RTC interface with PIC16F877A

Question: I am newbie to embedded programming. My problem is I can write and read data to ds1307(by saying using I2C debugger). But my received data on LCD showing 0xE1 constantly for every changing second. Is it I2C debugger showing wrong data as reading data? Or my conversion is wrong, if it so, my data should change but it doesn't. I'm stuck here so hard.please comment where did I go wrong.
Comment: Welcome to engineering SE. I understand that you have a RTC, a micro and LCD. But I have trouble understand how they are connected and the relationship to the I2C debugger.
Comment: This is way too confusing.  Closing.  It should be obvious that your question relies on context you are not telling us about.
Answer: Ok firstly calm down, everything has an answer. you say you read and write data from real time counter by I2C debugger but can not by microcontroller; MCU stands between LCD and RTC right? and there is alternate read/write path to RTC, either MCU can access it, either I2C debugger is that right? so from all this i assume you have some kind of Development board with RTC,MCU,LCD, and a I2C debugger.
first, always try to think of these  electronic components as tiny micro cities. they all live by their own separate lives and communicate to each other by wires just as buses are used to connect cities to each other. if RTC responds to I2C debugger we can assume that RTC is powered and feels ok.
but LCD shows frozen values. you are not sure is this because MCU could not communicate to RTC...  or because MCU can communicate with RTC but MCU fails to pass this data to LCD. so there are 2 joints, either MCU->RTC is dead or MCU->LCD is in wrong format. firstly try to send couple of things to LCD. something, does not matter what. Hello world or something. if it shows well, then problem is certainly with MCU->RTC communication.

RTC interface with PIC16F877A


High-viscosity gel/polymer to suspend conductive material while it is being printed

Question: I currently doing research on 3d printing on circuit boards. The technique we are using is to put a conductive material, I.e ceramics/metal in a gel/polymer, to print the suspension and then when is complete to sinter away the gel/polymer. The problem I am having is the suspension needs to be thixotropic. Furthermore it must have a high viscosity i.e 500 cpa under low shear and to quickly drop to low viscosity as the shear increases
So far the closest thing I have been able to find is in this paper but if you look at the graphs none of them have a high enough viscosity and more importantly the drop to low viscosity under increasing shear is too shallow.
I have tried to use models like the ones in this paper but I am finding it quite difficult.
Does anyone have any suggestions to find more materials like the one I require? Thanks
Comment: Would something like [this conductive paste](https://www.youtube.com/watch?v=z4IGQ5JMP6g) work?
Answer: The material you are describing sounds very similar to the material used for Metal Injection Molding except that you want to print the material rather than molding it.
A company called MarkForged is making a printer called the Metal X that uses this technique of printing & sintering to produce solid metal parts.  Here is a article describing more details about the printer.
It sounds really cool.
If you investigate papers around those processes you may find what you are looking for since they are so related to what you are trying to do.


Understanding the Kruskal diagram for Schwarzschild spacetime

Question: I am studying Kruskal coordinates for my General Relativity course. On the book Spacetime and Geometry: An introduction to General Relativity by Sean Carroll, the author gives the metric in Kruskal coordinates $$\mathrm{d}s^2=\frac{32G^3M^3}{r}e^{-r/2GM}(-\mathrm{d}T^2+\mathrm{d}R^2)+r^2\mathrm{d}\Omega^2$$
and the Kruskal diagram with $\theta$ and $\phi$ suppressed.
How can I relate this diagram with a Minkowski diagram? What does the origin of the Kruskal diagram mean? The author then says that every point is a 2-sphere. How can I imagine this? Can I draw this diagram restoring, let's say, the $\phi$ coordinate in order to get a three-dimensional spacetime diagram?
Answer: You can relate the Kruskal diagram to the Minkowski diagram by realising that, because of the (-+++) signature, $dT^{2}$ takes the role of the time-like coordinate, while $dR^{2}$ takes the role of the space-like coordinate. You can interpret the Kruskal diagram as a "Miskowski diagram of curved spacetime".
You can therefore also introduce lightcones to the diagram by considering the $ds^{2}=0$ null geodesics. It is here where $\theta$ and $\phi$ are surpressed by choosing radial light ($d\phi=0$) in the equatorial plane ($\theta=\pi/2$). By setting these variables to a constant you are limiting the diagram to a 2-dimensional slice of the actual geometry. Though, the surpressed degrees of freedom still exist. For every point, you have neglected the 2-sphere-spanning coordinates. In other words: every point is a 2-sphere.
You can restore $\phi$ by rotating the 2D cut light cones to represent actual cones. Just like with flat space Minkowski diagrams.


Efficiently accessing arbitrary NDArray batches in mxnet

Question: Fitting convnets such as Resnet and VGG benefits from the ImageRecordIter python class, that allows efficiently loading batches from large collections of RGB images stored in RecordIO .rec files,
Does anybody know about equivalent facilities for large arbitrary input 2D or 3D matrices (for 2D, rows = items and cols = features, + channels in 3D)?
NDArrayIter requires loading the whole dataset in memory, which is to be avoided in my case (>40Gb data file). CSVIter does not allow straightforward shuffling, and works only for 2D matrices.
Answer: You can keep each data sample as a separate file and implement a very simple custom DataSet class following the reference code ImageFolderDataset


Strangers ID's in elements when save an .ai file as SVG in Illustrator

Question: I have a map of a floor with offices in it in Illustrator, and I need to add to each office drawn an ID to work with it in JavaScript. But the names of the offices have numbers and/or special characters, such "()" and "+" (i.e. "360 (IVO+IMR+IEC)"),and when I save it as a SVG file, the IDs looks like "id='_x33_60__x28_IVO_x2B_IMR_x2B_IEC_x29_'".
Any idea of why happen this? How can I fix it or avoid?
Answer: It looks like some of the characters in your file name are being turned into their unicode representation.  For example, the character '3' in unicode is '\x33', and your corrupt file name shows'x33'.  Also, '(' in unicode is '\x28', etc, etc.  This seems to not be coincidental.
I don't know what operating system you are running, but maybe you can check your settings for character display, language, or region, as this seems to be a character display problem on your system.  Hope you can get it solved.
Here's a chart of unicode characters, if you're interested:
http://www.utf8-chartable.de/unicode-utf8-table.pl?utf8=string-literal&unicodeinhtml=hex
Comment: Thanks for the answer. The OS is Windows 8.1, in spanish. Illustrator is in spanish too. I will check the properties and configuration of Illustrator.
Answer: For futures references, I resolved this adding a space with the space key at the begin of the ID (for some reason Illustrator prints me something like "_x33_60" if the ID was "360", while with the space at the beginning  i.e. " 360" prints "_360") and deleting the non-alphanumeric characters.


Connotation difference between "subscribers" and "observers"

Question: In the observer pattern, and similar, is there a meaningful difference between "subscribers" and "observers" in the wild, or in the lit? With RxJS and (functional) reactive programming, are the terms interchangeable?
Comment: And how do both of those relate to 'listeners'?
Comment: If you say "subscriber" people will assume a pub-sub system. If you say "observer", they won't.
Comment: Listeners also same, at least in Observer pattern
Comment: @gidds In plain English, observation is active whereas listening can be done passively. One could argue that an observer is the one who actively observes (i.e. keeps open the link to the observed target), whereas a listener passively waits for the target to transmit the message (meaning that the target is the one who maintains the link to the listener). However, I very much doubt that people make such a subtle distinction in everyday communication.
Comment: Just for clarification and for the sake of the question. Are you asking in RxJS context only or in general? If it's only in RxJS context, I think @Benjamin already answered `Subscriber - Implements the Observer interface and extends the Subscription class.`. If not, I found the answers to be a bit opinionated because they differ from framework to framework (see @Karl's answer)
Answer: Nearly all words used in programming are plain English terms that still retain all of their original semantics (or as much of it as applies to programming), since their purpose is to help English speakers explain technical concepts to other English speakers.

Example definitions of each term:
Subscriber (noun)

"a person, company, etc., that subscribes, as to a publication or concert series."
"a homeowner, apartment dweller, business, etc., that pays a monthly charge to be connected to a television cable service".
"a person who promises to donate a sum of money, purchase stock, etc."

Observer (noun)

"someone or something that observes."
"a delegate to an assembly or gathering, who is sent to observe and report but not to take part officially in its activities."

The definition leading to Observe (verb) has the following example definitions:

"to see, watch, perceive, or notice"
"to regard with attention, especially so as to see or learn something"
"to watch, view, or note for a scientific, official, or other special purpose"

The differences between the terms in English are that subscription tends to be either more deliberate, focused or proactive around a subject.    Observation might involve less focus or be a more passive activity.

These terms clearly have overlapping semantics in English, with the term 'observe' being far more general and abstract.  As Karl points out in his answer, they are often used interchangeably in contexts where any minor semantic differences between them aren't important, such as the example given in the question with ReactiveX.
In some specific contexts, there are more obvious reasons for choosing one term over the other,  for example, the Publish-Subscribe messaging pattern uses 'subscriber' to convey the importance of each recipient needing to deliberately express an interest in receiving messages.
While a 'subscriber' could easily be described as an 'observer' in this pattern, the term has weaker connotations and intent.  i.e. For a person described as an 'observer', it may simply not be important whether or not that person has actually expressed any particular interest in receiving some information.   However, in the context of the messaging pattern, 'expression of interest' is an important, distinguishing feature.
As always, naming things is a hard thing to do - people who choose between names like Observer or Subscriber need to think long and hard about context.
A word which is too general just risks losing the audience through lack of clarity or purpose.   A word which is already loaded with specific connotations risks misleading the audience if those connotations don't match the technical concept.
Comment: I also have the feeling that the term "subscriber" is used more often in contexts where there is a central messaging system (EventBus, MessageBus) where one can subscribe to messages/topics/events, while observer is more often used in cases where observers are attached to an observed entity directly.
Comment: Is there not a difference in delivery guarantee where a subscriber is a sub-set of all observers with that specific guarantee of delivery? A subscriber is guaranteed to 'see' all observable events for the duration of the subscription. An observer without a subscription has no such guarantee. I'd liken it to visiting a comc store and picking up the comic you've subscribed to every week but sometimes missing an issue of one you're not subscribed to. In tech that might translate to a connection failure meaning an observer misses an event but a subscriber would have that event queued.
Comment: @melkisadek Each person's expectations may be different, but personally I wouldn't expect an 'Observer' abstraction to be forced into taking responsibility for missed events, since that implies they would need to be involved in correcting the problem, possibly even communicating back to the event's origin (therefore no longer 'just' being an observer).   That seems like a [Leaky Abstraction](https://stackoverflow.com/questions/3883006/meaning-of-leaky-abstraction); where I'd hope a lower-level detail elsewhere would already have it covered, allowing the observer to remain fairly passive.
Comment: I was thinking more about the English Language difference between Observer & Subscriber. Both are essentially passive but a subscription needs setting up and I would expect access to the thing subscribed to for the duration of the subscription (magazine issues or Sky TV channels). An Observer would only expect to see what was available at the moment of observation (e.g. Library books that haven't been loaned out or Freeview TV channels).

As @Laiv mentions in his comment on the question, once you bring actual framework implementations into it, it quickly becomes opinionated.
Comment: @melkisadek That's what I mean by "expressing an interest" being of importance in the context of the publish-subscribe pattern.    However for the concept of an observer, whose dictionary definitions are pretty abstract and highly context-dependent, I don't personally see any clear link or connotation with reliability -- that seems to me like something which would depend entirely on specific context and not something belonging to the general observer concept.
Answer: The terms are mostly interchangeable, but there are subtle differences in specific implementations. For example, a Monix Subscriber is described as "an Observer with an attached Scheduler." I don't believe that's a universal distinction, though, just one of those difficult naming problems of programming where it's more convenient to use a synonym than an annoying compound name like ObserverWithScheduler.
Answer: In Rx speak an Observer is something that can get notifications from a data source and a Subscriber is an observer that can also unsubscribe from that source.

Subscriber - Implements the Observer interface and extends the Subscription class. While the Observer is the public API for consuming the values of an Observable, all Observers get converted to a Subscriber, in order to provide Subscription-like capabilities such as unsubscribe. Subscriber is a common type in RxJS, and crucial for implementing operators, but it is rarely used as a public API.

That's just Rx terminology - in a regular programmer discussion the terms are interchangeable even if they have slightly different but similar meanings a bit like arguments and parameters.


Transferring PhD departments

Question: I was wondering, I'm interested in both some aspects of pure math and some aspects of theoretical computer science. I'm currently in a PhD program in computer science at a pretty decent institution (let's say, top 5 in most TCS people's minds), but I think my interests are more mathematical than I had anticipated. (For example, I'm realizing I'm more interested in some areas of topology and geometry and connections to computer science.) Do you think it would be worth trying to transfer into the math PhD program/do you that would be viable? I'm just about to start my second year. It would likely set me back a year at least to pass the qualifying exam in the math department, but I sort of think that it would do me good to acquire a more robust background in math. Of course, this is a very individual consideration, but I wanted to get a sense of what the general feeling on this type of question would be before chatting seriously with faculty in the two departments. (I know that usually people move from math into CS, not vice versa...)
Answer: I can't balance your options for you, of course, but I'll give you a couple of things to consider if you haven't already.
One is the time to completion of your current degree project. If it is soon, then staying might be best and then moving gradually into your math studies, either formally or informally.
But another option than the one you mention would be to ask around to see if you can't find an additional advisor in math and work with both of them at the intersection of math and CS which you seem to be interested it. This pretty much assumes that you are not yet deep in the weeds of your CS doctoral research. You might be able to avoid the math qualifiers that way if you have already qualified in CS.
I would guess that there is already some collaboration between the departments at an institution such as you describe. You might be able to explore it painlessly without needing to make an immediate decision or burn bridges.
What would be on your credential when you finish would depend on a bunch of things, of course.
Answer: The first year is sort of a calibration period, so unless the stakes are too high, some fluctuation is to be expected. I usually advise people that dropping out or switching chairs during the first year is a much better option than being stuck for 3-4 years with a topic (or advisor) you found is not for you.
PhDs are hard as nails already, so why risk burning yourself out on a topic that doesn't match your interests. Matters like the level of your institution or in which direction people usually move seem secondary in this situation.
Regardless of what advice you get here though, being you i would go and talk to your advisor about this. Simply be open. They will more likely have a specific idea how to proceed, and who knows, maybe you can work out a pretty novel direction by involving a co-advisor.

Transferring PhD departments


"Logic Design" vs. "Digital Circuit Design"

Question: I'm aware that different companies have different definitions for job titles, but in general, is "logic design" the same thing as "digital circuit design"?
Answer: To me, the job titles are very similar, but not exactly the same. "Logic design," in my opinion, implies writing VHDL or Verilog to design digital logic to go onto FPGAs, CPLDs, or maybe even ASICs.
"Digital Circuit Design," on the other hand, means to me that in addition to (potentially working on) the HDL stuff, you are also designing the entire digital part of the board/chip/system - including working on the interfaces to the analog stuff. I would also think "digital circuit design" includes less "logic design" and more using ICs and off-the shelf components/IP blocks.
Now, this obviously does not have to be the case. The two job titles could certainly describe the exact same position, that's just my interpretation. If you're looking for a job in that area, the job description can probably provide some more information on what the particular job entails. If it's still not clear, apply to both and then in the interview you can ask for clarification.
Comment: "Logic design" was in use long before programmable logic was developed. It was commonly used to describe the process of developing digital circuits based on TTL and other logic families.
Answer: At Intel's career center (i.e., jobs.intel) I have found two positions that could help answering this question. According to their website, it is expected from a Logic Design Engineer [1] to:

Performs logic design, Register Transfer Level RTL coding, and simulation to generate cell libraries, functional units, and subsystems for inclusion in full chip designs. Participates in the development of Architecture and Microarchitecture specifications for the Logic components. Provides IP integration support to SoC customers and represents RTL team.

I have also found a Logic Design Engineer position at ARM [2] which agrees with Intel's definition. Therefore, in a very short summary, a Logic Design Engineer seems to design, simulate and debug RTL logic.
On the other hand, Intel expects from an Engineer for digital circuit design [3] to:

Conducts or participates in multidisciplinary research in the design, development, testing and utilization of information processing hardware and/or electrical components, mechanisms, materials, and/or circuitry, processes, packaging, and cabinetry for central processing units CPUs and/or peripheral equipment. Prepares specifications, evaluates vendors, and analyzes test reports. Ensures products conform to standards and specifications. Develops plans and cost estimates and assesses projects to analyze risk. Develops procedures, analysis and design for computer components, products, and systems. Initiates, guides, and coordinates overall design and development of new ideas and products. Responds to customer/client requests or events as they occur. Develops solutions to problems utilizing formal education and judgement.

Those tasks, in my opinion, seem to be more related to "project management" and "decision making" than to the actual implemention (not that this engineer doesn't get its "hands dirty"). Additionally, the Digital Circuit Engineer position seems to comprehend chip fabrication tasks, while the other position doesn't. Accordingly, it seems that for Intel there is a difference between the two job positions. However, I could not found a Digital Circuit Designer position at ARM. This could either mean ARM does not use this definition, or that there is simply no positions open at the moment.
Overall, I would advice looking into which positions each company offers and what they expect from each of them as presented definitions could easily vary for other companies.
Note: References will eventually expire as they are job positions. Therefore, I have inserted all relevant content from them in this answer.
Comment: Those job descriptions were probably written by human resource personnel, instructed by some group leader looking for some guy/gal for the job. I don't consider that definitions, just opinionated concepts. Over my years as engineer, I've been doing the same job under many names: digital design engineer, embedded engineer, hardware architect, fpga programmer, etc, etc. Job names are not the same as a definition.
Comment: @JHBonarius that's indeed true. That's why I pointed that those _could easily vary_. As the question's purpose is not clear, I thought that maybe showing some open positions could be interesting.
Comment: Considering the OP asked the question nine years ago, I'm not sure he's interested in current open job positions...


Generalized Hardy-Littlewood-Sobolev Inequality

Question: The Hardy-Littlewood-Sobolev Inequality says that
$$\text{for $p,q,r\in (1,+\infty)$ such that }\quad
1-\frac1p+1-\frac1q=1-\frac1r,\tag {$\sharp$}
$$
$$
\exists C, \forall u\in L^p(\mathbb R^n),\quad
\Vert{u\ast\vert\cdot\vert^{-n/q}}\Vert_{L^r(\mathbb R^n)}\le C
\Vert u\Vert_{L^p(\mathbb R^n)}.
$$
Setting $v_q(x)=\vert x\vert^{-n/q}$, we see that $v_q\in L^q_w(\mathbb R^n)$, which is also the Lorentz space
$L^{q,\infty}(\mathbb R^n)$ (the latter space is a Banach space when $q\in (1,+\infty)$).
Is there a generalization of Young's inequality such as
$$
\exists C, \forall u\in L^p(\mathbb R^n),
\forall v\in L^{q,\infty}(\mathbb R^n),\quad
\Vert{u\ast v}\Vert_{L^r(\mathbb R^n)}\le C
\Vert u\Vert_{L^p(\mathbb R^n)}\Vert v\Vert_{L^{q,\infty}(\mathbb R^n)},
$$
with $p,q,r$ satisfying $(\sharp)$?
Comment: Do you have a typo in the first line of your $\sharp$ statement?
Comment: @John Bentin : No, this is the same condition as the one for Young's inequality $L^p\ast L^q\subset L^r$ under $(\sharp)$.
Answer: See Corollary 2.15 in the paper

V.F. Kovalenko, M.A. Perelmuter, Yu.A. Semenov, Schrödinger Operators with $L^{l/2}_w (R^l)$-Potentials, J. Math. Phys., Vol. 22, No. 5, 1981, pp. 1033-1044

link to the paper on journal website
Comment: A textbook reference is Theorem 1.4.24 in Grafakos: "Classical Fourier Analysis". One way to prove Young's inequality is using the Riesz-Thorin interpolation theorem and similarly one can use Marcinkiewicz' interpolation theorem to prove the weak Young inequality. Observe that you can allow the endpoints in (#) for Young's inequality but not for the weak Young inequality.
Answer: The weak type Young inequality
$$
\Vert{u\ast v}\Vert_{L^r(\mathbb R^n)}\le C_{p,q,r}
\Vert u\Vert_{L^p(\mathbb R^n)}\Vert v\Vert_{L^{q,\infty}(\mathbb R^n)},
\quad 1<p,q,r<\infty,
\quad \frac1p+\frac1q = 1 + \frac1r
$$
is in fact a direct consequence of the Hardy-Littlewood-Sobolev inequality.
By the Riesz rearrangement inequality (a special case of the Brascamp-Lieb-Luttinger inequlaity) we have
$$
|\iint f(x) g(x-y) h(y) dxdy| \leq |\iint f^*(x) g^*(x-y) h^*(y) dxdy|,
$$
where $f^*$ is the symmetric non-increasing rearrangement of a function $f$.
Now,
$$
f^*(x) \leq C_n |x|^{-n/q}\|f\|_{q,\infty}
$$
and the claim follows by duality.
This argument has the advantage that it gives the optimal constant provided that the optimal constant in the HLS inequality is known (thus at least in the case $p=r'$), as opposed to interpolation arguments.
Answer: Inequalities like this are discussed in this paper of Nakanishi: http://epubs.siam.org/doi/pdf/10.1137/S0036141000369083
(See section two.)
As others have mentioned already, one can get estimates like this from the standard estimates plus interpolation.


How can I get a notification when a new Stack Exchange dump is made available?

Question: How can I get a notification when a new Stack Exchange dump is made available?
Answer: Unfortunately, neither Stack Exchange nor the Internet Archive provide any satisfactory way to track or alert about Dump uploads, see below.

You can see a user-maintained approximation of dump dates here.
Or login to the Internet Archive and only then can you see the history of dump uploads at catalogd.archive.org/history/stackexchange (Note the submittime column.)

The Data Dump nominally updates quarterly but my recollection over the years is that the interval and the release dates are rather sporadic.
For alerts about availability, the only current option seems to be to use a third-party monitoring service like Follow That Page or similar.

Things I tried and that failed:

Search Stack Exchange.
Search the SE Blog.
Search the Internet Archive for "track"/"watch"/"alert"/"monitor" capability. Found none.
Favorited the Stack Exchange Data Dump entry -- this added no useful alert activity, even on my favorites RSS feed.
Used Internet Archive's "Advanced Search" to create an RSS feed.  But due to design limitations such feeds are useless for update tracking.
You can create a JSON URL that returns the last update date, though.
So if you have some mechanism to poll that URL once everyday or so, that should show if something new is available.
Note that even archive.org's own wayback machine does not track changes to the data dump upload very well.


Restore from Time Machine after installing Bootcamp

Question: Can I setup Time Machine to backup my Mac and then install Bootcamp?
Then after installing Bootcamp, can I go back to that restore point so Bootcamp will be gone?
Answer: No, Bootcamp will create a fysical partition on your Macintosh HD. If you restore your Mac  with TimeMachine, the software will only detect your Mac-partition and restore it's data. It will leave your Bootcamp partition in tact.
If you want to get rid of the Bootcamp partition, just run the Bootcamp assistant again and it will allow you to delete the Windows partition with one mouseclick.
Comment: Can I put back the deleted Windows partition back to my Mac partition?
Comment: So you're asking for a solution to create a partition, delete it and restore it by a back-up software?
Comment: not really. since im not yet that familiar with my Mac, and I want to try out bootcamp, I just want to know how to restore things the way they were before should my installation of Win7 using bootcamp screw up. And I am anticipating a screw up because I do not have my Mac OS X Lion installer with me (Laptop is company issued), I heard you can install bootcamp/windows 7 without the Mac OS X installer DVD by downloading Apple's drivers on the web.
Comment: If you want to experiment with Windows 7, you can try out one of the virtualisation software. This creates and deleted Windows partitions on the fly. Try VMWare or Parallels to do so.
Comment: I have already tried VMs. But they are slow. And Ill be playing games and using heavy apps on Windows 7 so I guess Bootcamp is the way.
Answer: If something goes wrong, simply start Boot Camp Assistant again. You can use it to delete the Windows partition, during which process the Boot Camp Assistant will also (and automatically) merge the deleted partition with the Mac partition. It will do so without you losing any data from the Mac partition (but you will lose everything on the Windows partition, of course).
In other words, after you use the Boot Camp Assistant to delete the Windows partition, the partitioning scheme on the drive should be identical to how it was before you used Boot Camp and installed Windows in the first place.


Shopping for new Harmonica, what key is best?

Question: I'm shopping for a new blues  harp and I see on a lot of they say, all keys only.  What does this mean?
Answer: Can't understand why any harp would have 'all keys only' on it. Blues harps come in many keys, and decent blues players will have an armoury of at least half a dozen.
Reason being - blues harp works best using one that is not in the same key as the song. Song's in C - use an F harp. Song's in A - use a D harp. basically, count forward to the fourth note in the song's key. A-B-C(#)- D.
So if you play with a band which plays blues in different keys, you will need those appropriate harps. I used to do a particular open mic, and one guy would keep trying to make his one and only harp fit in every song, till somebody explained where the problem lay. Went out, bought several, can now play along in several keys!
The harmonicas which can be played in any key are those with a push button. But even they won't work as blues harps, unless the song's in G. That's because a lot of chromonicas are basically in C.
Answer: There is no "best key", but some of them are more preferable to others, and it all depends on who you are going to play with and which keys they prefer. Another thing that also affects it is which style. It is common to play in second position when you're playing blues, and that means that you are playing in a key one fifth up from the key indicated on the harmonica. So if you have a C harmonica, you will play in G when using second position.
But on the other hand, harmonicas are not very expensive. For your first, I'd recommend a regular C. Then just buy more as you need them. If you want to be serious in jamming with various other people, then you will need quite a few.


How to handle auto-backstab on my rogue party members?

Question: I went mage, but I have heard rogues are OP, but have the problem that they do not auto-backstab. How do I handle this? Is there a way to manually control the rogue to make him backstab turn-based mode, or should I just dump melee rogues if they approach me?
Comment: Can you clarify your question a bit? Are you asking how to manually control other characters? Or about how to backstab as a rogue? The way you have currently phrased your question is unclear.
Answer: There are several ways in which you can backstab an opponent.

You are attacking him from behind.
The opponent is stunned.
The opponent is frozen.

So if you manage to stun the enemy very often using your skills or your team mate's skills, then you'll also be able to get the bonus backstab damage without attacking from the back half circle.
Manually positioning the rogue is must if you want to backstab from the back half circle,  as there is no way you can alter the tactics to make the rogue position himself/herself behind the enemies.
Although one thing that is worth noting is that you need to have Coup-De-Grace for easier backstabbing.
Answer: You can take control of your rogues (or any party member) by simply clicking on their portraits, or using the F1-4 keys.
At any time during the game, you can pause by using the space bar, including during combat. When the game is paused, you can issue orders to your party members.
You can have a tactical view of the battlefield by zooming out.
So, during combat, you can simply pause the game, click on your rogue, click behind an enemy so your rogue will go there when you unpause. When he is there, you can either let him auto-attack, or pause again and order him to use a specific attack.
It is easier to backstab ranged enemies, as they do not move, but melee enemies can be backstabbed too : you just need to prevent them from turning around. Rogues and warriors both have skills to stun the enemy, and mages can freeze them or turn them to stone, preventing them from moving.
Answer: Backstabs in DAO occur when a rogue attacks anywhere from the back half of the circle of the enemy.
Since you do not want to manually control the rogue, then the only thing you can do is control the target's positioning.
If you are a warrior, you can use skills like taunt to turn enemies so their back is exposed to the rogue.  Other than that, manually controlling the rogue is the best way to get them to backstab.  Just move them to the backside of an enemy before attacking with them.


What is minimum safe bend radius for rg213?

Question: What is minimum safe bend radius for rg213 cable?
Comment: Check the specs from your supplier. I see several that specify a repeated minimum bend of 1.6" or 42mm. Your mileage may vary.
Comment: Once or many times? For RG213 a once-off bend around a 2" diameter cylinder is OK, but if it's a rotator flex loop then you'd want at least a 12" *radius*. The datasheet should give both figures.
Answer: It will vary from manufacturer to manufacturer. One general rule is not bend less than 10 times the diameter of the cable. So a cable that is 0.5 inches in diameter should have a radius of no less than 5 inches.
This for free formed loops. If part of a fixed assembly the bend radius can be less.
Much depends on the type of insulation used. Over time, the center conductor can actually displace the insulation and end up moving toward the shield. This will change the impedance and might eventually lead to a short.
Comment: Minimum radius is not mentioned in the specs for the cable from the supplier I have in mind so these general rules are helpful.


Dealing with dust mites

Question: I know a lot of people have dust mite allergy, so drop your tips here if you have any handy hints.
Good vacuum cleaners ?
Things that poison them ?
Bedding covers ?
tnx
Answer:
Vacuum frequently (little or no advantage to expensive models).
Vacuum everywhere feasible, e.g., under mattress, books and behind furniture.
Avoid forced air heating. Best is radiant, with no dust-gathering surface, and forced-hot water is also good.
Check with an allergist for ways to avoid dust and on desensitization (immunotherapy).

Dealing with dust mites


Convex hull of a triangle and a translation of it

Question: Say you are given triangle ABC in $\mathbb{R}^n$, and its translation A'B'C' such that A'B'C' is not coplanar with ABC. Must it be the case that the convex hull of ABC and A'B'C' is a triangular prism?
Comment: @Logan, thanks. For a minute I thought I had a counterexample to this. Oops.
Answer: Yes.
Note that for such a translation to exist, $n \ge 3$. Set A as the origin. Let $e_1, \ldots, e_n$ be the standard basis for $\mathbb{R}^n$.  Perform a linear transformation sending $\vec{AB}$ to $e_1$, $\vec{AC}$ to $e_2$, and $\vec{AA'}$ to $e_3$. It should be clear that the convex hull of $\{ 0, e_1, e_2, e_3, e_1+e_3, e_2+e_3\}$ is a triangular prism, and since invertible linear transformations preserve the combinatorial type of polytopes and commute with taking convex hulls, the original polytope was also a triangular prism.


How do I solve these integrals of wave function and operator?

Question:
First integral
$$\int \Psi^*({\bf r},t)\hat {\bf p} \Psi({\bf r},t)\, d^3r,$$
where the $\Psi({\bf r},t)=e^{i({\bf k}\cdot{\bf r}-\omega t)}\,\,\,$ and $\hat {\bf p}=-i\hbar \nabla$.
Second one
$$\int \Psi^*({\bf r},t)\hat {\bf p}^2 \Psi({\bf r},t)\, d^3r,$$
where the $\Psi({\bf r},t)=e^{i({\bf k}\cdot{\bf r}-\omega t)}\,\,\,$ and $\hat {\bf p}^2=-\hbar^2 \nabla^2$.
Comment: @Nick Kidman these integrals are actually expectation value
Comment: @nabla: But the quantum state you give is an eigenstate of momentum operator.. There is no variation in momentum, then.
Comment: @Karsus Ren how about uncertainty?
Comment: @nabla: It is momentum eigenstate, then there is no momentum uncertainty.
Answer: You want
$$\langle\hat A\rangle:=\int \Psi^*(r,t)\hat A \Psi(r,t)\, d^3r,$$
and since
$\Psi(r,t)=e^{i(kr-wt)}$
you have
$(\Psi(r,t))^*\hat p\Psi(r,t)=\\
=(e^{i(kr-wt)})^*(-i\hbar \nabla)e^{i(kr-wt)}\\
=e^{-i(kr-wt)}(-i\hbar (ik))e^{i(kr-wt)}\\
=\hbar k,$
and so
$\langle\hat p\rangle=\\
=\int \Psi^*(r,t)\hat p \Psi(r,t)\, d^3r\\
=\int \Psi^*(r,t)(\hbar k) \Psi(r,t)\, d^3r\\
=\hbar k \int \Psi^*(r,t)1\Psi(r,t)\, d^3r\\
=\hbar k \langle\hat 1\rangle,$
and similarly
$\langle\hat p^2\rangle=(\hbar k)^2 \langle\hat 1\rangle,$
which also implies
$\langle\hat p\rangle^2=\langle\hat p^2\rangle\langle\hat 1\rangle.$

The usual doctrine is that the wavefunction is a normed eigenstate, i.e.
$$\int \Psi^*(r,t)\Psi(r,t)\, d^3r=1,$$ which means $\langle\hat 1\rangle$ is equal to the number 1. The problem is that the norm of the plane wave $\Psi(r,t)=e^{i(kr-wt)}$, for which the integrand is $\Psi^*(r,t)\Psi(r,t)=e^0=1$, diverges for an integral $\int d^3r$ over an infinite volume.
I'd be tempted to just say you should define
$$\langle\hat A\rangle:=\frac{\int \Psi^*(r,t)\hat A \Psi(r,t)\, d^3r}{\int \Psi^*(r,t)\Psi(r,t)\, d^3r},$$
as then in this case $\langle\hat p\rangle:=\tfrac{\hbar k\langle\hat 1\rangle}{\langle\hat 1\rangle}$ and so the object $\langle\hat 1\rangle$ formally factors out in the computation in this case. But in general, the problem is more complicated than that. Maybe you find this thread illuminating, and there are certainly others on physics.SE regarding such issues.


Access to the markets for a country

Question: What does it mean for a country to have access to the markets. E.g: There is an ongoing discussion when Greece will follow a prosperity path in order to enter again the "markets".
Comment: @AlecosPapadopoulos I heard a rumor that if you are caught trying to sneak into the Markets you get a slap from an Invisible Hand.
Comment: @calculus No. Here "markets" refers to Financial Markets where the country could borrow directly from private lenders.
Comment: @calculus I am Greek, living in Greece, and I tried to enter the Financial Markets, and they wouldn't let me in. But I was able to sell some olive oil to the goods markets. :)... Seriously now, this is common knowledge.
Comment: @denesp Rumors. The Hand is very Visible. And it sings, as it comes and goes, a cute little song, with the title "The Tails are Greek". My head is a little fuzzy from the slaps but I think it went something like (in 3/4 tempo)  "No mountain as high as your interest  / No ocean as deep as your discount / Extreme Value Theory is no match for Youououou (pause).../ The Tails, belong to You!".
Comment: I think here it is meant, that if Greece would get competitive enough, then Greece is able to export its goods-especially to other EU-countries. Greece has more or less full access to the EU-market (e.g. no costums). Therefore it cannot be meant, that Greece has many and strong restrictions to export its goods. And if Greece has more exports than imports, then the greek economy get more money from the buyers abroad than the greek economy has to pay for the imports. This surplus can help to get on a prosperity path. The money can be used for investments, for example.
Comment: @AlecosPapadopoulos How do you know ?
Answer: When a country loses access to markets they mean access to debt markets. Here is a quote from a paper if you need a citation:

Greece lost access to credit markets when debt exceeded 130% of GDP,
  whereas Belgium successfully handled identical debt relative to GDP.
  What determines the highest debt that a country could repay, defined
  as "fiscal limit?" Can we estimate the fiscal limit for a country
  which has never lost access to markets? We use historical data on
  primary surpluses (surpluses excluding interest payments) and debt
  relative to GDP for six high-debt, developed countries, two of which
  lost access to markets after the 2008 global financial crisis, to
  estimate the behavior of the primary surplus in response to changes in
  debt. The high-debt countries include Belgium, Canada, France, Greece,
  Italy, and Portugal.

Predicting Sovereign Fiscal Crises: High-Debt Developed Countries (Daniel and Shiamptanis (2015))
Specifically, "closed" means that that the sovereign can no longer raise funds from capital markets. Depending on the specific situation, some entities within that country can continue to raise external funds. A business with significant assets or good prospects may be able to continue to raise funds even when the country cannot. In Greece, at least until recently, this was the case. See the article Greek companies get back on the road, with help from bonds.

Access to the markets for a country


Are there any mathematicians who expressed non-obvious sets of rules on how to do research?

Question: I recently saw a paper where there are presented some rules on how to learn mathematics (and do research) which were firstly articulated by Lagrange.
Are there any similar rules that were expressed before early 1800s by other mathematicians?
Comment: D'Alambert: "Allez de l'avant, la foi vous viendra"
Answer: Plato had a simple rule: learn geometry. This of course is well before the 1800s.
This is tempered by the time of al-Jabr who taught us to learn algebra.
Another heuristic is one by Newton who said 'he stood on the shoulders of giants'. This implies that one ought to study the works of the great masters of the subject thoroughly.
Another useful heuristic is by Solomon Lefschetz. Unfortunately this is after your cut off date, being in the early to mid 20C.
He had one simple rule: he said he wasn't interested in prettifying already established results, what he was interested was in original work that showed something new.
This is what he told the graduate students who were under his supervision.
Another heuristic, again unfortunately well after your cut-off date is by Atiyah who reminded students that there were a lot of gems in the work of older mathematicians and which had been forgotten. This, however, ties in with what Newton thought.


Need a judicial data set

Question: I need a dataset of textual documents of judicial data (any country for that matter) for the purpose of text mining.
Can anyone please let me know the sources for the same?
Comment: Welcome to Open Data SE! What kind of judicial documents are you looking for? Could you provide some examples?
Answer: Australian laws and cases (all state and federal jurisdictions) are online at: austlii.edu.au.
See for instance High Court (the highest) 2014 cases at:
http://www.austlii.edu.au/au/cases/cth/HCA/2014/
Federal (we call them Commonwealth; Cth) laws starting with letter 'M':
http://www.austlii.edu.au/au/legis/cth/consol_act/toc-M.html
etc etc etc...
Answer: In the USA, a court case is structured by a docket. The docket contains every piece of legal correspondence in the case.  Depending on the case, most of it is public record.  The federal US system for this is called PACER and is the single most over priced and ridiculous data access portal I have ever encountered. I hear Carl Malamud (data - liberator) is working on something.  To get around this silliness of paywalling public records, RECAP (the opposite of PACER) was established.  I think Carl may have had a hand in RECAP, regardless he should be thanked for making so many public US government documents more reasonably accessible to the public.
Check RECAP archives here:
http://archive.recapthelaw.org/
If you want something really big, look for famous cases like oracle v google.  Great amicus briefs in there.
Answer: More Australian examples:
Federal: Law/Acts: All letters:
http://www.austlii.edu.au/au/legis/cth/consol_act/
State: Qld : Law/Acts: Letter 'P'
http://www.austlii.edu.au/au/legis/qld/consol_act/toc-P.html
Answer: I had posted an answer about how to scrape the Canadian judicial website - see here.
Here is an example of the HTML for a court case: https://www.canlii.org/en/ca/scc/doc/2007/2007scc4/2007scc4.html
By building a list of URLs to court cases, you can then run them through an HTML reading procedure to get the text

Need a judicial data set


What is a source maps vulnerability?

Question: I was wondering if any can simplify the source maps vulnerability?. I've googled this vulnerability but can't get my head around this. Could anyone please help me to understand this issue and how do I investigate and find the issue?. All I know it's normally a '.map' file, is it correct and normally can be done by adding .map at the end of the js extension? Something like example.js.map.
Not sure how to tell the difference between minified and unminify code?
Answer: JavaScript or similar languages may be transpiled, minified or "packed" before deployment to a test system.
On such systems, when JavaScript errors occur, it is valuable to be able to identify where in the original source code these errors belong. It's not really useful to see "Error in bundle.js:1", because that really doesn't mean anything for you.
This is where source maps come in: They allow you to "map" packed code back to original source code. While this is a handy feature for your developers, it also makes the job of an attacker easier, but telling him exactly which JavaScript frameworks in which version you are using.

What does that mean for me? Should I be worried?
All in all, it's not a huge issue. It's similar to having verbose error messages enabled. It won't enable an attacker to suddenly take over your server, but you're helping an attacker, when you really don't need to.
If your vulnerability scanner reported this on an internal testing system, then feel free to ignore this vulnerability as a false positive. If your scanner reported this on a production system, consider removing the source map on the production system.
Answer: If your vulnerability scanner is telling you that the existence of a source map is a vulnerability, you should start shopping for a new scanner, one from a company that doesn't believe in security through obscurity. A well-written Web app stays secure even if the attacker has a copy of all of the source code. If you're required to fix all findings from this scanner for some dumb bureaucratic reason, then the "fix" is to delete the .map files, but keep in mind that this will significantly impede debuggability for zero real increase in security.
Comment: I disagree. You shouldn't rely on security through obscurity, but it can be a layer in the defences. There is no reason to have these files available in production and they make an attackers job considerably easier. If everyone else decides not to include them and you decide to include them then an attacker may choose to target you over the others because you're an easier target

What is a source maps vulnerability?


Noise Reduction for Video in Blender

Question: I have footage of noisy HD video (too dark) and wonder if Blender's noise reduction applies to video. There is also this Blender add on that is available for a nominal fee, but again, there is no indication that it works for video and the seller cannot be contacted. Can anyone advise on noise reduction for video in Blender? I have tried noise reduction in DaVinci Resolve and it works a treat, but hope the same can be done in Blender...or better. Just to be clear, because some are saying 'duplicate' this is for VIDEO not 3D. V I D E O.
Comment: In my opinion, to process video, stick to a video editing app. If resolve does a good enough job for you, then use it. blender is terrific for creating and animating in 3d, but it is light years away from the maturity of  dedicated video apps when it comes to video editing, compsiting or post-processing. If you are willing to spend some money into cleaning noise use [NeatVideo](https://www.neatvideo.com/) (not compatible with blender)
Comment: Blender is a bit of a struggle as an NLE, but I was surprised it can do what it does. There are times when it can be useful for intro/outro graphics. Perhaps for 'add-on' developers reading this, they may want to make something for video reduction noise. One of this issues I have with DaVinci Resolve is that when you use Lite (their free version) it disables one of your GPU's (my workstation has two) and I do not have cash for the paid version, yet. I don't think Blender would ever disable my GPU's. Today, maybe Blender sucks as an NLE, but maybe it won't tomorrow.
Answer: Cycles noise reduction introduced in recently released Blender 2.79 version works exclusively for rendered images because it specifically uses information from the 3D scene to make an educated approximation, as far as I know.
As such it would not work for random video files since no 3D information would be available in most situations
Everything else that uses the Compositor and/or Video Sequence Editor should be able to work as well for externally obtained footage, as long as it does not rely on data obtained from 3D rendering, like render passes, layers, or any other buffered data from a virtual model.
The mentioned addon seems to be used in the node editor as a node group based approach, so in theory it should work with any externally obtained footage.
Just use an Shift+A > Input > Image or Input > Movie clip to insert your video sequence and use the desired nodes as recommended.
Disclaimer: Whether the algorithms or processes used in those nodes will work correctly or satisfyingly in your particular footage or specific type of noise is unknown.
Those nodes were made specifically with Raytracer bound noise/fireflies in mind, that have particularly very high peaks, so it may not work well of the low intensity noise or your particular case.

Noise Reduction for Video in Blender


Should the answer be downvoted in case if it might rise to issues though it is a correct answer for this question and solves it

Question: An answer for a question solves what the user wanted, in particular.
However, in rare cases, user might get a problem. The answer might have a side effect, that too rarely. The answer might have left an exceptional case unanswered.
Or, a user finds that answer has an issue long time later it has been answered.
Should it be downvoted?
Comment: Why not suggest an edit, either fixing the problem or adding a warning?
Answer: You can downvote any answer for pretty much any reason you feel appropriate. There are no strict rules. This may be because it's simply incorrect, but may also be because it's technically correct but doesn't do a good job at explaining things. It may also be because you don't like the formatting, or if there are too many typos. It's really up to you to make the judgement.
I have often downvoted answers for exactly the reason you've described: the answer is technically correct, but is missing some information which may come back and seriously bite someone who follows the given advice. It's usually best if you also leave a comment explaining this so that the answer can be improved, but you're in no way obligated to do so.
The only thing that's not allowed is doing stuff like targeting a specific person with up/downvotes. You need to judge answers, not people.
Answer: I don't think people should necessarily down vote anything unless its explicitly wrong. I've noticed, mostly on other SE sites, that a lot of the tech world knows the answer but is horrible at explaining it. Even worse, we tend to have a lot of people who like to rebut answers with, "Well technically...". I don't know if it is smugness or lack of understanding their audience, but these types of responses tend to hurt learning. I know there have been many times where I'll put a lot of detail into an answer and on purpose not include something. Usually its an outlier case that will only confuse the person asking the question and isn't pertinent to their query. Then someone will swoop in, down vote and create a post poorly explaining the nuance case and make life much more difficult.
Is there a way to fix this? No. People will still act the way they act.


Increasing the Survival Rate of Multiple Births?

Question: Historically, multiple births (twins, triplets, etc.) are less likely to survive under circumstances of high infant mortality, what might change that so at least one tends to survive?
Comment: You are asking about chances in the body of your question and about how to increase them in the title. Choose one. There of course are many solutions. You should maybe give a broad direction you want to go in and if you want a solution that exclusively makes one sibling survive and not increase the total survival rate of any birth and so on
Comment: Switch the species. Cats and dogs and pigs have a much higher survival rate for multiple births.
Answer: There are two factors that tend to give multiple births higher mortality:

More stress on the mother, which, in low hygiene environment, directly translates in childbirth problems for both mother and children.
Tendency to have "early birth", which translates in newborn problems if an incubator is not available.

If you want to give multiple pregnancies a better chance to result in healthy children you can:

have the "normal" children be smaller with respect to mother (I mean: either have normal newborn well below 2kg or substantially enlarge mother belly).
introduce a mechanism where fetuses "fight" for space while in the womb, so that result will be some "very early" births (presumably miscarriages) and a final "normal birth" of the "winning" one.
introduce some post-partum device able to protect premature (e.g.: some kind of skin pouch as found in marsupials).
Comment: If you are willing to make the protagonists non-human, then there are plenty examples of animal species giving birth to multiple living babies and most of them surviving (under good conditions). This includes many domesticated animals (dogs, rabbits, pigs...) and hemerophiles (cats, rodents...). In fact the majority of mammals procreate that way. In this regard humans are an exception, not the rule.
Comment: Let's assume that they're either related to humans or rather close to them in physiology, what then?
Comment: @Preg-Fan: It's difficult to answer that. There are "good reasons" why things are as they are, so good Evolution was forced to find a way to ensure multiple birth is a rare exception. In order to revert this you *must* change something substantial (risking other problems). I stated what are (IMHO) the minimal requirements (each one of them would be enough). I can't know what You are inclined to accept, but be assured some non-trivial changes *will* be needed, otherwise Evolution would (most likely) have found a way to "harden" women.


Windows 10 USB only working if device plugged in during boot

Question: I got a PC with a ASUS B85M-G motherboard and the following problem. None of my USB ports (neither at the back, nor at the front, neither USB 3.0, nor USB 2.0) work. Actually, they don't work for devices plugged in to them after Windows has booted. A device that is already plugged in during boot (mouse, usb-stick, ...) is perfectly detected and usable. When I plug in a device at runtime and then reboot Windows, the device is available.
Sometimes (but not always), a Windows alert message saying "USB device not detected" or the like is shown. When that happens, there's also a unknown device called "USB-STICK" in the device manager.
My device manager's usb-section looks like this: https://anchr.io/#/image/OdjZd.png. The usb-related BIOS settings look like this: https://anchr.io/#/image/v0Q2g.jpg. In forums I found that my problem could have something to do with the xHCI mode, but neither disabling nor enabling it helps. Any ideas?
Comment: Have you found ousony t how to solve the issue? I have the same problem in Windows 10 with a Sony Vaio.
Answer: It looks like the xHCI driver is missing in your operating system. If you had a fresh OS install with xHCI disabled, it is likely that the driver setup skipped this controller.


Is it illegal to threaten harm to yourself?

Question: If Bob goes up to Alice with a knife and threatens to cut her, obviously that's illegal. But what if Bob points the knife at himself, and threatens to hurt/kill himself? Assuming he's subdued before he can hurt himself, can Bob face legal action? As a related follow-up, what if Bob asked XYZ of Alice, or else he would hurt/kill himself? Would that qualify as extortion, or something similar?
Answer: Bob can ultimately be detained to prevent self harm, while self-harm is not fully legal, it is not generally a crime, however if Bob is a member of one of the Fort Peck tribes, it constitutes "aggravated disorderly conduct" which is a crime. So it partially depends on what you mean by "illegal", and partly on who Bob is. This is irrespective of whether there is an Alice. Bob can also be detained if it is reasonable to believe that he is threatening Alice, and the description of the circumstances does not establish that it is unreasonable to believe that he threatened Alice.
Answer: canada
Under the Criminal Code, assault (including threats of force) requires the target to be "another person" (see s. 265). Bob does not commit the offence of assault by threatening to harm himself.
If Bob persuades or induces Alice to commit an offence and Alice follows through with it, then Bob is a party to that offence (s. 22).
If Bob persuades or induces Alice to commit an offence but Alice does not commit the offence, then Bob is guilty of the standalone offence of "counselling an offence that is not committed" (s. 464).


Can you use TWF with Eldritch Glaive?

Question: Just like the title says. The warlock invocation eldritch glaive lets the warlock attack with the glaive effect "as if wielding a reach  weapon." Is this sufficient to let a warlock use two-weapon fighting in conjunction with the eldritch glaive? (I know that if it's allowed, then the warlock'd probably have to use in his off-"hand" unarmed strikes or armor spikes.)
Comment: This question mentions both Eldritch Glaive and Eldritch Blade. Is this the same thing or is it a mistake?
Comment: @Sdjz So far as I'm aware, there isn't a warlock invocation named *eldritch blade*. (And, unlike spells, third-party folks couldn't write warlock invocations.) I've gone ahead and changed the question's mention of *eldritch blade* to the well-known and -documented *eldritch glaive.*
Answer: Typically no…
A warlock must take a unique full-round action to make attacks with an eldritch glaive (Dragon Magic 82). The invocation's description, in part, says, "As a full-round action, you can make a single melee touch attack as if wielding a reach weapon."
While the Player's Handbook on Two-weapon Fighting, in part, says, "If you wield a second weapon in your off hand, you can get one extra attack per round with that weapon" (160), earlier on Full Attack, in part, says, "If you get more than one attack per round… because you fight with two weapons…, you must use a full-round action to get your additional attacks" (143). (Bear in mind that the section is titled Full Attack; it's not like the run action—also a full-round action action—entitles a creature to make extra attacks because the creature's wielding two weapons; it's the full attack action specifically that allows a creature to make extra attacks because the creature's wielding two weapons.)
Thus the full-round action that eldritch glaive requires isn't just, like, code for a full attack during which the warlock can, for example, employ two-weapon fighting, but, instead, the full-round action that eldritch glave requires is its own special full-round action and, because of that, it's sometimes sadly incompatible with other combat options… like two-weapons fighting.
…But ask the DM
It's probably unlikely to create problems if a DM allows anyway eldritch glaive and two-weapon fighting. Two-weapon fighting is always resource intensive if it's to matter, so devoting feats, gp, ability score increases, and other resources to improving two-weapon-fighting-while-eldritch-glaiving likely won't raise any balance concerns: adding to his ability to two-weapon fight means subtracting from his ability to do cool warlock stuff… and, ultimately, that other cool warlock stuff probably would've been more optimal than two-weapon fighting.
The only potential wrinkle I can imagine to ruling that eldritch glaive can be used with two-weapon fighting is that folks might argue to extend that ruling throughout the game so that two-weapon fighting extra attacks can be made during any full-round action that involves an attack—like a full-round action Tome of Battle-style martial strike or maybe even a mundane charge!
That… really doesn't sound terrible, to be honest, but such a change may be a concern for the DM if the DM is worried about radically altering the game.
Comment: The only concern I have with applying the two-weapon fighting combat option to the charge combat option is that if you have the Improved Two-Weapon Fighting feat, you get two attacks with your offhand weapon (while during a charge you only get one with your main weapon), which just seems narratively "off." So Improved Two-Weapon Fighting and Greater Two-Weapon Fighting might, in this hypothetical, need some minor tweaks to wording to say they only apply in situations where you actually get that many main weapon attacks.
Comment: @KRyan O, yeah, in any campaign wherein the DM allows two-weapon fighting to work in conjunction with *any* full-round action that includes one or more attacks, there will be weirdness! However, the situation that comment describes is *so far* from the question that I hesitate to address it in the answer. Seriously, do you think mentioning further issues that may arise with a hypothetical house rule is necessary, or are we just speculating?
Comment: No, probably not necessary, it's just something that has caused me some troubles in the past—you can actually cause this situation in official Pathfinder, by taking Improved Two-Weapon Fighting with the warpriest's 6th-level bonus feat: they get to select that as if they had full BAB, but they _don't_, so their full-attack at that point become main hand, off-hand, off-hand, which is weird. It's come up for me a few times with my third-party work, too.

Can you use TWF with Eldritch Glaive?


What is the maximum level?

Question: What is the maximum level in the game and how many skill points will I have at maximum level?
Answer:
This answer is outdated as of the 2019 Commander Lilith DLC, as noted in this answer

The max level in the Borderlands 2 base game is 50, giving you 45 skill points to spend. Gearbox actually has a character planner on their website (which can be found here) that should help you pick out your skills.
Borderlands 2's "Ultimate Vault Hunter Upgrade Pack", available for $5 (or as part of the Season Pass DLC) can be purchased to increase the level cap from 50 to 61.
The Ultimate Vault Hunter Upgrade Pack 2: Digistruct Peak Challenge DLC further pushes the level cap to 72 for those who own it.
Comment: @WernerCD I didn't count the point at level 5 because that's the one you need to spend on your action skill to unlock your skill trees in the first place. Technically speaking though, you do get 46 skill points.
Comment: @DiabloMonkey The level cap with UVHPack is sixty **one**. Can you please link to something proving it is 65?
Comment: Looking at the [char editor](http://www.borderlands2.com/us/skilltree/commando.html), you have 46 points to spend. You forgot the point at level 5?
Answer: As of the release of the Commander Lilith & the Fight for Sanctuary DLC on 2019-06-09, the level cap has been increased to 80.

What is the maximum level?


Unable to complete Cyanogenmod 14 setup

Question: Hei, I Just installed CM14 on my Nexus 6p + Gapps.
All clean, fresh unlocked etc.
Cyanogen boots up to setup-wizard the device, select the language etc.
But after the wifi selection the "tranfer data from another device" opens up and I can not cancel it / proceed it.
Can someone help me with this ?
Comment: I changed 3 times the language and got back of the screen .
Then an crash report came up and I langed on the "complete setup" screen.
Answer: As of now the Setup Wizard is known to be broken across multiple devices on CM14.x.
The solution for now seems to be removing <code>/system/priv-app/CyanogenSetupWizard</code> from your recovery. But the trick is that you shouldn't just delete it; instead, move the folder elsewhere for backup, then boot up into the OS properly. You will notice things like the notification bar and recent keys working weird. Don't worry - boot into recovery again and place that folder back to where it was, and set correct permissions (rwxr-xr-x for folder, rw-r--r-- for file). Reboot and you should see the Setup Wizard briefly come up but goes away if you interact with it. That's it - now start using the phone as you would normally.

Unable to complete Cyanogenmod 14 setup


Accessing Master Page property

Question: I'm setting a session variable in the master page in the Page_Init event.  I then have a property on the master page that allows me to access that value.
Code on master page:
<code> public Eco.Business.User User
{
    get { return (Eco.Business.User)Session["user"];}
    set { _user = value; }
}
</code>
I then do this in the page load event of a page that uses the master page (class for the master page is SiteMaster).
<code> SiteMaster m = new SiteMaster();
    Eco.Business.User _user = new Eco.Business.User();
    _user = m.User;
</code>
Can figure out why the property in the master page is not being set. It is always null.  But the session Session["user"] has something. I know this because I saw it in the debugger. Any ideas?
Thank you
Answer: If I understand what you're trying to accomplish, I think you will want to set the object in the Session in the property definition as well:
<code>public Eco.Business.User User
{
    get { return (Eco.Business.User)Session["user"];}
    set { Session["user"] = value; }
}
</code>

Accessing Master Page property


A prime number problem.

Question: If $n$ is a positive integer and $(p_1,p_2,p_3,p_4,\ldots, p_n)$ are distinct positive primes, show that the integer $(p_1\cdot p_2\cdot p_3\cdot p_4\cdots p_n)+1$ is divisible by none of these primes. How do I figure out that none of the primes divide that new integer?
Comment: You don't need induction. $d$ cannot divide $kd+1$?
Comment: You don't even need them to be primes. It suffices to have $p_i\ge2$.
Comment: Start with a simple case. Does $p_1$ divide $p_1p_2$? Does $p_1$ divide $p_1p_2 + 1$?
Comment: No it can't. I know it can't be possible, but to prove it, do I do induction?
Comment: Oh, that's what I was after. Thanks.
Answer: Suppose $7$ is one of the primes, so $p_1\cdots p_n$ is a multiple of $7$.
The next multiple of $7$ after $p_1\cdots p_n$ is $(p_1\cdots p_n)+7$.  So $(p_1\cdots p_n)+1$ is not a multiple of $7$.
More formally, suppose $7$ divides $(p_1\cdots p_n)+1$.  Then for some integers $j$, $k$,
$$
\begin{align}
(p_1 \cdots p_n) & = 7j \tag 1 \\
(p_1 \cdots p_n) + 1 & = 7k \tag 2 \\[10pt]
\text{Then subtracting $(1)$ from $(2)$, we get: } 1 & = 7k - 7j = 7(k-j) \\
\end{align}
$$
So $1 = 7(k-j)$.
Comment: But how exactly do I show that as a proof?
Comment: Do you have the theorem sometimes called the "division algorithm", stating that for $m,n\in\mathbb N$, there exists a quotient $q$ and a remainder $r\in\{0,1,2,\ldots,n-1\}$ such that $m = qn+r$? $\qquad$
Comment: Yes, I've learned that algorithm.
Comment: I've expanded the answer somewhat. $\qquad$
Answer: We will need the following theorem:
Theorem. For any two natural numbers $x, y$ ($ y \geq 1 $), there are unique natural numbers $q, r$ where $ 0 \leq r < y $ such that $x = qy + r $.
Proof. If $ x < y $ then we must have $ q = 0 $ and $ r = x $, so in this case the $q, r$ exist and are unique. Assume that there is a natural number $ x \geq y $ such that no such $q, r$ exist, then without loss of generality we may assume that $ x $ is the smallest such number. However, then $x - y$ cannot be written in the desired form either, as if we had $x - y = qy + r $ then this would imply $x = (q+1)y + r$. This contradicts the minimality of $ x $, as $ x - y $ is a smaller natural number with the same property. Therefore, such $q, r$ must exist for all values of $x$.
To prove uniqueness, assume that we had $x = q_1 y + r_1 = q_2 y + r_2$ and $r_1 > r_2$, then $r_1 - r_2 = y(q_2 - q_1)$. On the other hand, $r_1 - r_2 \leq r_1 < y$, so that we have $y(q_2 - q_1) < y$ and therefore $q_1 = q_2$. QED.
Corollary. $x = qn + 1$ ($q, n \in \mathbb{N}$) is not divisible by $ q $ for any $q \geq 2$.
Proof. If it were, we would have $x = qm$ for some $ m $ and $x = qn + 1$ simultaneously, contradicting the uniqueness proved in the above theorem.
The statement in the question follows immediately from the corollary.
Comment: The division algorithm (Theorem) is not needed. Simpler: if $\, qm = qn+1\,$ then $\,q(m-n) = 1,\,$ contra $\, q> 1$.
Comment: That is simpler, although I see no harm in using the division algorithm either way.
Comment: The simpler method is much more general: it works in any ring for any nonunit $q$, i.e. any $q$ that does not divide $1$. But most rings don't have a division algorithm. That said, it is, of course, always helpful to have multiple proofs. Here one gains a bit different insight by using the *uniqueness* of remainders in the division algorithm - as you do. I've written about the *power* of uniqueness theorems in many of my posts, e.g. [see here.](http://math.stackexchange.com/search?q=user%3A242+powerful+uniqueness)

A prime number problem.


Do I have to mod my xbox 360 console to play region free games?

Question: Do I have to mod my xbox 360 console to play region free games?
I bought my Xbox 360 in Japan so I would like to know if i have to mod my console to play region free games as I live in south africa...
Answer: By definition, a region-free game will play on any console regardless of its region. Modding your console is only useful to play region-locked games on a console not from the correct region.
Answer: Region-free by definition means that the game is not locked to a certain country or region, see what I did there?
Example. Say I make a game and I develop it in Japan. I want it only to be sold and played in Japan. I would "region-lock" it. So if someone decided to order my game in America. It couldn't be played. IF
I think you're asking if you need to mod your console to play region-locked consoles and that answer is technically yes.


Is it ok to ask professor to read my published article?

Question: I have applied for a position last month and the deadline is on March. But by this time one of my work has been published in a good journal (which I wrote in my CV as under review). The position is competitive. Is it ok if I mail the professor and ask him to read my published work? (Though the published work is not so much similar to his work). Will it add extra value to my application? (I have talked with the professor regarding his work and admission several times through email)
Answer: I think it is fine to send the article, but not even necessary to ask him/her to read it. It is enough just to make it available, with a note about where it is published. It will be read or not, whether you ask or not. It is also good whether it is closely related to the professors area of research or not.
But making it available easily is a good thing to do and should enhance the application. It shows something about your ability, even if the sub-field is different and even if it isn't read.
Answer: MAR is the deadline for applying or for the decision?  (Action to take is similar with perhaps a minor different flavor.)
A.  If for the application, just send an updated CV and a short note why (the paper accepted).
B.  If for the decision, than send an email letting them know the paper was accepted and that you are still interested in the position. Short and sweet email.  More of just a touch point since you have an excuse to do so.
P.s.  In either case, do NOT bother attaching the paper--you didn't attach the in review papers, why attach the in press ones?


How can I change the "Delete?" label in a Djano Inline

Question: I'd like to replace the default "Delete?" label in TabularInLine to be something like "X". Is there a way to do this in Django directly or do I have to change it after the page loads with JS?
example image
Answer: You would need to provide your own version of the Django Admin template that generates that page. To do this you would save a template with the same name and the same parent directory path within your project's template directory (see further documentation and recommendations here https://docs.djangoproject.com/en/dev/ref/contrib/admin/#overriding-admin-templates). Based on the simple nature of the desired change it would be advisable to only modify that section of the template using this method https://docs.djangoproject.com/en/dev/ref/contrib/admin/#overriding-vs-replacing-an-admin-template.


Apple Battery Charger - does not charge to 100%?

Question: I have recently purchased the Apple Battery Charger and immediately charged the batteries that came with it. A few days later (3 or 4) I placed the batteries into my mouse and noticed that they only indicate about 75% full. Is this correct? Is the value being read wrong (they are actually 100% full) or do they not fully charge?
Comment: The reviews on the apple site seem to mirror my experience: http://store.apple.com/au/reviews/MC500X/A
Answer: It's hard to tell with this new product, that is really a normal battery charger. Rechargeable batteries should charge all the way to 100% especially when they are new. If you're not getting a full charge, try depleting them all and fully charge them, see if that works. Otherwise, batteries may be defective or it could be a mouse/software misinterpretation.


Asterisk test ISDN card

Question: I have an AVM ISDN controller C4 plugged into an asterisk machine.
It shows up in the PCI device list as:
Digital Equipment Corporation StrongARM DC21285 (rev 04)
How can I test this card to see its working from Asterisk, if possible without plugging actual phones into it?
Anybody knows a command for it inside Asterisk's CLI?
Answer: You can use dahdi-tool for this.

Asterisk test ISDN card


Urine on clothes

Question: As Salam alaikum. Unfortunately, I suffer from prostatitis. And sometimes there are feelings as if urine has dripped, sometimes it happens that it's just an instigation, and it happens that it has dripped. And when I was in the toilet today, I was washing myself and this feeling happened. It was like urine dripped, but I do not know if it really dripped, and if it dripped, where exactly on clothes. Absolutely no idea. What to do?
Answer: You are suffering from Waswas and you should not give much attention to any of the thoughts like "feelings as if urine has dripped" unless you see a concrete evidence.
The prophet told someone who was suspecting his Wudu during the prayer: "Do not stop praying unless you notice a smell or hear a sound", i.e. if you suspect your wudu for some feeling, you ignore it and persist on praying unless you notice something evident.
Comment: to add to what you said, we have to understand that Allah is Afwun (Pardoning), so we just try to avoid urine, finally if some drops of urine happened to be there, he may pardon us.

Urine on clothes


How can I "automatically" get a reminder that day is done?

Question: I many times forget time and stay long hours in the office.
Is there any kind of app that would automatically set a reminder when computer starts + X hours passed?
Now I try to set a reminder (native app) but many times I forget, and it is a bit tedious.
I was wondering if there is somekind of automated way to get some kind of reminder that the day is done?
Has anyone had a similar issue and solved it with some other approach?
Answer: Go to the built-in Clock app and add an alarm for the time you want to go home or log off your computer. Select repeat and choose the weekdays that you want it to go off. You can choose a ringtone or song (We Gotta Get Out Of This Place) instead of one of the standard tones if you want.
The Timer tab in the Clock app can sound an alarm after 8 hours if that's what you want instead.
Comment: I'll try your suggestion. Basically I was interested in something that does it without me needing to actually set anything. In Windows for example I know that the Computer first start is part of the Events in adminstrator logs and I think it is possible to configure some event on start up. So I was wondering if some kind of event would cause some app (perhaps the clock app that you say) to add to the current time e.g. 8 hours to ring without needing to set it every day manually. Do I make sense I what I describe?
Comment: Where is this timer tab?
Comment: On the bottom of the screen: World Clock - Alarm - Stopwatch -Timer.
Comment: I am sorry but I can't find this build-in Clock app. Is it when I open "Date & Time preferences" when I click on the current time?
Answer: You have some great productivity soft like that :

THE ULTIMATE TIMER. IT'S INSANELY SIMPLE. Toggl's time tracker is
  built for speed and ease of use. Time keeping with Toggl is so simple
  that you'll actually use it. Toggl drives a stake in the heart of
  timesheets.

https://toggl.com

Find your ideal work‑life balance. With so many distractions and
  possibilities in your digital life, it's easy to get scattered.
RescueTime helps you understand your daily habits so you can focus and
  be more productive.

https://www.rescuetime.com

Start putting your time to good use with My Minutes. Wasting too much
  time browsing the web? Put a cap on your web surfing by setting a goal
  of "at most 45 minutes".

https://itunes.apple.com/us/app/my-minutes-simple-personal/id553366149?mt=8
An exhaustive list here :
http://www.fastcompany.com/3024249/10-time-tracking-apps-that-will-make-you-more-productive-in-2014
Comment: Why is rescue time not in the app store? Is it safe to download and install such way?
Comment: Basically your suggestion is to do time tracking instead I understand
Comment: In my point of view it's safe.. But the tracking is more intrusive... My suggestion was to test a tracking soft and put an alert 'work time done' but i don't really know if it's possible.


How to make a logo resize properly in a responsive theme

Question: I am creating my first responsive website http://islamabadpools.com; I have used the Omega theme as a starter theme, and it works almost perfectly for the layout.
I used the absolute image module for adaptive images but it's not working for views banner slideshow.
I am also unable to make the logo responsive so I removed the logo from theme options.
I created a new article content, and added a logo as an image and given it a title logo; then, I created a view block with an article image field and filtered that with the title "logo"
and in field properties; in the view, I selected adaptive as the format.
Now my logo is responsive/adaptive but it's getting very small on lower screen sizes.
I repeated this for the quick assistance block displaying in the right corner of the header.
I just want to know what the right way to make the logo responsive is.
Answer: Add the following css to your site:
<code>.view-logo img {
  max-width: 100%;
  height: auto;
}
</code>


Why do we get the privilege to upvote or downvote at different reputation levels?

Question: To upvote we need a reputation of 15, but being able to downvote requires a reputation of 125.
Why do we need more reputation to downvote?
Comment: Because downvotes are serious business and they should not be thrown around like toys.
Comment: @Mystical I don't even throw toys around like toys... wait a minute...
Comment: @Mysticial - for the last time, stop throwing the downvotes around in the living room and go outside!  You'll break a lamp in here.
Comment: And look at all these people hurling downvotes at this question like toys.
Comment: I think you should be allowed to downvote an answer after you've had one of your own accepted. Same goes for a question. If someone can't write an acceptable question, why should we consider their vote on others?
Comment: @Mysticial Upvotes are serious business as well. I never throw them around like toys.
Comment: We'll need only 100 rep to downvote on this site.
Answer: Voting a question or answer up is an act of pure goodwill. The only reason to do it is because you think it's a good and useful question. If you vote up junk that doesn't deserve it, so be it. A newcomer may not really know what deserves voting up, but they will probably not give upvotes to spam, or answers that say "I have this problem someone help me".
Downvotes are given for two reasons. The good reason is that this is a poor question or answer, and people shouldn't be fooled by it. Making the internet better. The bad reason is "I want to make my answer [or my friend's answer] look better and show up first". By asking you to earn some rep, the site is asking for some commitment to making the internet better. The hope is to weed out those who would downvote for the wrong reasons, or convert them to a sharing way of thinking.
125 rep is probably not quite enough to achieve that, but it's something.
Comment: I don't know...upvoting harmful or very low quality content can be quite harmful, saying "so be it" doesn't sound right to me.
Comment: @FrédéricHamidi And yet it takes 5 downvotes to compensate for the rep of even a single upvote.  People can go around posting crap getting on average of 2-3 downvotes per answer, but if they get an average of one pity upvote per answer they're coming out ahead on rep, thus encouraging them to continue this behavior and stop posting low quality content.
Comment: @Servy, indeed, on the reputation side the post author ends up a winner. I confess I usually do not consider up/downvoting in terms of raw score, possibly because I'm pretty confident users who repeatedly post "bad" questions and answers cannot possibly reach dangerous (3k+) amounts of reputation even if some of their posts are mistakenly upvoted. That's only a hunch, of course, and I do not have data either confirming or infirming it.
Comment: Let me throw some toys around ... Nope, +1 because this is serious business.
Comment: @Servy, I don't know if it can really be considered as harmful... If the quality of the upvoted post is very low, in my experience it only results in someone commenting `Who the  upvoted this?` and the post getting a few compensating downvotes in the process.
Comment: @Servy: I think there is the auto ban? Isn't it based on score rather than rep?
Comment: @nhahtdh People tend to hit the question ban much more often than an answer ban.  Deleted content also contributes quite a lot, but if they're getting a pity upvote or two they're discouraged from deleting rather than encouraged to delete.  While that may kick in depending on the specifics, the fundamental idea is that upvotes on wrong or low quality content encourages more of such content, and that's bad, very bad.  Personally I'd say it's even worse than downvotes on valuable content.
Comment: @Servy: I'd say the fact that people hit question ban often is because downvote on question does not cost reputation, so they are thrown around more liberally compared to answer downvote. And I don't know whether people don't delete answer is because they don't know how to, or they just want to preserve the rep gained.
Answer: To discourage things like downvoting answers that compete with you or your friends, a downvote comes at a cost of -2 rep.  The cost has to be meaningful.
If you could downvote at 15 reputation, you could create a "troll" user. The troll would gain 3 upvotes  and could then downvote 8 times.
The requirement of 125 makes it harder to create troll accounts.  Few trolls are willing to invest this effort.  And those few that make it through can be investigated by moderators.  It's way easier to show a pattern of abuse with 13 votes as proof.
Answer: Given that downvoting answers detracts reputation from the recipient, it is not something you want to give to a one-time question asker that happened to get a few upvotes but hasn't really gotten the hang of how SO works.  Also, at such a low level of reputation, you could quickly cause yourself to lose enough reputation to lose privileges, causing some confusion among the newly initiated.
There is a deeper answer to this, I'm sure, but I think these facts played a part in the decision.
Comment: note: downvoting *questions* is free :)
Comment: @hayden This is funny because until they posted up above, I didn't know that!


Can a tor exit node know the ip of .onion sites?

Question: I am just wondering about this since I heard that tor exit nodes know the ip of the website the user is visiting
Answer: No, a Tor exit node does not know the IP of a .onion site. The only node that knows the real IP of a .onion site is a special node called guard node. It's the first node the hidden service connects to, so it knows the real IP.
Answer: You already have an accepted answer, but I'm going to add a clarification anyway.
When connecting with a hidden service (.onion), there is no exit node at all! Exit nodes are gateways to the normal (non Tor) Internet. Hidden services (.onion) don't exit, therefore no exit node.
Guard nodes are entries (although all nodes are bidirectional) to Tor. So yes the guard node knows the real IP of the connecting computer but it knows nothing about .onion hidden services. The guard node cannot identify and locate .onion hidden services.


Translating Objects in Worldspace

Question: Given the worldspace coordinates of a collection of arbitrarily positioned objects, how do I translate them while preserving their relative placement? For instance, I have a table and a few bowls that are placed on top of it at (x1, y1, z1) and wish to moved them to (x2, y2, z2).
Answer: One popular method is to use parent-children hierarchies to store matrix transformations in relative space. If you are moving the table and everything along with it, the bowls are the children of the table as far as their location is concerned. This can be done as simply as storing and pushing matrices in an array, and multiplying them. This could also be a simple use of a scene graph (note that scene graphs are not strictly defined as a spatial hierarchy though, as they can be used for many purposes).
PushMatrix() and PopMatrix() are examples in OpenGL for stack local transformations. However, these operations are expensive if you frequently look up their world position this way. It's a better to store an extra matrix for each object for its absolute position in space. You access this matrix when the object in question is not being moved at the moment, to save performance. Multiplication of local matrices then would happen only when the object is moved, and then its world (absolute location) matrix will be updated.
Answer: This problem is called Inverse Kinematics. In Inverse Kinematics, you begin with some "desired" translation and rotation for the endpoint in a kinematic chain. The goal is to determine where all the other objects in the kinematic chain are (their rotations and translations), and joint angles (if you have any joints).
In your case, you are putting in the rotation/translation of the final object in the chain (the bowl), and asking for the required rotation/translation of the first object in the chain (the table). Unfortunately, there is no general solution to your problem, since there are an infinite number of ways to place the bowl at (x2, y2, z2) while preserving the relative transform between the bowl and the table. (because you can rotate the objects arbitrarily and preserve the local transformation).
However, all you need to do to get a single solution is to invert the transformation between the table and the bowls. For this, I am going to assume you already know about transformation matrices.
Call the relative transform matrix between the table and the bowls H_tablebowl. Call the transform from the world to the table H_table. The global transform H_bowl = H_table * H_tablebowl. Now, what you're asking is, suppose we fix H_bowl to some value H_desired. How then do we find the resulting H_table? We know:
H_desired = H_table * H_tablebowl

And therefore
H_table = H_desired * inverse(H_tablebowl)

If you have just the translation of the bowl, then you can arbitrarily fix the orientation to some value (like the identity). Then the solution simply becomes:
translation_table = translation_bowl_desired - translation_table_bowl

Translating Objects in Worldspace


How to deserialize xml created by to_xml() in google appengine

Question: In Google App Engine, I can serialize an object by calling its to_xml() method.
There doesnt appear to be an equivalent from_xml() method to deserialize the xml.
Is there an efficient way to deserialize back to an object?
Answer: Just to clarify, I'm going to assume that you're asking about the Model.to_xml() method, and that by efficient you mean a single method which you can call which will provide you with a model object.
As you noted, there is no such method on the Model class for the datastore API. I think the intention is that the purpose of the to XML method is to make the model easily exportable to another application, such as a javascript client or for importing into another database or storage mechanism, similar to using the remote API.
It should be possible to create a function or static method of a specific Model class which would generate a new model of a particular type from parsed XML. You will then most likely want to perform a get_or_insert() to write the resulting object.
If you're looking for a native Python to Python serialization method, you could consider pickle.


Setting up a fresh web developer environment OS X or Unix?

Question: I am doing a clean install of OS X Snow Leopard and I was wondering what people think should go into the ideal web developer environment?
Can I get a good rundown of things you would do when setting up a clean system?
My main focus is HTML, CSS, PHP, and Actionscript work. But I would also like to dabble in other languages and frameworks as well (including Ruby and Python, Rails and Django).
The main goals

Cleanly and rationally organized
Efficient to add new frameworks, project source code and packages
Easy to disable components, frameworks and parts of the environment
Ability to host multiple projects simultaneous without too many conflicts or dependencies
Effective source control over all projects and environment configurations
Somewhat idiot proof for a non system administrator, but sufficient power to customize
Easy to isolate and debug environment configurations.

I am aware of MAMP and XAMPP. And I use Git.
I was thinking about using macports for setting up various tools and packages. I also want to cleanly manage frameworks. But I also want to be able to experiment with unknown frameworks without fear of cluttering or breaking my normal day to day working environment.
I know the command line but I am by no means a system administrator. With all that said what would you recommend for managing the hosting environment? Apart from VM are their tools for conveniently sandboxing configurations (different versions of frameworks, databases, webservers, etc) and linking these to a particular client's project code?
It seems like macports by putting everything in /opt is the way to go. I don't have to worry about mucking up the system binaries. And if I make a mistake or want to start over I can blow away /opt anytime I want to.
Are there tools to manage changes to your local web environment? For example if I install a particular package can I conveniently see "what has changed". Basically a way to do a diff on part of or even the whole system to know what implications are in place as I add new a new framework or update a package like PHP, Ruby, Perl, MySQL, Apache, etc. What about snapshots and backups of the configuration? can I version control this? If I setup PHP and Apache in a specific way to work with a specific clients hosting environment needs can I undo that configuration to quickly switch over to a different project?
Feel free to mention or link other related questions or answers if this question has any overlap. And I am not sure if this question should go on serverfault or superuser. But I am mostly interested to hear what other web developers have to offer.
Also, in particular I am curious to learn from people's mistakes. The main gist is, if you were starting over what would you do differently? Knowing what you know now?
Answer: For snapshotting entire setups including servers VM's would be the way to go. In Linux I often use chroots to isolate an install, but then the Apache ports etc are still shared.


I can't uncheck "Manage Windows Without Launcher"

Question: Please help, I can't uncheck "Manage Windows Without Launcher" of the docky.
Answer: Docky can have multiple docks, on the side, top or bottom of the screen, but it requires at least one of those docks to manage those windows that don't have a launcher on any dock. So you will have to select the dock you want to "Manage Windows Without Launcher" and check the box. Then when you select the dock that previously "Managed Windows Without Launcher" it will be unchecked.
Comment: its a shame, why would i want docky to manage the opened windows when i have panel. Going for cairo dock. thanks for the reply anyways.
Answer: I was looking for this because I thought it was a bug.
This 'feature' + the 'no separator' politics answer I was given previously makes me wander if you want people to actually USE Docky or are you trying to send them all towards Cairo-dock??
Answer: + 1 for not wanting this behavior, otherwise Docky would have been perfect for me.
if you feel like me, go to bug Bug #597755 on launchpad and let the developers know you care by telling them this 'bug' also affects you or leaving a comment.


Thesis corrections didn't save

Question: I have been a bit "haunted" by something that happened to me in graduate school. After submitting my MA thesis my advisor and the second reader corrected lots of typographical errors. I incorporated my advisor's corrections with no problem. However, there was a big problem when I tried to incorporate the second reader's corrections. I did the corrections and pushed the save button on my computer. However, unbeknownst to me the corrections did not save for reasons that I have never understood. Some days later my advisor called me into his office and mentioned that he had found lots of errors in the thesis. He checked the copy of the thesis that he had given me for correction and found that those corrections had, indeed, been made. Then he wondered out loud why the second reader hadn't "caught" the mistakes. But he never asked for the second reader's copy of the thesis. I went home checked the second reader's copy of the thesis and saw, to my horror, that the corrections had not saved. I stayed quiet and nothing came of this. I got my degree, but I have always wondered what could have happened if my advisor had discovered that the second reader's corrections had not been incorporated into my thesis. Under these circumstances could the thesis have been rejected?
Comment: I can't imagine rejecting a thesis because of unsaved corrections. The appropriate "penalty" would be that you have to make those corrections again and make sure they get saved (which I hope you did anyway).
Comment: Thanks for responding.
Answer: It's done. You got your degree, and nobody got bent out of shape over the issue. It is time to move on and use your emotional and intellectual energy on things that can shape your future, rather than dwelling on the past!
Comment: A valid answer solves the actual problem of the asker although unbeknownst to him/her. It did. Thumbs up!
Comment: This doesn't answer the question, rather it says "you shouldn't have asked it". In my view this is rather the job of a comment than of an answer, if anything.
Answer: I suggest making a corrected copy of your thesis publicly available, e.g. on your own webpage.  You can mention that your copy corrects certain typographical errors in the original thesis. That way any interested reader can find their way to the best version of your thesis.
Errors creeping in through some kind of version control failure are extremely common. When we notice this, we correct it -- what else can we do?  Also errors in theses are extremely common.  Good for you that the errors you are talking about are typographical.  I am a mathematician, and not long after I graduated I learned that one of the main results in my thesis is just false.  (I mention this on my webpage and instruct people not to cite results of my thesis directly but rather use published sources.)  Over the years a few other real errors were
pointed out to me. Nevertheless I have had a successful academic career for the last 20 years. The parts of my thesis that got published were only published after much more thought and work on my part; they don't include any of the errors I or anyone else has ever found in my thesis.  I think my story is pretty typical.
Once you fix what can be conveniently fixed, I really hope you can move on.  I can virtually guarantee that no one else is still thinking about the typos in your master's thesis.
Comment: Thank you so much for these thoughtful and sensitive remarks. I am most grateful.

Thesis corrections didn't save