Translate book-length text to mp3 audio

Question: I have a 70 chapter book that I need to have read aloud to me. My sight is failing after 45 years. I need book.txt translated to book.mp3.
Comment: You might want to look into DAISY books. https://openlibrary.org/help/faq/accessing You can also install a DAISY reader on Ubuntu by running the following command: `sudo apt install daisy-player` Some books are copyright protected and for these books, you may need to apply for NLS service to obtain a key https://www.loc.gov/nls/enrollment-equipment/apply-for-nls-service/ or you can call 1-800-424-8567 for help. You must be a United States citizen to apply for a key but a key is not always required.
Comment: https://en.wikipedia.org/wiki/DAISY_Digital_Talking_Book
Answer: First, run the following commands to install the dependencies:
sudo apt update
sudo apt install lame espeak

Next, run the following commands to convert the file from text to wave to mp3:
espeak -s 155 -a 200 -f book.txt -w book.wav
lame -V2 book.wav book.mp3

If you don't want the wav file you can delete the file.
The espeak command options set the speed of words per minute to 155 and the amplitude to 200.
Use espeak --help for more options.
Comment: Just found this!  Alz, ?...  --{worde than death.}  For the record, I pieced things together and used the info above to create a scipt that works fine.
Answer: If you have a dual boot, try using Balabolka .. Or borrow a friend's computer.
The official website (be careful) is http://www.cross-plus-a.com/balabolka.htm
Balabolka does work in Wine but it is 32bit so follow the instructions.
I think I used this webpage to follow the directions..
https://www.reddit.com/r/linux/comments/6z41qb/my_text_to_speech_tts_solution_wine_microsoft/
The content from that page is:
The Solution. It was surprisingly simple. Download the 32bit version of SpeechPlatformRuntime.msi from https://www.microsoft.com/en-us/download/details.aspx?id=27225 and MSSpeech_TTS_en-US_ZiraPro.msi from https://www.microsoft.com/en-us/download/details.aspx?id=27224 this should work with the other voices as well.
$export WINEARCH=win32
$export WINPREFIX=~/.wine32
$winetricks msxml3
$wine msiexec /i SpeechPlatformRuntime.msi
$wine msiexec /i MSSpeech_TTS_en-US_ZiraPro.msi

After that you should be able to use any windows tts program that uses Microsoft Speech Platform v11. I use Balabolka's Command Line Utility http://www.cross-plus-a.com/bconsole.htm it's a simple console app and doesn't require any extra dependencies.
Answer: There are many online services that let you convert a TXT file to MP3.
for example:
https://onlineconvertfree.com/convert-format/txt-to-mp3/
There are many others.
If you want to be able to do this offline, you can write a simple python sript, see this discussion:
https://stackoverflow.com/questions/19683282/how-can-i-convert-a-text-file-to-audio-mp3-using-ffmpeg-on-ubuntu-11-04

Translate book-length text to mp3 audio


Should a sign up for two different accounts be split into two pages?

Question: Let's say there is a sign up for merchant and customers. Is it okay if I make the sign up page for the both of them on one page? I added an image here as an example. The sign up is for merchants and the log in is for customers.
Comment: Related: https://ux.stackexchange.com/questions/97803/user-login-and-signup-for-app-with-multiple-but-separate-roles
Comment: "The sign up is for merchants and the log in is for customers." - you mean it is currently implemented this way? It seems confusing this way and doesn't make any sense.
Answer: Well keep a single form for both of them just differ them on the basis of type like a dropdown with merchant or customer option on sign up. And while signing in, maybe a checkbox maybe which says want to login as a merchant. Depends which one do you want to show as default.
Secondly, apart from this, Don't just give placeholders for input fields because while typing they would disappear. From UX perspective, it is better if you give label on top of the field for better readability.
Comment: so in conclusion, is it better to split the pages? i'm sorry i really confuse what is more effective:(
Comment: You can split as well to have different pages altogether for both but the user can be customer or merchant both at the same time, right? Having separate pages means they know they are on specific url (customer or merchant). Having both on single page allows them to be able to just go to single url and switch /select the relevant role and log in.
Comment: "From UX perspective, it is better if you give label on top of the field for better readability" - what is your evidence for that? Placeholders in input fields make the form seem less cluttered and therefore easier to fill. Judging from personal experience I have not noticed any problem with placeholders.
Answer: No, it should not be a different form. let them signup and just ask the primary role in the form itself. and if it is something where a single user can play different roles then there should be option to switch roles after the login.


Find similarities in two layers in Gimp (like opposite of difference)

Question: I have two (actually more) images in layers, that share the background (an image of a book page), but differ in the text on the book page. The text is in english. I want to translate the text and display it on the page instead. So what I'm trying to achieve is to get a blank book page. My idea is that I take multiple of these pictures and find the common pixels, while erasing the differences.
I tried changing the layer mode (essentially went through all the options), but no option returned a good result. The best one was Lighthen only, since the text is black, but then the background image broke in other places.
Logically, I would need the opposite of Difference.
Do you have an idea?
Answer: I would use a different technique to remove text from a page. This works quite well for a page with some texture/shading on it, although you might need to do some manual Clone Stamp retouches afterwards. Obviously success may depend on your image, but since you didn't share it, I'll use one I found online.
The Heal Selection (Resynthesizer) plugin is available here.
Here's an example:
Make a tight selection around the text using the Free (Polygon) Select tool.

Do Filters > Enhance > Heal Selection, here I set the sampling pixels to 60, but left everything else at defaults. If you have a large image it might take a few minutes, but worth the wait.
Here's the result

You can break up the patchiness using the Clone Stamp tool, set to a large soft edged brush and low opacity.
Here's the final result. When you you put knew text on this, it will help break up any inconsistencies even further.
Answer: The best way to do this is to use a Median filter. There is one in the GMIC filter suite plugin: given a set of overlapping similar images (in layers) it generates an image where each pixel is the most frequent pixel value(*) across the layers. This filter is often used to remove people from images of buildings, by taking several shots of the building.

If the text is white or black, an alternative is to set all layers to blend mode Darken only (for white) or Lighten only (for black). Between two layers where one is the plain background and one has black text, the Lighten only will make Gimp keep the lighter of the two pixels, and since black is darker than anything, Gimp will keep the non-text pixel.

However, with either technique you can have pixels that correspond to text in most/all images...
(*) technically, their median, but in this use case the result is usually the most frequent
Answer: What if you actually use "Difference", and work on it to be used as a mask?
You can convert it to grayscale and probably invert the curves. A blend mode is a tool; the result might not be exactly the one you need, so adapt it.


Why price always increase?

Question: My question is why price of goods and services always increase
Is it a law like (entropy always increases) .
But in electronics price always decrease.
Comment: "Always" is too strong a word here
Answer: First, your statement is not factual and contradictory.

Electronics are goods so both statements you make cannot be true.

Price of goods and services do not always increase. There are many goods and periods of time for which prices decline, even outside electronics. For example, price of natural gas in EU between Sep 2022 and Jul 2023 declined as data show.

You maybe meant to ask about average prices/CPI, but average prices also do not always increase. For example, in the US average prices declined rather sharply after 2008, and there were also various other periods of time where prices declined as data show.

However, prices tend to increase over time on average. This is just trend/tendency not an iron economic law as you suggest.
The reason for this trend is that in most countries central banks on purpose pursue policy that leads to inflation, as economists generally believe low inflation, i.e. increase in prices, (inflation in ballpark of 2%) is good for an economy. As a result governments, or to be more specific central banks, consciously pursue monetary policy that tries to engineer low inflation, even in situation where prices would decline if economy would be completely left to its own devices.
However, to engineer inflation you only need to pursue monetary policy that makes prices increase on average. If economy would be completely left to its own devices prices of goods that become more abundant or easier to produce or less in demand, ceteris paribus, would decline, while prices of goods that are becoming more scarce or harder to produce or demanded, would raise. Monetary policy can affect these prices through making money less valuable thus making prices higher than they would be if value of money would not change. However, since policy only tries to target average prices if some goods or services experience price decline that is faster than decline of value of money, the prices of such goods will still decline, although less so than they would in absence of any policy.
Electronics is a category of goods where there is constant rapid innovation. For example, there is empirical tendency of number of transistors on chip of same size to double roughly every two years (e.g. see Moore's law). As a result of this and other advancements, that allow firms to produce more electronics with same/similar resources prices of these declines, and because the progress is so fast the prices tend to decline faster than value of money drops.
Comment: Your answer is mostly very good but I'd like to nit-pick one sentence, "Monetary policy can affect these prices through making money less valuable" - this is like saying "we made it bigger by making it bigger"... Did you actually mean "Monetary policy can affect these prices through making money more/less plentiful"?...
Comment: money becoming more or less valuable is consequence of them being more or less plentiful, I focused on the downstream consequences in that sentence

Why price always increase?


X-ray characteristic radiation

Question: A high speed electron knocks an orbital electron in the atom. This collision creates a vacancy that is filled by an electron from a higher energy level. My question is, what happen with both electrons after the collision? (high speed electron and the knocked electron)
Comment: Off we go, into the wild blue yonder... Eventually they land jobs filling orbitals around other atoms.
Comment: Or somethimes they have to moonlight ... taking part-time jobs in several atoms that form a vertical trust^W^W benzene ring.
Comment: @JonCuster at should be an Answer.
Comment: They also emit photons during these changes.
Answer: Its a  many particle interactive  system and electrons are being knocked out from many such atoms  from various shells-
they can be caught by some other atoms if a suitable place is available in their arrangements or
get out loosing their energies by collision /radiation  and  transforming to mainly thermal energies.
The efficiency is at a level  that only 1%   of the total energy input  gets back as X-rays.
The Tube target  is to be cooled continuously  by water  otherwise the target can melt so a lot of energy of electrons convert to heat and electromagnetic radiation.

X-ray characteristic radiation


Were the Old Testament prophets married?

Question: Were Elijah, Isaiah, Jeremiah and Ezekiel married? There is no mention for them, whilst there are for Moses
Comment: If there isn't any mention of a wife in the Bible, it is because the mention of the Prophets were only included because understanding of their persons is crucial to the understading of what they did as well those acts' place in Salvation History. Who they were married to has nothing to do directly with Salvation History.
Answer: Were the Old Testament Prophets Elijah, Isaiah,  Jeremiah and Ezekiel married?
The short answer is yes and no.
As for the Prophet Elijah, the answer is we simply do not know.
The Scriptures do not mention one way or another if the Prophet Elijah was married or not.
The Prophet Isaiah was certainly married.

Isaiah was the 8th-century BCE Israelite prophet after whom the Book of Isaiah is named.
Within the text of the Book of Isaiah, Isaiah himself is referred to as "the prophet", but the exact relationship between the Book of Isaiah and any such historical Isaiah is complicated. The traditional view is that all 66 chapters of the book of Isaiah were written by one man, Isaiah, possibly in two periods between 740 BC and c. 686 BC, separated by approximately 15 years, and includes dramatic prophetic declarations of Cyrus the Great in the Bible, acting to restore the nation of Israel from Babylonian captivity. Another widely held view is that parts of the first half of the book (chapters 1–39) originated with the historical prophet, interspersed with prose commentaries written in the time of King Josiah a hundred years later, and that the remainder of the book dates from immediately before and immediately after the end of the exile in Babylon, almost two centuries after the time of the historical prophet.
The first verse of the Book of Isaiah states that Isaiah prophesied during the reigns of Uzziah (or Azariah), Jotham, Ahaz, and Hezekiah, the kings of Judah (Isaiah 1:1). Uzziah's reign was 52 years in the middle of the 8th century BC, and Isaiah must have begun his ministry a few years before Uzziah's death, probably in the 740s BC. Isaiah lived until the fourteenth year of Hezekiah's reign (who died 698 BC). He may have been contemporary for some years with Manasseh. Thus Isaiah may have prophesied for as long as 64 years.
According to some modern interpretations, Isaiah's wife was called "the prophetess" (Isaiah 8:3), either because she was endowed with the prophetic gift, like Deborah (Judges 4:4) and Huldah (2 Kings 22:14–20), or simply because she was the "wife of the prophet". They had three sons, naming the eldest Shear-jashub, meaning "A remnant shall return" (Isaiah 7:3), the next Immanuel, meaning "God with us" (Isaiah 7:14), and the youngest, Maher-Shalal-Hash-Baz, meaning, "Spoil quickly, plunder speedily" (Isaiah 8:3).

The Prophet Jeremiah was forbidden to marry.

Jeremiah Forbidden to Marry
16 The Lord gave me another message. He said, 2 "Do not get married or have children in this place. 3 For this is what the Lord says about the children born here in this city and about their mothers and fathers: 4 They will die from terrible diseases. No one will mourn for them or bury them, and they will lie scattered on the ground like manure. They will die from war and famine, and their bodies will be food for the vultures and wild animals."

The Prophet Ezekiel was equally married.

What is known of Ezekiel is derived solely from the book that bears his name. He was among the Jews exiled to Babylon by Nebuchadnezzar in 597 b.c., and there among the exiles he received his call to become a prophet (see 1:1–3). He was married (see 24:15–18), lived in a house of his own (see 3:24; 8:1) and along with his fellow exiles, though confined to Babylonia, had a relatively free existence there.
He was of a priestly family (see NIV text note on 1:3) and therefore was eligible to serve as a priest. As a priest-prophet called to minister to the exiles (separated from the temple of the Lord with its symbolism, sacrifices, priestly ministrations and worship rituals), his message had much to do with the temple (see especially chs. 8–11; 40–48) and its ceremonies.
Ezekiel was obviously a man of broad knowledge, not only of his own national traditions but also of international affairs and history. His acquaintance with general matters of culture, from shipbuilding to literature, is equally amazing. He was gifted with a powerful intellect and was capable of grasping large issues and of dealing with them in grand and compelling images. His style is often detached, but in places it is passionate and earthy (see chs. 16; 23).
More than any other prophet (more even than Hosea and Jeremiah) he was directed to involve himself personally in the divine word by acting it out in prophetic symbolism. - Ezekiel
Answer: Jeremiah was forbidden to marry in Israel. It clearly says not to marry in this place. It has no mention of you cannot marry. It clearly states that he is forbidden to marry in a specific place, which we can clearly assert as Israel. So Jeremiah serving the king of Babylon, and the king of Babylon Acknowledged that he was a prophet that served his political interests, says prophecies that said Babylon would destroy Jerusalem and such. Meaning the king did not hold him captive. After those facts Jeremiah could have been married to a Babylonian woman.
Comment: Welcome to Christianity Stack Exchange.  Please take our Tour to find out how we are different to other sites and what we look for in a well-researched answer: https://christianity.stackexchange.com/tour


Is there a single word for "lack of communication/coordination"?

Question: Example:

The accident happened due to a lack of communication (or coordination) between the parties involved.
Answer: Miscommunication — Cambridge

noun Failure to communicate ideas or intentions successfully
"A spokeswomen blamed the confusion on miscommunication between the company and its customers."
Answer: Perhaps disconnect (Cambridge)

A situation in which two or more things are not connected in the way
  that they should be.

better indicates the missed opportunity to communicate, if that's your intention.
Breakdown also sometimes gets used in this sense, though the assumption that it refers to communication (rather than, for instance, their automobile) may be a little more ambiguous in certain situations or audiences.
Answer: Confusion has a couple definitions along this line: [Merriam-Webster]

a situation in which people are uncertain about what to do or are
  unable to understand something clearly

and

the feeling that you have when you do not understand what is
  happening, what is expected, etc.

So it would be: "the accident happened due to confusion between the parties involved."


what is good (stackexchange) form for questions?

Question: I wind up on these pages a lot when searching from google and the like. I see a lot of questions closed as off-topic. That doesn't feel very welcoming for this uninitiated pseudo-nerd. I'm pretty sure this is a friendly community. Can you point me to why so many search results seem like they are flamed closed?
Comment: Hello and welcome! Not to intentionally be unwelcoming, but this is more of a meta question rather than hardware/software related: https://meta.superuser.com/
Comment: Questions being closed are an opportunity for the author to improve a question that otherwise would be deleted.  A question being closed, shouldn't be taken personally, as the action is against the question not the author.
Answer: The reason these sites are helpful is that they are kept on-topic by trusted community members. More often than not, off-topic questions aren't ignored... they are migrated to another forum of the Stack Exchange where they can be better answered by people more familiar with that topic. A topic that is closed as off-topic probably isnt suited for any question-answer site. This is a question-answer site... It is not a do-my-homework-site, nor a help-me-I-have-no-clue site. We are not here to provide you with generalized information (i.e. Where can I learn more about foo?), when a  quick google search can give you that.
Not all of these types of questions are bad... they just don't belong here. You don't expect Netflix to send you sandwiches. Sandwiches aren't bad, they just aren't in Netflix's scope.
Hope this helps... FYI this question is  super off topic, and will most likely get migrated to Meta Stack Exchange... Not because its a bad question or we are unfriendly, just 'cause it doesn't belong here.


Why is the sound of running water soothing?

Question: What is it about the sound of running water that soothes the brain and the soul?
This is what I found on the internet:

Our species evolved where trees met savannahs and where freshwater
  sources were present. Our brains are deeply encoded with the love of
  water – we revel in the delicious feel and noise of burbling brooks…

and

I personal think we LOVE the sounds of running water because inside
  the womb of our mothers, that's what we hear...along with the sounds
  of her beating heart. I was told that we hear the blood running
  through her veins in utero.
Comment: A researcher at out institute studying the effects of mindfulness mediation said that rain and other natural water sounds had strong alpha waves, inducing alpha wave activity in the human brain (which are correlated to relaxed, meditative states). I have no published source for this, but maybe you can find something with this hint.
Comment: Could you please add links to those quotes? Who are you quoting from what context?
Comment: I think something to consider on top of the other answers is association with being in utero. I think that being immersed in liquid while your brain and senses are just developing as a fetus must have **some** effect on you.
I have no evidence to back this up, but it's a theory, and hopefully someone else can elaborate on this further.
Comment: The sound of a waterfall falls in the category of Red noise, where the power of the sound with frequency falls with increasing frequency as $ \frac{1}{f^2} $. If the power increases with increasing frequency, it is called blue noise.
You can read more of it here:
https://driftspeed.wordpress.com/2016/07/20/on-the-colors-of-noise/
Comment: My answer is a practical experience. I came across a video yesternight - https://www.youtube.com/watch?v=NlIcKqbYRmk - and meditated on it. I feel that running water is directly related to our body composition which is majority water. The running water sound activates the vessel of our body water and blood and makes rise our Prana energy, our life force from all parts of the body, from our feet to upwards and upwards in a regular flow towards our Sahastrar, the Crown Chakra. .....and any process or sound which takes us and helps us reside at our Crown Chakra gives a Divine and surely a soothin
Answer: There cannot be a single answer to this question which would be entirely correct. Different theoretical approaches to psychology will yield different explanations. This is evident from the other answers in this question (some which you provided) which all stem from different theoretical accounts:

Evolutionary Psychology: Species evolving around water
Developmental Psychology: Prenatal development in womb
Sensory and Perception Psychology: White noise account
Behaviorism, specifically Classical Conditioning: We develop a learnt association between the sound of water and relaxation.
A prediction based on a cognitive science approach is less clear in my opinion. It would likely stem from a combination of sensory arguments (white noise) and from neural networks of association.

Why do we see so many different accounts for the same phenomena? Firstly, it is difficult to produce a falsifiable explanation for why such a perverse qualitative effect exists. In order for any given explanation to be scientifically valid, it has to be able to be tested. The explanations provided so far do not generate meaningful hypotheses which we can test using experimental studies. Therefore, it is difficult to form a single model accounting for why we find water sounds relaxing. Consequently, we see a range of explanations with little evidence for any of them (they are all just untested just-so stories). Note, even some of the better responses, such as this one (linked above), do not provide falsifiable or testable answers.
A second reason we see such variation could be that there is no simple answer. The "true" answer probably will draw upon a wide range of reasons for this phenomena. In this way, perhaps the best explanation at this point is that there are a variety of reasons why certain individuals find water sounds relaxing (those aforementioned). Although perhaps not the most satisfying conclusion - it is likely the most accurate.
Answer: It may have something to do with the manner in which the water flows. Disturbed or moving water has a frequency content/distribution that approaches noise (think ocean waves lapping up against the the shoreline/beach, which is close to white noise).
Our hearing system tends to tune out when presented with white noise, mainly due to there being no discernible pattern in the sound for the hearing system to focus on. The mind then starts to drift (excuse the pun) ...
Answer: I think the answer to this is on a question I did some time ago:
Why does being in a natural environment induce some kind of "peace" state while mecha/tech ones induce the opposite?
We feel relaxed when listening to the sound of water, because we associate the sound to something like a beautiful waterfall, and to waterfalls/nature, the majority of us will associate peace, water has always been good to us, drinking water for example. Another example of "the things we use to consider good are the things that make us feel good" is the sound of birds telling there is no danger around, as Randy mentions in his answer to that question.


What is a British English equivalent to 'Fussbudget'?

Question: Lucy from Charles Schultz's Peanuts strip is often described as a 'fussbudget', for example here: 'Lucy: Fussbudget to Feminist'. What is a British English equivalent to 'fussbudget'?
Answer: Fussbudget
noun US informal, old-fashioned.
(UK fusspot)

a person who is often not satisfied and complains about things that are not important:
"I can't eat this meat - it's too tough." "Stop being such a fussbudget and eat your dinner!"

(Cambridge Dictionary)
 Fussbox  is another AmE variant:
(Southeastern U.S.)

a fussy or needlessly fault-finding person
Also called: fussbudget

(Collins Dictionary)
Comment: I have tried to edit this to the correct format and quotation from Cambridge Dictionary but failed. Anyone else care to try?


What is the difference between HLS and MPEG-DASH?

Question: It seems both protocol does the same thing but is there a advantage of one over the other?
Comment: I haven't seen HSL vs. DASH comparisons yet, but for me those 2 editorials from Streaming Media were enough to get the picture: - What is HLS: http://www.streamingmedia.com/Articles/Editorial/What-Is-.../What-is-HLS-(HTTP-Live-Streaming)-78221.aspx - What is MPEG DASH: http://www.streamingmedia.com/Articles/Editorial/What-Is-.../What-is-MPEG-DASH-79041.aspx If someone finds actual comparisons, I'd appreciate it as well.
Comment: Here's a bit on comparison...

Web Standards:  Of the two adaptive streaming protocols MPEG-DASH has the best chance of becoming the unifying standard.  HLS, being older and with Apple pushing hard behind it, has more support especially in older browsers/os/devices.  HLS now, MPEG-DASH tomorrow.  The following article is a good assessment of the fractured state of streaming technologies today: http://blogs.imediaconnection.com/blog/2012/04/27/mpeg-dash-its-time-for-apple-to-put-up-or-shut-up/
Answer: You should ask yourself what is important to you (encoding, encryption methods, standardization, etc.)
Jason Schneid wrote an excellent comparison: http://www.internetvideoarchive.com/IVA/news/2012/09/13/progressive-download-vs.-adaptive-bitrate-how-to-choose-the-format-right-for-you
Comment: This link has been updated and moved: http://www.internetvideoarchive.com/documentation-2016/video-api/progressive-download-vs-adaptive-bitrate/
Answer: Here's a quick comparison for Aquary.  Too long for an inline reply...
Web Standards:  Of the two adaptive streaming protocols MPEG-DASH has the best chance of becoming the unifying standard.
Support: HLS, being older and with Apple pushing hard behind it, has more defacto support especially in older browsers/os/devices.  You can support HLS on windows machine by using the jwplayer.
Performance:  Not sure but the makers of bitdash, an mpeg-dash player, make this claim: "streaming performance is 53% higher compared to Microsoft Smooth Streaming and 101% higher than Apple HLS".
Conclusion: HLS now, MPEG-DASH tomorrow (and now if you can manage it).  The following article is a good assessment of the fractured state of streaming technologies today: http://blogs.imediaconnection.com/blog/2012/04/27/mpeg-dash-its-time-for-apple-to-put-up-or-shut-up/
Comment: At the end of the day its best to support multiple streaming technologies but if you have to pick one or prioritize which to go with first then HLS is still the choice because Safari (the defacto browser on iPhone's and iPads) does not support MPEG-DASH.  As a result HLS was by far the dominant encoding format in 2017 and 2018...
https://bitmovin.com/whitepapers/Bitmovin-Developer-Survey.pdf
https://www.encoding.com/files/2018-Global-Media-Formats-Report.pdf
Answer: MPEG-DASH is a vendor independent, international standard ratified by ISO/IEC MPEG. Previous adaptive streaming technologies - such as Apple HLS – have been released by vendors with limited support of company-independent streaming servers as well as playback clients. As such a vendor-dependent situation is not desired, standardization bodies started a harmonization process, resulting in the ratification of MPEG-DASH.
In the recent years, MPEG-DASH has been integrated into new standardization efforts, e.g., the HTML5 Media Source Extensions (MSE) enabling the DASH playback via the HTML5 video and audio tag (in contrast to Apple HLS which depends on FLASH on platforms outside of the Apple ecosystem), as well as the HTML5 Encrypted Media Extensions (EME) enabling DRM-protected playback in web browsers. Furthermore, DRM-protection with MPEG-DASH is harmonized across different systems with the MPEG-CENC (Common Encryption), and MPEG-DASH playback on different SmartTV platforms is enabled via the integration in HbbTV 1.5 and 2.0.
While MPEG-DASH is codec and container agnostic Apple HLS is, e.g., bound to the MP2TS container. There are also many more differences.
Comment: That bitcodin link is very misleading. I wrote the Motorola HLS chunker 5 years ago, and even back then, when the HLS spec was just 17 pages long, it ticks almost every box that that blog post implies it is missing.
Comment: I don't think that the second paragraph is particularly accurate at the beginning. MSE and MPEG-DASH are separate structures that go through different standardization processes, and want to allow for completely different structures. It is true, that many of the same folks are involved in both, and they are complimentary, but to imply that this is untrue of other competing groups is unfair and biased.
Answer: From an application designer point of view, trying to choose one technology for video streaming services like youtube or netflix, I would say they all have theirs fall backs and you should use all of them.
Every regular video streaming service today will have two problems: client support (and you should want everything, from Smartphones, to tvs, consoles, apple tv and google chromecast) and server infrastructure.
HLS is native supported on everything Apple, runs very smooth and offers great personalization through the use of a lot of open source js video players. Android has problems, but even on 2.3 devices I have made flash player run HLS on a hybrid application. Performance sucks. But you can transcode on the fly with ffmpeg! Live streaming is also possible and very straight forward.
MPEG-DASH is really well supported on newer devices, in 5 years this talking could be over. With ngnix and rtmp extension you can build a video streaming server in half an hour.
I first chose HLS beacuse it's easy. Right now I'm creating everything HLS, WebM (lower definitions) and MPEG-DASH at the same time for different clients to allow all of them to run natively.
That way I can rely on building only Hybrid applications and use all of my AngularJS code on every client. Otherwise it would be impractical for smaller projects to embrace video streaming services. Then you have services like Wowza.
Comment: I am curious why you are choosing WebM over MP4?


Where have the Privacy Settings gone in WordPress 3.5?

Question: I moved a WordPress site to another server and everything is working well, minus the fact that I can't seem to change the settings in Privacy. When I click on "allow search engines to index this site", the radio button automatically switches back to "ask search engines not to index this site". Also, the Privacy Settings menu itself is gone from the Settings menu. I have to manually type in /wp-admin/options-privacy.php to access the page. Can anyone tell me what is going on?
Answer: The privacy page was removed in WordPress 3.5. Go to wp-admin/options-reading.php and set search engine visibility there.
Answer: Is in "Settings > Reading page > Search Engine Visibility".
For more details see this blog post.

If you are developing your WordPress site and don't want it showing up in search engine results, the WordPress team thoughtfully added a setting for site privacy. You get to decide this when you first install your self-hosted site, but you can change the setting after the fact.


A deep learning approach that can calculate distance to obstacles

Question: After reading about the most famous object detection CNN based methods: YOLO, YOLO 9000, r-cnn, faster r-cnn, etc., I was wondering if there is an architecture that can calculate the distance to the obstacle after detection?
Thank you.
Answer: Actually, I don't think this is a problem that could be solved just from the image because it could be a small object that is really close or and big object really far. As far as I know, self driving cars use sensors for this. From what I found here, you would need the actual height of the object to calculate it from one image.
I strongly suspect you could also calculate the distance by having two images and then using the distance between the two cameras, and the Pythagorean theorem to calculate it. But that's just conjecture.
Comment: CNNs can distinguish objects from each other, how is that different from learning that distances could change depending on what kind of object it is? You can estimate the distance based on what type of objects they are, right?
Comment: @hbdz that's easier, you can use car's average height, it doesn't differ that much except in the case of special vehicles or trucks. But you can use the height of a regular car as a baseline and then extrapolate from there. Then you follow the first link I gave you about calculating the distance knowing the height, should be a good approximation.
Comment: I am using this for Self Driving Cars what do you think I should do for this case ?
Comment: Using two cameras and the pythagorean theorem is called stereo vision, and is a common way of estimating distances. It is very similar to binocular vision in animals.
Answer: As far as I am aware there are no direct architectures that solve this at this moment in time, but I don't think this is a big issue for CNNs in general. For your training set you could choose to either train directly to estimate a distance if it's always the same object or if there are multiple objects and you want to detect them you can add the distance to the loss function. You need to tune the weighting between these two different objectives however and it might not be obvious how to do this if you don't know how these object detectors work.
EDIT: Based on your additional information:
It mostly depends on the training data you have available, if you have historical distances between the camera and the vehicle then I think a system like I proposed will work significantly better because it allows you to train the network end-to-end.
I could imagine you only have bounding boxes, then you might need to find a different solution, either by approximating the size of the car (by identifying the type of car for example) and using the size of the predicted bounding box as an indicator for how far away it really is. Different cameras might make this tricky due to different types of distortion.
Comment: I added some information based on this
Comment: I am using this for Self Driving Cars what do you think I should do for this case ?


Display search results within the same page in wordpress

Question: How can I display the search results on the same page where I have put search form?
Answer: Can you explain how did you put the search form? Are you working in code or with any page builders?
Assuming you are using code, best case is to use Javascript / Ajax to search in the same page.
Other options include submitting the search form and reloading the page with data. You can add form submit action like this to submit your search form to the same page.
<code> <form method="post" action="<?php echo esc_url($_SERVER['REQUEST_URI']); ?>">
    // your search input here
 </form>
</code>
Then in the same page, you catch the form submission like this and show the results.
<code>if ($_SERVER['REQUEST_METHOD'] === 'POST'){
    enter code here
}
</code>


Ruled surface out of lines of curvatures

Question: I'm trying to proof the following statement:
Let $c$ be a curve inside a surface element $f:U\rightarrow\mathbb{R}^3$ (i.e $c=f\circ\gamma$ where $\gamma:I\rightarrow U$). Then $c$ is a line of curvature iff the ruled surface $g$ defined by $f$'s surface normal $\nu$ along the directix c is developable.
To make it clear- $g$ is the ruled surface created out of the normal vector of $f$ sliding through the curve $c$.
Both conditions have many equivalent definitions. For the first condition I thought using that $c'$ is an eigenvector of the shape operator $L$. For the second condition I thought of either using that the normal vector of $g$ doesn't change along $\nu$ or equivalently that the Gaussian curavture of $g$ vanishes.
Any ideas for solving this?
Also hints are welcome, but please make them helpful enough!
Answer: You should prove that the ruled surface $x(s,t) = \alpha(s)+t\beta(s)$ (say, with $\|\alpha'\|=\|\beta\|=1$) is developable if and only if $\alpha', \beta, \beta'$ are everywhere linearly dependent.


how i am able to select contact in campaign report

Question: Campaign is not directly related to contact but when i try to create a report type after selecting the campaign directly i am able to select contact object. can anyone please explain how i am able to select contact directly under campaign?.
Answer: as far as i know, i think you created the campaign member but not campaign.
Please refer this link under USAGE headings,
https://developer.salesforce.com/docs/atlas.en-us.api.meta/api/sforce_api_objects_campaignmember.htm
Answer: I think its feature provided by Salesforce to reduce the report creating effort of admins.
The relationship is like
Campaign  <--- Campaign member (junction member) ---> Contact / Lead
So ideally we should have option to select only Campaign member (junction member) but for better usability Salesforce have provided Contact / Lead as option which is more meaningful and useful .


Why was my dishwasher hardwired directly to a switch box?

Question: I was removing my dishwasher today, and to my surprise I saw that it was hardwired directly to a switch box with the switch taped in the on position with electrical tape. Any ideas why on earth it was done this way?? It's already on its own circuit (which I turned off before uninstalling the DW).
Comment: Why did they do it? You'd be surprised how many people know what things "should look like" but don't understand why. It likely never crossed the original installer's mind that the reason cords aren't supplied with dishwashers, ovens, dryers, etc. (beyond saving a few pennies) is that manufactures can't know what the outlet you're going to use looks like (they know what it *should* look like, but read the second sentence again). Faced with just the power box on the dishwasher and what looks like no outlet box on the wall, this is what they came up with. I like to call it "illogical logic."
Answer: A sequence of people who did not 100% know what they were doing. There is a reason why many places restrict electrical work to licensed electricians.
One likely possibility: Disposal.
A disposal is normally on some sort of switch (a normal toggle switch like this, an "air switch", something). If someone was adding a dishwasher where none existed before (quite common for a house built in the 1960s or earlier) and had a disposal but didn't really need it, then they might decide to disconnect the disposal and connect the dishwasher to that circuit, which is perfectly acceptable.
If that person did not understand how to hardwire an appliance, they might not realize that the proper thing to do is:

Remove the switch
Splice the wires together in the switch box (now just a "junction box") with wire nuts
Install a blank cover plate on the box

which you should do now.
In addition, the box should be mounted securely to a wall, floor, or permanently installed cabinet surface. That is almost always very easy with a metal box. If it is a plastic box then that may not be so easy, in which case I recommend replacing it with a metal box.
The NM cable (dishwasher to box, box to next box or through the wall or floor, etc.) should be secured to wall, floor or permanently installed cabinet surfaces such that it does not get moved when using the cabinet for storage and also that nothing should be on top of the cable - normally this means securing it to the back wall of the cabinet.
Comment: Heck, they could have replaced the switch with a GFCI outlet and put a cord on the dishwasher. At least around here that's allowed.
Comment: Yep. Want to bet they didn't have wire nuts? Because this reeks of saving a trip to the hardware store.
Comment: Or a GFCI deadfront and put the dishwasher on the load side and continued with the existing NM instead of switching to cordage.
Comment: They'd have had to run the cable through the cabinet side to install the GFCI, and bored another hole for the D/W cord.
Answer: Hardwired dishwashers need a disconnect switch.
It appears to me the installer did not understand "in an accessible area" and just stuck it in a junction box (if even) and stuffed it behind the dishwasher.
The right place is on the kitchen backsplash. To avoid bad user-interface / consumer confusion, I recommend using a GFCI switch there. Which also provides the required GFCI protection.


Difference between Ranged Sorcerers Attack and Ranged Basic Attack

Question: The attack Dragonfrost (PHB2 pg 139) is a Sorcerer at will attack that is Ranged 10. How ever it also has a special section stating "This power can be used as a ranged basic attack". What difference would this make to using this attack ability in combat? Would using it as a basic ranged attack require the use of a ranged weapon, adding the power to the basic attack?
Answer: Note: RBA = ranged basic attack
Being an RBA has no effect on how you use the power.
Dragonfrost works exactly the way it seems like it would from looking at the power description: it's a ranged implement attack that targets 1 creature within range 10.
Being an RBA does affect when you can use the power.
There are a number of ways to grant yourself and/or allies a basic attack (sometimes it will specify a melee basic attack or a ranged basic attack, but in many cases it just says basic attack, which means the person making the attack can choose which). If you have the Dragonfrost power, then whenever you could make an RBA by pulling out a weapon and using your dexterity modifier for the normal RBA, you could instead attack with the Dragonfrost power (which you should do, unless you're carrying a ranged weapon and have a dexterity that's better than your charisma, in which case why are you a sorceror?).
Comment: @RMDan Correct. Generally speaking it's only a minor boost for a power to count as an RBA. When a melee power counts as an MBA, that's a big deal, because it also means that power can be used on OAs and charges.
Comment: That's good to know. So I could use Dragonfrost if an allies ability would grant me an RBA during their attack/turn.


Chromium - open with home pages "pinned"

Question: I'm using the latest PPA Chromium under Ubuntu and I really like the "Pinned" tabs idea.  Anyone know of a way to have my home pages open as pinned tabs automatically?
Answer: There is no GUI way of doing this atm, but I solved this problem by using switches in the actual launcher for Chromium. Here is what I use:
chrome.exe page1 page2 page3 --pinned-tab-count=3
That will open up these three pages pinned. Just replace the pages with the URL of your favourite sites and change the --pinned-tab-count number accordingly.
Answer: I would guess that this is not possible yet.
Have a look at, and maybe keep an eye on in case  anything happens, on
http://code.google.com/p/chromium/issues/detail?id=24781


How do I access a hard drive from a live CD?

Question: How can I access my hard drive from a Live CD? As far as I can tell the hard drive can only be accessed via /media/longnumberhere after its been mounted. Is there a way to access the hard drive a drive instead? (so it can be accessed by /dev/hda)
Answer: Not sure what this has to do with shredding...
To mount a drive in this manner, first locate it using sudo fdisk -l in a terminal (within the LiveCD environment).
Then determine the drive/partition you want and mount it as usual with the mount command.


never ending omnibus progression

Question: When I studied music theory in college (years ago), I remember my theory instructor demonstrating a use of the omnibus progression where it would go on forever, sounding continuous to the untrained ear (which made the whole class start laughing after like a minute of increasing intensity). I think it involved making some tricky inversions at some point, but I can't find an example of anyone doing this online.  Does anyone know how to make this never-ending omnibus progression?
Comment: This reminds me of [Shepard tones](https://en.wikipedia.org/wiki/Shepard_tone).
Comment: Are you talking about [this type of progression](https://en.wikipedia.org/wiki/Omnibus_progression)?  (That's what I've usually heard referred to as the "omnibus," but since you said you couldn't find it online, perhaps you're referring to something different?)
Comment: @Dekkadeci exactly! I couldn't remember the name of that either. It's like using the omnibus progression to create a shepard-tone-like illusion.
Comment: @Athanasius Basically, yes, only he had changed something about it so it could be played indefinitely.
Answer: I've seen (but I cannot remember where) a cyclic type of omnibus. As the progress is just an extended voice exchange, one could exchange the voices back though that would give a <> style rather than a wedge. One cheat (which works for all progressions but may not be musically interesting) is to double everything at the octave (or make 3 or 4 octaves if possible) then transpose the low voices up in a staggered manner and transpose upper voices down similarly; the result will be a fake Shepard Tone.
Since the basic construction is a wedge (<) which has one-way movement, one must figure out how to make this repeat and sound natural. Either fade in new  or both.
Comment: The 1st approach would be cool and would definitely work. It would be interesting to hear an example of that. The 2nd approach is likely similar to what my professor played (given he has only two hands).
Answer: Further to the Wikipedia page already linked to by Athanasius in a comment, the omnibus progression can also be extended in such a way as to harmonise a descending chromatic scale in one part and an ascending chromatic scale in another, like this:
Answer: To respond to something that came up in comments: to be clear, the Omnibus Progression doesn't need to be "modified" to be played indefinitely.  If you look at the Wikipedia page first example, there's only an octave given in the example, but you end up with a G7 chord that is precisely the same voicing as the E7 seen as the fourth chord in the sequence.
Basically, the progression starts over again at the 10th chord, just now transposed "up a third."  Every fourth chord is a dominant seventh, and they change voicing, but the voicing repeats every tenth chord.  (Effectively, there are three different upper voices and they each take turns doing various parts of the chord during each three-chord segment of the progression.  After three iterations of that, they reset.)
Another way to think about it is if you look at the 10th chord in the Wikipedia example (on B-flat7) and now just pretend you were starting the progression over again transposed to B-flat, then you can keep going.  After 10 more chords, you start again (now in D-flat), and continue indefinitely.
The oscillating pattern mentioned in another answer is also simple to make.  The voice-leading in the omnibus is effectively reversible, as it depends on strong chromatic bass motion and contrary voice resolutions in the upper voices.  So, you can use a chromatic ascending bass instead with similar upper voices, and the whole thing goes backwards.  If you turn around after several chords (usually done at another dominant 7th), you can get an oscillation that sounds a bit carnival-like.

never ending omnibus progression


Why don't we (or when do we) use a lenient definition of nightfall on seder nights?

Question: There are various positions on when we can say maariv (evening prayers), corresponding to various positions on when the day ends (and, thus, a new day begins which starts from the night). But the times I see for starting the Passover seder all use a stringent (i.e., late) definition (3 stars, even 3 small stars).  Why don't we (or when do we) use a lenient definition of nightfall on seder nights?
Comment: "There are various positions on when we can say maariv, corresponding to various positions on when the day ends" This isn't entirely accurate. Many positions about Maariv are not based on when the day ends but when Plag or Bein HaShemashot or "Erev" start, even before the final end of the day.
Comment: Are you referring to Shuls that regularly publish different nightfall times? I've rarely seen such a thing. Probably you just see the late time because that's all they ever publish, for better or worse to keep things simple, even though you're right an earlier time is fine.
Answer: R. Yitzchak Abadi does indeed record a lenient definition. In Ohr Yitzchak Vol. II (Kuntres Acharon Hilchot Pesach) he writes:

מיד כששקעה חמה יכול להתחיל בסדר אך לא יאכל המצות קודם צאת הכוכבים
Immediately when the sun sets one can begin the seder, but one should not eat the matzot before tzeit hakochavim.

In a footnote there he explains:

כיוון דביה"ש הוא ספק לילה במצה שהיא דאורייתא צריך להמתין לצאה"כ
Since bein hashemashot is possibly night, by matzah which is biblical you have to wait until tzeit hakochavim.

The logic here seems to be that since it is uncertain whether night already begins at sunset, we apply the rule of acting stringently for biblical mitzvot and acting leniently for rabbinic mitzvot.
Comment: This doesn't really answer the question. It doesn't provide for using a lenient definition of nightfall, but rather proposes, contra the Shulchan Arukh, that nightfall isn't necessary and Bein Hashemashot is sufficient. The OP asked about using earlier times for nightfall than used for certain biblical obligations when we are strict for 3 visible small [adjacent] stars. (Not my downvote)
Comment: second point is the key
Comment: @orange it's essential to his argument certainly but it's quite unintuitive. one glaring problem with R Abadi's logic is https://judaism.stackexchange.com/a/44206/759 . the fact that it rejects centuries of precedents in implicit favor of a combination of minority opinions is just a bonus
Comment: סיפור יציאת מצרים is also a biblical obligation of the night of the 15th.
Answer: The Mishna Brura Orach Chaim Siman 472,1 say that one should wait till definite nightfall, not Shekia-sunset (doubtfull nightfall), which means only when 3 stars emerge at night.
According to Myzmanim there are various opinions when this is, some say 6.45 degrees, some 7.12 degrees according to Igros Moshe or 72 minutes for those that hold like Rabeinu Tam. Even though on Motzei Shabbos and Yom Kippur is there a minhag to use the more strict definition of Nightfall 8.5 degrees because there is a mitzva Deoraisa and punishment of Kareis (unless there is need for someone unwell), on Seder night though, the Hagadda which has to accompany the matza at Nightfall is Deoraisa, but by the time you get to Ma Nishtana after Kaddesh, urchatz, Karpas, Yachatz and pouring the second cup, the 7 or 8 minute difference between 7.12 degrees lenient time to 8.5 degrees strict time is easily covered, so one can use the lenient opinion unless one is of a Chassidus that always keep 72 minutes after sunset.


How can I make an attractive enclosure for my circuit?

Question: I have finished working on the circuit and firmware for my design of a MIDI controller. I'd now like to take it off the breadboard and put it inside some sort of enclosure. I can handle making the PCB, but I really have no idea about how to go about making an attractive enclosure?
The circuit has a 16 button grid and 2 potentiometers on it and a USB connection. I saw the design of the Midi fighter and really liked it. I looked at Radioshack and saw they had some cheap looking boxes, but that's not really what I was looking for.
Is there some sort of resource or pointers to how to do attractive enclosure design?
Comment: You came to the wrong place.  We're engineers.  We don't do attractive.
Comment: Have you looked at the [tag:enclosure] or [tag:cases] tags?
Answer: My two favorite places are OKW Enclosures and Polycase.  They have off the shelf options in different styles, no minimum order.  They will even do customization on small orders too, i.e. drill holes, silkscreen, etc.
If you can't wait and you are lucky enough to live next to a Fry's electronics, you can walk over and pick up a simple one for not much extra overhead.
Answer: Instructables has a lot of stuff about making cases.
I used once a plastic laminate called "Forex", which is used in advertisement and is very easy to craft. Unfortunately, googling it gives a lot of results for "Foreign Exchange" or something similar.
You can also try in the home improvement site here; it's about DIY stuff, I don't know anything more.


Learning about Computer Vision

Question: I am really intrigued by the field of computer vision and the potential it has. Are there any examples (preferably implemented in .NET) which I can study along with a reference book?
Answer: Sample Vision Code

Vision Source Code - Carnegie Mellon University
Open Source Computer Vision Library - Sourceforge
Computer Vision Test Images
libsift - Scale-Invariant Feature Transform implementation
C# wrapper for OpenCV

Resources

Computer Vision Online - Computer Vision Online
Computer Vision "Home" - Carnegie Mellon University
Lecture on Vision Systems - Cardiff School of Computer Science
Lectures on Computer Vision Systems - The University of Nottingham Computer Science Department
Feature Detection - Wikipedia Article
Scale-Invariant Feature Transform - Wikipedia Article

Stack Overflow Questions

Where do I learn about Image Processing and Object Recognition?
Image Processing Textbooks?
Computer Vision References
Answer: OpenCV (Open Computer Vision) is the most popular library, and it has been wrapped for C#:
http://www.codeproject.com/KB/cs/Intel_OpenCV.aspx
Some discussion about this wrapper and the library in general is here:
http://coolthingoftheday.blogspot.com/2008/08/opencv-open-source-computer-vision-for.html
Answer: While the OpenCV library is interesting to use, it doesn't offer a lot of transparency as you learn. If you're interested in actually learning about the field, I would recommend looking into low-level image processing libraries and implementing your own Computer Vision applications. Once you've coded your own basic CV applications, using the OpenCV library becomes a lot easier. I would suggest the following topics to advance quickly through the basics:

sobel operators for edge detection
trying your hand at color segmentation
reconstructing 3d information from stereo images using disparity maps

Here's a site with some good test images (http://www.cs.cmu.edu/~cil/v-images.html).
I also found a good resource of course slides that cover the majority of these topics at (http://www.cs.nott.ac.uk/~tpp/G5BVIS/lectures.html)
Happy hacking =)
Answer: Here's a large collection of code, toolkits, and apps you might find useful
http://www.cs.cmu.edu/~cil/v-source.html
Answer: You could start by looking at some of the similar questions on this site:

where-do-i-start-learning-about-image-processing-and-object-recognition
image-processing-textbook
computer-vision-reference

I can also look at these two sites:

http://www.cs.cmu.edu/afs/cs/project/cil/ftp/html/vision.html
http://www.cs.cf.ac.uk/Dave/Vision_lecture/Vision_lecture_caller.html

The sites provide information, tutorials and code examples, even though they are not actively maintained anymore.
Answer: There is the OpenCV project on sourceforge with a book that you can get as well.  You can see it here. However, that is not a .NET solution it is C
Answer: I recommend Open Computer Vision Library. It's much spoken of and looks promising. It even has an O'Reilly accompanying book :)

The Open Computer Vision Library has >
  500 algorithms, documentation and
  sample code for real time computer
  vision. Tutorial documentation is in
  O'Reilly Book
Answer: I've done a bit of work with SIFT in the recent past and it seems to be a rather interesting modern algorithm for feature detection, which is one of the major (and perhaps more advanced) topics within machine vision. Someone has written a C# library for SIFT with a pretty nice example that can automatically stitch together separate photographs of the same scene. Admittedly, this isn't a very complete answer, and I can't recommend a reference book, but hopefully it should be of some use to you anyway...
Answer: The AForge.NET library is pretty good and is written in C#, with the source available here.
Supported features are:

AForge.Imaging - library with image processing routines and filters;
AForge.Vision - computer vision library;
AForge.Neuro - neural networks computation library;
AForge.Genetic - evolution programming library;
AForge.Fuzzy - fuzzy computations library;
AForge.MachineLearning - machine learning library;
AForge.Robotics - library providing support of some robotics kits;
AForge.Video - set of libraries for video processing etc.

The algorithms are maybe not as cutting edge/academic as some of the other answers but a lot of the engineering problems taken care of (getting video into your application, etc).

Learning about Computer Vision


Is information kept by Stack Exchange after profile edit?

Question: If you edit your profile on a Stack Exchange site, does Stack Exchange keep records of your old profile data?
Answer: Moderators can see your previous display names if they need to. This is the most widely seen thing that you can change in your profile as it's displayed against all your questions and answers. Most other editable fields are only displayed on the profile page itself.
There's a feature-request to store a complete history of profile changes
Answer: Public information from your profile will also be temporarily accessible via the Stack Exchange Data Explorer. It's in the Users table and your ID appears in the URL of your profile.
https://meta.stackexchange.com/users/547450/user
                                       ^
                                       id

If your question relates to accidentally having deleted some data from your profile that you want back, this could be helpful, since it's only updated once a week (every Sunday morning around 3:00 UTC, to be exact).


Torque limiting application

Question: I have an application in which speed of the shaft is 0.54 rpm. The input speed of the motor (induction 4 pole AC motor) is 1400 rpm. So the gear reduction is enormous. I had two helical redactors coupled together and I read that in this situation  when you have such big reduction (2 stage reduction) and super low speed you have to limit the input torque. I don't understand this – why is this necessary? The start up torque of AC motor is 2-4 times higher than the nominal torque, how to start this application? Can someone tell me why in big reduction systems it is necessary to limit input torque?
Answer: Because the torque is multiplied by the same factor that you reduce the speed with. For large reductions this can create a lot of torque. If the output is seized up then this results in large forces which will start damaging things like bending or shearing shafts, stripping gears or cracking the case.
A common way to limit torque is to include a sacrificial plastic gear that gets stripped when torque becomes too large. This is then the designated weak point just like the fuse in an electrical system.
Comment: Oks, but how is suppose to limit the torque. The gear is driven my AC motor i think the only one way to is ti limit AC motor current, but it''s interesting how the motor is going to start - the start torque is about 4 time nominal
Comment: @next_for it means that if torque gets too high the plastic gear will simply fail. If the output shaft is not blocked then the torque just won't get that high.

Torque limiting application


How I create table View of webform submissions

Question: I want to view webform submissions in table view. I created a view of webform submissions but it shows a link for the data submitted. I dont want to use link, I want only simple table view.
Comment: You may be looking for this feature: http://drupal.org/node/680386
Answer: You can create your own tables of Webform submissions with Views...

Make a new view of type 'Webform submissions'
Add a page, set the path and set the Style to 'Table'.
Add the fields you want, sort and filter as needed.

If you want submissions filtered by the node (Webform) they were submitted against,  you should add a relationship for 'Webform submissions: Node' so you can pass the Node ID to the view -- remember to include the argument placeholder in your path for the nid (e.g. submissions/%)
(Of course, this provides a tabular view of Webform submissions with the fields you choose as outlined in your question -- the existing view of submissions will still be on the tab for that Webform node... Changing that is a different question.)
Comment: sorry for very very late reply. I made some changes with help of your answer.
Answer: In default webform results are arranged in Table format.If you wish to show webform results to users then just enable permissions in people>permission.


Hatchbox Silver PLA settings?

Question: I have a RepRap Prusa i2. I have done the majority of my printing with clear PLA that I got on the cheap from eBay. It works just fine.
I bought a roll of Hatchbox Silver PLA (1.75 mm) from Amazon. I have never had a print go well with it. I have tried various combinations of hotter and cooler extruder and bed (180 - 220°C extruder, 50 - 78°C bed). Prints always either curl up from the bed after 5-20 layers are deposited or delaminate in the middle of the print. I print directly on the heated glass bed, and have also tried various cooling fan settings.
Does anyone have good settings (Slic3r) to use with this stuff? Or any other advice for getting a successful print?
Answer: I've been using Hatchbox 1.75 mm (but white), and settled on 190°C extruder temp, and 60°C bed. I've had trouble getting some prints to adhere to the bed, but most have been ok; I don't see a clear pattern. I don't know whether it's the fiber or my settings. I'm trying slightly higher temperatures, higher extrusion rates, and other filament brands to see if those help. Will post back if anything clear shows up...
Answer: I know the original user has probably found an answer to their question by now, but I'll add my 2 cents for the benefit of others who come across this.
My experience with Hatchbox has been that the walls and top layers were looking good at 200°C, but when I started stress testing the parts to their fail points I noticed that the internals were just a fibrous mess with no structural integrity.
So I started increasing the temperature in increments of 10°C and found that at 210°C it improved, and at 220°C there was good layer adhesion.  At 230°C layer adhesion was absolutely beautiful, but it begins to get a little too melty.  I have settled at 220°C for my machine.
Keep in mind that everyone's printers are going to be slightly different - hotends, fan setup, even the thermistor could have varied resistance from one machine to another causing incorrect readouts on temps.  That's why you have to tinker and find what works well for you and your machine.
Answer: I use a Wahao Duplicator I3 with a heated bed. I have only used the orange Hatchbox PLA with great results. I use 210°C for the extruder and 55°C for the bed. Speed is 40 mm/s which works well for me.
Answer: I use 205°C for the extruder and 60°C for the bed on my RoBo3D. I also put hot glue stick on the bed to help adhesion and use a brim if it is a small object.
I would also check the first layer to see if you need to adjust your z offset. Delamination could be a sign the plastic isn't fusing correctly, which could be both an offset or temperature issue. It could also be a feed issue from the roll itself.
You can try printing these, Print Temperature Calibration Piece, and see what temperature gives you the best result.
I have had only one delamination happen to me and I think it had more to do with a hiccup in the commands sent to the printer than the filament itself. I basically have only used Hatchbox filament.

Hatchbox Silver PLA settings?


Is single/multi TT important by USB3 hubs?

Question: I'd like to buy a new USB3 hub to replace my old one, which has only 4 slots. By USB2 hubs single TT was a problem, because USB1 devices could slow down the entire hub. Is there something similar by USB3 hubs? Can too many USB2 devices slow down USB3 data transfer by these hubs or was this issue addressed by designing the new standard?
Comment: +1. It is a deeply complicated system topic. Whoever voted to close it down is incorrect.
Comment: The wikipedia article is quite wrong in its description of TT workings. Hubs/TTs don't really "automatically translate", the host must use a special category of transactions called "split transactions" to manage the TT and devices behind it..
Comment: I'm not familiar with the term TT. Please clarify.
Comment: @TwistyImpersonator https://en.wikipedia.org/wiki/USB_hub#Transaction_translator
Answer: In USB 2.0 framework USB1 devices didn't slow down anything. The problem with single TT (Transaction Translator, to translate HS traffic into FS/LS packets locally, in each hub) was that a single TT would slow down USB1 devices on the same hub, not the overall HS hub performance.
In USB 3.x specifications, electrically the USB 2.0 interface is completely independent from SuperSpeed path, it runs in parallel, on dedicated old-style D+/D- wires. Unlike USB 2.0, USB 3.x doesn't introduce "TT" (Transaction Translator), the USB 3.x super-speed transactions cannot be "translated" into HS USB 2.0 transactions.
However, internal pipes of the controller and system interfaces (internal fabric) have limited bandwidth, so the system must manage it. The xHCI specifications define the concept of "BI", "bus instance". BIs can be of SS type, or HS type, or LS/FS type. System can assign several BIs to a port, and allocate certain bandwidth for each port, so it is possible that too many USB2 devices may encroach into SS bandwidth. This will depend on xHCI implementation and on software driver stack. It is unclear to what extent modern USB stack is intelligent to manage all this flexibility. This write-up is an example of general confusion in the area of USB bandwidth allocation.
Comment: @inf3rno, do you mean "10-port hub"? In USB terms these are called "ports", not "slots". Also, keep in mind that a 10-port hub will likely have at least one extra tier of hub controller chips, due to pin limitation per IC package, see https://superuser.com/a/1122852/620011 Also, any hub is a generic device, give or take, but port bandwidth allocation is a function of  host controller and host software.
Comment: So it is unclear, but probably you'd need many USB2 devices to have effect on USB3 speeds. I'd like to buy a 10 slot hub. They are expensive, so hopefully they are prepared for this scenario as well.
Comment: Yes, I meant 10 port. :-)
Answer: Single TT vs Multi TT is still relevant for USB 1/2 Low- or Full-speed devices connected to the hub in some situations, but it is not relevant to USB 3 superspeed communication.
Note: this answer will deal mainly with the scenarios of using USB 1/2 devices on USB 3 hubs, I don't go far into USB 3 stuff like the other answer, though you are likely to find less problems with USB 3 devices in general.
A 3.x hub has to include USB 2 hubs in it as well, as the USB 2 communication still goes back via the old USB 2 D+ and D- wires to the host, so all USB 1.1 and 2 communication still shares that same 480Mbit Fullspeed USB 2 bottleneck as USB 2 always has.  This may be disappointing to some but I guess it was a compatibility or cost win?  USB 3 devices aren't really impacted by what the USB 2 bus is doing on the hub this to any degree you'd need to worry about (if they are genuinely using USB 3) because that will go via the USB 3 hubs back to the host via the superspeed wires.  And with a 5Gbit pool there, as opposed to the 12Mbit pool that was the concern for single TT on USB 2, there's more to share.
There is a separate issue that is rarely talked about - regardless of how advanced your USB 3 hub is, an isochronous USB 1/2 device can reserve bandwidth and this can cause conflicts way earlier than you may imagine for something so modern as a USB 3 hub - even if the hub's USB 2 side has Multi TT.  This is why things like webcams, capture cards and audio interfaces continue not to work well through hubs if they are USB 1/2 devices, because they "reserve" bandwidth on that old conceptual 12Mbit shared bus that your modern hub remains compatible with.  In some cases I've seen that the software drivers for certain audio devices cripple some of the device's functionality when the are on a hub, possibly out of fear of such contention for bandwidth reservation.
One more tip - blue plug doesn't always mean a device really uses USB 3.


Traceroute of Router's own serial port

Question: I got two routers on my network and I am pinging one router's serial port ip address from that router itself. by checking traceroute I found ping is going outside to neighbor router which is directly connected via serial link on the same port I am pinging.what is the reason of that traceroute behaviour? Image of Router R1, traceroute from R1 to R2, R1 have ip address of 10.1.1.1/24 and R2 have 10.1.1.2/24.
Comment: You need to provide more information. A diagram would be good, and we need the router configurations and traceroute. Edit your question to include these.
Comment: Please, never put text in an image in your question or answer. Copy the text, paste it into your answer, and use the Preformatted Text feature (`{}`) on the text. We need the full router configurations, too.
Comment: Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
Answer: Because of when you traceroute you own IP address on a point-to-point serial interface the ICMP packet goes over the wire to the other side and back.

Traceroute of Router's own serial port


Runtime interfaces and object composition in C++

Question: I am searching for a simple, light-weight solution for interface-based runtime object composition in C++. I want to be able to specify interfaces (methods declarations), and objects (creatable through factory pattern) implementing these. At runtime I want mechanisms to instantiate these objects and interconnect these based on interface-connectors. The method calls at runtime should remain fairly cheap, i.e. only several more instructions per call, comparable to functor patterns.
The whole thing needs to be platform independent (at least MS Windows and Linux). And the solution needs to be licensed liberally, like open source LGPL or (even better) BSD or something, especially allowing use commercial products.
What I do not want are heavy things like networking, inter-process-communication, extra compiler steps (one-time code generation is ok though), or dependencies to some heavy libraries (like Qt).
The concrete scenario is: I have such a mechanism in a larger software, but the mechanism is not very well implemented. Interfaces are realized by base classes exported by Dlls. These Dlls also export factory functions to instantiate the implementing objects, based on hand-written class ids.
Before I now start to redesign and implement something better myself, I want to know if there is something out there which would be even better.
Edit: The solution also needs to support multi-threading environments. Additionally, as everything will happen inside the same process, I do not need data serialization mechanisms of any kind.
Edit: I know how such mechanisms work, and I know that several teaching books contain corresponding examples. I do not want to write it myself. The aim of my question is: Is there some sort of "industry standard" lib for this? It is a small problem (within a single process) and I am really only searching for a small solution.
Edit: I got the suggestion to add a pseudo-code example of what I really want to do. So here it is:
Somewhere I want to define interfaces. I do not care if it's C-Headers or some language and code generation.
class interface1 {
public:
    virtual void do_stuff(void) = 0;
};

class interface2 {
public:
    virtual void do_more_stuff(void) = 0;
};

Then I want to provide (multiple) implementations. These may even be placed in Dll-based plugins. Especially, these two classes my be implemented in two different Dlls not knowing each other at compile time.
class A : public interface1 {
public:
    virtual void do_stuff(void) {
        // I even need to call further interfaces here
        // This call should, however, not require anything heavy, like data serialization or something.
        this->con->do_more_stuff();
    }
    // Interface connectors of some kind. Here I use something like a template
    some_connector<interface2> con;
};

class B : public interface2 {
public:
    virtual void do_more_stuff() {
        // finally doing some stuff
    }
};

Finally, I may application main code I want to be able to compose my application logic at runtime (e.g. based on user input):
void main(void) {
    // first I create my objects through a factory
    some_object a = some_factory::create(some_guid);
    some_object b = some_factory::create(some_guid);

    // Then I want to connect the interface-connector 'con' of object 'a' to the instance of object 'b'
    some_thing::connect(a, some_guid, b);

    // finally I want to call an interface-method.
    interface1 *ia = a.some_cast<interface1>();
    ia->do_stuff();
}

I am perfectly able to write such a solution myself (including all pitfalls). What I am searching for is a solution (e.g. a library) which is used and maintained by a wide user base.
Answer: While not widely used, I wrote a library several years ago that does this.
You can see it on GitHub zen-core library, and it's also available on Google Code
The GitHub version only contains the core libraries, which is really all the you need.  The Google Code version contains a LOT of extra libraries, primarily for game development, but it does provide a lot of good examples on how to use it.
The implementation was inspired by Eclipse's plugin system, using a plugin.xml file that indicates a list of available plugins, and a config.xml file that indicates which plugins you would like to load.  I'd also like to change it so that it doesn't depend on libxml2 and allow you to be able to specify plugins using other methods.
The documentation has been destroyed thanks to some hackers, but if you think this would be useful then I can write enough documentation to get you started.
Comment: Thanks Tony. I will definitivly take a look.
Answer: A co-worker gave me two further tips:

The loki library (originating from the modern c++ book):
http://loki-lib.sourceforge.net/
A boost-like library:
http://kifri.fri.uniza.sk/~chochlik/mirror-lib/html/

I still have not looked at all the ideas I got.


To whom was Yoda referring when he said, "There is another?"

Question: In the original trilogy Yoda refers to another hope:

Obi-Wan: "That boy is our last hope."
Yoda: "No...there is another..."

The assumption being after seeing Return of the Jedi (Episode VI) that the other was Leia.
If, however, you consider the prequel trilogy canon, then this assumption depends greatly on your point of view*. Obi Wan knows about Leia (and for unknown reasons has discounted her as a hope), so Yoda must be referring to someone or something else.
Is there any canonical source as to what Yoda meant, or was uncle George setting us up for Episode VII?
*as a wise man once said

you will find that many of the truths we cling to depend greatly on
  our own point of view.

Just to add a bit of clarity: I was thinking about who Yoda was referring to when he was talking to Obi-Wan. When talking to Luke, it is obvious that Leia is the other (as he talks about a 'Skywalker'). It is not so obvious (after watching the prequel trilogy) that he means it when talking to Obi-Wan.
Comment: @MarkRogers Related, but not duplicate.
Comment: "Obi Wan knows about Leia... so Yoda must be referring to someone or something else" — not necessarily. Obi-Wan might have decided that Leia doesn't count as "a hope", but Yoda might not agree with him. If we saw the rest of the conversation, it could have gone "OBI-WAN: You don't mean Leia, surely. YODA: Indeed mean Leia I do. OBI-WAN: Come on Yode, she's as useless as your weird sentence construction."
Comment: Maybe Ben felt that an untrained Leia taking down the Emperor and restoring the Jedi order was not worth hoping for if the barely trained Luke should fail?
Comment: @jeremy-french, re: your edit - it's obvious that Leia is the other skywalker when Yoda is talking to Obi-Wan, but it's not obvious when Yoda is talking to Obi-Wan. Huh?
Comment: (Note to the producers of *The Force Awakens*: yes, I am available for script work.)
Comment: possible duplicate of [Did Yoda Intend On Training Leia As a Jedi?](http://scifi.stackexchange.com/questions/12403/did-yoda-intend-on-training-leia-as-a-jedi)
Comment: It was Leia - Obi-wan was just a sexist pig.
Comment: I always assumed it was a variance of (WARNING TVTROPES LINK!!!) http://tvtropes.org/pmwiki/pmwiki.php/Main/AsYouKnow
Yoda knows of Leia, so does Obi-Wan, Luke has already flown off - so there is probably no one else on Dagobah - but US, the audience. Because, let's be honest, Ben is a manifestation through the Force, Yoda need not have actually spoken aloud.
Comment: Don't remember where, but I've heard of the possibility that Leia isn't actually Luke's sister.
Comment: additional related discussion: [Did Yoda definitely know who the other hope was?](http://scifi.stackexchange.com/q/91685/5184)
Comment: Are we absolutely sure there wasn't a third sibling to Luke and Leia, little mentioned in canon? Donald Skywalker, anyone?
Comment: It doesn't really make sense in ESB for Yoda to mean Leia, since he literally says seconds before this to Luke, to sacrifice her if he honors what she fights for.
Answer: This dialogue from Star Wars episode VI Return of the Jedi made it clear it's Leia :

BEN: Then the Emperor has already won. You were our only hope.
LUKE: Yoda spoke of another.
BEN: The other he spoke of is your twin sister.
LUKE: But I have no sister.
BEN: Hmm. To protect you both from the Emperor, you were hidden from your father when you were born. The Emperor knew, as I did, if Anakin were to have any offspring, they would
  be a threat to him. That is the reason why your sister remains safely anonymous.
LUKE: Leia! Leia's my sister.
Comment: Because he didn't had time to initiate her to the ways of the force. And with Yoda gone, who will?
Comment: @Bardo She did shows force affinity during the original trilogy. Without any training, she used telepathy to communicate with Luke while he hung on the antenna behind Cloud City. While Luke initiated the communication, it's not something that she would be able to do if she didn't had the force with her.
Comment: @Bardo That seem convoluted. After all, The last words of Yoda were *"Luke, the Force runs strong in your family.
Pass on what you have learned, Luke... There is...
another...Sky...Sky...walker."* He would not had used his last words to hint about a potential children from Leia, *"Always in motion is the future"*.
Comment: Also keep in mind, how does this work with Yoda's line to Luke in ESB where Luke asks "And sacrifice Han and Leia?" and he says "If you honor what they fight for...yes!" This is like literally seconds before he says to Obi-Wan "there is another".
Comment: Good point. Then why does Ben not know of her, or assume that she has is not a hope?
Comment: Some people states that the truly hope isn't exactly Leia (who doesn't shows any force affinity during the original trilogy), but it's future children. Probably Yoda's power can trascende time and space and see the future of Leia's children, while Ben simply see that Leia hasn't the Force.
Comment: That's not clear. Probably she's more attuned to it's brother than anyone more on the MF. Luke is about to die, recently shocked by it's father discovery and, although gaining in Force potential, far away to control all it's power. It's acceptable to think that's Luke's mind who stablish contact with his nearest affine mind in seek of help.
Comment: I'm going to split hairs here. But Yoda spoke to Luke of another sky-walk-er, which is Lea. As I said in the post, after watching the prequel trilogy it is not conceivable that Ben needs to be reminded of Lea. Hope != Skywalker
Comment: Great answer, but it begs the question, how is it that ghost Ben does not know about Leia in ESB?
Comment: @JDoe He does know, see my comment up there. "he didn't had time to initiate her to the ways of the force. And with Yoda gone, who will?"
Answer: As a further confirmation to DavRob, Episode 3 (at least Matthew Stover's novelization that was approved and edited by Lucas, not sure about the script of the movie) confirms that Yoda ALWAYS meant Leia by "another" hope:

"... Hidden, safe, the children must be kept. Foundation of the
  new Jedi Order, **they will be**."
  "We should split them up," Obi-Wan said. "Even if the Sith find
  one, the other may survive. I can take the boy, Master Yoda, and you
  take the girl. We can hide them away, keep them safe— train them
  as Anakin should have been trained —"
  ... When right is the time for skills to be taught, to us the living Force will
  bring them. Until then, wait we will, and watch, and learn."
Comment: @SamIam - Old, Yoda was. Senile.
Comment: @DVK: Old, Lucas was. Senile.
Comment: @dmm When six Star Wars films you have made, look as good, you will not.
Comment: That brings another question to mind:  If Yoda and Obi-Wan originally conspired to train them in the force, than why did Obi-Wan have to argue with Yoda about training Luke in Empire Strikes Back?
Comment: @DVK Debatable, that statement is. http://scifi.stackexchange.com/q/6343/2841
Comment: And what was one of features we know of how Anakin was supposed to be trained?  When he was very young, before he could develop emotional attachments to his family.  So what did Yoda and Ben proceed to do?  Leave them alone until they're adults and have had ample time to develop emotional attachments to friends and family, and leaving them only a matter of months to learn skill sets their opponents have spent decades mastering.  Those Jedi sure are smart.
Comment: @SamIamsaysReinstateMonica - I always saw that scene not so much Obi-Wan trying to convince Yoda, but more like Yoda giving Luke a hard time and Obi-Wan showing up to say "Yoda, don't be an ass. Just train the boy already."
Answer: If we are to assume that Yoda's statement that 'there is another hope' has any thematic relevance to the movie in which is takes place, Yoda must be referring to Vader, since Leia does not save the Galaxy. The entire Star Wars saga is about Anakin's redemption, and how his redemption is the only way in which the darkside can be defeated. Thematically, it makes no sense for Yoda to be referring to Leia, other than to state that the Jedi have no idea what they are talking about, which they certainly do not if they are referring to Leia.
Comment: Anakin was the greatest Jedi, and the only one capable of defeating the emperor.  Luke's refusal to give in to hatred and fear recalls Anakin to himself and leads to his redemption.  So Luke is the harbinger, and Anakin is the hope.
Comment: "since Leia does not save the Galaxy". She never needs to, because Luke does it first. The first hope comes through.
Answer: The original pre-SE/pre-Prequel novelization of Return of the Jedi explains very clearly that Leia was meant to be trained as another Jedi.
Ben and Luke are discussing whether or not Leia might be able to help sway Vader.

"She hasn't been trained in the ways of the Jedi the way you have, Luke - but the Force is strong with her, as it is with all of your family. That is why your path crossed mine - because the Force in her must be nourished by a Jedi. You're the last Jedi now, Luke... but she returned to us - to me - to learn, and grow. Because it was her destiny to learn and grow; and mine to teach."
Answer: As it says in the novel of ROTJ... Luke said "But you can't let the Emperor of Vader get their hands on her (Leia). Obi-wan said "She hasn't been trained in the ways of the force as you have Luke. You are strong and patient now, and you're ready for your final confrontation"
Luke was the only hope because if he failed, there was now NO one left to train Leia in the ways of the force. Yes, she would have the same potential, but it would be wasted because now that both Obi-Wan and Yoda were physically gone, there was no way that Leia could be trained as a Jedi.
Answer: I'm going to go against mainstream opinion . It is definitely NOT Leia . It could only be redeemed Anakin Skywalker. There are several reasons for this:

Like it or not, Leia is only supporting character in whole saga . Ok, she had Death Star plans in Episode 4, but after that her significance is much reduced. Yes, she is Force sensitive, but as far as we know, never near potential of her brother or father . And who would have trained her, even if she somehow escape from Endor ? Force ghosts ? From all that we know Jedi training requires grueling regime for months and years. Luke trained long and heard on Degobah, but despite all of that was no match for Palpatine . And as far we know, Force ghosts could appear only for short time (few minutes, or even seconds) . Otherwise, Yoda and Kenobi could train not one, but many Padawans across whole Galaxy, because there are still many Force sensitive children/younglings .
Significance of sentence There is another Skywalker is much increased in Clone Wars last episode "Sacrifice" . If you consider another Skywalker to be Leia, significance of this phrase would be practically non-existent. Both Luke and Obi-Wan Kenobi knew that Leia exists and that she has some Force talents . In the end, she doesn't do anything extraordinary, so why would  Force Priestess utter this phrase to bewildered Yoda as her (and years latter his) final words ? There must be something else .
Both Yoda and Kenobi considered Anakin Skywalker to be as good as dead . "More machine then a man", "Darth Vader betrayed and murdered your father" and especially Once you start down the dark path, forever will it dominate your destiny, consume you it will.
Yoda thought and taught Luke that there is no coming back from Darth Side. This is old and dogmatic view of Jedi Order before Order 66. Force Priestess in last episodes of Clone Wars tried to teach him something else. Yoda understood that there is some Dark Side in everybody, even him. But yet he still thought he has nothing to learn from Sith (encounter with vision of Darth Bane and illusion of Sifo-Dyas) . In other words, he could not sense good in them - right until his dying moments.
Only then he realized that simple truth - Anakin Skywalker is still alive. Suppressed, wounded, half-mad but still father of the boy standing before him. And yes, redemption is possible - there is another Skywalker, one destined to destroy Sith and bring balance to the Force. Which he did .
Comment: The Director's commentary is pretty clear that Luke (at this point) is potentially expendable **because another could be trained in his place**. That doesn't gel with it being Vader *at all*.
Comment: @Valorum Luke trained 1-6 months (various estimates)  in Empire Strikes Back , but he was not ready to face Vader then. In  RotJ his power is much grater, suggesting that he trained a lot between two episodes . Did he return to Degobah is unclear . Anyway, he did have "Jedi boot camp" behind him, something Leia could never achieve because she didn't have a tutor.
Comment: Luke only trained for a few days (months at most) on Dagobah.
Answer: There is a speculation that "another" could be not a Skywalker at all, but Ahsoka. She was already trained in the ways of the Force and mastered lightsaber combat. Finally, she has already duelled Vader and survived it (end of Rebels Season 2).
That makes her a more powerful (than Leia) candidate to defeat Vader, as Leia is untrained, and there is no one left alive capable of training her.
upd: she IS alive by the end of RotJ, according to the Rebels finale.
However:

(out-of-universe) Ahsoka character was not even conceived at the time the Original Trilogy was created, making it a retcon
The Skywalker twins were purposefully hidden by Yoda and Obi-wan, as the last hope to restore the balance to The Force. In Revenge of The Sith, they speak of no one else.

Thus, it is only a fan theory.
Comment: "Nothing is certain if she is still alive at the time of RoTJ", she is seen in the finalie to Rebels which is set after the battle of Endor
Comment: @JeremyFrench, thanks! I have updated the answer
Answer: When the line "that boy is our last hope" is said, Yoda gets bathed in a greenish blue light, representing Luke. However, when Yoda says, "no, there is another," he gets bathed in a red light, representing Darth Vader.
 You must remember that every element in a movie is an intentional choice, and that this isn't the only time that these colors are used to represent their affiliated characters, and let you know who is being discussed. The point here being that Darth Vader is the other. This makes sense since Darth Vader is actually the Hero of the story, in other words, it's about his journey and his path towards redemption. The story is merely being told through Luke's eyes.
This is why it is Darth Vader who finds his place among the Jedi Master by the end of the story. Furthermore, the thing people use to justify Leia as being the other hope is just Obi-Wan's quote, but as you'll recall, he didn't know who Yoda was referring to any more than the viewer did, and this is his own misconception, one which is used as a misdirect for the viewers. Luke is not present for all key elements of the story, which involve the struggle in the balance of the force, only Darth Vader is, because it's his story.
There is also Yoda's last words, which echo his line in Empire, and which he says after Luke has learned that Vader is actually Anakin Skywalker:
YODA ... There is...another...Sky...Sky...walker.
The fact he says this after Vader acknowledges he is a Skywalker and not before, should also let you know he wasn't talking about Leia.
OBI-WAN: I will take the child and watch over him. Master Yoda, do you think Anakin's twins will be able to defeat Darth Sidious?
YODA: Strong the Force runs, in the Skywalker line. Hope, we can . . . Done, it is. Until the time is right, disappear we will.
This line doesn't mention Leia as an additional hope, it mentions BOTH TWINS as the original hope. Further proof that it is Darth Vader who is the other hope.
Furthermore, Obi-wan spoke with certainty all the time in the prequels, and was constantly wrong.
Look at the prophecy of the chosen one: "Another depiction of the prophecy was a cave painting in the Ophuchi Sanctuary. According to the Ophuchi interpretation, the painting showed an enslaved dove rising up and defeating a serpent that slowly tried to corrupt and destroy him to catch him as its prey. When the serpent was destroyed, rain that had not fallen in the desert for many years would fall again. The Ophuchi believed that a drought would overtake Tatooine the day that the Chosen One was born, and that he would be aided in his task by one called the Argus who would free the Chosen One from his shackles before vanquishing the serpent."
The enslaved dove, is Darth Vader. The serpent trying to corrupt him is Emperor Palpatine. The Argus is Luke, who causes Darth Vader to rebel against Emperor Palpatine. So you are telling me, YOU honestly think, the PERSON DESTINED TO RETURN THE BALANCE TO THE FORCE, who GEORGE LUCAS CONFIRMED WAS "officially the Chosen One and not Luke," wasn't the other hope, but Leia was?
Comment: Can you offer any evidence to back up what appears to be a fairly outlandish fan theory?


Helper class for sql server database

Question: When is it appropriate to create a helper class for a sql server database using the asp.net framework? Basically I'm trying to create a minature wiki (with multiple pages) and storing all of the data/strings for a specific page into a table on it's own.
Comment: Whenever one would be useful. :-P Seriously, you're going to need to elaborate on this to make it a valid SO question. What problem are you trying to solve?
Comment: @StriplingWarrior see above edits
Answer: Always and Never.
Always, because you want good separation of your data tier from your business logic and presentation tiers (or model and view, or whatever framework you use).  Make sure you're thinking of it in these terms, too.
Never, because this is already done for you, on several levels.  There are numerous ORMs out there, including Linq-to-sql, NHibernate, Entity Framework, and more.  More than that, what is ADO.Net but a set of classes to encapsulate your server?
Answer: Well it could be appropriate to return a single instance of a DbConnection object - that way you only specify how to connect to the DB in one spot.
You may find it useful to have a base class for your ADO layer which provides these generic methods to deal with the ADO (part of the .NET framework for connecting to SQL server).
You could have a helper method to populate an object from a DataReader using reflection too.
Also for putting parameters together to send to a SQL command or Stored procedure.
Hope you find this helpful. :)
Answer: It's heavily dependant on your project.
For code clarity, and your own sanity, you might find it easier to make a wrapper class for all of your Database manipulation. This way you can have the rest of your code work with native objects, rather than the contents of a DataReader.
Just my advice, but hopefully helpful.

Helper class for sql server database