Can I use a different image input size for transfer learning?

Question: Most pre-trained CNN models accept a $224x224$ input size when they were trained. Can I use $256x256$ to get a higher accuracy?
Answer: If you change the image size, you will be able to reuse only part of the original network.
Convolutional and pooling layers can be applied to images of any size, so the initial part of the network, which normally consists of convolutions and pooling, will be reusable as-is.
However, the dense layers after the convolutional part assume certain input dimensions. Therefore, as your larger images lead to larger input to the dense layers, you won't be able to reuse the dense layers.
Comment: can you please explain the answer to this [one](https://stackoverflow.com/questions/65516526/can-you-use-a-different-image-size-during-transfer-learning). Do you agree to it?
Comment: The linked answer is incomplete. If you take a look at the source code link they provide, you will see that the network takes a parameter called "include_top" and only when it is true the network accepts arbitrary shapes. That parameter controls whether you only reuse the convolutional part. This is precisely what I describe in my answer.


Cyclometer synonym for bike-computer?

Question: I don't have anywhere near the rep to propose this directly, but cyclometer seems like a good synonym for bike-computer. It took me a few seconds to realize how I should tag a question I just posted - and if I'd had 300 rep I would've unwittingly created the cyclometer tag instead!
Answer: Good point. Done. cyclometer is now a synonym for bike-computer

Cyclometer synonym for bike-computer?


Should the Chazzan say the pesukim of Kedusho loud?

Question: In the repetition of the Amida, it seems (see Teshuvos Igros Moshe 3 (9), OC 104 (7), OC 125 Biur Halocho d.h. "elo shoskin ..") that the Chazzan should say the pesukim of Kedusho loud enough so that someone who has not yet finished his own Amida can hear them and thereby fulfill his obligation. But some Chazzanim do not, especially on Shabbos and Yom Tov. What sources do they have to rely on?
Comment: I don't think the question is worded fairly. I think a more neutral question would be: "According to ... a Hazzan should recite the verses out loud. Are there any sources that say he should - or may - recite them quietly?"
Comment: I wouldn't say the Biur Halacha concludes so strongly in either direction.
Comment: It's a machloket rishonim if the person in silent amida needs to hear the leader or the congregation to be yotzei https://hebrewbooks.org/pdfpager.aspx?req=66471&st=&pgnum=159 Seemingly the latter group (which is the majority) would justify the practice of the rambam mentioned below.
Answer: In Rambam's text of the siddur (printed after the various laws of prayer, blessings, and the like, in the back of his code), he writes:

The chazan says each one calls the other, and the congregation answers holy holy holy ... the chazan says by David, your holy anointed one, and the congregation replies G-d shall reign forever. And all the parts that the congregation recites, he says along with them. He should not raise his voice while they answer with him.
Answer: I once heard (I do not remember from who) that on Shabbos and Yom Tov since the Davening is done at a slower pace - in general people are holding along with the Chazan - and thus it is unecessary to say the Pesukim out loud.
It is also very possible that the Chazan is saying it out loud, however as there are often more people in Shul on Shabbos/Yom Tov and often they are Davening louder than during the week, it may be hard to hear the Chazzan saying the Pesukim.


Where did the 9 tails of Sora go?

Question: Towards the end of Naruto Shippuden season 4, the 9 tail's chakra left Sora's body and then Yamato said that it will try to seek a new host now. Who was that new host? Did the chakra in Sora come back to Naruto, the real host of the 9 tails?
Answer: Short version: He was just a filler character...
Long version:
Sora appears only in the Twelve Guardian Ninja arc of the anime. In the other arcs of the anime and in the manga he is not mentioned anywhere.
In other words, as readers and viewers of Naruto, we don't know if Nine-Tail's chakra, that left Sora's body, found a new host or did come back to Naruto, the real host of the Nine-Tails.
Links to external resources: Twelve Guardian Ninja (Arc), Sora
Answer: It is very likely that the secondary chakra of the nine tails was returned to the original host's body, that is Naruto. When Yamato says that the chakra of the nine tails is excess and will need to find a new vessel, notice that the camera zooms in on Naruto and therefore could be a subtle hint incorporated within that episode itself.

Where did the 9 tails of Sora go?


How much space NAS snapshots consume?

Question: I am trying to understand how snapshots on NAS work. Let's say that I have a 10GB share on NAS. I create a 1GB file. A daily snapshot is taken. After that I delete the file, but the snapshot remains. How much available space will I have? I assume that it will not let me overwrite the space where the snapshot points so, will I have 9GB of available space remaining?
Comment: it depends on the NAS and the software used. Maybe giving us the make and model and vendor for a start?
Answer: Most NAS snapshots implement copy-on-write, so the snapshot itself initially takes up no space (or next-to-none, there is some overhead).  But any block that is changed whilst the file it's part of is snapshotted must be copied.  If an entire file is deleted whilst it's still in a snapshot, all those blocks must still be kept.
So in your case above, as long as that file is still in a snapshot, you only have 9GB left.  Worse still, if the file is not deleted but completely altered, so that every block is changed, you will only have 8GB left, as 1GB is used up by the file in its current incarnation, and 1GB is used by the original file.  If the file is completely changed every day, and every daily snapshot is kept, you'll run out of space completely before the end of day ten.
Comment: Thank you! Just want to double check. If I create a file and delete it before snapshot is taken, it will not consume any space?
Comment: If creation *and* deletion happen without any intervening snapshots, the file is simply gone, and takes no space.

How much space NAS snapshots consume?


TCP Scans vs SYN Scans in port scanning

Question: What is the difference between TCP Scans and SYN Scans?
Answer: TCP scanning refers on scanning a target network for TCP connections , how you are going to look for the connection defines different techniques. Both Connect Scan and SYN Scan are types of TCP Scans to determine if the probed server has active TCP connections
SYN Scan is a type of TCP scanning where you probe the target network sending SYN packets, at all desired ports , to initiate a three-way handshake . The server will respond with SYN-ACK for every open port and a RST response for closed ones.After that you don't reply to the server to complete the 3-way-handshake and open a connection.
Connect Scan is another type of TCP Scan similar to SYN Scan but this time after receiving a SYN-ACK response from the server you reply with ACK response completing the 3-way-handshake and establishing a connection to the server, which will take more resources and time to complete.
Comment: So they change in a way of scanning. In addition TCP scan (connect scan) uses the OS system call, connect, to check the port status. SYN Scan uses, a packet with SYN bit set to 1, called SYN PACKET, to check the port status.
Comment: just edited my answer
Comment: Note that, depending on the platform, you may need elevated privileges (root) to perform a SYN scan. Also the scans have different profiles that can create different artifacts on the targets.

TCP Scans vs SYN Scans in port scanning


Infinite Sets (real rational integers)

Question: How can the real, integer, and rational number sets be infinite, yet, they aren't all the same size?
Comment: Look up "cardinality" and "cardinal numbers" using google. Also "countable set" would be good, and maybe "Cantor's diagnoan proof." BTW integers, rationals same size in cardinality.
Comment: And [this](http://math.stackexchange.com/questions/18969/why-are-the-reals-uncountable?lq=1), and [this](http://math.stackexchange.com/questions/732/proof-that-the-irrational-numbers-are-uncountable)...
Answer: Because of Cantor's theorem (the diagonal construction).
Given the definitions of what it means for two infinite sets to be of the same size, and of what it means for one set to be at least as large as another, $\Bbb N$ and $\Bbb Q$ are of the same size, because we can prove that there is a bijection between them.
However, Cantor's theorem shows that no 1-1 function $\Bbb N\to \Bbb R$ can exhaust all of $\Bbb R$ — it can't be onto $\Bbb R$, so $\Bbb N$ is strictly smaller than $\Bbb R$.

Infinite Sets (real rational integers)


Can I fit 27x 1 1/4 tires on a 622x14 rim?

Question: I have an old 60s (I believe) Schwinn Suburban that has no tires. I looked up what size tires to get and found 27x 1 1/4 as the match. I just recently scored a set of 622x14 rims. Could I fit the 27x 1 1/4 tires on these rims?
Comment: https://www.sheldonbrown.com/tire-sizing.html
Comment: See also   https://bicycles.stackexchange.com/questions/34543/is-there-any-other-size-tires-that-will-fit-on-a-27-x-1-1-4-rim  and https://bicycles.stackexchange.com/a/63518/19705
Answer: No, not safely.
Bicycle tyre measurements are somewhat nonsensical, and plain unit conversions will not result in useful numbers - 27 1/4 inches is 692 mm which is larger than any common wheel rim.
27" and a fraction, is probably a ETRTO size of 630.
Aside, 27.anything " in a decimal is a separate system and cannot be rewritten as fractions while remaining the same tyre size.   It really is a horrid mess.
The ETRTO number is a good attempt at standardising tyre sizes, and can be directly compared; that is any 622mm rim and tyre should work together, but 622 and 630 is different and won't.  Easy.
Since you have bog-standard 622 rim, go with normal 622mm tyres which are available new.   Even if your existing tyres fit on, they won't lock into the bead securely.

The other half of the question is whether your bike frame would take the 622mm rims - the front dropouts will likely fit, but the rear is probably a different width.  And then there's the issue of making the brake pads reach the rim, and getting the chain to run on the cassette, shifting, etc.
Since you have the bike and wheels, it is probably less work to buy 27 1/4" tyres+tubes, and fit them to the existing wheels.  The range will be small but they do exist.
Comment: That aside, they shouldn't have to find a tube specific to 27" rims, as a 622 tube should fit fine onto a 630 rim. Continental's 28" tubes have a print on them that explicitly says 622/630. I've done this with other inexpensive (3€) tubes as well.
Comment: Where I live, 630 tires and rims are extremely hard to get (and they are both expensive and low-quality), so I understand OP's goals here. The brake pads should be able to adjust some 3 mm lower. The frame is likely steel so cold setting it, or just chucking that 130mm axle in shouldn't present a big issue. I don't see a problem with the chainline and shifting, but even so, adjusting the rear mech is relatively trivial as far as bike maintenance goes.


Does Command Undead last past an undead's death and raising?

Question: If an undead creature fails its save against the Necromancy wizard feature Command Undead, and then dies and is raised or rejuvenated (eg a lich coming back from their phylactery) are they still affected by Command Undead?
Answer: RAW: likely yes
A dead (neither living nor undead) creature is not a "creature", so it is not a valid target for the ability. However, the ability was used when the creature was a valid target, so this is not a problem. As the ability does not say it ends when the creature dies, it doesn't.
This leaves the question of whether a re-raised creature is the same creature as the previous incarnation. Clearly the body is the same, and at least some of the personality is persistent, as most undead know the languages that they knew in life. Of course, what constitutes a single person is a hotly debated philosophical question, so you should feel free to give your own interpretation, but I think most people will conclude that the re-raised creature is indeed the same creature.
What happens to the CHA saving throw?
When a creature with an INT of at least 12 (such as a lich) is targeted by command undead, it is allowed to repeat the saving throw every hour. I cannot find any rules, SE posts or Sage Advice on objects (as that is what a dead creature is) making saving throws. However, the unconscious condition only specifies automatic failure of DEX and STR saving throws, so I would rule that the corpse makes the saving throw with the CHA score it had while alive (or in this case undead). I think you can also make a reasonable case for a corpse having 0 CHA, giving it a -5 on the saving throw.
At the table: ask your DM
I do believe the above answer to be correct according to RAW, but it would certainly not be unreasonable to rule it otherwise. Therefore, if the DM disagrees, whatever they say goes. Incidentally, this is also RAW. From page five of the PHB:

One player, however, takes on the role of the Dungeon Master (DM), the game's lead storyteller and referee.

(emphasis mine)


How do you store "int" values in an NSMutableArray* or NSMutableDictionary*? Chronic problems with JSON data that come in as integers.

Question: How do you store "int" values in an NSMutableArray or NSMutableDictionary?  Chronic problems with JSON data that come in as integers.
Should I try to store these integers as NSNumber objects or just as strings that contain the integer?
How dangerous is it to do a "raw" (int) conversion on the pointers if I know the values will always be Natural Numbers (numbers>=0 including zero for null.)
The integers I'm always working with are Foreign Key Id's from a database.
Answer: Use NSNumber like this:
int yourInt = 5;
[myMutableArray addObject:[NSNumber numberWithInt:yourInt]];

Or using modern Objective C syntax, you can use the following for expressions:
[myMutableArray addObject:@(2 + 3)];

Or for lone numbers:
[myMutableArray addObject:@5];

Answer: Use NSNumber objects (e.g. using [NSNumber numberWithInt:value])
Answer: You need to use NSNumber, as others have said, or use an NSString with the string representaton of the number. It really doesn't matter which, but the NSNumber will be more efficient.
You can't just throw in an int, let it be interpreted as a pointer, and then cast it back on the way out. The reason is that the object (that the int will be interpreted as a pointer to) will be sent the retain message when it is added to the array, and this will definately cause a crash since it will be an invalid pointer.
Answer: You can also use:
[myDict setObject:[NSNumber numberWithInt:anInteger] forKey:@"MyInteger"];

Answer: You can also add value like this
NSMutableArray *values = [NSMutableArray alloc]init];
[values addObject:[NSNumber numberWithInt:23]];


Downloading video from SWF

Question: If I am seeing a SWF video in my web browser (sample: http://www.somename.com/swf/x92154) how can I download the video to disk? If I use Save As it is saving .swf, not the video.
Comment: http://stackoverflow.com/questions/2792862/how-to-extract-flv-stream-from-jw-player-5-1
Answer: Although the URL for the SWF will be in the page source, in most cases this will not help you.
The SWF is usually streaming the video, alternatively it could have the video embedded in it.  Most flash swf container have their video encoded as an flv or f4v. The link will explain the various encoding that may be in play (H.263, H264, On2...). The best thing to do is to use a browser plugin like tamper-data, fire-bug, safari's web-inspector resources, or a proxy to watch all the requests made while it is running the SWF. FLVs are often streamed over plain HTTP, and can therefore, once you find the url with the aforementioned inspection, be downloaded simply. They can be played back with an FLV player (there's a couple, most are iffy), or in a container built with flash, or Adobe Air. You probably want to convert them, which is trickier, but there's some ffmpeg guides with parameters to be found online. In the rare case that the SWF contains the video embedded in itself, you can use a tool to extract it, oddly enough some versions of ffmpeg do this.
Answer: .swf IS the video (Shockwave Flash)
you can drag the SWF file into your browser or use some stand-alone player (e.g. Flash Movie Player) to play the video.
Comment: This is wrong. Flash videos are encoded as .flv files, which could be anything from sorenson spark to on2 something. Also H.263 and H.264. They are embedded or often streamed into .swf files. Downloading the .swf won't necessarily get the actual video. Check your browser's requests when loading the swf.
Comment: Pretty sure this person wants a .mpg or .avi video file instead of the swf.  So for example, they want to go to a website that streams video using flash and rip the video out of it.  I know there are ways to extract YouTube videos as .avi/mpg but the techniques are hacks and specific to the swf file/site. I'm thinking if the site wanted you to download the videos as avi/mpg then they would provide links to those formats.
Comment: Matt, i have long since retired from the mind reading business. :)
Answer: SWF Extractor This software can be used by the users to extract all uncompressed SWF files. It is easy to start its process by using its "Open and Extract all" button. It decompiles MP3 files and images from SWF and the users can have a facility to view all extracted resources by using a grid below the button.
Answer: A .swf file is a shockwave flash video. In order to view it on your computer offline you'll need flash player.
Answer: Actually, to play the SWF file, it needs to be downloaded to your disk first. It is usually saved in your temporary internet files. The map is hidden, by default on Windows.
Answer: The quickest way is to get the .swf file path, then copy this to notepad...
Right click here and click save as

For example, if I wanted to get http://mysite.com/test.swf I would use.
Right click here and click save as

Then save it as a .htm or .html files called anything you want. Double click on it and then do as it says!
When you have saved the file, you should be able to open it up VLC media player, Flash Player or convert it using the usual set of tools.
Answer: View the html source of the page, search the page with Ctrl+F and search for ".swf".
Click on the link and save the page (Ctrl+S).

Downloading video from SWF


What is the difference between Early and Late Binding?

Question: What is the difference between early and late binding?
Comment: Would I be wrong to say early = direct function call while late = call to function through a function pointer?  It never ceases to amaze me how programmers have a way of taking simple concepts and making them seem way more complex than they are (as a show of intelligence?).  Programming is inherently a very easy field of study until you get down to things like how a float type is made or the development of compilers.
Comment: [Late and early binding](http://calculist.blogspot.com/2006/05/late-and-early-binding.html)
Comment: Possible duplicate of [Early and late binding](https://stackoverflow.com/questions/484214/early-and-late-binding)
Answer: The short answer is that early (or static) binding refers to compile time binding and late (or dynamic) binding refers to runtime binding (for example when you use reflection).
Comment: But the wikipedia article on late binding (http://en.wikipedia.org/wiki/Late_binding) says that "Late binding is often confused with dynamic dispatch, but there are significant differences". So are they the same or not? If they are the same, then that wikipedia page needs to be changed.
Comment: Better stackoverflow answer here http://stackoverflow.com/questions/484214/early-and-late-binding
Answer: In compiled languages, the difference is stark.
Java:
//early binding:
public create_a_foo(*args) {
 return new Foo(args)
}
my_foo = create_a_foo();

//late binding:
public create_something(Class klass, *args) {
  klass.new_instance(args)
}
my_foo = create_something(Foo);

In the first example, the compiler can do all sorts of neat stuff at compile time.  In the second, you just have to hope that whoever uses the method does so responsibly.  (Of course, newer JVMs support the Class<? extends Foo> klass structure, which can greatly reduce this risk.)
Another benefit is that IDEs can hotlink to the class definition, since it's declared right there in the method.  The call to create_something(Foo) might be very far from the method definition, and if you're looking at the method definition, it might be nice to see the implementation.
The major advantage of late binding is that it makes things like inversion-of-control easier, as well as certain other uses of polymorphism and duck-typing (if your language supports such things).
Answer: Similar but more detailed answer from Herbert Schildt C++ book:-
Early binding refers to events that occur at compile time. In essence, early binding occurs when all information needed to call a function is known at compile time. (Put differently, early binding means that an object and a function call are bound during compilation.) Examples of early binding include normal function calls (including standard library functions), overloaded function calls, and overloaded operators. The main advantage to early binding is efficiency. Because all information necessary to call a function is determined at compile time, these types of function calls are very fast.
The opposite of early binding is late binding. Late binding refers
to function calls that are not resolved until run time. Virtual functions are used to achieve late binding. As you know, when access is via a base pointer or reference, the virtual function actually called is determined by the type of object pointed to by the pointer. Because in most cases this cannot be determined at compile time, the object and the function are not linked until run time. The main advantage to late binding is flexibility. Unlike early binding, late binding allows you to create programs that can respond to events occurring while the program executes without having to create a
large amount of "contingency code." Keep in mind that because a function call is not resolved until run time, late binding can make for somewhat slower execution times.
However today, fast computers have significantly reduced the execution times related to late binding.
Comment: "the object and the function are not linked until run time" This statement seems to imply that an object exists prior to run time. Aren't objects purely run time entities? Its the class of the object that exists at compile time. This could be better stated as "the function call and its implementation are not linked until run time"
Comment: one example of late binding is in polymorphism (in OOP) that we use interfaces or abstract classes and then we bind to that in runtime.
Answer: Taken directly from http://word.mvps.org/fAQs/InterDev/EarlyvsLateBinding.htm

There are two ways to use Automation (or OLE Automation) to
  programmatically control another application.
Late binding uses CreateObject to create and instance of the
  application object, which you can then control. For example, to create
  a new instance of Excel using late binding:
 Dim oXL As Object
 Set oXL = CreateObject("Excel.Application")

On the other hand, to manipulate an existing instance of Excel (if
  Excel is already open) you would use GetObject (regardless whether
  you're using early or late binding):
 Dim oXL As Object
 Set oXL = GetObject(, "Excel.Application")

To use early binding, you first need to set a reference in your
  project to the application you want to manipulate. In the VB Editor of
  any Office application, or in VB itself, you do this by selecting
  Tools + References, and selecting the application you want from the
  list (e.g. "Microsoft Excel 8.0 Object Library").
To create a new instance of Excel using early binding:
 Dim oXL As Excel.Application
 Set oXL = New Excel.Application

In either case, incidentally, you can first try to get an existing
  instance of Excel, and if that returns an error, you can create a new
  instance in your error handler.
Comment: I know this reply is old, and it's sourced from somewhere else, but it's not accurate. Late binding implies use of CreateObject, but CreateObject does not necessarily imply late binding. Binding does not apply to the method of instantiating an object, only to how it is declared. If you declare your object "As Excel.Application" it doesn't matter how you instantiate it. I always use CreateObject to instantiate object references to external libraries, that way I can switch between early and late binding and only have to switch one line (not two) -- the line that declares the object.
Answer: In interpreted languages, the difference is a little more subtle.
Ruby:
# early binding:
def create_a_foo(*args)
  Foo.new(*args)
end
my_foo = create_a_foo

# late binding:
def create_something(klass, *args)
  klass.new(*args)
end
my_foo = create_something(Foo)

Because Ruby is (generally) not compiled, there isn't a compiler to do the nifty up-front stuff.  The growth of JRuby means that more Ruby is compiled these days, though, making it act more like Java, above.
The issue with IDEs still stands: a platform like Eclipse can look up class definitions if you hard-code them, but cannot if you leave them up to the caller.
Inversion-of-control is not terribly popular in Ruby, probably because of its extreme runtime flexibility, but Rails makes great use of late binding to reduce the amount of configuration necessary to get your application going.
Comment: This point applies also to compiled languages that may include components compiled JIT and included at runtime to implement plugins or dynamic frameworks. Some canonical examples of this exist in Java, and of course Ruby and Python as well. An extreme example is Erlang, where the runtime can load two versions of any module at once for live upgrades/downgrades. So though a lot of Erlang code (most?) is written as statically typed pure functions, the runtime requirements mandate late binding and dynamic types under the hood.
Answer: The easiest example in java:
Early (static or overloading) binding:
public class Duck {
    public static void quack(){
        System.out.println("Quack");
    }
}

public class RubberDuck extends Duck {
    public static void quack(){
        System.out.println("Piiiiiiiiii");
    }
}

public class EarlyTest {
    public static void main(String[] args) {
        Duck duck = new Duck();
        Duck rubberduck = new RubberDuck();

        duck.quack();
        rubberduck.quack(); //early binding - compile time
    }
}

Result is:
Quack
Quack

while for Late (dynamic or overriding) binding:
public class Duck {
    public void quack(){
        System.out.println("Quack");
    }
}

public class RubberDuck extends Duck {
    public void quack(){
        System.out.println("Piiiiiiiiii");
    }
}

public class LateTest {
    public static void main(String[] args){
        Duck duck = new Duck();
        Duck rubberduck = new RubberDuck();

        duck.quack();
        rubberduck.quack(); //late binding - runtime
    }
}

result is:
Quack
Piiiiiiiiii

Early binding happens in compile time, while late binding during runtime.
Answer: public class child()
{    public void method1()
     {     System.out.println("child1");
     }
    public void method2()
     {     System.out.println("child2");
     }

}
public class teenager extends child()
{    public void method3()
     {      System.out.println("teenager3");
     }
}
public class adult extends teenager()
{
    public void method1()
    {    System.out.println("adult1);
         super.method1();
     }
}

//In java
public static void main(String []args)
{    ((teenager)var).method1();
}

This will print out
adult1
child1

In early binding the compiler will have access to all of the methods
in child and teenager
but in late binding (at runtime), it will check for methods that are overridden
at runtime.
Hence method1(from child -- early binding) will be overridden by the method1 from adult at runtime(late binding)
Then it will implement method1 from child since there is no method1 in method1 in teenager.
Note that if child did not have a method1 then the code in the main would not compile.
Answer: The compile time polymorphism also called as the overloading or early binding or static binding when we have  the same method name with different behaviors. By implementing the multiple prototype of the same method and different behavior occurs in it. Early binding refers first compilation of the program .
But in late binding object is runtime occurs in program. Also called as Dynamic binding or overriding or Runtime polymorphism.


Can we use a VIX-like method to calculate implied volatility for Black Scholes model?

Question: So I understand that the VIX is an estimate of implied volatility. Volatility can also be calculated from the Black Scholes model. My question is can we use a VIX-like method to calculate implied volatility (of individual equities, not SPY or SPX) and plug that in the B/S model to get a price estimate of the option?
Comment: ie, can you 'calculate' how vol should be priced using BSM and use it to determine over/undervalued options?  Not successfully, no.  Implied vol is also known to be consistently higher than realized vol.
Comment: I'm sure you can use that as an estimate for IV, but the question is, what is your goal?  Maybe you are looking for a single IV figure that represents the entire SPX curve for an option with about 30 days to expo.  I could see that.  But for pricing an individual option, you'll have to have real conviction to believe it is priced differently from the current market price., and that using the VIX value for IV is the right IV value.
Answer: The VIX methodology is rather involved but in essence it uses all of traded near the money (as it turns out they need not be near the money as long as they are within a continuum of traded options strikes), near dated S&P 500 options to arrive at the VIX (A detailed explanation of the calculation can be found on the CBOE website, http://www.cboe.com/products/vix-index-volatility/vix-options-and-futures/vix-index/the-vix-index-calculation).  As such, it is a composite of the implied volatility of short term S&P 500 options.
As there is a skew and term structure of volatility, using such a composite index of a particular equity would not be helpful in pricing individual options.  To price individual options, if they are not listed or customized in strike or maturity, the best approach would be to use the closest to the money and maturity of exchange traded options and use an accepted method of interpolating the implied volatilities of said options to arrive at an implied where your customized options may be valued.


Fatal error after brew update and brew upgrade

Question: $ brew update
Error: Permission denied - /usr/local/Library/Formula/abyss-explorer.rb

$ brew upgrade
==> Upgrading 20 outdated packages, with result:
ant 1.9.4, automake 1.14.1, elasticsearch 1.2.0, erlang R16B03-1, gd 2.1.0_2, git 1.9.3, gnuplot 4.6.5, ios-sim 1.9.0, leiningen 2.3.4, libgpg-error 1.13, libpng 1.6.10, libyaml 0.1.6, maven 3.2.1, mongodb 2.6.1, openssl 1.0.1g, python 2.7.6_1, readline 6.3.5, redis 2.8.9, sqlite 22.214.171.124, wget 1.15_1
==> Upgrading ant
==> Downloading https://downloads.sf.net/project/machomebrew/Bottles/ant-1.9.4.mavericks.bottle.tar.gz
######################################################################## 100.0%
==> Pouring ant-1.9.4.mavericks.bottle.tar.gz
  /usr/local/Cellar/ant/1.9.4: 1597 files, 39M
==> Upgrading automake
Error: Permission denied - /usr/local/share/doc/automake

Comment: Please try and explain your problem.
Answer: Homebrew needs /usr/local/ to be owned by you:
sudo chown -R `whoami` /usr/local

Answer: In general, when you experience an error with Homebrew, a good place to start debugging is to run brew doctor.  It often suggests some solutions.  It looks like you haven't tried that yet, so if you get into trouble, start there.
You can also consult the Homebrew web page, the Homebrew wiki, and the Homebrew troubleshooting page.  If you consult those resources, you'll find suggestions to run brew doctor and to set the permissions on /usr/local... as well as other suggestions.
So, please try those first, if you get into trouble again in the future.


Force Fresh Images on IIS 7

Question: How do I force IIS 7 to not cache images on a certain page?
Answer: I don't think the IIS web server is the one caching pages - it's the client's browser.
You can add a meta tag to the pages you don't want the client side to cache, and there are ways to do this for different older browsers and such.
If you write in ASP and want the same non-cache effect, here's the header information.
<% Response.CacheControl = "no-cache" %>>
<% Response.AddHeader "Pragma", "no-cache" %>
<% Response.Expires = -1 %>

Comment: Those Response directives will only set the headers for ASP pages, not for static images. IIS settings need to be adjusted for static images.
Answer: The thing you are looking for is cache-control header value (note that this only works for browsers that respect http 1.1)
For asp the code is:
<% @Language="VBScript" %>
<% Response.CacheControl = "no-cache" %>

You can also set this directly on a folder using the metabase:
Here's how you would set the folder pix on the default website:
Open a command prompt and change to your C:\InetPub\AdminScripts folder.
Run the following command:
CSCRIPT ADSUTIL.VBS SET W3SVC/1/ROOT/pix/CacheControlCustom "no-cache"
Note the possible values are "no-cache" , "Public", "Private"
Yo can also set this via ADSI:
Option Explicit
Dim objCache
Set objCache = GetObject("IIS://localhost/w3svc/1/root/pix")
objCache.CacheControlCustom = "no-cache"
objCache.SetInfo

So far these approaches will work on IIS6 and IIS7 so long as you have the IIS6 admin tools installed.  For a pure IIS7 environment here are the appcmd commands:
First unlock the config section
appcmd unlock config /section:staticContent

Now you're good to change the caching options for static content.
Make static content non-cacheable by setting "Cache-Control: no-cache":
appcmd set config "Default Web Site/<Application>/<Folder>" /section:staticContent /clientCache.cacheControlMode:DisableCache

Where <Application>/<Folder> is the path to your folder
See also IIS 7.0: clientCache Element for staticContent (IIS Settings Schema)

Force Fresh Images on IIS 7


outbound message session id raises "This session is not valid for use with the REST API" error

Question: I have an Outbound Message that is received by a php webserver. The session Id is extracted and as per https://developer.salesforce.com/docs/atlas.en-us.api.meta/api/sforce_api_om_outboundmessaging_setting_up.htm
the session id is used to call back into the originating Salesforce with a REST apex call. https://XXX.my.salesforce.com/services/apexrest/VI/Contact/003O00000XXXXXXIAH.
<code>        $sf_url .= '/services/apexrest/VI/Contact/'.$sfObject;
          $this->_log('/onAfterRoute.txt', 'sfURL: '.$sf_url, FILE_APPEND);
          $this->_log('/onAfterRoute.txt', 'sessionId: '.$sessionId, FILE_APPEND);
        $curl = curl_init();

        curl_setopt_array($curl, array(
          CURLOPT_URL => $sf_url,
          CURLOPT_RETURNTRANSFER => true,
          CURLOPT_SSL_VERIFYPEER, false,
          CURLOPT_SSL_VERIFYHOST, false,
          CURLOPT_CUSTOMREQUEST => "GET",
          CURLOPT_HTTPHEADER => array(
            "authorization: Bearer ".$sessionId,
            "cache-control: no-cache",
          ),
        ));

        $response = curl_exec($curl);
        $err = curl_error($curl);
        curl_close($curl);

</code>
The user configured on the Outbound Message has API and REST permissions but the REST apex call fails with "This session is not valid for use with the REST API".
The help I've been able to find references 'Use Any Api Client' but that dates from 2019 and I can't find that permission in my profile. I think it is also a fairly broad permission and pretty open to abuse.
The originating/destination salesforce site has MFA enabled if that is an issue.
Does anyone know what permission I need to create a session id that can call an apex REST endpoint?
Thanks, Greg.
I've also cross-posted this on developer.salesforce.com/forums without luck. Trying here for a different result.
Answer: Turns out the user account I was using for Outbound Message (and hence the session id) was a High Assurance account. It had all the permissions for REST API access but was High-Assurance. I switched to a non-High Assurance account and I'm off and racing.


Need help in implementing DICOM in JAVA

Question: I want to implement Dicom using JAVA.
      And also i should not use any existing API and i have to develop from the scratch.
      I spent almost 10 days in understanding DICOM itself,i got some vague idea
      so kindly help how implement it in java , where to start,architechture etc...
Answer: I agree with malat. DICOM is a complex beast and re-implementing everything from scratch is likely not the way to go.
I would also add dcm4che as a toolkit which can be used to process, create and manipulate DICOM objects in Java.
Comment: This is how I started. It works to learn it via dcm4che :) Took me about 3 years additionally to the main job.
Answer: I would read the source code of other open-source projects such as:

GDCM
DCMTK
dicom3tools

DICOM can be very subtle, I would say it will take you 3-5 years of experience to understand all the details and fix all your bugs. You should avoid re-inventing the wheel.

Need help in implementing DICOM in JAVA


Programs similar to iPhoto or Picasa with geotagging?

Question: I recently asked a question on Ask Different and it led to me to the discovery of Picasa. Admittedly, iPhoto would've been much better, but I have a Windows laptop. Anyways, the only feature that I'm looking for is the geotagging feature. Picasa can do that but it's pretty lame. You can only do one picture at a time and it gives you latitudes and longitudes and an option for a map that you can open, but only on every individual picture. Is there any other program that has an interface that's more similar to the one on your iPhone? Where it can show you all the pictures in all of the locations at once, and once you zoom in the locations branch out?
Answer: There is Pictmo with the geotag extension it is freeware, (but still copyrighted), for Windows. And is probably worth a try.


Why do we miss 8 in the decimal expansion of 1/81, and 98 in the decimal expansion of 1/9801?

Question: Why do we miss $8$ in the decimal expansion of $1/81$, and $98$ in the decimal expansion of $1/9801$? I've seen this happen that when you divide in a fraction using the square of any number with only nines in the denominator. Like in
$$
  \frac{1}{9^2}=\frac{1}{81} =
  0.01234567\!\underset{\uparrow}{}\!9
    01234567\!\underset{\uparrow}{}\!9
    01234567\dots\,,
$$
and in
$$
  \frac{1}{99^2}=\frac{1}{9801} =
  0.0001020304050607080910111213 \dots 9697\!\underset{\uparrow}{}\!99000102 \dots\;\,,
$$
the decimals go on predictably when suddenly in the first one you miss $8$, and in the second you miss $98$ and it keeps going on forever. How does this happen? Why do we miss numbers like $8$ in the decimal representation of $\frac{1}{9^2},$ or like $98$ in the decimal of $\frac{1}{99^2},$ or $998$ in $\frac{1}{999^2},$ or $9998$ in $\frac{1}{9999^2}\;$?
Comment: This has been bugging me since I was 6 years old.  Thanks for asking and thanks to those who answered!
Answer: For $\frac{1}{81}$, there was an $8$, but it got bumped up. We can write $\frac{1}{81}$ as this sum:
$$
\large{\frac{1}{81}}=\;\;\;\small
\begin{align}
     &0.0
\\+\;&0.01
\\+\;&0.002
\\+\;&0.0003
\\+\;&0.00004
\\+\;&0.000005
\\+\;&0.0000006
\\+\;&0.00000007
\\+\;&0.000000008
\\+\;&0.0000000009
\\+\;&0.00000000010
\\+\;&0.000000000011
\\+\;&\underline{\quad\vdots\quad\quad\quad\quad\quad}
\\   &0.01234567901 \dots
\end{align}
$$
This kind of effect of "carrying the $1$" when the nine digit flips to a ten is the thing that is causing the behavior in all of the fractions you are describing.

To follow-up, this should provide a bit more insight as to why interesting patterns appear in the decimal representations of fractions with a power of $9$ or $11$ as the denominator, and see why we can write those numbers like $\frac{1}{81}$ as that sum. First note that
$$
\frac{1}{9} = \left( \frac{1}{10}+ \frac{1}{100}+ \frac{1}{1000}+ \dotsb \right)
$$
so if we were to consider $\frac{1}{81}$ like before, we would have
$$
\frac{1}{81} = \left(\frac{1}{9}\right)^2
             = \left( \frac{1}{10}+ \frac{1}{100}+ \frac{1}{1000}+ \dotsb \right)^2
$$
Then if we were to want to know the value of the ten-thousandth's decimal place of $\frac{1}{81}$, we would just have to find the numerator of the term in the expansion of this square with a denominator of $10\,000$, which we can readily see is
$$\begin{align}
\frac{1}{81} = \Big( \dotsb + \Bigg(\Big(\frac{1}{10}\Big)\Big(\frac{1}{1000}\Big)+\Big(\frac{1}{100}\Big)&\Big(\frac{1}{100}\Big)+\Big(\frac{1}{1000}\Big)\Big(\frac{1}{10}\Big)\Bigg) +\dotsb \Big) \\
             = \Big( \dotsb + \Bigg(\frac{3}{10000}&\Bigg) +\dotsb \Big)
\end{align}$$
So it looks like these evident patterns that appear in the decimal expansions of fraction with a multiple of $9$ in the denominator is due at least partly to the fact that this infinite sum representation of $\frac{1}{9}$ consists entirely of terms with a numerator of $1$, so multiplying this sum into things may result in "predictable" behavior that results in a pattern.
As for why having a multiple of $11$ in the denominator makes similar patterns, note that
$$\begin{align}
\frac{1}{11} &= .090909090909090909 \dots \\
             &= \left(\frac{9}{100}+\frac{9}{10000}+\dotsb\right) \\
             &= \left(\frac{10-1}{100}+\frac{10-1}{10000}+\dotsb\right) \\
             &= \left(\frac{1}{10}-\frac{1}{100}+\frac{1}{1000}-\frac{1}{10000}+\dotsb\right)
\end{align}$$
So again we have an infinite sum of terms each with a numerator of $1$ (just alternating sign this time) that will result in certain "predictable" patterns when multiplied by things.
Comment: Basically, 8 is the first number from the "large" end that can swallow a carry. Thus 8 is the one that often falls victim to that carry.
Comment: How did you determine that 1/81 could be expressed by that sum? Sorry if this is a dumb question, I'm not really a math guy. Is that a rule somewhere?
Comment: Use long division to divide 81 into 1.
Comment: This explains why that eight is gone.
Comment: @JasonC I actually had no idea, but just noticed the pattern. In a bit I'll start playing around with it. I think it just has to do with dividing by a power (multiple maybe) of 9, one less than the decimal base. Kinda like $1/9 = .1 + .01 + .001 + ...$
Comment: What's actually going on is that the [generating function](https://en.wikipedia.org/wiki/Generating_function) for the sequence 0,1,2,3,... is $\frac{1}{(1-1/x)^2}$, in the sense that $$\frac{1}{(1-1/x)^2}=0x+1x^2+2x^3+3x^3+\cdots$$ for small enough $x$. Plugging in $x=1/10$ or $1/100$ gives a fraction that equals a sum of successive integers moved steadily one or two decimals further right.
Comment: Why is $\frac{1}{9}$ equal to $\frac{1}{10} + \frac{1}{100}...$?
Comment: @Imray If you punch it into a calc, you can see that the decimal approximation of $\frac{1}{9}$ is $0.1111\dots$. Then we just separate this decimal into the sum of each digit divided by its place value. So we have $\frac{1}{10}+\frac{1}{100}+\dotsb$.
Comment: Does this rule mean that if we had (1/8)^2 in base nine or (1/ten)^2 in base eleven that we would also see this pattern?
Comment: @AaronFranke yep. Because $\frac{1}{8} = \frac{1}{9}+\frac{1}{9^2}+\dotsb$
Answer: "Originally" there were 95, 96, 97, 98, 99, 100, 101, 102 ... but since there's only two digit positions for each of them, the one in front of 100, 101, and so forth carries over to the number in front of it and increases that preceding number by 1. This makes 99 into 100, and the one in front of that then carries over to 98 and makes it 99. And that's where the carries stop.
So the reason why exactly 98 is the one that is missing is that 98 is the largest two-digit number that can be increased by one without gaining another digit that would carry.

It may be instructive to see what happens if we look at some other "original" pattern than 0, 1, 2, 3, ..., 98, 99, 100, 101 ...
For example, $\frac{7}{9801}$ should produce

0, 7, 14, 28, ..., 84, 91, 98, 105, 112, 119 ...

but when carrying out the division the digits we get are:
7/9801 = 0.00071428...849199061320...

because of carries. Here one sees more clearly that 98 is not "missing", it is just increased by one, like the last two digits of the subsequent numbers in the sequence.
We can also look at
9/9801 = 0.00091827...819100091827...

Here, like in $\frac1{9801}$ there's a 99 in the original sequence, but it gets bumped up to 100 by the carry, and then the "original" 90 in turn gets bumped up to 91. Likewise
11/9801 = 0.0011223344556677890011223344...

There's two of every digit except 8 and 9! Again, what really happens is that the original 99 gets bumped to 100, which again bumps 88 to 89.
Answer: Here's my answer now: The eight gets bumped to a nine and the nine gets bumped to a zero right here: $0.01+0.002+0.0003+0.00004+0.000005+0.0000006+0.00000007+0.000000008+0.0000000009+0.00000000010=0.012+0.0003+0.00004+0.000005+0.0000006+0.00000007+0.000000008+0.0000000009+0.00000000010=0.0123+0.00004+0.000005+0.0000006+0.00000007+0.000000008+0.0000000009+0.00000000010=0.01234+0.000005+0.0000006+0.00000007+0.000000008+0.0000000009+0.00000000010=0.012345+0.0000006+0.00000007+0.000000008+0.0000000009+0.00000000010=0.0123456+0.00000007+0.000000008+0.0000000009+0.00000000010=0.01234567+0.000000008+0.0000000009+0.00000000010=0.012345678+0.0000000009+0.00000000010=0.0123456789+0.00000000010=0.0123456790$so this is what happens.  As you just saw, the 0.00000000010 (0.0000000001) changes the nine into a zero and it carries one into the eight, so it becomes a nine.


How to delete spaces between different shapes after you divide a shape in multiple ones in adobe illustrator?

Question: I'm a beginner with adobe illustrator and for a project we need to split letters(A,B,C..) in many pieces because we need it for an application, and I did that using shape builder tool, pathfinder-divide, knife tool etc but when I save it as SVG(we need it like that) the shapes have a bit space in borders(like a white line). Does anybody know how can I divide without those lines or hide them?
Comment: If these are conflation artefacts, see [possible related question here](https://graphicdesign.stackexchange.com/questions/65058/image-looks-embossed-when-converted-to-svg/65060#65060)
Comment: Are you able to provide any visual examples? I think it would help to show of the issue more clearly
Comment: Sounds like conflation artefacts.  Could you please post a screenshot. Thanks
Comment: @BillyKerr Yes, can you please check this image.
Comment: @epp Yes, those are conflation artefacts.
Answer: SVGs with exact borders between parts have that error. It's not in SVGs. Programs which render those SVGs for raster displays create 1px wide partially transparent zone to reduce jagginess. That's anti-aliasing. You must put something behind the shapes, maybe the same shapes shifted 1px horizontally and vertically or generate overlaps by inserting a stroke.


Complete beginner at electric guitar with pain on fretting hand's wrist

Question: So as the title says I am a complete beginner at the guitar and am experiencing a lot of pain on fretting hand's wrist. The pain comes in after about 2-5 minutes of play.
Is this something that will go away as my hand gains flexibility over time or could it be bad positioning/posture? As I move to the 12th fret, my elbow gets closer to my stomach. My fretting hand bends at the wrist and forms a 90 degree angle. Any answers would be greatly appreciated.
Answer: Your fretting hand should not make a 90 degree angle (at least not continuously), it may occasionally for some chords.
More importantly: Does it bend 90 degrees towards you or away from you?
If that seems ambiguous please try to describe the exact shape, or take a pic and post it.
The wrist should be close to straight with a slight bend.  Regardless of the cause of the pain the posture you describe does not sound correct.
Some "discomfort" is normal but the type of pain you are describing is not normal and could eventually lead to carpel tunnel, tendonitis, the development of cysts, and other issues.  Please find a guitar teacher who knows what they are doing and take some lessons.  Or find reliable on line examples.
The problems with on-line examples is that you kind of have to know how to play to be able to discern if what you are seeing is correct.
Answer: First and foremost;
Do not play sitting down on the couch, or slumped onto your bed and pillows.
Your arms become trapped and immobile due to the restrictions of the structures of the offending furniture.
In other words, stand up and play the guitar.
Get a strap, and play standing, the way you will want to play when you are performing live, in front of people.
This way your arms and wrists are unencumbered, and free to move around, which is exactly how various chords and phrasings demand they be.
Cinch the guitar strap up to where your guitar is centered on your navel, not hung low down below your tender bits.
While you are learning the fundamentals, it is important that the angle of your wrist and fingers allows you to play barre chords comfortably and without distortion of your tendons and connective tissue. (Hanging the guitar down low, a la Jimmy Page or Slash may look cool in the rock videos, but it is no way to try and learn the instrument.)
If the guitar isn't comfortably and ergonomically-centered on your body, you just won't be able to learn the thing.
Does this make sense?
Answer: You need to get assistance from a friend or a teacher, anybody with quality guitar experience, that

is going to see you play!!!
you are going to watch play!!!
is going to help you improve / kill bad habbits

That stage at this point seems to be mandatory.


How do I manage Java timer tasks?

Question: I'm looking for some guidance on how to manage multiple timer tasks.  I'd like to be able to dynamically create timers and then when each timer is finished, it'll reset itself.
Example:
Timer 1
 - perform action x
 - reset to perform action x again in 30 minutes
Timer 2
 - perform action y
 - reset to perfom action y again in 10 minutes
Answer: What you want is the ScheduledExecutorService.
It allows you to schedule tasks to run at a given time or at a given rate.
Answer: The following code creates a timer and executes it every 1000 ms after an initial delay of 500 ms. You can easily define two or more timers this way.
<code>TimerTask task = new TimerTask() {
    @Override
    public void run() {
        System.out.println( "exec" );
    }
};

new Timer().scheduleAtFixedRate( task, 500, 1000 );
</code>
Comment: Well I'd actually like to reschedule the task after previous task has completed (to ensure they aren't overlapping).
Answer: Perhaps it could be worth reviewing Quartz Enterprise Job Scheduler

Quartz is a full-featured, open source job scheduling system that can be integrated with, or used along side virtually any J2EE or J2SE application - from the smallest stand-alone application to the largest e-commerce system. Quartz can be used to create simple or complex schedules for executing tens, hundreds, or even tens-of-thousands of jobs; jobs whose tasks are defined as standard Java components or EJBs.

How do I manage Java timer tasks?


(XPS13) reinstalling keyboard support from recovery mode

Question: I accidentally removed libinput while trying to revert to synaptics on Ubuntu on my XPS 13 9350), so the keyboard constantly sends returns making it impossible to use the desktop.
In the recovery mode, I guess I could reinstall libinput, but I cannot get my wlan to work.
I already configured wpa_supplicant and try getting the network interface up using wpa_supplicant -B -iwlp58s0 -c/etc/wpa_supplicant.conf -Dwext but this results in an error ioctl[SIOCSIWENCODEEXT]: Invalid argument which I cannot find a solution for.
Is there a way I can just get my keyboard working without internet access, and if not, what am I doing wrong for getting wlan back up?
Answer: I found out that the reason the keyboard was sending return keystrokes was because I used the virtual keyboard on the login screen to enter my password and I had used the virtual return button to log in. There is apparently a bug in this which will continue sending return keystrokes even after the virtual keyboard has disappeared.
I logged in a second time, used the Ubuntu virtual keyboard to install the openssh-server and then ssh'd in from another computer to reinstall libinput. All good now, except that the touchpad still behaves strangely and I hope I'll never need WiFi from the recovery console because I wouldn't know how to set it up.


Points from earning hats in the winter bash?

Question: I am very enthusiastic about earning hats on multiple sites in the winter bash. It is an engaging concept too. However, I am wondering if my reputation can increase because of that i.e. get more points.
Answer: Hats themselves do not give any reputation points.
However, if you make a post or suggest an edit to get a hat, and your post gets upvoted or your edit gets accepted, you get the reputation from that.
Answer: Hats are temporarily, as explained also in winter-bash:

... that typically runs from mid-December until early January each year ...

Also, as mentioned in the accepted answer to ' Is there a simple page, "What is Winter Bash, and what's all this about hats"? Can we have one? ':

When the event is over, the "hats" are all gone and can't be accessed anymore.

So as soon the hats disappear again, all points (= reputation) gained from earning hats would have to be deducted also again ... assuming that such reputation changes would be consistent with what happens if questions or answers disappear (= get deleted), in which case the reputation changes from deleted posts get corrected also.
Answer: Increasing the number of hats does not increase the reputation. To increase reputation check that and Votes on posts cause you to gain (or sometimes lose) reputation.


How to become invisible to opped members in minecraft?

Question: I have installed a plugin called Vanish No Packet in a Minecraft Bukkit Server in which I play with my friend. I am the owner of the server but my friend is also op. I thought of trolling him by becoming invisible but he was able to see me. What can I do so that even the op players can't see me? What changes do I have to make in the permissions file? You can also download my server's permission file and make changes.
Thanks!
Answer: Your friend can see you because all OP players have vanish.see permission by default, so you need to negate it.
I recognized that you use PermissionsEX reading the link that you have provided, so you could add your friend to a group that negates this permission or you could add it specifically for him.
To only for him:
/pex user YourFriendNick add -vanish.see

To create a group:
/pex group aNiceGroupName add -vanish.see
/pex user YourFriendNick group add aNiceGroupName

With a group you can add more friends adjusting the second command, so when you are done you can delete the group and the negative permission will be remove, allowing your friends to see vanished players again with a single command:
/pex group aNiceGroupName delete

Note: Your friend will not be able to see any vanished players if you negate the permission.
Answer: Here is an option you can use without plugins:
/effect give @s minecraft:invisibility 1000000 255 true

It does not show particles (due to the hideParticles option being set to true), and will apply forever (a very long time!).
To reverse this effect, you can use the following command:
/effect clear @s minecraft:invisibility

Comment: @Schism, you edited my answer stating that the order of parameters is amplifier before length. However, this is simply not true in the current latest version, 1.14.4, as [shown here](https://i.stack.imgur.com/fdnL5.png).
Comment: Ah, I attempted to force [this suggested edit](https://gaming.stackexchange.com/review/suggested-edits/281304) through with an update to the duration, but I copied it over wrong. (I had meant to press Improve but pressed Approve, and so I tried to copy over the edit, but I somehow missed the substantial part of it... whoops.)


The website is addressing 2 categories (employers and candidates), Which one should we be addressing more?

Question: I am working on a website that addresses both employers and candidates, and the user should choose whether he is an employer or a candidate from the homepage.
But i am lost here, If i want to add the benefits or how it works on the homepage? should i put it for the employers or for the candidates? or for neither and add them inside when the user chooses his category?
Answer: Without knowing very much about what your website does, I would suggest having a homepage that looks something like this:

At the top of your screen, let the users know a little about who your company is and what they do, then in order to provide more specific information towards Employers or Candidates, create two sections and list a few benefits for each party. Within those sections you can provide links so the user can continue on the path that applies to them.
Answer: Since the nature of the site is kind of vague, i am presuming that it is for an organization.
If by candidates, you mean general public who can visit the site without logging in then it would be helpful for them to read the potential benefits which the organization provides . It could communicate a clear idea to the visitors about the organization.
Once an employee logs in , you can very well add the employee perks to the list.
Or you can show them both which by itself will be a motivation to the candidates to become potential employees.


If a real image is formed at some distance from a concave mirror, how can we always see it, no matter where we are standing?

Question: In a typical concave mirror experiment, the "real" image can only be focused at a specific position, where the light rays meet. Yet, if I look at some stationary object behind me in a stationary concave mirror and move away from it, my eyes can always obtain an image of the object. How can that be possible?
Answer: You do not need to stand at the theoretical distance where a real image is formed, because your eyes are an additional optical element focusing light on the retina. In the distance where a real image is formed, you wouldn't need the lens in your eyes at all, your retina would be enough to see a sharp image, because this is the distance where rays from the mirror overlap to form a sharp image. At all other distances the image isn't sharp, a canvas or your pure retina would receive a blurred image. So you need your eyes there to do the additional necessary focusing. The additional focusing power is different at any distance, but your eyes are very good in adapting (basically your lens is shaped by muscles resulting in a different focal length).


Securing against DDoS

Question: My client would like to have his eCommerce (custom-made) site secured from DDoS attacks. What strategies can I implement? There are multiple forms in the purchasing flow --- searching, drilling-down to the product, user information and payment and I want to avoid captchas.
Answer: None of those will really protect from DDoS attacks. The point of a DDoS is to use up so much of the targets bandwidth that no legitimate traffic can get through.
Having a captcha or something will protect from bots, but thats about it.
The only way to mitigate (but not solve) the risk of DDoS attacks is to get more bandwidth and failover agreements with other hosting providers.
Comment: @gAMBOOKa: Yes, typically.  Can your captcha code handle millions of requests a second?  Can your hosting provider?
Comment: But don't DDoS attacks use zombie computers to run bot scripts?
Comment: Some do. A simple DDoS is to find out what server your site is on and simply flood it with page requests. That is essentially what is happening when a site gets slash-dotted.
Answer: There is nothing to prevent DDoS attacks, there is no single tool to mitigate them, you can only raise the bar, having a good firewall and some thresholds (automatic rejects, even banning) for accessing the different services/pages if you know the average use of the site
Comment: I'm curious: How would a firewall (good or bad) be helpful if the pipe is just full?
Answer: Squid can help with slashdotting. It will help your system handle large volumes of identical requests without pounding the hardware so hard.
 http://en.wikipedia.org/wiki/Squid_(software)
Answer: This guy has a way to help with application code. Not sure if it works for your language of choice, but the idea is good. Nothing is capable of stopping all attacks, but you can try to make it difficult for them =)
Answer: You can install mod_evasive if you are using Apache - a short description can be found here: http://www.think-security.com/protect-your-apache-web-server-with-mod_evasive/
Answer: A good relationship with your bandwidth provider is about the only thing that can help you mitigate a DDoS attack. The reason being that once the traffic hits your wire, it is effectively taking up bandwidth, so there's nothing you can put on your side that will help. Being able to work with your ISP to filter out DDoS traffic before it comes down the wire at you is both the only way to keep the traffic off of your circuit as well as the best way to escalate the issue (the ISP will likely try to filter the traffic coming into their network as well). Your ISP will be considerably more effective if other ISPs need to be contacted to shut down bot hosts...

Securing against DDoS


"I like listening to music" and "I like to listen to music" - is there any difference?

Question: When speaking about my hobby, should I say:

I like listening to music.
I like to listen to music.

Do both mean the same? Is any of these sentences grammatically incorrect?
Answer: In short: there is almost no difference when using them in that sentence, and both are grammatical and common.
In general, the "Xing" form is slightly more casual whereas the "to X" form is a bit more abstract. In the form "I like..." it's essentially the same, but the difference becomes a lot clearer when you use it as a subject:

Listening to music is the best hobby

vs.

To listen to music is the best hobby

The first sounds like you are speaking from personal experience, whereas the second sounds more like you are making a philosophical or poetic statement.
Slightly beyond the scope of your question, but one last thing to note is that there are some verbs that require one form or the other, and that will overrule any other consideration:

I enjoy listening to music [correct]
I enjoy to listen to music [wrong]

and

I want to listen to music [correct]
I want listening to music [wrong]
Comment: What are those verbs that have a particular requirement I mean besides the mentioned `want` and `enjoy`. Intuitively it seems to be somehow linked with the `process` vs `fact` thing i.e. `like` is ok with both process and fact but `enjoy` only makes sense with a `process` and `want` does only fit some `fact`.
Answer: The Oxford Guide to English Grammar by John Eastwood says in section 121.2:
Some verbs can take either a to-infinitive or a gerund with almost no difference.
Eastwood has the following list:
like love perfer hate
begin commence start continue cease
intend propose
can't bear
bother (I don't bother washing up/to wash up.)
He has some minor annotations to some of these verbs which I don't think very important.


Questionable content in student's theses

Question: If having some questionable aspects in the thesis - like not elaborated and rather simple theoretical models -, that did not influence the whole work and results, but might still arise the thought "Why didn't the student know/do better here?", can this have a negative influence when applying to some graduate school?
Comment: Obviously. This would also cast doubt on the advisor(s)' competence, or the student's sense to communicate with the advisor, and so on. Nothing positive in such a scenario.
Answer: My recommendation is for the student to make it clear in the thesis that they know these are overly simple theoretical models. If the models don't significantly affect the main results, it is difficult to see how being honest can hurt. And trying to make it appear that the models are more significant than they actually are could definitely hurt.
Comment: The student was more confident in his experimental skills than theoretical analysis ones. He explained the observations on a somewhat oversimplified model, but was aware of this and mentioned it whenever felt necessary, while also providing some first correction. He felt that elaborating a full model from the beginning would have exceeded his mathematical skills, eventhough it might have been easy for others...he's not known to be confident in mathematics. Despite providing first correction and mentioning the simple model's drawbacks, might this prevent him from getting into astro grad school?
Comment: @Lucas: I don't know ... I'm not familiar with what they're looking for in astro grad students.
Answer: It is very unlikely that the graduate admission committee will read your thesis when making admission decisions. The essay, transcripts, test scores, research experience, letters, and publication authorship are far more likely to be used to select the future graduate students.
Comment: @Lucas: The student's case wasn't good enough for him to be admitted if we completely ignored the research. And how can you tell whether a student is good at research when you're judging this from a mostly nonsensical paper, and the recommendation letter of an advisor who permitted (or encouraged) the student to write this paper?
Comment: You'd be surprised. I've read some applicants' posted arXiv papers, and for one of these I realized that it was more or less complete nonsense (probably mainly his advisor's fault). This definitely had a negative effect on his admissions decision—we rejected him.
Comment: So eventhough some fault may mainly be due to the advisor, a committee still punishes the applicant? Just out of curiosity and ignorance, so no judging: is this common?


How did they factor RSA 240?

Question: Since NFS runs in essentially $n^{1/3}$ time, and RSA-240 is a composite of two 120-digit primes, shouldn't this have taken at least $10^{40}$ operations, not including any overhead? Even if you could do say $10^{20}$ ops / s as modern supercomputers can almost do, this still should have taken essentially $\infty$ years. So what is this massive speedup I'm missing?
Comment: A bit of search turned up [the paper](https://eprint.iacr.org/2020/697.pdf) called "Comparing the Difficulty of Factorization and Discrete Logarithm: a 240-digit Experiment"
Answer: $\exp((\log n)^{1/3})\neq n^{1/3}$.
If you work through the formula for $L[\tfrac{1}{3},1.92]$ and set the $o(1)$ term to $0$, you get $2.4\cdot 10^{23}$ operations for $n\approx 10^{240}$.
The reported computation was 900 core years on a 2.1 GHz CPU, which is about $6\cdot 10^{19}$ cycles, which is much closer. Bear in mind that asymptotic notation can hide factors that actually make the result smaller sometimes.
Comment: I just looked at the linked document, and it says 1,000 core YEARS. Fifty top-of-the-range Macs for 4,000 dollars each can do this in a year for 200,000 dollars in total. Maybe 10,000 KWh.
Comment: Just checked: Your number of cycles is right. And the number of operations is probably higher.
Comment: Thanks, I think I used years for my calculation but wrote hours instead.

How did they factor RSA 240?


Do I install my green board before I install my shower pan?

Question: I have had to take my old corner unit shower out and about to install a bigger shower.  What I'm going back with is Cultured Marble.  This will be the pan and the walls.  I was told I needed to install the pan and prep the walls with the green board prior to them making and installing my walls.  My question is do I install the green board first or the shower pan?
Answer: Shower pan is always first because you want the top of the shower pan to the edge of the green board.  So there may be shimming involved to get the walls not only lined up with the pan but as close as you can to perpendicular.
I am not going to argue with your installers because I have had some large sheets of granite and marble installed for showers but I would recommend a backer board not green board.  Even if they say green board is fine because the water is impervious to their tile that doesn't mean water can't get on the green board from behind or up top.  And if they are gluing the sheets down there will eventually be issues.  Using Hardiboard would take water coming from any direction out of the equation.
Comment: So should I put the pan up to the studs and then bring my green board or backerboard down to it?  Is that what you are telling me?
Comment: Ted - How big is the pan compared to the area.  You should have framed around it on 3 sides so that it fits pretty snug.  Do you have a picture of what's going on?
Comment: I have a 45 3/4 inch opening and going to frame it down to a 42 inch opening.  I have plywood on the valve wall 36inch and also on the 42 inch back wall.  Will be putting up a new wall for the other 36 inch back wall of the new shower.  The plywood is not in good shape so I will replace it.  Then install the new back wall and finally set the shower pan.  Once that is complete, I will add my green board or backer board.  This make sense?
Comment: @Ted - Nothing wrong with using plywood to build out but I will say I have never installed green board for the outside of a shower area.  If you did you would have to put something over it like kerdi.  Is this what the marble manufacturer instructions say to do?
Answer: I don't know how far along you are, and I've never installed a shower, but I have installed a few bathtubs from scratch, and I assume the principles are the same.
I frame the enclosure to allow 1/4" extra all around, i.e for a 60" long tub I frame the opening 60-1/2" long. I make sure the corners are as square as I can get them, and the walls are straight and plumb. I make sure the studs in the corners are firmly tied together to minimize any flexing if someone heavy leans on the wall, and I make sure that there will be enough stud showing in the corner to fasten the boards on wall #2 after the boards are up on wall #1. I put blocking where any horizontal joints will be, including above where the top of the tub will be. I install the tub, shimming the studs with 1/4" shims to 1/4" above the top of the tub lip. I install 1/2" backer board 1/4" above the lip of the tub. (I agree with DMoore, above, about greenboard, I won't use it for a tub enclosure)
Since the framing is 1/4" "outside" the tub, the inside face of the 1/2" backer board is now 1/4" "inside" the tub. The lip of a tub is usually 1/8" to 1/4" thick, so the finish material (tile, marble etc.) can overlap the lip of the tub smoothly, with the back of the finish material barely touching, or almost touching, the inside face of the lip. If your shower pan lip is more than 1/4" thick you might need to adjust accordingly. Also, if you are thinking of going this route, you might want to check with your marble supplier to make sure that this extra 1/2" won't throw off their calculations.
Backer board is much more troublesome to cut than greenboard, and it is important to avoid breathing the dust. You can attach it with special screws designed for the purpose, or 1-1/4 galvanized roofing nails. The screws are hard to drive, an impact driver is the way to go, I find. I usually use half screws and half nails, because I prefer screws, but nails are quicker and much cheaper. Fasteners should be 8" OC, and should not be placed within 2" of the corners of the board, nor within 3/8 of the edges. I actually have a scrap of 3/8" plywood 8" long and 2" wide for this purpose.
Answer: Your shower pan kit should have instructions on how to install it.
Placing the green board in first, and then trimming it to slide the shower pan in isn't all that unusual.
I'd recommend either buying your shower pan first, so you can read the instructions before you start putting in the greenboard.  If you don't have the space to hold the shower pan, select the shower pan and look online for the installation instructions.


What information is available if you set up a node?

Question: I'm doing a project on blockchain technology where we are supposed to do some kind of measurement and evaluate the result. I've heard that you can set up a Ethereum node and get some kind of information that way, but I'm confused as to what information is available if you run your own node. Some guidelines of possible measurements that are possible would be greatly appreciated!
Thanks
Answer: I'm not sure what kind of information you are looking for. Statistics about the network or data about what happens in the network?
You get some statistics, such as current block number and so on. Some info is here: Ethereum block architecture and the Ethereum White Paper has more details.
But for network data, you get it all. Everything that happens in the network gets processed in your node as well. So if someone at the other side of the globe sends Ether to his friend, your node processes the transaction as well - all nodes process all transaction. So, you can basically follow anything that happens in the network.
Comment: Thanks for your reply. After some consideration, I'd like to be able to get information about the network, such as the location of all nodes in the network. Like what Ethernodes.org has done, but I'd prefer to do it myself. It says that it is powered by [EthereumJ](https://github.com/ethereum/ethereumj), so I assume they have looked through the open source code and figured out how to extract that information? Is there an easier way to get information of all nodes on the network from your own node?
Comment: I'd imagine they just traverse the nodes in some fashion and check their IPs and getlocate based on IPs. But can't give you much more ideas, I haven't played around with nodes much.


Difference between network and sub-network

Question: Today, at school I learned about subnetworks. So, let's say I have a 10.0.0.0 network with a 255.0.0.0 mask, I could subnet it into two networks, for example, 10.1.0.0 and 10.2.0.0, which would both have a 255.255.0.0 mask. But at this point, what's the difference between them being two subnets of 10.0.0.0 or just being two separate networks? Especially if they need routers between them, aren't them just two separate networks?
Comment: I believe that in this particular instance, subnetting refers to the fact that the addresses are assigned hierarchically, and that the routers outside 10.*.*.* do not need to know internal structure of the 10.*.*.* network. But subnets are pretty fuzzy defined terms, so there isn't always logic in them.
Answer: Today, network and subnetwork are mostly interchangeable. Depending on the context, network might refer to a wider view, an aggregation of multiple subnetworks. Subnetworks is a more precise term for logically distinct networks.
The terms had more distinct meanings when classful networking was still in use before 1993 when CIDR was introduced, but that is long obsolete.
Comment: You can also say that *every* network is a subnetwork of 0.0.0.0/0
Comment: So basically, this aggregation could be defined, for example, by the networks being in the same building? If my school has 3 networks, one for each floor, which don't communicate with each other (being 10.1.0.0, 10.2.0.0), can they still be considered subnetowks, simply because they're in the same building even tho they don't communicate between them?
Comment: Yes - aggregated over the same building, same city, same security zone, purpose, ... You could have such a "supernet" 10.1.0.0/16 that actually uses subnets 10.1.0.0/24, 10.1.1.0/24, ..., 10.1.255.0/24.


Robinson Arithmetic and Church-Turing Thesis

Question: What is the connection (if any) between proving the undecidability of Robinson Arithmetic and the Church-Turing Thesis? If there is any connection to CTT, is it necessary?
Comment: I've rolled back the question to its original form - if you want to ask a different question, do so in a separate post rather than radically changing this one.
Answer: There is no connection at all.
CT says that we can interpret the formal result "There is no Turing machine which decides whether a number is the Godel number of a theorem of Q" as "The set of Godel numbers of theorems of Q is not effectively calculable." But this is not relevant to proving that formal result in the first place.
Of course CT does get used all the time in proofs in computability theory, but only in the following way: when we want to argue that a certain operation is computable in the formal sense of Turing machines (or some equivalent model), rather than actually writing down a computation we just describe an algorithm and then say "By CT there's an actual machine which performs this algorithm." But this is only a time-saving technique: we can always sit down and actually write out the desired machine, we're just invoking CT to get out of having to do so (think of it as a really fancy way of saying "The construction of such a machine is left as an exercise for the reader").
So CT is in fact never needed for any proof. It's only ever used to shorten proofs. Its true role comes in interpretation and motivation of theorems and definitions, by connecting formal computation models with the informal-but-compelling notion of effective calculability.


How can I create an efficient MySQL database that auto-complete requests like Google

Question: I'd like to get some ideas on how I can create an efficient MySQL database that can handle high traffic auto-complete requests like Google's new auto-SERP-update feature.
The key to this is, I am trying to take the content of my book and I want to index the text in a way such that the database requests the relevant text in the quickest/least overhead possible.
For Example:
If I were to type the text: "as", I would essentially scour the database (the entire book) and see a result set for sentences in the book that say:
<code>"...that is as I was saying..."
"as I intended..."
"This is as good as it gets"
...
</code>
But as soon as I type a "k" and it spells "ask", the result set changes to (ie):
<code>"Ask your father..."
"...I will ask you to do this."
...
</code>
In addition, I was considering adding helper words, so if you are in the middle of typing "askew", but currently only have "ask" spelled, the database would grab all words containing "ask", you will see helper words like "asking", "askew", "asked", "ask".
Importantly, this book is a rule book, so it has it's own unique key for each rule. Thus, when a person types in a word or 2, all rules with that combination of words will show up in the result set.
I am willing to do any research above what exact help anyone chooses to give. I am at a loss for the kinds of keywords I should be looking for in such a subject-- so in addition to specific solutions, keywords on this type of database structure would also be appreciated and helpful.
I have read something about full-text search? Can this be a solution, or is that not efficient enough for my purposes?
I know how to do ajax calls and auto-completion already... that is not the issue I am asking for solutions for. What I need is understanding on how to structure and index the database such that when I write a script to parse the content of my book in text format, and insert the tokens into the database, it will be later pulled in the most efficient way. I expect a high level of traffic eventually on the site, so minimizing request overhead is of paramount importance.
At an initial state, I was thinking of something like tables for each character length greater than 1... thus I'd have tables called "two_letters", "three_letters", etc.
One example record in the "two_letter" database could be "as", and it has a many-to-many relationship with every rule in the book that contains "as" in it... thus:
<code>"as", "125"
"as", "2024"
"as", "4"
</code>
Of course, the smaller the letter set, the larger the database will be. This book is very big, so we're talking millions of records here! One for each combination of 2-letters, and the rule it is associated with. THEN, do it all over again with 3-letter combinations, until there are no more words. This is an initial brainstorming attempt only and may be a terrible idea, but it's my first thought on this.
Once the script is run, the database will create the tables and insert the records as it goes. It will likely read over the content many times for each length of characters.
I want it to recognize multi-word combinations as well, just as a keyphrase in Google would be auto-updated in the SERP. Thus, as the user types "they are go", you may find:
<code>"they are gone already..."
"they are going to the movies later."
"how they are gonna get there is..."
</code>
I am essentially asking for that exact auto-complete feature in Google, but the content is a book, not indexed websites on the internet.
I look forward to hearing from some of the geniuses out there that get what I'm asking for here and feel like impressing some people! :)
Thanks in advance to everyone.
Comment: Forget MySQL. It can be fast, there are full-text search solutions for it, but I think you need a more optimized solution. Start by looking for "Trie". Then follow "Automata". Build something awesome and post here about it :)
Comment: Agree with Stefan. Look for alternative solutions such as SOLR/LUCENE. It has auto suggestion and other cool features built into it.
Comment: Thanks for the pointers so far. I have actually been reading up on Sphinx and Lucerne. Not sure quite yet how they're implemented, but looks promising from a study I read on them compared against mysql.
Answer: I have to recommend Sphinx.  It's an amazing search engine for data stored in mysql (or other databases).
Answer: I second Sphinx -- I think Craigslist uses it


Switching Grand Company

Question: I am wondering about whether you can switch the grand company you have chosen or not. And if so how. I have chosen the Maelstrom and want to switch to the Order of the Twin Adder because their gear is a bit more optimized for my class (bard).
Answer: Yes, you can switch Grand Companies once you have reached the rank of Second Lieutenant by talking to an NPC in your Grand Company headquarters.
Once you switch, you will no longer be able to use any existing Grand Company gear you have, and you'll start at the very beginning rank-wise for your new Grand Company. If you reach Second Lieutenant in your new Grand Company (and at least 30 days have passed since you last switched), you can switch again if you'd like. When you switch, your old rank and company seals are retained, but you can't use them for anything if you don't currently belong to that Grand Company.
Comment: @BlueRaja-DannyPflughoeft All of your GCs retain their ranks, even when you switch around between them. So if you're a Second Lieutenant Twin Adder, you'll always be a Second Lieutenant Twin Adder if/when you ever switch back to them. The same applies to your unspent company seals.
Comment: *"When you switch, your old rank and company seals are retained"* - You mean your rank from the original GC *(which you switched away from but are now switching back to)*, or the rank from GC you originally switched to and are now switching away from?

Switching Grand Company


Why do I need software to e-file?

Question: I have a PDF of a 1040 filled out. Why can't I just email it to the IRS? Why do I have to find a company offering e-file, read their privacy and terms of service, fill out a form to register an account, and I don't know what else because I decided at that point it's easier to just print it out and mail it?
Answer: Free File Fillable Forms is the official way to submit your tax form for free electronically to the IRS.  If you already have a PDF of your 1040 filled out, you can use Free File Fillable Forms to type this information in and submit it electronically.
As to why the IRS does not simply accept PDF tax returns via e-mail, it is for security reasons.  E-mail is not secure, so by e-mailing your tax return you would be making it vulnerable to being intercepted and even potentially changed before it got to the IRS.  In addition, there would be no way for the IRS to verify that it actually came from you, and it would be completely cost free for crooks to submit as many fake tax returns to the IRS as they wanted.
Mailing in your tax return is not a big deal, either.  I still mail mine in every year.

Responses to the OP's follow-up questions in the comments:

Despite the fact that the design of the Free File Fillable Forms website looks a bit amateurish, it is in fact an official IRS service.  I don't know exactly why it is served on "freefilefillableforms.com" and not "irs.gov".
Your question above is asking about e-mailing a PDF to the IRS, and my answer explains why they cannot accept e-mail submissions.  They could, perhaps, accept PDF uploads from IRS.gov, but they instead have chosen to accept returns filed through freefilefillableforms.com, requiring you to type your information in on their site.  By making you jump through a few hoops to submit your return (which you should theoretically only have to do once a year), they make things much more difficult for a scammer, who would have to jump through the same hoops every time they wanted to submit a fraudulent return.  If it is too easy to submit your one return, it is perhaps too easy for a scammer to submit thousands of returns.
Comment: What security features does submitting through HTTPS at IRS.gov with identity verification lack, that e-file and a paper form have? You just gave me link to a website I know nothing about. Clicking on random links is more secure than submitting things through the IRS website? What is "Free File Fillable Forms"? Is a specific software? A class of software defined by some standard? Why doesn't the IRS just host the software, instead of forcing people to use a tax company as middle man?
Comment: @Acccumulation I have expanded my answer to address your follow-up questions.
Comment: "E-mail is not secure" -- What about PGP signed emails?
Answer: It's pretty straightforward, really.  You will be actually filing instead of "agreeing to use a data interchange service in lieu of filing". Filing has legal force, which is why they stand on the formality of paper.  Not least, IRS cannot reject a filing as they can with e-file, they can only disagree, so you can't be tardy with real filing.
1 -- Print the form.
2 -- write your Social Security number on all pages that ask, and sign it.
3 -- Put it in an envelope
4 -- put stamps on it
5 -- Leave it for your mailman to take if secure, drop in any mailbox, or take it to the Post Office.

If you are overseas, unfamiliar with mailing, have full sheet-sized envelope, or more than 3 sheets of paper, you may need help or more than the normal single stamp.  If that's the case:

Get in line and take it to a postal clerk.  It'll be less busy on weekdays, earlier in the day, and in sleepy small-town post offices.
Weigh the package yourself and ask your nation's post office website (e.g. USPS.com) what the postage will be from there. You are allowed to overstamp it, so if you have $1.39 postage just use 3 common stamps.
In the US, take it to the post office and buy your postage at one of the machines that weigh your envelope and has a dimension chart.
You can also consider services like Certified Mail that will prove the IRS received it.  You must pay extra for the green paper card: the web-based delivery confirmation service is worthless because it's only archived for 90 days, and IRS disputes are slower than that.

Why do I need software to e-file?


Is There A Way To Find End Ships Quickly Without Using Cheats?

Question: So I had successfully killed the Ender Dragon. I used the ender pearls and threw them in those small portal things. I had found a few end cities, but no ships. Is there a way so that we could find them more quickly?
Answer: Every single end city has a fixed chance to spawn with a ship. Sadly the only things that you can use without using any external tools is the way the cities themselves spawn.
Since most of the time they spawn kind of in a line. So once you have found one city you should try going going along the axes of the world. Meaning you should go strictly north, east, south or west. very often you will find an end city within a few hundred blocks of distance.
There are tools you can use to look up where the cities are (i.e. chuckbase end city finder) but there is no simple way to finde ships specifically.
Comment: Chunkbase end city finder has an icon on where the end cities are showing whether the city has a ship or not.
Answer: There is no way to do this without cheats unfortunately
Answer: well you could copy the world and then go to creative mode and put in chat "/locate end_city_ship
then it will say the cords then you take down the cords on a notepad or something then delete the copy of the world then go to your original world and go to the end through the end portal and go to the coordinates that you took down
this is a method but it could be classified as cheating
Comment: Using creative mode sounds like using cheats.


Sentences in passive voice that don't use "by" for the agent

Question: I was being asked to write sentences in the passive voice, and one of the requirements was to use prepositions aside from "by" for the agent. Is that possible? Some examples would help. Thank you in advance.
Comment: No, "by" is the only preposition.
Answer: One can engineer passive sentences where by can be replaced with via, through or using, but I can only think of examples where the agent was already identified with an instrument.

The rescue team was brought in by helicopter.
Which means:
A helicopter brought in the rescue team.

You might disagree and argue that what happened was that A pilot brought in the rescue team in a helicopter, and the agent is the pilot, not the helicopter. But these sentences are correct:

The rescue team was brought in using a helicopter.
The rescue team was brought in via airlift.

Other similar examples:

Internet connection on this remote farm is provided by/via microwave.
Construction of the new prison is financed by/through property taxes.

Again, in both cases one can argue that the agent is the internet service provider not the microwave, and the city council not the taxation.
Answer: You can write sentences in passive voice without explicitly referring to the subject/agent. For example, 'the ball was rolled through the tube'.
I don't think there are any other words that explicitly ascribe agency to a subject the way the word 'by' does. Instead of writing, 'a goal was scored by the red team', you could write, 'a goal was scored for the red team' or 'a goal was scored due to the unrelenting tenacity of the red team' but the change in preposition fundamentally alters its meaning and shifts the agency of the sentence.
Comment: I hear you. Prepositions can change meaning, so I thought what was asked of me is impossible. I tried thinking of alternatives but to no avail. Anyway, thank you for the enlightenment :)
Comment: "The ball rolled through the tube" is not passive.  "The ball ***was*** rolled through the tube" is passive.
Answer: I'm not sure whether, in your question, for the agent modifies prepositions or "by" only.
If the latter (not "former", as pointed out and corrected) is the case, here's an example from Oxford Advanced Learner's Dictionary:

He was too preoccupied with his own thoughts to notice anything wrong.

From  Macmillan English Dictionary:

Daniel was robbed of his car, briefcase, and mobile phone.
Comment: In the first example, I believe that's not an agent—it's an instrument. (Compare the sentence "he was hit with a branch by a dog" which has both an agent and an instrument.) The second is not an agent either (if it were the agent, the active would be "Daniel's car, briefcase, and mobile phone robbed him.")
Comment: Right, they are *not* agents. I meant "latter", not "former". Thanks.
Answer: Whatever preposition used instead of by can be argued as not related to the agent of the action.
Examples:
I have been invited via an email.
I have been informed of it on phone.
In both these sentences, there is still the absence of a real agent of the actions.
I can find the only preposition that can be used to relate to the agent of an action other than by is through in a sentence like:
My ticket has been confirmed through the agency appointed by the airlines.
Here the agent of the action of confirming is the agency, not the airlines. The airlines can be said to be the agent of the action of appointing the agency.
Instead of a preposition, a prepositional phrase such as with the help of may be helpful as in:
My decayed tooth was removed with the help of a dentist.