Are Pablo Hidalgo's Tweets Canon?

Question: I sometimes see Wookieepedia articles citing Pablo Hidalgo's (a member of Lucasfilm Story Group) tweets. Are his tweets canon?
Comment: @DaaaahWhoosh - It used to say that (or words to that effect) on his twitter banner.
Comment: related, if not exactly a dupe: https://scifi.stackexchange.com/questions/910/how-is-canonicity-of-derivative-works-determined-for-star-wars
Comment: Not a dupe. It says that Lucasfilm Story Group Reps decide what canon is. It doesn't say anything about them adding to canon.
Comment: I've seen it mentioned on this site that his twitter account specifically says his tweets shouldn't be taken as canon, but I wasn't actually able to find such a statement.
Comment: @DaaaahWhoosh it was likely on meta
Comment: @Valorum - yes, I even quoted them in an answer (though don't have a screenshot yet)
Answer: Officially? No
It's worth reminding ourselves what "canon" means in the context of Star Wars:

@pablohidalgo Periodic reminder that all 'canon' means is: do other storytellers *need* to be beholden to it. That's it.

For the life of me, I cannot imagine Lucasfilm laying down an edict that requires future storytellers abide the exact words of Pablo Hidalgo's Twitter account. In other words, no matter how awesome she is, Millicent is not canon.
But it's still a useful resource
That being said, there's a reason Pablo Hidalgo is usually considered a "God" for the purposes of "Word-of-God". He holds a very privileged position with respect to the Star Wars canon, and has access to a vast quantity of material that the layfan will never see. So it's a little silly to disregard what he says out of hand.
Personally, I find it most useful - even if it's not technically correct - to consider (most of) Hidalgo's tweets as "canon until contradicted." The real value of his Twitter feed is that he can clarify the meanings of things that may not have been obvious; an advantage of his position. But at the same time, how do we know when something Pablo says is inviolate? Answer: we don't (usually; sometimes he's obviously joking1).
Hidalgo does try to make this easy for us: he almost never introduces wholly new ideas on Twitter, is frequently cagey when asked direct questions, isn't afraid to give generic responses like "that's not for me to say" or "not my call", and frequently reminds me people that major announcements aren't going to be made on Twitter of all places. Joking aside, I've never seen him deliberately mislead fans2; that's a large part of the reason why I, personally, feel comfortable citing him in answers here.
However, as non-insiders, we cannot rely on any of Hidalgo's statements not being contradicted by later works. Or by earlier works, for that matter. The ultimate source of "canon" is always going to be the published output.

1 Incidentally, this is why he really dislikes his tweets being cited on Wookieepedia
2 Whether or not somebody gets a joke is a different question, though Hidalgo usually tries to point out when someone has misinterpreted; if you have difficulty parsing his humour, it's worth reminding yourself of this fact when deciding whether or not something he said "counts" as canon.
Comment: It's also worth noting that not everybody considers "word of god" statements to be canon *at all*
Comment: Is there a page on Wookieepedia describing the process of how to use canon properly? And naturally, does it cite that tweet?
Comment: I upvoted your awesome answer, but i think Pablo himself saying his twitter is not canon is more canonical (is that meta-canon?)
Comment: @DVK-on-Ahch-To You mean like [this](https://twitter.com/pablohidalgo/status/887332603585593345) or [this](https://twitter.com/pablohidalgo/status/897256347628064768)? (Feel free to nick those, by the way). Nonsense. I refuse to believe Millicent and Ahsoka's pony farm aren't canon
Answer: I don't have a screenshot unfortunately, but as of December 2015, TFA release time, his Twitter account's blurb explicitly contained the text "Don't cite tweets as canon" (which I dutifully cited here in this answer). Here's more web evidence.

Also:

And just for an example:

Are Pablo Hidalgo's Tweets Canon?


Relating a sum to the standard deviation

Question: I have a summation that looks like
$$\sum_{j=0}^{n-1} S_j(v_{j} - \bar{v})$$
The $S_j$ terms all have values in $[0,1]$. $v_j$ is a data value and $\bar{v}$ is the mean of all $v_j$.
This expression is clearly related to the standard deviation. If $\sigma=0$ than all $v_j=\bar{v}$ so the result is $0$. But what I would like to do is relate the change in value of this expression to $\sigma$ for all values of $\sigma$. Is this possible? I have tried without luck but think that perhaps there is some property of $\sigma$ which I do not know which might help here?
Comment: In general no. You are right about the special case of zero SD and your sum, but SD is a root mean square and if it could be re-written as a weighted sum of deviations that would be public knowledge. I suspect at most there is an inequality lurking here, related say to Jensen's inequality, but don't bet on that and I am not the one to flesh that out even if it is true.
Comment: What causes the "change in value of this expression"? Are you contemplating changing the data, changing the $S_j$, or both?  @Nick is correct that there are some inequalities available, such as the Cauchy-Schwarz (apply it to the vectors $(S_j)$ and $(v_j-\bar{v})$), but they won't tell you much: consider the case where all but one of the $v_j$ are a constant $c$ and the last one equals $n\bar{v} - (n-1)c$.
Comment: Letting $S=(S_j)$ and $v=(v_j)$, your summation (call it $f$) is expressible as a dot product $S\cdot v - \bar{v}\sum S_j$. To learn about changes induced by changing the data, take the partial derivatives $\partial f/\partial v_j = S_j - \bar{S}$ and notice they have nothing to do with $\sigma$.
Comment: @whuber I meant changes in the data. I'd be interested in hearing more about any inequalities that may apply. I was hoping to find some bound on this expression in terms of $\sigma$.
Answer: Your original expression can be positive or negative.
Here is an upper bound in terms of the standard deviation, which is greater than or equal to the mean absolute deviation about the mean.
$$\sum_{j=0}^{n-1} S_j(v_{j} - \bar{v}) \le \frac12 \sum_{j=0}^{n-1} \left| v_{j} - \bar{v} \right|  = \frac{n}{2} {\displaystyle\sum_{j=0}^{n-1} \left| v_{j} - \bar{v} \right|}{ / n}  \le \frac{n}{2} \sqrt{{\displaystyle\sum_{j=0}^{n-1} \left( v_{j} - \bar{v} \right)^2}{ / n}} = \frac{n}{2} \sigma_v$$
To show this is tight, take the example of $v_0 = S_0 = 0$ and $v_1 = S_1=1$.
Comment: (+1) But note that your inequality is tight only for even $n$ and can be improved by accounting for the SD of the $S_j$.  (For instance, when all the $S_j$ are equal to one another, clearly the sum is $0$.)
Answer: An inequality
Let $S = (S_0 - \bar{S}, S_1- \bar{S}, \ldots, S_{n-1}- \bar{S})$ and $r = (v_0 - \bar{v}, v_1 - \bar{v}, \ldots, v_{n-1} - \bar{v})$ be the mean-centered $n$-vectors of coefficients and data.  Let $\sigma_v = ||r||_2/n$ be the standard deviation of the $v_j$. The Cauchy-Schwarz Inequality (which basically asserts the cosine of the angle between two vectors lies between $-1$ and $1$, reaching those extremes if and only if the vectors are parallel) implies
$$\sum_j S_j(v_j - \bar{v}) = \sum_j (S_j- \bar{S})(v_j - \bar{v}) = S \cdot r \le ||S||_2 ||r||_2 =   n ||S||_2 \sigma_v.$$
The first equality exploits the sum-to-zero property of the residuals $\sum_j (v_j-\bar{v}) = 0$, the second is the definition of the dot product, and the last follows from the definition of the standard deviation.  The inequality becomes an equality if and only if the vector $r$ is a multiple of the vector $S$.
Assuming all $S_j$ are either $0$ or $1$, this can further be simplified by writing $k$ for the number of nonzero $S_j$, for then $$||S||_2 = \frac{\sqrt{k(n-k)}}{n}.$$
Putting the two results together gives
$$\sum_j S_j(v_j - \bar{v}) \le \sqrt{k(n-k)}\sigma_v.$$
The right hand side is largest when $k=n/2$ or $k=(n-1)/2$ (depending on whether $n$ is even or odd, respectively); in either case the right hand side does not exceed $n/2$ times the standard deviation (and for odd $n$ it is strictly less).
Effects of changing the data
To determine the effect of changing the data $v_0, \ldots, v_{n-1}$ on $f(v_0, \ldots, v_{n-1})$ = $\sum_j S_j(v_j - \bar{v}),$ take the partial derivatives:
$$\frac{\partial f(v_0, \ldots, v_{n-1})}{\partial v_j} = S_j - \frac{1}{n}\sum_j S_j = S_j - \frac{k}{n}.$$
The gradient of $f$ is just the mean-centered vector $S$.  This does not involve the data at all, and particularly it's independent of their standard deviation $\sigma_v$.
When the $S_j$ can take other values in the interval $[0,1]$, all the results that do not involve $k$ continue to hold, which includes the two major ones: the implication of the C-S Inequality and the lack of dependence of the gradient of $f$ on $\sigma_v$.


Transferring favorites from Apple Maps to Google Maps

Question: Is there a way to transfer favorites (bookmarks) from Apple Maps to Google Maps? I understand why I can't, but has anyone found a workaround?
Answer: There is no way to synchronize Maps with Maps (so to speak), but you can sync Earth with Maps, with Google Earth being on the iPhone. If you log in to Google Earth, it will synchronize your maps. Those can be added from Google Maps on the web. Unfortunately, there's still no way to add stuff from an iPhone, but there isn't no connectivity between them.
Because I think that was a really messy and hard-to-understand answer, here's a clearer synopsis:

In the Maps app on the iPhone, there's no way to see things you've added on a computer.
In the Google Earth app on the iPhone, you can see "maps" (collections of pins) that you've created in Google Maps on a computer.
There's no way to add pins on an iPhone in either of these apps to later see on a computer.

I'm sorry there's no way to do what you want in a native Google app!


Was it common in Europe in the modern era that proper names were translated?

Question: My question is partially motivated by this question. I know that up until early 20th century in Hungarian many (or even most) foreign names were translated. For example this poster from 1864 mentions "Shakespeare Vilmos" (not William Shakespeare). The quotes in this work from a 1837 newspaper about the Texas Revolution mentions Moses Austin as Ásztin Mózes and his son (Stephen) as István. This translation habit was even a plot device in the novel Kőszívű ember fiai when the order came for Eugen von Baradlay, not Baradlay Jenő (although in this case the name was translated into German). I seem to recall that newspapers around the start of World War I still translated names of non-Hungarian politicians. Some translated names even survived into the 21th century (Jules Verne is still known as Verne Gyula, Karl May is still May Károly, Marx and Engels are known as Marx Károly and Engels Frigyes), but generally this habit died out sometime during the first half of the 20th century. Did other languages had similar habit? Did it die out around the same time?
Comment: T.E.D. but there is still a difference between turning یوسف into Yusuf and turning یوسف into Joseph.
Comment: Well, "Christopher Columbus" wasn't actually the dude's christened name. (Interestingly, we [don't actually know what that was](https://www.britannica.com/list/5-unbelievable-facts-about-christopher-columbus)) Its just the closest equivalent that sounds natural in English. And pretty much any Arabic or Chinese name you see rendered in Latin letters is some kind of approximation.
Comment: @Jan J historically sounded like Y so those would've been pretty similar
Comment: I think Christopher Columbus is one of the exceptions that remained translated even into the 21st century.
Comment: There is a famous Russian joke about the playwright Kopyetryasov and the physicist Odnokamushkin
Answer: It is still common in many European languages (including Hungarian, it seems) to change the order of names. E.g. in Japanese, Korean, Chinese, Hungarian the family name comes before the given name, but when reading Japanese or Hungarian names (but not Chinese or Korean ones!) in English texts, you will usually see the given name first.
One data point for Germany: if you search for "Jakob Watt" on Google Books, you get German publications from up to the 1850s, and he is almost exclusively referred to as "James Watt" afterwards
Translation of proper names was, however, reasonably common when Russian Germans migrated to Germany in the 1990s, e.g. from Yevgenii to Eugen, or Wladimir to Waldemar. But otherwise it has been rare for quite some time, e.g. you will not find serious publications with "Waldemar Lenin".
Anyway, one should not assume that people are terribly consistent about naming. That is why we have Peter (rather than Pyotr) the Great, but Ivan (rather than John) the Terrible.
Comment: Speaking of John the Terrible, there is a long-standing (and apparently still valid) tradition is to "convert" the names of British kings/queens in Russian – but not of anyone else. [Basically](https://ru.wikipedia.org/wiki/%D0%A1%D0%BF%D0%B8%D1%81%D0%BE%D0%BA_%D0%BC%D0%BE%D0%BD%D0%B0%D1%80%D1%85%D0%BE%D0%B2_%D0%91%D1%80%D0%B8%D1%82%D0%B0%D0%BD%D1%81%D0%BA%D0%B8%D1%85_%D0%BE%D1%81%D1%82%D1%80%D0%BE%D0%B2%D0%BE%D0%B2), king George is `Georg` / Георг, or king William is `Wilgelm` / Вильгельм (German "Wilhelm", yep). But prince Charles is Charles, no conversion here.
Comment: It was also common quite recently for Hungarians to translate their own names into foreign languages, e.g., papers of Erdős Pál in English were always by Paul Erdős. On the othe hand his younger collaborator Hajnal András never used the form Andrew as far as I know.
Comment: @Oleg, not just British; they are all germanised. France's Louis -> Людовик (Ludwig). Which is somewhat reasonable given that it stems from Frankish _Hludwig_, and the earliest of them must have called themselves that way. But this is not uncommon in English too (also for royalty): say, [Ferdinand of Spain](https://en.wikipedia.org/wiki/Ferdinand_VI_of_Spain) is not 'Fernando'.
Comment: I did search for Watt Jakab (the Hungarian version) and was surprised to see the name in this form in a [Hungarian lexicon](https://www.arcanum.com/en/online-kiadvanyok/Lexikonok-a-pallas-nagy-lexikona-2/w-1B649/watt-1B72A/) published in the 1890s. Apparently at that time it was still usual to translate the names.
Comment: @user2414208 Translating names like famous writers and poems, Verne, Pushkin, etc was very common in Hungary up to maybe mid 20th century. It is far less now, but even in the late 20th century, some names were used in the translated way.
Comment: The first half of the last paragraph "Anyway, one should not assume that people are terribly consistent about..." is possibly the single most important tool for understanding history that we have.
Answer: I did search for Watt Jakab (the Hungarian version) and was surprised to see the name in this form in a Hungarian lexicon published in the 1890s. Apparently at that time it was still usual to translate the names.
Then I searched for an early 20th century person - "Freud Zsigmond" and found an issue of the Nyugat magazine in 1925 published his memoirs. The neurologist's name was translated, but interestingly in the same issue the name of H.G. Wells was not translated (only misspelled).
This seems to be the theme in the 1920s - some names are translated, some are not, even in the same issue (e.g. an 1926 issue has a poem by "Wilde Oszkár" and a poem by Maxim Gorkij (only transliteration happened, no translation).
Answer: In Swedish some translated names like that can be found in older texts, like "Johanna d'Arc" in the 1800s who we later always use her native name Jeanne d'Arc for (in contrast to English where they still use their own version). I have Swedish editions by Alexandre Dumas from 1911 in Sweden where his name is given as "Alexander" on the title page.
Historical foreign monarchs are still written with established Swedish name forms when such exist, like "Ludvig XVI" for French Louis XVI or "Viktor Emanuel III" for Italian Vittorio Emanuele III), but newer ones keep their original names, so the current king of UK is "Charles III" in Sweden as well, and not "Karl III" (and there was a short debate about that in media last year).
I think many (in particular younger) Swedes think this practice is just strange when the original is in English, and they will prefer "William" and "George" over "Vilhelm" and "Georg" for such kings. When the original is a language they don't know it might be different ...


What are the major factions and players on the Magic and the Science side?

Question: There are various factions that exist on both the Magic and Science side, but what are the most prominent ones and who are their most well-known members?
Comment: This is tough to answer. Do you want to know only for the anime? Or also for the Novel? Also, the "major factions" switch from arc to arc. The only constant thing really is Touma (although the anime might make it seem like the Anglican Church is involved all the time, which is not the case).
Comment: I'd like as complete of a list as possible, just the anime is fine, but bonus points if you can include the light novel factions, too. By major factions I probably mean prevalent and currently active factions in the story, like the Board of Directors, Anglican and Roman Orthodox Church, ITEM, SCHOOL, and Skill Out.
Answer: Here is a generalized list of the people and faction in both the anime and manga continuity (including a bit from the light novels).
Magic Side
Roman Catholic Church

Matthai Reese, Pope
Biagio Busoni, Bishop
Ridovia Lorenzetti, Mardi Gras

# God's Right Seat

Fiamma of the Right
Acqua of the Back/William Orwell, Flere210 (Saint)
Vento of the Front
Terra of the Left

Russian Orthodox Church

Nikolai Tolstoy, Archbishop

# Annihilatus

Vasilisa, Head of Annihilatus
Sasha Kreutzev

Anglican Church

Laura Stewart, Archbishop
Orsola Aquinas

# The Church of Necessary Evil (Necessarius)

Kaori Kanzaki, Salvare000 (Saint)
Stiyl Magnus, Fortis931
Index Librorum Prohibitorum, Dedicatus545
Tsuchimikado Motoharu, Fallere825
Sherry Cromwell, Intimus115

# (Roman Catholic, London Branch) Agnese Forces

Agnese Sanctis, Leader
Angelene
Lucia

# Amakusa-Style Remix of Church

Kaori Kanzaki, Pontiff/Priestess
Tatemiya Saiji, Substitute Supreme Pontiff
Itsuwa
Uragami

Knights of England

"Knight Leader", Leader

British Royal Family

Elizard, Queen of England
Riméa, Princess of England (Oldest)
Carissa, Princess of England (Second-Oldest)
Villian, Princess of England (Youngest)
Silvia, Head Maid of the Royal Family (Saint)

Mercenarys

Oriana Thomson, Basis104

Science Side
Board of Directors

Aleister Crowley, General Superintendent
Kaizumi Tsugutoshi, Chairman
Oyafune Monaka, Chairwoman
Shiokishi, Chairman
Thomas Platinaburg, Chairman
Kumokawa Seria, Advisor

Hound Dog

Kihara Amata, Commander

Misaka Network

Misaka Imouto, Subject No. 10032
Last Order, Subject No. 20001

A Certain Magical High School

Kamijou Touma, Imagine Breaker (Level 0)
Himegami Aisa, Deep Blood (Gemstone)
Tsuchimikado Motoharu, Auto-Rebirth (Level 0)
Aogami Pierce
Tsukuyomi Komoe, Chemistry Teacher
Oyafune Suama, Math Teacher
Yomikawa Aiho, P.E. Teacher

Tokiwadai Middle School

Misaka Mikoto, Electromaster (Level 5 Esper, No. 3)
Shirai Kuroko, Teleporter (Level 4)
Shokuhou Misaki, The Queen of Tokiwadai, Mental Out (Level 5 Esper, No. 5)
Kongou Mitsuko, Aero Hand (Level 4)
Wannai Kinuho, Hydro Hand (Level 3)
Awatsuki Maaya, Float Dial (Level 3)

Sakugawa Middle School

Uiharu Kazari, Thermal Hand (Level 1)
Saten Ruiko, Aero Hand (Level 0)

SCHOOL

Kakine Teitoku, Dark Matter (Level 5 Esper, No. 2) (Awakened)
"Girl in the Dress", Measure Heart (Level ?)
"Boy with Goggles"

GROUP

Accelerator, Vector Change (Level 5 Esper, No. 1) (Awakened)
Tsuchimikado Motoharu
Musujime Awaki, Move Point (Level 4)
Etzali

ITEM

Mugino Shizuri, Meltdowner (Level 5 Esper, No. 4)
Takitsubo Rikou, AIM Stalker (Level 4)
Kinuhata Saiai, Offense Armor (Level 4)
Hamazura Shiage, Grunt, Chaffeur, and Informant

MEMBER

"Professor", Leader
Baba Yoshio
Xochitl
Saraku, Kill Point (Level ?)

BLOCK

Saku Tatsuhiko, Leader
Teshio Megumi

Judgement

Konori Mii, 177th Branch Office Chief, Clairvoyance (Level 3)
Shirai Kuroko
Uiharu Kazari

Skill Out

Hattori Hanzou, Leader (Temporary)

# Big Spider

Kurozuma Wataru, Founder, Former Leader
Hebitani Tsuguo, Second Leader

Anti-Skill

Yomikawa Aiho, Lieutenant, Branch 73
Tessou Tsuzuri
Saigou Ryouta

Kihara Family

Kihara Gensei
Therestina Kihara Lifeline, (Former) Captain of MAR
Kihara Amata, Leader of Hound Dog

Imaginary Number District

Kazakiri Hyouka, Counter Stop

Unaffiliated

Sogiita Gunha, Attack Crash (Level 5 Esper, No. 7) (Gemstone)

Other Side

Gabriel, Archangel
Aiwass, DRAGON


How to prove/disprove universality for a set of gates?

Question: A universal set of gates are able to mimic the operation of any other gate type, given enough gates. For example, a universal set of quantum gates are the Hadamard ( $H$ ), the $\pi/8$ phase shift ( $T$ ), and the $\mathrm{CNOT}$ gate. How would one disprove or prove universality of a set of gates such as $\{H,T\}$, $\{\mathrm{CNOT},T\}$, or $\{\mathrm{CNOT}, H\}$?
Answer: Universality can be a very subtle thing which is quite tricky to prove. There are usually two options for proving it:

show directly, using your chosen gates, how to construct any arbitrary unitary of arbitrary size (there's no constraint on the size of the construction, just that it can be done) to arbitrary accuracy (on some non-trivial sub space of the full Hilbert space).
show how your chosen set of gates can be used to recreate (to arbitrary accuracy) an existing universal set.

Conversely, if you wish to disprove it, you show that the effect of your set of gates can always be simulated by an (assumed) lesser model of computation, usually classical computation.
There are a few heuristics that you can use for guidance:

you must have a multi-qubit gate in your set. If all you have are single-qubit gates, you can simulate each qubit independently on a classical computer. So, if we believe that quantum computers are more powerful than classical, single qubit gates alone are not universal for quantum computation. This rules out {H,T}.
you must have a gate that creates superpositions. This rules out {CNOT, T}. Again, this is a classical computation with the addition of an irrelevant global phase.

Of course, these are not sufficient conditions: the set {H,S,CNOT} can be efficiently simulated as well (see Gottesman-Knill theorem). This must also be true of {H,CNOT} as they are a subset and so the operations that they can create is no more than those of the original set.
One of the universal sets that I find most interesting is {Toffoli,H}. It always feels surprising to me that this is enough (especially when you compare to the previous set). Note that it does not involve any complex numbers.
It is also possible to get universality from a single two-qubit gate such as
$$
\left(\begin{array}{cccc} 1 & 0 & 0 & 0 \\ 0 & 1 & 0 & 0 \\ 0 & 0 & \frac{1}{\sqrt{2}} & -\frac{1}{\sqrt{2}} \\ 0 & 0 & \frac{1}{\sqrt{2}} & \frac{1}{\sqrt{2}} \end{array}\right)
$$
Comment: Just pointing out that a lot of folks are used to thinking of universal as "can approximate any unitary with arbitrary accuracy." {Toffoli, H} fails to be universal in that sense because it can only approximate real gates. While the ability to approximate any unitary is sufficient for computational universality it is not necessary. And {Toffoli, H} shows exactly that. This is for example discussed in the wonderful comments  by Norbert Schuch here https://quantumcomputing.stackexchange.com/questions/1285/what-is-the-mathematical-justification-for-the-universality-of-the-universal-s?rq=1
Answer: Nielsen and Chuang, pg 191 of the 10th anniversary edition:

We have just shown that an arbitrary unitary matrix on a $d$-dimensional Hilbert space may be written as a product of two-level unitary matrices. Now we show that single qubit and CNOT gates together can be used to implement an arbitrary two-level unitary operation on the state space of $n$ qubits. Combining these results we see that single qubit and CNOT gates can be used to implement an arbitrary unitary operation on $n$ qubits and therefore are universal for quantum computation.

The first sentence there is an accepted result, so you must simply show that the combination of your gate set can implement "an arbitrary two-level unitary operation". To quote Wikipedia:

Technically, this is impossible since the number of possible quantum gates is uncountable, whereas the number of finite sequences from a finite set is countable. To solve this problem, we only require that any quantum operation can be approximated by a sequence of gates from this finite set.

See also this paper.


The electric field formula $E=F/q$

Question: If we follow the formula $E=F/q$ it says that when the force is bigger the electric field is bigger as well but if the charge on which the force is being exerted to bigger the electric field is somehow smaller? How does this make sense?
Answer: I'd say that you are looking at it backwards; it is better to imagine that eletric fields generate forces on charges. For a given eletric field, the bigger the charge, the greater the force; to produce an increase on the force exerted on a charge, the eletric field needs to be increased as well; so, for a given force, the greater the charge the smaller the eletrical field. It is analogous to mass in that different masses(A greater than B, say) subject to the same force will have different accelerations (B greater than A).
Answer: This is a great example of how causal understanding of physics is not manifestly obvious if you naively look at the mathematical expression.
What you say is true but is correctly formulated in the following way: for a given force $F$ on a charge $q$, the electric field $E$ (at the location of the charge) would have to get bigger as the charge $q$ gets smaller. In other words, what it says is that in order to produce the same amount of force on a smaller charge, you need a stronger electric field. As you can see, there is no mystery here at all when you understand it this way.
Of course, as you already understand (as implied by your question), the electric field acting on a charge doesn't change if you only change the test charge because it is determined by the external configuration of charges. Physically speaking, when you only vary the test charge, only the force acting on it will change. However, what $E\propto 1/q$ tells you is that if you want to maintain a constant force on a varying test charge, you'll need to vary the electric field in inverse proportion to the value of the test charge (via changing the external configuration of charges that produces the electric field).
Answer: If you, say, double the charge $q$, then you would naturally also see a doubled force $F$. Because for the field $E$, there would now be "double as much" charge to "pull" in.
But if you require the force to be the same, then you will have to reduce the field strength in some way. For example by changing the source that causes the field. Otherwise its impossible to change the charge and keep the force constant.
Your confusing may have arrived from the mistaken assumption that the force can be kept constant under normal, unrestricted circumstances. And thus, changing the charge would appear to change the field. Sure, this is mathematically possible - but not physically possible. Not without you actively changing the field in some way. Rather, it would be the field that is constant under such circumstances and the force would change when the charge changes.
Answer: I think you are confused by what $F$ and $q$ mean in the equation for the electric field:
$$E = \frac{F}{q} \tag 1$$
where $q$ is the test charge. The test charge is a charge of very small magnitude, so small that it does not affect the electric field but could be used to measure its strength. This is the definition from textbooks, now let's develop some intuition about electric field.

According to the Coulomb's law, the electric force between two charged particles is defined as:
$$\vec{F} = k \frac{q_1 q_2}{\vec{r}^2} \hat{r} \tag 2$$
where $k$ is a constant. Now assume that you have only one charged particle.  With only one charged particle there is no electrostatic force, i.e. there must be a second charge particle in order for force to exist. But we could define what that force would be in the presence of the second charged particle for every point in space:
$$\vec{E}(\vec{p}) = k \frac{q_1}{\vec{p}^2_\star} \hat{p}, \qquad \forall \vec{p} \in \Omega$$
where $\Omega$ is the set of all points. Now if you actually put the second charge particle $q_2$ at some position in space $\vec{p}_0$, the force between the two charged particles will be:
$$\vec{F} = q_2 \cdot \vec{E}(\vec{p}_0)$$
Note that the above equation is the same as the force defined in Eq. (2).
Having this in mind, how can we measure strength of an electric field? The idea is simple - bring a test charge at certain position in space, measure the force and then normalize the measured force, i.e. divide it by the test charge. This is exactly what Eq. (1) means!
Answer: The electric field definition uses E = F/q as you show, but you are missing the rest of the definition, namely that it is the ratio of F/q in the limit as q -> 0. This is done so that the test charge does not disturb the charge distribution that is creating the electric field.

The electric field formula $E=F/q$


A way for whole Calendar to show after swiping down in Iphone

Question: I want to see the whole calendar after swiping down. The part where the widgets are. Basically, when you swipe down, you can see the current date but when you try to click it, nothing happens. When you click the weather, the weather shows up so I was wondering if there is a way for the whole calnedar to show in the widgets page are.
Answer: If you have any events scheduled for today there's going to be a text in the Notification Center (when you swipe down) right under the current date saying "Your first meeting today...". Tap that and it'll bring up the Calendar.
If you don't have anything scheduled for today, you can scroll to the bottom of the Today view and tap the Tomorrow section instead.
Comment: Consider adding some additional details and/or screen caps to illustrate what you are answering here.  We are looking for more than a single line answer.


Can I deduct the cost of painting and replacing flooring after a renter moves out and we move in?

Question: We have been renting our retirement home out for several years.  The renters have moved out and we are moving in.  Can we deduct the cost of repainting and putting in new flooring?
Comment: Deduct it from taxes or security deposit?  What country are you in?
Answer: That depends on which country you are in.
In Australia it depend if it is for general wear and tear or if it needs replacing/repairing due to damage by the tenant. If it is due to general wear and tear, then no you cannot deduct it. If it is for damage and you can't use the money from the bond or insurance, then yes it will be deductible.
This answer may differ considerably in different countries due to different tax laws and rules.


When is a good time to have a betrayal?

Question: In my book a character who the main characters have saved before is revealed to be the real main antagonist. I originally wanted this reveal to happen at the end, but after looking at betrayals in most things, I found that they usually happen at the climax. But my question is: When is a good time to have a betrayal?
Comment: Isn't the end normally the climax?
Comment: @Chenmunka Usually not. The end is the denouement, that is, what comes after the climax. In more traditional narrative, after the climax, the hero returns home and find himself or his home changed. Think of the Hobbit's return to the shire and the recounting of what happens there and how Frodo eventually leaves for the elvish otherworld and what happens to Sam and Merry and Pippin after that – that's four chapters all taking place after the climactic battle of Minas Tirith.
Answer: It's the Roger Rabbit principle. Roger could only take his hand out of the handcuff when it was funny.
You can only reveal the betrayal when it is interesting. You can use it to drive whatever aspect of things you are doing. Raise tension or character development or fascination with the brave detective, etc.
You work out the plot and decide when it will hold your reader.  You work out when to reveal it to John, the betrayed person on the same rule. When will it hold your reader?
There are tons of ways to do it.
You can keep it all secret and have it be the Big Surprise at the end. Sherlock Holmes stories are often much like this. Though, of course, Holmes knew everything as soon as the client showed up at Baker Street.
It can be known to the reader very early, but the betrayed person much later. This can provide tension. When will John figure it out? What will he do when he does? Does he understand the clues you are dropping?
It can be known to everybody early except the reader. John has known for ages, and when the Big Reveal comes, John then drops his secret and demonstrates he has known all along. And the bad-guy is caught. Though don't go too far with that or people will be quoting lines from the end of the Bill and Ted movie.
It can even be known to everybody right from the start. The tension can arise from various intrigues and uncovering of evidence that allows proof. This is sometimes done in police procedural dramas. The valiant detective knows the facts but can't prove it  until the end.
In each case, the goal is to make the story interesting. Done well you get something fresh and interesting, even if it's a kind of betrayal story that has been done many many times before.
Comment: In short, the reveal should happen when it has the most impact on the dynamic of the narrative.
Answer: Personally what I would do is build up the relationship with the character that they're going to betray. It will add a whole new layer of betrayal if the readers actually have a connection with the character. This can happen whenever; if this book is just a one off I would have it in the climax, but if it was a series I would wait to it at the very end, and when the person is revealed have them escape or just cut it off right then and there to make the reader want to hear what happens next.
Answer: Boba Fit provides a really good answer.
But there are other times to do so. If you've seen the third episode of Star Wars, the clones turn on the Jedi at the most unexpected moment. You can also have a character commit a betrayal as punishment for insensitivity (which may not be an answer to your question, but I'm still thinking along the Star Wars theme).
Comment: I am aware of this. I am putting myself in the Jedi's(multiple similar characters) perspective.
Comment: "the clones randomly turn on the Jedi at the most unexpected moments" - it's only random and unexpected from the perspective of the Jedi themselves. To the viewer, it's neither random nor (entirely) unexpected.
Answer: Having recently watched Batman Begins, I liked the approach they took with Ra's al-Ghul. The movie introduced this nameless guy (played by Liam Neeson) who trained Bruce Wayne (played by Christian Bale) in multiple martial arts and helped him combat his fears and traumatic experiences. He really seemed like a good guy, while Ra's al-Ghul was a different guy who had motives of destroying Gotham City. When Bruce must kill a man to win the favor of al-Ghul, he refuses (as a classic Batman gesture) which leads into this whole fight where the temple gets burned. As the nameless trainer is about to die, Bruce saves his life and leaves, because Bruce valued the teachings he got from that man.
SPOILERS AHEAD:

That nameless guy was Ra's al-Ghul the whole time. That happens in the climax of the film, when Bruce realizes that the villain was not Dr. Crane but instead the guy he saved seven years before. The way the movie treats the reveal is a monologue, followed by evil actions, followed by a big fight scene where Bruce chooses not to save al-Ghul this time but instead let him die. This shows how Bruce let go of his memories from the training in order to serve Gotham, following the betrayal he got from his old trainer.

I hope this serves a good example as I think it is better to have the reveal before there is a final battle/fight/whatever. The character should have to face things and decide for themselves after the reveal, so both the protagonist and antagonist can have a resolution. Unless you want a cliffhanger for a next story, it's best to do something after the reveal to finish the story in a way that treats the betrayal properly and leads to a lesson learned (but not a sappy one, it should have some feeling or decision that impacts everything, like Batman letting al-Ghul die comparing to the way he saved him the last time that he was in that situation).

When is a good time to have a betrayal?


Issues Claiming A Business On Foursquare

Question: I am trying to claim my business on Foursquare, but when I try to do it by phone both my main local number and main 800# are not working... It's telling me it is unable to verify that phone number?? These are the MAIN phone numbers?? If I try to mail verification, I need to somehow get it mailed to my PO Box (Breckenridge does not have physical mail delivery - ONLY Po Boxes), but when I try to either change the address entirely to the PO Box or just add the PO Box and hit the verify button, nothing happens. I've hit the verify button no less than a dozen times... Nothing. Please help!
Comment: This question appears to be off-topic because it is in no way related to software development.
Answer: It sounds like you should file a ticket with Foursquare's support team:
http://support.foursquare.com/home
They should be able to help you!
Comment: Any chance finding ticket url


'unknown error' on renderStream

Question: I have successfully managed to utilize directshownet DirectShow wrapper for the purpose of generating thumbnails of video files. For many test instances the code works just fine.
However for some, it throws an 'unknown exception'  at the RenderStream function call.
I have been unable to trace the reson of the exception, the error code is '-2147467259', InnerException:null.
I do not have much experience with investigating faults in COM interface, but the error code does not seem to form any logical value.
My first thought was the lack of proper codecs etc. however the problem persists on a couple of test machines, where most of the popular codec-packs have been installed (ffdshow, k-lite codec packs etc). THe vido also plays just fine outside of the app.
The machines are running x64 versions of windows (windows 7 and win server 2008 r2),have installed
x64 versions of ffdshow codec packs, then played with other settings like installing 32bit version of ffdshow as well, coupled with compiling test app in x64 as well as in x86 build mode. Fails all the time on the sample clip. Also tried to enable/disable particular codecs in the FFDSHOW settings panel looking especially at the h264 one. Nothing.
The problematic sample video is encoded using the following specification:
v-codec:H264 - MPEG-4 AVC (part 10) avc1
Resolution:1280x768
FPS:23..
I think the code for building Graph is allright as it works for lots of test cases, however here it is:
 private void SetupGraph( string FileName)
 {
     int hr;

     // Get the graphbuilder object
     m_FilterGraph = new FilterGraph() as IFilterGraph2;

     // Get a ICaptureGraphBuilder2 to help build the graph
     ICaptureGraphBuilder2 icgb2 = new CaptureGraphBuilder2() as ICaptureGraphBuilder2;

     try
     {
         // Link the ICaptureGraphBuilder2 to the IFilterGraph2
         hr = icgb2.SetFiltergraph(m_FilterGraph);
         DsError.ThrowExceptionForHR(hr);

         // Add the filters necessary to render the file.  This function will
         // work with a number of different file types.
         IBaseFilter sourceFilter = null;

         hr = m_FilterGraph.AddSourceFilter(FileName, null, out sourceFilter);
         DsError.ThrowExceptionForHR(hr);

         // Get the SampleGrabber interface
         m_sampGrabber = (ISampleGrabber)new SampleGrabber();
         IBaseFilter baseGrabFlt = (IBaseFilter)m_sampGrabber;

         // Configure the Sample Grabber
         ConfigureSampleGrabber(m_sampGrabber);

         // Add it to the filter
         hr = m_FilterGraph.AddFilter(baseGrabFlt, "Ds.NET Grabber");
         DsError.ThrowExceptionForHR(hr);

         // Connect the pieces together, use the default renderer
         hr = icgb2.RenderStream(null, null, sourceFilter, baseGrabFlt, null);
         DsError.ThrowExceptionForHR(hr); // **HERE** is where the 'unknown exception' is thrown.

         // Now that the graph is built, read the dimensions of the bitmaps we'll be getting
         SaveSizeInfo(m_sampGrabber);

         // Configure the Video Window
         IVideoWindow videoWindow = m_FilterGraph as IVideoWindow;
         videoWindow.put_AutoShow(OABool.False);
         // ConfigureVideoWindow(videoWindow, hWin);
         //
         // Grab some other interfaces
         m_mediaEvent = m_FilterGraph as IMediaEvent;
         m_mediaCtrl = m_FilterGraph as IMediaControl;
         m_mediaSeeking = m_FilterGraph as IMediaSeeking;
         m_mediaSample = m_FilterGraph as IMediaSample;
         m_mediaPosition = m_FilterGraph as IMediaPosition;

     }
     catch
     { }
     finally
     {
         if (icgb2 != null)
         {
             Marshal.ReleaseComObject(icgb2);
             icgb2 = null;
         }
     }

 }

Still trying to narrow down the problem.
Any comments would be appreciated as I have simply runed out of ideas.
Update: Seems like the problem can be put more specific: how to modify the above graph in order to make DirecShow utlize h264 codec available on the system? It does not happen by itself from what it seems.
Another I believe worthy update: I have dived deeper into the subject of building grapsh etc. I have also downloaded the GrapStudio software in order to play with different filter settings. However, as soon as I choose the Render Media File submenu and point it to the problematic video it says 'cannot render file'! Nothing less, nothing more,the video file plays just fine in Windows media player, or VLC. It was encoded with h264video codec, provided by FFDSHOW.
Another Update:
I have managed to make GraphStudio render movie (File->Render MEdia File), with use of K-Lite codec pack x64. The graph is built (takes use of LAV Video Decoder). My app STILL fails to auto-generate a graph, though its targeted for x64 platform as well and from what I've read GraphStudio just calls the same API function. That is very strange. So I have decided to build a semi-automatic graph.
    Guid gui = new Guid("EE30215D-164F-4A92-A4EB-9D4C13390F9F");
Object o;
ty = Type.GetTypeFromCLSID(gui);
o = Activator.CreateInstance(ty, false);
IBaseFilter ibfVideoDec = (IBaseFilter)o;
hr=m_FilterGraph.AddFilter(ibfVideoDec, "LAV Video decoder");
DsError.ThrowExceptionForHR(hr);

While adding other filters which I need, followed by a call to RenderFile. NOTHING. All of the filters were initialized by their corresponding CLSID, no error there. It wont render.Anyone?
if you ask me that DirectShowNet or maybe DirectShow as whole is terribly documented when it comes to use of modern codecs etc.
Comment: Were you able to fix this issue? Just wondering
Answer: The error is 0x80004005 E_FAIL "Unspecified error". Graph builder forwards you the error from some internal component without providing you details. There is no way to find the reason without building the graph instead in finer steps. It can be anything including faulty third party components in the system (which is very likely provided that you installed codec packs one over another). Breaking RenderStream into individual Connects and AddFitlers will explain the cause.

'unknown error' on renderStream


Weedeater doesn't run very well w/ muffler on

Question: I know nothing about this kind of stuff.  But, when I started my weedeater, and put it on no choke (or even half choke), and gave it full throttle, it slowly died unless I let up on the throttle.  I understand I should use 100% gas, but I Have E10 in this tank.  I took the muffler off, and now it doesn't have this problem.  Is there such a thing as a clogged muffler?  How do I clean my muffler?
Answer: While I can't provide the technical details as to why, I would say your weedeater is performing as expected. With full choke and full throttle, you are flooding it when the muffler is attached. I would expect that you would smell or even see fuel coming out of the exhaust. However, with the muffler removed, the backpressure is so low that the engine can blow out more exhaust, so it continues to run, albeit with a different power curve (and lots more noise).
If you were experiencing power issues that are preventing the weedeater from performing its duties with the muffler on and choke off, then I would say there may be a problem.
However, for the sake of reducing noise pollution, I would encourage you to run your weedeater with the muffler installed.
Comment: Agreed that it is running as expected. I don't know what brand of weedeater it is, but the instructions on mine say to start it with full choke, let it run for a bit, then put it to half choke, let it run for another bit, then run it as normal. Not supposed to be on the throttle while you are applying the choke. After it's warmed up for about a minute is when you take the choke off completely and then you can throttle it.
Answer: What I did was I cleaned out the muffler with brake cleaner then blew it out with my air compressor (didn't really do much, I didn't see much carbon buildup come out).  I put the muffler back on, dumped out the E10 gas that I had in the tank, replaced it with 100% gas, and now it works.  Not sure which of these steps ultimately fixed it.
Answer: The spark arresters clog badly, some you can take apart, others you can't. If it doesn't come apart, you either clean it the best you can or replace the muffler. e10 doesn't have much to do with it.
Answer: Ethanol requires less oxygen than gasoline. E-whatever will run rich and the choke will make it run richer.  You don't mention 2-cycle or 4 cycle, but if the former the muffler is an important part of the scavenge system.  So you again change the mixture.
Mufflers running at full throttle tend to be rather hot and self-clean.


OS or Onboard software RAID?

Question: I plan on installing Debian 6 on my server build with a E3-1270, 16GB DDR3, and 2x120GB SATA3 SSDs.  But this has me wondering, should I use Intel's built-in, on-board software RAID or the OSs'?  Which will perform more efficiently?  Which is simpler? Please give me a solid answer. Thanks!
Comment: There's plenty of people with opinions of Intel's FakeRaid technology; they're pretty universally negative. See also http://serverfault.com/questions/9244/how-do-i-differentiate-fake-raid-from-real-raid
Comment: If you use HW RAID: keep a spare HW RAID card handy in case it dies (or a support contract). It you use fake RAID, keep a spare motherboard handy (preferably with the same BIOS). If you use software RAID keep a spare OS ready (but that is easy, just reinstall and look in your documentation for RAID config).
Comment: Maybe I'm the only person on the planet that's had a generally positive experience with Intel's fakeraid.  Then again, I only use it on *desktops* and then only in RAID 1 mode.  I'd never trust it on a server when there are much more *flexible* options available.  If you can't afford a real hardware RAID on your server, at least go software instead of fake.
Comment: Also consider http://serverfault.com/questions/214/raid-software-vs-hardware (Disclamer : I like the answers about software raid)
Answer: OS-based software RAID is more portable in the event of a hardware failure. Use that over motherboard-based fakeRAID. all things equal, use mdadm or ZFS over the motherboard.
Comment: I agree, the RAID provided by the OS have always been stable(my opinion) compared to the so called RAID found in motherboards.
Answer: Hardware RAID > Software RAID > fake RAID.
(Honestly, I prefer no RAID above fake RAID, but that's probably a matter of personal preference.)
Answer: They both work the same way. The only difference is who keeps the container information.
Comment: I don't agree.  Software RAID has been known to actually work from time to tine.  Seems like a difference worth noting.
Answer: I would suggest to find an Hardware RAID setup which is optimized for use with SSDs. AFAIK most SSD are RAID similar setups internal (connecting the modules in the frame and providing caching), which might perform slow on 'normal' (hardware or software) RAID controllers. Most (cheap) SSDs carry a JMicron controller, so perhaps you should focus on a decent hardware RAID controller for JMicron SSD devices, to improve life expectancy and read/write speed/caching on the RAID setup.
Unfortunately i've never reasearched this myself, but i know special SSD RAID setups exist..

OS or Onboard software RAID?


Problem in using float on Android

Question: I am going to develop a calculator on android platform, it is fine in calculating numbers less than 1000000, when I tried to add 1000000 with 0, the result is "1.0000E7"?!
I try to change the type of result from float to double, but the problem is still here, I try to use long, result becomes normal, but it cannot calculate decimal place anymore....
Comment: Please show as the code that is responsible for printing the result.
Answer: For your output use String.format(String format, Object... args)
and see Formatter for an overview on how to use the different placeholders/format specifiers (you will be especially interested in Floating-point conversions, ctrl-f it).
Answer: The calculation and the result are completely fine. 1.0000E7 is the correct result. See Scientific Notation for more information. If you don't want the number to be shown this way you have to change the way you create the output string out of your result.
Answer: The output just switched over to scientific notation. The solution is hidden in that part of your code that prints the result on the screen (widget).

Problem in using float on Android


in rails should i be installing as a gem or a plugin

Question: I am trying to use acts_as_audited plugin.  Should I be installing it as a gem (put it in environment.rb) or a plugin?
what is the advantage of one over the other. Later on I plan to put this app on the clients server for permanent hosting. so am I better off having it as a gem? if it is as a gem ...when i put the app on the clients server..will I not have to get this plugin again?
Answer: In general gems are a more robust and supported way to add functionality to your app. There's a whole infrastructure on the Web and built into Rails to work with gems that isn't there for plugins.
For example, if you use a gem you get the whole set of Rake tasks for dealing with gems.
In your project root, run...
$ rake -T gem

(in /Users/username/project/someproject)
rake gems                      # List the gems that this rails application depends on
rake gems:build                # Build any native extensions for unpacked gems
rake gems:build:force          # Force the build of all gems
rake gems:install              # Installs all required gems.
rake gems:refresh_specs        # Regenerate gem specifications in correct format.
rake gems:unpack               # Unpacks all required gems into vendor/gems.
rake gems:unpack:dependencies  # Unpacks all required gems and their dependencies into vendor/gems.
rake rails:freeze:gems         # Lock this application to the current gems (by unpacking them into vendor/rails)

You can also specify gem dependencies in your environment.rb file. That gives you the ability to automatically install them with...
$ rake gems install

Another advantage of gems over plugins is that on the system level you have the gem utility for maintaining gems so that makes things easier.

if it is as a gem ...when i put the
  app on the clients server..will I not
  have to get this plugin again?

You can "freeze" gems into your app and deploy them as part of the app without installing them on the system. If you do that you won't have to get the gem or the plugin again unless you want to upgrade it to a newer version.
Answer: As I understand it, the two behave quite different:

the plugin is only available for the application you are in. So if you would like to freeze it in your application, and want to simplify the delivery, use the plugin.
the gem is installed for the whole ruby installation. So it is better to share a gem between applications. However, you have to keep in mind that on delivery, you have to additionally install the gem on the client machine.

So in your case, I would prefer to use the plugin, not the gem.
Comment: Gems can easily be frozen into `vendor/gems`.
Answer: You may find it easier to debug a plugin vs. a gem. It's also nice if in your IDE you need to search for code that's within your app tree.
I find it's nice to install plugins for development and the transition to gems after the code is released.
Comment: With bundler it has become quite easy to debug a gem. Just open it by typing `$ bundle open gem_name`


what will happen if the motor that is designed for delta connected in star connection

Question: I have a motor which is designed for 3 phase, 380V. The power rating of motor is 132kw and motor stator winding is connected in delta connection. If I connect the same motor stator winding in star connection with same 380 V line voltage, what will be the impact on motor line current and power rating of the motor.
Comment: Is this homework?
Answer: When you connect it in a star configuration, the voltage across each of the stator windings will be reduced by \$\sqrt3\$ and correspondingly, the peak mechanical power that could be delivered to a load for a given slip and supply frequency will be lowered significantly.
So, for a comparable slip, the current and voltage will both be reduced by about \$\sqrt3\$ and hence the power delivered to a load is reduced by about 3.
Comment: On top of that, the PEAK torque capability of the motor is reduced by the SQUARE of the voltage reduction. So instead of having just 58% of the available peak torque, you will get 33%. Peak torque is what a motor uses to re-accelerate after a change in load, or to accelerate it from a dead stop. Reducing it by 2/3 usually results in stalling unless the load itself is reduced by that amount or more.


Smartwave porto cart icon need to change

Question: I have tried to change the code in _mincart_lesss but cart is not changed in website.Any one can help me on this?
Comment: You can contact PORTO theme support. They will help you.
Comment: not sure but I think you can modify it from porto settings panel
Comment: I have tried to change the cart using in background url in app/design/frontend/Smartwave_Access/porto/web/css/custom.css file [![enter image description here](https://i.stack.imgur.com/VBlFc.png)](https://i.stack.imgur.com/VBlFc.png) ANd i have tried to change the variable of the cart in app/design/frontend/Smartwave/porto/web/css/source/variable_less [![enter image description here](https://i.stack.imgur.com/3Rgdk.png)](https://i.stack.imgur.com/3Rgdk.png) This both case not working for me.Do you have any suggestion on this.
Comment: Should i run the below commend after done the changes,i just upload the modified file in FTP account and clear cache.Need a suggestion on this php bin/magento setup:upgrade
Answer: Try something like this in your .css:
.minicart-wrapper a.action.showcart::before {
    content: "whatever content you want, for example Font Awesome";
}
You can also use a background-image.
Here's how to include CSS in your theme: https://devdocs.magento.com/guides/v2.2/frontend-dev-guide/css-topics/css-themes.html
And more useful link :-
Magento 2: How to replace minicart icon
Hope this help you
Thanks...


How do I download and install Opera in 12.04?

Question: I've heard that we can use it. Then how can I install it because I dont see it in the Ubuntu Software Center.
Comment: my first reply, I know its a bit late but i thought it helps [Try this](http://www.noobslab.com/2013/04/install-opera-web-browser-in-ubuntu.html) It should work.
Answer:
To install Opera, simply go to their download page here. Ubuntu will be auto-detected, and click on the big Download Opera button:

Choose the "Open With" option, and the file will automatically open in Software Center once downloaded:

Click on Install in Software Center, enter your password if asked, and then Opera will be installed:
Answer: In terminal:
sudo sh -c 'echo "deb http://deb.opera.com/opera/ stable non-free" >> /etc/apt/sources.list.d/opera.list'
sudo sh -c 'wget -O - http://deb.opera.com/archive.key | apt-key add -'
sudo apt-get update && sudo apt-get install opera

Comment: I tried it and it doesnt work @zuberuber
Comment: OMG, i did it, and it does'nt open with ubuntu software center
Comment: and how i do it? i dont have experience @zuberuber
Comment: Thank's to izx and EliahKagan i corrected code and now it should work just fine.
Comment: when i write the second part it says "wget: invalid option -- '0' "gpg: no valid OpenPGP  data found."
Comment: worked like a charm in ``12.04``. Thanks
Answer: Detailed up-to-date  instructions are available here:

Opera Browser in
the Ubuntu Community Help Wiki
Can I install Opera from a
repository? in the Opera
Knowledge Base

Quoting the Opera Knowledge Base:

With Debian- and Ubuntu-based distros, you can use Opera's repository to ensure that your system will always have the latest stable Opera version.

You can also always get the latest version from http://www.opera.com/download/ but in that case you won't be using the native system tools (apt, aptitude, Ubuntu Software Center) to do updates.
Installing via repository is the recommended way to install Opera according to the Ubuntu Community Help Wiki.
Answer: Open the terminal.
wget -O - http://deb.opera.com/archive.key | apt-key add -

Then:
64 bit.
wget http://deb.opera.com/opera-stable/pool/non-free/o/opera-stable/opera-stable_42.0.2393.517_amd64.deb

sudo dpkg -i opera-stable_42.0.2393.517_amd64.deb

Replace "amd64.deb" with "i386.deb" if you work on 32 bit.


Is a 1:1 gear ratio the same regardless of the specific gear sizes?

Question: I have a gravel 1by bike with 42t and a 11-42 cassette. I also have a road bike with 50-34t and then 11-34 cassette. My question. When going uphill in easiest gear in both, they would both be a 1:1 ratio, but is one effectively an easier gear(i.e less effort) than the other because of the different number of teeth? cheers
Comment: @Michael For the same gear ratio, you're right, larger chainrings tend to be slightly more efficient but that's because the chain is under *less* tension. At the same cadence and speed, the power must be the same but the chain moves faster--so the force transferred through the chain (i.e., tension) is lower.
Comment: There could be some small differences in efficiency depending on the number of teeth, even with the same gear ratio and development. For example small cogs tend to be less efficient. Having a big chain angle is also bad for efficiency. I've read that riding in the big chainring tends to be slightly more efficient, maybe because the chain is under more tension and loses less power to vibrations.
Comment: Suggestion: Don't phrase the question oppositely in the title (are they the same?) versus in the body (are they different?). This makes it hard to write a clear "yes" or "no" answer.
Answer: No, both gears will be identical. The absolute number of teeth does not matter, only the ratio does. Both bikes have a lowest gear ratio of 1:1, so from the gearing alone both will be equally "hard".
However, since the gravel bike's tires are probably bigger, the distance traveled in one wheel rotation is longer than on the road bike. This means that even in identical gear ratios (e.g. both 1:1), the gravel bike will be slightly "harder", particularly considering that the gravel bike is probably heavier.
You can use a tool like the bike gear calculator to compare effective gearing while factoring in tire size differences. For example see this comparison assuming 28mm and 40mm tires.
Comment: Crank length will also make a difference
Comment: thanks for that, hadn't really considered tyre size.  cheers
Comment: Just to highlight from the comparison you've linked: On the road bike in the lowest gear at 90rpm you'd be going 11.6km/h, with the gravel bike you'd be going 12km/h. That's a 2.6% difference. If your total weight with the road bike is 77kg and with the gravel bike it's 79kg that would be another 2.6% difference.
Comment: Also, the gravel bike's tires may big bigger, in some cases that is offset by having a different size rim. My gravel bike has a 47mm tire on a 650B rim which by my calculations is very similar to a 28mm tire on a 700 rim.
Comment: At 2.6%, geometry, bike fit etc will probably l make a bigger difference than wheel size to perceived effort if not real effort.
Answer: As said previously, the ratio is the important metric, not the number of teeth. Tires (tread and pressure) can be a important differentiating factor between the two bikes. The gravel probably has larger tires, which impact the outer diameter (as explained) and the surface in contact with the road.
They are also meant to be run at different pressures. Road bikes inflated are typically at high pressure (>6bars), while gravel bikes should be inflated at much lower pressure (2.5bars-4bars). That alone has an impact on the rolling resistance.
Gravel tires also have (deeper) treads, which improve traction on loose surfaces, at the cost of rolling resistance on hard surfaces. The effect of rolling resistance is more felt in uphill than on flat terrain, because it adds to an already existing effort.
So with that, the road bike should be easier on hard surfaces, while the gravel will be easier on loose surfaces because of the additional grip.
Answer: Doesn't matter for easier pedaling, but matters for wear
Since nobody has mentioned it yet - with bigger gears,

the chain runs smoother as the gears are closer to circles,
the chain links have to bend for a smaller angle,
the force on the chain gets proportionally lower,

all effects that reduce wear. On the other hand, the chain travels over more teeth in the same amount of time, which might increase wear, but I'm pretty confident the wear-reducing effects dominate, and thus bigger = longer lifespan.
Comment: Larger rings also mean more teeth engaged, meaning that the force is spread over larger contact area, meaning less wear on the chainring and cog.
Comment: The biggest factor for wear is the teeth count. Notice how chainrings are usually made out of aluminium and still last ages while the small sprockets are always made out of steel or titanium.
Comment: @DoNuT The premise of the question is changing the size of both cogs proportionally to each other, so the chain line stays exactly the same.
Comment: Chain line should also be mentioned here (assuming #2 means cog radius). I'm not sure if it makes a huge difference in the compact road crank vs. 1x example in the initial question, but on typical (bigger) MTB gearing, you can run 1:1 in the middle of the cassette, close to the ideal chain line. However, with suitable gearing, you'll naturally spend only a fraction on extreme positions and most of it somewhere in the middle of the cassette.
Answer: Larger chain ring are slightly more efficient in transfer loses. But larger chainrings are heavier.
Comment: I remember reading somewhere, possibly *Bicycling Science* (MIT Press) or a quarterly journal that ceased publication a couple of decades ago, that for a given ratio, the combination with the larger number of teeth is marginally more efficient, but I cannot put my finger on it. But I suspect that the difference is less than other factors, like whether the chain is lubricated.
Comment: The chain doesn't need to bend as much with a larger chainring (as noted by MaxD's answer), which results in a more efficient drivetrain.
Answer: gear ratio is not the only factor affecting the force you apply on pedals on a given climb: put in account for pedal length and wheel radius !!
Comment: You're correct - there's a lot of other measurements that will vary between bikes, but OP's question is specific to whether 34:34 is effectively the same gear as 42:42.  As far as ratio goes, they are.


Sizing a fuse for a different voltage rating

Question: I'm wondering if it's possible to fit a 24VDC thermal protection fuse for a 48VDC battery system. I have a 60A solar charge controller connected to a 48V battery bank, and want to connect an inline fuse between them. By what factor should the amp rating of the 24V fuse be multiplied by in order to compensate for a doubling in voltage (24V to 48V)? Or is it not as simple as I imagine?
Comment: Current rating should be multiplied by 1. However if it's rated to break the circuit at 24VDC it may not be capable of breaking the circuit at 48V. leaving an arc where the fuse used to be, melting things and starting fire. Need I say it? I will anyway. Don't.
Comment: Be sure to verify that your controller does not need battery present and connected _before_ any S/A panel is connected! It is quite possible that it relies on battery for voltage stabilisation and with S/A power present but not battery it can be damaged. Also, fuse voltage rating should match maximum possible open circuit voltage, not battery nominal voltage.
Comment: Actually, _why_ do you want to fit a thermal fuse just between controller and battery? Which failure mode are you afraid of and want to prevent? If the controller is safety-certified, the best think to do, except you really know what are you doing, is to follow manufacturer/installation instructions exactly. (Then, if any fuse is recommended, exact specification should be followed.)
Comment: I want to prevent a fire if there is a short in the controller.
Answer: There is always good choice for a fuse for any sort of impedance or voltage.  The Charger ought to have some current protection, but this may be a good candidate in the fast-acting JLS series.
Comment: Littelfuse is a good brand. I think I'll go with their clamp down fuses, though ideally I'd like something resettable
Comment: @st4rgut: If you want something resetable, then you want a circuit breaker, rather than a fuse.  The circuit breaker must be rated for more than the normal circuit voltage (or more than the maximum voltage that will be across it when it is open).
Answer:
I want to prevent a fire if there is a short in the controller.

There are at least three "basic" failure modes which could under some circumstances lead to fire:

Battery charging regulation in controller stops to react properly and battery gets overcharged by available solar power.
Short circuit or other failure in the controller results in solar power being dissipated inside the controller as a heat. Depending on solar panel size, this can be significant amount of heat.
Failure in controller leads to power from battery flowing back into the controller and significant heat is dissipated in controller, battery or both.

(There is likely few more possible failure modes, but let's stay with these.)
From these three, the suggested fuse placement would protect only against #3, and only if failure is short circuit "hard" enough to pull many times nominal current (which does not need to be the case while still dangerous amount of heat is produced). On the other hand in case of hard short circuit, the fuse needs to have interrupting current capacity higher than battery bank short-circuit current (so likely big, thick fuses as other answer recommends).
Because controller will have some diode-like reverse current blocking circuit at output, you would need failure of at least two components inside to create such short-circuit. So presumably it is not the most probable failure.
Situation #1 could be prevented by internal battery protection if present, but otherwise you are relying on controller to be safe enough. Why do you trust it here and not for #3? (Which could be prevented by internal battery overcurrent protection too by the way). For failure #2 again, you rely on proper controller design.
Do you have a specific reason to trust safety of the controller for all failures expect just short circuit at the output?
Comment: I guess you are right. I contacted the controller manufacturer (MakeSkyBlue) who said the fuse's role is to protect the wire. I guess the controller has enough safeguards to protect against the situations you mentioned.


Be careful with CSS em units when taking advantage of rules of specificity?

Question: I'm having trouble writing maintainable CSS code when font size is specified with EM units as opposed to PX units.  I've been accustomed to writing CSS code like this:
body {font-size: 12px;}
body .sidebar {font-size:11px;}
body .sidebar .loadmore {font-size:10px;}
body .sidebar .warning {font-size:13px;}

The idea is that on many pages through out the site, there's a lot of text that should have 12 pixel font-size.  I take advantage of the rules of specificity to override the 12px font size in special areas of the site.
Let's say I rewrote the above code as:
body {font-size: 12em;}
body .sidebar {font-size:11em;}
body .sidebar .loadmore {font-size:10em;}
body .sidebar .warning {font-size:13em;}

If I replaced px with em in the code above, my understanding is that I lose the advantage of rules of specificity.  Line 3 of the code would be interpreted as " 10 em of 11 em of 12 em" which is not at all the same meaning as " override all previous rules and use 10 em of (what is the default?)".  Is what I've stated correct?
edit If what I've said is correct, then how does one write a font size rule such as "use font size X for all elements, but use font size Y on side bars"?
Comment: See my example http://jsfiddle.net/PJWrW/.  For the nested elements, use values that multiply to the desired size - for example, `1.1em` or `110%`.
Comment: @John Edits made to my original reply to reflect your own reply, but in short.  jnylen is pointing you down the right track with his/her use of the scaling factors.
Answer: John the specificity that you are talking about will occur in the way that you have stated.  A reference as to why can be seen: http://kyleschaeffer.com/best-practices/css-font-size-em-vs-px-vs-pt-vs/.
Edit As a reply to your edit please consider what jnylen posted in the comments of your original post.
A font size of 12 em as you have listed for body {font-size: 12em;} is going to scale the default font size to 12x it's current size.  If you would like to use em's you need to consider at what scale rate you wish to use them and do the math.  If you want to set fixed sizes with nested statements you need to stick to fixed attributes (pixels).  The advantage of em's as stated in the article that I linked is that you can set a default size, say 12 px and then use em to scale them.  For example in mobile based websites.
Answer: Yes, em values "multiply" together when the elements they apply to are nested.  It's not necessarily a specificity issue - if you specified the rules individually for .loadmore and .sidebar you would see the same issue, since .sidebar contains .loadmore.
Here's an example of a way to work with this:  http://jsfiddle.net/PJWrW/
I usually use either px or percentage units for font sizes, to make it explicit that I'm setting an absolute font size or modifying the parent font size.
I sometimes use em units for defining dimensions like paddings and widths, since an em unit is basically the width of a letter at the current font size.
Answer: As far as I know, if you're using em's for font size, there is no one way to set a standard font size for elements in a left hand side bar (or elsewhere for that matter) whilst setting the specific size of some elements in that side bar. If you use em's you'll have to specify the sizes of all elements in that side bar.
Personally I usually use px for font sizing, simply because you can set a standard font size for certain elements as you say in your post.
The only convincing arguments I have heard for using em over px regard scaling issues that are no longer really a problem (IE6 doesn't allow you to change font size manually if you use px but most people stopped hacking for IE6 a while back) The only real situation I can see using em as an advantage is if you want to implement functionality whereby the user can change the font size via JavaScript like here


Do the Bite of the X spells from Spell Compendium allow the target to cast spells and wield weapons?

Question: Spell Compendium has several "Bite of the X" spells, such as Bite of the Weretiger, that grant enhancement bonuses to physical attributes and give the caster natural attacks. Some include text such as Bite of the Weretiger's "Your hands become claws, granting you two claw attacks..."; does this prevent the caster from wielding weapons, or cause any issues gesturing for the somatic components of spells?
Comment: Welcome to RPG.SE! Take the [tour] if you haven't already, and check out the [help] for more guidance.
Answer: You can cast spells and - likely - use weapons, as per the normal rules of natural attacks
Casting spells requires gestures, but you can do that with appendages other than hands. Even creatures with distinctly non-hand appendages, like a dragon with its claws, can cast spells with somatic components. You do need the appendage to be free and able to gesture, as normal.
The ability to handle weapons is a bit more nebulous, because the spell doesn't specify the exact form of the claws. Most monsters with claws have "hand-like" claws - like the Troll's, for example, which can clearly handle items as a normal hand would. Many beasts have more animalistic claws that can't. Because all humanoid creatures that I know of get hand-like claws, for the rest of the answer I will assume that the Bite of the X-spells give you those as well. If not, you physically can't use weapons (or material components). Unfortunately, since the spell doesn't specify the exact form, the DM will have to make a ruling how exactly the claws work - the only discussion I've found on the matter is one without definitive sources as well, on GiantITP.
The bite and claw attacks are natural weapons, and follow the rules for them. That includes the following rule for manufactured weapons:

Some creatures combine attacks with natural and manufactured weapons when they make a full attack. When they do so, the manufactured weapon attack is considered the primary attack unless the creature's description indicates otherwise and any natural weapons the creature also uses are considered secondary natural attacks. These secondary attacks do not interfere with the primary attack as attacking with an off-hand weapon does, but they take the usual -5 penalty (or -2 with the Multiattack feat) for such attacks, even if the natural weapon used is normally the creature's primary natural weapon.

So the Bite and Claw attacks will be made at a -5 (or -2 if you have Multiattack, which some of the spells also grant). Your weapon attacks would work as normal, including iterative attacks. Of course, you can't attack with a claw that you're holding a weapon with, although you can attack with the "off-hand" claw if you're wielding a 1-handed weapon.
Answer: As it is written, I'd say you are good to go my friend. Bite of the Weretiger, as our example is written as (emphasis my own):

Your hands become claws, granting you two claw attacks, and your mouth becomes that of a tiger, giving you a bite attack. You can attack with both claws at your full base
  attack bonus, but your bite attack takes a —2 penalty (as if you had
  the Multiattack feat).

The spells specifically says you can use the claw and bite attack, but it doesn't say you can't use your claw/hand to wield your weapon instead. The spell also states:

If your base attack bonus is +6 or higher, you do not gain any additional attacks.

So, if your BAB is +6 or lower (unlikely as this is a level 5 Druid/6 Wizard spell), you would be granted an extra claw or bite attack. If the BAB is higher, you can attack with your normal amount of attacks, you just have more kinds of attacks to choose from.
This DM would rule that an appendage needs to choose if it will go natural or weapon attack, then if an appendage has already made its attacks (claw holding a sword), it is done for the round (it's been busy attacking with the sword). The other appendages, including the new bite attack can still be used though.
As for the spell affecting the somatic component for spellcasting, the spell doesn't say that it interferes, so I wouldn't assume it does, it is a high level spell after all. If your druid had the feat Natural Spell, this DM would be even more inclined to approve it.
Comment: The "If your base attack bonus is +6 or higher, you do not gain any additional attacks." is in reference to the rule that Natural Attacks don't get iterative attacks (which you would normally get at BAB +6). Basically, they're just natural attack and follow their general rules; that line is just a (clumsy) reminder of that.
Comment: Ahh, I was wondering at it as I was writing (why put that in there at all!?). Got it now. Also see this discussion on how manufactured and natural weapons work: https://rpg.stackexchange.com/questions/22047/how-do-multiple-attacks-with-natural-weapons-work
Answer: Another thing to consider is it is bite of the X. So one could assume bite of the weretiger would turn you into a weretiger.
The Monster manual page 175 under creating a lycanthrope -> attacks.

A lycanthrope in hybrid form gains two claw attacks and a bite attack as natural weapons. These weapons deal damage based on the hybrid forms size. A hybrid may attack with a weapon and a bite or may attack with its natural weapons.

The downside is, it also states that a hybrid form spellcaster can't cast spells with verbal components.
Comment: Welcome to the site! Take the [tour]. I think that this answer brings up something that the other answers haven't—namely that all of the *bite of the X* spells say that they change the caster's *mouth.* So while *somatic* components may be possible, *verbal* components remain up in the air. Consider answering the entire question then brining up this point, but bear in mind also that the question is (oddly?) unconcerned with verbal components. Anyway, thank you—sincerely—for trying to help strangers and have fun!


Heat transfer, Cold vs. Hot

Question: If you boil water inside a pot the outer rim bubbles first, I imagine because its hotter.  Does that same concept apply for the inside of a refrigerator for example.  Is the outer rim always more extreme, or at least at first?
Answer: When you are boiling water bubbles typically form first at the bottom of the pot, and then at the walls. As you guessed, this is because the bottom is usually at higher temperature than the walls, since it's in direct contact with the heat source. The reason that bubbles don't appear sooner in the bulk of the water is that nucleation (the initial formation of tiny bubbles) is easier at surfaces and at their irregularities. To check this, you can use any pot with a big scratch, and you'll see bubbles forming at the scratch first.
In a refrigerator, the conditions are quite different. In a typical refrigerator there's a coiled set of pipes inside the freezer, near the top of the unit. This is the evaporator, and it's where the heat is extracted, and this is where you'll have the lowest temperatures. If the leaks are small, you'll have the lowest temperature at the top and the highest temperature at the bottom. Usually, the back of the refrigerator is colder than the front because heat leaks mainly through the door crack.
Comment: `because heat leaks mainly through the door crack`--No, its because we keep opening the fridge every three seconds :P. Seriously though: Great answer, you may want to expand a bit on nucleation. Also there's the issue about heat transfer requiring a temperature gradient, which is another explanation for this (there is a T difference at the metal-water interface, but the water has a small T gradient)
Comment: does the cooling air leaves the cooling coil reaches a saturation point?discuss that,and how does that effect upon the the condensation flow rate at the evaporator?

Heat transfer, Cold vs. Hot


EE3 CP Overview page and removing the "ExpressionEngine News" block

Question: How does one remove certain blocks from the CP overview page particularly the "ExpressionEngine News" block.
Answer: it's in the member group settings:Show news on CP homepage
Comment: Thanks, but I can't find it. Super Admin is locked
Comment: yeah... you'll need to be a super admin to set that setting...
Comment: I am Super Admin and I can't edit setting for Super Admin. I suppose I can duplicate Super Admin and turn off news in the new group and then delete the original Super Admin.
Comment: Strange that the Super Admin group settings are lock even to the Super Admin
Comment: It's default behaviour. You can't change the settings for the SA group


International date line

Question: What if international date line being shifted to Atlas Ocean? Most of trade partners will have different date, States and all America continents will enter day first etc. So what can be coincidence of this? I am asking this because I have read that samoa was shifted to have better trade partnership with Australia.
Answer: The consequence would be confusion, if someone is further east of you it's natural to think they're ahead of time (relative to you).  Especially if you're used to the ubiquitous maps of the globe (with Europe/Africa in the middle, the Americas to the left and Japan/Oceania on the right).  Confusion then might arise in some economical contexts that are highly standardised.
For example, spot transactions on the forex markets are delivered (cleared) in 2 days.  If someone behind the date line trades on your behalf you might have to wait 3 days, or just one day for the funds to clear, depending on what side you're on.  Also in your example, think of recurring events (like quarterly reports, dividends, etc.), you might still be on the day before they're due but time-wise (just the hours on the clock) you're ahead.  Or if you're west of the date-line and waiting for events from someone east thereof you have to wait another day.
If the explanations above are confusing then that's exactly the point I'm making.  So, my opinion, if you wanted to pull off something like that without confusing people you'd also have to establish a new prevalent mapping of the globe, with Europe/Africa far to the "west" and the Americas on the far "east" side.  Of course, established terms, like far-east, western society, etc. have to be recoined as well.
Answer: The Pacific Ocean is the closest thing to "no man's... land, sea and air" that still remains in the globe today, while also crossing it "vertically", from pole to pole.
Also, it is vast: Countries "to the left" and "to the right" of the Atlantic Ocean are much closer than countries "to the left" and "to the right" of the Pacific Ocean. So the latter is more suitable to mimic changing days (and so also dates), compared to the former. It appears therefore a natural "neutral place" to have the International Date Line.
The case of Samoa, and other countries close to the Line is special (as is always the case when close to any boundary). To copy from Wikipedia's article on the International Date Line:

"The Samoan Islands, now divided into Samoa and American Samoa, were west of the IDL until 1892, when King Malietoa Laupepa was persuaded
  by American traders to adopt the American date, three hours behind
  California, to replace the former Asian date, four hours ahead of
  Japan. The change was made by repeating Monday 4 July 1892, American
  Independence Day.
In 2011, more than 119 years later, Samoa shifted back to west of the IDL by skipping Friday 30 December 2011. This changed the timezone
  from UTC−11 to UTC+13. The IDL now passes between Samoa and American
  Samoa, with American Samoa remaining aligned with the American date.
Samoa made the change because Australia and New Zealand have become its biggest trading partners, and also have large communities of
  expatriates. Being 21 hours behind made business difficult because
  having weekends on backward days meant only four days of the week were
  shared workdays."

The economy, always the economy... -which should drive home the point that the economy is not about "making money" but still mostly about transforming the environment ("producing") in order to survive (by "consuming").

International date line


Centralizing tikzpicture environment "inside" a minipage, both horizontally and vertically

Question: Honestly, I do not know if tex.stackexchange.com already exists a similar or exact answer to this question but I'll leave it here and if there is any solution already posted I'm waiting to be notified, grateful.
I have found a solution that for me I would classify as an alternative because of the fact that I can not understand why it worked. So I am posting this question below so I even respond to those who also need to be able to find it easily. So my solution below will already serve as MWE for this very issue.
Answer: I do not know exactly what caused me to get it but I did the following path:
Attempts to find solutions:
It did not work "but it helped to get the solution", grateful to them too: https://tex.stackexchange.com/a/446763/178949 and https://tex.stackexchange.com/a/446853/178949.
It worked (I am grateful to @Alexey Malistov) I needed to delete or not use the following commands: "\ vbox", "\ vsize to": https://tex.stackexchange.com/a/62493/178949.
I've tried to use \ begin {center} \ end {center}, or use \ vfill and \ vspace * {\ fill} along with \ hfill and \ hspace * {\ fil}, or just \ vfill along with \ hfill and still combined simultaneously or not with \ centering, but always the grid of lines ends up going out of the box \ fbox.
Using the whole solution, without changing anything, from @Alexey Malistov as quoted above, I got an approximation of the exact centering horizontally and vertically but continued to put the grid (or the tikz environment) far down. Then I guessed that this extra offset below the vertical and horizontal center of the minipage was happening by the use of \ vbox. So I deleted \ vbox, and got to an exact vertical centering. So I combined, encapsulating everything before, with \ hfil.
If I do
{\ hfil {{\ vfil {
\ begin {tikzpicture}
... command to draw the grid ...
\ end {tikzpicture}
} \ vfill} \ hfil}}

I do not know why but it did not work.
But using \ vfil and \ hfil in the order of the code below worked. I appreciate comments that help me understand why it worked.
I have taken a capture of Zathura PDF and soon perceive the accuracy of the position in relation to the whole page of the document and simultaneously the centralization of the drawing of the grid inside the minipage represented by the edges of the box of the command \fbox.

\documentclass{article}
\usepackage{fancybox,tikz}
\usepackage[paperwidth=35cm,paperheight=35cm,bottom=2cm,left=2cm]{geometry}
\thispagestyle{empty}
\begin{document}
\fbox{
            \begin{minipage}[t][25cm][t]{\linewidth}%
                    {\vfil{
                    {\hfil{\begin{tikzpicture}
                       \draw [draw, black,help lines] (-4,-1.5) grid  (5,9.6);
                    \end{tikzpicture}

                    }\hfil}\vfil}}

            \end{minipage}
            }
\end{document}

Answer: This answer makes the grid and saves it in a box (\mygrid), using \savebox.
\savebox{\mygrid}{\tikz{\draw[step=2.5mm] (-4,-1.5)  grid (5,9.6);}}

Saving the grid in a box, is equivalent to the OP's use of a minipage to get the grid into a box.
mygrid is placed in the middle of the page, the location of which is defined by a pair of orthogonal coordinates: (current page text area.north) and (current page text area.east). These page coordinates are created by loading the package tikzpagenodes.
The intersection of these coordinates is defined using |-. See the very good explanation here: TikZ: What EXACTLY does the the |- notation for arrows do?
 for the use of the |- syntax.
\node (center) at (current page text area.north |- current page text area.east) {\usebox{\mygrid}};

We can show this placement by adding some markers for the page coordinates and guides. First, a marker (coordinate ctpaN) is placed at (current page text area.north) using:
\node[circle,fill=blue,radius=4pt,label=above:{\Large current page text area.north}] (ctpaN) at (current page text area.north) {};

and a second marker (coordinate ctpaE) is placed at (current page text area.east) using
\node[circle,fill=blue,radius=4pt,label=above left:{\Large current page text area.east}]  (ctpaE) at (current page text area.east) {};

We then draw a line connecting the coordinates labelled (ctpaN) and (ctpaE). Again, we make use of the |- syntax to the draw line.
\draw[blue,thick] (ctpaN) |- (ctpaE);

The use of page coordinates can be adapted to placing content anywhere on a page. A second example is provided that uses partway calculations (TikZ manual section 4.2.1) to place example-image-a in the lower left section of the page.
This is a more generalized way of placing content compared to using \hfil and \vfil. Instead, we can precisely place content anywhere on a page, including in the header, footer and margins.
Another option for specific placement of content is using the textpos package.
\documentclass{article}
\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{calc}
\usepackage[showframe,paperwidth=35cm,paperheight=35cm,bottom=2cm,left=2cm]{geometry} % added showframe to show the margins
\usepackage{tikzpagenodes}
\thispagestyle{empty}
\newsavebox{\mygrid}
\savebox{\mygrid}{\tikz{\draw[step=2.5mm] (-4,-1.5) grid (5,9.6);}}
\begin{document}
\begin{tikzpicture}[remember picture,overlay]
% Place the grid
  \node[circle,fill=blue,radius=4pt,label=above:{\Large current page text area.north}] (ctpaN) at (current page text area.north) {};
  \node[circle,fill=blue,radius=4pt,label=above left:{\Large current page text area.east}]  (ctpaE) at (current page text area.east) {};
  \draw[blue,thick] (ctpaN) |- (ctpaE);
  \node (center) at (current page text area.north |- current page text area.east) {\usebox{\mygrid}};
% Place example-image-a uisng partway calculations. Load usetikzlibrary{calc}
  \node[circle,fill=red,radius=4pt] (ul) at ($(current page text area.north west)!0.25!(current page text area.north)$) {};
  \node[circle,fill=red,radius=4pt] (ll) at ($(current page text area.west)!0.75!(current page text area.south west)$) {};
  \draw[red,thick] (ul) |- (ll);
  \node (ull) at (ll -| ul) {\includegraphics[width=1.5cm]{example-image-a}};
\end{tikzpicture}
\end{document}

Comment: Diego. Hopefully it's clearer now.
Comment: Thanks for your reply Ross. It will help me understand the dynamics (interaction) between centering tools, drawing environments (eg: \ tikzpicture) and the resulting behavior within and minipage. Although you have not used minipage in your answer, I did the test and it really works.


Was the time temporarily stopped by Lord Krishna during Geeta upadesham?

Question: The narration of Geeta took place just when Arjuna refused to fight the battle and was becoming emotionally weak. How did it happen that everyone waited until the whole Geeta of 18 chapters was completed ?
Some people say that Krihna had stopped time while narrating it, If so then is there any reference for this in Geeta or Mahabharata?
Comment: Related [How much time did Sri Krishna take to preach Gita to Arjuna?](http://hinduism.stackexchange.com/q/9209/3500)
Comment: @MrGreenGold both armies were lined up and shankh was about to be blown. So you meant the conversation was without any pause or thinking/contemplating in between?
Comment: To put it simple from what i heard from bannaje govindacharya, There was pre agreed war formalities before the start of the war. The formalities are blowing of conch and saying akraman.. or something that army marches forward from both side, it its not done both army are supposed standin position till the commander of both army says akraman.. or go head.. even if 5 hours converstion the other army is not supposed to attack until both completes the formalities that was before the war actually started
Comment: In otherewords batter is ready to bat but bowler had to bowl inorder for the match actullly starts, that is why have slow over rate fine in circket match where the opposition delays onslaught by taking more time
Answer: Do you know that time(dream time) run faster in dreams, we can pass the whole day in our dream but in reality it might just be 10-15 minutes.
Remember we are talking about highly effective individual of that time, one Krishna and one Arjuna. Krishna is God himself and Arjuna is a person who have worked hard, studied, learned ashtras and shastras and they did lot of meditation and sadhana.
When you do these things, you became highly efficient, and these people have dedicated their life in these practices.
And time is a relative object, we might see time as only going positive direction, but these individuals have transcend the kala(time and space).
Now when you are that much accomplished, your interactions would be fast.
They are also capable to do telepathy, so transferring thoughts form mind to mind. So both of them can do 700 Sholokas what will appear to human as some seconds or might be minutes. Because in time of war, I am not sure if you can get more time than that.
And due to their high efficiency, it might seem to normal people as if time was stopped. Just try and do meditation for some days and you can feel what can be achieved.
Comment: Although, you could be right here, personal opinion answers are not allowed in  Hinduism SE!
Answer: Why? Gita has 701 verses, assuming 15 seconds for one verse it would be completed in 3 hours. In older days there was time required to prepare for war. So it can be assumed that they spoke for 3 to 4 hours during the armies prepared. Its like watching Bahubali movie before the war.
Comment: That does not make any sense. Arjuna was ready to go to battle his literally raised his bow so the armies were ready.
Comment: Does it take 3-4 h to prepare for battle?
Comment: @Wikash_ Yes there were literaly lakshs of people forming patterns and formations, setting up camps and getting your weapons ready. For eg say the war started at noon, they could have started talking from 9 o'clock.
Comment: @Wikash_ where does it say he was ready and he raised his bow?? Also even if that were to be true, Arjuna could have easily asked the others to wait for 3 hours
Answer: Based on the Book "महाभारत के कुछ रहस्य" by "(श्रृंगी ऋषि in Satyug) & कृष्ण दत्त in present life".
No the time temporarily did not and can not be stopped, it was just an conversation of 20 minutes before the war and no one can talk for near 700 shlokas we see in present Geeta.
So we should refer to the Geeta by "श्रृंगी ऋषि shringi rishi in Satyug) & कृष्ण दत्त (krishna dutt in Kalyug)", which only includes the 20 minutes conversation.
If you see only 100 years back there at that time also there were not as shalokas as we have today, so we should always seek towards the truth.
More over IMO the above incident given in the book sounds practical, No one is going to sit for both of them to talk for so long, Lord Krishna was a great persuasive and can convince any one
Comment: So you're saying Gita did not have 700 shlokas originally? If not 700, how many did it contain originally?
Comment: Shrungi rushi cannot write it in Satya yug. As Gita was told in dwapara yuga. What is the proof that it is written by Shrungi rushi? How is that authentic?
Comment: "If you see only 100 years back there at that time also there were not as shalokas as we have today, so we should always seek towards the truth." can you provide Sastra Pramana for this?
Comment: Why is this downvoted? This sounds very reasonable.


Did I input the correct ACWP, BCWS and BCWP values? [EVMS]

Question:
I know I performed the calculations correctly but I'm not confident about the 3 values in red
Comment: Why are you not confident that Microsoft Project is not calculating correctly?
Comment: This isn't a MS project problem - just simple EVMS in excel. I'm not sure if I interpreted the problem correctly.
Answer: Based on the Wikipedia page for BCWP, your BCWS number is probably wrong.
Unless the project has reached its deadline date (100% of projected time used) the BCWS column would not be 100% of the projected cost.
The BCWS column would have the % of the budget based on % of time. (As opposed to the BCWP column that has the % of the budget based on % of tasks completed)
As Wikipedia shows in the example provided:

To illustrate the difference between the three terms, assume that a schedule contains a task "Test hardware" estimated to run from 1 January to 10 January and to cost $1000, and that this is a simple effort with no overhead or allocated costs. However on 5 January, halfway through the time allowed, the work is 30% complete and has spent $250.
BCWP is $1000 (budgeted cost) times 30% (work performed), or $300
BCWS is $1000 (budgeted cost) times 50% (scheduled amount), or $500
ACWP is $250
Answer: Your BCWP and ACWP are correct, per the information you are providing.  It is unknown whether your BCWS is correct because "to date" is insufficient schedule information for anyone to make a determination.  If the project should have completed by "to date," then BCWS = BAC and is correct.  If "to date" means at some or any point before the scheduled finish date, then BCWS < BAC and is not correct.
To capture the correct BCWS, you need to calculate how much of the project, in dollars, should have been completed by the date you are taking a measurement.  Keep in mind that % in time is NOT the correct way of calculating BCWS because spend is not distributed evenly in most cases on a project.  That only works if your labor and material costs are literally the same value for every project work day.  There are cases when that's true but not in most.