sensor to detect rope position, as it nears the end of the line retreval

Question: I have built a winch for a 4wd, to race with. I would like suggestions on a sensor to detect rope position as it nears the end of the line retrieval. Not at the drum end, as that may vary. Something along the lines of a short piece of trace wire, inserted inside the winch cable, a few meters from the hook end, to turn a light on as it passed by a sensor? Is there something like this? Application would be in water and dirt, 12v power supply. Thank you for any help.
Great feed back, thanks. see the winch here.https://www.youtube.com/watch?v=vgx1hc5GikU
FYI I want some kind of warning system, for when the hook is attached to the front of the truck, and we are winding the loose rope back onto the drum, and you cannot see how near the rope is to stopping as it pulls tight.
Comment: Is the rope metal or polymer?
Comment: Encoder added to the winch reel?
Comment: thanks for suggestions everyone. Encoder on the drum can't work in this case as the rope may not spool evenly, which increase the amount recovered per revolution
Rope is poly, dynema. I think about six strands spun together - easy to get to the core of.
Answer: There are several types of sensor you could try.
Tie a knot in the rope. Put a lever operated microswitch next to the rope inlet on the winch.
Wind some iron wire round the rope (assuming it's not steel rope). Perhaps use a sleeve of heatshrink over the top to hold it in place. Then arrange a magnetic circuit with a permanent magnet and a linear Hall effect sensor, such that the output of the sensor changes as the iron changes the reluctance of the magnet path. Use an opamp or comparator to sense the change in Hall output.
Wind some copper wire round the rope, and solder the start to the end to make a shorted turn (assuming it's not a steel rope, but with care it might even be got to work on steel). Use a high frequency oscillator and a search coil close to the rope, to sense the shorted turn. Sense either a drop in level of the search coil, or coupling to another coil.
For both of these schemes, sensitivity and rejection of false triggers will be improved by using a pair of sensors side by side, sharing the same exciter in the middle, and sensing them differentially. Common mode interference and drift will be rejected as the sensors are differential. As the rope comes in, first the outboard sensor will react, then the inboard. Look for this sequential signature.
I assume that reflective sensors would quickly be blinded by mud.
Comment: I can't tie a knot in the rope, as the rope needs to be smooth to run through the fairleads, and reluctant to change the thickness, for the same reason. Thank you for your other suggestions, I will research them, so that I can ask, some more detail, once I know what I'm talking about.
Answer: Implementation will depend on type and size of rope.
a sophisticated way would be to add a sleeve to the outside or a(n enlarged) core to the inside to increase the diameter of the rope by say 20%.  This should not impact massively on the rope flexibility and may even help to prevent tangles by stiffening it a bit. If strength is not the limiting factor replacing part of the inner core and making the rope thinner may be possible but could compromise the rope safety ratings, might work with some types of woven fibre ropes I expect.
You would then have a second pair of slot rollers behind those that feed the rope onto the drum spring loaded firmly and they will indicate the altered thickness
of rope has entered the winch.
If the rope is conductive and sleeved with an insulating tube or braid it may be possible to detect the change in surface conductivity but in mud and such not altogether reliable.
If the rope is non conductive a braided wire sleeve may be electrically detected.
If the rope is non metallic or a non-magnetic stainless steel a ferrous braiding or core could be magnetically detected.
EDIT:
*An inductive metal detector (stud/pipe/conduit finder) should be able to pick up a thinnish ferrous core wire.
Magnetic inserts may be an option (get a bunch of small magnets and insert them into short lengths (say 1 inch/25mm) of tubing and then insert a bunch of these into a heat-shrink tube of the length you want to have your detected end (say 80 inches/2m). This will let you pick up the end of the rope as it passes a magnetometer (3 axis compass sensor might be the best) by generating a field anomaly as each magnet passes.  Stronger magnets are better but too strong and they will pick up bits of scrap iron, rust and magnetite.  The two layers of plastic should protect the rope structure from too much damage from the magnets.  Rubber magnetic sheet (fridge magnet sheet) cut into a ribbon might work but is much weaker and will need more sensitive detection.  Placing a string of magnets with coded North-South arrangement at regular intervals (every 2m) could theoretically let your system know which point is passing through along the whole length of the cable.*
Comment: The rope is non metallic, the braided wire sleeve is along the lines of what I was hoping for, but I need the out side of the rope to be as smooth as possible
A magnet sensor, will only detect as the magnet passes close by?. I would like (ideally) a signal from the sensor, as the rope covered 1 - 2 meters, to be easily visible.
Can a simple wire be magnetised 2m long? Don't the N and S poles need to be close together for a magnetic sensor to work?
Comment: Stainless steel braid is available from auto accessories suppliers if held in place with heatshrink and hot-glue (either full length or at each end) it should prove reasonably durable.  another option is to splice it (or some wire) it into the twist of the rope.
Answer: The simplest idea I can think of would be to put a small, powerful magnet in the rope. As in open up the strands with a blunt screwdriver, place the magnet, and let the strands close again. They will tighten back up when you put tension on it.
Next, a few Hall sensors along the fairlead. A single one won't work as every winch I've ever had or seen has either a roller fairlead or at least a slot so the cable can be angled side to side or up and down. So you need to make sure the magnet never gets out of range.
Once that's done, the rest of the problem is simply reading the sensors. However, I can't see what problem you're solving. Although it was a long time ago, I have a lot of experience with off-roading and needing winches. I can't think of a single time (except the few times I was alone) that I was retrieving the winch cable and there wasn't someone on the outside of the truck keeping a light tension on it to feed the cable properly and tell me when I was getting close.
Comment: Thanks Lyndon, That's kinda what I'm thinking, though I don't come from this back ground. To answer your last question first. The winch is very fast (think 40kmh - 11m/s), a standard fast winch will only retrieve line at 0.4m/s. We wish to hook the line to the truck, then complete the line retrieval while the passenger gets back into the truck. The sensor is to give the driver a chance to slow the winch down before it pulls up tight against where the winch hook is secured to on the truck. The rope is contained in a pipe fairlead, so it is always in the same location (+/- 25mm)
Comment: The winch is mounted in the rear of the truck and the rope is duct-ed to the front. Would one small magnet quickly passing by the sensor be enough to trigger it?
Comment: http://i292.photobucket.com/albums/mm1/Craig_Fraser/rope%20guide%20arrow_zpsbm7754td.jpg
Answer: if you go the magnet/hall sensor I would go for smaller multiple ones distributed along a length of a meter or so. This allows a certain number of 'dropouts'. also multiple hall sensors along the pipe for the same reason. I think anything within the rope may potentially weaken it if the hard object is pulled over the fairlead under tension or possibly just the tension while winching will squeeze the strands of rope over the magnets.
because you dont need to know the length I would steer away from trying to measure anything but if you were I would have a pinch roller/wheel setup, the error in any spooling compared to 11m/s wind in probably will not matter, your light would trigger at 30m so give 2 seconds for winchman to react and slow the winch in time. With the harsh environment you are operating in I would also go as simple as possible and this solution would involve some electronics, probably arduino(https://forum.arduino.cc/index.php?topic=366220.0) and then you could also have an estimated length display.
Have you though of a simple mechanical solution? http://www.trulineaustralia.com.au/item-details.asp?CategoryID=71&ItemID=201
You would need to make some kind of "remote" wire or shaft linkage
Micro rfid chips/reader would to overkill.


Custom Named Entity Recognition using deep learning

Question: I have a dataset with two columns. First column has some text (news article) and the second column contains names of people (not exactly English names) present in those news articles (first column). I've tried to build a custom named entity recognizer using Spacy but it isn't working. Can I use deep learning approach to identify the names in unseen news articles ? (Test data)
Answer: The CNN and RNN are quite popular for custom NER. I will suggest you try to implement CNN first and then RNN. Also, when I did custom NER, I found out that for my dataset stacking is giving really good results. I used Random Forest, XGBoost and Linear Regression.
Answer: Named Entity Recognition (NER) is about identifying the position of the NEs in a text. This means that each instance must represent a particular position in a text, and the NER will predict whether this position corresponds to a NE or not. Currently your data is not formatted in this way so it's not surprising that it doesn't work: in a vector representation of the whole text the model cannot find the kind of indication it needs to identify NEs.
Comment: Yes, but is there any deep Learning aprroach like sequential modeling ?
Comment: I don't know about recent DL approaches, hopefully somebody else will give you an answer. The only approach I know with DL is hybrid: train a RNN on the sequences, then use the resulting features in a CRF model (CRF is the traditional approach for sequence labeling like NER).
Answer: I suggest you to take a look at the performance of mainstream taggers first. Namely: spacy, nltk, stanfordnlp. Check how good they are on finding the right set of names on your Test set.
Alternatively, you must make your own tagger. Any NER tagger is fundamentally a classifier with RNN or CNN layers that process input text. The output, Dense layer has as many nodes as classes avilable.
Another option is to download some pretrained model. For example, Huggingface's transformers library lets you download lots of Transformer-based architectures (like BERT), that you can then fine tune for your specific task.
However, building your own model is a lot of work. If you find that mainstream classifiers do a pretty good job, and you don't have too much time, then go with those tools. Good luck!


Stuttering problems

Question: I am a college student with stuttering problems. My first language is Spanish and my second language is English. I came to the U.S four years ago. I didn't stutter that much back then on my first days in the U.S, but as English became my first language, the problem worsened more and more. Now today, I can't even say a sentence in English without stuttering and I avoid talking to my teachers, partners,colleagues etc. I don't even go to office hours because of that fear. I use mathstack  exchange as a way out to avoid going to office hours. Any advice?. Right now, speech pathologists haven't made any significant progress in finding the cure for stuttering, so what can I do in the meantime?. I have never tried taking medications because that would be the perfect inducer for doing drugs and other things that go against my ethics, but is taking medication worthwhile?.
Answer: As a speech-language pathologist, I will say you should still see an SLP. While there is no "cure" for stuttering, an SLP can work on specific strategies tailored to you. Go to the American Speech-Language Hearing Association's (ASHA) website to find a professional near you. Many universities also have speech and hearing clinics where their graduate students work under the supervision of licensed professionals at low or no cost to people who go to the clinic.
Regarding medication: there are no medications approved to "treat stuttering." Many people who stutter also have co-existing anxiety disorders and could benefit from consultation with their physician on these matters. Beware, though, of any physician who prescribes a medication to help with stuttering.

Stuttering problems


how to customized user login page

Question: My question is when i  browse  my admin site www.example.com/user a simple login page will appear.

Here in this login form there is no option for forget password .so I need option to request new password and new password can be send through email.
Comment: which theme you are using ?
Comment: i am using my own custom theme
Answer: You can make a template to alter your user login form.
In template.php:
function YOURTHEMENAME_theme(){
    return array(
        'user_login' => array(
            'arguments' => array('form' => NULL),
            'render element' => 'form',
            'template' => 'templates/user-login-form',
        ),
  );
}

Then create user-login-form.tpl.php in your template folder and print the login form using
print drupal_render_children($form);

Don't forget to clear cache
Answer: Customizing the user login, register, and password reset pages is fairly simple, and uses the following concepts:
preprocessing to set variables
registration of functions in the theme registry
creation of one or more theme templates.

Step 1.
In the site theme directory, create or edit your template.php file.
Step 2.
The first step is to implement hook_theme for your theme. In the template.php file for your theme, look for a function named yourtheme_theme() and modify it to add these return values. If the function doesn't exist, add the following:
For D6:

 array(
      'template' => 'user-login',
      'arguments' => array('form' => NULL),
    ),
    'user_register' => array(
      'template' => 'user-register',
      'arguments' => array('form' => NULL),
    ),
    'user_pass' => array(
      'template' => 'user-pass',
      'arguments' => array('form' => NULL),
    ),
  );
}
?>

Notes about that code:
Change the function name by replacing "yourtheme" with the name of your theme
The template can be the same for all three. The example above uses a different template for each case: user-login, user-register, and user-pass
The template names must use a dash, not an underscore
Note: It's user_pass not user_password

For D7:

 'form',
    'path' => drupal_get_path('theme', 'yourtheme') . '/templates',
    'template' => 'user-login',
    'preprocess functions' => array(
       'yourtheme_preprocess_user_login'
    ),
  );
  $items['user_register_form'] = array(
    'render element' => 'form',
    'path' => drupal_get_path('theme', 'yourtheme') . '/templates',
    'template' => 'user-register-form',
    'preprocess functions' => array(
      'yourtheme_preprocess_user_register_form'
    ),
  );
  $items['user_pass'] = array(
    'render element' => 'form',
    'path' => drupal_get_path('theme', 'yourtheme') . '/templates',
    'template' => 'user-pass',
    'preprocess functions' => array(
      'yourtheme_preprocess_user_pass'
    ),
  );
  return $items;
}
?>

Notes about the D7 version:
The 'path' lines tell Drupal where to find the .tpl.php files. This is optional, and in the code above, 'path' tells Drupal to find the files in the templates subdirectory of the theme's base directory.
Note the "_form" added to the user_register element.
Note: As it is the case for D6, it's user_pass not user_password

Step 3.
Now you implement three preprocess functions. There may be more concise ways to code this, but this works very well and is easy to read, so here we go!
For D6:
Notes about that code:
Change the function name by replacing "yourtheme" with the name of your theme
The line $variables['intro_text'] adds the text that follows to the $variables array, which gets passed to the template as $intro_text
The second line renders the form and adds that code to the $variables array, which gets passed to the template as $rendered

For D7:
The code is even simpler for D7 because we don't need to pass a variable containing the form content we want rendered. The variable exists already in the $vars array and can be rendered in the .tpl.php file.
The above preprocess functions simply add a variable into the $vars array that is then displayed in the .tpl.php file. Much more complex manipulation of the content of the render array is possible.
Please note, that the preprocess functions should go into the template.php file.
Step 4.
Create template files to match the 'template' values defined above.
For D6
We need the following template files (make sure to use a dash, not an underscore) :
user-login.tpl.php
user-register.tpl.php
user-pass.tpl.php

For D7
As for D6 but with user-register-form.tpl.php for the register form.
Step 5.
Paste the following into user-login.tpl.php. Modify as necessary for user-register.tpl.php (D6) and user-register-form.tpl.php (D7):
For D6:

For D7:

Add the forgot password link, HTML Tags, Css & JS.
Note the change to the syntax for causing Drupal to render the form. Also, the D7 sample uses a different class for the div, but that's just a matter of preference.
Step 6.
Save your template.php file to the theme's main directory. Save your .tpl.php files in the same place for the D6 examples, or, in the case of the D7 examples, to the directory you specify in the 'path' element of the $items array.
Step 7.
Rebuild the cache. Go to Administration > Performance and click on "Rebuild Cache" on the bottom of the page.
Now, the user login page will contain the new text from the preprocess function, and the tpl.php file(s) can be modified to suit the site's needs.

how to customized user login page


Does a memoir need to include a reliable narrator?

Question: After reading a memoir excerpt about a drug addict, who was jealous of his peer, I began wondering if the author is intending to be unreliable. The memoir's account was practically as drunk as the author in the original context. That seems fitting considering it was a memoir that included drug addiction. Is it important for the narrator to be more ethical and self aware at the later time? His account of his peer was misrepresentative and unethically vexatious, but the overall personal journey was well described. Should the author recant the views formed in his earlier state?
Comment: I seem to remember a case of a recent memoir that ended up being revealed as being heavily fictionalized after it was published that ended up being withdrawn from shelves after this was revealed. I don't remember the title or exact details though.
Answer: A memoir does not need to have a consistent reliable narrator.
First off, what is a memoir, and how does it differ from a historical novel and how does it differ from a textbook?
Dictionary.com defines the word thusly:

a record of events written by a person having intimate knowledge of them and based on personal observation.
Usually memoirs.
  a. an account of one's personal life and experiences; autobiography.
  b. the published record of the proceedings of a group or organization, as of a learned society.
a biography or biographical sketch.

A memoir is written from personal observations. A historical novel is fiction set in a historic context; a textbook is a collection of facts. A memoir is neither of those.
A memoir, in my view, is supposed to give you an accurate feel of what the experience was like. To give you a glimpse of what it would be like if you had been there. To show what the author was going through, and how they felt.
Whether or not the author's perception of things was factual - given that it was influenced by the effects of drugs - is irrelevant. What matters is that it accurately portrays what the experience was like for the author.
Ultimately, in a memoir, the actual facts and what actually happened is less useful than how the author perceived it at the time. Because how the author perceived it at the time is the only way that we can, first of all, get an accurate feel of what the situation was like from their perspective; and second, it helps to understand actions taken by understanding what the author was thinking.
So, no: a memoir does not always need to have a perfectly reliable narrator, because that's not the point of a memoir.
Comment: Not sure if Dictionary.com is a good source to use here ... I seem to recall a more literature-specific encyclopedia of terminology, used by Gareth in some of his answers, but I don't remember now what it was called.
Answer: Memoirs are by definition subjective, so they definitely can have an air of self-awareness associated with them.  Three that come to mind are Benjamin Franklin's Autobiography, Frederick Exley's Notes from a Fan and William Borroughs' Junkie. In Franklin, the feeling is more like a Horatio Alger dime novel that a real life.  He seems more intent on showing the correct method of developing his moral life than chronicling the actual events.  I'm not sure how much he expected the reader to see this.
Exley explicitly subtitled his novel as "A Fictional Memoir". He freely embellished his own life in an attempt to give the feeling of what his life was like and to give better narrative cohesion.
Burroughs has a distanced view of his life and feels like a comment on it as well.
Once you accept Exley's "fictional memoir" stance you can start thinking of autobiographical fiction that often has a strong self-awareness associated with it.  I think of examples such as A Portrait of an Artist as a Young Man, or Ellison's Invisible Man.


Autofocus not working on Canon 20D

Question: i have a Canon 20D and i cannot get the autofocus to function correctly. Whenever i try to autofocus the lens will go to the closest focus and stay there. If i press the shutter button again it will move slightly and stop in the same place. How can i fix this issue?
Comment: yes. Also, the lenses I've used on it work fully on multiple other bodies.
Comment: Does this happen with more than one lens?
Comment: Did it just start happening suddenly?
Answer:
How can i fix this issue?

You probably can't. But here are a few things you can try:

Clean the electronic contacts on the camera that connect to the electronic contacts on your lenses
Reset the camera to factory default settings.
Remove the battery and leave it out for several hours or even a couple of days. Also remove the button cell backup battery that preserves the time/date and selected settings when the battery is removed. Don't forget to reset the time and date when you replace the backup battery and the main battery and power the camera back up.

Beyond that there's not much you can do if you've already confirmed that all the lenses work fine on other EOS bodies and none of them work on the 20D. Sending it in for servicing isn't practical since any evaluation, much less a repair, will cost more than the camera is worth. So at that point it's probably time to start thinking about a replacement camera body.
Comment: Long shot, but could there be an issue with the shutter button? And if so, is back button focus a work around?
Comment: That depends on whether the camera properly meters on a shutter half-press or not. If metering is working as expected that eliminates the shutter button as the source of the issue. This really sounds like a major hardware issue with the PDAF system.

Autofocus not working on Canon 20D


How can I tell which release my org is running?

Question: Usually you can tell what release (e.g. Winter '14) you are running under by looking at the logo in the top left, but if that has been customized or removed it's not an option. Is there some place in the setup or settings that let's you know what release you are running?
Answer: On the Home tab, on the top right of the screen is a link to Discover Winter '14. This indicates your release.
Comment: Well! I didn't find this in Lightning interface. Is there any similar way to check it in Lightning..
Answer: Or if you like to see it in xml, goto /services/data/ on your instance.
https://[instance].salesforce.com/services/data/
works with a lightning url too.
https://[domain].lightning.force.com/services/data
Answer: You can see in more detail what release and patch level your instance is on in the Releases section of the known issues page.
For example this page, which lists fixes for Summer 14, https://success.salesforce.com/issues_releases_view?release=190000000, also shows the patch level of each instance - at the time of writing "Spring '14 Patch 20.2". This can be useful if you see discrepancies in behaviour between orgs on different instances.
Answer: You could go to setup Build | Develop | Apex Classes and click "new".
This will let you see what the options for API version are, API 29 = Winter 14.
I'm sure there's a nicer way to do it though!
Comment: Drawback is that this is not available in enterprise production environments
Comment: You can create Visualforce Page
Answer: The /speedtest.jsp page that is available in each instance includes a Release section that includes the current patch release. This can be useful if you don't immediately know which pod your instance is currently running on.

In 2016 Trust was updated to include a REST API - See What's New in Trust.
Of particular interest is the new REST API.
With that we can do a single unauthenticated GET call and parse the exact releaseVersion from the JSON response.
E.g.
https://api.status.salesforce.com/v1/instances/na5/status

Extract from the JSON response showing Winter '17 Patch 13.5
{
  "key": "NA5",
  "location": "NA",
  "environment": "production",
  "releaseVersion": "Winter '17 Patch 13.5",
  "status": "OK",
  //...
}

You can also use https://api.status.salesforce.com/v1/instances/status/preview to see the releaseVersion of all the public pods.
Comment: The speedtest page would be ideal except that it apparently doesn't report the release for partial sandboxes.
Answer: In lightning experience, the option to view the current release (from the UI) is at the top right corner of the screen, help and training (question mark icon):

However, as of recent releases, this is no longer included, and you have to sleect the release notes in order to easily view what version you are supposed to be on.

Loading screens will also give you a hint as to what version you are on:
Comment: Unfortunately that doesn't show what patch version my sandbox is running.
Comment: Salesofrce changed/removed it from the menu options. Other than the loading screen, you will have to refer to other answers,
Answer: Option 1:
1.Login Your Org --> SetUp --> Company Information -->Instance --> Take the value of this
2.Open the link --> trust.salesforce.com --> status.salesforce.com --> status button click --> search with above instance --> After it finds the instance result --> click on the link --> Right side it show the Instance Details.
**Option 2 :**Simple, Refresh the screen it shows the logo and image of release version, Sometimes it will be very fast cant see the details.


What's a free web hosting service to show temporary beta versions of my Drupal websites online?

Question: What's a free web hosting service to show temporary beta versions of my Drupal websites online ?
Answer: You can serve em from your house and just use a service like dyndns to resolve a hostname to your IP address at home.  This is what I usually do myself.
To top it off, dd-wrt, tomato and some of the other router firmwares out there support these dynamic dns services and will automatically update your account for you regularly to make sure your IP address is set in their service to what it should be.
Comment: I don't know if I can, in good conscience, give a +1 to an answer that suggests hosting from home. We see people almost every day on Server Fault and Super User who are trying, unsucesfully, to do this.
Comment: Farseeker it is pretty trivial to setup a temporary home hosting solution.  Forward port 80 to a Lan IP address running a web server and create an account on one of the many dynamic IP address domain services.  Especially considered self employed developers usually have a web environment setup and ready to go.
Answer: Try DreamHost
Answer: I personally use WAMP since its so quick to setup. From there you could go many different directions. I have an account with http://www.dyndns.com to redirect to my home IP. I also use named based virtual hosting which is easy to setup if you take the time then I can use something like this for my clients http://projectname.something.getmyip.com which will redirect them to their project on my server.
If you want to try this, I can give you some pointers to setup the WAMP instance..
If you'd rather host it elsewhere, any major site is probably as good as any other. You could go with godaddy, 1and1.com, etc... and get a cheap shared account for a couple bucks a month.


What are the challenging benchmarks for self driving cars object detection beside Kitti

Question: I am working on 3D object detection in the context of self driving cars and I was wondering if there are other challenging benchmarks for this beside Kitti.
Answer: You may find Apolloscape dataset interesting. It was recently released by Baidu. From the article describing the dataset:

In this paper, we present a large-scale open dataset,
  ApolloScape, that
  consists of RGB videos and corresponding dense 3D point
  clouds.

Apart from the article,
there have been some blog posts with summarized information on the dataset.


Does Zinc become black & dull after reacting with dil. HCl?

Question: In the reaction where $\ce{Zn}$ reacts with $\ce{HCl}$ to give off Hydrogen gas & Zinc Chloride solution, does the zinc turn a dull black color after a while? If so, why?
Comment: Could you provide a little context? Are you asking because you tried this or saw it done and the zinc turned black? Are you trying to find a way to make zinc turn black?
Comment: Under which conditions does it happen? Only when you dip a zinc sheet into hydrochloric acid or also when you hold the sheet above to only react it with the hydrogen chloride in the vapour phase?
Answer: Look at it under a microscope.  If the surface is microporous, light goes into the reflecting cavities, bounces around, and is absorbed before it can escape.  Wilkinson Sword sold bolted stacks of double-edged razor blades as low power laser beam dumps,  Each sharp edge was mirror bright with a slight taper toward the edge.  Light bounced in and could not escape.  The sharp sides of the stack were astoundingly black.  375 blades x .004" = 1.5" square target.
Or, you have impure zinc and crud is accumulating at the dissolving surface.  Alloy 8111 aluminum foil contains about 2% or so of strengthening dispersed intermetallics.  Dissolving aluminum foil in acid or base leaves black residues.
Answer: The $\ce{Zn}$ cation polarises the $\ce{Cl}$ anions to a good extent and reduces the energy gap between certain energy levels. Therefore the electrons in $\ce{ZnCl2}$ are able to jump this gap by absorbing certain radiation, when this radiation is absorbed all the radiations except these are reflected and can be seen as complimentary color which in this case happens to be black.
Answer: It doesn't become pitch black, but it does become dull gray/dark gray. The reason is that even if metal surface is mirror bright, it is usually composed of multiple crystals with slightly different composition and orientations. Because of this differences, different faces of the microcrystals are etched with different speed, forming a complicated surface shape.
For the same reason, fine metal powders usually have dark coloration.
Answer: I've been doing this as art for a while and when I let the muriatic acid dry over night on the zinc it not only turns perfectly black but becomes  amazingly hard to sand down or buff back for aesthetic purposes.The image not only illustrates the deeper darker parts but near the center of the image is a dark area that is dark and not deep and I used a muriatic wash to try to get it off. It even resisted that. So my thought was that it was some type of zinc oxide that had occurred and was harder than the zinc.
Curious about everything .
Charlie W.


If a father's first wife dies and he remarries, is the first wife considered a step-mother?

Question: If a father's first wife dies (with or without children) and he remarries and had kids, is the first wife considered a (deceased) step-mother to the new wife's children, or simply "dad's 1st wife"?
Answer: No, the first wife would not be considered a stepmother to the second wife's children.  The "step" relationship occurs where a person "steps into" the position of the holder of a normal natural relationship, taking over that role.
A second wife can "step into" the role of mother to a first wife's children, becoming a stepmother, but the first wife, being dead, cannot step into the role of mother to the second wife's children.  The dead wife never had a relationship with the later children, and there is no common term for her indirect relationships with them.
Answer: If you accept the etymology that step-child in Old English was related to the word ástíeped meaning bereaved, then the children of the second wife have not lost a parent and so are not anyone's step-child.
Any attempt to create a family relationship between a dead person and ones not yet born who have no genetic (so-called "blood") connection seems to involve a serious problem in logic.
Answer: I would say the a step-parent is generally defined as a partner (generally married to, but more recently co-habiting) with the official parent.
If one or both of the official parents were previously married but had no children together, they would simply be the previous husband/wife of mum/dad.


What process manages disk storage in Windows?

Question: Which Windows process is responsible for determining the low level space management and allocation?
For example, that the data goes to this block, this segment etc.
Answer: There doesn't seem to be a dedicated file system management process, so I'm pretty sure it's being managed by the Kernel, so it would be the either the "System" process or something hidden managed by the System process. As the file system needs to be managed before the first service boots up, it should be deep in the systems core. (but them again, I don't know the MS source code)
Dedicated Filesystem Management processes would be those for defragmentation.
Answer: I would guess it's the driver ntfs.sys.
Comment: That's the best "very short answer". :) Of course it could be fastfat.sys for a FAT32 partition. If you want to cover more bases, you can say "it's the file system driver, e.g. ntfs.sys or fastfat.sys".
Comment: This is a better answer than the answer that simply says "It's the Kernel".
Answer: Any 'process' can access the disks via the Windows API if they have permission.
Where the data ends up on the disk (blocks, segments etc.) is determined by the mass storage drivers (which are (usually) kernel-level) and by the drives themselves.
Answer: It's a series of layers - at least two.
Blocks within each volume (e.g. C:) are managed by the file system driver. (In fact, a good definition of "volume" is "one instance of file system metadata". Each volume defines one and only one root directory \.)
Volume(s) within a physical disk are managed by a partition driver and a volume driver. The volume driver for dynamic disks also implements RAID-1, RAID-5, or RAID-0, i.e. a volume that encompasses several disks.
These drivers are not part of the kernel, though they run in kernel mode.
File system drivers do run some threads in the "System" process, but not everything in a file system driver runs there - some of it (as much as possible) runs in the context of the requesting thread. In none of the above cases are there separate entire processes devoted to managing the blocks within a volume.
With things like Storage Spaces, iSCSI, etc., there are a few more layers. Near the top, though, it is the same: A file system driver that works within the ranges of blocks defined by a volume driver. Again there are no processes dedicated to block management.


Acer new leaves in mid-September

Question: We had very bad hailstorm in late July which broke a number of branches off the Acer and left a layer of ice on the pot for 3 hours or more. The Acer leaves have slowly shrivelled as a reaction to the ice and damage, but the leaves didn't initially drop off. We are now in mid September and the leaves are starting to fall as new buds are forming and seem to be pushing them off (they are the biggest and reddest buds this Acer has ever had!). A few of the buds have opened and new bright red young leaves are brightening up what looked a very sorry tree. Most of the buds opening are on or close to where the wood was broken. Question: what will now happen to the buds that have formed, the majority look as though they will not open this year, but will they remain dormant and then open next spring or will the tree have a barren 2017?
Comment: Welcome! This question has excellent detail, which is what gets you the best answers around here, so thanks for that. Would you also please add where you live, and a picture if you have one? Just press the gray "edit" word under your question, or use this [edit], and add it in. Thanks. We hope you enjoy the site!
Answer: No, those leaves will all drop off.  That is the beauty of being a deciduous tree!  Leaves are the most vulnerable, roots a step up but buried in the ground (not a pot) protects them and then the stem/branches that have a thick epidermis and dormancy that slows the vascular system down to a crawl.  Dormancy means the plant is done making its own food for the season.  Your trees have stored enough food to maintain minimal necessary functions during dormancy and getting rid of the leaves is a protective mechanism.  This is why deciduous plants are so hardy.  Conifers have leaves far more hardy than deciduous trees but even a few of the conifers have learned to shed their leaves ie.) the Tamarack or Larch.
Environmental triggers such as day/light hours, heat, cold, storms, rain can confuse plants. Some people would go so far to say this tree is 'telling the future' for weather such as we will be having an 'Indian Summer' a long, warm beautiful fall.  I don't buy the woo-wwooooo stuff.  As the climate changes globally (and I am NOT talking about this anthropomorphic global warming crap) this is how plants adapt and their genome changes to ensure survival.

Acer new leaves in mid-September


C# Anonymous function-scope

Question: var foo = "bar";

new Func<String>(() =>
{
    var foo = ""; // This can't be done in C#. Why is that?

    /* In JavaScript, this is perfectly valid, since this scope (the anonymous
       function) is disconnected from the outer scope, and any variable declared
       within this scope will not affect variables in the outer scope */

})()

Answer: Actually, even in javascript it isn't entirely disconnected; javascript allows lexical closures - so without the var, the old value of foo should still be available.
The difference is that javascript chooses to allow you to re-declare the name with a different meaning (in the inner scope). C# chooses not to.
I find the C# version less easy to get confused about! In particular when code (further down in the method) expects to be talking about the "old" variable, and suddenly it starts looking at the "new" one.
Answer: C# captures local variables inside the anonymous function.  This is actually a very powerful feature that JavaScript also supports but in a slightly different way.
This concept is what computer scientists call a closure.  By capturing local variables they can become part of the state of the function itself thus giving you more flexibility.
Answer: Since the code refers to both symbols as "locals", the compiler cannot discover which you are referring to simply by going up the scope chain (local -> member -> type).
FYI, anonymous methods are compiled as classes and are assigned (as properties) any
members/locals they access as fields.

C# Anonymous function-scope


Simple Oauth oauth/debug?_format=json Internal Server error

Question: When i try to test the ooauth/debug?_format=json endpoint through Postman i get the internal server error and error code 403 forbidden.
Even though i use a valid Authorization header with Bearer and the access token for a certain user. The endpoint works fine for anonymous user.
So i guess it's a permission error or the token expires even though i've set a big expiration date for testing purposes.
Has anyone encountered the same issue as me? If yes did you manage to solve it? I follow the tutorial step by step from the official simple_oauth module page in drupal. Thanks in advance for reading this.
Answer: I fixed this issue by going to admin/people/permissions and selecting all of the Simple OAuth permissions for Authenticated User. I'm sure a more refined approach to selecting permissions will be possible, but initially selecting all of them has fixed this issue for me.


Does the Unearthed Arcana Scout get the PHB or UA Ranger's Natural Explorer?

Question: The Unearthed Arcana Scout archetype for Fighters gains Natural Explorer at 3rd level. It is written as the PHB Ranger feature. Can a Scout now use the UA Revised Ranger's Natural Explorer feature instead?
Comment: @DaleM This question was originally asked as an [answer to another question](http://rpg.stackexchange.com/a/91776/4563), which provides some context missing here.
Comment: Welcome to the site, check out our [tour] about asking good questions. Yours has a few problems: what game is this? What edition? If it is, as I think D&D 5e then there is something wrong because the Unearthed Arcana fighter does not have a Scout archetype.
Answer: Unearthed Arcarna are all unofficial rules and only usable by the agreement of the players at each particular table, particularly the DM.

You can think of the material presented in this series as similar to the first wave of the fifth edition playtest. These game mechanics are in draft form, usable in your campaign but not fully tempered by playtests and design iterations. They are highly volatile and might be unstable; if you use them, be ready to rule on any issues that come up. They're written in pencil, not ink.
http://dnd.wizards.com/articles/unearthed-arcana/unearthed-arcana-eberron

In the case where an unofficial rule1 cites an official rule2 which is then superseded by another unofficial rule3 then if you are going to use the first unofficial rule1 then you need to consider as a table what the implications are of changing to the second unofficial rule3 and make your decision.

1 - Unearthed Arcana "Kits of Old", Fighter Archetype: Scout incorporates the Ranger class feature Natural Explorer.
2 - Ranger class feature as published in the PHB.
3 - Ranger class feature as published in Unearthed Arcana "Revised Ranger".
Comment: @EnchantedHobbit not quite... Mearls says in the UA intro that *if* this Ranger version makes it into a future published work then both it and the original (PHB) ranger would both be AL-legal. But it's not AL-legal now. (Nor would it even be if Mearls had said in UA that it was, because AL rules are PHB+1, and AL makes AL rules, not Mearls.)
Comment: Not debating, just clearing up a misconception about UA. Your first comment might convey to readers that UA Ranger is AL-legal, when it's not. The "both" that Mearls is talking about are the PHB ranger and the "revised ranger in future D&D sourcebook." Even if that weren't the case, ALPG, not UA, controls AL. You can often find me in [chat] if you think I'm reading it wrong--with 20 rep (now) you're able to post there.
Comment: @DaleM since OP expressed confusion at your post, I tried to make it a little clearer *what* you were talking about without losing the overarching message I think you were getting at: *you're the ones deciding which rules to use, figure it out yourselves.* As always, I hope you think this improves your already-correct answer.
Comment: Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/50194/discussion-between-nitsua60-and-enchanted-hobbit).
Answer: Putting aside the fact that both the Scout archetype from UA Kits of Old and the UA Revised Ranger are not "legal" classes in the normal sense, you cannot swap one class' features with another class' features, even if they have the same names, unless your DM has allowed it.
The Scout archetype was clearly written using the PHB Ranger's Natural Explorer feature in mind, given that it was written before the Ranger, Revised article:

Natural Explorer
  At 3rd level,  you gain    the ranger  class   feature of the  same    name,   with    the following   alteration: You choose  additional  favored terrain types   at  7th and  15th   level.

In addition, the UA Revised Ranger's Natural Explorer feature does not include a Favored Terrain option at all, and based on the description of the feature on the Scout archetype it seems clear the Scout is focused on the survival and terrain exploration features of the PHB ranger, not the martial aspects of that class.
If your DM (or you, if you're the DM) has decided that some or all of the Unearthed Arcana character options are allowed, you still cannot swap the Scout archetype's Natural Explorer feature with the Revised Ranger's Natural Explorer feature, because class features for each class are unique to that class and only that class, and the Scout was written with balance against the PHB's ranger in mind.
The UA Revised Ranger is a new class.  It does not update the Ranger in the PHB, nor does it update any other class.  The features defined in the UA Ranger article only apply to the UA Ranger.  You could play either the original PHB Ranger or the new UA Ranger, but not swap features between them--at that point you're making a new, custom class.
The same could be said about using the UA Ranger's Natural Explorer feature with the UA Scout archetype; you're no longer using the Scout as written (because it was intended to use the PHB ranger's Natural Explorer Feature) but instead are making some custom homebrew class, which could upset the balance of the Scout archetype in comparison to the PHB Ranger or even other PHB Fighter archetypes.
That being said, as Dale has pointed out in his answer, you're already well beyond official rules territory here, so it really is up to you and your DM and the rest of your group how you intend to proceed.


Classification report and confusion matrix problem

Question: I am working on sign language recognition system using HOG and KNN. I have 26 classes of 180 images per class. The dataset was split into 1/3(67%) for tanning and 2/3(33%) testing after feature extraction with HOG. Model achieved recognition accuracy of 95% on testing dataset. But I am not understating the confusion matrix and classification generated. I believed 1/3 (33%) of each class should be 60 images for testing per class. But result the confusion matrix and classification report generated are shared below. Very confusing report. Kindly help. I can see TP of 65 more than class images.
Comment: is it a multiclass problem or at least you mistakenly approached it that way? i.e. is it possible that an image belongs to more than one class? It might be the mistake. you need to share your code
Comment: It is a multiclass problem, some images have great similarities though. Could that be the reason? If yes, way out of the problem, please. @KasraManshaei
Comment: Sorry I meant multilabel. if one image has two labels then the support of that sample will be 2. so the total support is due to number of labels and not samples. it means you may have 65 "labels to classify" instead of 60 which is number of samples. the rest i can tell u only if you provide a sample code
Comment: I just checked all my classes. Each class is 180 images. I spilt the whole dataset using test data split @KasraManshaei
Answer: This looks completely normal to me: your dataset has 26x180=4680 instances, so the test set should have 4680x0.33=1544.4 instances. According to the classification report it contains 1545 instances, which is consistent with this calculation.
It's important to understand that by default the dataset is split between training and test set randomly across all the instances, without taking their class into account. This means that by chance some of the classes can have a bit more or a bit less than 33% instances in the test set. This is what can be observed in the classification report and it's not a problem.
Sometimes this can be an issue when there are classes which have very few instances in total. In this case one should use stratified sampling in order to apply the proportion to each class independently.
Comment: Thanks, I find your response useful. However, this problem can be solved by manually separate testing dataset from training dataset. Thanks is zillion time @Erwan


Copyright of a product

Question: If I were to take a picture of an item I own, lets say a backpack. And were to photograph it for product photo website portfolio. Are there any chances for legal repercussions for using this product? There are no visible tags or brand indicators. Thanks for your answers in advance!
Answer: When creating a photograph of a 3-dimensional object, you are not at risk for violating the copyrights that rest on that object. This is primarily, because you are not creating an actual copy of the object, but merely a 2-dimensional representation of it.
Having the photograph of a backpack does not give you an item with the identical function of a backpack and therefore it can't be a copy.
However, there are other Intellectual Property rights that you need to take into account. The most important ones are Trademarks and Industrial Design Rights.
If an object has a very distinctive design (that is more than utilitarian), then it is likely to be protected by Industrial Design Rights, which means that you are not free to reproduce the design of the product, not even in a completely different medium, such as a photograph.
This, for example, holds also for buildings designed as a one-off by an architect, where you can´t just take/publish pictures of the building without permission from the architect (unless it is more of an overview shot with the building in its surroundings).
Answer: IANAL* - this is an engineer's opinion.
If the product is not readily discernible as being of a particular brand you MAY be OK.
In most cases I'd expect that there would be no problems. You asked however re "any chances", and I'd expect there may  be a small chance of problems in two possible areas.
There may be some attribute that very clearly brands the product for some people but which is inobvious to you.
Two possible instances where this could cause problems are

If you tried to use the image in a context where the branded product was different to a brand being promoted
If the brand owner objected to the way the image was used.

*I am not a lawyer - you knew that.
Answer: You can look at the policies of stock and micro stock houses here as a guide. In general for products or companies, any visible identifying logo makes the image unusable for stock. (with people, you need a model release for commercial work).
So it's fairly safe to take a picture of something if its not identifiable to a brand or a specific item.
Usage also matters here, there's more leeway if it's for personal or editorial use and a lot less if it's for commercial (advertising or sales).
Comment: The restriction on logos in stock photos is probably more related to advertising policies than copyright.

Copyright of a product


I've read that Sorrel is a permaculture green, but an anual, how does it come back?

Question: How does sorrel come back every year if you pick it all, when people say it's an annual?
Answer: Some things are annuals in some places (usually colder) and perennials in other places. And some people say things that are not strictly true. Tomatoes are perennials - in the tropics, or in a heated greenhouse. But we treat them as annuals in the colder regions, normally.
I find "French sorrel" to be an unreliable perennial in my garden - I will get a few survivors, but they don't all survive. French tarragon is similar, though actually better at surviving in general for me.
A seed company describes it as a perennial, but also says zone 6-10, so not surprising that it expires in zone 4/5 many times. Much permaculture literature is from balmy climes, I have noticed.
Some are annuals that reliably self-seed.
Wood sorrel is one of those, and has largely taken over the "sorrel" role for me as a result. I don't use a huge amount of it and have so far not been noticeably impacted by its oxalic acid content (which regular French sorrel has as well, I note the seed company claimed theirs had been bred for "low oxalic acid content" though I don't know what the relative amounts might be.
Comment: I've generally seen French sorrel listed as hardy to zone 4 or even 3. I'm in 4b, and my plant is at least 5 years old. I do not let it reseed.
Comment: Mine has typically all died out within 3 years - could be factors other than cold, of course. I'm a throughly imperfect gardener.
Comment: So which one should I choose from the seed catalog from 4A?
Comment: My Green De Belleville sorrel has survived one winter excellently, so far, and is thriving this year. The first year, it was pretty small. It's in clay in partial shade, though. This year it had lots of big leaves. I'm in southwestern Idaho. We had a warm winter, but the record low is about -25° F. Either way, though, I plan to grow it from saved seed for several generations to help it acclimatize, and allow for more cultivation. I got mine from Baker Creek.


Is there any experimental work being done on terraforming?

Question: Beyond theory, are any organizations doing experimental work on Mars terraforming? In laboratory environments.
Comment: I think this is an excellent question. We have over fifty questions tagged `terraforming` but they are mostly hypothetical. Instead of the usual "Could we do X?" you are asking if there are any experimental investigations (of course on a small scale) that people have actually done. I am sure people will find things. There is plenty of work on growing plants in all kinds of simulant soils and unusual atmospheric and environmental conditions.
Comment: I suppose geoengineering would be an aspect certainly, but I'm curious as to whether anyone has actually begun to actually create the sort of 'bio- dome' one sees in every fictional representation of a terra formed Mars. Also, if there's any attempts to either create plants capable of surviving in extreme climates as ELw38fr and his students did, but with more advanced genetic modification or hybrid technology. I imagine some protection would
Comment: Did you mean [Geoengineering](https://en.wikipedia.org/wiki/Geoengineering)?
Comment: Earth climate observation and modeling may satisfy your requirement of "Laboratory environment," Earth being the laboratory. For example, we tracked the sulphur dioxide and particulates output from the Mt. Pinatubo eruption, their distribution through the next few years, and subsequent observed meteorological changes. We use satellites, balloons and sounding rockets to sense or sample C02, Methane, ozone, chemicals, aerosols, and particulates in multiple layers of our atmosphere and incorporate that data into our climate models. That knowledge forms the basis for many terraforming schemes.
Answer: What do you mean "beyond research" ? Such studies are done in laboratories, or they are just games. You have a few "societies", such as the Mars Society, where people try to advance in such studies. Farming is a good subject, quite an easy one, lost cost, still important, and can eventualy not require huge instrumentation. Therefore, it has focussed some attention and still keeps going on.
At a less serious level, last year, I proposed such an experiment to young students (14-15) that were interested to do some experiments. They proceeded at one, about resistance to an important daily variation of temperature. On Mars the difference between night and day is about 70 to 80°C. We did a few "studies" between sub-0° at night and about 25 to 30°C at day, starting with different type of seeds, and chosing a comparative approach with witnesses. No major discovery ;-) Apart a cute intro for these young student to science reasoning :-).
Answer: At least one research group has conducted a chemical "experiment" simulating a possible greenhouse effect on Mars:
The data received by the Mars rovers suggests that Martian soil might be extremely acidic. If that was true at a large scale, then melting Mars' frozen water resources might be enough to cause both global warming and an increase of atmospheric pressure: if you put water on acidic minerals, greenhouse gases are released.
You can see the "experiment" at the time of the linked video:

I put "experiment" in quotes because this is very elementary. But this is, in my opinion, rather in favor of this concept of terraforming than against it. (in contrast to some of the far-fetched theories)
If you watch the whole thing, you can also see other plausible ideas and practical research. Though none of it looks as fancy as "domes" or involves genetically Mars-tailored organisms.
This is by far not a comprehensive summary on everything that's going on, but you only asked if there are "any" organizations doing such work.
Comment: Suggesting a link to a video would be a helpful comment, but not a Stack Exchange answer. Can you explain *in your answer* at least a few of the points in your video *that you feel answer the question as asked?* Otherwise this is a link-only answer.
Comment: Thank you. I too am not too sure its a good idea but I need the info for research.
Comment: The main problem with mars terraforming is it's gravity, and lack of magnetosphere. Even if you can give mars a thicker atmosphere, it won't be a permanent feature, it may last a long time on human scales but eventually most of it will be lost to space.
Comment: @ArtisticPhoenix This is not the one single solution to the problem of making Mars less hostile, just as this right here is not the place to discuss such details. The question is about what's currently being practically studied.
Comment: I was stuck on physics SE. Your questions and answers are good. Try some of the other SE sites like Engineering or Robotics.
Answer: Yes, we are doing it now.  It's called climate change.
By pumping the atmosphere full of ancient carbon we are terraforming the earth.
For those climate change deniers...
http://www.realclimate.org/index.php/archives/2004/12/how-do-we-know-that-recent-cosub2sub-increases-are-due-to-human-activities-updated/

CO2 produced from burning fossil fuels or burning forests has quite a different isotopic composition from CO2 in the atmosphere. This is because plants have a preference for the lighter isotopes (12C vs. 13C); thus they have lower 13C/12C ratios. Since fossil fuels are ultimately derived from ancient plants, plants and fossil fuels all have roughly the same 13C/12C ratio – about 2% lower than that of the atmosphere. As CO2 from these materials is released into, and mixes with, the atmosphere, the average 13C/12C ratio of the atmosphere decreases.

This can actually have a noticeable effect on carbon dating as well.
The Suess effect
https://en.wikipedia.org/wiki/Suess_effect
So in short, we are already experimenting with "terraforming" on our own planet.

Fossil fuels such as coal and oil are made primarily of plant material that was deposited millions of years ago. This period of time equates to thousands of half-lives of 14C, so essentially all of the 14C in fossil fuels has decayed.[5] Fossil fuels also are depleted in 13C relative to the atmosphere, because they were originally formed from living organisms. Therefore, the carbon from fossil fuels that is returned to the atmosphere through combustion is depleted in both 13C and 14C compared to atmospheric carbon dioxide.
Comment: Now all we need is a "control", a second Earth that we don't screw up, just for comparison ;-)
Comment: Voting down, as this does not even attempt to answer the question. OP asks about experimental work in the context of Mars terraforming. There no such thing as "terraforming of Earth", because that would make as much sense as sweetening the sugar, making aquatic solution of water, or trying to taste your own tongue -- that is, no sense whatsoever. It is quite clear that you completely rejected the intended frame of this question just to get a cheap excuse for engaging in irrelevant ramblings about supposedly human-induced climate change. Not helpful, innovative, nor entertaining.


Use of the xyY color space?

Question: What's the use of the xyY colorspace in games? I'm not sure what's the advantage of using it in shader programming or elsewhere.
Comment: [xyY is derived from CIE 1931's XYZ space](http://en.wikipedia.org/wiki/CIE_1931_color_space#CIE_xy_chromaticity_diagram_and_the_CIE_xyY_color_space).
Comment: I never heard of xyY color space, it either has an alternative name, or there is sth wrong, either way can you  provide a link where you read about it?
Comment: Did you mean xyZ?  https://en.wikipedia.org/wiki/CIE_1931_color_space
Comment: I'm not really sure this is on-topic, though, since there's no particular reason this color space is more compelling or useful for games than it is any other application.
Comment: According to further research xyY seems to seperate Luminescence from Chrominance.
Comment: xyY is used in this course http://blog.selfshadow.com/publications/s2012-shading-course/mcauley/s2012_pbs_farcry3_notes_v2.pdf.
Answer: The main reasons people use the xyY color space are:

It cleanly separates luminance (brightness) and chromaticity (color content)
The chromaticity part (xy) has the same range, namely [0, 1], no matter how bright or dim the color is
All physically realizable colors lie within [0, 1] in xy.  (The Y component is unbounded.)
You can convert an arbitrary reflectance spectrum to XYZ (and thence to xyY) by integrating the products of the spectrum with the color matching functions.

xyY is useful for investigating color gamuts, such as the gamut of human vision (the famous CIE horseshoe diagram), or the gamuts of various color spaces (e.g. sRGB versus Adobe RGB), where we care about chromaticity but not brightness.
However, there are some reasons why xyY is not a very good space in which to do image processing:

It's nonlinear.  This means you can't easily do physically correct lighting calculations, such as adding together the contributions of multiple lights, in this space.
Not every point in the xy [0, 1] square actually represents a color.  Points outside the horseshoe are invalid.  That makes it annoying to do any kind of image operation on xyY space, as you have to ensure you don't generate invalid colors.
It's not very perceptually uniform either, so you can't easily measure perceptual distances between colors (e.g. for perceptual error estimation, or selecting complementary sets of colors, etc.)  CIELAB space is better suited for this.

In short, I can't think of a reason to ever use xyY in games or shader programming.  If the goal is to separate luminance and chromaticity, YCoCg is probably a better choice; it's linear (if you transform to it from linear RGB) and is cheaper to transform to and from than xyY.
Comment: What about tone mapping?
Comment: @Fire Maybe.  If you're trying to do chrominance-preserving tone mapping, CIELAB might be better; I'm not sure.  If you're trying to do filmic tone mapping, you do it in RGB (since films have separate R, G, and B pigments).

Use of the xyY color space?


What should a moderator do if a user posts content on a site that is well-meaning, but unfriendly in content?

Question: A user posts questions and/or answers that are well-meaning, but unfriendly in content. Their posts get a lot of upvotes as well as a few flags. What should moderators do?
Comment: Your post title says "content on a site", but the body of the post refers specifically to questions and answers. Are you intending to ask specifically about Q&A sites, or any site in general? :P
Comment: @V2Blast Thanks for the edits! I think this is a broad question about the problem in general.
Answer: As a past moderator on a forum full of debates, I had faced this case a lot of time.
As a moderator, the good reaction is, according to me:
- If the post is a question:
Edit the question with more "gap fillers" and all the needed friendly text. Put it clear that it had been added to the bulk of the question, but that the bulk is not changed, unless words in this bulk are clearly rude.
It is important to edit and add those polite gap-fillers since otherwise, there won't be answers to this question.
- If the post is an answer:
For example if the user posted: "Your question is stupid, don't you understad/know X or Y"?
Then you should post an answer close to this answer, which formulate differently what the user said in his answer. And have a direct message to the user saying: "Your answer is well meaning but you are to rude/unfriendly, please consider new formulations etc..."
If there are truly rude or too familiar words in the answer, then edit the answer to delete those words. Otherwise don't, it's up to the user to change his answer.
Answer: A site should have clear policies so everyone knows what is appropriate and what isn't. In any case, you must follow your own policies. And it is helpful to continually consider and revise those policies when you notice they are not supporting the goals of your site.
With that said, the appropriate response (or policy revision) would depend on what you mean by "negativity". If you mean the user is giving well intentioned advice in a mean-spirited (or racist or sexist, etc) way, I think you discourage the mean spiritedness with warnings and/or bans if necessary.
On the other hand, if by "negativity" you mean that the user is stating facts and opinions without sugar coating, I think you should be pleased that your site is generating that kind of honest discussion. You can't please all the people all the time, so you are going to have to choose between pushing away those giving blunt advice or pushing away those that don't like hearing it.
You may also have to decide whether those flagging the post are potentially traumatized and needing protection from a well-meaning post that is actually harmful. Or if they are simply sheltered people, unable to handle legitimate facts and opinions that contradict their beliefs.
In any case, your choices need to depend on your goals... If your site generates revenue from people who prefer the sugar-coating, you might need to discourage honest and open commentary. If it is about advancing public knowledge, you are going to have to accept and encourage discussion that some will find offensive.
And if your main goal is increased user count, then regardless of the above you will want to avoid discouraging the person generating a lot of upvotes along with a few flags... That at least, is a simple numerical calculation.
Good luck.


Sport's APIs For Headshots and Stats

Question: I'm currently building an program that would benefit from higher quality images of University's Logos(NCAA, NAIA, etc.),head shots of athletes, and general statistical data(Games played, etc). The information needs to be quite accurate. I was looking into ESPN's API and it seems they no longer do public keys or are accepting new strategic partnerships. Is there anything else of that quality that is trustworthy?
Comment: Anything here? https://opendata.stackexchange.com/a/9822/1511
Comment: @philshem nothing there sadly. I'd really like to not scrap espn website for their headshots but it may come down to that.
Answer: For soccer players, Kaggle hosts the FIFA 18 Complete Player Dataset. Accessing the data requires registration.

17k+ players, 70+ attributes extracted from the latest edition of FIFA

Including a URL to each player's photo is in the CSV:

Example URL: https://cdn.sofifa.org/1x/18/players/20801.png

Note on player photo URL: needs to be slightly modified, based on my testing and this comment.

I replaced the /48/ with /1x/ on my local copy to get all of the photos to work.

https://cdn.sofifa.org/1x/18/players/237419.png
Note on original data source:

The data is scraped from the website https://sofifa.com by extracting the Player personal data and Player Ids and then the playing and style statistics.

Sport's APIs For Headshots and Stats


Is it appropriate to email a professor with a simpler solution than the one she provided?

Question: I am in a graduate math program in the US, and the professor is teaching via online lectures. The proof she provideed for one of the theorems is a little bit tricky to understand. I think I found a proof that, though is about the same length, I think is much simpler. Could it be considered inappropriate to email the professor out of the blue and give her the proof?
Comment: There was significant debate here about an edit which has since been reverted; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/115131/discussion-on-question-by-blue-is-it-appropriate-to-email-a-professor-with-a-sim).
Comment: _I think I found a proof that...is about the same length_ Perhaps you'll reduce it with time.
Answer: Email the professor, explain that you came up with an alternate proof, and ask if it is correct.
If you approach it this way, it should be perfectly acceptable to anyone.  You get to find out if your more-clear approach is correct, and assuming it is, the professor maybe uses it in the future.  If it's not correct, you get to learn where you went wrong.  A good exercise for all involved.
Comment: This. And based on personal experience on the professor's side: Do it, but please do this at maximum once per assignment. There is a fine line between being enthusiastic and annoying. If your professor points out flaws in your solution, consider your answer carefully. What might look like her opinion may actually be the result of years of experience.
Comment: _If you approach it this way, it should be perfectly acceptable to anyone._ While that's correct, personally I'm more impressed with a graduate student who shows me that they know their proof is correct (assuming it is) than with one who either can't decide whether their proof is correct or is appearing to feign ignorance out of fear of hurting my supposedly fragile ego. Bottom line: it's good to be cautious, but being overly timid carries its own associated cost and risks.
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/115175/discussion-on-answer-by-jeff-is-it-appropriate-to-email-a-professor-with-a-simpl).
Answer: It's okay to ask if your proof is right and, if it is, ask if there is an advantage in presenting an apparently more complicated version of the proof.
Keep in mind that, when teaching, the technique used in solving a problem can be more important than the solution itself.  It might be that this technique comes again later in the course, so having seen it once will help the second time around.
Comment: Or that the 'more complicated' proof will turn out to be generalisable to other settings...
Comment: Or that the 'more complicated' proof is actually more convincing to a beginner. For example, maybe similar proofs were discussed earlier, or maybe the steps require less specialized knowledge.
Comment: Or perhaps it simply the version in the course textbook (which then feeds into it being used later for a different problem)
Answer: Yes, it's fine. Professors are not snowflakes. You can communicate with them just as you would communicate with any other person. And presumably this professor is interested in the topic she is teaching and would be happy to learn about the simpler proof you found.
Comment: I found quite a disproportionate amount of academics to actually be quite sensitive to criticism. Given the power differential, the OP's question is not entirely unfounded. OP needs to find out what works for them. I am not saying that what you say is necessarily wrong, but it needs a caveat. That's basically it.
Comment: @CaptainEmacs fair enough. I see the wisdom in what you're saying. Thanks again for a nice discussion.
Comment: They are normal humans, but they are busy humans. That's a problem when trying to reach them.
Comment: @allo I don't see in what sense it's "a problem". OP asked if it's appropriate to send an email. Yes, it's appropriate. Unless OP wants an urgent reply (and there's nothing in the question to suggest that OP needs a reply at all), whether the professor is busy or not is irrelevant.
Comment: @DanRomik You're right and that's why it's a comment and not an answer. It's a small addition, which may be helpful.
Answer: Just to mention this possibility: it is very well possible that the professor finds her proof simpler than yours. Different people have different opinions on what is simpler / clearer, when it comes to proofs.
Do send her an e-mail, but maybe it is better not to be too absolute with "this is simpler than the other proof" when you write it.
Answer: Jokingly. When I was in my first year there was an exam in calculus. Part of it consists of student preforming a proof of their "favourite" law (one on the list).
Two students were able to reduce three-pages long proof just in three claims proof and one of them, after fair coin toss, walked in and performed this proof.
There were two professors assessing students, because there were too many students in the course so both were taking the lectures, plus one guest.
One of them and the guest were insulted by such mocking of the nice three pages of math (it was way too much shortening for them) and were attacking the student's claims and challenging the reasoning.
The other one enjoyed the proof and the discussion it led to.
In the end the student got mark A and just after their exam the professor who enjoyed the time crossed out the proof from the list for ever and since then they use the proof in their lectures and always naming it as Merryman-Trueman proof, after the two students.

TL;DR
A good professor will examine your reasoning and discuss it with you. Good professor will think high of your interest in th topic and your abbility to think outside of the box instead of memorizing-the-poem.
Bad professor will feel attacked by such arrogance of yours to undermine their genius...
It also depends how you word your email but in any case You will find what type of the professor you have encountered. Just stay polite.
Answer: Speaking as an erstwhile adjunct professor, my answer is:
I not only don't see anything wrong with that, I would encourage it. Obviously, you want to be polite about it, but otherwise, I think it's a valuable learning experience.
Of course, it could be that the prof knew of your easier proof but did not use it, for didactic reasons. Or it could be that the prof didn't know of it, or it could be that your proof has a mistake, or that it isn't as general as the proof offered.
Answer: I (in the U.S., in math...) would say "of course it's ok to send your own proofs to your professors for comment".
Asserting that your proof is "better", or similar stuff, is probably not productive. For that matter, as in other answers and comments, one of the most profitable outcomes is that you receive a professional critique of your argument, from your professor.
It's not that older people have special powers... apart from having lots of experience, which is almost like a special power, if they've been paying attention. :)
Comment: You can still mention that you *personally* think it is easier and possibly get interesting feedback why the professor thinks the other proof is easier to most people. Or they acknowledge that your proof seems to be easier. You just should not assume everybody has the same opinion, but only speak for yourself and see what's the feedback from other people.
Answer: I can only second Jeff's suggestion. Email the prof, say that you found an alternative proof and ask if it is correct. It is then up to the prof to decide whether or not it is "simpler".
I give my students props from contacting me with suggestions and if you play it that way I cannot see how this would be wrong or inappropriate. The worst case scenario is that either your proof is wrong or that your prof does not agree with it being simpler. Either case would not be an issue though.
Answer: Of course! You are in science, not politics. I hope! :-)
It's perfectly ok to tell the professor you found a proof you think it's simpler and much easier to understand. You can do that and still being polite. You can fully express what you have in mind, you don't have to pretend you are asking if it's correct or so, because then you only pass half the message you wanted to pass, the professor might not even be sure why you're sending it and you won't be satisfied with it.
Good professor will respond well. It's of course good to do it in such a way that the communication is just between you two. But possibly better than email is personal consultation, if it's available.
Comment: "Good professor will respond well". And bad professor?
Comment: @user111388 ... will show their bad temper. Bonus point - you will find a professor to avoid sooner or later.
Comment: user111388: exactly as @Crowley says: at least you will know he's bad and you know you don't want to do your Thesis or even PhD under him ;-) I know some stories from my PhD buddies how it can go if you cooperate with bad professor ;-)
Comment: @Crowley: Well, I'd say one can identify the bad professors earlier (at least a subset  of them) by paying attention during the lecture and avoid writing them an email. I had some professors completely uninteressted in teaching to which I know writing such an email would not end well for me (and my grade).
Answer: I would think that its perfectly okay to tell the professor that you think you have found an easier way. As long as your polite, and not telling the professor that they are doing a bad job (Or anything like that) then you should be fine. Just make sure you bring it up politely and ask if your easier solution would also work. Professors just want to educate students, so if you find an easier way, let the professor know as soon as possible so that she can teach other students your way, (if it works). That way you will be helping students in the future grasp a topic easier.


On what factors is a dissertation approved

Question: What are the factors that are considered when granting a PhD degree. For example, if a person has published excellent papers, but their dissertation is not perfect i.e. omissions and typos, would the committee consider it?
Also, what happens if they have good papers published, but the oral defense is not great.
People generally believe that if the dissertation advisors says OK, then everything works out. How true is that?
P.S. I am asking in the U.S.
Comment: In general, this depends on the process and rules of the university. In which country is this?
Answer: Although the exact process varies from university to university, the general form of the process in the United States is typically as follows:

The student needs to do work that makes a novel contribution to the sum of all human knowledge.  This is the universal part of the process, and the key thing that a Ph.D. really certifies that you are capable of.
The student, with guidance from the advisor writes up this work in a thesis document.  In some areas this is not-yet-published work, in others it is a summation of things already published.  In either case, it should be a complete and thorough presentation of the ideas and work.
Eventually the advisor and student are both satisfied, and the advisor judges that the student's work will pass external review.
External review is obtained from some combination of oral or public defense and input from other committee members.  Sometimes the defense is a serious part of the process, sometimes it is not; in either case, an advisor should never allow a student to stand for a defense unless they will pass.
The student satisfies any additional requirements imposed through the external review.  Sometimes this is just correcting typos, sometimes this is a lengthy period of additional research.  If it is the latter, then the advisor has generally screwed up.
Submit the final document for archive, and graduate.

Note that this process assumes some flexibility in the length of a Ph.D., which is typically the case in the US.  I know that in some other places, such as many institutions in Europe, there is often a shorter and fixed schedule.  I'm not sure how one deals with not being ready on time in that case...
Answer: It mostly depends on the university policy. Normally typoes are accepted to a certain extent as especially foreign students are not expected to manage the language perfectly.
Omissions on the other hand are a totally different thing. You have to omit many things anyway as they would not fit into the frame of your thesis. On the other handm if you omit something which is part of the area you are doing research on, then chances are high, that you are rejected - at least you will never get more than a "cum rite" and if you're satisfied with that, then I'd reconsider the whole doctorate-thing.
Answer: It greatly depends on the country and less so on the university. In general, it is true that a supervisor will not approve a thesis to be sent to the committee that he/she doesn't feel has a good chance of being accepted. Because doing so would not only reflect poorly on the supervisor, it also means more work for everyone involved.
In general, things like language errors are not cause for rejection unless you make it really bad. The thesis is judged primarily on its scientific content. Note that in some fields, you can create a thesis by simply making each published paper into a chapter and adding an introduction and conclusion. This allows for all of the critical parts of the thesis to be completed and reviewed beforehand.
The importance of the oral defense depends on the country. In my country, the Netherlands, the oral defense is practically irrelevant for most people. While in theory you can fail, as long as you keep talking, you will pass. It's mostly a show for friends and family. But in other countries the oral defense has more weight
Comment: Well, of course it is only dissertations in the sciences which are judged on their scientific content.


Parsing CityGML with PyXB

Question: I'm trying to parse a CityGML file in python in order to generate python objects from the buildings. Optimally the objects would have attributes corresponding to the elements in the GML, more or less like city.buildingID('123').roof.geom, which would give me the roof geometry.
I'm aware that specific elements/features can be extracted from CityGML using ElementTree, however I'm looking for a more comprehensive approach, because I need to iteratively access several different parts of each building.
I came accross PyXB, which to my understanding, could help me achieve exactly what I need. It generates python bindings from XSDs, then parses any XML using the corresponding schema to python objects. I generated the bindings using PyXB's provided binding-generator, adapted for CityGML2.0 (https://gist.github.com/balazsdukai/39668a068baf769f64d704e97baa6bbd).
Unfortunately my minimal example does not parse my minimal file. The file contains about 10 buildings, its CityGML2.0, semantically valid and has a non-planar surface according to val3dity.
import os
import pyxb
import pyxb.bundles.opengis.citygml.pbase as pbase # http://www.opengis.net/citygml/profiles/base/2.0

path = "loerrach_sub1.gml"

def citygml_read(gml_path):
    """
    Generates python classes from a citygml file.
    """
    gml = open(gml_path).read()
    pyxb.RequireValidWhenParsing(True) # do/not validate gml file when parsing to binding instance
    try:
        citygml_model = pbase.CreateFromDocument(gml, location_base=gml_path)
        return citygml_model
    except pyxb.ValidationError as e:
        print(e.details())

loer_sub1 = citygml_read(path)

The problem is that with pyxb.RequireValidWhenParsing(False) PyXB raises and exception:
pyxb.exceptions_.StructuralBadDocumentError:
{http://www.opengis.net/gml}FeaturePropertyType cannot accept wildcard content <pyxb.utils.saxdom.Element object at 0x7f5d728f1240>

The package author says that this is, because wildcards are not allowed by the schema (https://github.com/pabigot/pyxb/issues/53). Now, I manually checked if there are wildcards any* in the file but there are none.
Following I tried pyxb.RequireValidWhenParsing(True), but then I get:
The containing element {http://www.opengis.net/citygml/2.0}cityObjectMember is defined at cityGMLBase.xsd[47:1].
The containing element type {http://www.opengis.net/gml}FeaturePropertyType is defined at feature.xsd[76:1]
The unrecognized content WallSurface begins at loerrach_sub1.gml[10:0]
The {http://www.opengis.net/gml}FeaturePropertyType automaton is in an accepting state.
The following element and wildcard content would be accepted:
An element {http://www.opengis.net/gml}_Feature per feature.xsd[81:3]
Unable to convert DOM node {http://www.opengis.net/citygml/building/2.0}WallSurface at loerrach_sub1.gml[10:0] to binding

So, I don't really know what is going wrong here. It seems like something is missing from the bindings, but I believe I included all CityGML-related XSDs.
Answer: You might find the CityGML2OBJs and gml2obj tools helpful.
They are both Python tools parsing buildings meshes from CityGML files.

Parsing CityGML with PyXB


How to estimate sprint velocity with varying team capacity?

Question: We are a small team of 4 devs rather green in Scrum. Coming from all over the country, we often take odd days off or whole weeks off to go home. Therefore our team capacity changes dramatically from one iteration to another due to annual leaves, which leads to very different velocities from one iteration to another. How do we account for team capacity when estimating velocity at the Planning Meeting? Historical data will reflect very different capacities and we cannot wait one whole year to derive an average for our estimate velocity.
Answer: It might be a simple approach, but why don't you calculate your velocity as completed story points * capacity or completed story points / capacity, depending on how measure capacity. If you measure capacity in man-hours, use the second. If you measure capacity as a percentage of a 40-hour week, use the first. When you go to pull off story points, you should have a good idea about your capacity for a given sprint, and use your project's historical data to determine the story points completed for a given load.
However, this makes some potentially dangerous assumptions, such as treating all employees as equal - if your most junior developer takes a week off or the developer with the most experience in the domain and/or technologies takes a week off, your capacity will be the same numeric value, but the impact on velocity would probably be different.
Ultimately, use professional judgement based on historical data when planning a sprint. In this case, use previous velocity as an input into some other estimation scheme, involving the team. I would also err on the side of caution - it's easier to pull more work into a sprint than it is to remove a commitment to do a task.
Comment: Exemplifying the rationale with numbers, say at the end of Sprint n we have: 17 completed story points * 0.97 (1 dev's day out) = 16.49 velocity; using the other formula, 17 sp / 0.97 = 17.52. Now, comes the question. On the Planning Meeting of the follow Sprint (n+1), with a current capacity of 0.875 (5 days off among devs), what is our expected velocity? How do we estimate what we can accomplish with the reduced capacity?
Comment: @Pomario I'm assuming 2 week, 40 hour/week, 8 hour day sprints. Assuming one person took one day off, the capacity should be 0.99 for the first formula or 72 for the second. This gives you a computed velocity of either 16.66 or 0.24. Your capacity for the next sprint would be either 0.5 or 40. Plug the previous velocity and expected load into the equations. This means that you should bring in between 8 and 10 story points, since you multiple the completed velocity by your expected load. I'd err closer to 8 or 9. (Someone might also want to double check my math - I'm a bit sick today.)
Comment: I just realized I made a mistake - the first capacity would be 0.90, not 0.99, as 8 hours is 10% of an 80 hour work week. That means the computed velocity for the first sprint would 15.3. However, the analysis of the data doesn't change.
Answer: Velocity can vary even if capacity remains same.
So just trust your velocity it will take care of varying capacity itself i.e. assuming you are into 3rd sprint, take average of the last two completed sprints to commit to the next sprint. do not worry about variance in capacity.
Answer: Velocity is a guide, not a measure. Just take the average of all your sprints (account for standard deviation) and the average of your worst three, the average of your best three and say "We'll definately get these done, we might get these done, we won't get these done." By drawing three lines through your (fully estimated) backlog using these three velocities and your rough deadline (pretend it's 12 sprints and 12x your worst velocity is 75, 12x your best is 120 and 12x your average is 90. In a backlog of 100 points, even at your worst, you could do three quarters of it, at your best you'd nail the whole thing and on average, you'd deliver most of it).
With this data, your PO can make all the decisions he needs in what he MUST have, we he would like to have and what he doesn't mind leaving out.
Ultimate, things change, requirements are emergent and, well, things will change again. Don't bust your chops on maths to get a specific figure, accurate ranges are enough for this kind of thing. Bust your chops on software problems, not on backlog maths.


Moving domain/email from MS Exchange to GSuite

Question: I currently have a domain hosted by a company and an exchange email server and users use MS Outlook. I want to change over the domain from the current company to Google Domains and have the email through GSuite. How do I back up ALL emails ever received on each email to a .pst file to load into GSuite email? I know I can create the backup .pst file on a computer for emails on it, but will it pull all emails from server for backup even if they're 10 years old?
Answer: Have you read through this documentation?  https://support.google.com/a/answer/180898?hl=en


Sending GPS Location to server

Question: Is it possible to send my current location on iPhone or Android to the server so that others can view my current location?
Answer: Perhaps an email solution would be a workaround?
GPSLogger for Android app can automatically send an email with gpx or kml file to a specified address.

You could either push those emails to specified users or process the files on your server.
Answer: In Android there are many apps that will locate your location.
If you want to build your own app here is one way to do it.
Using GPS and Google Maps in Android - android:name="android.permission.ACCESS_FINE_LOCATION is the key
    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="net.learn2develop.GPS">
<uses-permission
android:name="android.permission.ACCESS_FINE_LOCATION" />
<application android:icon="@drawable/icon"
android:label="@string/app_name">
<activity android:name=".GPS" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>

Full source code:
http://www.devx.com/wireless/Article/39239/1954
Answer: This is a very broad question, with a dozen answers. The short one is: Yes.
But, I do not think you are as interested in the IF, as you are in the HOW.
I'm not going to get into details, but outline some possibilities.

Use an existing service such as Google Latitude
Make an app (using GPS libraries for the phone) or a webpage using html5 geolocation, and push the location to a server.
Comment: Google Latitude has been retired in 2013 (https://en.wikipedia.org/wiki/Google_Latitude)
Answer: Perhaps you could write an android app that uses the permission  (Just like Mapperz wrote), then sends this location to a database table on your server/hosting account.
Then you can write a simple map page that looks up the most up to date location of yours in that table using AJAX in every x seconds/minutes/hours etc. and refreshes the map accordingly.
For the timing on the client side lookup function, you can use an example like var location_lup = setInterval("your function()", 60000)
In case you want to stop the app looking up your location from the table, you can write clearInterval(location_lup);
Hope it helped!
Answer: One possible solution would be to build a web app in html5 and communicate your position to a web server set up in node.js. If you put the communication with the server as web worker it wouldn't freeze up your phone very time it contacts the server. Use html5 localStorage to store coordinates if you loose contact with the server
Answer: well you can find your location, and send that to server, so that other can find if and only if they have also installed the same application , there must be some permission also done to do this all.
use Google map you can have a look at the following website
http://www.trustingeeks.com/how-to-use-google-maps-v2-on-android-or-android-google-maps-api-v2-apps/

Sending GPS Location to server


My Tweets are not being received by the person concerned

Question: When I specifically tweet to a person B or tweet a pic mentioning the person's Twitter id (@id) the person B is not receiving my tweets in his home page unless the person follows me. When I specifically tweet to a person, they should receive my tweets, right? Why does this issue occur? I checked by creating two Twitter accounts.
Answer: No, that is not how Twitter works.
If and only if a person is following you, then your Tweets will show up in his/her news feed.
If you put @id into a Tweet, then the person will only see if it:

The person is following you, or someone else they are following sees
it and retweets,
The person looks at the Connect tab in his/her Twitter application.

If you want to guarantee that a person will see your Twitter-message, then use a Direct message - but you can only send these to your followers.
Comment: Ya i Know that but When I tweet by using @id the person should receive it whether they follow me or i follow them is it? But the person is not receiving. I checked with my friend and also I created another account and checked it.
Comment: When i reply to the persons tweet or pic i can see the tweet but others or even that person could not see my reply tweet. but if they visit my page they can see my repy tweet to the original tweet. why this occurs? This is diff none would have faced this issue.


How do I add another keyboards into Remix OS (Vietnam, Cambodia, Thailand Keyboards)

Question: I have a problem which are I cannot add another keyboards namely, Vietnam, Cambodia and Thailand. I cannot change the Keyboard from English language to Vietnam, Cambodia and Thailand languages. I have tried Khmer Smart Keyboard, Cambodia Keyboard APK and Phum Keyboard for Cambodia keyboard; Keyboard ManMan, Gadgetdoor Thai Keyboard, Thai Gingerbread KB and Thai Pack Without ALM97774503 for Thailand keyboard.
My host OS is Windows 7. I use VM-ware player to run Remix OS and Remix OS is marshmallow. How do I add another keyboards into Remix OS please?
Kindly please help me out. Any suggestion, I would appreciate it.
Answer: I think at now you can use Google keyboard that has those languages already: https://play.google.com/store/apps/details?id=com.google.android.inputmethod.latin&hl=en
It's also easy to switch between language.


If you modify a contract how does the new contract keep the existing tokens?

Question: I understand that you can't edit a contract, you can only create a new version of one. However, its not clear to me how the new contract can manage tokens created by the old contract. How does this work?
Answer: The only way that the new contract could manage the tokens is if you set the new address as the 'owner' of the token contract and assigned the balance, that is assigned to the previous owner, to the new address.
Another answer that I've written explaining about token contracts might help to clear things up for you.
If you need to upgrade the token contract, then it might be necessary to migrate the balances from the old token contract to the new one when you upgrade / create the new token contract.
Comment: This is sort of how I thought it worked, the contract manages the tokens because it maintains the ledger for them. If you moved the tokens to a different contract any existing users wouldn't be affected, right? They wouldn't know that there was a change. I've read about strategies for contracts like using redirects and versions that address the overall issue, but wanted to make sure I understood the core issue.