Does adding more engines to commercial aircraft increase safety?

Question: For example, the Boeing 747 has four engines, whereas the Boeing 737 has 2. Does this means that the Boeing 747 would be safer if one of the engines fail?
Comment: i recommend reading up on [ETOPS](http://en.wikipedia.org/wiki/ETOPS).
Comment: No.  the 737 is perfectly safe on one engine.  It needs to demonstrate this during certification.
Comment: I narrowed down the question to commercial aircraft since it was broad and I think that is what you were interested in. Single vs. Twin engines on GA aircraft is a whole different discussion and question IMHO....
Comment: B-52 was built in early age of jets where 8 engines were needed. there was a proposal to re-equip the plane with 4 engines but turned down due to TCO. Compare thrust of B-52 at 17,000 lbs each vs 70,000 lbs each on A380. Imagine 1 engine of 380 equal FIVE of those on B-52!! It is more about technology in the end.
Comment: @AbhinavAgarwal You could (thrust wise) replace the four CF6 engines on the Boeing 747-400 engines with two GE90-115Bs as used on the Boeing 777-300ER. Anything above four engines I believe is more a technology limitation and thrust requirement compromise than a safety requirement.

If I screwed up the question feel free to reformat the question back or change it as you want :)
Comment: The number of accidents due to engine failure on transport aircraft is so small that any statistical analysis would have low confidence
Comment: Not really, I wanted to ask why some planes like the B-52 contain 8 engines, while the mammoth A380 is okay with 4 as well.. So, you can have enough power with fewer engines as well, then why are more engines added?
Answer: In the modern day and age, it is very difficult to put a numerical value to this type of question, simply because the chance of something happening is so incredibly remote. This is not a clear-cut equation and is dependant on several factors.
A few thoughts:
The impact of loosing one engine will be less significant on a four-engined aircraft than a two-engined aircraft. You only loose 25% of thrust as compared to 50%. However, two engined jets are built with greater safety margin and are able to handle an engine failure at any phase in the flight. Four engined jets are certified to be able to fly on two engines on one side of the wing.
In theory, you are twice as likely to suffer an engine failure with four engines, since you have twice as many engines. While the lost thrust would be less significant, very rarely damage can propagate to cause damage to other parts (See QF32 and ELY1862). In general, it is easier, cheaper and faster to maintain two engines than four. Should a complete engine swap be necessary for instance, you only need to do it twice instead of four times. Every extra step is an step where something could theoretically could go wrong.
The GE90 (Boeing 777) is certified to handle 'large' birds (4kg) as compared to the CFM56 (Airbus A340) only being able to handle 'medium' birds. Hence, the Boeing 777 engines are likely to be a bit more robust.
From a human perspective, pilot workload will be lower with two engines rather than four. Should something happen in a time-critical emergency, there will be more systems you need to keep an overview of. See CAL006.
Furthermore, not every engine-related incident is spared simply cause you have four engines. BA Flight 9 lost all four engines due to volcanic ash. On BA Flight 38, the engines failed in unison due to ice in the heat exchanger on the engines that were operating in identical conditions.
Despite ETOPS being around for several decades and applying to thousands of aircraft I have not heard about a single accident involving commercial jets operating in that domain.
Comment: That is what we call a perfect answer!
Comment: 'able to handle an engine failure at any phase in the flight'.. what about duel engine failure at 1000ft after takeoff?
Answer: From a strictly "engine cut out" point of view in todays day and age you are not getting your self very much. There is a great article here that talks quite a bit about this point from a GA stand point. There is of course the simple fact that for some planes you need more thrust to simply fly. There has also been lots of research done on if servicing an engine frequently makes it safer or actually adds to the problem. Again from a GA (mainly piston) standpoint there is a case to be made.
Comment: I edited the question to narrow it down to what I thought was the OP's interests. Perhaps you would consider making a new question specifically for GA aircraft and posting this answer there instead? :)
Answer: The more engines you have, the better off you are if one engine fails; however, the more likely it is that one will fail.
Engines, like many things, are rated in terms of "mean time between failures" or MTBF. For aircraft engines, MTBF is relatively high (tens of thousands of hours when properly maintained), but they do still fail in relatively unassuming situations.
It's simple probability that, given a nonzero chance for a given engine to fail, the chance that at least one engine will fail is the combined chance for each particular engine to fail. So if the engine type used on a 747 has a 1/1000 chance to fail on a particular flight (the actual chance is much lower, in the tens of millionths), there is a 4/1000 = 1/250 chance of at least one engine on the plane failing during that flight. If the two engines on a 737 each had the same chance for failure, the chance of one engine failing on the flight are half those of one engine failing on the 747, because there are half the number of engines that could fail. In MTBF terms, we can say the mean time between single engine failures on a 747 is half that of a 737.
So, we see that increasing the number of engines, all other things being equal, actually increases the chances of something going wrong. However, the pilot of a twin-engined craft, though he may be twice as likely to experience an engine failure compared to the pilot of a single-engine craft, is going to have a much better day when it happens than the single engine pilot will.
The big question that really has to be asked is, how many engines can the plane fly on, and how many more than that number does it have? Jets like the DC-10 and 727 were marketed for their relatively high fault-tolerance; they could maintain level flight at low altitude on only one engine, having lost the other two, and on the 727 it didn't really matter which one was still running as they were all so close to the centerline. The 747 requires at least two of its four engines to maintain level flight (see British Airways Flight 9 in 1982, during which all four engines quit mid-flight due to ingestion of volcanic ash; restarting one engine slowed the rate of descent but it took two to level off).
Now, primarily for fuel efficiency reasons, passenger jets are designed with as few engines as they need; engines are most efficient at a specific point in their power curve, and you design the aircraft to cruise efficiently at that power output of its engines. This is why the 737 (and newer jets like the 777 and 787) doesn't have four engines; it doesn't need them, because the 737 is a fifth the weight and the engines it does have are more efficient than the 747's.
Answer: If an engine fails, the fraction of loss of thrust is smaller for an aircraft with four engines than for one with two. If other things happen, for example loss of rudder, yaw control is easier with three remaining engines than with one.
So in terms of %-loss of thrust and what this entails, a 4-engine plane is safer than a 2-engine plane.
Answer: ICAO regulations allow two-engine aircrafts to fly over oceanic routes (they must have a Ram Air Turbine - RAT) so such a plane - certified as ETOPS, Extended-range Twin-engine Operational Performance Standard - must be safe. Anyway I can agree with other answers stating that if you have to loose an engine it is better to have 3 other.


(Hardware) Machine will not boot - strange situation

Question: We have a LGA1366 build (about two years old) that would suddenly not turn on about six weeks ago. Power was getting to the motherboard (on-board LED was on) but pressing the power button (whether through the case button or on-board power button) did not turn it on.
I started a process of diagnosis, and eventually found that if I unplugged the 3.5" internal card reader from one of the USB headers, the motherboard turned on fine. So, the problem must have been a short within the card reader. Life goes on.
But two weeks ago, with the card reader still unplugged, the same thing happened again.
This time I stripped EVERYTHING from the build, going as far as to remove the entire motherboard from the case with nothing in it but a stick of RAM, the graphics card and a CPU, and it STILL wouldn't turn on.
In a desperate last attempt, I stuck a couple of paperclips into the correct contact points within the ATX 24v power connector and shorted them to "force" the PC to turn on. It turned on fine, but of course as soon as I broke contact between the paperclips, it would turn off again.
However, if I pressed the power button straight after this, it would turn on normally. Everything works and is rock solid. Everything is plugged into the build. No BSODs. No crashes. If I shut the machine down, the only way to turn it back on again is to short those paperclips again and then very soon after that press the power button.
I do not know what is causing this, and why "jumpstarting" it by doing the paperclip-short would cause the issue to temporarily disappear.
Any ideas?
Answer: Sounds like a motherboard fault but I would try another power supply to make sure.


Was hero worship the same as god worship?

Question: In Greek Mythology, their are a few special heroes (Diomedes being one) who, after Death claims them, have a shrine/temple build in their honor and for worship. Was the worship they received similar/same to that of a god, or completely different? In what ways?
Answer: In Proclusean hierarchy heroes were higher ranking than mortals, purified souls, daimons, lower than angels, archangels and Deities. They received worship and commemoration alike to the Gods. In fact they were - for example - Herculean mysteries and Herculean temples, stemming from the Eleusis rites (Heracles was a succesful initiate of these mystery schools). It is difficult to tell from a qualitative perspective what was the cognitive and spiritual way of expressing the worship, but I guess that in these days, when mixing and exchanging Deities was common, one might even have such instances when a hero received greater worship than a higher Deity in a different region.


Is there a set of NP-hard problems that are most commonly used for proving NP-hardness?

Question: Are there any NP-hard problems that are considered kind of the standard for reductions? There's so many but it feels like some come up more often than others (for example Vertex Cover, Independent Set, 3-SAT, etc.). I'm sure people just pick whatever is most convenient, but where's the boundary between "more useful" and "too obscure" when choosing a problem to reduce from?
Comment: Thanks for moving the question from SO to here. I believe you will get good answers now.
Comment: https://cs.stackexchange.com/q/1240/755
Answer: Most textbooks will have a set of 'core' NP-Complete problems from which all their examples and exercises would reduce from, which are probably the ones you list (3SAT, Vertex Cover, Independent Set, Clique, k-Coloring, Set Cover, Dominating Set, Hitting Set, Subset Sum, Knapsack.)
A bigger set of 'standard' problems would be Garey & Johnson's book. Beyond that, people look at hard restrictions of the standard problems (i.e. k-coloring for k=3, Exact Cover version of set cover, not-all-equal 3SAT, etc).
Beyond that, it gets fairly domain specific.


Definition of a computable (or recursive) set

Question: I am new to computability theory, but I understand the usual definition of a "computable set" S when S is a subset of the natural numbers.  Is there a notion of "computable set" that doesn't involve just subsets of the real numbers?  In particular, I am interested in the set $\Sigma^{\omega}$ for some finite alphabet $\Sigma$ (this is the set of right-infinite words over $\Sigma$).  Is there a notion of a computable subset of $\Sigma^{\omega}$?   Off the top of my head, it seems that a possible definition would be to say that a subset $X$ of $\Sigma^{\omega}$ is computable if each sequence in $X$ represents a computable function $\mathbb{N} \rightarrow \Sigma$, but that doesn't seem correct.  Any help is appreciated.
Comment: Maybe the definition you proposed may yield some interesting results. One thing to note is that with your definition all computable subsets of $\Sigma^\omega$ correspond to subset of $\omega$. $X \subset \omega$. $X \subset \omega \Leftrightarrow \{\Phi_e : e \in X\} \subset \Sigma^\omega$, where $\Phi_e$ is the computable function with index $e$.
Comment: @dan I think you should change the title to "Definition of a computable (or recursive) subset of $\Sigma^{\omega}$" so readers know that you're not asking a question about the definition of a computable set of natural numbers.
Answer: "Computable" subsets of $2^\omega$ are the clopen sets under the product topology (generated by basic (cl)open sets of the form $[\sigma] := \{X \in 2^{\omega} \colon \sigma \prec X \}$, where $\prec$ denotes "is a prefix of"), which is why clopen sets are called $\Delta_0$ in the Lightface Borel hierarchy. (Recall that $\Delta_0$ in the arithmetical hierarchy means computable.)
Prateek's answer is essentially proving that any clopen subset of Cantor space $2^\omega$ is a finite union of basic opens. I think a better word than "computable" for these sets is "decidable", since given any infinite sequence and clopen set you'll eventually know if that sequence is the clopen set or not (by Prateek's answer).
Comment: I've limited my answer to the case $\Sigma = 2 = \{0,1\}$, but everything I've said holds for general finite $\Sigma$.
Answer: Your definition does not seem right, as it talks only about individual elements of $X$, but nothing uniform about $X$. One could try to generalize from the definition of computable subsets of $\Sigma^*$ (all finite words over $\Sigma$), but as shown below, this gives something rather surprising. Here is the definition for $\Sigma^*$:

$X \subseteq \Sigma^*$ is said to be computable if there exists a Turing machine $M$ which on every input $x \in \Sigma^*$, halts and says "yes" or "no" accordingly as $x \in X$ or $x \notin X$.

This is equivalent to the notion of computability of subsets of $\mathbb N$. One could try to generalize this by just replacing $\Sigma^*$ with $\Sigma^\omega$.

$X \subseteq \Sigma^\omega$ is said to be computable if there exists a Turing machine $M$ which on every input $x \in \Sigma^\omega$, halts and says "yes" or "no" accordingly as $x \in X$ or $x \notin X$.

One might ask, what does it mean for a Turing machine to take $x \in \Sigma^\omega$ as input? Well, let's just say that $x$ is written on a tape available to the TM, just like for a finite word $x$. Of course, in finitely many steps, the TM can access only some finite prefix of an input infinite word.
Suppose we have a Turing Machine $M$, for a computable subset $X \subseteq \Sigma^\omega$. For every $x \in \Sigma^\omega$, $M$ run on $x$ eventually halts (and says yes or no). $M$ has examined only a finite prefix of $x$ before deciding whether to say yes or no. So we get

For every $x \in \Sigma^\omega$, there exists $N$ such that for any $y$ which agrees with $x$ in the first $N$ places, $(x \in X \iff y \in X)$.

This $N$ depends on the input $x$. Here's something interesting : we can get a uniform $N$ which works for all inputs (our $M$ and $X$ are still fixed)! More precisely,

There exists $N$ such that for every $x,y \in \Sigma^\omega$, if $x$ and $y$ agree in the first $N$ places, then $(x \in X \iff y \in X)$.

Here's a proof: For any finite word $\sigma$, say $M$ halts on $\sigma$ if on any infinite input which begins with $\sigma$, $M$ halts without examining more than the first $|\sigma|$ symbols of the input. This definition clearly does not depend on which infinite extension of $\sigma$ we choose. Let
$$S = \{ \sigma : \sigma \in \Sigma^* , M \textrm{ does not halt on } \sigma \}$$
$S$ is prefix-closed, and so can be naturally thought of as a tree. This tree is finitely branching (every node has finitely many children) since $\Sigma$ is finite. Note that since $M$ halts on every infinite input, every $x \in \Sigma^\omega$ has a finite prefix $\sigma \in \Sigma^*$ such that $M$ halts on $\sigma$. This means that our tree $S$ cannot have any infinite path (that is to say, $S$ does not have words $\sigma_0, \sigma_1, \ldots$ such that $|\sigma_i| = i$ and each $\sigma_i$ is a prefix of $\sigma_{i+1}$). From König's lemma, we get that $S$ is finite! (this is not hard to prove directly)
As $S$ is finite, let $N$ be one plus the maximum length of any word in $S$. For any input $x$, $M$ halts after examining at most the first $N$ symbols of $x$. This means that
$$X = T\Sigma^\omega$$
where $T$ is a subset of the finite set $\Sigma^N$. So as per this definition, computable subsets of $\Sigma^\omega$ aren't very powerful, they just behave like finite sets.
As a bonus, observe that from a description of $M$ (if we already know $M$ always halts), we can effectively compute the $N$, by building up the tree $S$. So if we are given two such TMs $M$ and $M'$, we can effectively compute if $M$ and $M'$ compute the same set : just get the corresponding $N$ and $N'$, and check for all finite words of length $\max(N,N')$. This is interesting because the corresponding result is not true for computable subsets of $\mathbb N$ or $\Sigma^*$.
(Aside: instead of generalizing computability, if one generalizes the notion of regularity from $\Sigma^*$ to $\Sigma^\omega$, one gets omega-regular languages.)


How to find out your body weight while travelling?

Question: While on the road you don't have your handy scales at home, and without making an appointment to see a doctor, where else could you find some scales to determine your on-the-road weight? This is useful if say, your travel medicine is weight-related...
Comment: Will update, yes :)
Comment: I cannot imagine any medication that would require a dosage change after the gain or loss of 2 or 5 pounds. I expect you would need to change your weight by 20 pounds or more to see any such consequence. Therefore take a tape measure and measure your waist (or some other consistent dimension) - as long as it stays stable, no doubt your weight is also. If it changes a lot (an inch?), seek out a place to be weighed.
Comment: you mean your own body weight, right? I first thought you were talking about your luggage
Comment: About 2 inches :)  But hey, this new hostel has a set of scales, victory!
Answer: Ask at your hotel or hostel. I work in a hostel and we have about four sets of scales so guests can make sure their luggage won't be over the weight limit for their flight.
I'm sure we're not unique in this regard.
Comment: Well that was easier than thought, my hostel in Ulaanbaatar had just such a scale :)
Answer: When you are at the airport you could step onto the conveyer belt of a checkin desk that is not in use. The scales normally still show the weight.
If you happen to find a shop that sells stones (for stone carving) they usually have scales to measure the weight of the stone to calculate the price. Those scales should be able to hold you.
You could try to befriend someone local and ask to borrow his or her scale. You could also use the couchsurfing website to contact people and ask them just to borrow their scale.
Or you could try to find a store that sells scales and just use it in the store without buying it.
Sometimes you can find a scale inside a gym or swimming pool (maybe more common in Scandinavia?)
Comment: Yep, at least in Finland nearly all gyms and public swimming pools have a scale, in the dressing rooms or elsewhere. (Come to think of it, for me gym is the only place where usually I weight myself, as I don't own a scale...)
Answer: In many countries you actually have people standing around on street corners with their scales which you can use for a small fee.
The problem may be that you may use your home scale naked, while you are dressed to various degrees when on the street (depending on the weather). Also some of the scales look pretty old, and may not be super correct. But at least is it gives you some idea.
Comment: Do you have any examples of countries/cities where this is the case?  I have never noticed this (although in fairness I haven't exactly been looking).
Comment: These guys are pretty common in Central Asia.
Answer: In the UK pharmacies sometimes have scales that require a coin to be activated.
If your hotel room has a bath, measure the dimensions, fill it up completely with water, climb in and measure how much water is displaced. Don't blame me if the hotel complains about water damage :)
Comment: "The weight of an object or substance can be measured by floating a sufficiently buoyant receptacle in the cylinder and noting the water level. After placing the object or substance in the receptacle, the difference in weight of the water level volumes will equal the weight of the object." http://en.wikipedia.org/wiki/Displacement_(fluid)
Comment: *love* the scientific approach to measuring it :)
Comment: That will only tell you your *volume*. It may work well enough if you happen to already know your average weight per cubic centimetre (-:
Comment: Not true, it will tell you your weight if you are floating.
Comment: So find a really big bath.
Comment: @victoriah: How can I accept a right answer in an off-topic comment thread? (-:
Comment: I was literally just re-reading and wondering that.  If we were the same density as water, sure.  And alas, our average weight per cubic centimetre changes all the time...
Comment: You can tell I'm taking this seriously :)
Answer: For completeness sake, pharmacies in Italy often have both scales and  sphygmomanometers to measure blood pressure. Both are available to the customers, and are either free or coin-activated.


Why did Yaakov give Yosef Shechem 'one more than his brothers' specifically?

Question: וַאֲנִי נָתַתִּי לְךָ שְׁכֶם אַחַד עַל אַחֶיךָ - bereshis 48:22. Yaakov previously gave Yosef an additional article of clothing, which spurred the brother's hatred of him (Yosef). Why would Yaakov go out of his way to say that this gift of 'Shechem' was one more than his (Yosef's) brothers once again?
Answer: Derishos Shabbos - The Apta Rav - page 231 - top left says that Shechem was given as payment for Yosef taking care of Yaakov's burial, which the other brother's were unable to do.

ושכם הרי  אינו נותנו לו בחנם רק עבור מה שמטריח  אותו בקבורתו מה שאין
  סיפק ביתר הבנים  לעשותו
Answer: In my answer to another question, I summarized the approach of R' Goldvicht ZT"L as to why Yosef did not reveal himself to his brothers.  The climax of that answer is that when Yosef saw that Yehuda was willing to put himself on the line to save Binyomin, he understood that the perceived jealousy that had existed between the other brothers and the sons of Rachel had been overcome (see there for the whole story).  Based on this, R' Goldvicht also explained how Yosef could show favoritism to Binyomin by giving him 5 sets of clothing while giving the other brothers only 1 each.
The same could be applied to Yaakov - it had been demonstrated that the jealousy that had existed was something they had overcome, and Yaakov felt it was now actually safe to treat him differently.
Answer: Pirkei D'Rabbi Eliezer, Perek 38, states:

ויצאה דינה לראות בבנות הארץ... ושכב עמה והרתה וילדה את אסנת
And Dinah went out to gaze upon the daughters of the land... and [Schechem] slept with her, and she became pregnant, and she gave birth to Asenath.

With all the people of Schechem dead, the heir to the throne is Asenath. When she marries Yosef, the deed of the land is passed into his family. Thus, Ya'akov is merely deciding not to confiscate and redivide Yosef's property.
Comment: It belongs to Ya'akov. However, he decides to return it to Asenat's, the rightful heir, family, since all the land will end up going to the shevatim anyway.
Comment: That's an interesting idea, but it doesn't fit with the words נָתַתִּי לְךָ "I give to you" so well.
Comment: Ya'akov has technically conquered the city (through his sons), as he states in our pasuk. Thus, he could just throw it into the big Nachala pot, but instead, he creates a side pot that only Yosef's descendants have a right to.
Comment: Either it's Yaakov's, in which case Asenat's birthright is irrelevant, or it's Asenat's, in which case Yaakov's giving it is irrelevant. You can't eat your cake and have it too.


Does a dedicated transport for a troops unit retain objective secured after the troops disembark?

Question: If I take a devilfish for my strike team in a combined arms detachment, will the transport have objective secured even after the unit has disembarked? If so, can I disembark the fire warriors on an objective and then take the devilfish to score at another objective?
Answer: It does, and you can. You don't even have to start the Strike team in the devilfish, so you could begin the game holding two objectives. A transport bought separately (generally most other transports are Fast Attack) will not have Objective Secured unless it is "Troops" or the mission says it's type has ObSec.
It's worth noting that if you have Pathfinders in a Devilfish and Firewarriors in a second, only one of them will have Objective Secured. The only really confusing situation is if both units disembark and then switch vehicles... Units in a transport do not confer (or revoke) ObSec status to the vehicle.
Comment: Pathfinders are Fast Attack, not Troops, so wouldn't have objective secured (nor would their transport).
Comment: Why would _only_ one of the two devilfish have Objective Secured if both the Pathfinders and Firewarrior units act as troops and can take the Devilfish as a DT?


Webform CiviCRM country field

Question: Just wonder if there is a way to show country name in country field while keeping the field readonly/"disabled" on webforms? For example, you want users to see their countries but not editing them. The closest I can get is to change the field type to textfield and "disable" it but it shows the country code instead of country name.
Answer: If you're creating a link from elsewhere that pre-populates the information, you could use a Drupal Views block that displays the country field as read-only.  (For reference: Displaying a Views block with a CiviCRM-enabled webform)
Comment: Hi Allen, just wanted to say thanks for all your contributions lately! Much appreciated! Cheers, Joe
Comment: Thanks for saying so!  Glad to be a part of the Civi community.

Webform CiviCRM country field


Does trub effect your gravity reading?

Question: took a gravity reading today at the end of the transfer from the kettle and there was quite a bit of trub in the cylinder, like the whole flip'n tube. so would the trub hold the hydrometer up and give a false reading?
Comment: It's explained pretty well [here](http://homebrew.stackexchange.com/a/9512/2982)
Answer: If the trub is actually physically holding the hydrometer up, preventing it from moving down, then unambiguously: yes, the trub will render your hydrometer reading useless.
If, on the other hand, the trub is suspended in the liquid, it is a mixed bag. Suspended solids will impact a hydrometer reading, but for brewers it is usually very minimal. The only actual measurements I've seen have put the effect at well below even a single point of gravity (thousandths digit on SG scale), though it is conceivable that the effect is more significant in very trub-heavy samples. Still, it's hard to imagine that we'd see an effect of more than a couple of points.
Comment: @Ryan Shdo - what was the difference between your trubbed reading and your unobstructed reading?
Comment: agreed and with my experience I should know to wait for the trub to settle, but I kinda fell stupid having to leave asap. I came home after work (now) and got an "unobstructed" reading, and it was right where I needed to be. I always wait a day or two for answers but Plus one for now for sure!

Does trub effect your gravity reading?


Permalinks vs. duplicate merging

Question: Suppose that I link (offsite) to an answer that I gave to a question that was later closed as a duplicate, e.g. as I just did to my answer here. Suppose that my answer is later merged into the original (non-dup) question. Will my offsite link to my answer to the dup question no longer work? What is the proper way to link to avoid this problem? Or perhaps there is no problem since the new mods do not seem to be merging duplicates? Please advise since link rot is highly undesirable.
Answer: If the merged question stub is deleted, it will auto-redirect to the target question.
Otherwise, there is always a link to the merged question in the stub.
Answer: My reading of http://blog.stackoverflow.com/2010/06/improved-question-merging/ is that your original link will either now point to a stub page that has a link to the merged question, or it will just work.
Comment: Thanks much, that's reassuring. Regarding permalinks, is it always safe to delete everything after the question number in the url?
Comment: @Bill: If you just want a link to the question, yes, I believe so, and I believe you can even shorten "question" to "q" (based on [this blog post](http://blog.stackoverflow.com/2010/09/announcer-booster-and-publicist-badges/)).

Permalinks vs. duplicate merging


How to map out user actions with connected features?

Question: I am dealing with a new feature for our dashboard and I am trying to map out all the user's possible actions and connect them to features we have so I could see if we are missing something and improve flows. I already have user stories created epics/tasks but I need some kind of step-by-step approach of the user so I am thinking something between customer journey/user flow and service blueprint. What kind of tool or process would you use for this exercise?
Answer: I was going to write the tools I used but there are lots of them which would be more appealing to you and more suitable for your experiences on tools you already used.
So I found more appropriate to share the lists below already available at,
Top-20-customer-journey-mapping-tools-an-overview
Best-customer-journey-mapping-tools
Hope that would help.
Comment: Thanks a lot for the list! I will search through and try to find something that would suit me :)
Comment: happy you enjoyed..
Answer: I think that the exercise Effect Mapping (also known as Impact Mapping) could be something for you.
How To
To develop an effect map you use a hierarchical diagram or a mind mapping tool and start with:

writing down the site/app business goals
connect the target groups/personas/users that is needed to fulfill the goals. Then you
connect the user's goals to the persona and then you
connect the solutions/features that support their goals.

In your case I think that you could start backward; from the feature that you have developed to the user goals (or the epics/tasks) and so on if you wish.
More info and examples

A short explanation of the concept:
https://angner.se/services/effect-mapping/
A simple example of a finished map:
https://www.impactmapping.org/example.html


What is the strongest crop in Banished?

Question: I have observed that some crops seem to withstand colder weathers than others. For example, squash dies at around 25f while cabbage dies at 32f. Which crop can withstand the coldest weather?
Answer: Despite what appears to be common belief here, squash are the most resilient to cold, being able to go down to 25f. From the resource files:

Squash:

float _growthTemp = 55.0;
float _growthTempRange = 30.0;

Pumpkin:

float _growthTemp = 60.0;
float _growthTempRange = 20.0;

However, it also appears that snow kills all crops, regardless of temperature tolerances.
Answer: In Banished, Pumpkins are the crops that are able to stand up to the most frost and cold. If you use them, make sure to plant them so they are ready for Winter as well as the first few weeks of Spring.
Answer: Pumpkins are the most resilient plant in the game. Though I have some uncertainties in my answer, just from reading the comments on the Wiki, and several other resources, I do believe that pumpkins are the most resilient plant.
Answer: Pumpkins i believe, as i read on the Wiki.

What is the strongest crop in Banished?


Issues with Lucene.NET version 3.0.3

Question: I've been using Lucene.NET v3.0.3 on a project for several of weeks ago, it very good library in addition to FacetedSearch is wonderful; but there are some points to need to say regarding this version, and I wish some tell me the best practice to tackle:

It does not support nested documents (relation between documents), [as it does in lucene java latest versions], for example on my domain model i have (Request, Applicant), one Request contains many Applicants.
a. In Indexing phase:i indexed one Request for one Applicant per document,in order to search particular information on Request and Applicant as will;  but this makes:

redundant request information on different documents,
difficult to use faceted search on (Request) on such document
Anybody can tell me if there any (way, plugin, code) to handle this issues? but not using solar library.

How can return unique result (distinct), Is it the only way to return the whole result then implement code to distinct on the result; this makes performance problem on 1 Million document.
Any Implementation on extra cache level, example caching a document field (requestID) for fast performance querying.
Any news regarding the next Lucene.NET release date?
Any implementation on nested query results on different indexing files.
Comment: You should split each question into it is own post as most aren't directly related and you'll have a better chance of having some answered.
Comment: http://lucenenet.apache.org/community.html
Answer: If you can map your relationships to hierarchies, you might look at my Stupid Lucene Tricks: Hierarchies (edit: updated link) which talks about using path enumerations to express and search hierarchies in Lucene.

Issues with Lucene.NET version 3.0.3


Stuck while upgrading from ubuntu 11.10 to 12.04

Question: i have ubuntu 11.10 installed within windows vista. i am trying to upgrade it to 12.04.  but the update manager seems to be stuck at "Installing the upgrades" while configuring manpages. i did a restart but after which my wi-fi driver was lost. after the restart, it started witing 12.04 but my wi-fi driver which i had installed was not to be found. now what to do.it did'nt upgrade fully.
Comment: You will have to install fresh-

This will help-

http://askubuntu.com/questions/136930/lost-power-while-upgrading-ubuntu/136939#136939
Answer: If it where my desktop/laptop I would ...
Backup user data to external storage and to a fresh install.
If your wifi adapter isn't working with a fresh install, then I'd do a 'lspci' and find the wifi adapter model and google that + ubuntu 12.04. It's almost certain that someone has already solved the issue for you. But I can't tell because you didn't post a lot of details other than a failed upgrade.


XML and Registry

Question: Which method is considered to be best practice for setting storage for applications: XML or Registry?  What are the benefits/downsides of using either of these?
Comment: It depends. If I was targeting Windows alone, I'd think about using the registry. But generally, I'd use the simplest file format that could possibly do the job (well) - in simpler cases, a plain old `.ini` file. XML is a heavy, flexible format, powerful enough for tasks like storing a whole database for import/export. But it's overkill for simple key-value pairs and other simple relations. Especially when you'd need to add an XML parser for the config files alone.
Comment: "setting storage"?  Do you mean "storing an application's settings"?  Also, XML is just a language (it can work in a file or in a database) and registry only applies to Windows.  It would help if you could clarify the platforms, and why you're comparing a language with an OS feature.
Comment: XML makes a rather lousy for storing settings and most other lightweight data.
Comment: @delnan would I be correct in assuming then that you use the registry for this kind of storage or do you use a different approach?  Can you elaborate on why you think XML is lousy for this purpose?  Thanks!
Answer: The registry is Microsoft's solution to storing application information relative to a user.  The advantages of this include:

Being able to hold application settings for each user of the computer.
Having an API already available for using this feature.

However the disadvantages include:

Platform dependent.
Limited to the
amount of information for a single
block of data.
Loss of portability
(you lose settings when you install
on another machine)

I personally vouche for using XMLs if not merely for the fact that it allows you to copy the entire application to another computer and have it work fine with the same settings.  Plus, if you write your application flexible enough, you can write entire projects onto XML files, something I wouldn't dare attempt with a registry.
It's convenient initially to use the registry, but it's far better in the long run to use XML files in my opinion.
Answer: For information that may be needed by other programs, such as the location and current version of an executable, store that in the registry.
For information that is only needed by your application, store that in a file in the user's AppData directory.  Use XML or whatever you find suitable, depending on the structure of the data.
That allows the registry to do its job - function as a central registry of applications - without cluttering it up.
It'll also make your testing life a little easier, since you can wipe the AppData file and reset the app back to defaults.
Answer: A major downside of the registry in Windows Vista and forward is that you can only store stuff in HKEY_CURRENT_USER unless you're running elevated.
That means that if your non-elevated program stores stuff in HKCU, and the user installs a new version of the program, the installer likely runs elevated, which may mean running under a different user account.
That means that you can't rely on being able to read program information out of the registry from the installer, because the installer is running under a different user, who has different stuff in their registry. :(
Answer: On Windows, I feel program settings belong in the registry. While xml-files may be easier to copy by hand, backup and restore procedures routinely include the registry, and they also support multiuser setups, where program install directories may not be preserved (nor would I want that, because paths may not be the same, and installers usually also take care of associating files and creating shortcuts. So on Windows, I mostly prefer installers over copying directories.
A function (from the gui) to export and import settings may really help migration though.
Project settings are perhaps better stored in the document or project directory. That allows for version control and sharing across users.
Comment: The whole U3 application (flash drive installation) thing relies on *not* having things in the registry, so for portable apps even on Windows the registry might not be the best choice.

XML and Registry


Can 2 members of a family use the same APC kiosk when they are entering the US under different visa programs?

Question: Regarding APC kiosks, what happens when one member of the family is entering the US with an ESTA form and the other one with a B1/B2 Visa? Can they use the APC kiosk together? At certain moment, the system asks whether you are travelling under visa waiver program or B1/B2 visa or if you are a US or Canadian passport holder or if you have a green card.  In my case, I will select "travelling with ESTA" but I'm afraid that when choosing "yes" to the question "are you travelling with other member of your family?" the system will only require to repeat passport scanning and fingerprints for the second person and will not ask the form of entry which is different from mine. Hope the question is clear.
Comment: Which airport will you use to enter the US? The kiosks are slightly different at every airport (unfortunately) and they may behave differently.
Answer: Ask the person at the kiosks. Clearly state that you're both traveling together under different visas and ask what you should do.
Make this clear the CBP officer also. The officer will likely want to know why a B1/B2 visa holder are traveling together and will also likely wonder how the start of your visas/travel dates correlate with one another.
Since you're traveling with a family member who is under a different visa, my advice is to just ask the person at the kiosk. Make it clear that you're traveling together but are either parting ways or staying together after immigration control.
Comment: "The officer will likely want to know why a B1/B2 visa holder are traveling together": it must be fairly common for family members to enter together with different status.  They could have different nationalities, or all be eligible for the VWP but one has a visa from an earlier trip, or one could be ineligible for the VWP for some reason.
Comment: Yes it will be common, doesn't mean the CBP officer won't want to know.


How to auto mount disk drives in gnome-shell?

Question: I have 1 usb disk and 1 esata disk plugged in my pc.
When I log in gnome-shell the usb one is mounted automatically.
Is there any way to mount the esata disk too, without modifying fstab?
Answer: No.  The system assumes that sata disks are internal, and therefore, does not auto mount them if they don't have an fstab entry.  Is there a reason you don't want to add an fstab entry?
Answer: A better and easier way to do that in Gnome3.4 (with Gnome-Shell) is using the GNOME Disk Utility.
I had to go for that because Ubuntu did not like de AriOS package (warning said it's bad software) and the pySDM is not that clear about the partitions. I always get confused trying to remember wich one is /sda1 or /sda3 or what so ever. It should show the labels!
The Gnome Disk Utility is really great. You can find it at Activities > Aplications > System Tools > Disks (sorry, not sure 'cos I'm using the brazilian-portuguese translation).
Tks!
For my brazilian fellows now:
A melhor opção é usar o aplicativo Discos do Gnome (gnome-shell). Vá em Atividades > Aplicativos > Ferramentas de Sistema > Discos. Clique na partição e no ícone de configurações abaixo dela. Lá, desative a montagem automática e escolha a opção LABEL no último menu, pois essa opção monta a partição com o nome (label) que você deu para ela no Windows.
Answer: There is a system service (man udisks(7)) that handle a mounting jobs in cooperation with udev. You can write udev rule to mark your esata disk as external and partitions on disk as automountable. Something like that:
KERNEL=="sd[b-z]", SUBSYSTEM=="block", SUBSYSTEMS!="usb", ENV{UDISKS_SYSTEM_INTERNAL}="0"
KERNEL=="sd[b-z][1-9]", SUBSYSTEM=="block", SUBSYSTEMS!="usb", ENV{UDISKS_AUTOMOUNT_HINT}="always"

To play around with this, try udisks console tool with --mount, --unmount, & --monitor options.
It works for me on Ubuntu 12.04.1 GNOME3 Fallback session


After two buffers operations (+/-), why is the result file bigger than the original?

Question: First file ( .shp ) had 1000KB, after 2buffers ( buffers on polygon, 1st buffer +100,
2nd buffer -100 ( small things near polygon should be removed ))
in quantum gis file grown to 1500KB, and after the same 2 buffers in postgis file has 20000KB.
Anyone can tell me why?
Comment: You probably have introduced a large number of new points. Try using the simplify algorithm in postgis.
Comment: Spot on johanvdw. When you buffer, it doesn't just 'inflate' the polygon's vertices, it adds new vertices to give you a more rounded shape. When you de-buffer, vertices are not removed unless they fall within the tolerance parameters of you GIS and/or they are absolutely identical (unlikely in most scenarios due to floating point errors). Therefore, the other effect you will get is that an inflate-then-deflate buffering process will not give you the same polygon outline as you had before.  This might not matter for your use-case, but you should be aware of it, in case it is critical.
Comment: Your comments would form the complete answer. Please post one.
Comment: @johanvdw - can you please make your comment an answer.
Answer: You probably have introduced a large number of new points.  Try using the simplify algorithm in postgis.
As Sylvester points out in his comment on your question many vertices are added to create rounded shapes near the corners, and when you reverse that operation new points are created which did not exist before.
Answer: (as per Underdark's request)
Spot on johanvdw. When you buffer, it doesn't just 'inflate' the polygon's vertices, it adds new vertices to give you a more rounded shape. When you de-buffer, vertices are not removed unless they fall within the tolerance parameters of you GIS and/or they are absolutely identical (unlikely in most scenarios due to floating point errors). Therefore, the other effect you will get is that an inflate-then-deflate buffering process will not give you the same polygon outline as you had before. This might not matter for your use-case, but you should be aware of it, in case it is critical


Can you eat food that has been bought on Shabbos by guest?

Question: If you live in a house with people who do not keep Shabbos and you all have dinner, and a guest or someone else living in that house brings kosher food for dinner bought on Shabbos, can a Jew eat that food on Shabbos? You did not buy the food or ask that someone should, and the food was not cooked on Shabbos.
Comment: Not stupid, but you wrote during Shabbos in the US and Israel where many site users reside, so expect answers once people get back online
Comment: stupid question or is everyone busy?
Comment: [Welcome to MiYodeya](https://judaism.meta.stackexchange.com/a/3887/11501) and thanks for this first question. Can I recommend you take the [tour](https://judaism.stackexchange.com/tour) to get a sense of how the site works? Great to have you learn with us!
Answer: NordicMountain, as a new user to Mi Yodeya, welcome aboard and Shavuah tov.
Congratulations on trying to keep kosher too. Eating only kosher food helps to keep someone Jewish, spiritually healthy and their faith strong. May G-d bless you and strengthen you in your observance.
Without getting into great detail, generally speaking traditional Jewish practice is not to derive benefit, including eating, from the actions of another Jew violating any of the commandments.
You haven't specified if the person who purchased and brought the food to your apartment was Jewish. Non-Jews are not commanded to observe Shabbat. So that aspect would not be a problem for a non-Jew.
Additionally, you haven't indicated if the food was in a sealed package and other details that would be relevant to answering your question in a complete way.
In keeping with the general policy of this site, you should consult with your local Orthodox Rabbi who knows you and your specific situation to get the correct answer to your particular question.
All the best.
Answer: If you should acquire food on Shabbes that came into your possession through another Jew's Shabbes transgression (either because s/he purchased it on Shabbes, or due to the means by which s/he transported it on Shabbes to your place), you are only allowed to derive benefit from it once Shabbes is over.
This ruling is recorded by the Rambam (Hilkhos Shabbes 6:23) and is in the Tur (Orach Chayim 318:1). It might also be the opinion of the Shulchan Arukh (ibid.), although the latter only mentions the aveira of cooking. If you want to study this sugya, it's predicated on a mishna (Terumos 2:3), and is found in the gemara in various places as well (Bava Qama 71a, Chullin 15a and Gittin 53b).
Comment: I don't know your background, but if you can find the biography of the Baba Sali, zt"l you might find the story about the two pushkas which he kept when having yechidut of interest.


What could be causing a dripping sound inside the wall?

Question: We have the problem with the dripping sound. Whenever we turn on the hot or cold water on in bathroom on the first or second floor, we can hear the dripping sound behind the wall. Usually lasts 5 min after we turn off the water. We checked all walls. Couldn't find anything. Not sure if should we spend money for plumbing inspection. What could the reason be for this dripping sound?
Answer: Often this isn' t a drip at all, but pipes moving due to thermal expansion and slipping in their supports. If it doesn't happen when you run COLD water, that's almost certain.
Answer: I would get it looked at, it could be one of 2 things in my opinion:
1: (the bad, but likely) you have a leak in the drain pipe.
2: (the good but unlikely) some sort of build-up is causing a dripping down the inside of a vertical pipe.
In the long run it WILL cause damp related problems such as rot and smells...


What is the benefit of compiling your own linux kernel?

Question: What benefit could I see by compiling a Linux kernel myself?  Is there some efficiency you could create by customizing it to your hardware?
Comment: the simple question of *what is the benefit* is becomes **vague** or taken out of context very quickly.  It would be way better to ask `What are the pros and cons of compiling your own kernel?`  Cons=not easy, many situations no value added.  Pros=security, performance, if you know what you are doing,NAS devices for example, using linux to make some piece of hardware work and have networking and graphic capability.
Answer: In my mind, the only benefit you really get from compiling your own linux kernel is:
You learn how to compile your own linux kernel.
It's not something you need to do for more speed / memory / xxx whatever.  It is a valuable thing to do if that's the stage you feel you are at in your development.  If you want to have a deeper understanding of what this whole "open source" thing is about, about how and what the different parts of the kernel are, then you should give it a go.  If you are just looking to speed up your boot time by 3 seconds, then... what's the point... go buy an ssd.   If you are curious, if you want to learn, then compiling your own kernel is a great idea and you will likely get a lot out of it.
With that said, there are some specific reasons when it would be appropriate to compile your own kernel (as several people have pointed out in the other answers).  Generally these arise out of a specific need you have for a specific outcome, for example:

I need to get the system to boot/run on hardware with limited resources
I need to test out a patch and provide feedback to the developers
I need to disable something that is causing a conflict
I need to develop the linux kernel
I need to enable support for my unsupported hardware
I need to improve performance of x because I am hitting the current limits of the system (and I know what I'm doing)

The issue lies in thinking that there's some intrinsic benefit to compiling your own kernel when everything is already working the way it should be, and I don't think that there is.  Though you can spend countless hours disabling things you don't need and tweaking the things that are tweakable, the fact is the linux kernel is already pretty well tuned (by your distribution) for most user situations.
Comment: I'd argue that if you want to build your own kernel simply for the learning experience, that you do it with a source-based Linux distribution like Gentoo or Linux From Scratch.  The Gentoo stage 2 install documentation is an excellent guide to understanding what it means to build Linux from the kernel up.
Comment: @rozcietrzewiacz Knowledge is of the utmost value. Compiling a kernel helps you extend your knowledge. If you don't buy that, then here's this - knowledge is power, and people pay good money to get power, and money holds value in today's world, so by the transitive property.... :P
Comment: Of course you know you actually contradict yourself in your answer. If the only benefit of compiling the kernel was to learn how to do it, then it would be useless - have no value. But then a few words later you say it is a valuable thing...
Comment: I agree, It is worth it only for the knowledge gained.
Comment: Agreed... those two projects are built for this type of thing.
Comment: Gr. stupid timeout... I agree, It is worth it only for the knowledge gained.  BUT- Sometimes there are performance gains. Going from 2.6.32 on stock debian stable to 3.0 or greater COULD show show gain.  Consider that the 2.x kernel was built to support everything, while a custom built kernel will most likely not.  My experience on debian stable has proven to me that it's worth it for the performance gains.  But other distros might not feel any different at all.  So.. yes and no.  Plus it's just great to know you lovingly hand crafted the innermost part of your OS. =D
Answer: Most users do not need to compile their own kernel, their distribution has done this work for them.   Usually distributions will include a set of patches to either integrate with certain parts of the way the distribution works, backports of device drivers and fixes from newer, but unreleased versions of the kernel or features that they are pioneering with their users.
When you compile your own kernel, you have a couple of options, you can compile an official Linus Torvalds kernel, this will not include any of the patches or customizations that were added by your distribution (which can be good or bad) or you can use your distribution rebuild tool to build your own kernel.
The reasons you might want to rebuild your kernel include:

Patching bugs or adding a specific feature to a production system, where you can not really risk upgrading the whole kernel for a single fix or two.
To try out a particular device driver, or a new feature
To extend the kernel, work on it
testing some of the "Alpha" modules or features.

Many developers use it to create also custom versions of the kernel for embedded systems or settop boxes where they need special device drivers, or they want to remove functionality that they do not need.
Comment: +1. Kids these days, they don't even know what 'make menuconfig' means and never had to patch their kernel network code to prevent being pwned by script kiddies. Fortunately those days are mostly gone.
Comment: you should add `bisect`ing to find where a bug was introduced...
Comment: amazing how this comment is up voted when it has nothing to do with the OP's question.  "Most users do not...." c'mon now.  OP's question is very clear about wanting to know benefits; not your opinion of what "most users" do here and there.
Comment: its nice sometimes to break the rules in a way that hurts no one.
Answer: Compiling the kernel yourself allows you to only include the parts relevant to your computer, which makes it smaller and potentially faster, especially at boot time. Generic kernels need to include support for as much hardware as possible; at boot time they detect which hardware is attached to your computer and loads the appropriate modules, but it takes time to do all that and they need to load dynamic modules, rather than having the code baked directly into the kernel. There's no reason to have your kernel support 400 different CPUs when there's only one in your computer, or to support bluetooth mice if you don't have one, it's all wasted space you can free up
Comment: I agree with most of your answer, but I'd be curious for some hard facts on "considerably faster".  I wouldn't want to give a new user the impression that their desktop will run generally faster with a hand-built kernel (from my experience with Gentoo, this is simply not true). Can you quantify the gains in boot speed?
Comment: @Sandy Agreed, since it looks like I am one of those n00bs :). Fixed
Comment: This answer was true 15 years ago, but it's not really relevant these days. Most drivers come in modules anyway, so they only take room on the disk, not in memory. (Or do some distributions still come without initrd? Without an initrd the kernel does need to include all drivers it might need to boot.) As for boot time, the few drivers that spend more than a millisecond trying to detect nonexistent hardware can be disabled with a kernel boot option.
Comment: I think "considerably" faster is actually justified with the caveat that we are talking about boot times. The stock distro kernels take easily 5 - 10 seconds longer to boot up that one I have stripped down to not look for any hardware I don't plan on using. The run time speed is probably negligible, I can't actually measure that reliably.
Comment: @Michael if it's an unverified assumption, I think replacing "considerably faster" with "potentially faster" in your answer might be a good idea...just to make sure no n00bs are misled. :-)
Comment: +1 to Sandy's comment, I definitely agree with smaller, but not sure about it being significantly faster. I'd also like to see some data on this if you can provide it.
Comment: @Sandy I haven't actually measured it, but I assume telling the kernel which devices to support versus it needing to scan for devices has to be faster
Comment: Considering most of it sits in modules anyway...
Comment: One easy way to reduce drivers is to [to use the "dep" option in initramfs.conf](http://askubuntu.com/a/344252/370841). It'd be a good idea to keep the original around (or an entire older kernel) in case it doesn't work or you change something and forget to move it back first, though.
Answer: I can't believe the accepted answer here starts out saying "It's not something you need to do for more speed / memory / xxx whatever."
This is totally false.  I routinely custom build my Kernels to both remove unneeded code as well as including performance enhancing code mostly related to hardware.  For example, I run some older hardware and can eek out some performance gains by enabling rarely enabled Kernel drivers such as HPT36x chipset support on some older MoBos that have this built-in.
Another example, BIG SMP under Slackware is the default and on a Dell 2800, for example, will consume a sizeable foot print to run things like GFSD (not as a kernel module) that, also by the way, consumes CPU ticks for something I don't need.  Likewise for NFSD and other catch-all to please all mentalities which is fine if you're just trying to get a Linux on a box and running but if you do care about "speed / memory / xxx whatever" then these things matter and work.
All my production boxes are custom Kernels.  If I'm on common hardware such as a Dell series (2800, 2850, 2900, etc...) hardware, it's simple matter of copying the kernel's .config file around to each box and compiling the kernel and installing.
Comment: I think the main point of the accepted answer is that for most hardware, the performance gained by compiling your own kernel are not worth the time required to learn how to do it (and learn what the options mean). That is probably experiential: it would be great to find some numbers on this.
Comment: Well, it's not my fault my answer was accepted. And while yes there are cases where compiling your kernel will help you "eek out some performance" or get up and running on a low power machine, I made the assumption that the original question was being asked by someone who didn't have a specific need ahead of time, and was just curious in the general sense what the benefit of compiling a kernel was.  I would argue that only people with specific requirements in mind benefit from kernel tweaks.  Since my answer was accepted I'll improve it to address the more power-user reasons for custom kernels
Comment: well then that it's disingenuous to not state this in the original question and then accept the answer that is on the grounds you allege.
Answer: Here are some situations where compiling your own kernel will benefit you:

A kernel with module loading disabled is more secure.  This will require you to select the modules you know you need and include them as part of the kernel, as opposed to compiling them as modules.
Disabling support for /dev/kmem, or crippling it with the appropriate compiler option is a good thing for security.  I think most distros do this by default now.
I prefer not to use initrd's when possible.  Customizing your kernel to the hardware it boots from eliminates the initrd.
Sometimes a later kernel version will have features you need, but this is very rare today.  I remember when I first started using Debian, it was using 2.4 kernels, but I needed a 2.6 kernel for udev support.
Disabling networking protocols/options you don't need can speed up your TCP/IP performance.
Disabling options you don't need lowers the memory footprint of the kernel, which is important in low RAM environments.  When you are using a 256MB RAM system as a router, this helps.
I find all the "tty" devices in /dev annoying on systems where I generally only log in via serial or ssh.
Comment: All true. However, removing module loading can cause problems on boot: most, if not all, distributions today just assume that modules will need to be loaded. Last time I turned off modules, it caused a litany of error messages to pop out during the Red Hat boot process.
Answer: I second gabe.'s answer (my comment is too long so I'm posting as an answer).
Unless you have a highly specialized purpose (e.g. embedded machines, strict security profiling), I see no practical benefit to compiling your own kernel other than to see how it's done.  By methodically reviewing the options, seeing how they interact with each other to build the system is a great way to understand how your system works.  It's amazing what you find out when you try to remove components that don't appear to have any purpose for the tasks you're trying to accomplish.
Be warned however--why jumping down the rabbit hole is undoubtedly exhilarating, it will suck back more nights and weekends than you thought possible!
Answer: Compiling your own kernel allows you to participate in the kernel development process, whether that is simple stuff such as supplying PCI/USB device IDs for an existing driver that may make a newer device work for you, to getting deeply involved in the fray of core kernel development.
It also allows you to test development kernels on your hardware and provide feedback if you notice any regressions. This can be particularly helpful to you and others if you have an uncommon piece of hardware. If you wait for a distro kernel, it can take some time for fixes from your problem reports to filter into a new distro kernel release.
I also personally like to compile my own kernels to include support for only the hardware that I have. When you run distro kernels and look at the output of lsmod(8), you see lots of modules loaded for hardware you don't have. This can pollute the module list, /proc, /sys and your logs such that when you're searching for something it can get hidden amongst the noise; You also cannot be 100% sure that those modules are not contributing to a problem you are trying to diagnose.
Answer: At work, we use hand-rolled kernels in order to apply out-of-tree patches such as vserver and unionfs.
At home, I am compiling hand-rolled kernels in order to find which commit introduced a bug I am experiencing.   Once I've finished that, I will probably stick to a hand-rolled kernel until the bug is fixed in my distribution (Debian), at which point I would revert to their kernels again.
Answer: I'm surprised that no one mentioned this reason for compiling a custom kernel:
because you want to use a different C/c++ compiler. GCC is pretty good for compiling the linux kernel. But there are vastly superior compilers out there! GCC's optimizations are a bit behind Intel's C/C++ compiler. And Intel supplies the performance primitives libraries, and the vtune tool, both of which are indispensable in producing a high-performance linux kernel. You can only get so far with GCC and G++. Practically no matter what you do the result will be limited by the compiler. So, I use the Intel compiler and performance libraries  It's a bit big--1.5GB download, but that gives a bit of an idea of what is all contained in a good compiler.
Intel's C/C++ compiler is available free for noncommercial use. But it's easier to google the noncommercial license Intel c++ compiler download page that to search Intel's website. I don't usually use GCC/G++ for anything. And you don't need to be a programmer. You just set your environment and change two lines in the make file to point to Intel's compiler.
Then you can get some serious speed!
Answer: This thread is age old and yet still is valid today as it was when the question was asked!
The answer is: You compile the linux kernel of your choice as per your need and requirements.
Many scenarios are valid:

You are an engineer and requires your build to meet the performance and security requirements/demands for your system, you recompile to meet and/or surpass the specified criterias.
You are a normal user and have an old system that you want to keep going for as long as you can, you recompile to add/remove components to keep your old system optimised.
You are a normal user with the latest fastest hardware and it has more than enough memory/RAM. No need to recompile but you still can if you are interested in learning a bit more about your system.
You just want to be like a Microsoft and/or Mac everyday user, don't recompile and just go with the updates from your upstream distro.
Keep the scenarios coming :-)

Unlike Mac/Windows users, what Linux provides is choice. The choice to take it easy  or optimise the system to your requirements.
Answer: For most uses generic kernels are good for virtually any hardware. Additionally they usually contain(ed) distribution-specific patches so compiling your own kernel may (might) cause problems.
The reson to compile your own kernel are:

You are using source-based distro so there is no 'generic' kernel
You are kernel developer and you develop kernel
You must customize kernel for example for embedded device with very limited hard drive
Some driver is not compiled in (very rare case)
You want to patch kernel AND you know what you are doing
You want to learn how to compile kernel

If I wasn't using source-based distro I wouldn't compile kernel at all.
Answer: If you want to install Linux on very specific hardware, say more exotic than a DS, you will have to cross-compile your own kernel.
Answer: Another case besides the many mentioned here for having custom compiled kernels is setting up specialized network boot environments where module loading is not feasible and you have to pass out fully working kernels to specific machines for specific tasks.


Can I pray Tahiyyat al Masjid during the Quran recitation before Friday Azan?

Question: Al salam alaykum brothers. Yesterday I went to the mosque for Friday Prayer and arrived before the Adhan, during the Quran recitation. I didn't really look around looking to see if anyone else is praying. I prayed Tahiyyat Al Masjid and sat down. After the Adhan, 95% of the people in the masjid including almost all of those who were there before me, started praying two rakhas. Did they not pray Tahiyyet Al Masjid when they came in during the Quran? Or is there another Sunnah prayer that is done right after the Friday Prayer Adhan?
Comment: Quran recitation before jumu'ah is not a sunnah.
Comment: This needs clarification was this your first jumuah prayer in that mosque or ever? Are you sure they prayed only two raka'as and not four? Was there a second adhan afterwards?
Comment: It was my first Jumah before the adhan. I didn't notice how many raka'as honestly. There actually was a second adhan afterwards.
Answer: Some clarification
Note that during the time of the prophet () there was only one call for prayer (adhan) of jumu'ah. But during the time of 'Othman a second call was introduced which was held earlier than the first call with a time gap.
In some madhhabs it is allowed or even recommended to pray a sunnah (or nafl)  during this time gap. Some may pray therefore the sunnah ratibah (related to) dhohr (as the jumu'ah is usally held after noon which is the beginning of the time for the dhohr prayer). This means that you may find people praying during this time gap up to four raka'as (For details see How many Sunnah and Nafl rak'at one should offer in Jumuah salah according to all the 4 Imaams?). And I assume that they pray either a sunnah/nafl before jumu'ah prayer or the sunnah before dhohr.
Note that the sahabah () on Friday used to enter the mosque and pray whatever they were able to pray of nafl raka'a's and stop when the imam came out.
Reciting Qur'an (by one person while the rest listens) before jumu'ah is not reported to be a sunnah of the prophet () nor is holding a lesson as it is often practiced in mosques.
On praying tahiyyat al-masjid during a recitation of the Qur'an
So basically this recitation could be considered as bid'ah by some scholars, and we are asked to follow the sunnah which is offering a two raka'a prayer: the greeting/salutation of the mosque (tahiyyat al-masjid). As it is reported:

The Prophet (ﷺ) said, "If anyone of you enters a Mosque, he should not sit until he has offered a tworak` at prayer." (Sahih al-Bukhari)

When any one of you comes for the Friday (prayer) and the Imam comes out (from his apartment), (even then) should observe two rak'ahs (of prayer). (Sahih Muslim)

and many more ahadith on this matter, some even quoting the prophet () ordering somebody to perform it while he (the prophet()) is holding his junu'ah sermon!
Note even if you entered a mosque in a different situation for example for a lesson on tajweed or recitation of Qur'an and you found people or one of them reciting the Qur'an you should perform your two raka'as first and than join the recitation. As the mosque is a place for worship and meant for prayers in first place:

Say, [O Muhammad], "My Lord has ordered justice and that you maintain yourselves [in worship of Him] at every place [or time] of prostration(1), and invoke Him, sincere to Him in religion." Just as He originated you, you will return [to life] - (7:29)
(1) in Arabic al-Masaajid.

The mosques of Allah are only to be maintained by those who believe in Allah and the Last Day and establish prayer and give zakah and do not fear except Allah , for it is expected that those will be of the [rightly] guided. (9:18)

Sulaiman b. Buraida reported on the authority of his father that when the Messenger of Allah (ﷺ) had said prayer a man stood up and said:
  Who called for a red camel? (Upon this) the Messenger of Allah (ﷺ) said: May it not be restored to you! The mosques are built for what they are meant.
  (Sahih Muslim 1 & 2 and Sunan ibn Majah)

See also this fatwa on islamweb on what to do if one enters a mosque during Qur'an recitation islamweb #23858.
On the interpretation of the verse ordering to listen to the Qur'an recitation
As for the interpretation of verse (7:204)

So when the Qur'an is recited, then listen to it and pay attention that you may receive mercy.

as an order of listening to the Qur'an when it is recited, is interpreted by scholars according to two different views:
The hanafis say it is an order and it is general some (of the hanafis) consider it a fard 'ayn (fard on everybody listening) and others consider it fard kifya (fard to listen to it at least by some muslims) (for details on fard kifya refer to Can someone give me examples of fard kifaya?). Only the first view (fard 'ayn) is creating an issue here, but as explained if the matter really is a bid'ah your sin if listening might be bigger than the one of not listening to Qur'an while praying your two raka'a's. Also praying the two raka'as doesn't take significant time.
The second view -which is held by the majority of scholars- is that only ordered during the prayers and in any other situation it is mustahab and mandub (recommended)! For details refer to this fatwa on islamqa #88728.
The verse above is also considered as an order to do the opposite of the disbelievers who said:

And those who disbelieve say, "Do not listen to this Qur'an and speak noisily during [the recitation of] it that perhaps you will overcome." (41:26)

Like it is mentioned for example by ibn Kathir in his tafsir:

After Allah mentioned that this Qur'an is a clear evidence, guidance and mercy for mankind, He commanded that one listen to the Qur'an when it is recited, in respect and honor of the Qur'an. This is to the contrary of the practice of the pagans of Quraysh, who said,
  ("Listen not to this Qur'an, and make noise in the midst of its (recitation)'') ﴿41:26﴾. Ibn Jarir reported that Ibn Mas`ud said; "We would give Salams to each other during Salah. So the Ayah of Qur'an was revealed;
(When the Qur'an is recited, then listen to it.)  (Source qtafsir)

So what one should avoid during a recitation is speaking noisily or loudly and disturb the recitation, not praying his two raka'a tahiyyat al-Masjid.
Comment: Jazak Allah Khayran Medi1Saif for the information regarding the sunnah between the prayers and its history, as well as what to do during the Quran recitation and if it would be a sin to pray as per your final hadith and tafsir. I chose this as the correct answer because as one answer, it has everything a person in a similar position needs to know.
Answer: The Greetings of The Mosque prayer is different to the Sunnah volntary prayers of Zuhr. The Greetings of the Mosque prayer only stands when you enter a mosque:

Abu Qataadah (may Allah be pleased with him) said: The Prophet
  (blessings and peace of Allah be upon him) said: "When one of you
  enters the mosque, let him not sit down until he has prayed two
  rak'ahs." Narrated by al-Bukhaari, 1167; Muslim, 714

The below stands whether you are within a mosque or not, it is prefered to engage in such prayers at home and perform the obligatory in the mosque:

Al-Nasaa'i (1817) and al-Tirmidhi (428) narrated from Umm Habeebah
  (may Allaah be pleased with her) that the Prophet (peace and blessings
  of Allaah be upon him) said: "Whoever prays four (rak'ahs) before Zuhr
  and four after it, the Fire will not touch him."

In regards to the permissiveness or validity of praying voluntary prayers while Quran is being recited I am unaware of the legal ruling on this, especially in the context you mentioned.
Considering the below, it would seem that it is wrongful for the mosque to allow for the loud recitation prior to the commencement of the Friday sermon as this is a time when new arrivals such as yourself engage in voluntary prayer and recite Quran quietly; the loud recitation of other would be more of a distraction in my view.

"So, when the Qur'aan is recited, listen to it, and be silent that you
  may receive mercy" [al-A'raaf 7:204]

I am also unaware of whether this is an authentic practice or it is considered as an innovation.
As far as I know it is a strong Sunnah to offer Greetings prayers but it isn't to recite Quran loudly prior to the sermon, based on this I would just pray as soon as I arrive whether Quran is being recited or not, but I don't have complete knowledge on whether this is the best approach or not.
Comment: @Khaled I would arrive there whenever I can, I wouldn't let that affect me. The earlier you arrive the better, you get rewarded more that way.
Comment: @Khaled in my opinion yes, but don't take my word for it, I am only building a conclusion on the information I have.
Comment: This is very interesting to learn. I didn't count how many raka'as they prayed actually so as per the second hadith you poster, it might have been the four raka'as. Are the first four raka'as meant to be prayed after the adhan and before the second adhan?
Now about the Quran recitation, it's on the mosque's speaker, so I actually don't know what to do now given  the third hadith you posted.  Should I avoid coming before the adhan and come and pray during the khutba?
Comment: JAK for your help Aboudi. I would then have to arrive after the Quran recitation, right at the adhan time right?
Comment: And it would be okay if I pray during the Quran recitation?
Comment: No worries at all @Aboudi. Jazak Allah Khayran for your help with this. I will continue to pray during the recitation and will ask local sheikhs who are aware of the local practice of Quran recitation before Jumah adhan to make double sure.


Vertical alignment with horizontal widths dependent on eachother

Question: Seems like a simple, straightforward example that's kind of giving me fits. Here's an image of what I'm shooting for:

HEre's my HTML

            Products that matter

Mauris leo diam, convallis at rhoncus at, pellentesque ut turpis. Nullam orci velit, dignissim a suscipit et, adipiscing vel magna. Mauris leo diam.

And the CSS
.container {
    width: 1000px;
    margin-top: 50px;
}
.caption {
    background: rgba(255,255,255,.9);
    display: table;
    width: 100%;
    height: 66px;
}
.caption .label {
    display: table-cell;
    background: #94749c;
    color: #fff;
    font-size: 30px;
    line-height: 30px;
    font-weight: 400;
    width: auto;
    height: 66px;
    vertical-align: middle;
}
.caption .content {
    display: table-cell;
    width: auto;
    height: 66px;
    vertical-align: middle;
}

I think the best way of accomplishing this in pure CSS is with display: table and display table-cell. That way we can get appropriate vertical alignment. The problem is the widths. What I ultimately want is the purple cell to fit to the length of the text whereas the minor cell line breaks.
Here's a JSFiddle example.
The issue is that, depending on the length of the minor cell, it will push the primary cell in and cause a line break. Also, if you shorten the length of the second cell, the primary cell becomes much too large.
What I'd like to do, without javascript, is have the primary cell auto format its width without line breaking and then have the secondary cell fill in the space and line break as necessary.
Thoughts?
Answer: Well it seems that white-space: nowrap is the key.
That was easy.


Network error: Unable to reach the server WordPress/CiviCRM

Question: Running CiviCRM 5.11 plugin on WordPress. This is a fresh install on DigitalOcean.
In the WordPress Settings>General, there is a place to specify a URL, which I did using the URL for the website as registered in DNS.
When I first installed this, the setting used the IP address of the server, for example http://nnn.nn.nnn.nnn
With this setting, no problems.
After I was sure my DNS was pointing to this IP address and that it had propagated, I changed the setting to use the correct URL.
I can log in to WordPress okay but, when I click on the link to CiviCRM, I get a pop-up that says "Network Error: Unable to reach the server. Please refresh the page in your browser and try again. I do that and have to log in again.
All of the WordPress links are working fine. It only is a problem when I click on CiviCRM.
I changed it back to the IP address and CiviCRM works fine
Answer: Oops...I needed to make changes to civicrm.settings.php. All fixed


Can semicha be removed?

Question: Can semicha (rabbinic ordination) be removed today? If so, what is the criteria for removal?
slightly related
Comment: I'm pretty sure there's no universal standard for any aspect of what we call "semicha" nowadays.
Comment: If we view smicha today as an indicator not of moral character but of learning attained as evidenced by passing a test of some sort, one can not lose smicha. If smicha is tied to character then it an be revoked.
Comment: @Dan disagree, it can be an indication not only of learning attained but of the ability to adjudicate based on that knowledge. If a person demonstrates that their sense of judgement is impaired then it can be revoked even if they still possess all the knowledge. The same is true of passing the bar/being disbarred.
Comment: a lawyer doesn't adjudicate so questioning his judgment is a matter of assessing his following the canon of law, not applying rules well. A rabbi who gives patently inappropriate psak halacha might be demonstrating only an ignorance (through forgetfulness or issuing psak on an area in which he has no expertise) or a disregard for the rules. Are you saying that ignorance is grounds for losing smicha?
Answer: This question has already been discussed in the Hirhurim blog, in which R. Student argues that no matter how we understand contemporary semicha today, a rabbi's semicha can be revoked by the mentor who gave him semicha. As an example of this happening, R. Student cites R. Rakeffet's biography Bernard Revel, which describes how R. Revel [first president of Yeshiva College] revoked a particular student's semicha:

When a Yeshiva graduate refused Revel's request to leave a position which had both mixed pews and a mixed choir, his ordination was revoked. Revel wrote to a graduate on September 19, 1933: "It grieves me to inform you that since you refuse to leave Temple…where the sacred laws of traditional Judaism are violated, I urgently request that you return the conditional document of ordination that you received from the Yeshiva. The basic purpose of the Yeshiva is to guard the sanctity of Jewish Law in this land. If you will not return the document of ordination, I will be obligated to publish newspaper announcements declaring the nullification of your ordination." The rabbi did not heed Rabbi Revel's request, and the Yeshiva publicly announced the cancellation of his ordination and proclaimed that "one can no longer rely on his answers to inquiries of Jewish Law."

Furthermore, there are various institutions which have begun providing a disclaimer that they can revoke the semichot they give. Yeshivah Pirchei Shoshanim declares as much on their site:

It is at our discretion to block access and terminate either the course or revoke one's Smicha of any participant if they do not adhere entirely to all precepts of the TORAH and the teaching's of its Sages while maintaining the high level of personal and moral integrity that is demanded of one who is either learning for Semicha or has achieved that designation.

Similarly, after an Israeli rabbi admitted to stealing Torah scrolls, the Israeli Chief Rabbinate revoked his semicha, creating a new precedent:

Rabbinate representatives said that this is a precedent, and from now on this will be the policy towards any Rav who bears an official document and is convicted of offenses.
Regarding rabbis convicted in the past, the possibility is examined
  whether a certificate from the Chief Rabbinate will be denied them
  retroactively.
Hagr"y Metzger [Ashkenazi Chief Rabbi]: "The council wanted to send a
  message that a rabbi who transgresses does not only transgress a
  halachic, moral or value prohibition - but this may jeopardize his
  continued tenure and status as a rabbi in Israel."
In addition, a certain Rav accused of falsifying addresses and license
  to hold Chuppahs, was summoned to a hearing and it will be decided if
  he will be denied a certificate too.
Comment: Didn't Rav Solovechik also revoke s'micha of any of his students who took Conservative pulpits?
Comment: @BruceJames I would like to see a source for that
Answer: I'm pretty sure there's no universal standard for any aspect of what we call "semicha" nowadays. You'd have to ask each rabbi or institution that confers something with this name what their policies on removal are.
Comment: @ShmuelBrin Removing the entire premise of a question can be a valid answer.
Comment: Seems to be more like a comment

Can semicha be removed?


Firefox is configured to use a proxy server that is refusing connections

Question: I am new to the TOR browser, I have downloaded and installed it on my mac. When I open it up and go to search something, it comes up with "Firefox is configured to use a proxy server that is refusing connections." I have gone into the settings but I can't figure out how to get around this problem. I don't know a proxy to use.
Can someone help?
Answer: Your tor process seems to be in bootstrapping phase and it's "not ready to serve" yet, please attach a log to your answer. Just give it some time - it can be even 5-7 minutes for a first run.


Iota dollar balance not displayed

Question: I have not accessed my IOTA 2.5.7 light wallet in quite a few months, however I was finally able to get my full balance after a few attaches. I downloaded the Trinity Wallet (with Ledger) and transferred a few over to it from the light wallet. The amount shows up on Trinity but there is no dollar value. Also, I attempted to transfer a few back to the light wallet as a test using the ledger but get the message about NOT ENOUGH FUNDS to transfer, even when I attempt to send 1 Iota. Help!
Answer: Marcus, they have changed the API calls from IOTA to MIOTA. It's a known bug that will be fixed in the next update.
"Will be fixed in next version. Just an bug in the API for fetching chart information."
See discussion on Discord on the Trinity-Discussion channel.
Comment: Ok, although I am definitely NOT tech-savvy, what I am getting from your gracious response is that it is safe to transfer the rest of my (M)IOTA from the 2.5.7. wallet over to my newly downloaded Trinity Wallet (with Ledger) and once the Update (bug) is fixed, my actual dollar value will show up as well as the ability to transfer back out to say an Exchange if I wanted to sell a few.
p.s. even though the (M)IOTA shows up in the Trinity Wallet, my balance on the 2.5.7. still has not gone down...?!
Comment: Yes, the IOTA amount you see in your Trinity wallet is what you are interested in. In the next version of the wallet you should see the dollar amount as well.
Disclaimer: I'm not a Trinity wallet developer. I got the answer from Discord in the Trinity-Discussion channel.
Comment: Ok, I understand. Appreciate the responses.

Iota dollar balance not displayed


How does absence of nd orbital in Oxygen affect its valency?

Question: The original question was 'Oxygen exhibits Oxidation state -2 to +2 but other elements of grp 16 exhibit only +2,+4,+6. Explain Why'. In the solution given i can't understand meaning of this line 'It doesn't have nd-orbitals due to which its valency doesn't increase'. Please explain how?
PS:I am a chemistry noob. So please provide as much details as possible :)
Comment: I strongly advise you to acquire a copy of this article http://link.springer.com/article/10.1007%2FPL00010730 and ask your chemical teacher to comment on it.
Answer: Whether or not oxygen can reach oxidation states higher than $\mathrm{+II}$ is completely independent of the type of orbitals the second shell has. If the orbitals would matter, nitrogen would not be able to reach every single oxidation state between $\mathrm{-III}$ and $\mathrm{+V}$ but would also be restricted to <insert arbitrary number here>.
The actual reason why oxygen's accessible oxidation states are limited is its very high electronegativity, second only to fluorine among the non-noble gas elements. There is simply no partner that can draw away electrons strongly enough to access high oxidation states. Fluorine itself, while typically being able to access high coordination numbers (higher than oxygen, compare $\ce{XeF6, NF3}$ or $\ce{SF6}$ to $\ce{XeO4, NO3-}$ or $\ce{SO3}$) is not the element of choice for accessing high oxidation states — that is oxygen. But oxygen cannot oxidise itself since it has the same electronegativity. Fluorine itself, as is evident by $\ce{NF5}$ being unknown as of today, would not be able to stabilise an oxidation state of more than $\mathrm{+II}$ on oxygen given our current knowledge.
Furthermore, the statement's claim that group 16 elements except oxygen only exhibit positive oxidation states is bogus. $\ce{Na2S}$, $\ce{Na2Se}$, $\ce{Na2Te}$ and $\ce{Na2Po}$ are all known and in all of these compounds the chalcogen has an oxidation state of $\mathrm{-II}$.
Comment: While NF5 is still unknown, there was a report of possible NF6- anion and NF4+ is known for a long time. There's a theoretical study indicating possibility of analogous OF3+.
Answer: You need to review the concepts surrounding atomic shell structure and quantum numbers, and how they relate to the organization of the periodic table, I think.  Briefly, since oxygen is in the second row of the periodic table, we know that its valence electrons occupy the second orbital shell, corresponding to orbitals with principal quantum number $n=2$.  Recall also that for a given principal quantum number $n$, only sub-shells with orbital angular quantum number $l$ up to $n-1$ are allowed.  Therefore, the valence shell of osygen only includes s ($l=0$) and p ($l=1$) orbitals.  On the other hand, the other members of group 16 will by definition have higher principal quantum numbers, which means that their valence shells include d ($l=2$) orbitals.  It is these orbitals that can be used to rationalize the existence of higher oxidation states for those elements, for example by the $sp^3d$ and $sp^3d^2$ hybridization schemes in VSEPR (valence shell electron pair repulsion) theory.
Now, that explains why heavier elements in group 16 can have higher (i.e. more positive) oxidation numbers than +2.  Your question as stated appears to have an error however, since it says that those elements "exhibit only +2,+4,+6" ... that's not technically correct .. for example there are compounds where sulfur has an oxidation state of -2 (e.g. $H_2S$).  However I don't think it matters for the answer to your question here.
Comment: I know that Oxygen doesnt have d-orbital n other elements down the group have it but HOW exactly does that restricts oxygen OR say allows other elements to have more than +2 Oxidation State?


Terminal Server user settings not saving

Question: We are running a Terminal service server. When our users connect, and they change the default printer, when they log off and log back in, that setting wasn't saved and the previous printer is de default one again. Is this something in the profile that isn't saving on the server?
Answer: What's the default printer on their computer? In general (unless configured otherwise at the server or via GPO or on the user account properties) the default setting is to make the default printer on the client computer the default printer in the TS session.
Answer: Is the rest of the profile (e.g. filesystem objects added to the Desktop or "My Documents, settings for software like Microsoft office which is saved in the user's registry) being saved?
If so, you might either be facing some automated solution (probably a logon script) just resetting the default printer to some preconfigured device or have the option to use the client's default printer as default in the TS session enabled/not enabled, so the default printer gets reset on every connection.
Comment: This is the problem yes. We fixed it with a GPO setting to not set the redirected printer as the default printer.


Generating a PDF document based on a Microsoft Word Template

Question: I need to take a Word document that is a template of sorts...collect user input to populate specific fields in that template..then generate a PDF file that includes the completed template as well as a few other document types. Does anyone have a good suggestion on a component to achieve this? Preferably one that does not require Microsoft Office to be installed on the web server.
Answer: Try Aspose Words for .net. From their website: "Aspose.Words enables .NET and Java applications to read, modify and write Word® documents without utilizing Microsoft Word." Utilizing Aspose Words with Aspose PDF permits you to output to PDF.
One thing you do NOT want to do is install MS Word on your production server. Loading those objects is SLOW and EATS memory. You won't be able to use the CutePDF Writer unless you also install MS Word on the server. Yeck.
Answer: Is there a reason to use Word? If you start with a PDF with Form fields, you can either allow the user to fill out the fields, or do it programatically with iTextSharp's PDF stamper.
If you need to use MSOffice 2000/2003 components programmatically, you can try Office Web Components. They do need to be installed on the server, but can be used by .NET and Com apps to interact with office file types. More info here...http://en.wikipedia.org/wiki/Office_Web_Components
If you dig about on an office CD you should find the OWC installer for your version. I haven't worked with 2007, but I assume there is something similar available.
iTextSharp and OWC are no-cost, check the licensing for more details.
Comment: The only reason we'll be using Word is for the users' ease of use. These templates change on a some what regular basis, so they need to be able to change them and most of the users only have PDF Reader software installed.  Thanks for your advice though.  :-)
Answer: Hmmm...You might be able to employ CutePDF printer in a creative way to solve this problem.  Essentially, it takes anything that can be fed through a standard print driver and makes a PDF out of it.  It's free.
Comment: I am familiar with CutePDF since I use it personally to print many things to PDF. I've never thought about using it in a server environment. I'll definitely think about that.
Answer: Try using The Apache POI API to populate the fields. It can get into Word documents and access their elements.
As for the Word -> PDF step, I'd also recommend evaluating the Aspose solution. It may even be able to perform both steps. Its not free, however.
Answer: My first thought for a "doc template" + merge to pdf solution would be to start with open office formats. - the odt file (open document template) is xml-based - so you could even use perl, to do the merge, then call writer's doc 2 pdf (I have no idea if they have an API, but one could find out in less than a day - even if one had to examine the source.)
and converting your "word" dot to a writer odt file is just a "file save as" operation in OoWriter.
Answer: If you use Aspose.Words, then your input document/template can be in one of the several supported formats including DOC, DOCX.
Then you can insert data into the document in a number of ways. You can use bookmarks in a document and just set their text. Or better yet use the reporting engine we provide. It allows to use standard MS Word MERGEFIELD fields plus adds capabilities for repeating regions and even nested. E.g. you can design an invoice (with parent/child data) template in MS Word and then populate from a .NET DataSet in one line of code.
Also, you only need Aspose.Words to produce PDF (a year ago you needed both Aspose.Words and Aspose.Pdf). You can also easily save the exactly the same looking document to DOC, DOC, DOCX and a few other formats.
I'm on the Aspose.Words dev team.
Answer: Have a look at the Muhimbi PDF Converter Web Services. It runs on Windows as a service, but can be accessed from any non-Windows web services capable environment including Java and .NET.
Although this solutions requires MS-Office to be installed on a server (not necessarily the same server as your application), it is very robust and provides perfect conversion fidelity.
To generate or Modify MS-Word files I recommend using the free Open XML SDK for Microsoft Office. Eric White maintains a really good Blog about it.
Disclaimer, I worked on this product. Having said that, it works great.