting into a Rosbag
Is there any way to add to a message to a rosbag at the beginning? I know you can append to a rosbag, but I want the message at the beginning.
Inserting all the other messages in afterward screws up the timing.
Originally posted by David Lu on ROS Answers with karma: 10932 on 2012-05-04
Post score: 1
I think rosbag Cookbook can do what you want. http://www.ros.org/wiki/rosbag/Cookbook
By section 1.2 of that link you do the following
import rosbag
with rosbag.Bag('input.bag', 'a') as bag:
from std_msgs.msg import String
metadata = String(data='my metadata')
for _, _, t in bag.read_messages():
break
bag.write('/metadata', metadata, t - roslib.rostime.Duration(0, 1))
Of course this does require post processing the data which may not be desirable.
Originally posted by Dustin with karma: 328 on 2012-05-05
This answer was ACCEPTED on the original site
Post score: 1 | {
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"openwebmath_score": null,
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} |
beginner, promise, typescript, angular-2+
}
}).catch((err) => {
return new Upload(Status.FAIL, err, new Date())
})
}
} First of all, there are some stylish issues in the code:
let input = new FormData();
// `input` is never reassigned so you should use `const` instead of `let`:
const input = new FormData(); | {
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"tags": "beginner, promise, typescript, angular-2+",
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} |
navigation, base-global-planner, costmap-2d, base-controller, move-base
local_costmap_params.yaml
local_costmap:
#Set the global and robot frames for the costmap
global_frame: odom_combined
robot_base_frame: base_link
#Set the update and publish frequency of the costmap
update_frequency: 5.0
publish_frequency: 2.0
#We'll configure this costmap to be a rolling window... meaning it is always
#centered at the robot
static_map: false
rolling_window: true
width: 3.0
height: 3.0
resolution: 0.025
origin_x: 0.0
origin_y: 0.0
plugins:
- {name: obstacle_layer, type: "costmap_2d::ObstacleLayer"}
- {name: inflation_layer, type: "costmap_2d::InflationLayer"}
#Configuration for the sensors that the costmap will use to update a map
obstacle_layer:
observation_sources: laser_scan_sensor
laser_scan_sensor: {data_type: LaserScan, sensor_frame: /laser, topic: /scan, expected_update_rate: 0.4, | {
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} |
javascript, beginner, programming-challenge
Iterate over each word, pushing to an array on the object, creating it first if necessary. Then, the object properties can be arranged lexiographically by sorting its entries (Object.entries returns an array of entries, where an entry is an array containing the key and the value, so just compare the keys in the .sort). This makes things so much shorter and cleaner:
function getOrderedNumbers(numbersByChar) {
return Object.entries(numbersByChar)
.sort((a, b) => (a[0] > b[0]) - 0.5) // Order entries alphabetically
.map(entry => entry[1]) // Take only the value of each entry
.flat(); // Turn the array of arrays of numbers into a single array of numbers
}
function parseString(inputStr) {
const numbersByChar = {};
for (const word of inputStr.split(' ')) {
const { char, num } = separateWord(word);
if (!numbersByChar[char]) {
numbersByChar[char] = [];
}
numbersByChar[char].push(num);
}
const numbersArr = getOrderedNumbers(numbersByChar); | {
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keras, tensorflow
model.fit(X_train, y_train, epochs=10, validation_data=(X_test, y_test))
and as you can see in the image below, for each epoch you can see that the first recall value (with threshold 0.6) is higher than the second one (threshold 0.9) as expected:
And for your case, to build the list of metrics objects programatically, where you can now see 3 recalls per epoch:
thresholds = [0.6, 0.7, 0.9]
metrics_objs_list=[metrics.Recall(thresholds=thr) for thr in thresholds] | {
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} |
graph-theory, co.combinatorics, metrics, max-cut, epsilon-nets
I initially asked this question here on mathoverflow. Here is an easy estimate. Here we call a set S⊆X an ε-net of a metric space X when for every point x∈X, there exists a point s∈S such that the distance between x and s is at most ε. If you want a strict inequality in the definition of ε-net, you can tweak the value of ε slightly.
It holds that ||A||∞ ≤ ||A||C ≤ n2||A||∞, where ||A||∞ denotes the entrywise max-norm of an n×n matrix A.
It is easy to construct an ε-net of the metric space ([0,1]N, d∞) with size ⌈1/(2ε)⌉N, and it is not hard to show that this size is the minimum. (To show the minimality, consider the ⌈1/(2ε)⌉N points whose coordinates are multiples of 1/⌈1/(2ε)−1⌉ and show that the distance between any two of these points is greater than 2ε.) By setting N=n2 and combining this with the aforementioned comparison between the cut norm and the max-norm, the minimum cardinality of an ε-net with respect to the cut norm is at least ⌈1/(2ε)⌉n2 and at most ⌈n2/(2ε)⌉n2. | {
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ros, roslaunch, network-setup, network
Title: Unable to Contact my Own Server
I am trying to run a roslaunch but I am unable to. Here is the error message:
Unable to contact my own server at [http://host-ubuntu:37730/].
This usually means that the network is not configured properly.
A common cause is that the machine cannot ping itself. Please check
for errors by running:
ping host-ubuntu
For more tips, please see
http://www.ros.org/wiki/ROS/NetworkSetup
The traceback for the exception was written to the log file | {
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"url": null
} |
# Math Help - Help!! Complex Fractions
1. ## Help!! Complex Fractions
can anybody help me?! I am really confused
1.) a-(5a/a+5) / a+(5a/a-5)
2.) (a/a-b) - (b/a+b) / (b/a-b) + (a/a+b)
3.) (a-b/a+b) + (b/a) / (a/b) - (a-b/a+b)
Thanks
2. Originally Posted by whoa
can anybody help me?! I am really confused
1.) a-(5a/a+5) / a+(5a/a-5)
2.) (a/a-b) - (b/a+b) / (b/a-b) + (a/a+b)
3.) (a-b/a+b) + (b/a) / (a/b) - (a-b/a+b)
Thanks
1) $\frac{{a - \frac{{5a}}{{a + 5}}}}{{a + \frac{{5a}}{{a - 5}}}} = \frac{{\frac{{a(a + 5) - 5a}}{{a + 5}}}}{{\frac{{a(a - 5) + 5a}}{{a - 5}}}} = \frac{{\frac{{a^2 + 5a - 5a}}{{a + 5}}}}{{\frac{{a^2 - 5a + 5a}}{{a - 5}}}} = \frac{{\frac{{a^2 }}{{a + 5}}}}{{\frac{{a^2 }}{{a - 5}}}} = \frac{{a^2 (a - 5)}}{{a^2 (a + 5)}} = \frac{{a - 5}}{{a + 5}}$ | {
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"url": "http://mathhelpforum.com/algebra/7515-help-complex-fractions.html"
} |
homework-and-exercises, electrostatics, charge, coulombs-law, dielectric
$$F = Eq_2 = \frac{1}{4\pi \varepsilon_0 k} \frac{q_1}{ r^2} q_2$$
with $E$ the electric field, $\varepsilon_0$ the vacuum permittivity, $k$ the dielectric constant of the material and $r$ the distance between the two charges. The dielectric constant $k$ takes into account the influence of the material onto the electric field (and thus also onto the Coulomb force).
So, if the charge was placed inside a material with dielectric constant $k$, the electric field would have been reduced by a factor $k$ and thus also the Coulomb force would have been reduced by a factor $k$. If the charge is placed into a vacuum, there is no influence on the electric field and thus also no influence on the Coulomb force (this corresponds to $k=1$). This second case is the case of your question and thus $F_1=F_2$. | {
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reference-frames, plasma-physics, shock-waves
The above image is an example of something called shock drift acceleration (SDA), where shock-reflected particles gain energy while skipping along the upstream edge of the shock front from the convective electric field. This is not to be confused with diffusive shock acceleration (DSA) (or first order Fermi acceleration) whereby particles gain energy by reflecting off of merging magnetic mirrors. A nice animation of SDA can be found at https://svs.gsfc.nasa.gov/4513.
(3) Am I wrong to be bothered by the concept of magnetic fields "moving" in the manner I described above, or am I missing something?
As I have already stated, I was missing several things. Further, magnetic fields do not "move" (i.e., field lines do not move), sources move or change and the fields respond. | {
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python, performance, cython
@classmethod
def clean_sheet_points(cls, goals_against: int) -> Points:
if goals_against == 0:
return cls.clean_sheet_bonus
return 0
class Forward(FrontLine):
goal_bonus = 4
@classmethod
def clean_sheet_points(cls, goals_against: int) -> Points:
return 0
class Team:
def __init__(
self,
club: Club,
players: Iterable[Player],
vice_captain: Player,
captain: Player,
) -> None:
self.club, self.vice_captain, self.captain = club, vice_captain, captain
self.players = {p.p_id: p for p in players} | {
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"tags": "python, performance, cython",
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inorganic-chemistry, coordination-compounds, crystal-structure
Title: How to calculate crystal field stabilisation energy? How to calculate it? I know that it depends on the coordination compound and the number of electrons present in t2g and eg orbitals and the final answer is expressed in terms of crystal field splitting parameter. But, how to know how many electrons are there in t2g and eg orbitals?
I think rather than a broad answer and example would help. So, consider the compound $\ce{[Ni(CO)4]}$ and how to calculate CFSE for it?
Step 1: Look up Nickel Carbonyl and find out what geometry it has.
We need the geometry to know how the $d$ orbitals will split in the ligand field. The geometry can also be predicted: late transition metals with strong field ligands tend to be tetrahedral.
Step 2: Find the appropriate crystal field splitting diagram for this geometry.
Step 3: Figure out how many $d$ electrons there are. | {
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Now $$A$$ is nonnegative, it is "well-known" that we can find orthogonal matrix $$Q$$ so that $$A=Q^T\Lambda Q$$, where $$\Lambda$$ is diagonal with $$\geq 0$$ entries. Write $$\sqrt \Lambda$$ be the diagonal matrix with $$(\sqrt\Lambda)^2=\Lambda$$, thus $$A=Q^T\sqrt\Lambda\sqrt\Lambda Q=(Q^T\sqrt\Lambda Q)(Q^T\sqrt\Lambda Q)$$. in conclusion, we can write $$A=P^TP$$, with $$P=Q^T\sqrt\Lambda Q$$.
Let $$P=[v_1, ...,v_n]$$. Then from $$A=P^TP$$ we see $$a_{11}=|v_1|^2$$, ... , $$a_{nn}=|v_n|^2$$. Thus $$\text{det}A= (\text{det} P)^2\leq (|v_1|\cdot...\cdot|v_n|)^2=|v_1|^2\cdot...\cdot|v_n|^2=a_{11}\cdot ...\cdot a_{nn}.$$
• Thanks, your proof is amazing. The first fact is also known as Hadamard's inequality. If you assign $P = \sqrt{\Lambda}Q$, then the expression $A = P^TP$ still holds true, and it's simpler. – Ly Minh Hoang Apr 22 at 4:56 | {
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} |
java, performance, game, computational-geometry, graphics
lights.add(new Light(newColor, new Vec2D(x, y), center.getRadius()));
}
}
}
/**
* @param g
* the graphics to use for rendering
* @param entities
* the list of entities to take into account when drawing shadows
* @throws Exception
*/
public void draw(final Graphics2D g, final List<Polygon> entities) {
// old Paint object for resetting it later
final Paint oldPaint = g.getPaint();
// amount to extrude our shadow polygon by
for (final Light light : lights) {
// minimum distance (squared) which will save us some checks
final float minDistSq = light.getRadius() * light.getRadius();
// The area for drawing the light in
Area shadowArea = null;
for (int i = 0; i < entities.size(); i++) {
final Polygon e = entities.get(i);
final Rectangle2D bounds = e.getBounds2D(); | {
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c++, integer, vb6
extern "C" LPWIN32_FIND_DATAW ZFILEIO_API GetFileInfoByIndex(INT64 index) {
assert(index <= SIZE_MAX); | {
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The scalar product between two vectors, a and b is de ned by a b= abcos( ); 0 ˇ (2. 9 The Maximum Principle 2. Established in 1978, O’Reilly Media is a world renowned platform to download books, magazines and tutorials for free. 12 Find the derivative of (x2 1)=(x 1). These are the lecture notes for my online Coursera course,Vector Calculus for Engineers. The simple goal of this guide is to demonstrate how to. Brown Physics Textbooks • Introductory Physics I and II A lecture note style textbook series intended to support the teaching of introductory physics, with calculus, at a level suitable for Duke undergraduates. Download James Stewart Calculus 8th edition pdf free. Get here NCERT Solutions for Class 12 Maths Chapter 10. of Statistics UW-Madison 1. As geometry is study of shapes, calculus is study of change, so it is an integral part of modern mathematics syllabus. Sample: 1B Score: 6 The student earned 6 points: no points in part (a), 3 points in part (b), 3 points in part (c), | {
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"openwebmath_score": 0.6265687346458435,
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"url": "http://wikibanking.it/vector-calculus-questions-and-answers-pdf.html"
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javascript, performance, beginner, php, html
$all_html .= '<h2 itemprop="name" class="tx-1 fw-8">';
$all_html .= $article_title; // article title
$all_html .= '</h2>';
$all_html .= ConstEQ::NEW_LINE; // required spacer for view
if ($array["m"]["g"]) {
$all_html .= '<p class="ro p-5 fw-6 tx-1 s16 r113">Near-Term Price Targets Computed on ' . date('l, d F Y \⏱ H:i T', microtime(true)) . '</p>';
$all_html .= ConstEQ::NEW_LINE; // required spacer for view
$all_html .= '<ul class="ro p-5 fw-6 tx-1 s18 r113">'; | {
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"tags": "javascript, performance, beginner, php, html",
"url": null
} |
ros, ros-kinetic, callback
Originally posted by mcamurri on ROS Answers with karma: 102 on 2019-02-17
Post score: 0
Original comments
Comment by PeteBlackerThe3rd on 2019-02-18:
Can you post the full error message please, we need to see all the detail to be able to help you.
Comment by mcamurri on 2019-02-18:
I've added a minimal example with full error output.
From the API docs it seems that all the boost::bind versions (11 and 12 out of 13) require you to also specify the tracked object:
tracked_object: A shared pointer to an object to track for these callbacks. If set, the a weak_ptr will be created to this object, and if the reference count goes to 0 the subscriber callbacks will not get called. Note that setting this will cause a new reference to be added to the object before the callback, and for it to go out of scope (and potentially be deleted) in the code path (and therefore thread) that the callback is invoked from. | {
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c#, properties
This feels really weird to me, but it does what I need it to do. I'm also thinking about having the setter throw an exception instead of setting _config to -1 when given an invalid value. Am I using Properties correctly, or have I completely misunderstood the point of them? No one has yet addressed the fact that you have chosen the wrong tool for the job.
What does Config represent? It looks like you should have chosen an enum where you chose an int.
public enum ConfigurationType
{
None = 0,
Type1 = 1,
Type2 = 2,
// etc.
}
You can get what ConfigurationType an int corresponds to quite easily:
ConfigurationType configType = (ConfigurationType)someInteger; | {
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special-relativity, solid-state-physics, fermi-energy
for the 1s electron of mercury (atomic number 80) this effect becomes significant; the electron approaches about 58% of the speed of light, ... | {
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bond, boiling-point, vapor-pressure
We can then write the equation for the mixture
P = x1 k exp (-Delta H vapp / RT)
The gas constant R is 8.31
If Delta H vapp is 40.8 x 10^3
We can make some progress, our value of k will be 519695
I used excel to then consider the tempertures required to get a vapour pressure of one for dilute solutions of glucose and I found that the boiling point of the solutions was described by the line T = m[2] + c where m was 0.4921 and c was 373. I used the solver to obtain the boiling points for the solutions.
Thus I have shown that ΔT=Kb Mi is true at least for dilute ideal solutions.
Now this will only work for dilute solutions, when we get concentrated glucose which will be what I call "damp sugar" things are going to change. One of my professional interests is in very concentrated solutions and the way that the activity functions change. I have an interest in things like 5 moles per litre solutions of sodium chloride and mixtures of things like choline chloride and ethylene glycol. | {
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# Chance of adjacent lockers with the same combination
One weird thing that happened to me in high school was that the combination lock on my locker had the exact same combination as the locker next to it. It always struck me that the odds were crazy on this, but I never calculated it.
The lock was a masterlock, the kind where you have 40 options for the first number, then 39 for the second (can't use the first number again), then 39 for the 3rd number (you can use the first number again for it).
• 1/59,280 chance that two locks have the same combination. (40 * 39 * 39)
• 1/29,640 chance that any specific combination is next to mine (w/2 lockers next to mine).
That gives a 1 in (59,280 * 29,640) chance that a specific combination is next to mine? Or a 1/1,757,059,200 chance.
This seems way too high, and there's probably something I'm missing here. Any thoughts on this calculation, or what it should be? | {
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"url": "https://math.stackexchange.com/questions/614569/chance-of-adjacent-lockers-with-the-same-combination"
} |
//Comparisons should be 19.
int[] merged = ms.merge(a, b);
System.out.println("After merging two arrays: ");
for(int i=0; i<merged.length; i++){
System.out.print(merged[i] + " ");
}
System.out.println("\nUsed " + ms.getComparisons() + " comparisons");
}
} | {
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"lm_q2_score": 0.8221891305219504,
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"url": "https://cs.stackexchange.com/questions/57726/why-does-merging-two-sorted-arrays-take-2n-1-comparisons"
} |
• @J.C.VegaO if it is still of interest I have an explanation for that: $p$ doesn't change sign in $(x_i,x_{i+1})$, while $p'$ does after $\xi_i$. Because $p$ goes to $0$ in $x_2$ while $p'$ has changed sign you have that $p+p'$ does the same and so has a root. Otherwise do a graph to make it clearer :-) Jan 18 at 12:33 | {
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"url": "https://math.stackexchange.com/questions/3355377/number-of-real-roots-of-px-px"
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thermodynamics, states-of-matter, combustion
Title: Burning vs Melting - when applied to cooking chocolate I'm aware melting is simply heat causing molecules to go from solid to liquid, and burning is a chemical reaction, normally with oxygen; but I don't understand how this applies to cooking chocolate.
See, when you cook chocolate naked on a pan, the chocolate will burn. However, if you cook a bowl of water with a smaller bowl floating on top with the chocolate in, the chocolate will melt and not burn. So, what's going on here? FYI, I'm not a physics major. Olin Lathrop captured something important, which is that the word "burn" does not always align to the chemistry definition of the word. But I did want to answer your question. | {
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slam, navigation, navsat-transform-node, slam-gmapping, gmapping
<param name="map_frame" value="map"/>
<param name="odom_frame" value="odom"/>
<param name="base_link_frame" value="base_link"/>
<param name="world_frame" value="odom"/>
<param name="transform_time_offset" value="0.0"/>
<param name="odom0" value="/husky_velocity_controller/odom"/>
<param name="imu0" value="/imu/data"/>
<rosparam param="odom0_config">[false, false, false,
false, false, false,
true, true, true,
false, false, true,
false, false, false]</rosparam>
<rosparam param="imu0_config">[false, false, false,
true, true, true,
false, false, false,
true, true, true,
true, true, true]</rosparam> | {
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"id": 28106,
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"tags": "slam, navigation, navsat-transform-node, slam-gmapping, gmapping",
"url": null
} |
Arctic Tern Migration Path, Froedtert Healthcare Jobs, Art3d Vs Smart Tiles, Adams Gas Reviews, Eddie Bauer Wooden High Chair Cushion, What Was The Purpose Of The Two Treatises Of Government, Mrs Dash Herb Seasoning, Down Under Definition, | {
"domain": "msurma.pl",
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"lm_name": "Qwen/Qwen-72B",
"lm_q1_score": 0.9817357237856482,
"lm_q1q2_score": 0.81161249732262,
"lm_q2_score": 0.8267117898012104,
"openwebmath_perplexity": 430.58297011142395,
"openwebmath_score": 0.7870026230812073,
"tags": null,
"url": "http://www.msurma.pl/ve00ubj5/ce2708-solving-system-of-differential-equations-with-initial-conditions"
} |
html, css, html5
1.2114-34.86316 6.4231-69.61201 15.9405-103.18546zm761.98496,101.59799h-609.58786c-.0414,43.61016 7.159,87.54256 23.8966,127.94783 15.0905,36.70744 38.161,70.13553 67.3649,97.03404 34.4165,31.87048 76.8843,54.55343 121.9428,67.23644 65.2151,18.37082 136.0196,16.64147 200.1507-5.3019 42.6625-14.58395 82.325-38.50952 114.0212-70.69197 27.771-28.03924 49.12266-62.27099 62.62002-99.32688 13.69849-37.32615 19.61521-77.22436 19.59164-116.89756z"/> | {
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"lm_q2_score": null,
"openwebmath_perplexity": null,
"openwebmath_score": null,
"tags": "html, css, html5",
"url": null
} |
Counterexample 106 from Steen and Seebach
As the title suggests, this post discusses counterexample 106 in Steen and Seebach [2]. We extend the discussion by adding two facts not found in [2].
The counterexample 106 is the space $X=\omega_1 \times I^I$, which is the product of $\omega_1$ with the interval topology and the product space $I^I=\prod_{t \in I} I$ where $I$ is of course the unit interval $[0,1]$. The notation of $\omega_1$, the first uncountable ordinal, in Steen and Seebach is $[0,\Omega)$.
Another way to notate the example $X$ is the product space $\prod_{t \in I} X_t$ where $X_0$ is $\omega_1$ and $X_t$ is the unit interval $I$ for all $t>0$. Thus in this product space, all factors except for one factor is the unit interval and the lone non-compact factor is the first uncountable ordinal. The factor of $\omega_1$ makes this product space an interesting example. | {
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"openwebmath_score": 1.000008463859558,
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"url": "https://dantopology.wordpress.com/category/normality-in-product/"
} |
robot-localization, gps, nav2, navsat-transform-node, ekf-localization-node
truck_simulation_launch.py
Demonstration Video: Video of back-and-forth movement and small jumps here
URDF Ackermann Plugin Code Snippet:
<gazebo>
<plugin name='ackermann_drive' filename='libgazebo_ros_ackermann_drive.so'>
<ros>
<!-- <namespace>/demo</namespace> -->
<parameter name="cmd_vel_topic" value="cmd_vel"/>
<parameter name="odom_topic" value="odom"/>
<parameter name="distance_topic" value="distance"/>
</ros>
<update_rate>30.0</update_rate>
<!-- wheels -->
<front_left_joint>first_wheel_left_joint</front_left_joint>
<front_right_joint>first_wheel_right_joint</front_right_joint>
<rear_left_joint>fourth_wheel_left_joint</rear_left_joint>
<rear_right_joint>fourth_wheel_right_joint</rear_right_joint>
<left_steering_joint>front_left_steer_joint</left_steering_joint>
<right_steering_joint>front_right_steer_joint</right_steering_joint> | {
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"tags": "robot-localization, gps, nav2, navsat-transform-node, ekf-localization-node",
"url": null
} |
wormholes
\end{equation}
The Roche limit for planets not tearing themselves apart is that the tidal acceleration of outside influences should not exceed that of the planet itself. In our case, this means roughly :
\begin{equation}
[(1-\frac{b}{r} (-\phi'' - (\phi')^2) + \frac{1}{2r^2}(b'r-b) \phi'] < -\frac{1}{r'^4} ((r'-2m(r')) (2m(r) + r'(-2m'(r') + r'm''(r'))))
\end{equation}
\begin{equation}
\frac{\gamma^2}{r^2} [(r-b) \phi' + \frac{\beta^2}{2} (b' - \frac{b}{r})]< -\frac{1}{r'^4} ((r'-2m(r')) (2m(r) + r'(-2m'(r') + r'm''(r'))))
\end{equation} | {
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python, performance, programming-challenge, fibonacci-sequence
def fibonList(x):
fibonSeq = []
firstT = 0
while mostList[firstT] <= x:
fibonSeq.append(mostList[firstT])
firstT += 1
yield fibonSeq
def powerset(iterable):
b = list(set(iterable))
for s in range(1, len(b) + 1):
for comb in itertools.combinations(b, s):
yield comb
def repWay(x):
ways = 0
for each in fibonList(x):
for i, combo in enumerate(powerset(each), 1):
for ea in sumOfList(combo):
if ea == x:
ways += 1
yield ways
def rangerepWays(x):
generalSum = 0
for i in range(x + 1):
for x in repWay(i):
generalSum += x
yield generalSum + 1 # + 1 because 0 = 0, while creating fib list I didn't incorporate 0 into fiblist.
for x in rangerepWays(10 ** 2):
print(x)
1- First: It works, but, unfortunately, is too slow.
I have tested the program with the given examples in the question and it works. It passed both. | {
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"tags": "python, performance, programming-challenge, fibonacci-sequence",
"url": null
} |
contour coordinates saves... Given value of a random variable also referred to by its traditional name, the Parzen-Rosenblatt window,... By its traditional name, the kernel density estimation python window method, after its discoverers the … is! Estimators ( KDE ) is a method to estimate the probability density function a. Your organization need a developer evangelist is just like a histogram but a... Window method, according to its discoverers: Symmetry such that \ ( )... Estimating the probability density function ( PDF ) of a given value of a kernel-density estimate using Gaussian Kernels estimate... Num_Variables ) a separate observation plot, prints the contour plot, prints the plot! Function that returns a probability for a long time, i could n't figure out how make! Using KDE ( ) for the analysis of the dataset the points where the first derivative changes sign... 2019 Reputation: 0 Likes received: 0 Likes received: 0 Likes received: 0 Likes received: Likes! Results and | {
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"lm_name": "Qwen/Qwen-72B",
"lm_q1_score": 0.9669140216112958,
"lm_q1q2_score": 0.8057532417643981,
"lm_q2_score": 0.8333246015211008,
"openwebmath_perplexity": 1111.0922776881075,
"openwebmath_score": 0.5756372213363647,
"tags": null,
"url": "http://konwakai.com/guild-wars-phnokqh/kernel-density-estimation-python-c63753"
} |
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