Can I leave my friend my body if I die

Question: So when I die I want my friend to keep my body parts in a jars and maybe make a mask out of my face or some thing like that. Can I do that? I'm only 17 so idk if my parents would have a say or if a will would even work for me being in parental control. Anyways thanks
Comment: I sincerely hope that you live long enough that the under 18 question is moot, by a lot.
Answer: It depends on where you live. In Washington, RCW 68.50.110 requires that

Except in cases of dissection provided for in RCW 68.50.100, and where
  human remains are rightfully carried through or removed from the state
  for the purpose of burial elsewhere, human remains lying within this
  state, and the remains of any dissected body, after dissection, must
  be decently buried, undergo cremation, alkaline hydrolysis, or natural
  organic reduction within a reasonable time after death.

Per RCW  68.50.130,

Every person who performs a disposition of any human remains, except
  as otherwise provided by law, in any place, except in a cemetery or a
  building dedicated exclusively for religious purposes, is guilty of a
  misdemeanor. Disposition of human remains following cremation,
  alkaline hydrolysis, or natural organic reduction may also occur on
  private property, with the consent of the property owner; and on
  public or government lands or waters with the approval of the
  government agency that has either jurisdiction or control, or both, of
  the lands or waters.

So cutting the body up and sticking the bits in a jar is illegal, but cremating or dissolving it and keeping the remains in a jar is legal.
As for parental permission, RCW 68.50.160 says that

A person has the right to control the disposition of his or her own
  remains without the predeath or postdeath consent of another person. A
  valid written document expressing the decedent's wishes regarding the
  place or method of disposition of his or her remains, signed by the
  decedent in the presence of a witness, is sufficient legal
  authorization for the procedures to be accomplished.

It does not require that the person be an adult.

Can I leave my friend my body if I die


What should I do when I have a variable-length sequence when instantiating an LSTM in Keras?

Question: In keras, when we use an LSTM/RNN model, we need to specify the node [i.e., LSTM(128)]. I have a doubt regarding how it actually works. From the LSTM/RNN unfolding image or description, I found that each RNN cell take one time step at a time. What if my sequence is larger than 128? How to interpret this? Can anyone please explain me? Thank in advance.
Answer: In Keras, what you specify is the hidden layer size. So :
<code>LSTM(128)
</code>
gives you a Keras layer representing a LSTM with a hidden layer size of 128.
As you said :

From the LSTM/RNN unfolding image or description, I found that each RNN cell take one time step at a time

So if you picture your RNN for one time step, it will look like this :

And if you unfold it in time, it look like this :

You are not limited in your sequence size, this is one of the feature of RNN : since you input your sequence element by element, the size of the sequence can be variable.
That number, 128, represent just the size of the hidden layer of your LSTM. You can see the hidden layer of the LSTM as the memory of the RNN.
Of course the goal is not for the LSTM to remember everything of the sequence, just link between elements. That's why the size of the hidden layer can be smaller than the size of your sequence.
Sources :

Keras documentation
This blog

Edit
From this blog :

The larger the network, the more powerful, but it's also easier to overfit. Don't want to try to learn a million parameters from 10,000 examples – parameters > examples = trouble.

So the consequence of reducing the size of hidden state of LSTM is that it will be simpler. Might not be able to get the links between the element of the sequence. But if you put a too big size, your network will overfit ! And you absolutely don't want that.
Another really good blog on LSTM : this link
Comment: Thank you for your answer. What if I lower the size of the hidden layer? say LSTM(64). What will be the consequences? Does it means lstm model has lower memory to capture long-term dependencies?
Comment: I edited the answer :)
Answer: Although this question has been answered I'd add a couple of remarks towards general neural networks design
As you know very NN has three types of layers: input, hidden, and output. Once this network is initialized, you can iteratively tune the configuration during training.
To optimize the network configuration we can use pruning.
Pruning describes a set of techniques to trim network size (by nodes not layers) to improve computational performance and sometimes resolution performance. The gist of these techniques is removing nodes from the network during training by identifying those nodes which, if removed from the network, would not noticeably affect network performance (i.e., resolution of the data). (Even without using a formal pruning technique, you can get a rough idea of which nodes are not important by looking at your weight matrix after training; look weights very close to zero--it's the nodes on either end of those weights that are often removed during pruning.)
You can find more here: https://stats.stackexchange.com/questions/181/how-to-choose-the-number-of-hidden-layers-and-nodes-in-a-feedforward-neural-netw


How to practice without a teacher?

Question: I'm going to join buddhist group which is in another city so I'll have few occasions to meet sensei especially because she is from USA and she arrives only few times a year to my country. So how should my practice look?
Comment: would help what tradition you will be meeting :)
Comment: I guess that "sensei" might imply Japanese.
Comment: Zez soto mixed with rinzai
Answer: Ask your questions (about how to practice without a teacher) to the Sensei when you meet her.
Since you appear to be taking refuge in the Sensei, her advice would be the most appropriate (in the near term).
Answer: Sutta-vinaya is your ultimate teacher. It is found in the books written by Bhikkhu Bodhi. Bhikkhu Bodhi is an American Buddhist monk from New York City. Ven. Bodhi has many important publications such as: A Translation of the Majjhima Nikaya , The Connected Discourses of the Buddha — a New Translation of the Samyutta Nikaya , In the Buddha's Words (An Anthology of Discourses from the Pali Canon), Great Disciples of the Buddha: Their Lives, Their Works, Their Legacy.. to name a few. As Buddhists, we should be familiar with the Suttas and if possible obtain our own copies. It is a sad fact that only we Buddhists who would not go to the original source for guidance. Do you find Muslims without the Quran or Christians without the Bible? It is only we Buddhists who are without the Nikáyas.
Having said that still it is very important to have a 'Kalyana Mitta (a noble friend), as it is much more important than all else for one who wants to walk this road less travelled. It is even more important than one's developed morality (Sila). Then that Noble Friend protects you from your own mind, until you are well established in the path.  Mind is a strange thing. It is always out to find others faults, and to justify your own thinking and actions. It is your Teacher, who could remind you now and then of this. A sense of 'hiri-ottappa' accompanied by mindfulness is to reflect on oneself only, and never let your mind to compare it to others (Hiri is an innate sense of shame over moral transgression; ottappa is moral dread, fear of the results of wrongdoing). Every time you do so, you get thrown away from this path. It is because of this mind, because of us trusting this mind that we never even now see the danger of Samsara, and we are forever in it. Thankfully I have such a noble friend. One can have only one or two such, the most. Otherwise you give into your mind again, and it decided what advice to take, and what to reject or ignore.  So I do hope that you  will find another Teacher close to you.
The most important thing to understand the Dhamma is to remember what is heard or read. Then follows the examination of the meanings of what is remembered. We tend not to do that. Just having a collection of books, or notes in the computer will not do. The process of learning the Dhamma goes through the stages of listening, remembering, constant reciting, mental observation and ideological understanding of the Dhamma. As per the scriptures, the self-study of Dhamma should thus have the following components:
Methodology of learning

It starts with careful listening with full attention (Suthaa).
Then what he has heard has to be registered in the mind (dhathaa).
The next step is to familiarize himself with what has been learned by reciting (vacaya paricita).
Then it has to be internalized with pondering over it, contemplating the meaning by applying it to yourself.  (Manasaanupekkhitha)
The next step is practising what one has learned to become a real knower of the teaching - The realization. It is the result of the above 4 actions.  (Ditthiya Suppatividdha)

How to practice without a teacher?


Engineering Mathematics and Mathematical Physics Books

Question: I would like to learn/brush up my concepts on Mathematics related to physics and engineering. I have found this book (Mathematical Methods for Physicists, by Arfken, Weber, Harris). This book covers almost all the topics that I need, However, it doesn't explain how and why things happen like this book (Elementary Differential Equations and Boundary Value Problems,by Boyce and Di Prima) explains the differential equations. Need something like the latter book to understand the mathematical concepts related to physics and engineering that would explain things elaborately.
Comment: @H.R. Actually, I am an electronics and communication engineering student. We need to cover topics such as Matrices, Determinants, Calculus(extensively), Vector analysis(Extensively), Probability(Extensively). In other words, we need to study topics in the book: Mathematical Methods for Physicists, by Arfken, Weber, Harris. This book covers almost all the topic that we need. However, I wanted to read a book that would explain things. I found a book by Mary L. Boas which I found enjoyable to read.I was searching for a book like that.
Comment: [This Post](https://math.stackexchange.com/questions/2175473/mathematical-physics-methods-in-mathematical-physics-books?rq=1) and [this one](https://math.stackexchange.com/questions/635060/mathematical-and-theoretical-physics-books?rq=1) can also be helpful. :)
Answer: Honestly, there is no one book which gives you the whole mathematics used in physics and engineering with enough details. If you want to dive deeply into concepts you should read special books for special concepts. However, here are some books similar to Arfken 's book you mentioned where some of them contain more details.
$1$. Mathematical Physics, A Modern Introduction to Its Foundations By Sadri Hassani. This book provides a nice balance between the details and spectrum of the concepts. It is much better than Arfken in my opinion. It tries to convey modern mathematical thinking. The materials are introduced in a smooth integrated way. I think it is a good choice.
$2.$ Mathematical Methods of Physics, Volume 1 and Volume 2 By R. Courant and D. Hilbert. This is a classic which still worth reading as has been written by two well known mathematicians. It provides nice rigor and a vast of concepts.
$3.$ Advanced Calculus for Applications By Francis B. Hildebrand. This is also a classic which is taught in some universities.
$4.$ Mathematical Methods for Engineers and Scientists, Volume 1, Volume 2 and Volume 3 By Kwong Ting Tong. A rather new book which worth looking at.
$5.$ Advanced Engineering Mathematics By Erwin Kreyszig. It is more like an encyclopedia than a book.
$6.$ Fundamentals of Mathematical Physics By Edgar A. Kraut. This one is a popular book in mathematical physics and people are satisfied by reading it. The text is user friendly. You can take a look at reviews in Amazon.
I should emphasize again that none of such books replaces a special book written for a special mathematical subject. They have to sacrifice details for saving brevity. So do not expect these books to provide a systematic step by step rigorous approach.
Answer: Advanced Engineering Mathematics by Erwin Kreyszig has pretty almost all the math that an undergraduate student in any branch of engineering might encounter.
Comment: I really hate this book! :D It is much worse than Arfken's book! It is just like a report which writes some formulas down without enough explanation. There are lots of discontinuties of thought through the book. :)
Comment: No one ever found it fun.  Though some schools do use it as a text.  It's certainly an encyclopedic reference work to find pretty much anything you need. Our love or hate can't take that away from it.
Comment: I can accept it as an encyclopedia but not as a book appropriate for learning. :)


Is it possible my raspberry pi to melt its plastic case at 55° degrees?

Question: I have simple question, since my raspberry is new and i don't know if its ok when its 100 % of the time at 55 degrees and basically my question is does my raspberry will melt the plastic case at this temperature?
Comment: No it won't. Period. The kind of plastic that Pi cases are made of melts at temperatures much greater that 55 C. Anyhow, if it could melt the case it would also melt its own board, which is made of plastic also.
Comment: PCBs are usually made of an epoxy-fiberglass composite which is considerablly more heat resistant than most plastics.
Answer: No.*
At 55°C, the raspberry pi cannot melt its case.
ABS plastic begins to soften at around 100°C.
Regarding the Pi being damaged, don't worry about it. Raspberry Pies throttle back their CPU speed if they reach 85°C.
*Actually there have been a few rare instances of a Pi melting its case or getting ridiculously hot. This happens when the SD card or CPU short out due to abuse. (like trying to run it on 12v)
Comment: Absolutely! Not a problem at all. At 85°C, you start to lose performance, so it's a good idea to keep your Pi cooler than that.
Comment: So , basically at 55°C its not problem ?
Comment: I wonder if a pi will function while suspended in boiling distilled water? Limits are easy to find, bit has anyone tried "suck it and see"? We might get lucky.
Comment: @WayfaringStranger, that is off-topic for this question. But **NO**, don't put a Pi in distilled water. The metal parts will quickly ionize the water, the conductivity of the water will increase until the Pi is shorted out. If you want to soak your Pi in something, use mineral oil.


How can I find someone online to mentor me on my first research paper?

Question: I am an undergraduate student, and I have an idea which I want to explore and write a research paper on. But I am totally new to this.
I don't have good CS community at my place.
So I can only look for a distant mentor.
Please tell me how and where (sites, forums) it is possible.
Answer: I would suggest taking to professors at your institution. If the semester is in session, you can go to their office hours; otherwise, you can email your advisor or another professor who knows you. Even if it's outside their area, they should be able to steer you in the right direction.
Answer: Answering your questions with suitable answers
for doing research you must have the following:-

A topic or brief subject on which you want to work. In CS field, start find faults and raising questions to yourself about the topic you learn, e.g. while learning sorting in Data structure, what other technique you can suggest while simplifying existing techniques, etc.
After the topic is decided, find who had done what work on your topic. It means to find references to your research work, because without references you cannot write research paper. e.g. search websites of IEEE or research gate.
Read any book on research methodology otherwise you will remain just a blogger. hahaha
Al last but not the least, find a research guide online or offline.

For any other queries, you can post me again
Answer: Depending on how serious you are (and what you mean by the word "research") your best bet may well be to search out professors in that area of research, no matter where they are in the world.  You could simply explain your position to them, and ask for they would be willing to work with you on the paper.
You may well get some "yes" answers.  This could also be a good way to start a relationship that could lead to a doctorate.
Good luck!


Writing parallel code for molecular computation

Question: I recently moved towards computational biophysics from an experimental science background. As of now, I am learning the fundamentals and doing some basic monte carlo simulations of LJ fluid on my desktop PC. However, when I tried to run my code on the cluster, it was equally or more slower than my desktop. Later, my lab mates told me to write my code suitable for parallel computation. I have no idea how to do that. Is there any resource, book aimed for people who are not very proficient in computer science, that can teach them about basics of such programming and necessary tools.
I wrote my code on c++, I am willing to move to fortran as well.
Answer: As was mentioned in the comments, A good, simple book/resource on Parallel Programming in C++ for scientific computing already gives an answer to the more general question of learning about parallel programming.
Having said that, a simple Lennard-Jones Monte Carlo program may not be a bad project to attempt, if you decide to go ahead and learn about parallel programming. The OpenMP approach is relatively easy to understand and implement. Many compilers have a -fopenmp flag, which will switch on the processing of any OpenMP pragmas in the code. A typical pragma is one that is applied to a for loop (or in Fortran, a do loop), to divide the iterations amongst the parallel threads. As an example, if you wanted to sum up $N$ numbers, and you have $P$ threads available, each thread could sum up (approximately) $N/P$ of the numbers, in parallel, and then the results can be combined at the end. You would need to learn some basic OpenMP concepts first: the difference between private and shared variables, and crucially the idea of a reduction variable, which would hold the result of the summation. But it doesn't take too long to master OpenMP at this level.
The point is that, in the simplest Monte Carlo program, the time consuming part is exactly such a loop. When you consider moving an atom, you need to compute the sum of Lennard-Jones pair potentials between it and all the other atoms, before and after the move. This assumes that you have a relatively small system, and are not using sophisticated techniques such as domain decomposition / neighbour lists to speed things up. Basically, if you can parallelize a simple summation loop, it is not a huge stretch to parallelize the single-particle potential energy calculation.
On your cluster, it is quite possible that each node consists of several cores with access to the same memory: if so, then you could use OpenMP to run on a single node, with each thread corresponding to one of those cores. So, in principle, best-case scenario, you might get a speedup of however many cores there are per node.
For larger-scale Monte Carlo, a more sophisticated approach may be needed. Parallelizing large-scale Monte Carlo codes can be done (e.g. by using domain decomposition and writing a program that uses MPI), but is more fiddly and needs more care (because of the need to ensure detailed balance) than this simple OpenMP example.
If you decide to proceed in this way, you should definitely follow up some of the resources mentioned above first. But after you've learned the basics, it's actually just a question of inserting a very few extra lines in a simple program to sum up a set of numbers, as a test, and then doing a similar thing to your code, and compiling with the appropriate option.


Is it possible to change the USB connection volume?

Question: At work I have my ringer volume set to 1/30 (which still seems very loud...). When I connect the USB cable to sync or charge I still get a very loud notification sound. Is it possible to reduce the volume when I plug it in? Failing that, is there a way to turn the USB connectivity sound off?
Answer: The only way I've found to turn of the "da-da-duh" sound you get when the phone connects to a power source or to Zune, is by toggling the Ring+Vibrate/Vibrate to vibrate. Its not as much of a hassle as I thought it would be. Right before I plug it in, I click the volume rocker, toggle to vibrate, plug it in, and toggle back to ring+vibrate. It take about 1.5 seconds.
The only sounds I can explicitly turn off on the HD7 are
Reminders, Key Press, Lock/Unlock, Camera Shutter and "All Other Notifications". Even shutting of "All Other Notifications" doesnt mute the usb connection sound.
I know it's not an elegant solution, but until WP7 gives us the ability to change individual volumes, this works for me.
Answer: You can do this by editing the registry (I use wp7RootTools):

Using your registry editor, browse to Current User\ControlPanel\Sounds\BatteryCharging
Change the value in the InitVol key to 0 (or whatever volume you prefer - on my phone, it was initially set to 75)

That's it! Note that you can also change the battery charging sound by altering the Sound key to point to a different wma file.


How does one make vodka from potatoes

Question: I ask this as a Russian born person of which would like to show off to friends and family. As a Russian born US citizen who occasionally gets playfully teased about our stereotypes, I would like to prove to them how stereotypical I can be.
Comment: Do you have distillation experience?
Comment: No I do not have any experience in brewing in general much less distillation, but I would be open to learning.
Comment: Also is it legal to distil where you are? A very important question.
Comment: From what I just looked up it seems to be legal but I need a license. I'm in the VA
Answer: You could start with this question from this forum to know how to turn potatoes into a sugary solution fit for fermentation.
Mind you, mashing not only means to mush the potatoes, but to add crushed barley malt and water. The crushed barley malt enzymes will turn the potato starches into sugars. Click on the tag "mash" to get more information.
However, after the fermentation process, vodka needs distilling, and that is a very specific theme, more subject to different laws, I suppose differing from state to state in the US, and also differing from country to country. And talking about distilling on HB SE seems to still be not generally accepted.
Comment: I accept talk about distillation, so long as there is some talk of mashing, fermenting etc... Pure distillation questions should probably be asked on Chemistry or Engineering SE. As they will have far more experience than most of us. Saying that I did make a 400l batch of Gin last year, with hops in :)
Comment: Thanks for the clarification, @Mr_road!

How does one make vodka from potatoes


How to do the land maneuver if I got complete thrust loss after liftoff with runway ahead?

Question: I am flying a single engine aircraft and after liftoff in air at low height, I lost the engine but I till have some runway length ahead, what should I do? Land straight ahead? How could I tell if I still have enough runway length to do the land maneuver and full stop on the runway? How should I perform the landing maneuver, quickly idle thrust and pitch down to stop the climb rate and then do a pitch up flare?
Answer: At low altitude engine loss you have no choice but to land straight ahead. Anything but the slightest heading adjustments will most probably end catastrofically. Your memory items are (at least, depends on complexity of aircraft):

Gently but decisevily lower the nose
Close throttle
Mixture cutoff
Close fuel valve
Adjust airspeed for landing
Flare and land
Now is the time to worry whether or not you have room to stop. Brake in a controlled manner and avoid objects if possible.

Should you have the time and composure at any moment during the predicament, radio "mayday mayday mayday [your callsign] engine out"
Comment: 8. Try to crack your door open before hitting anything.
Answer: How do you determine if you have enough runway ahead? That's a tricky one, and in this situation you quite possibly have milliseconds to make that determination. It's going to be an estimate at best because you certainly wont have time to do any calculations. As a general rule I'd say if you have around half the runway length left you're probably good.
In this situation you should definately make a straight ahead landing, even if you dont have enough runway left.
Cut the throttle (if you have any left, in say a partial failure/rough running), pitch down to landing attitude, and execute a normal glide approach landing.
Comment: "As a general rule I'd say if you have around half the runway length left you're probably good."  That depends entirely on the overall length of the runway!
Comment: If you've lost power, you really don't have a choice.  Your best bet (probably your only bet) is to use whatever runway you have to slow as much as possible before crashing into whatever's at the end.
Comment: The only time I can think where you *might* consider not landing straight ahead is when you are taking off from a short runway and your power fails as you are over a longer cross runway. Making a turn to land on the longer runway might be advisable, but even then you risk stalling in the turn and converting a perfectly safe landing into a crash.
Comment: @DJClayworth: Or perhaps a parallel runway, if there's no traffic using it.  E.g. my often home airport used to have an (approximately) 5000 ft GA runway paralleling the 10,000 ft commercial one, so there was a couple of thousand feet of the long runway extending beyond each end of the shorter one.


Where should I place my Open Source license file in my project?

Question: I have a license file for my open source project.
Where in the project's directories hierarchy should I put that file?
Answer: I agree with the other answers on the principal - it should be easy to find, although I'm not sure the examples his answer provided are are indeed the most common.
Projects created on (i.e., by) GitHub have their licenses placed in a file named LICENSE (no suffix) in the project's root directory. Another common idiom for GitHub projects is to use LICENSE.md to gain markdown formatting for it. COPYING and COPYING.md are also fairly common, although I must say that, IMHO, calling the license file "copying" misses a great deal of the point of open source - it's not about freely copying the content, it's about collaborating on it (in other words - "free as in speech, not as in beer").
Answer: It should be easy to find. I'd say in the root of your project as a license.ext or as part of the readme.ext (where .ext would of course be the appropriate extension of the format it is in). Those are the most common ways I've seen in PHP open source projects.
Of course multiple variations of the license file are seen as text file, markdown file, lower case, upper case, etc (License.txt, LICENSE.TXT, LICENSE, License.md)
Also most of the times on large scale projects the license is included in every file in the so called PHPdoc "page" section (again, this is in PHP projects).
On small scale projects, most commonly hosted on GitHub, it is included in the README.md file, which GitHub will parse and show on the project's home page.
Answer: The License is the agreement between you, and the user of the project.
The license file is just a file that defines the agreement.
It should be clear for the user what license he's getting, and what that license applies to, but there are no hard rules where to put the file, and what to name it.
For example, the Apache license advises that you put a text header in each file, which links to the Apache license online, and they don't advice putting the text of the license in your project at all, and from what I've seen, this is common practice for this license.
Some other projects don't have such a license header in their files, but just have the license file in the root of the project. Often these files are named something like license.txt, or the shouty variation LICENSE.TXT, or just license. Sometimes the license location is also included in a readme file.
The important part is that it is clear what the license applies to, and it's easy to find.


Why is my mint plant growing like this?

Question: Hi, I bought a mint plant from Walmart, figuring I can repot it and make it grow bigger. However it just keeps growing taller. I have 6-7" of just stem, with leaves on top. How/where should I trim it to make it bushier/fuller please?
Answer: I agree with both previous answers - your mint needs a lot more daylight. that's why it's getting tall and lanky, shortage of light. They really prefer full sun but also grow well in partial shade (so half a day's sun). Find a bigger pot with drainage holes, only one size bigger, move it into that using fresh potting soil, water it well and allow to drain down freely. Then cut it down to about 2 inches and stand in well lit place, like a windowsill with good daylight and preferably some sun. Water when the surface of the soil feels just about dry to the touch, water thoroughly and empty any outer tray or pot after 30 minutes so it's not left sitting in water.
Answer: Liza, it appears to me that your plant needs more sun exposure. Try putting the plant near an east facing window if possible. In the more northern latitudes, a south window has worked best for me (44 degrees north).
Comment: It looks like there are at least two separate plants in one pot. Disentangling the roots and putting them in two pots would help. As for "trimming" it, mint will regrow from the roots whatever you do to it. The usual problem growing it outdoors is how to keep it under control, not how to keep it alive!
Answer: I also would suggest you upgrade the plant to a bigger pot (one size bigger) or put it in the ground if possible--not sure if this is an options for you. The plant is most likely root bound and there is probably a lack of nutrients in the soil. Lastly a bit of sunlight would help as in the previous comment. Mint likes partial shade to full sun. Good luck!
Comment: thank you so much, I appreciate the community help!

Why is my mint plant growing like this?


Where is the link to the Privileges page?

Question: I couldn't find the link to reach the Privileges page. So my question is: is there no link/button that does that or I just couldn't find it?
Comment: +1,because i was also facing the same problem!!
Answer: The way I always find the privileges page is:

go to the Help Center (which is linked from the drop-down menu which is always at the top right of the screen on every page on the site)
scroll down to the "Privileges" section and click on "View a full list of privileges you can earn"

There you'll be able to see a list of all privileges, both those you've earned and those you haven't.
Answer: One way will take you two clicks:

Click the Badges button on the ribbon
On the Badges page, click the Privileges link in the window at the top-right


How do you make a water shader?

Question: I'm working on a minecraft-like world and recently saw this video with a water shader.  I searched but couldn't find any good info on how to do something similar.  Maybe I'm just googling the wrong thing.  Does anyone have any resources on how to do something like this?
minecraft water shader video
Answer: A long time ago, when I was programming similar water simulation, I used this as a source. It's written in C++/OpenGL. You can find there PDF with description and also source codes.
You can see, there are faked waves - if you don't want them there, you just don't have to use "noise" textures.
Comment: And if you want better (more realistic) water simulation, you can use one of these: http://vterrain.org/Water/

How do you make a water shader?


Bone Constraint/ Location rotation issue

Question: Trying to get my model to clench his fist with the location rotation bone constraint however when applied the bone barely rotates at all. Is there something i left out?
Blend file
Comment: what location rotation bone constraint are you talking about? I don't see any for your fist. Note that your Pivot Point is in 3D Cursor mode, maybe your problem comes from there?
Comment: I may have added the previous blend file. But when i add the constraint and try to rotate it, it moves  very slowly and when i move the bone above the finger tip and warps the entire palm.
Comment: please link the file with the constraint so that we can see the problem
Comment: Sorry disregard you were right its the 3D cursor mode. I didnt know that changed to that nor do i understand how it changed to that because i never touched it. thank you!
Comment: so did it fix your problem?
Comment: Yup it did, the fingers are moving properly now
Answer: Switch your Pivot Point setting from 3D Cursor to Median Point.


Make closing questions proportional to participation levels

Question: When a question has been found valuable by dozens if not hundreds of community members who have answered, commented, and voted, this should not be able to be overridden by 5 empowered users. The arbitrary views of literally 1 hand full of individuals should not override many multiples more.
Comment: That a question is popular is in no way an indication that the question is on topic for the site.  Popularity in no way indicates on-topicness.
Comment: It takes only a set of another five empowered users to reopen the question.
Comment: There's a lot of spam and nonsensical posting that can get pretty popular.
Comment: When it is closed it is not deleted. It only takes an hand full of empowered users to reopen questions.
Comment: @ChrisMarisic It implies none of those things.  It implies only that it's popular.  Spam can be popular, nonsense can be popular, and content without value can be popular.
Comment: If it's popular AND not relevant it should be popular for empowered users to take action on a scale much more substantive than a spam posting or nonsensical posting.
Comment: @Servy that would imply that's valued content and both understood and not spam.
Answer: Just because something's popular doesn't make it on topic for a site.
We've seen this time and time again.
Stack Overflow (and by extension Stack Exchange) should not be seen as a repository for all knowledge on a subject. They are question and answer sites with restricted scope.


what's the difference b/w MMC.exe and certmgr.msc

Question: can anyone explain what's the difference b/w MMC.exe and certmgr.msc? MMC's file-> snap in functionality seems weird. some certificates appear in MMC when we select computer account from add/remove snap in but they do not appear in certmgr.
Answer: Certmgr.msc is an MMC snap-in.  MMC is simply the windows GUI shell for most administrative and even some non-administrative snap-ins.  Snap-ins load different functionality to work with different parts of the system or network.  You can create custom MMC views that load multiple snap-ins at once.  If certmgr.msc is displaying different results than when you load the MMC window it is most likely not pointing or loading from the same location.
More about MMC with references: http://en.wikipedia.org/wiki/Microsoft_Management_Console
Here's an existing SuperUser post that talks about changing the certmgr.msc container: https://superuser.com/questions/249484/how-can-i-start-certmgr-msc-for-computer-account
Answer: MMC.exe is the host process to certmgr.msc. So comparing the two is wrong the wrong way to look at it already :)
What happens here is that there are two sides to the certificate store on Windows. One is the system-global store, the user is user-specific. certmgr.msc unless reconfigured always shows you the current user's certificate store (checked in Windows 7). This is also shown in the caption bar of window.
So the difference here is natural because they are two different collections of certificates. Depending on the system there can be an overlap, but usually that is minimal.
Let's say you'd be installing an SSL (server) certificate then usually that would go to the system store, while those root certificates for your browser would go to the user-specific store.
This is more visible when you do code-signing, where you have to specify the store when you sign the program.
Answer: MSC is a file extension for a Microsoft Management Console(MMC) file format used by Microsoft Windows and is a collection of various snap in tools to simplify administration of a computer and create automatic tasks.src
MSC extension are also known as Microsoft Saved Console Files.
Users can create and customize MSC files to publish a collection of tools or utilities to other users through email, network sharing or web posting. It can also be assigned to other networks, users, and groups with policy settings. System administrators may provide restrictions by customization.
src


Is pneumonia contagious?

Question: If a healthy person is near a person that has pneumonia, is there any risk of infection for the former?
If so, how is it passed on? Is it via coughing / sneezing or skin contact?
Answer: Mostly it depends on the cause of the pneumonia.
Pneumonia is the name for infection or inflammation of the lungs. It can be primary or secondary. A good example of the difference is pneumonia caused by the influenza virus.
Influenza affects the lungs directly. That's a primary pneumonia, and yes, this is contagious, as the air one coughs out contains droplets carrying the virus. Pneumonia caused by viruses is more common in children and young adults (except for influenza, which affects all age groups), and is therefore contagious to people who have never been exposed to the virus - usually other children/young adults. In general, primary pneumonia tends to be more contagious, and besides viruses, it can be caused by mycoplasma and tuberculosis. These are contagious.
The damage done by the influenza virus in the lungs leaves the person susceptible to attack by bacteria that would not normally gain a foothold in the lung. This is secondary pneumonia, and because your lungs are not damaged - and you already have the same bacteria in your mouth and throat as someone with secondary pneumonia but are not ill - you are much less likely to get sick from being exposed to bacterial pneumonia than from someone with viral pneumonia.
Similarly, pneumonia is more common in smokers with damaged lungs, or in people with some degree of decreased immunocompetence. Alcohol, other drugs, and people with swallowing disorders can aspirate leading to pneumonia; surgery or chest injuries where deep breathing hurts can also lead to pneumonia. These pneumonias aren't likely to be contagious. Finally, some pneumonias are caused by exposure to chemicals. Since there's no infectious agent involved, you can't be affected.
There are now vaccines against some of the bacterial pneumonias, so vaccines against influenza and others help.
Since you might not know what kind of pneumonia someone has, practicing good hygiene is always a good idea.
Pneumonia Mayo Clinic
Pneumonia
Answer: Pneumonia may be contagious if it is caused by an infectious microbe. But if pneumonia is caused by chemical fumes or other poisons, then it is not contagious.
If treatment for pneumonia is administered early on, then the time pneumonia is contagious for is shorter. For example, a person with bacterial pneumonia will stop being contagious within two days of taking antibiotics. For other types of pneumonia – like the one that can cause tuberculosis – the treatment may have to be administered for at least two weeks before a person is no longer contagious.
On the other hand, individuals with viral pneumonia are less contagious after symptoms have subsided. The key is to reduce your ability to contaminate others by utilizing proper hygiene and avoiding others as best as possible.
Bacterial pneumonia can be caused by different types of bacteria, including streptococcal pneumonia (most common in adults), chlamydophila pneumonia, and H. influenza type B pneumonia (most common in children).
The common signs and symptoms of bacterial pneumonia include high fever, cough with phlegm, chills, chest pain when breathing or coughing, rapid breathing, shortness of breath, and loss of appetite.
Bacterial pneumonia is very contagious, so beginning antibiotic treatment right away can reduce your contagiousness.
Viral pneumonia is caused by a virus and commonly affects children. Viral pneumonia may clear up within three weeks, but does increase the risk of bacterial pneumonia. Symptoms of viral pneumonia are similar to the flu with fever, aches, and cough. Symptoms may worsen within the first two days, then proceed to improve.
Viral pneumonia is highly contagious and can actually spread quicker than bacterial or fungal pneumonia.
There are three subtypes of fungal pneumonia: coccidioides, histoplasma, and cryptococcus. If a person with a weakened immune system inhales a fungus that's how they can become sick. Symptoms include fever, dry cough, fatigue, and shortness of breath. Unlike other types, fungal pneumonia is not contagious, but symptoms may appear worse in those with weaker immune systems.
Aspiration pneumonia occurs when a person inhales food or other objects into their lungs. Although not contagious, aspiration pneumonia can be life-threatening, so immediate medical attention is required.
Walking pneumonia is a milder form of pneumonia that presents symptoms similar to a cold. Those symptoms include low-grade fever, persistent dry cough, fatigue and tiredness, shortness of breath, chest pain, and loss of appetite. Walking pneumonia is less severe than full-blown pneumonia, yet it can still be transmitted through droplet infection. Steering clear of others can help reduce transmission, along with covering your mouth and nose when coughing or sneezing.
Source: Is pneumonia contagious?

Is pneumonia contagious?


Can MetaMask be used as remote node for back end, and not require users to have plug in?

Question: I am building a web app that would track events/transactions made by contracts on the chain. At this point I am considering hosting a geth node on AWS EC2 in order to use in my web3.js initialization object. Would it be possible to use the MetaMask service instead of hosting my own node, just to probe the chain, without requiring my client side users to download the metamask plug in in order to use it?
Answer: MetaMask doesn't actually host any nodes! So if you want to write applications without the overhead of hosting your own node in the cloud, you can point your app to Infura. Checkout the site here: https://infura.io/.
You just need to make an account, then point your app to our endpoints. Basically all you need to do is replace http://localhost:8545 with https://"NETWORK".infura.io/"APIKEY", where "NETWORK" is either one mainnet, ropsten, rinkeby, kovan, and where "APIKEY" is the key you will get when you sign up!
You will then be hitting the same endpoints as MetaMask, since they send your transactions to Infura by default.
Comment: WOW thats pretty much exactly what i was looking for, I dont know why it was so difficult to stumble across. Doesn't hurt that its free either! I am going to experiment with my EC2 server and this and use whatever is less hassle. Thanks.
Comment: I'm glad it all worked out for you! :)


How to block images and their ALT tags on Firefox?

Question: I use this addon to block images in Firefox https://addons.mozilla.org/en-US/firefox/addon/image-block/ . And this one to block in Chrome https://chrome.google.com/webstore/detail/block-image/pehaalcefcjfccdpbckoablngfkfgfgj . The Firefox one blocks the images and displays alt text in place of images but the chrome one does not . Is there any way to not display alt text when images are blocked?
Answer: You can use uMatrix instead. Whitelist the other types of resources for every site (such as cookies and scripts), and then control images as you want:

uMatrix
Point & click to forbid/allow any class of requests made by your
  browser. Use it to block scripts, iframes, ads, facebook, etc.


What should we do about this poor quality answer?

Question: There is an extremely low-quality answer on the question "Largest integer factored by Shor's algorithm"
This answer is clearly poorly received by the community: It sits at -9 score and has received many flags indicating it is of low quality and requesting deletion.
The decision of the moderators at the time was to decline to use mod powers to delete it, and the prescribed solution was:

... It will thus not be removed by moderators. Any flags asking for this will be declined....
... I won't stop anybody from voting to delete this A[nswer] themselves (using their 20k+ privileges) or from recommending deletion in the low-quality review queue....

I happen to disagree with this proscribed solution, for the reasons stated below.
Issues with proscribed solution
There are two methods that were listed as to how this answer could be removed:

20k+ reputation users can vote to delete it
reviewers in the low-quality review queue can recommend deletion

While the following mechanisms will be ignored:

Flags indicating low-quality and/or requesting deletion, irrespective of how many of these flags accrue.

Unless it can somehow resurface, the time for this answer to be present in the low-quality review appears to be long past. This eliminates one of the available options for deletion of this answer.
As for the other: There are 10 users with 20k+ reputation. Some of them are inactive. Two of the active 20k rep users are moderators who cannot "vote" to delete, as they can only "choose" to delete, which they must abstain from doing in this case.
At least one of our 20k rep users has left a flag on this answer, and there are 2 votes for recommended deletion already.
Unless one of the few remaining candidates finds their way to this answer, it will not receive the requisite number of deletion votes.
I would like to use this meta question to explicitly ask the community:
What should be done with this answer? Are we content with the proscribed solution(s)?
I understand the hesitation to use mod powers to delete the answer: We should let the community decide is the mantra when such decisions come up. And that's a good thing, and the right way to do things.
However, it seems that "The community" should represent more than the top 10 users. And the current options do not appear to reflect this.
Currently, even if every single user but the top 10 vote this answer as low-quality and recommend deletion, they will be ignored.
What does the community feel about this situation?
While responses from the moderator team are of course welcome, I would like to see responses from members of the community at large.
Answer: Given that the answer is mainly a link to the website of what appears to be some terribly executed scam trying to get people to give them money for a non-existing product, I would argue that it's reasonable to delete it as spam.


Android USB port suddenly functional

Question: I did system update on my android device and after some days, i discovered my phone which used to fully charge under two hours could only charge around 10% in an hour. I couldn't connect via the USB to the computer anymore.
So today after i made up my mind i was going to take it to a repairer, everything suddenly returned to normal. I don't know how i can explain that. Should i still take it there or keep using it ?
Answer: I would continue using it.

Could of just been a setting that went unnoticed
Could of been a glitch in the actual wire (maybe the connectors on eac end or the wire itself)

There's a number of things it may of been but if it's working fine now, I'd recommend just using it.  "If it ain't broke don't fix it".

Android USB port suddenly functional


Orbit Maneuvering

Question: I am working on a project of simulating orbit maneuvering. I have interfaced SGP4 with my current simulation code, however I realized that the orbit maneuvering cannot be done using SGP4. I am aware of the methods where all the perturbations are integrated and the state propagates. However, I haven't been able to find resources for doing the same. What are some good resources/modules which can do so. In GMAT I cannot add custom orientations as thrust that I am giving is dependent on the orientation of the Satellite. I also want to know the actual process which is followed while simulating orbit maneuvering of Satellites. (From the state vectors to the propagate step to the error convergence)
Comment: Orekit could be a good option.
Answer: It's difficult to do with SGP4, since it's a mean element theory - here's a pretty good post on what that means: Nuances of the terms (mean / osculating / Keplerian / orbital) elements
So if you take the state vector given by SGP4, apply a delta-V to it, and try to stuff the elements back into a TLE, you're not going to get exactly what you expect.  It really depends on what level of accuracy you need and how far out you're interested in propagating.
It's an ugly hack, but I have seen people simulate low, continuous thrust maneuvers by manipulating the drag parameter of the TLE.
Comment: Thanks for the answer. I do understand that using SGP4 is not an option so I actually want to know the method that I should follow. How to propagators of GMAT or STK do it? I haven't been able to find any theory on the same. Or if there is any other solution to it then my problem is solved. I have already tried it using SGP4 and it didn't work.
Answer: If you want to use GMAT, I would recommend writing your own GMAT script to interface with Python. The good thing here is that GMAT is high fidelity, so you can leverage that without having to recode it. Moreover, if your thrust is to be applied based on the orientation of the spacecraft, you can define a spacecraft body reference frame and define your thrust vector on each thrust arc in that frame.
If you want to code it up from scratch, which can be a fun challenge, maybe will my code be handy. It has locally optimal control laws for continuous thrust propulsion and finite burns, all in the RNC frame.

Orbit Maneuvering


Did prophet Muhammad saw ever give in to his anger?

Question: I know this is probably a very stupid question but today something happened with me and I was raging with anger and told myself, "Calm down your prophet never gave in to his anger". But then I realized what if it wasn't true I mean he was a human. If anyone could explain sorry for my bad English
Answer: There's multiple ahadith which indicate the Prophet became angry.  However, precisely how angry, and for how long, is probably difficult to ascertain.

Narrated Abu Musa Al-Ash'ari: Allah's Messenger was asked about things which he disliked, and when the people asked too many questions, he became angry and said, "Ask me (any question)." A man got up and said, "O Allah's Apostle! Who is my father?" The Prophet replied, "Your father is Hudhaifa." Then another man got up and said, "O Allah's Messenger! Who is my father?" The Prophet said, "Your father is Salim, Maula Shaiba." When `Umar saw the signs of anger on the face of Allah's Messenger, he said, "We repent to Allah."
Sahih al-Bukhari 7291
Narrated `Abdullah: The Prophet divided and distributed something as he used to do for some of his distributions. A man from the Ansar said, "By Allah, in this division the pleasure of Allah has not been intended." I said, "I will definitely tell this to the Prophet." So I went to him while he was sitting with his companions and told him of it secretly. That was hard upon the Prophet and the color of his face changed, and he became so angry that I wished I had not told him. The Prophet then said, "Moses was harmed with more than this, yet he remained patient."
Sahih al-Bukhari 6100
Ibn 'Umar reported: One day while the Messenger of Allah was giving sermon he suddenly saw phlegm on the wall towards the qiblah (the direction to which Muslims turn in prayer) of the mosque. So he became angry at people. He then scraped it and sent for saffron and stained with it. He then said: When any one of you prays, Allah, the Exalted, faces him: he, therefore, should not spit before him.
Sunan Abi Dawud 479 [grade: sahih]
Narrated 'Aisha: Whenever Allah's Messenger ordered the Muslims to do something, he used to order them deeds which were easy for them to do, (according to their strength and endurance). They said, "O Allah's Messenger! We are not like you. Allah has forgiven your past and future sins." So Allah's Apostle became angry and it was apparent on his face. He said, "I am the most Allah fearing, and know Allah better than all of you do."
Sahih al-Bukhari 20

Other examples are: Sunan Abi Dawud 2182, Sahih al-Bukhari 2359, Sahih al-Bukhari 6112, Sunan Abi Dawud 2700, Sahih al-Bukhari 7139.


Another term for "accounts payable"?

Question: I'd like to know the term that's used to describe a list of payables that a company needs to pay at the end of the month (or any specific period)? "Accounts payable" seems to be tad technical. I'd like to know if there are other words for it.
Comment: *bills*, *invoices*
Comment: _Payments due_ would be a less jargony expression.
Comment: @drew But aren't invoices more on those items that a company needs to receive (e.g. Company A sent an invoice to Company B so that they'll pay Company A for the services rendered) rather than what the Company A needs to pay?
Comment: The term you need is *trade creditors*, or simply *creditors*. That was the slightly more old fashioned way of saying *accounts payable* by accountants. In the same way *trade debtors* became *accounts receivable*. I speak as a retired accountant who saw much change in the lifetime of my career.
Answer: Some others, for what it's worth:

Expenses
Overhead
Monthly Outlay
Expenditures

Google
Answer: From 'businessdictionary.com':
invoice:
A nonnegotiable commercial instrument issued by a seller to a buyer. It identifies both the trading parties and lists, describes, and quantifies the items sold, shows the date of shipment and mode of transport, prices and discounts (if any), and delivery and payment terms.
In certain cases (especially when it is signed by the seller or seller's agent), an invoice serves as a demand for payment and becomes a document of title when paid in full. Types of invoice include commercial invoice, consular invoice, customs invoice, and pro forma invoice. Also called a bill of sale or contract of sale.
account statement:
General: Summary of all transactions with a customer or a supplier that occurred over the previous month, quarter, etc., and their effect on an open-account balance. Also called a statement of account.
Read more: http://www.businessdictionary.com/definition/account-statement.html
Read more: http://www.businessdictionary.com/definition/invoice.html
Comment: But aren't invoices more on those items that a company needs to receive (e.g. Company A sent an invoice to Company B so that they'll pay Company A for the services rendered) rather than what the Company A needs to pay?
Comment: Yes, if company A sends an invoice to company B, the company B should pay to the company A and vice versa. If the full payment is not done, the remaining is 'arrears' that B should pay to A or A should receive from B.

Another term for "accounts payable"?


Which course to take? Optimal control? Nonlinear control?

Question: I have tried to compare two courses, and there seems to be some overlap, but not as much. Which method is better when controlling a nonlinear system? Also, what is the main difference between the two?
Comment: This looks like an [academic guidance question](http://meta.engineering.stackexchange.com/q/261/1832). Such questions often involve personal choice and can probably be better answered by an adviser or counselor. We do not believe this site's format is well-suited to such questions, which are therefore considered off-topic.
Comment: In case the nonlinear control course features Lyapunov stability and you haven't been taught that yet, you might consider that one. Lyapunov stability is probably one of the most important concepts of control theory.
Answer: In nonlinear control theory, you will recognize most concepts such as controllability and observability where the linear case is often a special case of the nonlinear case. I would highly recommend digging into linear control theory first if you have not done so. Depending on the course you take, concepts such as Lyapunov stability are discussed here, which is a very important concept.
In contrast, optimal control is rather independent of the underlying system, be it linear or nonlinear and has therefore overlap with both, depending on what type of optimal control problem you look at. I would say that it has a broader scope since you will find optimization problems everywhere in different fields of research. Especially important is model predictive control which solves optimal control problems on a receding horizon and is one of the most-used control schemes in the industry (apart from PID control) because it can handle state and input constraints explicitly (which most other types of control fail to achieve).
All in all, I would recommend going this path:
Linear control theory => Nonlinear control theory => Optimal control theory
Comment: I agree with the answer, although it is worth weighing the options in the context of the intended application of the controls algorithms the OP needs to address, since controls is a mature and therefore vast field. For instance, MIMO, robust control and Kalman filtering are generally taught as a part of the linear control theory, some of which may be beyond the scope of what is required by the applications of interest.
Answer: In control systems, the main focus is the design of a controller for machines or robots, here we mainly deal with linear systems application of linear control theory.
While non-linear systems is an advanced topic, where we deal with advance and mathematically more complex systems.
If its ur first course in control systems or automatic control. Go for the linear control system, but if you have a basic background of controls then you can go for non-linear control.
Comment: If it's a first course, I'd recommend classical control systems then optimal controls.
Comment: ya, I certainly agree on that.
What I meant was that it depends on how much knowledge of the basics of controls he has already. Non-linear control can be a harder subject, so until one is confident enough in his/her skill, there wouldn't be much help by taking a harder subject earlier.


Is counting maximal cliques in an incomparability graph #P-complete?

Question: This question is motivated by a MathOverflow question by Peng Zhang.  Valiant showed that counting maximal cliques in a general graph is #P-complete, but what if we restrict to incomparability graphs (i.e., we want to count maximal antichains in a finite poset)?  This question seems natural enough that I suspect that it has been considered before, but I have not been able to locate it in the literature.
Answer: According to this abstract for "The Complexity of Counting Cuts and of Computing the Probability that a Graph is Connected" (SIAM J. Comput. 12 (1983), pp. 777-788), counting anti-chains in a partial order is #P-complete. I don't have access to this paper so I can't tell if this result covers maximal anti-chains or not.
Comment: Actually, if you look at the proof, you'll see that #P-completeness is proved for a class of posets in which all maximal antichains have the same cardinality. Namely, start with any bipartite graph $G=(V,E)$ with $n$ vertices and construct a bipartite graph $G'$ with $2n$ vertices by adding $n$ new vertices $\{v' : v\in V\}$ and $n$ new edges $\{(v,v'): v\in V\}$.  Then, if $V_1$ and $V_2$ is a bipartition of the vertex set of $G'$, define a poset on $V_1\cup V_2$ by setting $x<y$ if $x\in V_1$ and $y\in V_2$ and $x$ and $y$ are adjacent in $G'$. So this does answer my question.
Comment: @András: I think that their result is about counting antichains (which are not necessarily maximal).  It might be easy to see that counting maximal antichains is also #P-complete, but I cannot see it.
Comment: @András: The question is about maximal antichains, not maximum-cardinality antichains.  I have not studied the reduction in the paper, so maybe their reduction also proves the #P-completeness of counting maximal antichains at the same time, but at least they are different problems.
Comment: @Tsuyoshi: you are right, the Provan/Ball paper only shows that counting maximum-cardinality antichains is #P-hard.  Back to the drawing board...


Cut a paving slab easily?

Question: How can I easily cut a thick paving slab/flag-stone to the size I need without specialised tools?
The slab is around 2 inches thick, and very heavy.
They are similar to the image below.
Answer: A heavy hammer (3-4 lb head) and a broad cold chisel are the only really sensible way to cut a stone that heavy, short of industrial tools, and I don't know that I'd call them specialized -- but you can buy them cheaply at an import tool store or home improvement "big box".  The only practical alternative is a saw or angle grinder with a carbide or diamond wheel mounted, and this is much noisier and more expensive, not to mention a dry saw produces huge volumes of dust you shouldn't inhale.
To cut, just use the hammer and chisel to score a line a few millimeters deep where you want the cut, then put a rod (shovel handle works) under the cut line, and stand with your feet on either side of the cut line, as far from the line as the stone will allow.  If necessary, have a helper tap near your feet with the hammer, or stike the chisel in the precut groove.  The stone will break pretty cleanly at the scored line, and you can clean up any remaining irregularities easily with the chisel.
Comment: This is how I have cut natural slabs like shale and slate. This is how they did it for thousands of years.
Answer: If the material is too thick for Zeiss' method (which works really well), you can move up to the next level of cutting/breaking rock. You will need an impact hammer, a sledge hammer (or other very heavy headed hammer), and some metal wedges (steel works best).
Using the impact hammer, drill holes along the axis of where you want the rock to break. The depth of the holes will depend on the material you are separating, and other factors, like how much of the rock is covered or buried. After drilling the holes, insert two wedges against the side of the holes. Insert a third wedge between them. Striking the third wedge into the rock will start a crack formation. Repeat in the other hole.
This method should work well for most large garden sized rocks. This method is not good for very small rocks (maybe less than a 1 inch (~2 centimeters) diameter).
Here's a video demonstrating this method.
Wikipedia also has a much more detailed description of the process with pictures.

Plug and feather, also known as plugs and wedges, feather and wedges, wedges and shims, pins and feathers and feather and tare, refers to a technique and a three-piece tool set used to split stone.
Answer: An angle grinder with a cutting wheel works, and is less likely to break the slab than the hammer and chisel method.
Answer: No electrical outlets around?
A star drill along with a cold-steel chisel and hammer will work even if the stone is still in the ground. The star drill works like a chisel but you turn the drill after each blow to create a round hole. After a few pilot holes aligned along the line you wish to split the piece, the chisel between the holes will cleave the stone.
Take your time. Put lemonade into the fridge to cool for when you finish…
and…
WEAR EYE PROTECTION

Cut a paving slab easily?


How often does chanukah start before v'tain tal?

Question: Outside of Israel, we start saying "v'tain tal oomatar livrachah" ("and provide dew and rain for a blessing") in the amida on the evening of December 4th or 5th (depending on the year). Chanukah starts the evening of the 25th of Kislaiv. How often does Chanukah start before we switch to "v'tain tal oomatar livrachah"?
Comment: It feels off topic. I just can't pinpoint why
Comment: The more interesting question is how often chanukkah _ends_ before we start asking for rain in the diaspora.
Comment: Approximately 5 times in the 19 year cycle, the year after when you have two 12 month years in row, or if you prefer year 3, 6, 11, 14 and 17 in the cycle.

Remember the first night of Chanukah might be 3rd December but Shabbat, it might be that we don't start V'Tein Tal Umatar until the night of 5th December that year or even 6th (last happened 2003 but that year Chanukah was still later)
Answer: I have a book here that lists the Hebrew-calendar dates for starting "v'sen tal umatar" for the years 5750 through 5851. Counting, I see that in 26 of those 102 years (25%) Chanuka starts before that date. (And in two of the years they start the same night: 5787 and 5833.)
Comment: In 5660, 5736 (and then 5907 etc.) rain wasn't requested on chanukkah at all
Answer: There can't be a constant ratio for this, as the date of starting v'sein tal umatter changes (on the english calendar) every 3 out of 4 centuries (thus if you look in the Tur you will find a different date than the one in the shulchan aruch, which are both different from what we do).  This is because we follow two different opinions in Maseches Rosh Hashana for how to calculate the exact length of a year, and v'sein tal umattar follows the "less exact" calculation.  Theoretically, in a few thousand years v'sein tal will start very late and never be before chanuka.
Comment: But there can be a ratio for each set of 100/200 years of "constant" dates. Perhaps someone can provide a complete table until the century where the ration is zero.
Comment: @Double AA The question was how often, not how many times.  I was pointing out that "how often" has no answer.  There would be a how often for "how often Rosh Chodesh falls on Shabbos" or something which occurs with regular frequency, or how many times Pesach starts on Shabbos in the 19 year or 247 year cycles.  There is no "how often" for this question though.
Comment: I don't understand your comment. I said "ratio" not "amount".
Comment: I was addressing the question that was asked by the originator of the question.  I was pointing out that there is no pattern, as the two halachos are based on different calculations.  There is only a coincidental "ratio" was all that I was trying to point out.
Comment: The Hebrew calendar does not follow exactly either the Julian or Gregorian calendar but is somewhere in between. Ve Tain Tal U'Matar follows the Julian calendar


What is the difference between HFEC and LFEC inspections?

Question: Sometimes we have to do High Frequency Eddy Current (HFEC) or Low Frequency Eddy Current (LFEC) inspections. My question is: what are the major differences between these two types of inspection? Which one is preferable and more economical? Which type of inspection is required in which cases?
Answer: In general, higher frequency gives better resolution of potential defects but with lower penetration into the material (depth). So HFEC is used to detect surface defects and near-surface defects, but LFEC will be required to detect deeper defects.
From this page on the NDT Resource Center website:

The depth that eddy currents penetrate into a material is affected by the frequency of the excitation current and the electrical conductivity and magnetic permeability of the specimen. The depth of penetration decreases with increasing frequency and increasing conductivity and magnetic permeability. The depth at which eddy current density has decreased to 1/e, or about 37% of the surface density, is called the standard depth of penetration (d). The word 'standard' denotes plane wave electromagnetic field excitation within the test sample (conditions which are rarely achieved in practice). Although eddy currents penetrate deeper than one standard depth of penetration, they decrease rapidly with depth. At two standard depths of penetration (2d), eddy current density has decreased to 1/e squared or 13.5% of the surface density. At three depths (3d), the eddy current density is down to only 5% of the surface density.
  Since the sensitivity of an eddy current inspection depends on the eddy current density at the defect location, it is important to know the strength of the eddy currents at this location. When attempting to locate flaws, a frequency is often selected which places the expected flaw depth within one standard depth of penetration. This helps to assure that the strength of the eddy currents will be sufficient to produce a flaw indication.


Why OWASP Top 10 (web application) hasn't changed since 2013 but Mobile Top 10 is as recent as 2016?

Question: Latest edition of OWASP Top 10 for web application was in 2013 and for mobile applications, it is 2016. Why is it so?
Can we say that the pattern in the web application vulnerabilities is settled? Will same thing happen to mobile based applications?
Answer: The reason for the delay is that there has been little change in the Web T10. As stated by Dave Wichers, the Web T10 project lead, on 30 June 2015:

Historically, we've produced a new OWASP Top 10 every 3 years because
  this seems to balance the tempo of change in the AppSec market, all
  the work everyone does to map their tool/process/other thing to each
  version of the OWASP Top 10, and the effort required to produce it.
  We've been producing a new one every three years since 2004 (i.e.,
  2007/2010/2013), and so a new version for 2016 is due. (Definitely not
  happening in 2015).
However, we've been thinking about what might change in a 2016 release
  of the Top 10 and we don't actually think it would change much, if at
  all, which is kind of sad actually. I suspect some Top 10 items might
  move up or down based on the vulnerability prevalence statistics that
  we would need to gather and process, but I have my doubts that any new
  vulnerability types would break into the Top 10.
As such, given that we don't expect the list to actually change in any
  substantial way, the project has decided to defer the next update to a
  2017 release.

This table from the 2013 T10 Release Notes demonstrates the small change:

The changes were largely due to rethinking how to categorize the raw data, not due to significant changes in the data.
Some have postulated that the level of effort for creating the T10 was a factor for delaying it. While it is a lot of work, I do not think that was a major factor. The Web T10 is OWASP's most recognized project and always has lots of volunteers (I contributed to the 2007, 2010, and 2013 ones).
Speculating as to whether the same thing will happen for mobile applications, I do not think that is likely in the near future. Mobile technology is still in its infancy and subject to rapid change.
Answer: Please note that the OWASP Top 10 was updated in 2017.
I wrote about it at The OWASP Top 10: 2013 vs. 2017.
tldr:
Three new risks were added this year: XML External Entities (XXE), Insecure Deserialization, and Insufficient Logging and Monitoring.
Two items were removed from this year's top 10: Cross-Site Request Forgeries (CSRFs) and Unvalidated Redirects and Forwards.
Two risks from the 2013 report (Insecure Direct Object References and Missing Function Level Access Control) were merged into a single risk: Broken Access Control.
Answer: They don't update it every year and its done by volunteers in their spare time so updates can be slow as it's very comprehensive and takes alot of work. However, they are currently working on updating it this year and are asking for people to submit data towards it.

The OWASP Top 10 project is launching its effort to update the Top 10 again. The current version was released in 2013, so this update is expected to be the 2016 or more likely 2017 release. This time around, we are making an open data call so any organization with a broad set of application vulnerability statistics can contribute their data to the project. To make it easier for the project to consume this contributed data, we are requesting it be provided via a Google form. DEADLINE: Data must be submitted by July 20, 2016.

OWASP TOP 10 site accessed 13th July 2016
The reason the Mobile Top ten is up to date is because it's a new addition compared to the OWASP TOP 10 project which has been running since 2003/2004 when mobile security really wasn't what it is today.
Answer: Why no update?
I'm not sure but, likely there was no need, or too much discussion in the OWASP community to be able to update the web top 10 list from 2013. Also, the mobile world is evolving rapidly last years, probably that's why different vulnerabilities and needs are required and so the (mobile) security industry had to develop faster along with the mobile industry developments.
History of OWASP top 10
The first OWASP (web) top 10 list was published in 2003 and in 2004 a new list followed. Then in 2007, 2010 and 2013 new lists were released.
In 2013 the first Mobile Top 10 was created and became final in 2014. As far as I know in 2015 only a new mobile top ten analysis was done but didn't result in a final list. Now the Mobile Top 10 2016 that you referred to, is currently a release candidate document.
Developments
The Open Web Application Security Project (OWASP) is actually working on a OWASP top 10 2016 currently. Suggestions can still be submitted till July 20, 2016. Source: owasp.org.


What is the difference between a managed and unmanaged switch?

Question: I've seen some documentation discussing the use of an unmanaged switch. What is the difference in functionality/performance/etc. between an unmanaged and managed switch?
Answer: Unmanaged switches — These switches have no configuration interface or options. They are plug-and-play. They are typically the least expensive switches, found in home, SOHO, or small businesses. They can be desktop or rack mounted.
Managed switches — These switches have one or more ways, or interfaces, to modify the operation of the switch. Common management methods include: a serial console or Command Line Interface accessed via telnet or Secure Shell; an embedded Simple Network Management Protocol SNMP agent allowing management from a remote console or management station; a web interface for management from a web browser. Examples of configuration changes that one can do from a managed switch include: enable features such as Spanning Tree Protocol; set port speed; create or modify VLANs, etc.
Two sub-classes of managed switches are marketed today:
Smart (or intelligent) switches — These are managed switches with a limited set of management features. Likewise "web-managed" switches are switches which fall in a market niche between unmanaged and managed. For a price much lower than a fully managed switch they provide a web interface (and usually no CLI access) and allow configuration of basic settings, such as VLANs, port-speed and duplex.[10]
Enterprise Managed (or fully managed) switches - These have a full set of management features, including Command Line Interface, SNMP agent, and web interface. They may have additional features to manipulate configurations, such as the ability to display, modify, backup and restore configurations. Compared with smart switches, enterprise switches have more features that can be customized or optimized, and are generally more expensive than "smart" switches. Enterprise switches are typically found in networks with larger number of switches and connections, where centralized management is a significant savings in administrative time and effort. A Stackable switch is a version of enterprise-managed switch.
Source: http://en.wikipedia.org/wiki/Network_switch
I would explain in more personal detail, but the wiki explains it pretty well.
Answer: Most managed switches offer you features like:

View the bridging table to see which MAC addresses are associated with a given port
View error statistics for each port
View packet transmit / receive statistics for each port
Set duplex / speed negotiation (or lack thereof) on a per-port basis
View power-over-Ethernet status and current draw for each port (if applicable)

Typically there is a TELNET, serial, and / or web-based interface to interact with the switch.
Many managed switches allow you to poll the device with the SNMP protocol to use the information described above in graphs, alerts, etc. (Beware-- some low end managed switches, like the Dell 27xx series, don't have SNMP functionality!)
Most managed switches today support things like 802.1D spanning tree, 802.1q VLANs, and 802.3ad link aggregation, and the management interface allows you to configure these various features. You can typically setup port VLAN memberships, link aggregation groups, and control spanning tree parameters all from a web or command-line interface.
A goodly number of managed switches have taken to emulating the Cisco command-line interface (HP ProCurve, Dell PowerConnect to name a couple) such that someone with Cisco-specific knowledge can easily configure those switches.
Answer: If you are debating whether it is worth it to upgrading to managed switches, here are some criteria:

Security. Do you need the ability to
switch on and off ports, match ports
with MAC addresses, and set up VLANS?
Performance. Do you need to monitor
and shape traffic of individual ports
or switches? Do your clients have
real-time performance needs (SLA's or
metrics that you must meet)? Do you
have VOIP set up and want better QoS
features on the local network?
Management. Would you like the
ability to be able to easily see
network performance across various
clients? Have extra assistance with
troubleshooting connectivity or other
issues? Integrate your switches into
your SNMP management tool for log
file correlation?
Random Features. Do you have the need
for link aggregation or the other
random features offered only by
managed switches?
Answer: One additional thing: Most managed switches allow some form of port binding (so that you can use multiple NICs in a device to effectively multiply the bandwidth to the switch. Also, VLAN support is often not found on unmanaged switches, but are common on managed ones.
Answer: Unmanaged switches have a set behavior that works from the time they're powered on until they're powered off.
Managed switches normally have settings that can be modified remotely. This might include turning ports on or off, managing port speeds, throttling, segmenting and more.
Comment: (unmanaged switches)... or until they break.
Answer: Unmanaged switches are basic plug-and-play switches with no remote configuration, management, or monitoring options, although many can be locally monitored and configured via LED indicators and DIP switches. These inexpensive switches are typically used in small networks or to add temporary workgroups to larger networks.
Managed switches support Simple Network Management Protocol (SNMP) via embedded agents and have a command line interface (CLI) that can be accessed via serial console, Telnet, and Secure Shell. These switches can often be configured and managed as groups. More recent managed switches may also support a Web interface for management through a Web browser.
Comment: This question has already been answered many times. Your answer does not provide extra value.


Force SSL on parts of my Joomla site

Question: In Joomla 2.5 and/or 3, is it possible to enable SSL on certain pages? I am aware of the "Force SSL" option in global configuration, but I have a site with an e-store, and I would like to redirect user to the secure connection when they enter the checkout process. How can I do that?
Answer: The best way I know how is with the Yireo SSL Plugin. I don't think you can force PARTS of your store, but you can force the whole component. You might also want to check to see if your store has an SSL switch (most do).
https://www.yireo.com/software/joomla-extensions/ssl-redirect
Comment: Hi guys, I'm the creator of SSLRedirect, and I though I would drop a note on this: SSLRedirect is able to force SSL upon any page - instead of configuring components or Menu-Items, you can also configure custom URLs and even use regular expressions.
Comment: Is that a newer feature? I recall in the past that I think I could exclude article IDs or something, but couldn't specific certain pages by url. Sounds like it might have been upgraded since I last messed with it.
Answer: I second Brian Peat's suggestion of using the Yireo SSL Plugin, but as an alternative you can also achieve this using the .htaccess file (depending on how complex your URL structure is and how many pages you want to redirect).
<code>RewriteCond %{HTTPS} =off
RewriteRule ^checkout$ https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]
</code>
This will redirect your users to a secure connection if they visit http://yoursite.com/checkout.
Are there any particular reason why you only want SSL on parts of the site? It might be a security issue if sensitive information is sent through a non-secure (HTTP) connection, and then redirected to HTTPS. In that case it's already to late and and the information might have been picked up by someone.
Update:
I just noticed that any menu item can be forced to display using SSL:
Answer: Both Above answers using the plugin or .htaccess file are valid.(I like the .htaccess myself, more universal) The comment about the Joomla Menu Manager Metadata property may give people a false sense of security: While it does indeed make the LINK go to https, it doesn't force it if you visit the page with regular "http" allowing the data to be sent unencrypted. With security data, I would not relay on the metadata Secure menu if the data really needs to be secure.

Force SSL on parts of my Joomla site


Story about a woman cursed to be cold all the time

Question: I am trying to find this short story I read in high school. I believe it was written by Isaac Asimov since I was writing a paper on him at the time I read it. The only thing I can remember about the story is that there was a woman who was married. And something happened to her, a curse of some sort, that made her feel cold all the time. Eventually her husband's warmth is no longer enough for her so she begins to search for a warmth that will. And she keeps going through guy after guy moving on once their warmth isn't enough anymore. If any one knows this story I would love to find it again.
Comment: I can't say I've read all of Asimov's fiction - that would be more or less impossible - but this doesn't sound like any Asimov story that I can recall, nor does the summary sound like an Asimov plot.
Comment: Unfortunately, none of us know when you were in high school. Was it last year? 50 years ago? Did you read this as part of an anthology, or was it published separately?
Comment: @JonKiparsky - Asimov did edit several SciFi anthologies (and there's a SciFi magazine with his name on it) so perhaps that's the cause of the confusion?
Comment: Could you please give us more details about the book? Try to put a summary in the title to attract more experts to your question.
Comment: @SystemDown I think you're probably right.
Answer: "Baby, It's Cold Outside" by Isaac Asimov.
http://www.asimovreviews.net/Stories/Story011.html
Copied from the above link...

A cold, calculating woman who married for money only and to whom cash alone has worth is transformed by Azazel into someone who desperately
craves the warmth of a male body—any body.

Part of the Azazel series.  Main character has a small demon (Azazel) which helps him solve other people's problems, but never in the way he wants or expects.
The lady in question mentions that she had tried other men (losing count at 15-17), but none brought her the warmth that her husband did.


Tank armaments: railguns vs coilguns

Question: Assuming power can be provided, what would be the more practical primary armament for a tank using an electromagnetic cannon? I am looking for a good compromise between accuracy, cost and durability of the cannon. Assume that high temperature superconductors are common place in this universe.
Comment: Have you done any research into the difference between the two and why the military is pursing Railguns over Coilguns? Coilguns run into issues past a certain size, and it isn't a very large size either.
Comment: It might also be worth it to look at hybrid designs which use rails for one part of the acceleration track and coils for another. This might make sense if one technology is better at low speeds while the other is better at high speeds.
Answer: Coilguns (assuming current technology)
Ironically, rail guns have arguably received more attention for development in military applications.  Unfortunately, however, there have been some major setbacks.  The Navy is documented of having been developing rail guns as weapons as far back as 2005, yet as of 2018 there have been some hugely limiting problems:

There are a number of things the Navy still doesn't know how to do. How is it possible to shoot more than about three or four rounds out of an EM rail gun before having to change the barrel? How is it possible to build the kind of pulse forming networks that are needed to be able to shoot not direct fire weapons, but 200 mile indirect fire weapons? There is a lot of potential that a capability like EM rail gun could bring. But there are many risk to EM rail gun.
...
Railguns face two types of problems : engineering problems, and physics problems. Engineering problems, such as the size of pulse power units, are engineering problems that can be resolved with suitable applications of time and money. Physics problems, such as barrel life, are rather less amen able to such brute force solutions, and are the reason that not everything that can be described can be built, or built in a useful form.

Wikipedia summarizes the challenges of rail guns (emphasis mine):

The heat generated from the propulsion of the object is enough to erode the rails rapidly. Under high-use conditions, current railguns would require frequent replacement of the rails, or to use a heat-resistant material that would be conductive enough to produce the same effect. At this time it is generally acknowledged that it will take major breakthroughs in materials science and related disciplines to produce high-powered railguns capable of firing more than a few shots from a single set of rails. The barrel must withstand these conditions for up to several rounds per minute for thousands of shots without failure or significant degradation. These parameters are well beyond the state of the art in materials science.

This really only leaves coilguns - mostly for their capacity for fire regularly.  Some important items of note:

Although coilguns typically have lower velocities than rail guns, tanks don't need to fire at the same distance/velocity as the Navy needed in the first link above
The biggest issue with coilguns is timing, but the issues with timing in coilguns dates from WWII on to the 1980s, which is now much easier to deal with via computers.
NASA has many uses for coilguns, and is actively pursuing it's usage

In conclusion, although the railgun has arguably received more attention, there are some strong material limitations with it's usage in war.  Coilguns, on the other hand, are limited mostly by timing and design issues, which are much easier to deal with today, and therefore make coilguns more practical for tank cannons (assuming current technology).
Answer: Railguns.  Because you are writing awesome fiction, not working for DARPA.
Coilguns have a limited upside for awesomeness.  At the end of the day they are glorified doorbells.  Yes they are more practical.  So is commuting with your Prius as opposed to your jetpack.  If you are trying to shoot things in real life, work on the coil guns and you may be on the wrong website.
Railguns can be made into sweet near future scifi with nonmagical real physics-based schemes.  You know that because already are thinking along those lines with your high temp superconductors.
https://www.halfbakery.com/idea/Superconducting_20railgun_20projectile#1137552946
Using a superconductor for projectile or rails sidesteps much of the current issues with ohmic heating and rail ablation.
Another idea I had for railguns was more plasma.
https://www.halfbakery.com/idea/Plasma_20Rail_20Railgun#1186761424
Plasma armatures are used on some railgun projectiles - the armature is behind the projectile and gets turned to plasma when the electricity comes on.  The plasma then conducts the electricity, closing the loop that provides propulsive force.  Leaving the projectile out of this means more options for projectile composition.  Why not do that with the rails too?  Regenerate your plasma rails after each shot!  In my scheme, graphite is used.  I like graphite also because if the condensing graphite plasma were not vented appropriately, once they were in a real fight your tank crew would soon look like chimney sweeps.

Tank armaments: railguns vs coilguns


Using Google Analytics, how can I find the 10 pages with the biggest traffic changes in the last 30 days?

Question: I am looking to find top 10 posts which has gain traffic, lost traffic etc.
Comment: See this post https://plus.google.com/+avinash/posts/GKSmS4NaarS
Answer: If by top 10 posts you refer to most visited pages, once you have opened the view for your website under the Reporting tab:

Set the date range (in the upper right corner) to Last 30 days
Go to Behavior > Site Content > All pages to get a breakdown of the most popular pages by default metrics.
To filter out only blog posts, go to the search bar (just bellow the graph on the right side) and type /blog or /blog-post or the part of the URL category that your site uses for blog posts.

Hope this helps.
Comment: This is useful information, but it sounds like they want to see changes in traffic (gain and loss) rather than most popular pages.
Comment: Exactly, which pages has gain traffic over 30 days and which have lost, so that one can find out what is working and what is not. Anyway thanks for information.
Comment: Thanks Stephen, I have missed that part. OK then, after taking the above mentioned steps, I would nclick the "Comparison" data view (located just on the right of the search box, 4th icon) and compare Pageviews or Unique Pageviews with the site average to get a sense of the performance of the pages/posts. Another option is to go back to the first step and compare the last 30 days with the previous 30 days, then go through the same steps to get a better view of the performance of the pages.


How much data warrants building a pipeline?

Question: If I'm doing simple aggregation dashboards, what's the minimum amount of data which justifies building a full blown data processing pipeline? Is it reasonable to build a complicated pipeline with Mysql -> Hadoop -> Redshift and then analytics and visualizations on top of redshift if my database only has about 10million transactions per month. Would it be better to just run something like ReDash visualizations on top of my unaggregated data in MySql?
Answer: You should only complicate it as much as necessary to meet your requirements.

What kind of aggregations are you doing? Most DBs can handle basic counts pretty easily. 10 million in a month sounds like something a large MySQL instance could handle.
How quickly does everything have to update? If the users only expect the summarized data to be updated monthly, you have a lot of time. If you have to update it more often, it might make sense to have MySQL collecting it but Redshift presenting it. Redshift's analytical focus and columnar storage means you may not need pre-aggregated data until your volume gets much higher than what would require aggregation in MySQL. I was using a 4 node Redshift cluster with the smallest instance types and it could do a count across >300 million rows in 17 seconds.

Can you not build aggregate tables in MySQL? What is making you want to put Hadoop in between MySQL and Redshift?
Comment: I want to use Hadoop because:
- I can do cleanup and some normalization of data there (e.g. mapping geo coordinates to cities)
- I want the analytics to be updated daily and I want the visualizations to load fast, on unaggreated data they dashboard would become very slow
- This pipeline would be future proof, It will allow us to do more complicated stuff in the future
- Sounds much cooler than running plain queires on mysql tbh :P
Comment: Daily updates in a regular RDBMS is not bad unless you are always recalculating all your history.


How could low-gravity dust in the early solar system have formed hard stones?

Question: I wonder how very low-gravity dust could make bind together and make hard and dense stones that later on will merge together and make some of the planets? I read some meteorites as hard as a hard stone are remnants of the early phase of solar system's formation. If this is the case, it shows that they are formed using their own gravity attracting other dust; however, I thought making such a hard stone will require a high pressure.
Comment: Does this answer your question? [How do rocky objects between 1cm and 1m accrete to form planetesimals?](https://astronomy.stackexchange.com/questions/46783/how-do-rocky-objects-between-1cm-and-1m-accrete-to-form-planetesimals)
Comment: Actually keeping this question is helpful, since if someone asks some question like this, the search engines will route her here. The other one is a specific question and not a general one.
Comment: These are different questions and have different answers, not a duplicate, voting to leave open.
Answer: The process you are referring to is called pebble accretion, which is very complex and not particularly well understood.
The initial premise of your question, that dust particles stick together via their own gravity, is not quite correct. As you say, gravitational interactions between individual particles are incredibly weak. Rather, dust particles grow via collisions within a protoplanetary disk. During this early stage of star/planet formation, gas and dust are spread out in a huge disk in which the material orbits the newly forming star at the centre. Particles collide and stick to each other via electrostatic forces. Growth continues all the way through from dust particles, to much larger planetary building blocks called planetesimals. In this sense, meteorites are indeed remnants of the early Solar System. Sometimes you will hear them refer to as 'failed planets', in that they failed to accrete enough material to grow to planetary size.
There are still a lot of open questions relating to this process. For example, once particles reach sizes greater than about a meter, collisions result in fragmentation rather than growth. This has led to the development of newer theories, such as streaming instability, which are able to better explain rapid growth.
Recommended further reading...

Raymond & Morbidelli (2020)  - Planet Formation: Key Mechanisms and Global Models
The Exoplanet Handbook (chapter 10) - Michael Perryman
Comment: There was a really nice experiment on the ISS recently that demonstrated how strong and important electrostatic effects are on accreting small particles together. Sorry I can't find a better link https://skyandtelescope.org/astronomy-news/building-planets-in-plastic-bags/
Comment: This is not quite the answer to what OP is asking: "Stones" i.e.rocks of the size of a fist or smaller (down to mm-sized Chondrules) cannot be formed via pebble accretion. The latter is the process of accreting small rocks (such as Chondrules) onto a parent seed body of lunar to mars mass in order to form larger planetary cores.
How those pebbles form in the first place, i.e. how they are concentrated and melted, is not answered here.


G24Q CFL Line Voltage

Question: I am working with a CFL that requires a ballast to fire the lamp. This lamp is a G24Q-2. The lamp has four pins on the base. I am assuming that two of the pins are for the ballast connection and the other two are for constant line voltage. Is there a way to tell which pins are for which connection?
Answer: No sirree.  Nothing like that.
You may be familiar with ancient inductive ballasts where preheater 1, a starter, preheater 2 and an inductive ballast were all in series with line.  (and of course once the lamp strikes, it shorts out the starter and preheats, so now it's just the ballast and lamp in series, and the inductor limits current).  Those things predate this modern type of bulb.
Today, you will have electronic ballasts which intake 120V and output 4 wires to go to the bulb.  They do their magic electronic woo-woo inside the box, and synthesize high frequency (flicker-free) AC, doing a sequenced preheat start if needed for assured start in the cold.  These make sense because the silicon needed for the magic is cheaper than the mass of copper needed for a magnetic ballast.
Especially awesome are programmed start ballasts, which preheat the bulb exactly as much as it needs for a reliable strike at any temp, and very easy on the bulb.  That's the one to use for hard-to-change bulbs, or bulbs on motion sensors.
It's possible some very cheap lamp builder has found a way to wire those old-school, but I would not retain that design.  I would retrofit one of the electronic ballasts. In which case you wire it according to the wiring diagram on its labeling or instructions.

G24Q CFL Line Voltage


Report for users with and without Activities shows Record Count (1) for users without Activities

Question: I created a report that shows Users with Activities from this week. It groups records by Full Name and for Users with Activities, it shows a correct number of records. For Users without Activities, it shows record count (1) instead of (0). Is it possible to fix it? The report is created from custom report type (Users with or without related records from Activities (Assigned To)) without any customizations except date range.
Answer: It's because your custom report type basically says "with or without" the child record. So the parent records are always shown, whether or not they have child records.
I haven't tried this, but I think you might be able to filter out users without activity by the blank Subject column.