When self publishing, are you able to be artistic with the look of the printed word?

Question: I have not yet published a book, but from reading many books over the years I have noticed that some authors will change the font, make things bold, or change the size of the words for increased emphasis or some other reason. I have also noticed that when reading electronic copies of the same works, that those artistic details are lost. .Is there a way to self publish and still be able to be artistic with the font and sizing of the words with the finished book?
Comment: Even in situations where you CAN control font, etc I strongly caution you against excessive playing with these parameters - in many cases you'll do little beyond making the work harder to read.
Answer: The simple answer is no. Electronic reading devices contain a limited number of resident fonts and have facilities for resizing which forces re-pagination. You will notice on Kindle that page numbers are estimated. Your work will be displayed on anything from a 40" LCD screen to a 4" Smartphone.
Formatting may be maintained and controlled by saving your work as a PDF with embedded fonts. However, this results in awkward output. If your book is represented by 1 page per screen on a small device the text may be so small as to render it unreadable. If you magnify the text is will not re-paginate. Subsequently you would need to scroll left and right to read each individual line.


How do I install my printer to ubuntu?

Question: Hello Ubuntu community I have been having trouble with school because I haven't been able to print documents from Ubuntu(mostly because I don't know how to :( sad face) I was wondering if any of you nice people could help me so I can turn in my work and not get bad grades.
The printer I have:
HP Officejet Pro 8600
Thank you so much if you helped
Answer: A quick Google search and I found this: http://hplipopensource.com/hplip-web/models/officejet/officejet_pro_8600.html
Looks like the latest drivers are for Ubuntu 15.10, as of 1/12/2016.
Click on the "Download HPLIP" button near the top of the page, and follow the instructions.
Answer: I have used this very same printer with Ubuntu, but only for Wi-Fi printing.  I do not remember downloading any additional drivers (I think they came with Ubuntu 15.10).
Try going to System Settings -> Printers.
Answer: You need hplip, which can be downloaded and installed easily. It provides support for printing, faxing, and scanning (including duplex scanning and printing) for HP all-in-one printers. I have an 8620 myself.
Install HPLIP in Ubuntu/Linux Mint:

download HPLIP .run installer from:  Download HPLIP
Open terminal (Ctrl+Alt+T) and run command to give executable permission to the installer:
cd ~/Downloads/ && chmod +x hplip-*.run
Finally start the installer and follow the terminal prompts:
cd ~/Downloads/ && ./hplip-*.run

Courtesy of Ubuntu Handbook.

How do I install my printer to ubuntu?


Is CUA Mode good over usual Emacs Cut and yank commands

Question: Just wanted to capture the advantages of CUA mode over the usual emacs copy and paste commands. One advantage which is quite obvious is it similar to the keybindings which are present in other editors. What would a more better explanation on using CUA mode in emacs.
Comment: If you're comfortable with the standard bindings, stick with them. `cua-selection-mode` may still be of interest, though.
Comment: This question, as currently posed, is not well-suited to this site because it will elicit answers that are primarily opinion-based.  Could you please edit the question to conform to site guidelines more closely?
Answer: I suppose that I can give a silly answer to a silly question.

"Is French language good over German?"

Well, French it's a bit better if you're French, but then German is
better for Germans.
Neither are my mother tongue, but I like both, French maybe more.
Same thing for CUA: it's familiar to you if you're a die-hard Windows
user, and therefore maybe better. But Emacs bindings are more familiar
if you're using bash.
Personally, I'd never give up scroll-up-command on C-v.
Comment: s/bash/readline
Comment: you are correct, but my question was not to challenge the capabilities presented with any bindings, but in what ways it is good compared to the usual emacs modes. Few of them are: In CUA mode 'C-x', 'C-c', 'C-v', and 'C-z' invoke commands that cut (kill), copy, paste(yank), and undo respectively. The 'C-x' and 'C-c' work only on the active regions. Otherwise they still act as the prefix keys and the standard emacs commands like 'C-x C-c' still works. It has better support for rectangular-region, and moreover if you want to use C-v from scroll up, you can still use adding Shift to it as S-C-v.
Answer: The answers to this question will be highly subjective. The following is obviously my own opinion, and different opinions are certainly possible.
The reason the CUA commands are desirable is because of familiarity, not because there is some inherent superiority of C-x over C-w (etc.). Muscle memory is important for editor interaction, and if you are very used to the standard keys, cua-mode might make life easier for you.
On the other hand, cua-mode, even in its limited form with the keys only working with an active region, interferes with a number of Emacs commands. For example, rectangle commands (C-x r) will not be available anymore without deactivating the region first, same as narrow-to-region (C-x n n), and a few other commands, in addition to whatever commands your current mode includes under the C-c prefix that act special for an active region (e.g. Elpy will send the current region to a subprocess on C-c C-c if one is active).
So this is a question of very personal advantages and disadvantages. The main reason for using cua-mode is familiarity with the standard bindings. This is useful for people who are new to or rarely use Emacs, but I do not think that learning the slightly different bindings is particularly problematic. On the other hand, if you intend to use Emacs a lot, cua-mode will more often than not stand in your way.
(In general, I would love if Emacs would use the standard bindings. But I do not hold any delusions about the feasibility of that happening. Emacs predates those bindings, and the assumptions about key bindings are deeply ingrained in Emacs and the extensions. For example, almost every mode assumes that mode maps are on C-c.)


Windows failover cluster with two quorum disk witnesses?

Question: To avoid a single point of failure on the backend SAN system, can I place one quorum witness disk on each site and have the cluster use both?
Comment: How can a Quorum help to avoid a single point of failure? Does that even make sense?
Answer: No you can't.  The whole point of witnesses is to avoid a split brain situation.
Answer: The solution ended up being a file server witness placed at a third secure location with direct links to each datacenter to maximize redundancy.
Answer: If we just have 2  x nodes in a failover cluster then if they can't communicate both will assume the role of the cluster - the Split Brain Morten mentions.  the quorum disk fixes this as the node that can see the quorum disk wins as it gets 2 votes compared with the other node that just gets one.  If your quorum disk fails you'll still have your two node cluster so don't worry about that unless a node fails at the same time.  You do mention this disk is on a SAN so that does seem unlikely.  More on this here http://blogs.msdn.com/b/clustering/archive/2011/05/27/10169261.aspx
Comment: My concern is that due to severe licensing costs, we do not presently have automatic failover of disks between our two san hosts, meaning that if the site with the quorum disk goes down, one node and the quorum witness both go down at the same time. I would like to avoid any single point of failure like that.
Comment: I am currently thinking of adding a file server witness in a third location as a witness. combined with a quorum disk witness, that should prevent any spof scenario, I hope.


What should someone do if they find a similar working paper to their thesis after graduation?

Question: What should a student do if they find a similar unpublished working paper (say at a recent conference) after they have already defended the thesis and graduated? Suppose that the other group has been working on the paper for quite some time and presented it on different occasions, but the student only found out after graduation. Would it be a huge problem?
Comment: A problem to whom? What is exactly your concern?
Comment: If you already graduated and they merely presented but haven't published yet, aren't *you* the first to have published?
Comment: A problem to the novelty of my thesis...? I am worried that since they have presented their work elsewhere, theoretically speaking they are the first who came up with the idea, and my thesis could be regarded as a 'copy cat'.
Comment: Be nice and send them a copy of your thesis
Comment: Yes I am the first to have published. However I am not sure if presentation at conferences would count as informal publications? In fact I am more concerned about my reputation rather than actual publication in this case.
Answer: There is nothing you should do. You demonstrated that you can do independent research by coming up with creative work and defending it to a committee. The fact that others were doing the same at the same time does not invalidate your achievements: It may be that you will find it hard to publish the results in your PhD thesis given that there is now another publication, but the point of a PhD thesis is generally to demonstrate the ability to do independent research, and the latter is not affected by others having done the same.
If you are concerned about who was first: Unless you (i) came up with a theory at the level of General Relativity, or (ii) discovered something that can be patented and is likely to bring in millions of dollars in revenue, nobody actually cares about these sorts of things. To historians, it will be clear that you and the other group have been working on these things at the same time, and lawyers will not care unless there is a substantial commercial impact of your work.
Comment: Or (iii) you become a politician and some people are looking for all possible ways to discredit you.
Comment: @wimi No, there is no suggestion that OP *copied* or *plagiarized*. The work was just done concurrently.
Answer: Now, it would not be a huge problem.
It is common for research teams to work on the same problem without knowing of each others' work and sometimes come to very similar solutions and conclusions. If the thesis was accepted and published before the conference presentation, then you have the priority. If you unknowingly re-discovered some else's result, then usually nothing happens, so sometimes an academic committee investigates whether there was plagiarism. In your case, this is impossible since you could not possibly know about an unpublished result by someone else.
The polite way to handle this is to send a copy of your thesis to the other team and say that you were thinking alike. If the other team agrees that you published this first, then they might want to cite your thesis.
If you are not planning to work in academia, then the whole matter is of little import since the vast majority of employers does not care about your publications and priorities, unless this is a research institute. If your current employer wants you to get a patent on your discovery, then things become complicated.
Answer: Cite their work in future papers you send out for publication, if appropriate, just as you would with any other relevant work you're aware of at the time you send out the manuscript (incl. any revised manuscripts).
As others have suggested, consider sending them a copy of your thesis, which they could cite in their own future publications.  This would be especially helpful to the advancement of the science if you've made advances on parts of the problem they might have been getting stuck on, or if your independent works constitute independent validations of the same observed principles.
Don't worry about the past publications when you weren't aware of the other group's work. It's not reasonable to expect every researcher to be aware of every unpublished working paper even if directly on topic and even if previously presented.
Independent simultaneous invention/discovery is common, because multiple groups have access to the same memetic/conceptual building blocks and tools at approximately the same time.  See some of Steven Johnson's work, like Where Good Ideas Come From (trailer here), for more on this.
Even if it were previously published work that many people in your field were familiar with, the most serious likely impact would be earning an (in that case appropriate) reputation for not doing sufficiently thorough literature review and/or not being sufficiently well connected as part of the research community on this topic. Such a reputation might make funders a bit more hesitant to give you grant money (if they think it's more likely to go to reinventing the wheel than granting the same resources to someone else) but it's neither reasonably expected nor efficient to have you and every other researcher aware of every unpublished working paper with ideas being discussed among colleagues for possible improvement.
See also linked "related" questions on the right.


How to insert a Set into a column of type integer[]?

Question: I have a column of type integer[], created with the following query.
...
questions int[] DEFAULT '{}',
...

I am trying to insert a set of integers using Hibernate's query functionality.
Set<Integer> questions = randomQuestions();
Query query = session.createSQLQuery("UPDATE contestant SET questions=:questions WHERE email=:email");
query.setParameterList("questions", questions);
query.setParameter("email", email);
query.executeUpdate();

This doesn not successfully execute and throws and exception.
Caused by: org.postgresql.util.PSQLException: ERROR: column "questions" is of type integer[] but expression is of type record
Hint: You will need to rewrite or cast the expression.

How will I go about inserting my set of integers into the database?
Answer: query.setParameterList("questions", questions.toArray(new Integer[]));

try above , this should work.(Haven't tried though)


p-adic expansions for powers of p in the denominator

Question: I read this question and the answer to it, which deals witht the case when the number we are dealing with is a p-adic integer. How does one find a p-adic expansion for a number that has a p factor in the denominator? E.g. how do we find the 5-adic expansion of $\frac{4}{5}$? Is it the same as the 5-adic expansion of 4 with the digits shifted one to the left?
Answer: Start with the expansion for $4$, then just divide by $5$. Note that this corresponds to moving the decimal place over by $1$, since if you write the series as
$$4=\sum_{i=-\infty}^\infty a_i 5^i$$
then dividing by $5$ just gives

$${4\over 5}=\sum_{i=-\infty}^\infty a_i 5^{i-1}.$$
Answer: $4/5 = 4\cdot 5^{-1}$ is already the $5$-adic expansion. $4/5\not\in\Bbb Z_5$, but $4/5\in\Bbb Q_5$. Remember that elements of $\Bbb Q_5$ can be expressed by sums of the form
$$
\sum_{i = n_0}^\infty a_i 5^i,
$$
where $n_0$ is some integer (possibly negative) and $a_i\in\{0,1,2,3,4\}$ for all $i$. $4/5$ is already in this form, with $a_{-1} = 4$, and $a_i = 0$ for all other $i$. In general, you find the $5$-adic expansion of a nonzero fraction $a/b$ by factoring out the highest power of $5$ you can from both the numerator and denominator to get $\frac{a}{b} = 5^k \frac{a'}{b'}$, where $5\not\mid a'b'$, and then find the $5$-adic expansion of $\frac{a'}{b'}$ using the method described in the other question (basically via long division), and finally shift the expansion of $\frac{a'}{b'}$ appropriately depending on $k$ (multiply back in the $5^k$). The $5$-adic expansion of $\frac{a'}{b'}$ will need no negative powers of $5$, as you've factored them all out to obtain an element of $\Bbb Z_5$ (in fact, an element of $\Bbb Z_5^\times$).
(So, in short, it is simply the $5$-adic expansion of $4$ with the digits shifted.)


Transnormal function and isoparametric function

Question: Let M be a connected complete Riemannian manifold and denote by $\nabla$ and $\triangle$ the Levi-Civita connection and the Laplace operator of M, respectively. A non-constant function f of class $C^{2}$ on $M$ is called transnormal if
\begin{equation}\label{RK 1}
 |\nabla f|^{2}=b(f)
\end{equation}
for some real function b of class $C^{2}$ defined on the range of $f$, and  $f$ is called isoparametric if, in addition to the first equation, it satisfies
\begin{equation}\label{RK 2}
  \triangle(f) = a(f)
\end{equation}
for some continuous real function a defined on the range of $f$. The first equation implies that the level sets of $f$ are parallel to each other. The second equation implies that a level hypersurface has constant mean curvature.
Qustion: If $f$ is transnormal function and  the level sets of $f$ are parallel to each other, how to prove that $f$ is isoparametric function?
Comment: It displays nicer if you use `\Delta` instead of `\triangle` for the Laplacian operator.
Answer: For spaces of constant curvature this has been done by Élie Cartan in Familles de surfaces isoparamétriques dans les espaces à courbure constante.
In general, however, your claim is not true. See Theorem 1.4 in Transnormal functions on Riemannian manifolds by Reiko Miyaoka.


getting up to date contents of an iFrame

Question: Is it possible to get up to date contents from an iframe? Lemme explain the problem I am encountering:
function modify_iframe(url){
  my_iframe.src  = url;
  iframe_content = my_iframe.contentDocument;
  //....code to modify the content goes here,,,,
}

The first time I call modify_iframe(url_a) it sets the source as I would expect but the iframe_content is a blank document.
The second time I run modify_iframe(url_b) it sets the source as I would expect but the iframe_content is actually that of url_a.
So it seems that contentDocument is not returning the contents of the new source, but rather the source before it was changed.  Anyone know why that is and if there is a way around it?
Additional background info: We have been adding an event listener to fire off on the iframe load event which occurs when the src is changed. This was giving us the contents when calling contentDocument; however, users were being prompted that our site had unauthenticated content even though we use https for everything including the src. After removing the event listener we no longer receive the unauthenticated content warning, but the contentDocument of our iframe is always one step behind as described above.
Answer: Um, first try using a setTimeout to wait for the page content to load. But that's not a nice solution. What browser are you testing on? If it were me I would try to get to the bottom of the "unauthenticated content" error prompt.


Reincarnation confuses me

Question: There's the theory of reincarnation, which means that when you die, will be reborn as a different person. My problem with this is that it confuses me that we won't have any of the memories from that time. For instance, I could say that my consciousness was there in the 1800s with a different person, but I'd be confusing myself because then I'd ask myself why I'm not back then right now. To which I reply that that's because I'm in 2015 right now with no recollection whatsoever of life in the 1800s, but then it goes in a loop in my mind, so if anyone knows about any clarification or wants to speculate too, I'm open to all ideas.
Comment: Perhaps when you are between worlds you recover you're identity as a single unitary being; still reincarnation is an idea more associated with Indian philosophy than Western - it's probably best looking there.
Comment: Actually reincarnation was a fairly common concept in the West until it was deemed heretical by one of the early church councils. But I think it would be better answered if the question was not closed but moved by a moderator to Hinduism SE.
Comment: But I wasn't asking regarding Hinduism. I was asking in general. Many religions have a theory of reincarnation, but I'm not trying ask a religion-based question. Just a general one regarding the idea of reincarnation without any religious or ideological ties, and I thought that Philosophy seemed to best suit those parameters.
Answer: There must be something that gives content to the assertion that I and that person from 1800 are the same person . Since we do not inhibit the same body, the common factor should probably be in the memories. Here are two related excerpts from John Locke's classical memory theory of personal identity:

Self depends on Consciousness, not on Substance.
  SELF is that conscious thinking thing,--whatever substance made up
  of, (whether spiritual or material, simple or compounded, it matters
  not)--which is sensible or conscious of pleasure and pain, capable of
  happiness or misery, and so is concerned for itself, as far as that
  consciousness extends. Thus every one finds that, whilst comprehended
  under that consciousness, the little finger is as much a part of himself
  as what is most so. Upon separation of this little finger, should this
  consciousness go along with the little finger, and leave the rest of
  the body, it is evident the little finger would be the person, the same
  person; and self then would have nothing to do with the rest of the
  body . . .
Which shows wherein Personal identity consists.
  This may show us wherein personal identity consists: not in the identity
  of substance, but, as I have said, in the identity of consciousness,
  wherein if Socrates and the present mayor of Queenborough agree, they
  are the same person . . .

From what I've heard personally I think that reincarnation theories usually involve the belief that past lives can be remembered, in principle, even though they usually aren't remembered. That is, if you are properly gifted, or properly trained, you will recall your past lives. There is a lot of internet material about reincarnation memories. See for example here.

Reincarnation confuses me


File explorer needs to be restarted w/out admin priv. - HOW?

Question: In Windows 8 how do I restart explorer without admin privileges?
Answer: The Explorer is launched via normal user rights, so users should be able to restart it, too. The new Taskmgr required admin rights, because of the ETW network/disk tracing. If you use Process Explorer, you should be able to restart Explorer with user rights.


Facebook Like Box is Broke

Question:
Possible Duplicate:
I cannot get 'show faces' to work in the like box

Go to the like box app page:
http://developers.facebook.com/docs/reference/plugins/like-box/
Put in my profile:
http://www.facebook.com/thenetipot.net
Hit return to generate the new preview.
Turn off stream. Leave faces as shown.
You will note no faces are shown.
Now change the height to 500 and hit return to generate again - some now start to show up! You can increase it from there to 600, 700, 800 but the box is to big then and you can never get the wrap to work out neatly.
The other thing noted is if I login to my facebook user account with the standard height  (not the page owner account) - I see 3 friends show up in the like box, so perhaps there is some sort of security profile thing going on?
But I don't know what privacy setting that could be, as put in anyone else's URL and you will see the box neatly displayed with 10 people shown who will not be direct friends of your facebook account e.g. as with the following n the app URL box /smartpassiveincome
Answer: You've posted this question three times now. I would suggest that if the canned plugin that Facebook freely provides is not working out for you, to hire a developer to use the APIs to create your one that works to your needs. Make sure you have purchased a support package from that developer so in case you need any tweaks done after it is built or if facebook changes their API breaking your code (happens all the time).

Facebook Like Box is Broke


unbraced length of the compression portion of a long member

Question: I am designing a truss. the bottom chord in the first two panels at each end or at the supports are in compression and the rest of the bottom chord is in tension. there is no lateral bracing along the whole bottom chord. what do you think the unbraced length of the compression portion of the continuous bottom chord should be. I don't think we should use the whole length of the bottom chord since the tension part just would not buckle. should I use the length of the compression portion? but there is no lateral restrain where the compression portion meets the tension portion?
Comment: I am not quite catching the picture of it, perhaps some illustration or sketches will help? As far as I know, unless both sides of the compression member has pin end, you would need to consider factorizing the length of the member to obtain the effective length.
Comment: Twice the length of the chord.
Comment: The continuous bottom chord can be considered pinned at each end of the truss. Portion of the bottom chord is in compression. How do you factor that portion. More specifically the portion is by the support. Say couple of panels from the support. The middle part the bottom chord is in tension. It shouldnt be that hard to picture it in your mind. You can consider the whole length as unbraced but I think that is conservative.
Comment: Or I think we can have a column pinned both top and bottom. Apply a downward force from the mid height that is high enough to have tension in the top half of the column. Is the unbraced length the length of the column or half of the column?
Comment: Solar Mike. Just saw yours why?
Answer: Generally speaking the main application I can think of for trusses with unbraced compression chords is pony truss bridges. The AASHTO (ugh) Guide Spec for pedestrian bridges might have some information. I also believe the American Wood Council's NDS might have a paragraph with prescriptive requirements for unbraced wood truss chords in compression. It really depends on the material and what code you're designing to. I think the general idea of anything you find, though, will be that you need to either:

Go with the conservative full-length assumption.
Brace it.
Mathematically demonstrate according to some accepted methodology that the truss web members and connections are torsionally strong and stiff enough to brace the chord internally (i.e. looking at the truss globally as a single beam and checking it for lateral-torsional buckling).
Do a fancy advanced second-order analysis that explicitly models all system imperfections, any reductions in stiffness due to partial yielding, etc. so you can just throw the concept of effective length out the window entirely (most common for crazy curved structures drawn up by architects that defy any conceptual simplifications like "effective length").

I definitely agree that a sketch is needed, though. For example, it might help demonstrate why the ends of the bottom chord are in compression. Without a picture, right now the two possibilities I'm thinking of are:

The truss is restrained at both its top and bottom chords and is behaving as a fixed-fixed beam.
The ends of the bottom chord are only in compression in certain load cases due to some sort of applied axial load, like a braking crane, but the whole chord is in tension in the absence of such loads.

In scenario 2, it MIGHT be justifiable to treat the compression portion by itself as an axially-loaded, cantilever post.
Comment: to make it simple you can just consider scenario 2. of course we can always brace it as we did but the client with no knowledge of it think the brace is nuisance and will take it out. it is not happening now it might happen in the future when he decide to make it prettier. without the brace we can always assume the whole length of course which i always do. but I need a correct answer of it. what do you mean by cantilever post. just be simple in scenario 2 it is L or L/2. I dont think it is L since it is not the same as you compress the whole length and it will not buckle the whole L.
Comment: I kind of think in scenario 2 it is L/2 although there is not a brace at the mid height. but obviously if you just isolate the lower half of the post somehow it gets restrain at both ends of its own or it will not stand there. and the compression load only is going to buckle the lower part and definitely not the upper half.


What are similar scriptures like the Yoga Vasistha?

Question: I have really enjoyed studying the yoga Vasistha and like to read other scriptures that revolve around the same topic with the same depth to it. What are some other scriptures that fit that bill?
Comment: I am not sure in what context you are looking for a similarity to Yoga Vashishtha. Its major theme is using self-effort for enlightenment. Similar texts would be Narada Bhakti Sutras, Patanjali Yoga Sutras and Ashtavakra Gita which use devotion, a disciplined path of yoga, and a balanced path respectively as means to enlightenment. Also, Kenopanishada uses 'questioning' and Kathopanishada uses 'knowledge of after-life' as a path to enlightenment.
Answer: I know of only one scripture ,which is comparable to the YOGA BASISHTHA; that is the BHAGAWAD GITA .In both these scriptures ,a balanced view of the four types of activities in human life--Gyana,Yoga,Karma and Bhakti , is presented. Other scriptures ,HINDU or NON_HINDU , discuss only one or two aspects of these activities .Religion assumes that the main objective of Human Life, is to attain Liberation or  Enlightenment .Even Non-Religious activities , where material pleasure or success are main objectives , are also composed of these four activities.
Answer: There is the Moksopaya which is similar in structure and contents, also forming a dialogue between Vasistha and Rama containing roughly 30,000 Sanskrit verses (source). In fact, it was this text that formed, presumably, the foundation of the Yogavasistha. I have not read it to be sure, and as far as I know, there is no English translation available.
You might also be interested in the Shiva-rahasya-purana, available in a staggering amount of 100,000 sanskrit verses. This text is also left untranslated as of yet. There are however various English translations of the Ribhu-gita, which forms the sixth part of the full text. (source). One such example is found on archive.org. Although the Shiva-rahasya-purana is categorised as a Shaivite text, the Ribhu gita is said to expose Advaita-vedanta.
It would help if you specify the specific topics you enjoyed from this text.


How can I transfer etherbase status to another account within mist?

Question: After importing a wallet from JAXX to Mist, I wish to have the JAXX account having Etherbase status, instead of the default Geth one. However, I see no visual indications on how to do this within Mist.. Can anyone offer an explanation?
Comment: Can anyone answer?
Answer: This is a console-based solution and an untested one, at that. If you run geth attach while Mist is running, you can probably connect to the running geth instance. Then, you can do the following:
eth.accounts; // list your accounts
miner.setEtherbase(yourdesiredetherbase) // Set your etherbase. Not sure if this does what you want or if it's persistent.


can elm327 (bluetooth,wifi) adapters read and clear airbag(srs) codes?

Question: There are a lot of bluetooth and wifi obd adapters but only a handful of them(e.g blurdriver) claim that they can read and clear abs and srs codes, so I'm wondering whether a cheap elm327 based adapter can deal with srs and abs modules?
Comment: Beware that many ELM327 adapters out there are knockoffs and don't support all OBD-2 protocols. I have one, only worked on a 2008 Hyundai, didn't work on any other cars I've tried.
Answer: Most "cheap" or "universal" type code readers are only going to be able to do things that are exposed as OBDII parameters.  The car manufacturers are free to do whatever else they want using whatever proprietary protocols they want.
Air bags are not a part of the OBDII spec, and thus requires a special reader.  Some readers might have the right protocols and may be able to read the airbag codes, but even then they might not be able to clear the code for technical or liability reasons.
Also, there's not a huge demand for a device that can do this because the airbag and SRS systems normally require other special tools that are out of reach for most do-it-yourselfers.  They are critically important and delicate systems.
Comment: That's correct. For the records, let me add that it's usually not a problem of the hardware, but of the software. As long as the ECUs speak UDS or KWP, even a cheap ELM327 clone can read out the – vendor specific – trouble codes. However you need the proper data base to be able to interpret them correctly.


tried downloading ubuntu 15.10 installer crashed computer useless

Question: i tried downloading ubuntu 15.10 but the installer crashed while installing packages. Now my laptops boots up with some bugs no internet and installer wont open.
Comment: What is your question? Also, can you please add a little more detail? What did you do, what did you want to achieve and what happened instead? Did you encounter any warning or error messages? Please reproduce them in their entirety in your question. (see [How do I ask a good question?](/help/how-to-ask))
Answer: You did not actually ask any question, but I'm assuming that you want to install 15.10 and regain a working installation. I would create a live CD or bootable USB stick using another computer, boot the broken computer from that and install the new Ubuntu. That should fix your problems.
Just follow the instructions here for easy ways to switch to Ubuntu
Edit with details if computer does not automatically boot from CD or stick:
Enter Bios (watch out for this message during start up about which F-key to press, maybe F12?) and change the boot order so that CD or USB stick are preferred over your hard drive. Save these changes and reboot. In case your computer cannot boot from a USB stick, try a CD. (This may be the case for old computers)
Comment: downloading it now and i will contact if there is a problem. thank you mate
Comment: made the bootable usb drive but when i reboot it just goes on to normal booting
Comment: See my edit above
Answer: Hot normally a problem, if you have access to a working pc and a dvd burner.
Reburn the ISO inage on an new DVD-R blank, or erase the existing DVD-RW disk anf reburn it.  I'v encountered many "hidden" errors in optical disks that can clobber you good, but just redo and try again.
But you may not even have to fo that.  Use a lens cleaner and soft cloth or tissue and wipe the shiny underside of the disk clean, leaving no streakmarks, spots, or fingerprints behind.   Only handle the disk by its edges like you would carry a small turtle by clenching the edges of its shell with one hand and keeping it level.  If it is too wide to hold this way, use the edges around the inner hole. either with an outer edge or spread two fingers in the hole to provide a wedge against dropping.  Windex or a bit of mild detergent should work nicely, just get it all off after cleaning and leave no waterdrops on the surface.
Once you boot up the ISO, you can either go to Try or right into Install.  If you go to Try, you can mount the partition you were trying to and examine it for hour user accounts and contents.  WE are going to save that by not reformatting the partition during the install.  If you want to play safe, you can copy the folder /home to a different drive or partition first.  Uou probably will have to open a terminal throu Dash (top icon on left side) and type in "te".
You then click on Terminal.  With that open you type in seither sudo -i, and after the Enter key, you type in nautilus and another Enter key.  Now the File Manager (Nautilus) can do things the normal user can't.  you can also access the mounted partitions and drives by doing a cd /m*/*/ command.  This puts you where a dir command shows you the partition and drive names for those that are mounted.type in cd , and you are in the base or root point on that drive.  It's base to us now because it is not active, but when you install to it and boot up, it becomes the new root.
A dir or ls command here shows you all of its system folders and a few files.

More software can be installed at this point if you have enough RAM, but it is all temporary, and the amount that can be added is restricted to the amount of RAM you have.  It all goes away when you reboot.  You can write to a device at this point and that will last.
I use to advise people they could use the command rm -r ./[!h]* and wipe out everything except the only folder that begins with "h", that being /home/ where all user accounts and data reside.  But you really don't need to and it is safer not to.  In fact the whole process of using the Terminal was not necessary, but back then I did not know that.  It was part of my learning curve at the time.  Maybe you learned something to.
In fact, we did not have to Try the LiveCD at all, but could have gone right to install.  But this way, you can use the laptop while the install is taking place, to get on the internet and check your webmail, visit Facebook, or go back to Dash and type something like "ma" to being up the majongg game, or "so" to get and idea of what software you can install after the install is done.  Otherwise, the ten or so minutes required for the install just gives you a short slideshow of what you get with your new install.
It comes down to the install method you pick once the Installer begins running.  You will be asked questions like if you want it to reformat the whole DRIVE, not just this partition, and it will then install a new logical volume manager scheme if you allow this.  That wipes out everything on the drive, which I don't want, but you might.  And if you have multiple partitions or want to keep Windows, you don't want this either. You will not be able to repartition the drive later once you are under an LVM either, without starting over from scratch.  I prefer to use Ext4 for each partition and set them up with a tool like gparted or use the install process itself to add, delete, or resize partitions when I get to that point.  Note that if you elect NOT to reformat, you must user the same same format type and not resize the partition.  You only want to change from "Do Not Use This Partition" and designate it as root by selecting /.  But you can't do any of that under this choice.
The second choice will divide the drive up between Windows or other installed OSes and create a new partiton just for itself.  That means converting existing partitons to new structures and mappings to retain their content, and that takes a real ling time and can have problems.

The ONLY way I will install a LiveCD is to use the last, "Something else" process.  This is where YOU make the decisions, not a piece of software.
It takes a bit more expertise, but you can get online help. But before this point, you will be asked if the Installer can unmout mounted drives.  Say yes. as your intended partition is still mounted.  There are circumstances where you should say no id installing from an ISO image of a LiveCD that is on a partition, but that is not the case when it's being done from an actual CD or DVD disk.  While in Try, you could right-click on the partition icon and do a unmount and avoid this message, but if you forget, it gets taken care of here.
You reach a point in the process then where you see all the attached drives and all the partitions.  Only the first drive may appear on the acreen, but in the upper right portion of the inner window is a small scroll list where you can pick a different drive instead, if you have more than one.  Warning though:  If you pick a USB drive, make sure you also pick it to be the destination for the grub installation.  That is in the little space where you see the .../sda displayed.  If you change /sda to point to the USB drive/partition, the boot process will ONLY WORK properly when that USB drive is plugged in.  If you screw up and it gets changed, don't worry.  Reboot into the install you want to be the normal one by having the USB drive plugged in for the boot to work, and once in the desired install and having your Desktop up, open a Terminal and type these commands to fix the problem:
sudo update-grub; sudo grub-install /dev/sda

This will switch the primary install choice to that partition.  If you have the USB drive still installed, it will bew picked up as a alternative.  Unplug it and it won't be.  But if leftin, your next bootup when the USB drive is out will cause grub to complain and wait a time for you to decide to insert it by hitting "m" first, or to skip it if you hit "s" instead.  That little bit of aggrevation and loss of time never gets better.
But to get the same treatment on the USB drive, you have to have it installed and targeted with the sudo grup install command, but have its /dev/ name replace the sda in the ... /dev/sda command above.  Note that you might accidentally pick a partition like /dev/sda1, which it will do, but complain about what isn't there, and you can't normally boot up this way anyway.  So best not to.
Ihe installer for Ubuntu will create the /home folder and minimal user account under the name you gave it IF THEY ARE MISSING.  But if you already have them there, it will leave them intact WITH ALL YOU USER DATA AND FILES UNDISTURBED.  Everything related to the system folders are deleted.  You cannot add new folders under /home because that is limited to one or two user accounts.  BUT YOU CAN ADD NEW FOLDERS AT THE ROOT OR / LEVEL, and they will survive as well.  Ihis is important, because as super user (sudo , sudi -i, or even sudo su root), I have the power to do this, or take other steps as described below
:
    sudo mkdir /hold; sudo cp -rfp /home/ /hold/
This is a complete copy using reiterative, force, and preserve privileges options of all user accounts to the backup /hold folder.  Good for later recovery efforts if you mess things up in the future, but you can still get into the partition.  Of course /hold could be on a different partition, so this could be a safeguard both ways and you could in effect have cloned installs or even the same user stuff under different installs, a good way to see if you might want to move up or sideways to another Linux distro in the future.
The alternative approach is to use dd (duplicate drive) or rsync.  With dd, the older method, the two drives have to have the same exact geometry as to cylenders, tracks, sectors, and all that.  rsync is a powerful tool, but has a weakness in that it wants to keep the newest version of any files copied. In other wors, it goal is to syncronize two or more PCs as to certain or all folders and files. You want that ability with cp, you add the -u (update) flaf to the -rfp to make -urfp.  The order of these flags is not a problem, so if you want to make a word like -furp or -purf, it still works fine.
The problem with cp is that you find it is weak on wildcards, and has no other include or exclude abilities.   The same weakness is shared with dir, ls, and stat.  But find, tar, grep, and rsync are among the commands that separate file name/type from path in the initial request and also add in include and exclude directives (find not so much though, as it requires these to be individualized on the command line, possibly led by standalone -o to express OR rather than assumed AND, and possibly preceded by ! or ^ to indicate NOT.  An example of find would be:
find \/ a ! b -o c

Expressions are resolved in a left to right order,and wild cards are allowed.  Other operators like -readable -excuatable -type f -purge and [-delete can also be used, and effect results up to that point.  -ourge is a misnomer in that it would be better named -avoid or -skip.  Because that is whar it does.  =purge really means skip certain folders and their content in terms of subolder and files.
And find does not always get it right as to what you are looking for, but it only checks particulars about the folders and files. so is fast and gives you details the others don't check for,  It's not absolute about distinguishing whether a file is binary specific or actually one of the many text types, so its results need to be captured to file with >, >>, | tee files(s), or | tee -a files(s) and checked further.  In Windows, there are three methods for detecting types:  The letters after the last period in the file name are its extension, and/or the first word (2 chars) that make up the start of the file.  Those are the primary ways.  But under Windows, they added associations in the Registry where certain extensions map to one or more applications.  Then the user decides which of these to actually use.  That one then takes precidence in the future, becoming the new default for that user.
While some extensions from the DOS days are considered traditional, these were always two alphas, meaning letters, which are 26^2 in number or 676 in all, from AA to ZZ.  If you consider lower case as being different, you could have 52^2 or 2,704 types.  Seems like a lot, but real plain jane text files can have any two characters present, and even binary files can
possibly match up. Further, DOS and Windows treat upper amd lower case letters the same, which limits it to the initial 676 combinations.  So you pretty much have to see if the related app (program) recognises it or not, or be on a witch hunt for what program it might fit to, and there are thousands of programs out there.
But even in unknown or misadentified file types, and with the MacOS and Linux that assume no extension association for the most part, something has to show whether a file contains primarily text, usually in Unicode or ASCII, but possibly EBCDIC and other forms.  The first decision is whether it is a 16-bit (word) code like Unicode, or whether it is only 8-bits like ASCII or EBCDIC (an old IBM mainframe code).  For Unicode, you first check every other byte to see if there is consistency there or not.  If so, you then scan the other odd bytes and see if they match a text pattern like ASCII or if Unicode,a different written language as specified by the other 8 bits.
Sounds complicated, but actually it does not take too many tests like this on a file to see if yes, it is a written language of some kind, or no, it is a binary file.  It is the ratio of visible symbolic codes when compared to non-visible codes in the possible language under consideration.
But even as a binary file, it may conform to certain known types.  Through a process of trial-and-error, you could effect a program that can identify a likely binary type and even a possible doc or spreadsheet type, regardless of presence or absence of an extension, and even recover the text groups that appear in that file and put them in a new text file for further study.  In other words, if your partition got really hammered, as long as you can recover parts of the file, you can get most of your text back, simply because text has to follow certain rules.
If you encrypted your files, which is a excellent idea because otherwise you are at risk of malware reading them to get personal data, You probably  have a high degree of certainty of their protection.  But it can never be 100 percent certainty that you are completely protected. As long as you alone have the encryption key, even the average hacker can't get to your data.  But to the above average hacker, you have merely presented him with a challenge. This is because we are talking software here, and there are numeouseways to attack software, and the internet leaves a door open for the attackers to get in.  And often if they don't come to you, you can be lured into coming to them.  And either you open the files and read them into RAM where they are again plain text, or they master how you do this by observing and recording you doing your thing , then send that info back by the internet.  Ehen they are ready, they can hit with you with a hidden process to use your exposed steps and load up other encrypted files and harvest them for information and send that back as well.
You have the encryption key, but not the method of encryption used.  You could run into serious problems when attempting to work from a LiveCD to recover encrypted files and folders.  A part of the reason is that under the LiveCD, you are always ubuntu.  But when you made the encryption methos your default, you were your username.  If that is a factor, you may have deep problems which only becoming your username with the same encryption key can resolve.  This is all theoretical, as I've not used encryption myself.
This is because the encrypt/decript could be enhanced in some way with information related to that specific install or user. like incorporating the same UUID and hidden password into the key process. This would make the folders and files unreadable if just copied to an alternate drive or uploaded to a pirate's PC via the internet.  What's being used, and how it's being used, are simply not known at this point.
Tokeep it from being too restrictive on the user, What you probably have insteads is an encrypt/decript process that just uses the key you come up with and maybe your username.  It it included your password as well, then you lose the option to change your passwords on occasion.  However, that does not rule out physical characteristics of the PC, such as name, model number, and/or serial number in the creation of a complete enctyption key.  That increases security, but really limits where the files and data can reside and be accessible.
It may be futile anyway.  Encryption is just software, and anything that is software can be hacked by anyone who is expert at it and puts enough effort at it.  And when the same software is used worldwide and is publicly available, even documented to help developers, the task is not so much about unraveling the code, vur is more a question of which libraries, modules, APIs, and programs are handling the encryption/decryption process.  And in memory the contents of those files is revealed, so they can just steal it from there if they want.
0And they can even implant their own coded processes to  re-encrypt everything with their own key and negotiating a ransom electonicly so you can get your files back by purchasing the key from them.  No guarantee they will actually send you a key or that it is the right key.  There is no honor among thieves, and another transmission may be their undoing, so you aren't likely to get your files and data back even if you pay.
They go after anybody, as they share their methods with others of like mind, and what eventually entraps them is the money trail.  The monwy has to get back to them somehow, but that is a major undertaking in its own right, trying to track down money transfers over the internet, and they attack once and move on, setting up new accounts for the purpose.  There are three things you can do for better protection:  (1)  Back up your user accounts frequently, and keep older backups in case recent ones prove to be no good.  (2)  Put your backups somewhere else, like on USB drives, other computers, or in cloud storage.  Somewhere that if this PC gets hit, you can recover your content from another location.  USB drives are particularly good if you only use them for backups and keep them disconnected otherwise.  (3)  Get off WiFi and Bluetooth and other transmissions.  If it's in the air, they can get it.   Go wireless and through an ISP, get behind firewalls, and hope that is enough.
Malware protection works, to a point:  That point being, it can only protect you from what has been discovered about these attacks, the development of "signatures" (pattern recognition), the propagation of those signatures (often once a week, not every hour or every day), and the time taken bu the user to run the full scans needed to see if ANY of the files on you system had been been infected by the newest viruses detected.
And since no one company's product does all things well or have the same signatures, you get 3 to five of the best, give each an allotted time for
full scans, and hope the overlap catches maybe 98% of the KNOWN bugs out there.  But there are always new ones showing up.  Fortunately, most of the new ones are adaptations of others, and share pretty much the same signatures, so it is maybe a bit better than it sounds.
Me. I got off Windows over a decade ago because it is the biggest PC software target in the world, and people who stick to it don't even know that they have great alternatives in Linux like Ubuntu.  In the 7 years I've been on Ubuntu, I've had only five scam emails reach me where someone wanted my personal data.  My ISP , Cox.net, trapped the rest.  Then Thunderbird warned me the addresses given and URL given were bogus, but did not directly show me the real address.  On the other hand, Slimjet, a free and top-knotch web browser,  not only warned me again, but showed me the bogus URL link and opened and sent a report for me to people who investigate these matters.
I wasn't going to provide any peraonal data, but I quickly determined that the account was closed, possibly as they had already taken one fish and had quickly moved on.  Or maybe the complaints before mine had brought the law quickly on the scene.  But the email address was from an email provider in Britian, which shows you how widespread the threat is now.
Your safety is in keeping essential data off your pc or hand-help where intruders can find it.  Or use unconventional ways of storing or coding it so that it escapes detection.  The better known your methods are, the more likely that information will be taken from you, because the better known and more prevalent approaches will be attacked first.  That's one reason Windows had become so vulnerable.  There are other reasons related to Windows, but more on that further down.
I also sometines do two installs, one behind the other, for the same user.  After the first install, I use Try again and get into the sudo mode and move /home to /keep or /house.  So you still have the raw user account mas
de, but not in /home anymore/  I avoid format by using Something else again and make exactly the same account again in the new .home created. and

Different things to try, different ways to manage and attack the problem.  The big thing is, Linux allows this by  the separateness of /home as it leaves it alone it already there, and the LiveCD gives you real Linux power even on a CD or DVD.  Windows is a purely propretary product designed to only work from the PC where originally installed. and while there have been efforts at CD and DVD workarounds, you can't really master Windows because it is prohibited by law.  If you do a reinstall, it sets up new accounts under prior names and hides the old accounts and their contents.
An Administrator can work around this, but it is a pain in the neck.  And if you do the reinstall just to get control back, you lose all the added patches, fixes, and added software you once had, because the Registry is virginized again. An administrator can back up the Registry against the possibility of future corruption. but that's planning ahead, a task that has to be kept up as new software is added. Or after the Registry is cleaned.  Or purged by malware protection software.  The Windows' solution was to let the user set a number of saved recovery points, so you can go back to a better time.  That helps, but I find it a less than favorable solution.  First, it eats up drive space to save what Linux calls a "snapshot".  You can do the same thing in Linux, but I never bother.  Too many easy workarounds from the command line.
So with Windows, you have days of catching up again, and its almost as bad.  If you revert to the initial install from the hidden D: drive, which cannot be done piecemeal so that your settings, added software, and personal files and data are saved.  If you somehow keep your personal data intact, you have days of gradually getting Windows patches and bug fixes  downloaded and installed, with frequent reboots. Many shutdowns are held up because windows does not implement all the updates until the end, and you are warned not to power off Windows while this is going on. Occasionally they pull these dixes together into an SP. which I think of as a Super Patch.  It's a big collection of previous patches so that you just need to be that one, then do a reboot, and you are caught up to that point.  There are few if any actual enhancements in terms of new features or capabilities, as these are all reserved for the new release scheduled somewhere in the future.  And you will normally have to buy that new release when it comes out.  Your release is old news and will soon cease to be supported.  Win10 was an exception when it came out, because Win8.x was so vad that many people paid to revert to Win7 instead of waiting.  They were so angered that they were not included in the Win8.x replacement that they exxentially forced Microsoft to relent and credit them with a free upgrade to Win10 if they could prove their PCs had initially had Win8.x installed on it.  But now I've heard many prefer Win7, which has less in the way of annoyances on it. Miceosoftis out of touch with what people want or need.  It is geared to give them what Microsoft thinks it can persuade them to buy,  If you wanted a good stable Windows, you could have stopped at Windows 2000, or at worse, WinXP.  WinXP was a restampted version of Win 2000 with stiff license verification and validation added so that they could beat down counterfeits coming out of Asia.
Only verified installs could get Windows patches, and they made sure of this by forcing IE to be recognized as an integral part of Windows, then making sure only IE could poll for and get the fixes.  They even forced Windows to prove itself as valid, and otherwise display a warning that it was not the real thing on the screen of cloned or pirated copies.  Not easy to do when it isn't even real Windows, but they found a way.
Linux is entirely different.  I get new releases and patches about twice a week, and it is only when the kernel, or core, is enhanced and recompiled on my own PC is a reboot indicated, and that can be delayed until later.
A typical automatic update is over in less than 10 minutes, ans shutdowns are close to immediate.  When I reboot, I have full choice as to whether I use the most recent compile or an earlier one.  And it is all free, the download, the install, the upgrades, everything.  Anything where money is involved is either a request for a small donation or a small fee, of a few dollars when the appearance of 3rd party software choices is asked for by the user.  Not the numdreds of dollars needed for upgrading Windows and buying other new software that

So you made the right move to Linux, which is very pointed at meeting user needs, not craven desires.

If Linux gives you any problems, just ask for help as you did.  You will find it in spades.  Most are short, but having heen in your shoes a few timea, this is the summation of my experience and what you can do to help yourself.  If too long or detailed for some minds here, I can place on a cloud and supply a link back.  Those interested enough can follow the limk.  Those not interested can skip it.  I will copy and paste this to a text file in preperation for a shootdown from the Admin here.  Quite a few of my threads and post have gotten this treatment in the past.


My father is forcing me to wear the hijab

Question: My father have been forcing me to wear the hijab for a couple of months now, is it permissible? For context he didn't advice me gently but instead used violence and threatened to murder me if I don't wear a headscarf, it have been affecting me mentally and made me grow resentment towards him. My mom supports him and doesn't see anything wrong about it which also made me grow some resentment for her.
Comment: You don't indicate your age or country. In many places, threatening murder would be considered child abuse or assault. Your father seems to have a far worse problem than simply disagreeing with your headwear. You might consider consulting your religious leader or social worker about him (not about this specific issue), or if it is serious enough the police.
Answer: It is obligatory upon you to cover your áwrah and observe the hijāb, and it is impermissible for you to reveal your hair and beauty to non-mahram men.
You may not like the behaviour of your father, and it can be understood that you would not like it, but you must remember that a Muslim man who has ghayrah will not tolerate his daughter to reveal herself to men, and will be angered by it, and he is to ensure that she covers herself properly to the best of his ability.
You may also dislike the advice given here by myself, but it is for your own good:
Observe the hijāb and make your dunyā and ākhirah better, your parents will be pleased with you, and more importantly you will please your Lord.
May Allāh make it easy for you to obey His Commands.
Comment: But threaten to kill her? I find that ridiculously excessive. At the most, Allah encourages respect and dignity to his religion. Such violence would indefinitely scare Muslims away especially if it's their parents threatening them.
Answer: Complete hijab and chastity is the command and advice of God, the Merciful, to all believing girls and women; O you, O Prophet, say: O Prophet! Tell your wives, your daughters, and the wives of the believers to put down their veils. This is best done so that they are known and not harassed. The veil, in a way that covers the beauties and adornment of a woman and protects her from the eyes of vulgar and uneducated people and those contaminated with animal lust and evil states, is a Qur'anic commandment, a human duty and a moral program. According to various narrations, the principle of hijab has been created since the time of the Holy Prophet (PBUH) so that, for example, we read in history that after the revelation of Surah Noor, Aisha praised the women of Ansar for observing the hijab.
It can be said that Islam has considered the following aspects of the philosophy of hijab: 1. The value and respect of women: a precious and precious gem such as a woman, a strength in the divine treasury of hijab, from robbery, looters and those polluted with sludge Sin will be safe. When women are not seen and their pure and innocent faces are not exposed to the eyes of the people, the flame of lusts and airs, the fire of aspirations and instincts does not rise to disobey and burn the purity of a nation and destroy the spiritual foundation of a country. 2. Psychological relaxation: Sexual instinct is an unsaturated feeling and if released, the tendency to it becomes more and more. On this basis, Islam has issued special instructions to moderate this fiery instinct in men and women. In the meantime, the special duties of women are to refrain from any self-decoration in order to attract the attention of men. 3. Strengthening the family bond: Assigning sexual pleasures to the family environment and within the scope of legitimate marriage, strengthens the bond between the couple and causes the couple to be more connected to each other. 4. Community Stability: The introduction of sexual pleasures from the home environment to the community weakens the workforce and community activities. 5. Spiritual successes: The veiled woman has chosen God from herself and God. Such a choice gives a different mood to his spirit of thought and action and gives meaning to his cover, making it a logical, God-pleasing action in line with his evolutionary movements, which has manifested in his inner beauties.
The veiling of a woman is a clear manifestation of her piety. In his speeches, the Supreme Leader mentions the hijab as a manifestation of spirituality and says: For many years, the West has fought with spirituality and with the manifestations of spirituality. Hijab has been one of the manifestations of spirituality that the West has never been accustomed to. 6. Physical and mental health: Religious dress is a message of chastity, personality and God-fearing Muslim woman, and men in society not only will not covet such a lady and praise her purity and decency, and on the other hand her body and beauty in the shadow The hijab he wears will be hidden from the eyes of non-mahrams. In this case, the woman in her stronghold of hijab will be safe from the poisonous gaze and annoying words and the thugs of the society, and her inner peace and security will be established. The hijab and religious cover of the female guardian is one of the polluted eyes and possible harms that give the woman peace and security, and the more complete this cover is, the higher the percentage of security and protection.
Contrary to what opponents of the hijab criticize, the hijab does not paralyze half of the community; The Islamic ruling on hijab does not preclude any social or economic activity; What paralyzes the power of society is the lack of hijab and the promotion of free sexual relations and polluting the work environment with erotic pleasures. Some of the methods of promoting hijab are: 1. Teaching hijab in schools. 2. Encouraging women and girls to observe the Islamic hijab. 3. Scientific, cultural and artistic activities in the field of culture of hijab. 4. Promoting a culture of zeal. 5. Necessary monitoring of mass media. 6. Effective activities of the three forces in promoting and spreading the culture of hijab. 7. Enjoining the good and forbidding the evil. 8. Rational and logical strengthening of hijab among women.
Ref.: https://civilica.com/doc/423507/
Answer: According to the Qur'an, women should cover their entire body, including all their hair, body, and legs, from non-mahram men, but they can leave the face and hands round from the wrists down. Regarding the necessity of covering the feet from the wrist down, it is not obligatory during prayer, but from the point of view of the non-mahram it should be covered (1). Abdullah Javadi Amoli, referring to the verse "Zalak Adni An Ya'rfan Fala Yuzin [106]" says: Hijab is to respect and honor a woman who is not viewed by non-mahrams as an animal [107]
106. The Holy Quran, Surah Al-Ahzab, verse 59
107. Woman in the Mirror of Beauty and Glory, Abdullah Javadi Amoli, page 242


Do I need to know the curve for ECIES decryption?

Question: Let's assume that I have key pair generated using the following curves: brainpoolP256r1, brainpoolP320r1, brainpoolP384r1 or brainpoolP512r1.
Do I need information which curve was used to decrypt message? Can I infer which curve was used based on the private key?
Comment: You cannot see from a *decrypted* message what was used to decrypt it. Could you update your question with the actual scheme used and if you maybe meant to test what curve is *needed* to decrypt the message?
Comment: Do you need the modulus and/or the curve equation when applying the decryption algorithm? Both of those will already identify the curve
Answer: This awfully looks like homework, but hey, here we go. Each curve has an order, which is the number of points on the curve (specifically, the number of points into a subgroup of prime order of the curve, but in the case of the Brainpool curves, the subgroup is the whole curve). A private key is a non-zero integer modulo the curve order; i.e. if the order is $n$, then the private key is a number between $1$ and $n-1$. In practice, the size of the private key, expressed in bits, will be close to the size of $n$ (the size in bits of an integer $x$ is the integer $k$ such that $2^{k-1} \leq x \lt 2^k$).
Curves brainpoolP256r1, brainpoolP320r1, brainpoolP384r1 and brainpoolP512r1 have orders of size 256, 320, 384 and 512 bits, respectively. Thus, look at the size of your private key; this should allow you to infer which curves you are talking about.
(Technically, a 255-bit integer, for instance, could be a valid private key for all four curves, since it would be in the accepted range for all four curves; however, probability that a private key, chosen uniformly in the range for brainpoolP320r1, ends up being a 255-bit integer, while it had a whole 320-bit range to chose from, is less than $2^{-35}$, so it won't happen often. In that sense, your answer won't be absolutely guaranteed to be correct in a mathematical sense, but it can be a good guess nonetheless.)
Comment: @MaartenBodewes The encoding is described in ANSI X9.62, and this has been imported into [RFC 5915](https://tools.ietf.org/html/rfc5915). I did not bring it up in my answer because chances are that it is some homework with the integer spelled out as an integer, not encoded. Indeed, if the private key is encoded as per X9.62, then it will be part of a structure that also include an OID for the curve, and the question is moot.
Comment: Often the number is encoded as a *statically sized* integer (in an OCTET STRING), so the issue in the last section doesn't arise. I had to look this up for somebody and I at least came to this conclusion given some RFC. Now which RFC I have to look up.
Answer:
Do I need information which curve was used to decrypt message?

ECIES (the algorithm indicated in the tags) uses hybrid encryption. The message for hybrid encryption can have any size and value. It is therefore impossible to see what algorithm has been used to decrypt the message. Information about the decryption is required to determine the curve used.

The key length can be determined from the public key that is part of the ECIES ciphertext message. From that it should be possible to iterate over all known standardized curves with that same size and find the curve by performing the decryption. You would need the private key for that of course.
If it is a brainpool prime curve - as in the question - then there will really just be one candidate (e.g. brainpoolP256r1 for 256 bit public key). So it is possible to determine the curve without involving the private key.
So it is possible to determine which standard curve is used for encryption / required for decryption.
---

Can I infer which curve was used based on the private key?

Generally the curve is considered part of the private key and encoded with the other information (such as secret $S$) about the private key. A common encoding format is X9.62 which contains either the curve parameters or an OID indicating which curve is used.

If you just have secret value $S$ then you should be able to determine the size of the curve by the encoding: generally the private key is encoded in as many bytes as required to encode the order of the curve (using the minimum number of bytes) - left padded with zero bytes.

Generally the private key will have approximately the same size as the order of the curve - which determines the key size. The chance that the private key is of a size that fits a smaller curve is really small. As indicated by the answer of Thomas, the chance that a brainpoolP256r1 bit private key fits a brainpoolP224r1 key is about one in $2^{32}$ when encoded using the minimal number of bits. This chance decreases to one in $2^{64}$ for the larger 320, 384 and 512 brainpool prime curves.
So even if a non-standard, minimal encoding of the secret $S$ is used then the curve size and therefore the curve should be easy to determine with a high level of certainty.
---
You would be out of luck for unpublished proprietary curves of course; it is not possible to determine the domain parameters from just the secret $S$, the public point $W$ and/or the ciphertext message.


What exactly is "voltage drop" across a circuit element?

Question: what exactly is "voltage drop" across a circuit element? I don't quite understand what this means.
Comment: If you found an answer helpful, consider accepting it. This marks the question as cleared up.
Answer: If you have a simple circuit with resistors, the voltage at the source decreases throughout the circuit. At the positive terminal of a battery for example, you might have a voltage of 9 V, while the negative terminal can be taken as the ground potential 0V.
The voltage in between those terminals (that means through the circuit) decreases from the positive voltage 9V to the ground potential 0 V.
How does it decrease? We assume that we have perfect conductors as wires, which means that they have the same potential at every point, i.e. at the beginning and the end of the wire, the voltage is equal. The only points in a circuit where the voltage can decrease are the resistors in that case. In front of the resistor is a higher voltage, and behind it a lower voltage. The difference is the voltage drop. It corresponds to the amount of power dissipated in the resistor and is proportional to the resistance.

Here is the schematic of a simple circuit. As you can see, there are three resistors in series and a voltage source of 9 V.
A current of $0.5 mA$ flows through the circuit, and it flows through all circuit elements. We can calculate this current by finding the equivalent resistance of the circuit. For a series connection of three resistors, we just add their resistances:
$$R = R_1 + R_2 + R_3 = 3 k\Omega + 10 k\Omega + 5 k\Omega = 18 k\Omega$$
From $U = R I$ we can find the current flowing through every element:
$$I = \frac{U}{R} = \frac{9 V}{18 k\Omega} = 0.5 mA$$
Now we can find how much voltage drops at every element. It is proportional to its resistance. Since we now know the current and the resistance at each element, we can calculate the voltage drop.
For the voltage that falls off at $R_1$, we write: $$\Delta U_1 = R_1 I = 3 k\Omega \cdot 0.5 mA = 1.5 V$$
Similarly for the other resistors we get $5 V$ for $R_2$ and $2.5 V$ for $R_3$.
In the circuit above we can see how this changes the voltage levels at each part of the circuit. Coming from the positive terminal of the voltage source, the voltage is 9 V. It stays this until it reaches the first resistor. At the front of the resistors (in direction of the current, clockwise), the voltage is 9 V (the red part), but the voltage behind the resistor is lower: it is now only $9 V - 1.5 V = 7.5 V$ (the yellow part). The voltage dropped over the resistor. If you'd probe the voltage behind the resistor, you should measure 7.5 V.
Similarly this works for all subsequent resistors: the 10k resistor will drop 5 V, which means that in front of it we have a level of 7.5 V (yellow), and behind it $7.5 V - 5 V = 2.5 V$ (green). Finally, the last resistor drops 2.5 V, bringing the voltage at the end down to 0 V (blue).
Answer: when electrical current flows through a circuit component (easy example: a resistor), the resistor dissipates power; as it does, the voltage decreases steadily from the high-voltage side to the low-voltage side. this decrease in voltage is called the voltage drop.
In the case of a resistor of resistance R with a voltage difference across it of V volts, the power dissipated is equal to (V^2)/R.
Answer: What exactly it means is, how much the opposition the circuit element is doing against the current flow..!!
If the circuit element has no resistance, meaning it doesn't oppose the current flow at all, the voltage drop across that element will be absolute zero. But that's true only for superconductor.
In all normal case all circuit elements will have some resistance and they oppose current flow and thus drops some voltage across them by obeying the Ohm's Law.
Answer: There is nothing special about the term "voltage drop" - it is just a voltage across a particular component or any part of a circuit.
It is typically used in the context of a circuit with a known total voltage, in reference to voltages across specific parts of the circuit, especially, when we want to know how the total voltage is distributed between various parts of the circuit.
Let's say, we have a battery that measures exactly $9$V. We connect it to a circuit consisting of two components connected in series, say, a resistor and an LED.
A typical question here could be: "What is the voltage drop on the resistor?" or "What is the voltage drop on the diode?", which is the same as asking "What is the voltage across the resistor?" or "What is the voltage across the diode?".
Let's say, we measured those voltages and came up with $7$V on the resistor and $1.97$V on the LED. We re-measure the voltage on the battery and it is $8.98$V. So, we say that there is $0.02$V voltage drop on the internal resistance of the battery.
But that leaves $0.01$V unaccounted for. So, we say that there must be another $0.01$V voltage drop somewhere in the circuit, perhaps, on the long wires or on the contacts.
Answer: Voltage is a term which is sometimes confusing because people use it different ways in different contexts. Technically, voltage is the difference in electrical potential between two points. Electric potential is a physics concept which describes how much potential energy will be added or removed from a system if a unit charge is added or removed.
For example, if the electric potential (I like to use the symbol $\phi$ for electric potential) at a point is 93 V, then adding a 1 coulomb charge at that point will add 93 J of potential energy to the system. Next, if we move that charge to a point where the potential is 100 V, we have effectively added 100 J but removed 93 J, for a net change of 7 J. The voltage, potential difference, ($V=\Delta \phi$) between those points is  +7 V. On the other hand, if we started with the charge at $\phi = $100 V potential point and moved it to the $\phi = $93 V potential point, we would have a voltage, $$V=\Delta\phi=\phi_{final}-\phi_{initial}=-7\text{ V}$$ and a potential energy decrease of 7 J. That potential energy is converted into some other form of energy, depending on the system.  This decrease of potential, or negative voltage, is commonly called a voltage drop.
I personally don't like adding the word "drop" to voltage. I simply say voltage, and I always emphasize which end of a circuit element is higher, because if the voltage "drops" going left to right, then it "rises" going right to left. The word voltage by itself is enough to convey a difference of potential.


What happens if a series of EM waves pass through an inductor?

Question: Seeing that an inductor takes an alternating current and produces a magnetic field.  An EM wave is made of an electric field, and magnetic field propagating through space, so can a series of EM waves passes through an inductor, would it induce a current in the inductor?
Comment: This is a good question as it goes to the heart of electromagnetism and what every good circuit design engineer has to think about when designing any circuit and why we shield circuits. EM waves are around us all the time we are literally existing in one massive, ever changing EM field and hence anything that can conduct electrons can have inductance and thus induce currents usually called noise!
Answer: Two answers:
Yes, you're describing a "loop antenna."   A loop antenna is simply an unshielded inductor that's being used to absorb some incoming EM waves.  In non-radio circuitry inductors are shielded to prevent this from happening.  Shielding can take the form of a ring-shaped toroid core, or an "E/I" shape core with the coil inside the slots, or simply enclose the inductor (or the entire pcb) in a conductive shell.
Besides loop antennas, another "inductor-like" antenna is the end-fire helix, where radio waves come in towards the end of the spiral, and are guided into the coax cable.  Helical antennas are commonly used for satellite comms, since they're inherently circular-polarized, and will pick up signals from distant dipole antennas at any random alignment.

Second answer: can waves pass through inductors?  Yes and no, because whenever a component is large enough that EM waves can fit inside, that component isn't a capacitor/resistor/inductor anymore.  Instead it has become a waveguide element.
For example, at high enough frequencies, a parallel-plate capacitor is no longer a capacitor, instead it's a halfwave resonator.   And with short enough wavelengths, all your wires become antennas.
An inductor, if wound single-layer on a cylinder core, can have several EM waves moving across it, because it has become a helical waveguide.   (Actually that's the basis of Tesla coil secondaries: they're quarter-wave helical waveguides, with one end grounded, and driven at a frequency where a reflecting wave builds up.  Like an organ-pipe, but for EM waves.)
The key point here is this: for normal circuitry (small components and long EM waves,) the "Waves" instead behave as AC b-fields and e-fields.  They simply become our familiar AC volts and amps.
On the other hand, if the first part of a wave is still on its way through a component, while the next part of the wave changes polarity, then at least one halfwave can fit inside that component, and it no longer behaves as expected.
Another way to say it:  inductors and capacitors must be small enough to remain well inside the "nearfield" zone where "nearfield" is a quarter wavelength at your operating frequency.  For example, at 2.5GHz wifi microwave, the "nearfield" is about an inch.  If your wifi component isn't far smaller than one inch, then it's starting to become all waveguide-y inside.  Instead try 10MHz circuitry, where electronic components won't act weird, as long as they're far less than 25ft long!
Answer: An inductor is coupled to a magnetic field, an inductor induces a magnetic field around it. A magnetic field also can induce a current in an inductor. So yes an "EM wave" will induce a current in an inductor. An "EM wave" as you call it (or only the magnetic field portion will also induce currents in any wire or loop of wire it travels next to and can be calculated with Amperes law


How to explain the reasons to change Phd. supervisor

Question: I spent a year with a Phd. supervisor. I am not happy from both aspects: relationship and academically. Is it ethical to change the supervisor? Should I explain the reasons for change in details to the prospective supervisor or just be brief? How to avoid getting the impression that the student is trouble-maker (if I explained details of problems) vs. avoid give the impression there is no real reasons for change or that the student is not serious enough (if I am brief)?
Comment: "Is it ethical to change the supervisor?": It's not an ethical problem. If the relationship with your advisor is compromised, it would be hard to complete a successful PhD, and it's better to change advisor. Depending on where you are, though, this could be more or less difficult.
Comment: It's all in your question already, avoid going into details that could make you look like a troublemaker, and do specify real, preferably academic reasons for the change. Make clear why you see your PhD work in the potential new supervisor's research direction.
Comment: Just say it wasn't a good fit.  Leave it at that.
Answer: You didn't say in what situation you need to explain this, which may change the answer.
If it is merely coming up in passing in a conversation, "It was not a good fit" is a good neutral way to give the general idea and leave it up to your interlocutor whether to pursue the topic or not.
If you are specifically asked for your reasons for leaving, a condensed 2-3 sentence version should be enough in most cases. Try to avoid placing blame, it is not a trial of who is right or wrong, you or your advisor. E.g. "our research interests do not align, I would really like to go more into topic B" rather than "he keeps making me do grunt work on things I hate". If you have academic reasons you probably don't need to go into the personal reasons at all, but if you do want to bring it up at some point, frame it as something like "our personalities do not mesh well". Stay carefully factual when recounting details. (This doesn't mean downplaying the issues. Think of a way to formulate it neutrally but still exposing the crux of the issues barefacedly.)
Generally, potential other supervisors will see themselves in the role of your current supervisor, so they will imagine that you will talk about them in the same manner as you will talk about your current supervisor.
Answer: You should definitely look to change supervisors, but you may need to consider the politics of doing so. Academia is a small world and it's possible that you'll run into your old supervisor again some day, or that they will talk to others who you work with, so it's generally better to be tactful.
My department had a Postgraduate Coordinator who was there to assist all the PhD/MSc students. Mine was very helpful when I needed to drop one of my co-supervisors because our working relationship had broken down. If your university has such a role, I'd strongly encourage talking to them about it; they may be able to help you smooth the waters with your old supervisor.


Is there a performance degradation when we ALWAYS use nullable value types instead of value types?

Question: Is there a performance degradation when we ALWAYS use nullable value types instead of value types?
Comment: Overflow
: not that you should worry about.
Comment: Not as big of a performance hit as having an IStackOverflowUser implementation also inherit StackOverflow itself.
Comment: to point out, I'm willing to bet that @MitchWheat knows a lot more about this than you so I'm gonna go with listen to him. @MitchWheat ~ You should've made that an answer :p ...
Answer: As Mitch Wheat pointed about above, no, you should not worry about this. I'm going to give you the short answer reason now, and later I'm going to help you discover more about what you're asking:

Write your code to be correct. Profile after writing so that you find the points that are causing you grief.

When you have code that constantly uses Nullable and you have performance reasons and you profile it and you can't find the problem yourself, then come ask us how to make it faster. But no, the overhead of using Nullable is for all intents and purposes not degrading.
Discover more about what you're asking:

Performance surprise with "as" and nullable types
Why shouldn't I always use nullable types in C#
C# Performance gain returning a Nullable Type from a SqlDataReader
Alternatives to nullable types in C#
Casting (int?)null vs. new int?() - Which is better?
Boxing / Unboxing Nullable Types - Why this implementation?

Now, having read all those pages, I hope you feel more enlightened.
Comment: That's an `ul` unordered list - `ol` ordered lists are erhn... ordered (numbered) yah know? ;)
Comment: What about memory? Since `obj.Value` can't be passed as a reference type (ref/in), it's necessary to assign the value to a new variable, doesn't this necess duplicating the value type as opposed to just assigning it to an ordinary type from the beginning?
Comment: oh, facepalm, I started to type UL the first time :p
Answer: It's the price of copying the entire value type: pretty much nil for things like integers, GUID's, etc., but it's large if you're constantly copying 512-KB value types (which you shouldn't be having in the first place) inside a tight loop.


How to switch between graphics on Dell Inspiron N5110?

Question: I have got a Dell Inspiron N5110 running Ubuntu 12.04. It has two graphic cards, Integrated Intel graphics And Nvidia. I was wondering if there is a way to switch between graphic cards. As the Nvidia card is using a lot off battery power I want the Intel card to be the default.
Comment: Are you sure that you are running on the nvidia GPU? I think your intel GPU is running your desktop while the nvidia card is sitting down wasting power. http://superuser.com/q/392098/47108
Answer: Is it one of their Optimus cards? That's what I have, and I use Ironhide to switch between cards. My laptop uses the Intel card most of the time, but when I need more power I run the application through optirun <command>.


is there way to make Server Core is the default startup?

Question: I want to know if i can install windows server 2008 "full installation" and put the Server Core default startup and make the server manager is just Secondary option.
is that possible? , and how can do it?
thanks for every one
Comment: I don't think you can. Windows Server 2008 server core is essentially a different product from the normal install.
Comment: Your question makes no sense. What does "Server Manager" have to do with it?
Comment: I also doubt it can be done, the whole point in server core is minimising the attack surface and hardware requirements by cutting out server manager and lots of other gui stuff.
Answer: In Windows Server 2008 and 2008 R2, you can not switch between Core and full server editions.  The purpose of core is to limit the files installed and services running. A reinstall is required to change them.
You can however, install Server Core edition and use Server Manager from another server to do most management tasks.


Add shortcut to custom settings

Question: Is there a way to create a shortcut or quick access button to custom settings in salesforce? I want sales team to easily add new values or remove existing without going into setup, but custom object seems too heavy since I will store key - value pairs, so it's just name + field with lookup relationship.
Answer: The best way to do this is to create a visualforce page that would expose the custom settings in a user-friendly way. This way you wouldn't need to grant their profiles the permission required to access that section of the setup.

Add shortcut to custom settings


Emacs connect to MySQL (MariaDB) non-interactively

Question: I am looking into sql.el, and I can't find a way to bypass creating comint buffer and setting some global variables in order to connect to the database.
This is less than ideal because I know the credentials, but I don't want to alter global variables which might be used for something else, and there is no way to just create a process and interact with it, or so it seems.
Ideally, I'd like to have a MySQL process, with which I could interact programmatically in an asynchronous way. I.e. the intent is not to let the user write queries, but rather to translate user's input into queries and to execute them as the program sees fit.
Answer: OK, I've found this library: https://github.com/skeeto/emacsql, and so far it seems good, so I'm going to stick with it for now.


Port storyboard to iOS4

Question: I'm a fan of Xcode's new storyboarding, but I'm annoyed it won't work on iOS4. I understand why it won't work, because it relies on new classes added to the iOS5 framework. However, it would be cool to be able to port a storyboard back to iOS4 somehow. A tool that outputted xib files for the individual stories, and code generation for segues.
If anyone knows of anyone else doing something in this area, I'd be interested in using it, since my app needs to support iOS4, but I'd like to move forward with Storyboarding. Can i have my cake and eat it too?
Answer: Nope you cant. Ended up gutting the storyboarding and going back to individual xibs.

Port storyboard to iOS4


Relationship between kurtosis and the center of a distribution

Question: Some have stated that kurtosis is the "movement of probability mass from the "shoulders" of a distribution into its center and tails" where "center" is defined as the range between $\mu \pm\sigma$. I was trying to find a proof for this but was unsuccessful. Can anyone point me to a proof of whether (i) larger kurtosis implies greater probability in the $\mu \pm\sigma$ range, or (ii) greater probability in the $\mu \pm\sigma$ range implies larger kurtosis?
Comment: Given that you already know the answer to this, I think a more broadly beneficial question would perhaps ask whether anything *can* be said about more in the tails or more near the peak when kurtosis increases.
Comment: If my internet connection stays up, I should have time to get back to this over the next couple of days. Which definition of more in the tails is that?
Comment: The 3 theorems are (i) kurtosis is between E(Z*4*I(|Z|>1) and E(Z^4*I(|Z|>1) +1, for all distributions with finite 4th moment, (ii) when the distributions are restricted to continuous with decreasing density of Z^2 on (0,1), then the +1 can be replaced with +.5, and (iii) for any sequence of distributions having kurtosis tending to infinity, E(Z^4*I(|Z|>b))/kurtosis -> 1, for all real b. The definitions of tailweight implicit in these 3 theorems are, for (i) and (ii), E(Z*4*I(|Z|>1), and for (iii), E(Z*4*I(|Z|>b).
Answer: I saw a very good reference that pointed out that these intuitive/graphic ideas are not really sound.  Kurtosis is often explained as (1) more mass in the tails; (2) less at the center; and (3) some shift relative to the 'shoulders'.  I have also seen the claim, as you say, where 'it shifts from the shoulders both in and out, so there is more in both the shoulders and tails.'  But all of that is very geometrical, and it raise the question of 'more than what'?  And it presumes 'shoulders', which are a vague concept.
I will try to dig up the reference, but I don't think you can prove what you claim.  Imagine taking a normal distribution, then take all points within 1-$\sigma$ and put them out at >3-$\sigma$.  That will have more kurtosis, I believe, but zero mass in the center.
I will try to dig up that reference, since he did a good job of giving both examples and pointing out that kurtosis is what it is - and while it may have some relation to variance or SD, it needs to be understood (like all moments) for what it is mathematically (which is simply a statistic based on expectations of points raised to a power).


Intermittent cold water from the hot faucet

Question: Why would cold water run from the hot water faucet (for about a minute), after the hot water was already flowing?  This happened in two washrooms, at different sides of the house, but not at any other faucet.  Hot water then flows normally.  This does not seem like a problem with a diverter, filter, hoses too close together or any of the other solutions proposed in related threads.  Any suggestions?
Comment: So you turn the faucet on and get hot water.  Then it goes cold.  Then it goes hot again.  Is that accurate?
Comment: Does this happen all the time? Where is the water heater in relation to the bathrooms?
Comment: Do you have a hot water tank or do you have a tankless water heater?
Answer: Water cools at different rates in different parts of the system
Basically, the pipes from the heater to the faucet are not in the same thermal conditions.
For example, pipes in internal walls are at indoor air temperature (say 20C) and pipes in roofspaces will be at (close to) outside air temperature (say 5C to 40C depending on where you live). If the pipes are full of hot water (say 70C) as they are after being used, all else being equal, the greater the temperature gradient, the quicker they cool.
Add to this that the thermal insulation between the pipes and their surroundings will not be uniform and its not unusual to get a part of the system that retains heat for longer than other parts. If you turn on the taps shortly after they have been used you will get "bubbles" of cold being pushed along.


Diminishing returns and economies of scale

Question: I was wondering whether these are contrary as one effectively says production becomes cheaper as production increases. To increase production you may need to upgrade from a standard machine to high capacity (like if a seemstress wanted to go from making friends clothes to a small buisness) which would cost alot more to produce more (diminishing returns). I know they are uneven but I'm I going wrong somewhere? Is diminishing returns an advantage of smaller buisnesses?
Comment: Possible duplicate of [Showing that production technology exhibits decreasing returns to Scale](http://economics.stackexchange.com/questions/14005/showing-that-production-technology-exhibits-decreasing-returns-to-scale)
Answer: In production with more than one input, "diminishing returns" refers to what happens when we increase one input while keeping all the rest constant. "Economies of scale" is a more informal term for "increasing returns to scale" and so relates to what happens when we increase all inputs by the same proportion (while, and this is important, we keep the technology unchanged).
Perhaps it could help you to revisit your example based on the above standard definitions of these concepts.
Comment: So don't these counteract each other when looking to increase production? @Alecos Papadopoulos
Comment: @SRawes They refer to two different ways to increase production, so in what sense do they "counteract each other"? For example, if one increases all inputs by the same proportion, one cannot examine whether diminishing returns for one input appear, because, by definition, we examine diminishing returns per input by keeping all the other inputs constant.