PCB design for hand soldering exposed pad

Question: The (battery managing) IC I want to use has an exposed pad for thermal relief.  I am designing the PCB and want to hand solder the chip on the board.  I have read that you can drill VIAs to connect the exposed pad to a ground plane.  I would solder the pins (easy enough) and then solder through the VIAs to the ground pad.  Is this the best practice?
Comment: Been there, done that... and in retrospect, get yourself a hot air tool.   They are so cheap now (paid $35 for my to-go version), and solve not only this problem, but many others as well, such as mistakenly soldering an SMT part down unaligned.
Answer: For hand soldering chips like that with a metal pad I use a largish via. I solder the leads first after positioning the chip correctly, and then apply solder through the via with a large tip. The technique works very well.
Comment: would you say 4D/w ratio for largish hole D to wire ,w diameter ?  I think it also helps to spread the heat on a larger bottom side ground plane with 10cm^2/W with many heat pipe vias  (+1)
Comment: @ Leon, that's exactly what I have done in the past for proto hand soldering operations only. If the default via array is 25/12 then I would use one of those thermal vias (of the via array) w/a ~25 mil drill to feed the solder thru. Don't forget to clear the soldermask on that opposite side via/pad to get good thermal contact w/the solder iron.
Comment: I haven't tried this (because I have a hot air rework station), but my instinct is saying to pre-tin the chip pad to aid in creating a good joint. Could also imagine that making it difficult to solder leads first. Any voice of experience have some input there?
Answer: In addition to what others said....
Do not overlook the area for dissipating 2.5W of heat during full charge current and expect worse than best case 20Vin efficiency.
This means you need heat pipes or vias under IC heat pad to all layers for at least 6.25 sq in according to eval. PCB design which is consistent with my design standards for open air use in thermal resistance using >2.5W/sq.in
Enclosed , needs much more thermal  design effort.
 MCPCB is better with Alum, and Cu MCPCB is best.
Answer: Best practice would be a reflow process in a reflow oven. You could also achieve similar results with a electric iron or a hot air fan. I would not recommend soldering such a pad with a soldering Iron.
Comment: Or you could just put paste under the chip if there is no ground plane and let it reflow itself in operation.... ( just kidding)


What happened to the derelict spaceship after the events of Aliens?

Question: What happened to the derelict spaceship? Did it survive the explosion of the terraforming processors?
Answer: Your canon may vary.
In the Alien: Resurrection novelisation, we learn that the reactor explosion entirely vaporised the derelict ship.

It was too bad they didn't have more historical information. Gediman
considered it a scientific tragedy that they couldn't go back to
planet LV-426, where the Aliens were originally discovered by the
Nostromo crew. The wealth of information that must have been there!
But the derelict ship with its bizarre cargo of thousands of eggs had
been destroyed when the nuclear reactor of a damaged atmospheric
processor had exploded, leaving nothing behind but radioactive waste
and a crater nineteen megahectares in size. LV-426 would never be
habitable again.

As seen in Aliens: Colonial Marines, however, the derelict ship (codename: Origin) survived the explosion of the base at Hadley's Hope entirely unscathed because it was sitting behind a mountain.

Joshua Morris: "Quick status update on the derelict ship codenamed Origin. Interior is stable — cross-referencing the ship's current state with reports supplied by y'all, it looks like the Origin has been relatively untouched since the, what was it... USCSS Nostromo encountered it fifty-odd years ago. Hell, even most of the eggs are still intact. If I cared, I'd tell you suits that you're a bunch of exploitative dumbasses who are going to get yourselves, and a lot of innocent people killed. But since my shuttle leaves tomorrow and this little project has got me enough money to buy a small country, I'll just say: Good luck with all of that."
Comment: @user255577 - All signs point to it having survived. It's not in flyable condition though.
Comment: I would like to know if it survived the explosion, because if it did, then it is probable that it can still be flown, after destroying all the eggs inside of it of course. Perhaps human engineers can reverse engineer it and make space ships very similar to it.
Comment: @ Valorum okay, I'll take your word on it that it's not in flyable condition.
Answer: According to the Alien Resurrection novelisation it was destroyed when the Hadley AP exploded. The Weyland-Yutani Report said it wasn't a viable source of eggs post-explosion.
It also popped up in Aliens: Infestation (completely intact), the Earth War comics, the first AvP PC game, Alien Trilogy game, and other things I've probably missed.


Is it easier to attenuate a sine wave or a more complex wave?

Question: All other variables being equal, how does waveform complexity of a plane wave affect shielding effectiveness?  Is it easier to attenuate a sine wave or a complex waveform?
Comment: You should be more clear about what you mean when you say, "wave."  It sounds like you are asking about how to shield something from radio-frequency (RF) electromagnetic radiation (also known as, "radio waves").  Is that correct?  If so, then knowing roughly what frequency band the signal occupies will be more important than knowing the bandwidth/wave-shape/information content.
Comment: A sine wave has only one frequency. A complex waveform has many component frequencies that can extend far lower and far higher than that single frequency. A shielding effective for the single sine frequency might not be as effective at such extreme frequencies, so some part of the signal might slip in.
Comment: @james, yes, you're right.  I thought the tag "electromagnetic" and the term "shielding effectiveness" would have made that clear, but I'll consider adding clarification to my question.
Answer: In almost all cases, where linearity holds, it makes no difference.
You can analyse a complex waveform into a superposition of component sinewaves. An attenuator will reduce each, possibly by a different amount.
If the attenuator shifts the phases of the components, this may shift where the peak occurs, and so the ratio of peaks of output to input may be slightly different to the ratio of powers.
If your fields are so large the attenuator goes non-linear, then the complex waveform will likely send it non-linear at a lower power, as its peak to RMS ratio will be higher than that of a sinewave. Whether that means it attenuates more or less will depend on the detail of the non-linearity.
Comment: The question is about "shielding". Shielding is usually a set of conductive elements of various shapes and sizes, frequently with gaps and different grounding methods. Thus the shields may have resonances, and usually don't attenuate all things uniformly over wide frequency ranges.
Comment: @AliChen ... and a shield amplifies or attenuates a signal? 'Possibly by a different amount' === 'don't attenuate all things uniformly over wide frequency ranges'.
Comment: I am not sure what do you mean. My English is poor. If a shield has pieces hanging out of the size of 1/4 of some wavelength, it will amplify emission at that frequency. Or magnify susceptibility to external radiation...
Comment: @AliChen unless it's powered, so the shield is receiving power from some external source, it cannot add power to a signal. It may act as a transformer between a mismatched source and receiver to improve the matching and so power transfer. Normally when we talk about a shield, we assume that there aren't resonators engineered into it, which can be false if it has slots in it!
Comment: This is a philosophical topic. Yes, a shield can't add power to a signal. However, a specially-formed conductive elements can collect power from bigger area, and create fairly strong signals at specific isolated points. Especially if this point is connected to input of a RF amplifier. These arrangements are called "directional antennas", a horn in road radar detector is an example. And when we talk about shields, the reason of the talks is to avoid accidental engineering of resonator cavities and quarter-way receiving antennas. It looks like we are approaching the question from opposite ends.
Answer: Any "complex waveform" is a superposition of "sine waveforms". Therefore each "sine waveform" will be affected in accord with your shielding technique, and should be addressed individually. So yes, complex waveform needs more work.
Comment: @dcorsello, how broad is your "broadband signal"? If it is from 30 Mhz to 30 GHz, then you might need to pay close attention to possible gaps in your enclosure. And what choice of "materials" do you have in mind, other than copper foil?
Comment: in my application, the attenuator is a passive, ungrounded, sealed enclosure, which needs to attenuate a broadband signal.  So, in my case, I don't need additional attenuators to address multiple, individual frequencies. Rather, I need to choose a material that attenuates well across the entire bandwidth.
Comment: The frequencies are 1-1000 MHz.
Comment: @dcorsello, I took some look into your other questions. As I see you need a protection from a strong electromagnetic pulse, weapon-grade. AFAIK, copper doesn't shield magnetic fields much. To shield against magnetic field, you need magnetic materials with high permeability. http://www.magnetic-shield.com/pdf/magnetic_fields_shields_overview.pdf


How did German become the language of science?

Question: Recently, I read an interesting article about how English replaced German as the language in which scientists communicate. But how did German become the leading language in the first place? In the early years of what we could call modern science, around the time when Galileo worked, I would expect latin to dominate the scientific discussion. What happened that scientists switched to German?
Comment: Maybe you should write a definition of what "language of the science" is. Most articles written in that language? Then maybe it is Chinese. Most Nobel Prizes? Then Latin never was. If the definition is "the language one must know to perform scientific activities", I think the "metric" should be non-native scientists who must learn the language in order to keep doing science. And German never was it, except perhaps for Chemistry.
Comment: @SJuan76, one quick fix, most scientific articles published in china (and most of asia for that matter) are written in English, not in chinese.
Comment: My impression was that it was Göttingen that did it.
Comment: See: Jungnickel & McCormmach's [_Second Physicist: On the History of Theoretical Physics in Germany_](https://isidore.co/calibre/browse/book/5957) (2017).
Comment: To say 'X is/was _the_ language of science' is to say that there is/was no other: did you really mean that? -- because I'd say it is clearly not so: it's easy to find sources to show that at least since the 17th-c. there has always been more than one widely-used (arguably principal) language of science. Maybe you really meant to ask how did German become _one of the principal_ languages of science??
Comment: Related: Knowing language of Science in different times of history.
Answer: My impression is that German never was "THE language of science" in the same sense as English in now. After the switch from Latin to modern languages, there was no single dominating language of science. Up to the middle 20-s century there were at least 4 common languages
of science: French, German, English and Italian.
Let me state more precisely what I mean: French scientists wrote in French (not in German),
English/American wrote in English (not in German, not in French). And so on.
Scientists of other nations had an option: to write in their native language or in one
of these 4 "languages of science". For example Russians wrote in Russian, English, German and French.
This multilingual situation prevailed in Mathematics until 1970-s. Since the end of 70-s
very few Germans write mathematics in German. There are still many French mathematicians
writing in French, but a talk in French in an international conference is really rare.
But it is incorrect to say that German (or French) ever was THE "language of science".
Until 1970-s the Germans wrote in German, the English wrote in English and the French
wrote in French. These languages were "one of the languages of science" each.
EDIT. It seems to be true, however that in terms of VOLUME of published scientific works German was on the first place in the 19th and early 20th century. (I can confirm this by some statistics I made myself). But still English, French and Italian scientists wrote in their own languages. Nowadays the situation is very different: most scientists of any nation write in English.
Comment: I disagree that WWI ended that. German's role as the language of science declined only when Hitler came to power.
Comment: Actually, many French thesis in mathematics are now mixing English and French.
Comment: According to the article cited by the OP, German was the primary language of science in 1900, and World War I was the event that ended that.
Comment: It is WWII, not WWI that ended German's role as the language of science. Russian only publish their major works in Russian after mid 1930s. I don't think Chinese publish their major works in Chinese nowadays.
Comment: 5 "languages of science", not 4: you forgot (drumbeat ...) Russian. :-)
Comment: Russian was never an international language of science. It was the language of Russian/Soviet science (though I agree that publications in this language made a significant part of all publications). It is like Chinese nowadays.
Answer: One reason is geography: German is spoken in the middle of Europe and contains  - or is close to - many eminent academic cities. Germany was not a homogeneous country (like e.g. France) before 1871, but a collection of small dynastic states, which were culturally quite diverse. The protestant part of Germany had a strict work ethic and there was also a substantial Jewish population, all of which contributed to the development of mathematics and science.
The age of Enlightenment ('Aufklärung') and the romantic period played an important role in Germany and lead to a surge of interest in topics such as nature, philosophy, and also science and math. Traces of this period are still visible in the classical curriculum of some high schools ('humanistisches Gymnasium').
Finally, the German language is good at creating new composites: for example 'Eigenwert' (eigenvalue), 'Nullsummenspiel' (a game without favorable outcome), 'Gedankenexperiment' (thought experiment) and so on. This is a very convenient thing in scientific discourse, and many of these terms have been borrowed or translated into English.
Comment: @FranzLemmermeyer Euclid lived in Alexandria in Ptolemaic egypt in the 4th-3rd century before christ antiquity, which had similar geographic advantages as Germany did in the early modern era, being in the crossroads of major trading languages.
Comment: German was spoken in what is today Germany, in Austria-Hungary (there are many, many important Hungarian mathematicians who wrote in German, that being the language of upper class) and in large parts of Switzerland.
Comment: Besides Germany, German is also spoken in much of Switzerland, a country which is not irrelevant to scientific developments of the time.
Comment: You cite that the presence of a substantial jewish population as a contribution.  How did they contribute?
Comment: Well it's striking how strongly they contributed not only to science but culture in general: music, literature, chess, journalism... the names in HD22686's list illustrate this fact nicely by the way. The reason for this is probably worth a question on its own.
Comment: If geography is a reason, then why didn't Euclid write the elements in a Gothic language?
Answer: The change from Latin to German wasn't instantaneous. True, Galileo was one of the first to break the mold and write in his native language, but he used Italian, not German. Newton, too, used English (though, admittedly, also a lot of Latin). There doesn't appear to be a sudden shift to German around this time period. The change was gradual. As the article you mentioned says,

Then it [Latin] began to fracture. Latin became one of many languages in which science was done.

Why the change? I found that this put it best:

But researchers began to move away from Latin in the 17th century. Galileo, Newton, and others started writing papers in their native tongues in part to make their work more accessible and in part as a reaction to the Protestant Reformation and the declining influence of the Catholic Church.

After all, how many people in the 17th century were fluent in Latin?

I'd say that German became the language of science sometime in the late 19th century, growing until the late part of the early half of the 20th century. Physics exemplifies this. Look at this list of physicists:

Max Planck
Albert Einstein
Werner Heisenberg
Emmy Noether
Heinrich Hertz
Wilhelm Rontgen

There were also many Austrians in physics:

Erwin Schrodinger
Wolfgang Pauli
Ernst Mach

Also, Germany was strong in mathematics:

Bernhard Riemann
David Hilbert
Felix Klein
Hermann Weyl
Comment: Noether is more mathematician than physicist.
Comment: @2000 You can't ignore [Noether's theorem](http://en.wikipedia.org/wiki/Noether%27s_theorem).
Comment: Of course. But usually people knows she as an mathematician, like hilbert,poincare,riemann,gauss,... they have many worthy works in physics.
Comment: It's true but  you can't ignore [Noetherian ring](https://en.wikipedia.org/wiki/Noetherian_ring) and she's work in [commutative algebra](https://en.wikipedia.org/wiki/Emmy_Noether#Commutative_rings.2C_ideals.2C_and_modules) and [topology](https://en.wikipedia.org/wiki/Emmy_Noether#Contributions_to_topology) and she's [doctoral students](https://en.wikipedia.org/wiki/Emmy_Noether#List_of_doctoral_students)...
Comment: @2000 I know, I'm just saying that you can't treat her work in physics as negligible.
Answer: Related question: "What is the history of scientific Latin?" This answer to that question has a very nice quote by Gauss discussing his Latin:

From G. Waldo Dunnington's 2004 biography of Gauss, Carl Friedrich
  Gauss: Titan of Science, p. 37-8:

… Of unusual interest is the part which Meyerhoff⁶ took in this book [sc. Gauss's most important mathematical work: the Disquisitiones
    arithmeticæ]—the correction of the Latin.
⁶Johann Heinrich Jakob Meyerhoff (1770-1812) became in 1794 collaborator, and in 1802 director, of the gymnasium in Holzminden. He
    was thoroughly grounded and trained in the ancient and modern
    languages. As a Göttingen student he had won a golden prize medal for
    a Latin dissertationon the Phoenicians. Yet mathematics was rather
    foreign to him.
The above is striking enough, if one considers how little Gauss needed to mistrust his own proficiency in this respect. According to
    Moritz Cantor, Gauss wrote a classical Latin, giving rise to the
    expression that Cicero, if he could understand the mathematics of it,
    would have censured nothing in the Gaussian Latinity, except perhaps
    several customary incorrect modes of expression which Gauss used
    purposely. But it was Latin just the same and therefore attractive and
    stimulating to only a narrow circle of readers. Referring to
    Meyerhoff's work, Gauss wrote:

Of course I understand that it cannot be an especially attractive work for Mr. Meyerhoff, since he does not seem to be sufficiently
      acquainted with mathematics, in order to look on it just as reading.
      Thus the word algorithmus was unknown to him. Only on a single point
      must I take the liberty of disagreeing with him. I well know that si
      with the subjunctive is not good Latin; but modern mathematicians seem
      to have made for themselves the rule of constantly using the
      subjunctive in hypotheses and definitions; I do not remember an
      example of the opposite, and in Huyghens, who according to my
      notion writes the most elegant Latin and whom I purposely, therefore,
      have imitated, I find the subjunctive continually in these cases. I
      open at random and find Opera, p. 156, Quodsi fuerit; p. 157, Si
      sit, si fiat, si agitetur; p. 158, si suspendatur; pp. 188 seqq.
      are examples by the dozen. Therefore, since in this instance the
      desire to be a genuine Roman would be only purism (which as far as I
      am concerned would be less allowable, because I am well minded not to
      be so in any case) and the thing is not at all absurd in itself, I
      went with the current. I hope Mr. M. will not take offense at me. What
      was incomprehensible to him in the accedere possunt, p. 5, I have
      not been able able to guess; I have therefore let it stand. The
      passage p. 7, which previously ran thus: Si numeri decadice expressi
      figuræ singulæ sine respectu loci quem occupant addantur, Mr. M.
      misunderstood, because he probably didn't know that figuræ means
      numbers; he took numeri for the nominative plural and figuræ for
      the dative singular and on that account suggested to me that
      singulus is not wrong; but just for this reason a mathematician will probably not construe it incorrectly, chiefly because it doesn't make
      sense; nevertheless I have now arranged the words somewhat differently
      by this time.

Thus, Gauss seems to have worked with a mathematical Latin based on
  classical Latin. Gauss also wasn't afraid to innovate the Latin. It
  seemed to be a truly living language to him.
Gauss's Dictionary of Scientific Biography entry says:

He published in Latin not from internationalist sentiments but at the demands of his publishers.

Thus, it seems that the publishers played a role in phasing out Latin and thus allowing the adoption of German.
Wilhelm Weber, Gauss's student, never wrote any scientific Latin, to my knowledge. His famous works are in German.
Answer: A brief nubbin of an answer, but I think neglected by other answers: Bismarck's big centralized push to subsidize science and industry, in order to overtake Britain in such, in particular (and perhaps also France, et al).
This is similar to the U.S.'s NSF-and-other strong federal subsidization of "hard science" after WWII, both because "the bomb won the war" (not to mention crypto...), and to keep ahead of the main competitor, the Russians (who did acquire "the bomb", and, on top of everything, orbited Sputnick first, etc.)
So, at the very least, there was another "golden period" of U.S. mathematics, namely, post-WWII until perhaps the collapse of the former Soviet Union c. 1990. Well-funded, high-esteem. This tended to promote English as "the language of science" in and after that period...
Answer: German physics and the Journal "Poggendorff's Annalen" contributed to German becoming a scientific language in circa 1840s.
From Jungnickel & McCormmach's Second Physicist: On the History of Theoretical Physics in Germany (2017), "Chapter 6: Physics Research in "Poggendorff's Annalen" in the 1840s," "§6.1 Foreign Recognition of German Physics," pp. 137-8:

In an important respect, Poggendorff's Annalen in the middle of the nineteenth century was a different journal than the one he began editing twenty some years before. New foreign physics in translations and reports still had a prominent place in it, but the German physics appearing there was no longer in its shadow. The Annalen now regularly published work by German physicists that equaled, and occasionally surpassed, the best work by foreign physicists. At the same time, German work was gaining recognition abroad. This was a greater achievement than one might think, particularly in France. Humboldt had found in his many years abroad that the German language did not "flourish excessively in the great Babel," and that at the Institut de France "almost everything is lost that is sent in in German without excerpt and explanation."1 Even a paper by Gauss might get lost, the reason why Humboldt translated his paper on absolute measures before submitting it. The Journal de mathématiques pures et appliquées published no German mathematical physics at all in the early years following its founding by Joseph Liouville in 1836. Through the 1830s, the Comptes rendus and the Annales de chemie et physique together published only about a dozen papers on German physics. In the 1840s these journals added nearly a dozen new German names, mainly those of experimentalists though including the mathematical physicists Neumann and his student Kirchhoff. It was not until the 1850s that German physics came to be published in the Annales as copiously as foreign physics had long been published in the German Annalen. Twenty-five German physicists and well over 100 of their papers appeared in the Annales between 1850 and 1863, and German mathematical physics now received almost as much attention as German experimental physics. Experimentalists such as Magnus, Plücker, and Buff were represented by more papers than before, and the mathematical physicist Clausius appeared eight times and Kirchhoff thirteen. Liouville's Journal, however, continued to publish very little German mathematical physics: of the new physicists, only Clausius appeared there with a single paper on the mechanical theory of heat in 1855.2
In Britain in the 1830s and 1840s, German physics papers appeared very occasionally in the Philosophical Magazine and the Edinburgh New Philosophical Journal, but frequently in Taylor's Scientific Memoirs. The Memoirs published the work of experimentalists, Magnus again, H. W. Dove, and Hermann Knoblauch, and also a good many theoretical works. The volume for 1841 contained a translation of Ohm's 1827 theory, Galvanic Circuit, as well as of ten other, more recent German physics papers, mainly those by Gauss and Weber dealing with Earth magnetism. The volume for 1853 was devoted almost entirely to German work, including Helmholtz's memoir on the conservation of force and many papers by Clausius. This being the last volume of the Memoirs, from then on the Philosophical Magazine assumed the responsibility of frequently publishing German physics papers. By the 1850s the work of German physicists could be read in translation in Britain about as regularly as the work of British physicists could be read by German physicists in the Annalen.Notes

A. v. Humboldt to Gauss, 17 February 1833, in Alexander von Humboldt, Briefe zwischen A. v. Humboldt und Gauss. Zum hunderjährigen Geburtstage von Gauss am 30. April 1877, ed. Karl Bruhns (Leipzig, 1977), 23.

Our account of German physics in foreign publications is based on our survey of the journals mentioned. The work by German physicists appearing in the Comptes rendus of the Paris Academy of Sciences constituted a minute fraction of the journal's contents. The German physicists who published there in the 1840s were Dove (2 papers), Holtzmann (1), Kirchhoff (2), G. Karsten (1), Magnus (2), J. R. Mayer (3), Moser (2), Plücker (3), Poggendorff (2), Reich (2), and Wiedemann (1). In the 1840s Liouville's Journal published only three papers on mathematical physics by Germans: by Gauss (1) and Neumann (2). In the same decade, the Annales published papers by Buff (1), Dove (2), Magnus (3), Moser (1), Poggendorff (4), and A. Seebeck (1). In the subsequent period, 1850–63, the Annales published work by many more German physicists: Beer (2 and 1 with Plücker) Beetz (2), Buff (9 and 1 with Wöhler), Clausius (8), Dove (2), Eisenlohr (2), Hankel (1), Helmholtz (8 including some on physiology), Holtzmann (1), Kirchhoff (13), Knoblauch (6) R. Kohlrausch (3), Magnus (13), J. R. Mayer (1), J. Müller (2), Neumann (1), J. F. Pfaff (2), Plücker (8), Poggendorff (4), Quincke (7), Reich (3), Riess (6), Weber (1 with Kohlrausch), Wiedemann (11), and Wüllner (3); Gauss appeared with a paper on mathematical physics.

The survey of the Annalen for these years, on which the figures and discussions of the research published there are based, is our own. In 1840–1845, the ordinary professors of physics publishing in the Annalen were Buff (1 paper, 13 pages), Dove (8, 151), Fechner (6, 127), Magnus (4, 77), Moser (7, 143), J. Müller (1, 10), Muncke (1, 1), Neumann (1, 28), Osann (1, 25), C. H. Pfaff (4, 93), Pohl (1, 24), and Weber (5, 90). German physicists publishing there who later became ordinary professors were: Beetz (1, 18), Feilitzsch (3, 58), Hankel (6, 121), G. Karsten (2, 33), Kirchhoff (1, 18), Knoblauch (1, 12), Ohm (5, 98), and A. Seebeck (8, 169). Physicists at the Berlin Academy were: Poggendorff (18, 355) and Riess (10, 194).


Nonideal RF coupler model, admittance matrix in QUCS simulation

Question: I'm trying to simulate a nonideal directional coupler in QUCS. Unfortunately, the only model available is the ideal one without taking into account the isolation or insertion loss values.
Initially, I tried to model these effects with attenuators, but comparing the results from different simulators (which have the nonideal models) I can see some crucial differences in the final circuit attenuation plot. Probably my equivalent circuit is wrong.
Schematic of the circuit with my coupler model:

I'm starting to think that the right way to model the nonideal coupler is only by modifying the source code of the component. I already considered this, and the parameters are easily accessible. This is for example the admittance matrix for AC analysis:
<code>void coupler::initAC (void) {
  setVoltageSources (0);
  allocMatrixMNA ();
  nr_double_t k = getPropertyDouble ("k"); //coupling factor i.e. 0.707
  nr_double_t z = getPropertyDouble ("Z"); // reference impedance i.e. 50 Ohm
  nr_double_t p = deg2rad (getPropertyDouble ("phi")); //coupler phase shift i.e. 90 deg.
  nr_double_t b = 2 * std::sqrt (1 - k * k);
  nr_complex_t a = k * k * (qucs::polar (1.0, 2 * p) + 1.0);
  nr_complex_t c = qucs::polar (2 * k, p);
  nr_complex_t d = z * (a * a - c * c);
  nr_complex_t y;
  y = a * (2.0 - a) / d;
  setY (NODE_1, NODE_1, y); setY (NODE_2, NODE_2, y);
  setY (NODE_3, NODE_3, y); setY (NODE_4, NODE_4, y);
  y = -a * b / d;
  setY (NODE_1, NODE_2, y); setY (NODE_2, NODE_1, y);
  setY (NODE_3, NODE_4, y); setY (NODE_4, NODE_3, y);
  y = c * (a - 2.0) / d;
  setY (NODE_1, NODE_3, y); setY (NODE_3, NODE_1, y);
  setY (NODE_2, NODE_4, y); setY (NODE_4, NODE_2, y);
  y = b * c / d;
  setY (NODE_1, NODE_4, y); setY (NODE_4, NODE_1, y);
  setY (NODE_2, NODE_3, y); setY (NODE_3, NODE_2, y);
}
</code>
The problem is that I don't know which values to modify or what to add. I have not derived this admittance matrix and after searching the literature (Pozar) I couldn't find any example similar to this.
Do I really need to modify this admittance matrix (in AC and then S-params model) or there is a different equivalent circuit to model the nonideal isolation in coupler? If I really need to modify the matrix could You suggest some steps?
Edit:
The directional coupler in my circuit is discrete "Ultra Low Profile 0805
3 dB, 90° Hybrid Coupler" (https://cdn.ttm.com/repository/products/wireless-xinger/3db-hybrid-couplers/C2327J5003AHF/C2327J5003AHF_Datasheet(Rev_I).pdf)
I have revisited the Annaren site which was changed to TTM Technologies and found the S-parameter files to be easily accessible now (must have missed it before or something changed on the website) The S-parameter model is all I need. Before, I checked for the s4p file and didn't find it so I tried to model it with this nonideal discrete approach or by trying to modify the admittance matrix.
Answer: You have given us very little information about the coupler you are trying to model, apart from the fact that it is not ideal.  If you know enough about it to jump in and modify the y-matrix directly, you probably know enough about it to use one of QUCS standard models.
If you have measured parameters, then use a .s2p file for the four port.
If you know enough about it to generate a .s2p file, then that is probably easier than modifying the source.
Why can't you improve your model?  If it is a backward-wave coupler - use a pair of coupled transmission lines.  If it is a lumped element coupler - model it as it is. If it is a branch-line hybrid,  model it as it is,  etc..
Note - I'm not a QUCS user, but I'm sure that you can use the available features of the program to significantly improve your model.
Comment: Added some information in "Edit", I will use found S-parameters as they provide the most accurate model.


Is Underlining Available as a Markup Format

Question: Can text be formatted as underline?  If not, can this feature be added?
Comment: Underlining is the traditional way to indicate a hyperlink on the web, and so its use for any other kind of emphasis is a big no-no in user experience circles. Besides, underlining often substituted in earlier days for italic, bold, small-cap, and other formatting options that were not available on typewriters— a situation much-improved nowadays.
Comment: I wish there were. Or possibly some highlighter-like highlighting. People use italics, bold, and double-quotes to try to refer to strings of text that themselves might have italics, bold, or quotes. Yes, one can refer to a block of text by offsetting it as a block quotation. But there is currently no good way, that I know of, to highlight strings of text in context. (And, yes, if underlining or highlighting were added then the problem I mention would be raised for text that already has underlining or highlighting...;-) Still, it would be helpful, IMO.)
Comment: @choster Your point that underlining is used for hyperlinks is a good point.
Answer: There is no underlining markup for markdown. The  tag doesn't work either, so there is no way to underline on EL&U.
I cannot answer the other part of your question, as I'm not a Stack Exchange developer, but there is a meta meta question that covers it.
It essentially says, "no."
Comment: ..........            _Thanks!_


Battery drains in daily use

Question: my car battery goes flat weekly, even though my alternator output is constant 14.3 Volts. The  battery voltage does not drop during the night, however, it decreased significantly by afternoon, as if commuting would have drained it. Did you ever experience a similar issue, or do you have a suggestion as to what could be causing this?
Parasitic draw is 50 milliamps. Battery is couple of years old, but in good condition.
Comment: How did you determine your battery is in good condition? Yes, it's only a couple of years old but it doesn't mean it has gone bad. If, right after running the engine, you shut the car off, then turn the lights on for 10-20 seconds, turn them off ... what does is the battery voltage?
Comment: I could recently drive the car 30 miles with a manually (and properly) disconnected alternator. I presumed that qualifies, correct me if I'm wrong.
Comment: Okay, but can you actually test it as described above?
Answer: First off, take your battery and have it tested.  It's quite easy for even a relatively new battery to develop a problem where it's not able to output its full rated current or voltage when needed.
If the battery checks out, then your next likely culprit is the alternator/voltage regulator.  In most vehicles today, these two are integrated.
There are also shops that will test your alternator, make use of one of them.

Battery drains in daily use


Can I show a "Private & Confidential" job offer letter to a mentor for advice?

Question: I received a written job offer letter from a University in Australia. At the top of the letter it says "Private & Confidential". Can I show this letter to a mentor to ask advice about particular details in the offer? Does "Private & Confidential" mean no-one can read it without my permission? Or is it much stricter, to potentially protect the employer, meaning no-one other than myself and the employer can read it? Nowhere in the letter is the phrase further elaborated on.
Comment: Asking a single person, who is not associated with the institute, nor applying to the institute, in confidence for opinion on something in the offer is likely not a breach of private and confidential.  Posting that you have an offer from that institute on the internet likely is.
Answer: IANAL, but all job offer letters should be considered private and confidential, at least it means the following (confidential could mean much more, depending on the exact circumstances):

Private: do not put it anywhere where you personally do not have formal control over it (Obvious for a job offer)
Confidential: Strictly control the number of people you share this with, and take care that there are no conflicts of interest. i.e. do not share it with any of the following: Employees of competitors (no matter about your relationship to them), employees/Management of the company at which you apply (in case they have their own political stake in it).

I think the main function is to protect against competitors probing the salary.
Comment: What is your basis for defining confidential in that way? If I send you something and say "please keep this confidential", to me that simply means "don't share this with anyone." Of course, you might have a right to ignore my request.
Comment: Think of it like a medical lab result. These are also "private and confidential", but you're allowed (as the recipient) to share it with another doctor, but the doctor that sent it was not allowed to share it with others aside from you. Also, it allows legal action against anyone viewing it without your consent.
Comment: I would define confidential (excluding things which are confidential by a legal definition): Make sure that you share it only when needed for the purpose for which it is meant, in a way which keeps the private and confidential nature.
Answer: The meaning (and therefore strictness) of "Private & Confidential" can vary quite a lot and may well be organisation-specific so we can't give you a definite answer.
More often than not I'd interpret this as "Don't post this publicly, don't show this to other companies, don't scan this and post it on Glassdoor etc" and I wouldn't have thought showing it to a personal mentor (unless there were some conflict of interest) to be a problem. If you're concerned though you'd be best off asking the person who gave you the offer.


Access to image uploaded in article content type is denied

Question: when I attach an image to my article content type it doesn't show image. I mean when I creat an article content type and I upload an image to its using Image filed of article content type and publishe my article, the image not shown and when I right click to image and clicl "open in new tab" it goes to "Access Denied" page and says you don't have access to this image. this is true for my galley images too.
pleas help me :)
thanks
Answer: If you have uploaded an image as a private file it is not accessible by other users even if any user has access to the node. Please check "Upload destination" in image field settings.
Comment: no, my Upload destination is set to Public Files. in fact, there is no choice :) and it should be Public Files
in addition, I have a gallery that I made it myself. I have this problem there too. but only in gallery page that preview picture as gallery_thumbnail (a cutome view that I created)
in fact the original picture shown but the gallery_thumbnail picture not shown :(
Comment: Yes, it should be public to make it accessible to other users, but in fact there are two ways to store images (and other files) - private and public which you can see on the "Image" field setting and on every file itself.
Have you checked admin/structure/file-types/manage/image/display and admin/structure/file-types/manage/image/file-display?
Comment: in admin/structure/types/manage/gallery-image/display when I change the preview to for example thumbnail(100*100) and click Update, it changes but when I refresh the page it is None(original) again. :( I don't know why it never changs?! :(
Comment: please help me :(


Should I create my aragonOSx plugin manually or through the aragon SDK?

Question: It is unclear to me whether I should build a plugin using the Aragon SDK or if I should build my own smart contracts plugin manually and publish it to the aragonOSx protocol?
Answer: The SDK's current focus is in providing browser clients to interact with the DAO and with any plugins it may have installed. In future iterations, we may provide tools to ease the plugin publication process.
However, as of right now, plugins are built entirely using Solidity. Answer on how to do that is here: Do I need to submit pluginsRepo to the aragon repository or can I use any custom developed plugin from a personal reporegistry contract?
TLDR: every plugin consists of a Plugin.sol contract containing the plugin logic and a PluginSetup.sol contract containing the plugin installation instructions.
Then, in order to publish, you want to call the createPluginRepoWithFirstVersion function from the PluginRepoFactory.sol contract and pass it the address of your PluginSetup.sol contract. After that, you're done and your plugin is published for any Aragon DAO to use!


Why Oracle SQL Developer does not need Oracle client?

Question: I installed Oracle SQL Developer from Oracle's web page. It seems to work without a Oracle client installed on my computer. How is that possible? I also installed Toad for Oracle and it seems to require Oracle client.
Comment: I found an interesting article comparing the two.: https://www.thatjeffsmith.com/archive/2014/01/oracle-sql-developer-4-and-the-oracle-client/
Answer: SQL Developer is using the so called "thin driver".
For this the JDBC driver (a file named ojdbc6.jar) implements the complete Oracle network protocol which is usually handled by the Oracle client. It could use the another implementation: the "OCI" (or "thick") driver which would require an Oracle client to be installed. That would be necessary if e.g. Transparent Application Failover in a RAC is required.
This is not something specific to SQL Developer but to any Java application using JDBC to connect to the database.
Comment: @Dexter: https://docs.oracle.com/database/121/JJDBC/instclnt.htm#JJDBC28217 and https://docs.oracle.com/database/121/JJDBC/overvw.htm#JJDBC28036
Comment: Could you pls, list down cases when do we need oracle client. One is mentioned in the ans as when Transparent Application Failover in a RAC is required. Another cases?
Comment: @Destex Java JDBC standard for example does not support a way to tell you, that our password expired or is about to expire. You need to register thick, in order to change expired password via SQL Developer. Also thick driver provides much detailed error messages than thin one.


Symmetry of a spatial wavefunction independent of $M_L$?

Question: Consider the atomic wavefunction:
$$\newcommand{\p}[2]{\frac{\partial #1}{\partial #2}} \newcommand{\f}[2]{\frac{ #1}{ #2}} \newcommand{\l}[0]{\left(} \newcommand{\r}[0]{\right)} \newcommand{\mean}[1]{\langle #1 \rangle}\newcommand{\e}[0]{\varepsilon} \newcommand{\ket}[1]{\left|#1\right>} \ket{\psi}=\ket{L,M_L}\ket{S,M_S}$$
let us assume that $\ket{L,0}$  is has a certain symmetry on swapping electrons $i$ and $j$ such that the overall wavefunction $\ket{\psi}=\ket{L,0}\ket{S,M_S}$ is anti-symmetric then will the wavefunction $\ket{L,M_L}$ (for the same $L$) have the same symmetry on swapping electrons $i$ and $j$? i.e. if $\ket{L,0}\ket{S,M_S}$ is anti-symmetric is $\ket{L,M_L}\ket{S,M_S}$ always anti-symmetric for a given $L$, $S$ and $M_S$?
Answer: The symmetry does not depend on $M_L$.  The simplest way to see this is as follows.  Start with $\vert L,M_L\rangle$ as a product state.
If it is a product of only two states it would be written as
$$
\vert L M_L\rangle = \sum_{m_1m_2}C_{\ell m_1;\ell m_2}^{LM_L}
\vert \ell m_1\rangle \vert \ell m_2\rangle \tag{1}
$$
where $C_{\ell m_1,\ell m_2}^{LM_L}$ is a Clebsch-Gordan coefficient.  Permute particles $1$ and $2$, which is same as permuting $m_1$ and $m_2$ and you get
$$
C_{\ell m_2;\ell m_1}^{L M_L}=(-1)^{2\ell-L} C_{\ell m_1;\ell m_2}^{L M_L}
$$
showing that the phase $(-1)^{2\ell -L}$ and thus the symmetry character does not depend on $M_L$.
If you have more than two particles the job is a little more complicated.  Start with $\vert L,L\rangle$ as a product state, generalizing (1) to more than one constituent.  The coefficients in the linear combinations are no longer CGs but this doesn't matter for now.
From the state $\vert L,M_L\rangle$ you reach the state $\vert L,M_L-1\rangle$ by application of the lowering operator
$$
\hat L_-= \sum_i \hat L_{i,-}= \hat L_{1,-}+\hat L_{2,-}+\hat L_{3,-}\ldots
$$
Note that this sum is symmetric under permutation of particle numbers, so that, for instance:
\begin{align}
P_{12}\vert L,M_L-1\rangle &= P_{12}{\cal N}_{M_L}\left(\hat L_{1,-}+\hat L_{2,-}+\ldots \right)\vert L,M_L\rangle\, ,\\
&={\cal N}_{M_L}\left(\hat L_{1-}+\hat L_{2-}+\ldots\right)P_{12}\vert L,M_L\rangle
\end{align}
where ${\cal N}_{M_L}$ is a normalization constant.
This shows that the symmetry under permutation of $\vert L,M_L-1\rangle$ is that of $\vert L,M_L\rangle$, and independent of this $M_L$.


Do URLs submitted in a site map to reindex have the same priority as request indexing?

Question: Will Google position the URLs with same page rank in both cases?
Which is fast and good?
Will all URLs in the site map get indexed?
Comment: What do you mean by "request indexing"?   I've never heard of that before
Comment: "request indexing" - I assume you mean the the "Request indexing" option in GSC after having used the "Fetch as Google" tool. (?)
Answer: You have included few things in the question, the following should clarify.
XML Sitemap:
When you submit XML sitemap, Google algorithm reviews it and it will index pages based on its algorithm. There is no guarantee that it will index all submitted URLs.
XML Sitemap Priority:
It only lets the search engines know which pages you want for the crawlers understand in terms of priority. The priority you assign doesn't influence ranking.
Re-Indexing:
Google algorithm re-crawls pages in certain interval regardless you submit xml sitemap or not.
How to get crawled fast:
There are several factors you can consider like:

Have HTML sitemap, still very handy search engines.
Do internal linking from important pages based on your priority.
Submit XML sitemap
Share pages on social media sites, G+ is an important to place to start.
Build authority in general which can also influence fast crawling.
Comment: Sitemaps are generally only used to audit that Google can effectively crawl a site. Where a sitemaps have a real benefit is for extremely huge sites and sites that have content behind a login or pay wall.


overheat after install ubuntu please

Question: Laptop suddenly shutdown due to overheat. Before my laptop suddently shutdown, my fan run faster.
There any coding to overcome this problem?
Hp pavillion g4-2029wm
Ram 8gb
How to solve this problem?
Answer: I have overheating problem with HP Pavilion g4-2002tx, it has switchable/hybrid graphics between Intel and AMD Radeon. However, it has never gotten sudden shutdown.
I just power off the AMD Radeon by sending OFF to /sys/kernel/debug/vgaswitcheroo/switch. Now, the thermal is about 63° C and I conclude that the problem is caused by the discrete graphics card, so just turn it off when it is not needed.
echo OFF | sudo tee /sys/kernel/debug/vgaswitcheroo/switch

If you sudo cat /sys/kernel/debug/vgaswitcheroo/switch:

Before turning off discrete graphics (AMD Radeon):
0:IGD:+:Pwr:0000:00:02.0
1:DIS: :Pwr:0000:01:00.0

After turning off discrete graphics (AMD Radeon):
0:IGD:+:Pwr:0000:00:02.0
1:DIS: :Off:0000:01:00.0

Hope it helps.

overheat after install ubuntu please


Does the process of photosynthesis occur in insectivorous plants?

Question: Does the process of photosynthesis occur in insectivorous plants?
Can you please give me a clear answer and explain to me how?
and also can you describe the environment in which they grow ?
Thank you
Comment: is this a homework question? you need to give a little more detail and effort when posting to this site... please see the help page where it discusses "how to ask a good question" - thanks!
Comment: Normally the carnivorous plants are photosynthetic and green. They need to depend on animals for nitrogen. They are adapted to regions of poor nitrogen availability in soil.
Comment: @AlwaysConfused  if you know the answer then post it as an answer. Use comments only to request clarification and suggesting something.
Comment: @WYSIWYG Ok but before that I'll have to go through some reference. However I've seen possible-answers, or where could be looked for, sometimes posted (and they helps, too). As well for unconfirmed answers sometimes it is told that "post it as a comment instead".
Answer: "Carnivorous plants are plants that derive some or most of their nutrients (but not energy) from trapping and consuming animals or protozoans, typically insects and other arthropods. Carnivorous plants have adapted to grow in places with high light where the soil is thin or poor in nutrients, especially nitrogen, such as acidic bogs and rock outcroppings."
Source: https://en.m.wikipedia.org/wiki/Carnivorous_plant


Oxidation States?

Question: Metals in low Oxidation states are usually reducing agents. Is there any example of a metal in zero Oxidation state acting as an oxidizing agent.
Answer: As with pretty much every "is there ______?" in chemistry, the answer is yes, there is.
Of course, using the pure metal itself as an oxidising agent would be really tough. However, if you use certain tricks to stabilise the negative oxidation state, it is possible. For example, π-acceptor ligands such as $\ce{CO}$ withdraw electron density from the metal. So, $\ce{M[(CO)_n]^m-}$ complexes are stable for certain choices of $\ce{M}$, $n$, and $m$. For more details see: 18 Electron Rule For Determining the Stability of Transition Metal Complexes
Consider $\ce{[V(CO)6]}$, a 17-electron complex. It would be quite happy to accept another electron to become $[\ce{V(CO)6}]^-$. This reduction can be achieved with sodium metal. So, here vanadium(0) is acting as an oxidising agent; it is itself reduced to vanadium(−1).
These examples are not incredibly common, but it can happen.
Answer: If metal is in 0 oxidation state would get oxidized, then it would have to achieve a negative oxidation state since it would have to itself get reduced. Since it is a metal, it would have a really low reduction potential. If the reducing agent has a really high reduction potential, then I think it might be possible ( you will have to check the reduction potential values for that )

Oxidation States?


Corridor with a dead body turns out to be in a Möbius strip

Question: I'm looking for a book of science fiction short stories. One of the stories describes the experiences of a man who finds himself in a corridor with a dead body. The corridor turns out to be a Möbius strip. I must have read that late 1970s.
Comment: I know that story. I think it's from van Vogt, but it's definitely an older one from the 50s or so. A man wakes up to find himself in a triangular corridor; as he walks along it, he finds a dead body laid out in his path. He goes past it, and a little while later finds another body, this one crumpled in a heap. He eventually figures out that the whole corridor is a mobius strip, with down based on whichever wall he's walking on, so the body had fallen from one wall to what became the floor. It's all part of a recruitment test for some top secret organisation.
Comment: (And a half hour of googling didn't turn up anything of us, though hopefully there's enough extra information there to point someone else in the right direction)
Comment: Yes, I recognize it as well.  But haven't been able to narrow it down.
Comment: @andrewsi Yes, that's the story. I must have read that late 1970s.
Comment: A number of stories featuring Moebius strips are discussed at http://www.carliner-remes.com/jacob/math/project/lit.htm, however I don't think any are what you are looking for.
Answer: Ah-ha!
The story you're looking for is Theodore Sturgeon's "What Dead Men Tell".
It's collected in The Perfect Host, and at least some pages of it are available on google books
The protaganist wakes up in a triangular corridor; as he explores, he discovers a body that has been laid out in his path, and notices that the colours of the walls and his clothing change as he walks along. The whole thing is a recruitment test, to work out if he's smart enough to join a top secret organisation.
Since you're after a collection of short stories, here are the places where it's been anthologised
Comment: Good job!  Didn't recognize it as Sturgeon at all!


WinRAR installation on Ubuntu

Question: How can I install WinRAR on my Ubuntu 10.04 system? I tried sudo apt-get install rar.
Answer: WinRAR is a windows program for using RAR type files.  There is no 'WinRAR' on Ubuntu.
Installing rar like you did should add support for RAR files into the standard "archive manager" for ZIPS, TARs, etc.
(copied from William Fleming, he got some of my upvote power for his answer)
Installing unrar will help you with unpacking them:  sudo apt-get install unrar
Comment: gave you my up vote power ha!
Comment: @HoseinRahnama I haven't audited the `rar` command, however most tooling requires `unrar` to unpack the RAR file.  Note this answer was written in 2012, so things might've changed since then.
Comment: It seems that `rar` can also unpack `.rar` files. So, what is the point of installing `unrar`?
Comment: Yeah, that's an old answer. It would be nice if you update this answer by including some explanation about `rar` too. It seems that `rar` can compress and decompress while `unrar` only decompresses.
Comment: @HoseinRahnama When time permits it I can.  I'm quite busy nowadays though so sometimes I don't get to update the older answers I've written.
Answer: sudo apt-get install unrar

This will allow you to unpack them.
Answer: Two ways to install WinRAR in Ubuntu:
Method 1: Install the available rar and unrar tools
In the Terminal type:
sudo apt-get update
sudo apt-get install rar unrar
sudo apt-get clean

It will install the rar software and after installation, it will open rar files in the archive manager
Method 2: Install wine and then WinRAR
Install wine and download the winrar.exe from WinRAR website and install the WinRAR software similar steps to be followed for the installation in windows and after that rar files are able to open
For more details see this blog post.
Answer: If you're referring to this, it's a commercial version, as you can see, and it has not a GUI.
I suggest using file-roller, which is the default archive manager for the GNOME desktop environment.
Answer: I know that the pre-installed Archive Manager can open some compressed files, but during my experience to open some .rar format, that brought me an error. one of the practical app to open such files and extract them is unrar that can be installed through the command below:

sudo apt-get install unrar

for this purpose, the useful command and its functionality is here:

test your rar file if it is corrupted :unrar t <yourRARFile>
extract the containing file in full path: unrar x <yourRARFile>

WinRAR installation on Ubuntu


Holding all other parameters constant, why is theta higher for ATM calls than for ATM puts?

Question: Compare theta for ATM puts and ATM calls with all other parameters (e.g. volatility, strike price, price of underlying, risk-free rate, etc.).
Comment: I don't know enough of the theory to put in a formal answer, but I think this has to do with different volatility skews between the puts and calls.  And this is not always the case, although mostly correct for stocks, you may find some options on some commodities that exhibit the opposite.  Also something to do, for securities, to the fact that moves on the downside tend to be more violent/pronounced than on the upside, and this gets reflected in the the IV of each option which will drive the price.
Answer: Assuming 0 dividends, the underlying is not hard to borrow, and the option is European:
If the risk free rate is 0, the theta decay for strike and maturity matched options on the same underlying are equal.  If the risk free rate is negative, the put will have a higher theta decay.
The intuition for this is that a long call option position borrows money to buy stock.  There is implicit interest expense.
A put is effectively short the stock and lending cash.  This is implicit interest income.
Consider a long call option and short put option position with the same strike and expiration.  It replicates a futures contract.  Hopefully, this example will aid the intuition about why the call is a form of borrowing cash and the put is a form of lending cash.
Answer: I'm not well versed in the Greeks since I only use delta.  I'll take a stab at it but take this answer with a grain of salt.
Theta has different formulas for both call and put options. Whether it's merely a change of signs to account for direction or whether it relates to the distribution curve, I couldn't tell you.  It's above my pay grade. Perhaps a calculus quant will drop by and offer that explanation.
What I can tell you is the pricing relationship of puts to calls  when  at-the-money:

P + I = C - D

Let's assume that there's no dividend.  Then:

P + I = C

Due to the carry cost, the call's premium will exceed the put's premium by the amount of the carry cost or "I" .
Since theta is the amount that an option's value will decline every day until expiration and since the call premium is higher then the call's theta must be higher.
Answer: Theta is the phenomenon that if the underlying's price remains stable, the option's value goes down. Stocks usually go up, and options are priced with that in mind. So if the stock does not, in fact, go up, then it's performing less well as expected, which helps puts and hurts calls.
Another way of looking at it: when you say "ATM", that means that the strike price is equal to the current underlying price. But the expected price at expiration is higher than the current price, so a call that is currently ATM is, in some sense, underwater (in that the option will be valuable only if the stock underperforms expectations). And theta is higher for underwater options.
Charles Fox talks about borrowing money, which is yet another way of looking at this principle.


js not load properly in docker devbox

Question: I have installed dev enviroments for magento 2 based in configuration beta provides
But js not load even i already have setup permissions and installed sampledata
Anyone know how to fix it?
 Running in ubuntu 16.10 with docker 1.13.0 MagentoCE2.1.3

Frontend
Comment: if static generation not work... could you provide what link do you followed to create docker container? it caused due to various reasons like wrong port expose, wrong base url. could you check base url from database and check the same will be present as the root path of all the css&js in page source.
Comment: I got configuration based in macos but run in ubuntu
Answer: The issue is occur because after install magento 2 you haven't deploy its static content. So magento 2 unable to find your css and js. Try run below command in same sequence :
To resolve this issue run below commands :

php bin/magento deploy:mode:set developer (set the mode of
environment is developer)
php bin/magento setup:di:compile(it will generate all the proxies
and dependencies )
php bin/magento setup:static-content:delpoy(it will deploy all the
static content)
php bin/magento cache:clean and php bin/magento cache:flush(clear
the cache) It will resolve the issue.

Also check permission of you var/generation directory it should be 770 or 755
Also for more refernce check this link - No images or JS on new Magento 2 installation
Answer: Can you clear your cache and reploy your static contents? You can use the following commands and run it from your Magento install directory /var/www/magento2:
php bin/magento cache:flush
php bin/magento setup:static-content:deploy

Comment: yes but not work
Answer: You need to deploy the static files, clean cache, upgrade the setup on database, reindex and give the right permission on folders, so do that:
alias mage="php -d memory_limit=-1 -f bin/magento"
mage deploy:mode:set developer ;
chmod -R 777 pub/static/ var/ pub/media/ &&
rm -rf var/view_preprocessed/ var/cache/ var/page_cache/ var/tmp/ var/generation/ pub/static/frontend/ ;
mage cache:clean &
mage cache:flush &
mage indexer:reindex &
mage setup:upgrade &&
mage setup:static-content:deploy ; mage setup:static-content:deploy -f;
mage setup:db-data:upgrade &&
mage dev:source-theme:deploy &&
chmod -R 777 pub/static/ pub/media/ var/

Maybe will be necessary give the permission to the folders out of the
  docker container.

js not load properly in docker devbox


Problem with repeated icons

Question: What's the best way to avoid repeating icons on each row, it clutters the layout and takes attention from other important elements.
Answer: Or, perhaps something like this?

download bmml source – Wireframes created with Balsamiq Mockups
This way, you don't really have two columns of the same icons, but you still see them. You could even color them on hover behind the counter label, if you have a mouse-based UI.
Answer: You may only show them on hover. Or you may use greyed out icons and color them on hover. This way, they do not get too much attention.
Comment: This is the best solution and widely implemented. I'd suggest displaying the icons on the first row of objects, and keep the rest on hover. This way the user is given a clue about the UI and encouraged to see how the icons for lower rows would appear.
Answer: If they're really the same in each column, just take them out and place them as column titles. This way you can also attach a label to them and not leave the users guessing.
Comment: Is there are a lot if rows, users may forget which is which.
Comment: This is a good solution, problem is I can't use any more vertical space. So I wouldn't be able to fit this, most probably users already see those icons in other parts of the app and already know what they are.
Comment: It's just a simple table, like thousands of other tables on the web and elsewhere. Solutions exist for very long tables as well, e.g. repeating or sticky title row.

Problem with repeated icons


Mate terminal change background transparency programmatically?

Question: I've decided to experiment with making my life more beautiful by having background images scraped from flickr that change every 30 minutes together with transparent terminal and editor windows.
However, this has some downsides. Occasionally the images are too visible and impede editing, so I want to tweak transparency.
Thus I want a quick way to change transparency in my editor (emacs: done) and my terminal (mate-terminal, not-done).
This appears to be possible in gnome-terminal (Changing gnome terminal transparency with a command in Ubuntu?). My understanding was that mate-terminal was forked from gnome-terminal.
" You can use gconftool with the key /apps/gnome-terminal/profiles/Default/background_type (you might have to use a different profile name than "Default"): "
But I don't seem to be able to find any settings that change when I change background.
meld <( { gconftool  -R / | sort ; gsettings list-schemas | xargs -n 1 gsettings list-recursively  | sort  } ) <( { sleep 20 ;  gconftool  -R / | sort ; gsettings list-schemas | xargs -n 1 gsettings list-recursively  | sort  } )

Source code
I tried reading some sort code. This looks like a good starting point: https://github.com/mate-desktop/mate-terminal/blob/078d0b1fdac2e50dfa4411b612e78a4be134e47d/src/terminal-screen.c#L1111
The profile looks to get found like so profile = g_value_get_object (value); The reference manual for this function call can be found here but the documentation for GValue seems a little opaque.
Anyway yes, does anyone know enough to get an answer for this?
Possible lines of attack

Use btrfs snapshots to discover exactly what changed
Use *strace *to work out what is going on (strace output is a bit noisy because of this being an X application)
Read the code mode

Alternatives

Switch to gnome-terminal. I'm disinclined to do this because something that is unlikely to change. My understanding is that MATE was forked because gnome was changing too fast so this seems like a good choice.
Switch to another terminal. I'm not open to this. But don't really know which terminal to switch to
Intelligently render backgrounds to ensure that they are tinted correctly
Have keybindings that modify the background rather than the terminal
Answer: mate-terminal store it's settings in dconf, separate set per each terminal settings profile. So if you have default profile then it will be:
$ dconf read /org/mate/terminal/profiles/default/background-type
'solid'
$ dconf read /org/mate/terminal/profiles/default/background-darkness
0.5

First setting for background type - solid or transparent, and second one for transparency level.
To change transparency settings programmatically you have 2 options:

Use single profile and change it's settings via dconf:
$ dconf write /org/mate/terminal/profiles/default/background-type "'transparent'"
$ dconf write /org/mate/terminal/profiles/default/background-type "'solid'"

Create 2 profiles with different settings and choose one when launching terminal:
$ mate-terminal --load-config=FILE


Salesforce.com configuration review tool

Question: This is regarding quality control for Salesforce.com projects.  For Force.com development (custom coding), we have at least Source code security scanner which does static code analysis to some extent.  Do we have any other tools/utility for reviewing Salesforce.com configuration.  Whilst I understand that configuration is based on the requirements, there should be some sort of review against standard Salesforce.com configuration benchmarks/guidelines.
I have seen different solutions being offered for configuration review, most of them based on ISO 25010.
Has anyone used any tool/application for Salesforce.com configuration review?  Appreciate any inputs in this regard.
Answer: One nice tool for configuration reporting is Cloud Converter by Model Metrics - https://appexchange.salesforce.com/listingDetail?listingId=a0N300000016cVIEAY
Another nice tool is Snapshot from Dreamfactory - https://appexchange.salesforce.com/listingDetail?listingId=a0N300000016YhyEAE
it is a paid app, but you can do a lot with the free 14-day trial.


Oceans of sugar?

Question: Simple/Vague question but what would it take to have a world that oceans aren't  salty but sweet? Oceans full of sugar is that even possible?. Also secondary  question could life survive in the water?
Comment: Rewired brain chemistry. You can make anything taste like anything else.
Comment: Broadly no.  Sugar needs something to make it, as an organic molecule.  Your second question is answered here: https://worldbuilding.stackexchange.com/questions/115341/replace-sea-salt-with-sugar-what-happens/115343
Comment: The main problem is that salt comes from runoff of minerals. However  sugar requires a living organism to produce it. Do you want almost zero salt? Approximately how much sugar? The same as a teaspoon in a coffee?
Comment: @chasly-supportsMonica around as much as the real world sea is which is 3.5 percent so 1-3 percent sugar would be fine or any amount that can make the ocean taste sweet.
Comment: Also, as covered in part by the question I linked above, if the life in question is anything like life on our planet, a) the seas wouldn't be sugary for long, and b) everything would die very quickly.
Comment: Also, perceptible sweetness starts at 0.2% sucrose concentration by mass in water, for human adults.
Answer: A Few thoughts:
Unfortunately, a sea of sugar isn't very likely. Sugar would give water osmotic pressure like salt, but sugar is a high-energy molecule that would be a product from a living creature. The sea would represent a HUGE amount of metabolic effort to produce, and a huge amount to protect from things eating it (it's a virtual witch's candy house). So why on any planet would you have an entire SEA of sugar-water?

Toxicity: The local life isn't like terrestrial life, with very different biochemistry. Sugar is actually the local equivalent of cyanide. The sweet local organism (SLO) that produces it is more tolerant of the stuff than the rest of the ecosystem, but can't actually USE sugar for anything useful. The SLO has been toxifying it's environment for a long time trying to eliminate competitors for space or predators. Over time, it's needed more and more sugar to keep adaptable rivals under control. Sugar would spontaneously degrade when exposed to oxygen, so you might need a reducing environment.
Lure: Your world contains huge organisms. The sea contains large predators that secrete sugar as a lure. The closer you get to the predator, the sweeter it gets. The sweet-loving prey animal would need to be a high-value target to make the expenditure worth while, so at least Kaiju-big would make sense. Eventually they would get smart and avoid sweetness, so they would need to be rather dumb.
Amoebic Sea: Your sea represents a part of the biochemistry of a REALLY large organism. Maybe it's using the sea to make vast blocks of alien honey, slowly sweetening it until it crystallizes. What you need vast stores of sugar for is up to you - maybe there's a 30 year hibernation cycle due to an eccentric orbit. Maybe it's energy stores for launching interplanetary spores. Who knows?
Artificial sweetener: Not all that is sweet is sugar. Maybe the waste product of the local species is a compound that is sweet like saccharine. An artificial (to us, not the locals) sweetener can be much sweeter, more stable, and possibly lower in cost that sugar is. I feel this is a bit of a cheat, but it's probably the most plausible of all these solutions (pun intended).

As to other species, they would need to be adapted to the sweetness, but there is nothing intrinsically incompatible with sweetness and life (except in the sugar-is-cyanide scenario).
Comment: Compare your SLO to the earliest photosynthesisers who pumped the world full of a hideously corrosive metabolic toxin. Somehow, evolution found a way to cope ;-)
Answer: The ancient romans used to make syrup by boiling grape juice in lead pots. The resulting syrup contained some amount of a thing called "sugar of lead", which does taste sweet but ironically is a salt.
Sugar of lead is lead acetate. It does not form naturally, but in a fictional world it could be produced by microbes in the water. This would be very toxic and dangerous to animal life as we know it, but in an alien world where this is a thing, the alien life would have evolved to be tolerant to that chemical.
Answer: A birthing pool for a megahive
On your planet the dominant form of life is a societal hive creature similar to supersized bees or ants of Earth. From humble beginnings they have scaled up to continental level hives dominated by a single queen and with specialised functions for the workers/soldiers/farmers.
To produce young efficiently they birth young and secrete sugar into major bodies of water so that the larvae can feed quickly once they emerge. Rival forms of life have been exterminated or are so terrified of the soldier caste that they stay away from the tempting sugar seas.

Oceans of sugar?


Mystery Romex in junction box

Question:
I replaced a light switch installed at the bottom of the basement steps with one that has a dimmer. When I opened the junction box i saw there are two Romex wires coming in. One is connected to the switch at the top of the stairs which makes sense as this is a three way switch. I don't know what the other one is connected to. The copper is connected to the ground, but the black and white wires are exposed and not connected to anything. Is this some kind of standard practice I'm not aware of or should I disconnect the ground and cap off the wire? I'm assuming the mystery wire is not live. I'm picking up a voltage meter tomorrow to confirm. Even if it's not live, I feel uneasy having exposed random wires in the box. Any advice or input would be greatly appreciated.
Comment: Examine the place where power is delivered to this lighting circuit, ie. at the other switch or at the lamp. I'll bet the circuit is not properly grounded there because no reliable fault ground is available.
Comment: Thanks for the feedback. The other box is grounded.
Answer: It's not unusual to see an unused wires folded up in a box with the ground connected and the other conductors capped.  Unfortunately it's very rare to see anything marked or labelled to help the next guy figure out what's what.
This one's a little different in that it's clipped short on purpose - someone wanted to discourage trying to use the wire - and the wires are not capped.
I'd cap the wires and leave it alone.  Turn off the breaker for the light circuit, test to see if the short wire is live, and if so find and turn off that breaker.  I'd peel back the jacket 1/2", carefully strip 1/4" or so off the black and white, and twist on a small wire nut.
Tracing the wire to figure out where it goes and the rest of the story could be a bit of a project, and there's nothing to indicate any hazard, so I would not bother.
Comment: Great input. Thank you so much. I am going to try exactly what you suggested. Will update with findings.
Comment: I tested the mystery wire and as expected it is not live. I guess the electrician used it to ground the box. I capped the wires and closed up the box. Glad to have that concern off my mind. Thanks to all who helped.
Answer: It looks like someone retrofitted ground and used a whole Romex to do it, possibly to avoid rules in the Electrical Code that restricted  retrofitting ground.  In 2014 Code those rules were abolished and it's now legal to run just a ground wire.
Comment: Yeah... I was the thinking the same. Thanks for the input.

Mystery Romex in junction box


How do I create a custom content entity?

Question: There are already some resources describing how to write a custom content entity for Drupal 8. Perhaps the most useful one is the one included in the Examples module. I'd like a super-basic example that introduces Drupal 8 and PHP5 OOP concepts step-by-step, without throwing me in the deep end.
Answer: Building a basic content entity type in Drupal 8.
In this case we create a Drupal 8 content entity to match a node from our Drupal 7 site, in preparation for migrating this data.
The entity does not implement the Field API so remains in code throughout. Nevertheless it can be a useful skeleton for building out Content Entities.
Background.
This stems from the need to build a basic custom drupal 8 content entity to hold data coming in from a migration.  Elsewhere we will explore writing tests to drive our field code and plugins for field constraints For the time being it is suffice to say:
Our new Drupal 8 advertiser content entity will have basetable fields:

UUID
ID
Advertiser Name

Defining a Content Entity in Drupal 8.
First all our custom entities now live at web/modules/custom.
Inside our custom entity the file structure that we will end up with looks like this:
web/modules/custom/advertiser$
├── advertiser.info.yml
└── src
    ├── Entity
    │   └── Advertiser.php

We start by defining our custom module in module_name.info.yml. This is self explanatory:
name: Advertiser
type: module
description: 'Barebones advertiser entity'
package: custom
core: 8.x

Meanwhile The basic Advertiser entity class and associated schema is defined in src/Entity/Advertiser.php.
We start with an annotation that describes the class that our file contains.
/**
 * @file
 * Contains \Drupal\advertiser\Entity\Advertiser.
 */

The next thing we do is define a namespace for our Advertiser Entity Class. This will come in handy whenever we want to use our classes.
namespace Drupal\advertiser\Entity;
Now it is time to define our entity, which we do in an annotation! - TIP: This is the  actual definition of the entity type it is read and cached so be sure to clear the cache after any changes.
/**
 * Defines the Advertiser entity.
 *
 * @ingroup advertiser
 *
 * @ContentEntityType(
 *   id = "advertiser",
 *   label = @Translation("Advertiser"),
 *   base_table = "advertiser",
 *   entity_keys = {
 *     "id" = "id",
 *     "uuid" = "uuid",
 *   },
 * )
 */

Because this is a barebones entity we only use a few properties and no handlers (like access). For a comprehensive list of available options for your entity see the docs here: https://www.drupal.org/node/2192175
At this point we have a functional module that defines our custom content entity, however if we go ahead and enable the module we will see that the 'advertiser' table has not been created in the database.
drush sqlc
SHOW TABLES;

This is because our class doesn't have any methods that explicitly interact with the database. Furthermore we need a description of the bare minimum of methods needed for an entity to interface satisfactorily with the Database.
Generally we can add classes by adding something like use Drupal\Core\Entity\ContentEntityBase; after our namespace defintiion at the top of our script. This makes these methods available to our own class, which can extend them or in the case of Interfaces, implement them.
We do two things, we extend an existing ContentEntityBase class that already has the necessary methods to interact with the DB, and implement an ContentEntityInterface to describe...

the methods that we need to access our database. It does NOT describe in any way HOW we achieve that. That's what the IMPLEMENTing class does. We can IMPLEMENT this interface as many times as we need in as many different ways as we need. We can then switch between implementations of the interface without impact to our code because the interface defines how we will use it regardless of how it actually works. - https://secure.php.net/manual/en/language.oop5.interfaces.php

All this means is that we end up with the following: Tip Remember to add any new classes through a use statement at the top of our script:
class Advertiser extends ContentEntityBase implements ContentEntityInterface {
But we still need use these new useful methods to put something in the database, we start with the basic fields for our entity.
The method baseFieldDefinitions comes from ContentEntityBase class that we are extending.
It takes two parameters:

The entity type definition. Useful when a single class is used for multiple, possibly dynamic entity types.

And it returns

An array of base field definitions for the entity type, keyed by field name.

So we implement it like this:
public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {

  // Standard field, used as unique if primary index.
  $fields['id'] = BaseFieldDefinition::create('integer')
    ->setLabel(t('ID'))
    ->setDescription(t('The ID of the Contact entity.'))
    ->setReadOnly(TRUE);

  // Standard field, unique outside of the scope of the current project.
  $fields['uuid'] = BaseFieldDefinition::create('uuid')
    ->setLabel(t('UUID'))
    ->setDescription(t('The UUID of the Contact entity.'))
    ->setReadOnly(TRUE);

  return $fields;
}

So altogether we have this:
<?php
/**
 * @file
 * Contains \Drupal\advertiser\Entity\Advertiser.
*/

namespace Drupal\advertiser\Entity;

use Drupal\Core\Entity\ContentEntityBase;
use Drupal\Core\Field\BaseFieldDefinition;
use Drupal\Core\Entity\EntityTypeInterface;
use Drupal\Core\Entity\ContentEntityInterface;

/**
 * Defines the advertiser entity.
 *
 * @ingroup advertiser
 *
 * @ContentEntityType(
 *   id = "advertiser",
 *   label = @Translation("advertiser"),
 *   base_table = "advertiser",
 *   entity_keys = {
 *     "id" = "id",
 *     "uuid" = "uuid",
 *   },
 * )
 */

class Advertiser extends ContentEntityBase implements ContentEntityInterface {

  public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {

  // Standard field, used as unique if primary index.
    $fields['id'] = BaseFieldDefinition::create('integer')
      ->setLabel(t('ID'))
      ->setDescription(t('The ID of the Contact entity.'))
      ->setReadOnly(TRUE);
 // Standard field, unique outside of the scope of the current project.
    $fields['uuid'] = BaseFieldDefinition::create('uuid')
      ->setLabel(t('UUID'))
      ->setDescription(t('The UUID of the Contact entity.'))
      ->setReadOnly(TRUE);
  return $fields;
  }
}

Now when we run drush en advertiser -y; drush sqlc we can see the advertiser basetable has been added to the database!
Comment: Just wanted to comment that learning it this way is highly highly advised instead of using Drupal console outright. REALLY helps to understand the code before using convenient tools.
Comment: That's one way to write tutorials I guess, but note that Drupal Answers isn't meant for answers that would fill a whole blog post. Would be awesome if you could help me bring the entity documentation (https://www.drupal.org/developing/api/entity) up to speed. It has similar pages already, would be nice to have those updated and verified.
Comment: @Bedir, would love too. Where can I put this?
Comment: See https://www.drupal.org/node/2629550 for example, you could improve/check that. documentation pages on drupal org can be edited by anyone.
Comment: @Berdir - I added this at: https://www.drupal.org/node/2683569
not sure how adding it to the relevant page/sub-page works ... perhaps you could do that. I have similar tutorials for using Tests to drive further development of the content entity, adding custom field constraints/validators and finally migrating a D7 node into the new D8 custom content entity... Will post when done.
Comment: To place it in the menu, you just have to set the book outline. There's a vertical tab at the bottom, just go there and select the parent. The easiest way to do that is start by going to the page where you want to add it as a child page and click on the add child page link somewhere on there.


Low Poly Modern (2018) Standards?

Question:
What are the standards to which it refers? (https://en.wikipedia.org/wiki/Low_poly)
Comment: This is described in the page you referenced https://en.wikipedia.org/wiki/Low_poly#Low_poly_as_a_relative_term
Answer: The term standard is not used in the sense you think. It's not like an SI units standard or sRGB (literally meaning standard red green blue) standard. There is no definition for lowpoly, other than it needs to display in real-time. It depends on hardware.
By modern standards (standards in hadrware) it is safe to say that the dolphin can be rendered in real-time and so would be considered low poly.
By ancient standards (4bit computer the size of a room) you wouldn't be able to render that at 60fps, it would be considered high poly.
Comment: It might help to show the dictionary explanation of the particular meaning of 'standard' used here. For example https://en.wiktionary.org/wiki/standard#Noun "Something used as a measure for comparative evaluations."
Answer: There are no standards! Low poly is always a relative term. There are several factors that decide whether it is low or high poly. It is also described in the same article.
But think of it as trying to decide if a room is minimalistic decorated. A large living room with 30 items can be minimalistic, but if you place the 30 items in a small corridor it is not. There are no guidelines and is more of a assesment from room to room - the same can be said of low / high poly

Low Poly Modern (2018) Standards?


Could there be observable gravitational warnings of an approaching vacuum decay bubble?

Question: I understand both gravitational waves and a hypothetic vacuum decay bubble travel with the speed of light. Does this mean there won't ever be any observable warnings of vacuum decay before an observation point would get cought in the vacuum decay bubble? Or could we, for example observe a change in orbital path of the sun through the galaxy if vacuum decay would start in the core of our own galaxy?
Answer: No, all models of vacuum decay bubbles I have seen in the literature expand at the speed of light which means there will be no warning. Gravitational waves move at the speed of light, so they are no help.


Do the 2 individual 120v legs coming from meter into main panel have to be connected to specific terminals on the main shutoff breaker?

Question: The old SEU wiring in my box has a black and red cable, but I have also seen newer SEU service cable where both 120v legs were black.
Answer: No, there is no "positive or negative" or "left and right" or whatever.  This is the same when hooking up a 240v appliance.  The two legs don't matter and there is often no way to differentiate the legs other than maybe black and red.
Comment: NO PHASING REQUIRED AS WOULD BE WITH THREE PHASE..+
Comment: Yeah I know.  I have an installation with 2 conduits between the panel and the machine shop.  One conduit has 20A circuits. The other conduit has four 30A circuits arranged B-R, B-R, B-R, and B-R.  *In the bottom of the panel and splice box are a bunch of wire markers that fell off*. Imma rearrange them B-B, R-R conduit 1, B-B, R-R conduit 2.
Comment: I assumed there was no specific order for single phase, but better to ask the community and get a consensus. I'm actually surprised that in roughly an hour of Google searching I could not find any forum/blog/article that specifically touched upon this exact topic.
Answer: Yeah, in split-phase, nobody cares what color the hots are.
I've seen people go in backflips to have red and black. It's just not necessary.
Of course in cables, it's best-practice to do something to distinguish conductors.  You never know what the application will be.


What is Master Device in MIDI?

Question: So, what is the "Master Device" in Multi-output device? Cause I'm trying figure out how MIDI Aggregate Devices work, I need to now what is it.
Answer: MIDI system needs to know who is the master.
It is for the master volume adjustment when you have multiple output devices.
Each output device can have its own volume adjustment preset, but the master volume will control overall Volume.
The MIDI has 2 options to set up:

The Create Multi-Output is self explanatory.
The Aggregate is:

You can combine several audio devices to use as a single device, known
  as an "aggregate device." By aggregating devices, you can increase the
  number of discrete audio inputs and outputs without purchasing more
  expensive multichanneled audio equipment. For example, if you have an
  eight-channel audio device and a two-channel audio device, you can
  combine them to work as a single ten-channel audio device.
For the aggregate device to work correctly, the sample rates of the
  combined devices in the aggregate device must be set to the same
  sample rate.

What is Master Device in MIDI?


Clean data and noisy data: which one has higher entropy?

Question: I have a question regarding to the information theory. Between clean data and noisy data, which one has higher entropy? I think the noisy data has, am I right? But, noisy data does not have more information than clean data, it just contains more noise.
Comment: Be careful about how "information" is defined. I think you're shifting meaning from the first time you use it (implicitly, when you equate it to entropy) to the second time, when you mean something else by information. The issue here isn't clean vs noisy data, it's simple equivocation.
Answer: Entropy is not a measure of relevance, it is a measure of randomness. So your guess is correct.
Answer: Slide 5 of this lecture summarizes the notion of entropy in detail:
http://www.cs.nyu.edu/~mohri/mls/lecture_14.pdf
The key idea is that entropy is a measure of the uncertainty of $X$. Thus, more noise increases the uncertainty and, therefore, the entropy increases.
Notice that entropy is maximal for a uniform distribution (i.e., complete noise):
$\newcommand{\E}{{\rm I\kern-.3em E}}$
$$
H(x) = \E\Bigg[\log\frac{1}{p(X)}\Bigg] \leq \log \E \Bigg[\frac{1}{p(X)}\Bigg] = \log N
$$
The inequality follows from Jensen's inequality. It assumes finite support.


MySQL Server wont Start after Yum Upgrade

Question: After executing yum update on my CentOS Cloud Server the MySQL doesn't start.
After searching on web for the error:
Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

I tryed to search for the file mysql.sock through find and grep but didn't succeded. The error log of mysql, after trying to start it in safe mode is:
130529 13:51:18  InnoDB: Starting shutdown...
130529 13:51:23  InnoDB: Shutdown completed; log sequence number 0 43655
130529 13:51:23 [Note]
130529 13:51:23 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
130529 14:15:52 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
130529 14:15:52 [ERROR] Error message file '/usr/share/mysql/english/errmsg.sys' had only 481 error messages,
but it should contain at least 641 error messages.
Check that the above file is the right version for this program!
130529 14:15:52 [Note] Plugin 'FEDERATED' is disabled.
/usr/libexec/mysqld: Unknown error 1146
130529 14:15:52 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
130529 14:15:52  InnoDB: Initializing buffer pool, size = 8.0M
130529 14:15:52  InnoDB: Completed initialization of buffer pool
130529 14:15:53  InnoDB: Started; log sequence number 0 43655
130529 14:15:53 [ERROR] Aborting

130529 14:15:53  InnoDB: Starting shutdown...
130529 14:15:58  InnoDB: Shutdown completed; log sequence number 0 43655
130529 14:15:58 [Note]
130529 14:15:58 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended

Hope you guys can help me, i can provide any information you need, just tell me how can i help you helping me out.
EDIT:
Tryed to chwon the files for mysql and chmod that either.
Before negative flagging me, look what i wrote, i've already used MYSQL_UPGRADE and the error is the same about socket.
[root@cpro5022mysql]# mysql_upgrade
Looking for 'mysql' as: mysql
Looking for 'mysqlcheck' as: mysqlcheck
Running 'mysqlcheck with default connection arguments
mysqlcheck: Got error: 2002: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) when trying to connect
FATAL ERROR: Upgrade failed

Answer: You have an error there in your log which explain what's going wrong. [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it. means that your mysql table's schema is out of date and needs to be upgraded.
Comment: Here is the code when i run mysql_upgrade:
[root@cpro5022 mysql]# mysql_upgrade
Looking for 'mysql' as: mysql
Looking for 'mysqlcheck' as: mysqlcheck
Running 'mysqlcheck with default connection arguments
mysqlcheck: Got error: 2002: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) when trying to connect
FATAL ERROR: Upgrade failed


How to get user Interests?

Question: This is not a duplicate of How can I get the interests of my friend through facebook api?. user_interests permission (to access /me/interests) is useless (if not deprecated) Facebook feature that hardly ever returns any data.
Instead, I am referring to the data aggregated by Facebook at this page:

These are all user likes grouped into categories like "Music", "Books", "TV Shows", etc. Generally, user likes can be retrieved through /me/likes. However, the latter query returns a rather vivid array of categories.
Is there a way to get user likes categorised into the same generic categories like Facebook does?
Answer: https://developers.facebook.com/docs/reference/api/user/:

The User object has the following connections:
books: The books listed on the user's profile.
games: Games the user has added to the Arts and Entertainment section of their profile.
movies: The movies listed on the user's profile.
music: The music listed on the user's profile.
television: The television listed on the user's profile.

The fields favorite_athletes and favorite_teams are deprecated, though. Not sure, if there will be any replacement for these analog to the above connections – or if users are just supposed to normally "like" the fan pages of athletes/teams in the future.
Answer: My approach to this issue is to process the API data within my application as such:
'Books' => array('Fictional Character', 'Writer', 'Book', 'Author', 'Book Store', 'Library', 'Magazine'),
'Films' => array('Actor/Director', 'Movie', 'Producer', 'Studio', 'Movie Theater', 'TV/Movie Award', 'Fictional Character', 'Movies/Music'),
[..]

e.g., if user likes "Writer" or "Book", I assign the like to "Books" category.
However, this solution is not ideal as Facebook might change category names, add new names, etc.

How to get user Interests?


How to fix 0x80071A91 error in Windows Vista / backup Vista system?

Question: I am getting this error below:

"File backup could not save your automatic backup settings for the following reason:
Transaction support within the specified file system resource manager is not started or was shutdown due to an error. (0x80071A91)
Please try again."

I tryed this (to fix) on cmd:

"fsutil resource setautoreset true C:\" as an adm

But did not work.
What I want is to make a backup of all my files.
Answer: Did you delete all files first from C:\Windows\System32\config\TxR before executing fsutil? Make sure explorer shows system and hidden files.
Comment: +1: I gave you that tip on Channel 9, you had the same issue with an update.
Comment: @magicandre1981 Yup, I'm passing on the knowledge.
Answer: John see this blog post

Recently I was very frustrated installing Vista on my home machine. It's not that something wrong with Vista, it was drivers that drove me crazy. Problems I had were caused by the fact that nVidia failed to provide working drivers for RAID 0+1 array based on nForce 4 Ultra chipset (I've got ASUS A8N-E motherboard). When I finally managed to install everything, it was running fine for couple of weeks. After certain point though Windows updates begun to fail as well as Vista backup feature stopped working. I had basically only one clue. It's an error message I was getting when I tried to start a backup job:
File backup could not save your automatic backup settings for the following reason:
Transaction support within the specified file system resource manager is not started or was shutdown due to an error. (0x80071A91)
Please try again.
Microsoft help wasn't really helpful: http://support.microsoft.com/kb/927748/en-us. Googling didn't bring any luck either, so I start researching toward file system resource manager (FSRM). Accidently I found that fsutil tool has an additional argument "resource", which evidently controls FSRM behavior.
So, if you see a bunch of failed Windows Updates and/or your Vista files backup doesn't work anymore, here are the steps you need to do in order to reset FSRM:
Click "WinKey" on your keyboard.
Type "cmd" and hit Ctrl+Shift+Enter. That will bring you to the command prompt in Administrator mode. It you still have UAC enabled, it will ask you for permissions, click "OK".
Navigate to your Vista system folder (i.e. C:\Windows\System32)
Type "fsutil resource setautoreset true C:\" assuming that you have your Vista on drive C.
Reboot.


Is it fine to run a public website on the sql express db?

Question: Is it fine to run a public high traffic website on a sql server 2008 express db?
Comment: You need to define "high traffic."
Comment: You can run a public website off SQL Express with great performance. You can run a public website off a DataCenter edition with fusionio SSDs and terrabytes of RAM and the site can perform like crap. As long as the database has a sound design, the engine and response time should be fine. It might make sense to do some caching in your app, maybe not but just because it's free, doesn't mean it's dreck. It's your design and your access methodology that will make all the difference.
Comment: I mean something with traffic as this website but the website will access the db from each user browser every few second to get updated data.
Answer: Here is a partial list of restrictions of this version:

Number of CPUs:  1
Maximum memory utilized:  1 GB
Maximum database size:  10 GB
Replication: Subscriber only
Backup compression: N/A
Most of performance features is not available.
...

See comparison list for more details
Answer: Depending on your definition of high traffic, it is likely that you will see awful performance. If there is any transactional writes that happen often, you'll cap out the max database size rather quickly, and as mentioned above there are many hardware restrictions on express. Not to mention you don't have all the creature comforts for a professional enterprise instance (SQL Agent, etc.).
SQL Server express is more for embedded applications, or very small low-budget intranet applications.