Atmega88p with shift register 74hc595

Question: I need to use a shift register to control multiple leds, but I need to control each one individually. The idea would be to send a buffer with the data, however I need to have several active leds and just want to change the state of each one at a time.
For example: change state of led in PIN 1 of the PORTC to HIGH,
then the led in PORTC PIN 2 to HIGH, then the led in PORTC PIN 1 to LOW etc ...
Can someone give me and advice or some example code?
Thanks for listening
Answer: That is doing it the hard way in my opinion.
Manipulate a byte (8 bits) or two with the LED on/off states.
Then just do a single SPI.transfer to send the data out.
All outputs will update at the same time. If you shift out the same data, the output stays the same.
<code>// time for an output change?
digitalWrite (ssPin, LOW); // SS goes to RCLK
SPI.transfer(dataToDisplay);  // SCK goes to SH_CLK, Data goes to Serial Data In
SPI.transfer(dataToDisplay2);  // use if have 2  shift registers.
digitalWrite (ssPin, HIGH); // all outputs update on this rising edge
</code>
Answer: The idea is to send the bits in the order in which the LEDs are attached to the shift register, meanwhile changing the clock pin for synchronisation.
You store one byte for each of the 8 LEDs (or less) you want to control. When you want to change one LED you change the appropriate bit, and send the bits to the shift register using the shiftOut function.
On an Arduino this is part of the library, otherwise you have to do it manually.
On this arduino shift out in native C question you can find the code, here is the fragment:
<code>void shiftOut(GPIO dataPin, GPIO clockPin, bool MSBFIRST, uint8_t command)
{
   for (int i = 0; i < 8; i++)
   {
       bool output = false;
       if (MSBFIRST)
       {
           output = command & 0b10000000;
           command = command << 1;
       }
       else
       {
           output = command & 0b00000001;
           command = command >> 1;
       }
       writePin(dataPin, output);
       writePin(clockPin, true);
       sleep(1)
       writePin(clockPin, false);
       sleep(1)
    }
}
</code>
In case you want more than 8 LEDs to control, you can store 4 bytes (uint32_t) and change the command argument type from uint8_t to uint32_t and the for loop to run until 32. Of course the shift registers need to be chained (max 4 for max 32 LEDs).

Atmega88p with shift register 74hc595


How do I fully uninstall the Diablo 3 beta for Mac?

Question: The beta doesn't have an uninstaller, Blizzard's directions are (by their own admission) not thorough. Where are all of the D3 directories and preference files, and what is the most effective way to zap them?
Comment: `Mac apps are notoriously difficult to fully uninstall` -  drag .app file or folder containing it to trash. Empty trash. Exceedingly rare is the program that dumps more than a small plaintext preference file anywhere else on your system.
Comment: Whenever I have to fully uninstall something, I use [AppCleaner](http://www.freemacsoft.net/appcleaner/). Plus, it's free.
Comment: "Fully" being the operative word. I've had my fair share of hidden caches.
Comment: @LessPop_MoreFizz apps are always leaving stuff in ~Library and various other places. From memory the StarCraft II demo required cleaning up.
Comment: @row1 Personally, I'm really not going to worry about 10kb of junk .plist files in ~library, which is the majority of what you're talking about. Unless you're troubleshooting, you really shouldn't need to either.
Answer:
Uninstalling applications in Mac OS X is very different than
  uninstalling in a Microsoft 1Windows environment because Mac OS X has
  nothing like the Windows Registry.
Most Mac OS X applications (anything that ends in .app), like Safari
  and iTunes, are bundles. The application icon you see in Finder
  (typically the Applications Folder) is usually a special folder
  itself, made to appear as a single double-clickable file. These
  "folders" contain all, or at least most, of the files needed to run
  the application, ie they are self-contained. This means that to
  uninstall these applications, you only have to drag them to the Trash.
  If you control-click (or right-click) on an Application icon, and you
  see "Show Package Contents", then it is a bundle.

Source
For Diablo III Beta, you just delete the folder, because it does not create Package Content for you to delete.
But it does create fill .txt files that are not part of the installation.
Here is a screenshot of my Mac with all files with "Diablo" in their name.

And here's the screenshot with the "Beta" name search:

Aside from the Diablo III "Beta Setup" that is in my Download folder, there is "diablo3_beta_enus-driverinfo.txt" that is in /Users/Shared/Battle.Net/Client/Blizzard Launcher.1454/Support
The others files are inside the folder in the applications (or in the location you selected).
Also inside /Users/Shared, there are 2 folders called: Battle.net and Blizzard. They are created after you install any Blizzard Game like WoW or SC or Diablo. I don't recommend to your remove those folders, unless you are going to stop playing Blizzard games.
Almost forgot:
There is a file that saves your preferences called D3Prefs.txt the location is: /Application Support/Blizzard/Diablo III
Comment: There is a folder in Application Support, too - `~/Library/Application Support/Blizzard/Diablo III`.
Comment: If you're going to be thorough enough to look in `~/Library/Application Support`, you should also probably delete the .plist files found in `~/Library/Preferences`. They all share the `com.blizzard.` prefix. You really shouldn't need to delete anything in /Library unless you're troubleshooting a bad install though. 20kb is not going to provide any useful additional storage space on a modern hard drive.
Comment: For me: Just delete the folder will solve the problem. The other files don't mess with nothing and they're not heavy.
Comment: @Adeese you are right. going to fix this.


Can Magento 1.9 be configured to load product images directly from an external URL:

Question: Is there any way to load images directly from external url, instead of importing images in to the server?
Comment: You mean like a CDN or simply get the images from some other place and don't manage images with Magento?
Comment: In product detail page, the images should be loaded from external url. It should not be downloaded. i.e directly shown from external url's like images from ebay, amazon,etc..
Comment: How do you plan to manage images and product relations? I suppose you want to throw a link in the product creation page and then render it in the frontend.
Comment: Yes, i can add the image urls into the new table based on sku.
Answer: AvS_FastSimpleImport has this feature implemented
Answer: I had many issues with the same problem, solved it by working around the code in
app/design/frontend/"MYTHEME/default/template/catalog/product/view.phtml.
after adding ximage attribute to the attribute set, I replaced the code in view.phtml from :
                <?php echo $this->getChildHtml('media') ?>

To
<IMG SRC="<?php echo $_product->getXimage();?>" ALT="some text" WIDTH=<?php echo '';?>" HEIGHT="<?php echo '';?>>

working fine
you can also add new attributes with size and width of the images, use image resizer function of your own and insert the new sizes in the html tag as above.
that's it.
Comment: Of course you need to save the image URL in the product ximage attribute
Answer: I had faced many problems while uploading Images to the magento store locally but its now working fine when I installed updated version of Adobe Flashplayer plugin for firefox browser.
External Images can be uploaded just by downloading to your device and there after you just upload onto your store.
Comment: The OP didn't indicate they were having any problems with the uploading functionality, just that they wanted to keep the images OFF of the local system and instead serve them from a remote host.
Answer: Short Answer: No, not really or at least not without an extension.
When you add an image through either the admin interface or via an import process, you're not just transferring a file.  That DOES happen on the initial upload, but there's some additional logic that gets executed as well when the image is rendered in place on a page as a full size, medium size, or thumbnail image: Magento takes the file and uses image processing functions to resize the image for the sizes configured in the image display theme templates.  This is done in a "lazy" manner - when you view a page with an image, magento checks to see if the correct size that needs to be displayed has already been generated. If not, the image is generated at the correct size then rendered.
Subsequent views use the pre-generated image. Once all image sizes have been generated it shouldn't resize anymore.
The PHP functions that perform this resizing can only do so if:

You have the correct permission set to allow apache (or Zend Server) to write to the folders and files system where images are stored and...
the base image has already been uploaded and stored on the local drive where apache (or Zend Server) have permissions to read and / or write.

If you store images on an external server, none of that works first and foremost because the php code as-shipped expects the location where it will be reading from to be on a local disk.
You could write your own extension that pre-generated all required size images upon upload to server, then transfer all images to an external server, then update all database records that refer to all those image url's to point to new IRM for each image size, but that is not trivial.  There may be an extension available that does this but default install does not.
Thought I would also add that directly linking to images hosted on eBay or Amazon that you don't host yourself may also run into legal complications of copyright infringement and / or perhaps just eating someone else's bandwidth without properly compensating them for the cost they incur or at least seeking permission (essentially trespassing on someone else's property).


How to access and use database in Window Phone 7?

Question: I am new to Window Phone 7 development and I want to create a simple database driven application. But I couldn't find a reference of System.Data.Linq or other dlls in my Windows Phone application. How can I do database operation, please give me easy solution.
Comment: You should probably use WCF Data Services or a similar technology; you should not connect directly to SQL Server from the phone.
Answer: This is a topic too complex to fit in a single, short answer. What got me going (if your question is about local databases) is the official introduction on MSDN: Local Database Overview for Windows Phone. This might already give you all information you need, in any case it has all the keywords you need for doing further research.
Answer: There are many sources of this information.  For starters, here is a link to the video in the MSDN How-To videos:
http://msdn.microsoft.com/en-us/hh336286
Here is a great link on delicio.us: Using SQL CE on WP7 Mango–Getting Started
http://devlicio.us/blogs/derik_whittaker/archive/2011/07/21/using-sql-ce-on-wp7-mango-getting-started.aspx
Here is a good one from Chris Koenig (MS Developer Evangelist):
http://chriskoenig.net/2011/10/14/using-databases-with-mango
And here is one by Claudiu Farcas:
http://claudiufarcas.blogspot.com/2011/10/windows-phone-mango-sql-ce-tips-and.html
These are some great resources to get you started.


running an executable in parallel by dividing the input directory tree

Question: Commands like find and grep would benefit greatly if they were to run in parallel. Is there a utility or a program that takes a command as an argument and makes it run in parallel by running multiple threads of the command, each on a subset of the directory tree?
Comment: See here: http://unix.stackexchange.com/questions/85859/variable-declaration-in-parallel-sh-c. There's a tool called parallel which will do what you want. Also you can use xargs to divide up file trees like so: http://unix.stackexchange.com/questions/63772/speeding-a-find-rm-command-with-test-through-parallelization.
Answer: GNU xargs has a -P command for that.
find . ... -print0 | xargs -r0P4 -n10 some-command

Will run up to 4 some-commands at a time with up to 10 files as argument.
Answer: Actually commands like find and grep are almost always IO-bound: the disk is the bottleneck, not the CPU. In such cases, if you run several instances in parallel, they will compete for I/O bandwidth and cache, and so they will be slower.
With a command that is more CPU-intensive, or in rare cases (e.g. a very fast RAID-1 that isn't otherwise busy together with a slow CPU), you can use tools such as GNU parallel or the -P option of recent versions of GNU xargs.
Assuming that file names do not contain newlines, the following commands invoke cpu_intensive_command on each file in turn, with two parallel threads:
find -type f | xargs -I {} -P 2 cpu_intensive_command {}
find -type f | parallel -X --number-of-cpus=2 cpu_intensive_command {}

An alternative strategy is to divide the work in two parts that you estimate are approximately equal. This requires no fancy tools, but does not balance the jobs between the processors.
cpu_intensive_command [a-m]* &
cpu_intensive_command [!a-m]*
wait

Answer: Walk through GNU Parallel's tutorial: http://www.gnu.org/software/parallel/parallel_tutorial.html and watch the intro videos: https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1


How do I hide submenus from the top menu bar?

Question: My website is wiki-style and has a lot of pages that should only be reached through links on other pages. Having these all accessible from the top menu bar under their respective headings leads you from dropbox to dropbox as each page has more subpages- a huge inconvenience.
 I've managed to hide these in computer view by creating a 'dummy menu'. I added a '-' to either side of my menu bar so it looks like part of the design, when actually they were nameless menus under which I listed all my pages. As long as people didn't click on them, they couldn't tell.
 It worked fine until I realized the menu bar looked different in mobile view- completely collapsed, and when you uncollapsed it you got the full list of menus and submenus covering your entire screen- including my five-mile-long list of pages under the dummy menus. It takes forever to scroll down to the actual article.
 The only 'hide' options I've found so far makes the page completely inaccessible, even through my links. Is there another way to decide which pages are visible through the menu bar? One that will allow 'hidden' pages to still be reached through links?
Comment: Not clear can you please provide more descrption
Comment: It depends completely on the theme. Most use WP Menus where you can un-check a box that says something about automatically adding new pages. If your theme does not use a WP Menu but instead something like `wp_list_pages`, you will need to create a child theme and insert your own menu instead - one that does not list out all the subpages.
Answer: If you want to hide sub menus all you need to do is not have them in the first place.  Try going to the admin panel's menus section and just remove the unwanted sub menus from the menu itself.


Current limit in boost converter

Question: The schematic is made by Great scott (a YouTuber).I need to know can we add a current limit to it by using a sense resistor and feeding the sensed voltage proportional to the current in the feedback controller opamp?My question is can I add the output of this current limit part  to the voltage feedback controller opamp?(in the inverting input)?
Comment: You've summed up what you need to do; put a shunt resistor in line on of the power rail, use an op-amp to amplify the voltage across said resistor. The question is what you do with this current limit, do you want a micro controller to read it? Do you want the signal to trigger a transistor to turn something off/on?
Comment: Yeah my bad ..I forgot to mention that .I was going for adjustable current limiting.
Comment: And what happens when there is an over current event?
Comment: Well that is why i wanna add a current limit function to it @Puffafish
Answer: With this topology, it's not possible to implement a current limit. See the current path? It's from the Vcc power source through L1 and D1 into the load.
There is no switched element in that path.
To add a current limit, you'd had to add a switch in the current path. Because a conducting MOSFET has lower losses than a diode, it is adviseable to put another MOSFET in instead of the diode D1.

simulate this circuit – Schematic created using CircuitLab
The path over R_limit and the diode is for preventing T1 and/or T2 to be shot by overvoltage if T1 is opened while current is flowing through L1 and T2 is not opened because of the current limiting function.

Current limit in boost converter


Exercise index (Pike pushups first or regular ones)

Question: I don't know which exercise should I do the first Pike pushups or regular pushups. I heard that you should start with the hardest exercise, which is pike pu for me but also I heard that you should start with compound exercises first, and pushups are more compound than pike pu.
Comment: Starting with the "hardest exercise" only makes sense if the exercises explicitly target the same muscles; while there's obviously some overlap here, pikes are more focused on the shoulders/tris than regular pushups (which also can hit tris depending on arm position).
Answer: I would say pike pushups first is likely ideal because these are callisthenic movements.
Compound first is typically something people say to people lifting weights. You don't want to do isolation work and tire out a muscle required in a lift or the rest of the muscles required in the lift won't get as much out of the session. Worst case scenario you tire out muscles required to maintain proper form in the lift and get injured.
Hardest first is something typically taught in calisthenics. This is because if you don't do it at the start of the workout, you probably won't be able to do that progression at all. Also, as Dave mentioned in the comments, this is taught because a lot of callisthenic moves have overlap in the muscles they use and virtually everything is compound.
The way I structure my workouts is one of the big three lifts first always. Bench, deadlift, and squat before anything. Next I prioritize the most difficult callisthenic movements going to the least difficult. I finish my workouts with isolation work for muscles I missed/want a bit more volume on.
Comment: Yeah, I never do pullups before I train my front lever. In calisthenics the general rule is to do your hardest progressions first.
Comment: Does this also apply to pullups and front lever raises, since the latter is more difficult than pullups?


Is third party content automatically published under the OGL?

Question: When publishing third party content for Pathfinder, is the published content automatically considered to be under the OGL? I was browsing http://www.d20pfsrd.com and see tons of third party content. Is this because they are required to allow this or are these simply the third party publishers that have consented to be on the site?
Answer: No, third party content for Pathfinder is not automatically open content.
However, many third party products do contain open content in whole or in part.  The way you can tell is that the product itself tells you.  Any OGL product contains a reprint of the OGL license along with a section that indicates what part of the product are Open Game Content and which are not (Product Identity).
d20pfsrd reaps the portions that are Open Game Content and collates it.
You'll note that even some of the Paizo classes from some Golarion books have different names on d20pfsrd; that's because the class itself was declared open content but the name had product identity in it.  Correctly identifying open content requires careful reading of the license the content's delivered with, avoid any sweeping generalization because it can get you into trouble.
Comment: ... but, as a very, very rough generalization, mechanics are typically OGL while fluff (including proper nouns) is rarely OGL. This is why Pathfinder (and the 3.5 SRD) has Mage's Disjunction instead of 3.5's PHB's Mordenkainen's Disjunction, for example.
Comment: The way that "Product Identity" is categorized however, leads one to believe that that it largely relates to names lore etc.

The core question that remains, Is can a mixed work that contains some OGL content, and some reserved non OGL content, that isn't just product identity (the concept) be categorized as 'Product Identity' (the keyword) for purposes of the contract.


Related Content Block for a Views Page, Not a Node Page

Question: I've created a views page that displays the most recent node of a certain content type. I have an image field in that content type that I would like to have displayed in the sidebar in a related content block. I have achieved this on the individual node pages using the contextual filter of NID with Content ID from URL. However, the views page is not the node page, so the related content block will not appear. How would I achieve this? Thanks!
Answer: You created views block which display current node images - right? What images you want to display on views page?
You can create another views block where display images from some nodes(add some term to nodes to mark them) or images from recent nodes which views shows.
Comment: The views page is essentialy the same as the node page, except that it is limited to the most recent node of a certain content type. This is so I can have a menu item that will link to the most recent node. I want the related content block to display the images related to that specific node which is being displayed as a page view. Since the user can upload an unlimited amount of images for each node, I can't limit the display of the view because I do not know how many images there are.
Comment: Create new views block which select images from recent node and place it on views page
Comment: Thanks for the quick reply. How would I limit the images to the most rencent node?
Comment: Views have a field option to limit multiple field values or use pager options if you display images as a separate rows


What does this phrase mean "value to me the cost"

Question: In an English translation of a letter of Cicero I came across the phrase 'they will value to me the cost of my former house and site.' (letters to Atticus IV.1). Does anyone know what this means or have a better translation? If so much obliged.
Comment: I'm voting to close this question as off-topic because it appears to involve non-standard English; interpretation of such becomes largely a guessing game.
Comment: I think this question is worth answering. It is about the concepts of 'value' 'cost' and 'price' and it is about the way in which the English language deals with numerical cost, intrinsic value and transactions between humans on that basis. (And welcome  to EL&U, by the way.)
Comment: In similar translation issues, it's always a good idea to cite the source of the text and add a link. That way we avoid the plausible accusation that the translation was by a non-native speaker if I'm to understand Ashworth's comment and reason for closing the question. Luckily, Colin Fine's answer provided the source and the link.
Answer: It appears to be using value in a strange way, that I cannot make much sense of. The normal meaning of the verb is "to determine the value of".
The translation seems to be considerably more copious than the Latin original rem totam aestimabunt ("they will value the whole affair"), which is rendered here as "value to me the cost of a site and house". This is evidently the translator's (Evelyn Shuckburgh) attempt to make it clearer to an English reader; but to my mind he has made it less clear by this "value to me".
I find no evidence that the Latin aestimo means anything but "determine the value of" (like the English verb value). Lbf's answer seems to suggest that the implication is that the state will pay Cicero that value if they take his land. That is as good an interpretation as any; but I don't think that the English word value normally has this meaning - certainly the OED does not list it.
Comment: agree ... i edited my answer.  My reading of the paragraphs implied he would be made whole if they did take such.  I simplified ... but it may have been meant that he would get property elsewhere of same value.
Answer: Letters of Cicero

They will value to me the cost of my former house and site.

As in:

He will be paid if they (the state ) take his land ect.

or

He will be given land etc ... of same value.

In any event he is happy with the arrangement ( i read the paragraphs before and after ).


OpenCV move to begin frame position fail

Question: I am trying to use OpenCV VideoCapture to read some frames for training. After training, I would like to return to the beginning of the video and do processing. The problem is that OpenCV VideoCapture set(CV_CAP_PROP_POS_FRAMES, 0) cannot return to the beginning of the video.
VideoCapture cap("video1.mp4");
if( !cap.isOpened()){
    cout << "Cannot open the video file" << endl;
    return -1;
}

// read some frames here

int count = cap.get(CV_CAP_PROP_FRAME_COUNT); //get total frame count
cap.set(CV_CAP_PROP_POS_FRAMES, 0); //Set index to 0 (start frame)

int index = 1;
while(1)
{
   Mat frame;
   bool success = cap.read(frame);
   if (!success){
     cout << "Cannot read  frame " << endl;
     break;
   }
   cout << "the current frame: " << index << endl;
   index++;
}

In the program, the final index value would not be same as frame count. Say a sample running would be:
index = 3774 and count = 3786
index = 3764 and count = 3776

I also try to set frame index using CV_CAP_PROP_POS_MSEC (according to a post). But it didn't work.
My current solution is to reconstruct a VideoCapture and read from begin to end.
Can anyone explain why set can even not return to the beginning of the video? I think it go nothing to do with the decompression algorithm.
Answer: Try
cap.set(CV_CAP_PROP_POS_AVI_RATIO, 0);

or
cap.set(CV_CAP_PROP_POS_FRAMES, 0);


Lock orientation (Portrait) on VueJS PWA for all browsers

Question: I am trying to get a screen lock to work for my web application.
I have been searching the forums but cant find a solution to this problem.
Does anybody know how I can tackle this problem?
Problem solved with a css fix.
Answer: I used the scss media queries to solve this problem.
<code>@media screen and (min-aspect-ratio: 13/9) {
  html {
    transform: rotate(-90deg);
    transform-origin: left top;
    width: 100vh;
    overflow-x: hidden;
    position: absolute;
    top: 100%;
    left: 0;
  }
  .bw-dashboard {
    height: inherit;
  }
}
@media screen and (min-width: 1292px) {
  html {
    transform: none;
    transform-origin: none;
    width: 100%;
    overflow-x: none;
    position: relative;
  }
  .bw-dashboard {
    height: 100vh;
  }
}
</code>
Answer: Currently PWAs do not have an overall working solution and I think the CSS approach is not very satisfying.
But you can use the ScreenOrientation API which will work for all browser except Safari and Edge (mobile/desktop). Do not use the outdatet Screen API.
If you plan to wrap your PWA into a mobile app, frameworks like Capacitor or Cordova will provide a native bridge to access the respective orientation lock feature.


How can a turbofan's fan generate thrust in cruising flight if air is being slowed down?

Question: High bypass turbofans in airliners generate most of their thrust from their fans, not their "cores". However, at cruise they are actually spilling some air past the intake rather than sucking air in (in contrast a propeller always creates a low pressure "suction" in front of it). Given that the air ingested is being slowed down, how can the fan generate thrust? I assume that the air is forced out the exhaust at an even higher speed than cruise? The exhaust has a smaller area than the intake thus the higher exit speed?
Answer: While in cruise, air is actually pushed into the propeller or fan, there is no "sucking in" taking place which would imply a lower pressure at the fan than the surrounding air.
Source: TU Delft lecture handout Vliegtuiggasturbines by C.J. Houtman
Pic above was used earlier in this answer, and shows the fan inlet in cruise (left) and at take-off (right). The in-flowing air has kinetic energy, and slowing it down by expansion in the fan inlet:

increases pressure in front of the fan
allows the fan to add energy to a slower airflow, generating lower compressibility losses.

So the fan adds energy to the incoming airflow, both in the form of increased pressure and increased velocity. Further downstream after the fan, the extra pressure is traded in for a further increase in velocity, until the flow is expanded to the surrounding pressure.

However, at cruise they are actually spilling air past the intake

Not really, air does enter the intake. The front end of the fan nacelle is shaped such that inflow is optimised at cruise.

I assume that the air is forced out the exhaust at an even higher speed than cruise?

Correct, this is what creates thrust.

The exhaust has a smaller area than the intake thus the higher exit speed?

Yes, subsonic airflow accelerates when the stream tube diameter is reduced.
Comment: (Please change the figure caption to show that cruise is (a) and take-off is (b)))
Comment: Sourcing your images & charts would be appreciated and is expected.
Comment: @FreeMan Indeed it is, you're right. It's from my treasured university lecture handout "Vliegtuiggasturbines", decades old and paper format only.
Comment: Ah, well then, University, course ID & title, professor and time slot, please! :D
Comment: @Freeman yep it's in the figure reference (press Edit)
Comment: Unfortunately, that's only visible to those for whom the image doesn't load (as the alt-text), or to those with screen readers (that will read the alt-text to them), or to those with edit privileges (or think to edit the question and discover it there), so I've updated it a smidge. Hope you don't mind.


Could a malicious attacker subvert the Bitcoin network by failing to create a block?

Question: I know its astronomically improbable, but say a malicious node "wins" the proof of work inherent to the Bitcoin protocol. If a malicious node simply waited indefinitely, or maliciously disconnected during the block creation process, what would the Bitcoin network do about it? If a block isn't created will the network just hang indefinitely, or is there some way of overcoming a halt like this?
Comment: Possible duplicate of https://bitcoin.stackexchange.com/q/22978/5406
Answer: The other miners will not be aware that this malicious miner has find the correct hash(win) since he has not propagate it, so they will still try to find the correct hash and some second later one of them will find it correct and propagate it, then cycle will repeat again without anyone knowing that this malicious miner has win second before the one that has officially win it.
Comment: Interesting. How about proof of stake?
Comment: There is no competition between miners in proof of stake, it depend on the implementation but for EOS for example which is Delegated proof of stake, if one of the 21 selected current "block producer" is unable or refuse to publish one of his block, the code force the next scheduled block producer to take his place.


Filter webpart and consumer web part

Question: I have a Customer filter web part tie to a list. and It's working good. and I have a order list web part. The set up is working fine. However, is there a way not to display any order data from the order list web part if there are no selection in the customer filter web part. or if user selects empty.
Comment: I have added the output to show to you it's working as you request in your question!! please check from your side you have configured the provided list as I have mentioned in my answer , also please have a tour in http://sharepoint.stackexchange.com/tour to know where you can comment and where you can answer Thanks!!
Answer: Yes you can disallow displaying any order data from the order list web part if there are no selection in the customer as the following:

Edit Page > Edit the provided list, in this case, it is the customer.
Below Miscellaneous > uncheck Send the first row to connected Web Parts when page loads

Output

once the item is selected it will filter as shown below
Answer: I added "Select a Value" to the filter webpart and that worked. Now all 4 other consuming webparts are showing no records. User selects a value from filter and all 4 webparts are showing related values. Thanks everyone for your help.

Filter webpart and consumer web part


Goal of macerating fruit for marmalade

Question: I have a recipe for kumquat marmalade, it calls for 2 parts fruits, 1 part sugar and 1 part water. Before boiling the liquid it states that one should macerate the fruit in de sugar water first. How does this maceration help?
Comment: Related : https://cooking.stackexchange.com/questions/94760/
Answer: Macerating breaks down the fruit and extracts the juices. Especially when making jam, it can expedite the process, allowing you to prep the fruit a day in advance. While some recipes say to macerate for several hours, letting it sit overnight can produce better results, particularly when using dried fruits.
Answer: It softens the fruit peel and membranes, and reduces the amount of additional water required, so cooking time is reduced and saves resources. Also softening peels and membranes without long cooking preserves  fresher flavour within the fruit. From personal experience. I do all jams, marmalades and conserves with maceration overnight now. Flavours are much improved.
Answer: Maceration is the "magic" (really science) of applied osmotic pressure. The sugar mixture will draw fluid out of the fruit (indeed, many maceration steps are done by mixing the dry sugar with the fruit, rather than by placing the fruit in sugar-water - there is soon fluid, and the osmotic pressure is considerably higher since the concentration of sugar is higher. If water is needed, it would be added after maceration, in those recipes.)
Comment: This is a good explanation of the mechanism behind maceration, but it doesn't say why somebody would want to have macerated marmalade instead of a non-macerated one.

Goal of macerating fruit for marmalade


What are the requirements of a transaction being included in a block?

Question: What are the requirements of a transaction being included in a block? How does a miner verify that a transaction meets such requirements?
Answer: From the Bitcoin wiki (as-of March 19, 2013):

Transactions are cryptographically signed records that reassign
  ownership of Bitcoins to new addresses. Transactions have inputs -
  records which reference the funds from other previous transactions -
  and outputs - records which determine the new owner of the transferred
  Bitcoins, and which will be referenced as inputs in future
  transactions as those funds are respent.
Each input must have a
  cryptographic digital signature that unlocks the funds from the prior
  transaction. Only the person possessing the appropriate private key is
  able to create a satisfactory signature; this in effect ensures that
  funds can only be spent by their owners.
Each output determines which
  Bitcoin address (or other criteria, see Scripting) is the recipient of
  the funds.
In a transaction, the sum of all inputs must be equal to or
  greater than the sum of all outputs. If the inputs exceed the outputs,
  the difference is considered a transaction fee, and is redeemable by
  whoever first includes the transaction into the block chain.
A special
  kind of transaction, called a coinbase transaction, has no inputs. It
  is created by miners, and there is one coinbase transaction per block.
  Because each block comes with a reward of newly created Bitcoins (e.g.
  50 BTC for the first 210,000 blocks), the first transaction of a block
  is, with few exceptions, the transaction that grants those coins to
  their recipient (the miner). In addition to the newly created
  Bitcoins, the coinbase transaction is also used for assigning the
  recipient of any transaction fees that were paid within the other
  transactions being included in the same block. The coinbase
  transaction can assign the entire reward to a single Bitcoin address,
  or split it in portions among multiple addresses, just like any other
  transaction. Coinbase transactions always contain outputs totaling the
  sum of the block reward plus all transaction fees collected from the
  other transactions in the same block.

http://en.bitcoin.it/wiki/Protocol_specification#Transaction_Verification
Comment: Yeah, I read that. Not at all what I meant. I mean, how does a client/node do what is described in that article? How can I improve the question?
Comment: If you read C++, it is documented best in the bitcoin/bitcoin project on GitHub.  I know you are probably looking for a technical paper.  The source code is where that exists for now.
Comment: Or PicoCoin shows it fairly well, in C: https://github.com/jgarzik/picocoin
Comment: Or the most simplified pseudocode:

If UTXO is not yet spent, eligible for including in block.
If space in block, include eligible transactions.


Music won't play on my iPhone 5s why not?

Question: I go onto my music and select a playlist I want to listen to, I then click shuffle or select and song and it won't play. It looks like it is about to play but then it automatically pauses and skips to the next song. If you click play it restarts the song - no sound comes out and if it switches to a song that does decide to act normally there is no sound at all. I have tried plugging in head phones; this makes no difference and then taking them out; this again makes no difference. I have tried turning on the ringer and turning it off, again this makes no difference. Mobile data on, data off, no difference. Bottom line is I can't play my music. I am using an iPhone 5s with iOS 10.2. Please help :)
Answer: Have you tried also restarting the phone? I have the same phone model and do have to reboot it every once in a while.


Chaotic circuit for random number generation

Question: I know, there is an analogy between RLC circuits and harmonic oscillators. Now there is a physical system, called double pendulum which has chaotic motion. I'm just curious if it is possible to create a circuit, which behaves like a chaotic pendulum, and use it for hardware randomization?
Comment: Um, have you tried http://www.chaotic-circuits.com/ ?
Answer: Chua's circuit is a chaotic oscillator built from a RLC circuit and a nonlinear element. It's not simulating a double pendulum directly, but generates chaotically oscillating output.
If you're looking to generate hardware random numbers and aren't concerned about double pendulums specifically, there are easier ways. See wikipedia for examples. One famous but impractical technique was Silicon Graphics' random numbers generated from a lava lamp.
Intel's Ivy Bridge processors use metastable R-S latches to generate true randomness from thermal noise. So if you just want hardware random numbers, your computer may have them already.
Answer: The double pendulum: -

I'm just curious if it is possible to create a circuit, which behaves
  like a chaotic pendulum

Yes you are watching it - your computer is a circuit and it is modelling it right in front of your eyes. Not only is this an answer, it is proof all in one package.
Of course, if you wanted to take the differential equations and do it using op-amps, this is also possible. Picture taken from this wiki page entitled double pendulum
Comment: Well... It is a a recorded animation, not a simulation itself. But your point is clear up to the fact that a digital simulation is not the same as the actual process (I would say it is not *really* chaotic by itself).
Comment: +1 for the eye candy (but it's the same each time!)
Comment: The important words are "which behaves like" LOL


How does density of alkali metals increase down the group?

Question: Size of alkali metals increases down the group, so volume also shows increment, and since volume is inversely proportional to density, how does density also increase down the group?
Comment: The molar volume increases from 13.10 cm$^{3}$/mol for Li to 71.07 cm$^{3}$/mol for Cs. Mass increases from 6.9 gm/mol for Li to 132.9 gm/mol for Cs. So, the mass per atom increases faster than the atomic density decreases.
Comment: Because mass is also increasing, presumably faster than volume.
Comment: Do you mean "why"? "How" suggests you may want to know whether the increase is linear or some other mathematical function.
Answer: $Density=mass/volume$
1) If mass is increasing and volume is decreasing, then density (mass/volume) will increase.
2)If mass is decreasing and volume is increasing simultaneously, then the density (mass/volume) will decrease.
*3)If both mass and volume are increasing, then we need to check which one of them is increasing at a faster rate(since both are contradictory factors)
a) If mass is increasing at a faster rate than volume, then density will increase.
b) If volume is increasing at a faster rate than mass (i.e denominator in mass/volume is increasing making the overall fraction smaller), then density decreases.
You can apply same logic when both volume and mass are decreasing simultaneously.
Generally, we see that in alkali metals the rate of increase of mass is greater than rate of increase of volume, therefore the density increases down the group.
Also, note that there is no definite reason for why mass is increasing at a faster rate than volume. So asking "why" does it happen isn't a great question.
Answer: Its just because density is directly proportional to mass. And the mass increases faster than that of volume expect for the case of potassium which is lighter than sodium.


How to find the eigenvectors and eigenvalues of a hermitian operator?

Question: While reading Theoretical Minimum by Leonard Susskind, I came across the exercise 3.4 where he asked to find the eigenvalues and the eigenvectors of the matrix that represents the $\sigma_{n}$ component of the operator $\sigma$ where: $$\sigma_{n}=\vec\sigma.\hat n$$
Which leads to:
$$\sigma_n=\begin{pmatrix}n_{z}&(n_{x}-i.n_{y})\\(n_{x}+in_{y})&-n_{z}\end{pmatrix}$$
Given that:
$$n_{z}=\cos(\theta)$$
$$n_x=\sin(\theta) \cdot \cos(\phi)$$
$$n_y=\sin(\theta) \cdot \sin(\phi)$$
How can I approach the question as I am a little bit confused, and I searched online for the answer and found that we need to find the determinant of the $\sigma_n$ where is equals:
$$\begin{pmatrix}\cos(\theta)-\lambda&\sin(\theta)\cdot\cos(\phi)-i\cdot \sin(\theta)\cdot\sin(\phi)\\ \sin(\theta)\cdot \cos(\phi)+i \cdot \sin(\theta)\cdot \sin(\phi)&-\cos(\theta)-\lambda\end{pmatrix}$$
How does finding the determinant of $\sigma_n$ help solve the question and where did the $\lambda$ come from in the first place?
Comment: Can you link the online answer you are talking about? And also, how familiar are you with linear algebra? So that people can answer your question accordingly.
Comment: Here is where I got the answer: https://quantum-abc.de/Exercises%20complete1.pdf. My mathematical knowledge is mostly from high school.
Answer: From your post and the comments therein, it seems that you would benefit in reading a little bit more about linear algebra. There are plenty of resources for that, including some excellent posts on the Mathematics StackExchange.
In this post, I will only answer your question about why finding this determinant allows to compute the eigenvalues of a matrix. However, it's quite hard to answer such a question with high school knowledge only, so I'll assume just a tad bit of knowledge about matrices (hopefully not much, but feel free to ask questions in the comments).
We will need several facts:

If a matrix is not invertible, its determinant is nil. Reciprocally, it is invertible if its determinant isn't nil.
If there is a non-zero vector $x$ such that $Mx$ is the zero vector, then $M$ isn't invertible. Reciprocally, if the only $x$ such that $Mx=0$ is $x=0$, then $M$ is invertible.
If there is a non-zero vector $x$ such that $Mx=\lambda x$ for a certain $\lambda$, then $\lambda$ is an eigenvalue of $M$.

With that being said, let us consider an eigenvalue $\lambda$ of a matrix $M$. From Fact 3. we have:
$$Mx=\lambda x$$
Which we can rewrite as:
$$Mx=\lambda Ix$$
with $I$ being the identity matrix. This is equivalent to:
$$(M-\lambda I)x=0$$
But now from Fact 2. we have that $M-\lambda I$ is not invertible, which means from Fact 1. that the determinant of $M-\lambda I$ is nil.
Thus, we have shown that if $\lambda$ is an eigenvalue of $M$, then the determinant of $M-\lambda I$ is nil.
Reciprocally, if $\lambda$ is not n eigenvalue of $M$, then we can show that $M-\lambda I$ is invertible. Suppose that:
$$(M-\lambda I)x=0$$
Then it means that:
$$Mx=\lambda x$$
But we have assumed that $\lambda$ is not an eigenvalue of $M$, so it necessarily means that $x=0$. Thus, from Fact 2. $M-\lambda I$ is invertible, which means from Fact 1. that its determinant is not nil.
All in all, we have shown that the eigenvalues of $M$ are exactly the solutions to the equation
$$\text{det}(M-\lambda I)=0$$
Where we want to solve for $\lambda$.
If you want to learn more on this topic, you should read about the characteristic polynomial of a matrix.
In your case, you will find that the determinant is actually a degree 2 polynomial in $\lambda$. You should thus be able to quickly find the eigenvalues.
Once you know an eigenvalue $\lambda$, there are several ways to compute the eigenvectors. The simplest is simply to solve for $x$ in $Mx=\lambda x$. Such an $x$ isn't unique, but you're interested in linearly independent solutions here.
This might be a bit too much for an high-school level and I apologize for that. But to put it in a nutshell:

The determinant of $M-\lambda I$ is called the characteristic polynomial of $M$, and its roots are exactly the eigenvalues of $M$.
Using the definition of an eigenvalue, it is possible to find an eigenvector associated to a known eigenvalue.
You should definitely get yourself an introductory course on linear algebra if you're interested in that topic, you'll learn a lot of things!
Comment: As for learning linear algebra, I would highly recommend [Greg Sanderson's Essence of Linear Algebra series](https://www.youtube.com/watch?v=fNk_zzaMoSs&list=PLZHQObOWTQDPD3MizzM2xVFitgF8hE_ab) to get an excellent intuitive understanding. If you are looking for something slightly advanced, then I would recommend [Gilbert Strang's Linear Algebra Course at MIT](https://www.youtube.com/watch?v=7UJ4CFRGd-U&list=PL221E2BBF13BECF6C).
Comment: @zizaaooo Oops, you're right! Its determinant isn't nil, so $M-\lambda I$ is invertible indeed, sorry for that!
Comment: Thanks a lot, but I why did you make a point about $x$ being 0 if $\lambda$ is not an eigenvalue of $M$?
Comment: @zizaaooo In this step, our goal is to show that if $\lambda$ is **not** an eigenvalue of $M$, then $M-\lambda I$ isn't invertible. In order to do this, we use the second part of Fact 2. : we show that the only $x$ satisfying $(M-\lambda I)x=0$ is $x=0$.
Comment: Do you mean that $M-\lambda$ is invertible because the only solution is $x=0$ if the $\lambda$ is not an eigenvalue of $M$? Because you  wrote in the first line of your comment that $M-\lambda$ isn't invertible. I might be repeating what you just said but I want to make sure that I understood your answer.


Adding storage above garage ceiling

Question: I'd like to add some storage space in the ceiling of the garage. It looks like someone got a start on it already. There looks like a 16 foot 2x4 nailed into the top of the wall on both sides with one 2x4 spanning. If I put more 2x4s across the span every four feet, is that going to hold a plywood subfloor and some light storage
Comment: That 2x4 is more to hold the bottoms in place when building.  Some plywood will not hurt, but the main thing is LIGHT storage.  Those trusses are not built to hold weight.
Comment: @Ecnerwal I added two more images
Comment: @crip659 Is there any way to reinforce the tursses?
Comment: I should have said heavy weight.  It also depends on how the weight is spread out.  Usually it is pounds per square foot.  200 pounds over 20 square feet is much better than 200 pounds on 2 square feet.
Comment: @Chad can you provide a better "lengthwise" picture of this space showing the trusses?
Answer: Ideally, you find out who made your trusses and get the specs from them for exactly what they were designed for. That information may be in plans which may be on file at your LAHJ or there may be information stapled to or written on to the face of one of the trusses.
These pictures make it hard to tell, but there's some chance it's actually a "spare room" or "attic" truss with potential weight-holding capacity designed in. The apparently open center and relatively heavy bottom chord suggest that.

Image source https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fswifttimber.co.uk%2Fuploads%2Fimages%2Ftrussed-roofing%2Ftruss-attic.png&f=1&nofb=1&ipt=98a0dd23d6fd60eb00cd9803978a0127208028a67186b104779b8fbabd91fc65&ipo=images no endorsement implied
Your new pictures make it quite clear that's exactly what you have for a truss, and as such, it should take reasonable loads (still would be ideal to track it down and find out what it's designed for,) but this is not "just rafter ties" nor is it a truss that's only intended to support the roof and a ceiling below. Truss spacing appears to be 24" on center, so 3/4" ply/OSB (T&G preferred) should be floor-span-rated for that spacing directly, no extra 2x4's needed.
When you have half the floor sheathed and properly connected to the chords, you can remove the "rat-board" 2x4 down the middle and keep going to the other side, since all that is doing is holding the bottoms of the trusses, which the floor will do once it's in place.
Comment: The mending plate on the chord would concern me.
Comment: @Mattman944 that's a very normal part of engineered truss manufacturing. Not a field repair, and nothing to be concerned about.

Adding storage above garage ceiling


How to combine elecrolytic capacitors into one big bipolar one

Question: I want to make capacitor with large capacity which can hold both positive and negative charges. Is it possible to combine elecrolytic capacitors somehow to achieve this?
Comment: Yes, of course it is possible, somehow. But then what? There's not enough info how would you like to use such a cap, what would it achieve and how would you like to charge and discharge the capacitance?
Comment: Two electrolitics each with a protection diode would get you most of the way there, though the reverse voltage through the diodes would significantly reduce the life of the caps. Why are you trying to do this? What's wrong with unpolarised caps? Or it might be easier to rectify the input voltage, and then carry on with a polarised cap. Depends on why you are doing this and what the rest of the system is.
Comment: Yes, by putting them in anti-series. See here: https://newbedev.com/can-you-make-a-non-polar-electrolytic-capacitor-out-of-two-regular-electrolytic-capacitors
Answer: Yes. There are two ways to do this. The rough way, and the nice way.

simulate this circuit – Schematic created using CircuitLab
The rough way is to omit the positive bias and R1. Diodes D1 and D2 will conduct when required to rectify the input signal and 'pump up' the middle node to keep the capacitors from becoming more than one diode drop reverse biassed, which is usually OK for aluminium electrolytics. While the initial charging is happening, the overall capacitor will appear to have a value of C1 or C2, with a diode drop in series. Once the middle node is charged, the capacitor will behave as C1 in series with C2, capacity = C1*C2/(C1+C2).
The nice way is to use a positive bias to pre-charge the middle node to more than the expected signal swing. This will keep both capacitors correctly biassed throughout. The diodes are still required for safety.
Usually, you'll make C1 equal to C2, though there's no requirement to.
Comment: How to make C1 equal to C2 if tolerance +80%/-20%? Why just not a bridge?
Comment: How does the bias work if the capacitors are discharged? You'd have to charge the capacitors through the bias before the bias becomes effective, not?
Comment: @RJR which bit of 'precharge' don't you understand?


Turning Off Wi-Fi During Logout Script Doesn't Work With Launchd

Question: I'm writing a launchd plist and a shell script on my MacBook running Yosemite to automate the following scenario:
Turning off Wi-Fi when the user logs out.

Here's my script:
#!/bin/sh
onLogout() {

    #Turning off Wi-Fi. Tested in the Terminal and worked.
    /usr/sbin/networksetup -setairportpower en0 off

    #Log a message as a proof that the script is executed
    echo 'Logging out' >> ~/Desktop/logout.sh.log
    exit
}

trap 'onLogout' SIGINT SIGHUP SIGTERM
while true; do
    sleep 86400 &
    wait $!
done

When I logged out, I did see the log message appearing in the log file. But the Wi-Fi was still on.
Please help.
Answer: Use networksetup -listallhardwareports to get a list of all network devices. Usually en0 is the ethernet interface, en1 is WiFi.


Cannot get the jQuery Vertical Slider to work on the iPad

Question: I am trying to get jQuery Slider to work on the iPad but failing at every attempt I do!
Please does anyone know how to do this? Many Thanks in Advance :)
Answer: Adding the "Touch Punch" plugin will add touch-support to current jQuery UI plugins: http://touchpunch.furf.com/
Answer: Try jQuery mobile rather than jquery UI - jQuery mobile is specifically designed with touch based devices in mind.
You can see the slider functionality here:
http://jquerymobile.com/demos/1.0b1/#/demos/1.0b1/docs/forms/forms-slider.html
Answer: Take a look at touchstart, touchend and touchmove events for idevices. Take a look at
How do I make a JQuery Slider-like feature on iPhone/Android web app?


How to show that $A^3+B^3+C^3 - 3ABC = (A+B+C)(A+B\omega+C\omega^2)(A+B\omega^2+C\omega)$ indirectly?

Question: I found this amazingly beautiful identity here. How to prove that $A^3+B^3+C^3 - 3ABC = (A+B+C)(A+B\omega+C\omega^2)(A+B\omega^2+C\omega)$ without directly multiplying the factors? (I've already verified it that way). Moreover, how could someone possibly find such a factorization using complex numbers? Is it possible to find such a factorization because $A^3+B^3+C^3 - 3ABC$ is a symmetric polynomial in $A,B,C$?
Comment: A general formula for $A^n+B^n+C^n$ in terms of the symmetric polynomials $$s_1=A+B+C, s_2=AB+BC+AC, s_3=ABC$$ is $$A^n+B^n+C^n = \sum_{i+2j+3k=n} (-1)^j\frac{n}{i+j+k}\binom{i+j+k}{i,j,k} s_1^is_2^js_3^k$$ Not sure how that would help, but the RHS has a term $+3s_3$ when $n=3$.
Comment: Specifically, $$A^3+B^3+C^3 = (A+B+C)^3 - 3(A+B+C)(AB+BC+AC) + 3ABC$$
Answer: We know $(A+B)\mid(A^n+B^n)$ for $n$ odd. What about with three terms? Compute
$$\mod A+B+C:\quad A^3+B^3+C^3\equiv-(B+C)^3+B^3+C^3\equiv-3BC(B+C)\equiv 3ABC.$$
So $(A+B+C)\mid(A^3+B^3+C^3-3ABC)=f(A,B,C)$. Further
$$f(A,B,C)=f(A,\omega B,\bar{\omega}C)=f(A,\bar{\omega}B,\omega C)=\rm etc.$$
by inspection so both $A+\omega B+\bar{\omega}C$ and $A+\bar{\omega}B+\omega C$ are also factors.
This argument exploits divisibility properties and inherent symmetry. It is generalized by the first proof (using matrix operations) mentioned in my other answer to compute $\Phi(G)$ for $G$ abelian.
Comment: Beautiful answer.  I guess by "etc." you mean $f(\omega A,B,\bar\omega C)$ $ etc.$
Answer: HINT:
If $A+Bw+Cw^2=0$ where $w$ is one of the three cube roots of unity
$\implies -A=Bw+Cw^2$
Cubing we get, $(-A)^3=(Bw+Cw^2)^3$
$\implies  -A^3=B^3w^3+C^3w^6+3\cdot Bw\cdot Cw^2(Bw+Cw^2)=B^3+C^3+3BC(-A)$
$\implies A+Bw+Cw^2$ is a factor of $A^3+B^3+C^3-3ABC$
Answer: You can consider it as a polynomial in $A$ and attempt to factor it. So you want to find polynomials in $B$ and $C$, say $r,s,t$, such that
$$(A + r)(A+s)(A+t)=A^3-A(3BC)+B^3+C^3.$$
In particular, you need $r+s+t=0$, and you similarly have information about $rs+st+tr$ and $rst$. It's not hard to see that the roots are linear polynomials in $B$ and $C$, so they have the form $a+bB+cC$ for a constant $a$. You can plug this representation into the three equations you got from looking at the coefficients and solve.
If you need help getting started on the resulting equations, note that $rst$ has no constant term, so at least one of the roots has no constant term.
Answer: This is a $3\times3$ circulant determinant which is a special case of a group determinant ($G=C_3$).
Let $\{X_g\}$ be a set of formal variables indexed by elements of a group $G$, then $\Phi(G):=\det(X_{gh^{-1}})$ we define to be the group determinant. KCd has a set of notes concerning these objects in the history of representation theory, and includes two proofs of the factorization
$$\Phi(G)=\prod_{\chi\in\widehat{G}}\left[\sum_{g\in G}\chi(g)X_g\right]$$
for finite abelian groups $G$. The first proof shows each linear factor divides $\Phi(G)$ by invoking matrix row operations, the other exhibits the factors as eigenvalues of a linear transformation.
More generally invoking the Wedderburn decomposition yields for arbitrary finite $G$
$$\Phi(G)=\prod_{\rho~\rm irred}\det\left(\sum_{g\in G}X_g\rho(g)\right)^{\deg\rho}. $$
Answer: $(a^3+b^3+c^3) = (a+b+c)(a^2 +b^2+c^2-ab-bc-ac)$

$1+\omega + \omega^2 = 0 \implies \omega+\omega^2 = -1$

$= (a+b+c)(a^2 + b^2 + c^2 +ab(\omega+\omega^2)+bc(\omega+\omega^2)+ac(\omega+\omega^2)) = (a+b+c)(a(a+b\omega^2+c\omega)+b\omega(a+b\omega^2+ c\omega)+ c\omega^2 (a+ \dfrac b\omega+c\omega)$
Now, note that $\dfrac{1}{\omega}= \omega^2$
And after substituting this we get the desired identity.
Answer: Expanding on Potato's answer:
First lets make $a^3 + b^3 + c^3 -3abc\ $ a polynomial in $a$ so we get $a^3 - a3bc + b^3 + c^3$. This has $3$ roots so lets express it as $(a+p)(a+q)(a+r)$. But also know: $$a^3 + b^3 + c^3 -3abc = (a+b+c)(a^2 + b^2 + c^2 -ab -bc - ac)$$
Therefore lets say $p=b+c$. So our polynomial is now: $(a+q)(a+r)(a+b+c)$. Expanding this expression and equating the co-efficients of $a$ we get the following equations:
$$r+q + b+c = 0 $$
$$qr+br+bq+cr+cq = -3bc$$
$$bqr + cqr = b^3 + c^3$$
Doing sum of roots on the third equation we can get:
$$qr = b^2 - bc +c^2$$
subbing the this equation into the second equation we get:
$$(b+c)^2 + br+bq+cr+cq = 0$$
$$(b+c)^2 = -(b+c)(q+r)$$
$$b+c = -(q+r)$$
Now, since $b+c$ is real and lets assume $q$ and $r$ are complex, this means $r$ is the conjugate of $q$. So let $q=x+yi$. Therefore we get:
$$-2x = b+c$$
$$qr = |q|^2 = x^2+y^2 = b^2+c^2-bc$$
So we have $x = -(b+c)/2$ and substituting this in the above equation we get $y = \frac{\sqrt{3}}{2}(b-c)$.
This means:
$$q= -\frac{b+c}{2} + \frac{\sqrt{3}}{2}(b-c)i$$
$$ = -\frac{b}{2} + \frac{\sqrt{3}}{2}bi + -\frac{c}{2} - \frac{\sqrt{3}}{2}ci$$
$$ = bw^2 + cw$$
where w is the complex cubic root of unity. Hence this means that:
$$ r = cw^2 + bw$$
Therefore:
$$a^3 + b^3 + c^3 -3abc = (a+b+c)(a+  bw + cw^2)(a+bw^2 + cw)$$


How to logout and signin with another facebook account

Question: I use the facebook app's SingleSignOn dialog to login, but I can't clear the cache of the facebook app.
So when I try to use another facebook account to login, it will login automatically with the previous account.
What can I do ?
public String logout(Context context) throws MalformedURLException, IOException {
    Util.clearCookies(context);
    Bundle b = new Bundle();
    b.putString("method", "auth.expireSession");
    String response = request(b);
    setAccessToken(null);
    setAccessExpires(0);
    return response;
}

Answer: You have to use AsyncRunner.logout() method. Take a look at example.


Can Kohanim live in a condo or apartment building?

Question: Asking the question because if there is a Jewish person living in the same building that dies in the building, couldn't this pose a problem for a Kohen being under the same roof?
Comment: How is this different from a Kohein having a roommate or ever being in the same room as anyone else (aside from nuclear relatives)?
Comment: Unless the building houses a morgue, why would you assume there's a dead body in it? And even if it did house a morgue, why would you assume it had Jewish bodies in it? While a Kohen is not allowed to touch a body of a non-Jew, it doesn't cause Tumah to spread through the whole building.
Comment: While i agree with @Salmononius2 that it's rather unlikely for a dead body to be in a random apartment building at any given time, or should be noted that Tumah can spread through a building via the concept of ohel
Comment: @Salmononius2 Actually, the Shulchan Arukh (YD 372:2) says a Kohein should not be in the same building as a dead non-Jew.
Comment: It seems from the Kitzur [סימן רב - הלכות טמאת כהן](http://www.toratemetfreeware.com/online/f_00561.html#HtmpReportNum0201_L2) that there's no prohibition to live there, but if somebody dies he needs to get out, fast. Could be an issue even of a non-Jew dies, according to some opinions. (ibid).
Answer: While a Cohen must be fastidious regarding ritual purity, there are discrete limits to how far we require them to go. Generally, we prohibit them from engaging in activities in which contact with tumas meis would be inevitable (see discussions on a Cohen attending medical school). There is no inevitability to someone dying in their apartment building.
Furthermore, the major principle is "derech tumah latzeis, vi'ayn darko lehikanes." While the body may be taken out the front door of the building (thus turning the common area into an ohel), it would not enter the apartment of the Cohen. Therefore, he would only become impure if he was WITH the person who died, or happened to be standing in the hallway between the point of death and the removal of the body. The former he is exempt entirely, and for the latter, just advise him to wait until the ambulance leaves. So there is no need for a general concern of tumas meis in an apartment building.
Comment: @DannySchoemann Not quite - all the examples given are about the Kohen and a KNOWN source of tumah - and si'if vav actually describes my point precisely: הֲלָכָה לְמֹשֶׁה מִסִּינַי הִיא שֶׁהַפֶּתַח אֲשֶׁר עֲתִידִים לְהוֹצִיא דֶרֶךְ שָׁם אֶת הַמֵּת מִן הָאֹהֶל אֲשֶׁר הוּא שָׁם, שֶׁעַל יְדֵי הוֹצָאָה זֹאת יִטְהַר הָאֹהֶל, אַף עַל פִּי שֶׁהַפֶּתַח הַזֶּה הוּא סָתוּם, מִכָּל מָקוֹם נִדּוֹן כְּאִלּוּ הוּא פָתוּחַ So the front door, or whatever designated opening the meis will be taken out, preserves the other rooms from tumah. And once it's out you're in the clear.
Comment: @DannySchoemann Nonsense to you! Tumah spreads through the ohel ONLY IF there is an existing opening CURRENTLY OPEN between the two domains. In old times, most rooms in the same house weren't "sealed off" the way they are now (no doors between rooms, walls not reaching the ceiling, etc.). If the window/door is closed, a meis under the awning outside does spread tumah INSIDE the house. The door as a luach that seals the entrance definitively stops the spread of tumah to the inside of the room. Reread Ohalos.
Answer: My great-grandfather z"l lived in an apartment building in Warsaw and his custom was to leave the building for 7 days when someone died.
Comment: While very cool if true, that doesn't seem to make any sense Halachically. Was he worried that they kept the dead person around in the building for the whole week?
Comment: Was he a kohen?
Comment: Welcome to Mi Yodeya, Menachem!  Do you know anything about why your great-grandfather did this?  Had he been told to, was he stringent just in case, something else?  Do you happen to know if that was the custom in his community or if this was a personal custom?  Any further information that you can [edit] into your answer will help.  Thanks, and I hope to see you around the site.
Comment: In Antwerp the houses are built attached one to the other around the block. Plus the roof's  of the houses even if it's not the same height it is above or below one another that considers the whole block as one roof. And if shabbos there is a nifter the kohanim don't go in to the houses on that block. It happened more than one time. They don't go in to the houses/ apartments till the nifter is taken out after shabbos.


Why bittorent needs many ports

Question: Why bittorrent needs as many ports?..Why not just one-2? I know that some of them are used for peer discovery, but dont exactly know how is this happening. Can you please provide more technical information about how bittorent works(deeper than its described in wikipedia)?
Comment: [citation needed]
Answer: Google says:

"A BitTorrent client normally associates the TCP port number 6881.
  However, if this port is busy for some reason, the client will instead
  try successively higher ports (6882, 6883, and so on up to a limit of
  6999). In order for outside BitTorrent clients to reach this one, they
  must be able to connect to the correct port."

Here is the specification incase you were curious, http://wiki.theory.org/BitTorrentSpecification
Comment: My BitTorrent client doesn't.
Comment: I don't think he's asking about the port the server is listening on. I think he's asking about the ports used by the connections.
Comment: @David Schwartz and you are right...Sorry for my bad question construction.
Answer: BitTorrent needs many ports because it makes many outbound connections. Typical operating systems (including Windows, Linux, and most others) only permit a single outbound connection per local port per IP address. All of your inbound connections will use the same local port. But each outbound connection will be assigned a random local port by the operating system.
Your outbound connections will have the remote port that the other client is listening on. Your inbound connections will have essentially random remote ports, since they are allocated by the remote operating system effectively randomly.
Typically, a TCP connection only has a well-known port on the receiving side. BitTorrent is not an exception to the usual rule. Most likely it only seems unusual to you because you're not used to having a large number of inbound connections. Also, some people specifically change their BitTorrent server port, and you have to connect to them on whatever port they happen to be using, whether it's the well-known normal port (6881) or not.

Why bittorent needs many ports


Why the force is changing when I press something, if $a=0$?

Question: As the second Newton's law says $F=ma$. Why the force is increases, when I press something, if $a=0$?
Comment: Fhe $F$ in $F=ma$.  Is the **net force**.  If there is no acceleration it is because some other force, opposing the motion, is increasing at the same time.
Comment: @M.Enns, "net force"? What does it mean? I've finded a link
Comment: @M.Enns, so the other force is the electromagnetism?
Comment: The net force is the vector sum of all the forces acting on an object.  Say you are pressing a book down onto a table, the net force would be the sum of the force you apply plus the force of gravity on the book plus the normal force of the table acting upwards on the book.
Answer: The Newton's second law states that the net force is equal to the product of mass and acceleration.
I believe you are referring to the force of static friction which is Ffriction = $\mu$*FNormal

Until the applied force exceeds the value of the static friction the body remains at rest.
Comment: I almost understand, but one more question. There is a heavy ball. If I touch it, it wouldn't move, but if I touch it stronger, it will moves. As I understood, static friction force acts on it so it doesn't move by itself. So why it going to move when I touching it with specific force(not knocking, not punching, just touch and press, speed and accelerate is zero)?
Comment: To the OP: The thing is that some forces have the ability of "adjusting". They can "adjust" to equal and balance out an opposing force. Such "adjusting" forces are for example static friction and the normal force. But they all have a limit. That is what the last graph in the answer here shows. When that limit is overcome, the force gives up and let's go.


Service Broker to Send Messages Specific Database bases based on critiera

Question: In Message Broker can you configure to use one queue but based on criteria send to a different Databases or is it a one to one relationship? I am tryibg to figure out if I should use Message broker or SSIS package.
Answer: Service Broker conversations are between services, not between queues. You send from a service, to a service. A conversation is tied to exactly a pair of services and cannot change. The same service can participate in any number conversations, with any number of peer services. If you want to send messages to multiple peers, you need to start multiple conversations.
Answer: The Service Broker simply acts as a messaging queue for the different Database Mail Profiles you have configured on the server.  If you plan to reuse a mail configuration, then Database Mail is the way to go.  Otherwise, the Send Mail task in SSIS will provide a more customized benefit.


Do "progressive waves" need a medium for their propagation?Can they be produced in vacuum

Question: Progressive waves are those waves which transmit energy from one point to another point .They have two types of waves; transverse waves and longitudinal waves. And transverse waves have further ,mechanical transverse waves( water waves) and electromagnetic transverse waves (light waves.)But longitudinal waves have only mechanical longitudinal waves(sound waves) and no electromagnetic longitudinal waves Can we conclude from this that ;progressive waves need a medium for their propagation as longitudinal waves have no electromagnetic waves?
Comment: I'm not sure if this is a point of confusion, but transverse waves can definitely still transmit energy.
Comment: Note: if the photon has a mass (currently $m_{\gamma} < 10^{-18}\, $eV), then there are longitudinal EM waves in vacuum.
Answer: Let's untangle the question a little bit:
Progressive waves are waves, that transmit energy from one point in space and time to another point in space and time. There are different types (longitudal/transverse), but the fundamental property, that distinguishes progressive waves from different waves, is the energy transfer.
So if the question is 'can electromagnetic waves be progressive waves', we have to check, if they can transfer energy. The answer to that question is: Yes! Even in vacuum, electromagnetic waves have an energy flux, that is described by the Poynting vector $S$
$S = E \times H$
with the usual electric field $E$ and magnetic field $H$. Mind, that this is not the magnetic induction $B$, but the two are closely related.
Even though you are right, that electromagnetic waves are purely transverse in vacuum, this does not stop the wave to carry energy with it. But in materials, there are even longitudal components to the wave.
If you want to have experimental evidence for this, there are two easy ways to check. The first is to set up a black body in vacuum and illuminate it with a focused beam of light. Over time it will get hotter, so there needs to be some energy transfer happening. The other way is on a much larger scale: our earth, as it is radiated on by the sun. Between the earth and the sun is approximately vacuum, so energy needs to be transferred through that, otherwise it would be very cold on our home planet.
In conclusion, progressive waves do not need a medium for their propagation. Electromagnetic waves in vacuum do not have a medium they exist in and still transmit energy, so they are progressive.
Comment: I can't get it clearly Please tell me in a yes or no
Comment: Please tell me what is unclear. Your question is hard to understand, because you mix up several concepts, this way I don't know what exactly to say 'yes' or 'no' to.
Comment: The question is basically that ;Do progressive waves need a medium for their propagation?
Comment: Ok, I will expand the answer accordingly. But please try to understand the reasoning as well
Comment: Ah! I got it now from your last paragraph.
Comment: Ok good to hear :-). Then please accept the answer after about a day, so other people have a chance to post an answer as well.
Comment: Ok ,and  thanks by the way ,you provided me  the same answer which I was thinking right


Are these topological invariant sets?

Question: Is being $T_1$ is a topological invariant?
Is being a first-countable space is a topological invariant?
I need a little hint as to whether or not these sets are topological invariants.
Comment: Suppose $X$ is T$_1$ and $f:X\to Y$ is a homeomorphism. Can you show $Y$ is T$_1$?  Repeat for $X$ first countable.
Comment: By "be first accounting space", do you mean "being a first-countable space"? If so, yes, first countability is a topological invariant. Here is a list: http://en.wikipedia.org/wiki/Topological_property
Answer: A toplogical invariant is a property that is preserved under homeomorphism.  So your first question is equivalent to:

If $X$ and $Y$ are homeomorphic, and $X$ is $T_1$, is $Y$ also $T_1$?

Let $f\colon Y \to X$ be a homeomorphism.  Given that $X$ is $T_1$, and $f$ is continuous and invertible, can you show $Y$ is $T_1$?
Answer: Let $X$ be $T_{1}$. Let $f:X\rightarrow Y$ be a homeomorphism. This tells us that $f$ is an open mapping (i.e., open sets map to open sets). Let $x,y ∈ X$, and let $B$ be an open set  containing $x$ but not $y$. Since, $f$ is an open map, then $f(B)$ will be an open set in $Y$. Can we be certain that the open set $f(B)$ contains $f(x)$ but does not contain $f(y)$? If so, then it follows that $Y$ is also a $T_{1}$ space, and thus topologically invariant.
Secondly, regarding first-countable spaces, let $X$ be a first-countable space, and let $x$ be any element of $X$. Then $x$ has a countable neighborhood basis. Since $f$ is an open (closed) map, it will map every open (closed) neighborhood around $x$ (in $X$) to one around $f(x)$ (in $Y$). Thus, it follows that $f(x)$ has a countable neighborhood basis, and thus $Y$ is first-countable.

Are these topological invariant sets?


Is it possible to say "hold the silence"?

Question: I have to write a formal essay about environmental issues. I want to write a sentence: "I can no longer hold the silence about this problem". Is it possible to say this? Or its better to say something like maintain/remain/keep my silence? Which one sounds more formal?
Answer: The idiomatic expression "keep silent" is already common:

I can no longer keep silent about this problem.

This is fine to use in your essay.  Style guides do suggest you avoid using the personal pronoun "I" in formal essays, as it's redundant because the reader already knows it represents your personal opinion.  It may be better to write it as a general recommendation for all of humanity:

We can no longer keep silent about this problem.

In more creative writing, you can say anything you want, and there's nothing wrong with "hold the silence", when placed in a context where it makes sense.  The nuance it somewhat different and means "be silent" rather than "keep silent".  It's something I might say when teaching mediation:

As you begin to focus inward, learn to hold the silence within you, calming your thoughts and letting your breath move in and out like the waves of the ocean.

If I wanted to use it as a creative variation on "keep silent", I would probably use "maintain" rather than "hold", and use a personal pronoun.

The fury rose within her, threatening to overcome her natural decorum.  She could no longer maintain her silence about the problem -- she wanted to rage and scream and break everything that would satisfyingly shatter when thrown against the wall.
Comment: "Hold my tongue" is another common expression meaning the same thing.


Reducing capacitance of a wire

Question: Given a wire and a piece of foil wired to a bread board, is it possible using capacitors wired in series (or some other method) to significantly reduce the capacitance of the wire/foil?
Comment: If I've got the right mental picture of what you're doing, you have two choices: reduce the size of the foil, and move all other conductors further away from your wire and foil.
Comment: A photo of what you have now might help us understand your problem.
Comment: Do you need to reduce the DC capacitance or the AC capacitance?
Comment: :( I don't know. I have a capacitance sensor, I'm trying to reduce the value on it.
Comment: I believe DC...
Comment: A distinction between "the DC capacitance or the AC capacitance" makes no sense at all.
Answer: I'm not 100% sure I understand your needs, but you might consider a negative capacitance amplifier, as in http://en.wikipedia.org/wiki/Negative_impedance_converter, whose parallel negative input impedance should subtract that of your wire.  This is a positive feedback trick, so if your negative capacitance is too high, your system will go unstable.
This is used all the time in neuroscience to deal with large capacitances in glass microelectrodes, but I've never seen it used for cable capacitance.
Answer: I've used double screened cable. The inner core signal is applied to a unity gain amplifier which projects back the same voltage onto the 1st (inner screen). This means that the inner core "sees" a capacitance that is vastly reduced. The outer screen is used as ground and of course the inner screen "sees" all the ground capacitance.
I've used this on a capacitance probe too.
Things that make it go wrong - long wires where the frequency used has a wavelength that approaches (maybe) 100th of the cable length. Significant attenuation down the cable (losses) means it isn't as effective.
Use high impedance inputs on your actual cap-probe input and the non-inverting screen driver input.
Comment: Not quite "doesn't see any capacitance", but rather "reduces current caused by the cable capacitance".  If i=CdV/dt, then one can reduce the current by reducing C, or by reducing dV/dt.  Double shielded cable with an amp driving the inner shield at the common mode voltage achieves the latter.
Comment: I think you meant to say " Inner screen" here " ...the inner core sees all the ground capacitance."

Reducing capacitance of a wire


I'm trying to acces an item from my database in WP7 and output it

Question: I have made a database for my application and it uses an sdf database. When I query the database and put it in an ObservableCollection I get the information but how do I access the elements within? Any help?
var mathItemsInDB = from Math_Info math in mathDB.Math_Information
                            where math.mathID == 0 select math;

        Math_Info_Items = new ObservableCollection<Math_Info>(mathItemsInDB);

        base.OnNavigatedTo(e);
    }

    private void displayProblem()
    {
        //here i would like to display the mathproblem fetched from the db and not an already created array
        this.MathProblem.Text = mathProblems[problemNumber];    //displays the mathproblem/equation
    }

Answer: I have not tried it but mathProblems.ElementAt()?


How to create a random pacman maze

Question: Hello I have been working on an algorithm to generate a random pacman maze. I have seen a couple of articles but could not break down the logic. I am using the maze algorithm depth first search and then I mirror the maze to make each maze symetrical. I am running into issues like cleaning up the dead ends. If this is not possible I would also attempt another algorithm if anyone has their own logic to generate the random maze. Any help is appreciated. Thanks
Comment: I know this is an old question but check out this site if you're having problems, it helped me a ton. http://www.contralogic.com/2d-pac-man-style-maze-generation/
Comment: What do you mean by "pacman maze"?
Comment: I am attempting to make my own pacman clone and I would like to create a "pacman maze" similar to this picture  http://ryangenno.tripod.com/images/MSpacmaze4.gif. I would like to generate this at random
Answer: I solved my problem and wanted to share. For starters I set the top row and first column and last column as a wall obstacle then I set a path on the second column, second to last row and second row so it surrounds the outer wall. Also keep in mind I am only creating 50% of the maze so when I am done I copy the maze so both sides are equal. Then I created a middle section surrounded by a wall for the area where the ghosts spawn. Then any part of the maze that hasn't been looked at I generated paths using the depth first search algorithm. After this was done I know that in a pacman maze there are no dead ends. What I did was check every cell that is part of the path that pacman can travel. If any cell has only 1 bordering cell then it is a dead end. If it is a dead end see if it can be connected to another path. If not set the dead end as a wall and check the maze again for any dead ends. After you follow these steps you will have a random maze with no dead ends that resembles the typical pacman maze.
Answer: I'd offer to do a random walk by dfs in the clean area (without any wall, in n*n matrix of 0's), after that fill the areas which are not covered by random walk (make them as wall), this also could cause to unused spaces, but this guarantee to have a long walk. you could set the size of walk arbitrary (e.g when your walk size arrived to (n^2)/2, you could stop the walk).
Answer: I created a random PacMan maze generator a long time ago on the C=64 using the depth first and elimination of dead-ends, but recently got challenged by my friend to do it again. Found a better way. Check it out at my site
Essentially, I created a grid of rooms with each direction having an open door (closed on the border except where the tunnel goes), then start closing the doors randomly according to the rule that there should never be more than 1 closed door in an adjacent room if 2 doors are closed, a third one would create a dead end. Just keep doing this randomly until all the potential door are either closed or open by the rule.
Mirroring was a bit more work, but I started with the basics and just built up the rules to allow for mirroring, ghost house location, minimum wall length (no single walled roundabouts) and maximum wall length, etc...
Comment: The link is now dead
Comment: Apparently, you tried to update your answer using a different user account, and the [suggested edit](http://stackoverflow.com/review/suggested-edits/1287465) was rejected. Why not using your original account?

How to create a random pacman maze


Why heat is also produced when electron hit a material rather than producing only light?

Question: I mean atoms are mostly electron clouds . So , all electron that hit a material should be taken up by the electrons of atom and the energy be used up by the electrons to go to a higher orbital and then eventually producing photons on going back to lower energy . How does some electron's energy  convert into heat energy ?
Answer: The thermal energy is simply energy randomly distributed in a sufficiently uniform manner among the many degrees of freedom of some large system as result of many interactions. Any energy pumped to the system may become thermal provided that it is transmitted to other degrees of freedom sufficiently well.
When electron hits the atom part it not only excites it but also gives it as a whole some velocity. This kinetic energy may be transmitted to other atoms through collisions just like in the ideal gas. During those collisions the energy of electrons in excited state may be transmitted to the electrons of other atom. Finally the photons produced by excited atom may be absorbed by other atoms instead of flying away. This distributes the energy obtained by a single atom among all the atoms in the material and raises thermal energy.


Notes in a Chord

Question: I'm trying to work my way through the Mark Levine Jazz Theory book but I'm scratching my head at the start of chapter 2 (Pg15). Maybe this book is too advanced for me and I need to pick something less Jazzy. A stave in the first example shows the notes F,Ab,Eb,G with the Chord F-7 written above it. I can't fit these notes into the chord, I would have expected to see F, Ab, C, Eb. In the next bar it names the chord as Bb7 with the notes below Bb,Ab,C,E,G. Again I would have expected to see Bb,D,F,Ab. Can somebody help and explain how or why these notes appear ?
Comment: You're correct about the basic spelling of those chords. It seems like there might be some additional context needed. Could you post images? The title of the chapter could shed some light as well.
Comment: There are so many discrepancies in this book, I gave up on it. As an educational tome, it isn't. Try Bert Ligon instead.
Answer: In a book on chords we might expect the labelled chord to be played exactly as the chord symbol indicates, but this book is more about how a musician may approach the basic chord chart and embellish upon it creatively. Essentially, when a musician playing in a jazz context sees a chord, they will very often put their own substitute voicing on top that has a few more of the interesting extensions in it. In the Mark Levine book, he is concerned with showing the underlying chord progression as it may appear in a Realbook or leadsheet, and displaying it alongside what a musician may actually play. The chord charts as written in jazz lead sheets are fairly rough simplifications, giving the improvising musician a good clue as to what that chord is 'doing' in the piece of music, and leaving the space open for them to extend it in a way that suits them, and suits the stylistic sensibilities of the current group they are playing in.
In the example fig 2-1, we are seeing a ii V I progression in Eb.
F, Ab, Eb, and G are the intervals 1, b3, b7, 9, a minor9 chord, a common extension of the minor7 chord in the ii position. The 5th is omitted, but it doesn't effect the naming of the chord, the 5th is very often the first to be omitted from a voicing as it serves no strong purpose in defining the FUNCTION of the chord (here, at least).
Bb, Ab, C, D (not E), G are the intervals 1, b7, 9, 3, 13. A dominant13 chord, again, a common extension of a standard dominant7 chord in the V position. Note, you can generally add any upper extensions below the 'highest' extension you get. Ie in a 13 you can happily add all the extensions up to the 13th, there are some caveats and rules to that but perhaps thats not for right now, you'l come to them in time!
Edit, looking again at the example I would agree with Pied Piper that actually the Bb's 13th (the G) is better thought of as a suspension, in this context, as it is part of the melodic line on top and quickly resolves to F within the second measure!
Musicians playing jazz (depending on their personal choice and sound) will generally extend most chords in one way or another to get a more interesting or complex sounding harmony. Mark Levine is showing the underlying changes (the chord symbols) in such a way that their function can be easily seen, alongside a transcription of how someone may choose to actually play them.
This may seem a little complex for the learner, but it's not so bad. The underlying quality of the chord will be held in it's 3rds and 7ths, generally.
1st, 3rd and 7th - some kind of major7
1st, b3rd and b7th - some kind of minor7
1st, 3rd and b7th - some kind of dominant7
The extensions, in the example you asked about, are chosen from the other notes available from the scale, Ebmaj in this case. The ii chord naturally has a natural 9 so it has been added, the V chord has a natural 9 and 13 in the key of Ebmajor so they too have been added. These extensions are said to be diatonic to the key, ie. they are the ones we would expect.
Worth noting, playing extensions that are NOT from the key is very common, in order to create tension or other effects. But this is something to look at later perhaps, and IIRC in this book Mark Levine introduces the learner to these extensions as they come up.
Comment: Thank you so much for your answer. It's made it a lot clearer but maybe I'm trying to run before i can walk with this book. Do you know of any other books I could try before the Levine book ?
Comment: No worries! Hmm, it's a bit tricky as I tend to teach learners to a certain point in-classroom and then once they've got a good foundation I direct them off towards the various books, Mark Levine etc. once they are ready, making sure I warn against the pitfalls that some of these books have (including the Mark Levine one) and work with them with these new findings. Whats your instrument? I can have a look around for some good ones that stick to the fundamentals!
Comment: I play guitar and it was an online guitar instructor, Tom Quayle that suggested buying the Mark Levine book in his course 'Jazz Harmony - Playing Changes'. The book tells you in the introduction that you don't need to be able to play piano but it's a struggle when the first set of examples it gives you (as you've now explained) have extensions and voicings I wasn't expecting. I'll try and stick with it for now and struggle through it, I might end up being a better pianist than guitarist. Thank you again for you're help.
Comment: Ah I see! Yeah, the examples will be annoying to play on guitar. I'm bass but when reading this book I plodded through on piano, many of the voicings will not be playable on guitar anyway! This is a slightly contentious book, the scale for every chord approach is not the way the great jazz giants would have thought, but the book talks as if it's 'the only way'. Its good for a more modern sound though, I would just read and take bits from it as you go and not worry TOO much about the examples, maybe play on a keyboard if in doubt!
Comment: I agree though, its a bit annoying when the first example chucks in a concept the author hasn't even thought to mention. The Bert Ligon books are suggested above, I haven't read it but had a look at it just now and it may well be a more concise alternative!
Comment: Ok, I am trying to work through it using a piano but the chord extensions threw me until you explained it. I'll struggle on and if it gets too much I'll put it back on the shelf ( or ebay) and try something else. Again thanks for your help, I'll probably need it again.
Comment: Feel free, in the absence of my NORMAL life, playing this stuff each evening with other musicians who express these ideas with a mastery that I can't comprehend, chatting about it on social media is a very welcome substitute!
Answer: In the first bar the melody note is G, so this is really a Fm9 chord. Leaving out the fifth (C) doesn't change the quality of the chord.
In the second bar the notes are Bb, Ab, C, D (not E), G. The G is just a suspension from the previous bar and resolves to F. It's really a Bb9 chord.
Comment: So, in what's supposed to be an educational book, why does Levine frequently call the chords by inaccurate names, with no text explanations to help the sort of people who would try to use a book such as this to expand their playing? As I read the book, I made notes of so many places that lacked relevant information - I can't recommend this book enough - to leave on the shelf!
Comment: @Tim I wasn't trying to defend the book. I agree with you, it's not explained properly.
Comment: Not knocking your answer, just knocking the book. So many 'mistakes'...
Comment: Melody notes can be part of a piece's functional chord structure, but they don't have to be.  The same can sometimes be true of certain "color" notes in an accompaniment.  In some contexts, omitting a 7th or 9th of a chord, or replacing it with the root, may fundamentally change the way it sounds, while in others such a substitution might be barely noticeable.  If a piece has a chord with C, E, and Bb, while a melody note hits a B natural that will resolve up to C while the chord notes underneath resolve to C, F, and A, I'd classify that as a C7 despite the presence of a B natural.

Notes in a Chord


What is the origin of the noun "satellite town"?

Question: A satellite town is a town that is located in the outskirts of a major city. What is the origin of this name, satellite town? What does "satellite" exactly mean here?
Answer: At OED.com* the 6th noun definition of satellite is firstly of a state (country, principality, etc.,) that is politically or economically dependant on and subservient to another. Their earliest quote:

[1776   T. Paine Wks. (1796) II. 24   In no instance hath nature made the satellite larger than its primary planet; and as England and America‥reverse the common order of nature, it is evident that they belong to different systems: England to Europe, America to itself.]

As you can see, satellite is being used in a metaphorical sense, so the origin is the astronomical definition of satellite. The meaning of satellite with regards to towns being:

A community or town that is economically or otherwise dependent on a nearby larger town or city.

Which you can see is parallel to the definition for states.
* OED.com requires a subscription, which might be provided by your library. Try your library card number to find out.
Comment: N.B. of course it isn't the *earliest* quote that is necessarily very interesting, but rather quotes of the early 1900s (when "satellite town" appears to have been coined). Though... taking usage from that time, I think you arrive at the same conclusion :)
Comment: The OED has an entry for *satellite town*, first is from 1925.
Answer: In space, a satellite is something that orbits (or goes around) something else.  Usually the smaller object orbits the bigger one.
Geographically, then, a satellite town is a community located near a big city.  Typically, there is some "attachment" between the satellite town and the nearby city (for example, a large percentage of the workers in the satellite town are employed in the city).
Comment: Well, technically both always orbit each other.  :)
Comment: @vsz: Maybe we should migrate this to Physics.SE? :^)
Answer: Well, a "satellite" of a planet is an object in its orbit. As far as I'm aware, it's simply an analogy on that. Doing a quick unscientific Google Books search and looking at how "satellite" appears to be predominantly used in the 19th and early 20th century ("satellite town" appears to have been coined in the 1910s/1920s), this would seem to be how speakers have always conceived of the term.
It is true that "satellite" is occasionally used in other contexts to mean "adjoining"/"accompanying", e.g. the term "satellite vein", which apparently predates "satellite town" by some decades, but this usage appears to have been marginal compared to the use of "satellite" in the planetary context.
Comment: A planet's "satellite" is itself an 'analogy'.
Comment: Kris -- I suspect that nowadays that's not the case and that the word has evolved so that the planetary context is the main meaning. However, it's interesting to note that etymologically, the word has come 'full circle'.
Comment: Have you heard of the cronies hanging around a political lightweight being called 'satellites'? This usage has been around for ages.  Plus, the term has been in use in an 'analogous' sense in many specialized fields as much as in astronomy -- only not as popularly known.  I know of engg & medical terms.
Answer: 'Satellite' simply means a 'follower' -- a smaller object or person following a bigger one.
[http://www.etymonline.com/index.php?term=satellite]
1540s, "follower or attendant of a superior person," from M.Fr.satellite (14c), from L. satellitem (nom. satelles) "attendant" ...
The term was used in the astronomical sense by Kepler in the 1610s.
By extension, a thing dependent, and typically found around, a larger one of its like is a satellite.
Comment: As I say in my other comment, this is an interesting observation from a historical viewpoint. But it doesn't reflect the meaning of "satellite" in 2012.
Comment: And looking at usage of "satellite" in the decades leading up to "satellite town" being coined, the use to mean "attendant" doesn't appear to have been common at all-- the planetary use had apparently already supplanted it by a long way.
Answer: It is taken from the Sanskrit word Sathiya, which means follower. The French spelled it their way from Sanskrit/Hindi.
Comment: This does not answer the question as currently written. Adding some detail as to how the word "satellite" led to the term "satellite town" would fix that.


When do you unlock overwatch function in CSGO?

Question: The question is simple, how many competitive matches do you need to unlock overwatch function in CSGO? Or what range do you need to be to unlock this function?
Answer: There is no set number of games or objectives to complete, to get Overwatch access. According to the wiki:

Investigators are selected based on their CS:GO activity (competitive
  wins, account age, hours played, Skill Group, low report count, etc.)

Basically the older your steam account is, and the higher your in-game rank, with high percent accurate reports, then you have a pretty good chance to get selected, as long as you haven't been correctly reported (say griefing or scripting)
Though my steam is not that old (don't even have the 5 year badge) and my rank was mid level when I got it, so I believe the most important thing is accurate in-game reports of actual cheaters (or griefers/scripters) you encounter.
Answer: It's technically not defined by Valve but many users have said they unlocked it around Master Guardian range and immediately when they hit 150 wins. I was Master Guardian and didn't have it unlocked, presumably because I had only like 70 wins or something. One friend had around 300 wins when it came out and didn't unlock it till about 350. So there really isn't a defined range, it's kinda random.
Answer: After you get 150 competitive wins, you are eligible for overwatch
Comment: This answer adds nothing that was not already stated in previous answers.
Comment: There is no set numbers, as stated from the answer above


Visa requirement with a residence permit from Greece

Question: I am of Turkish nationality and have a residence permit from Greece. If I fly from Turkey directly to Germany, do I need a visa?
Answer: No.  Your residence permit from a Schengen country allows you to travel to other Schengen countries for up to 90 days in any 180-day period.  See Travel Documents for non-EU Nationals:

If you have a valid residence permit from one of those Schengen countries, it is equivalent to a visa.