A good quick introduction to Knot Theory?

Question: Is there a good quick introduction to knot theory?  I am relatively mathematically savvy so any level is appreciated.
Comment: "Relatively mathematically savvy" means very little unless you specify who it is that you're savvy relative to.  A bright high school student?  An undergraduate math major?  A graduate student?
Comment: I've heard "The Knot Book", by Colin Adams, recommended for this purpose. (I'm leaving a comment instead of an answer because I haven't read the book myself.)
Comment: Grad student in CS, leaning towards theoretical CS with an undergrad major in Math and a minor in CS
Comment: Neuwirth's "Knot Groups" is ta great introduction to knot theory. It best explains covering spaces, the original key to the calculation of invariants that distinguish them (100 years ago).
Answer: As Michael comments, Colin Adams has a well regarded text called "The Knot Book". Adams has also written a comic book about knot theory called "Why Knot?". It's very humorous but is a genuine introduction to the mathematics involved. This comic book comes with a plastic "rope" that can be knotted, unknotted, and twisted into different shapes.
I think "Why Knot?" qualifies well as a "good, quick" introduction to the topic. Well worth tracking down.
Comment: +1; the Knot Book is really a gem.  It treats a wide variety of topics, many quite deep and the subject of intense current research, in a very readable and engaging way.
Comment: Take care when reading first editions of "The Knot Book." Some copies include (without disclosure) corrections that did not appear in the original.
Answer: Rolfsen's textbook "Knots and links" is quite nice. It assumes a 1st course in algebraic topology, and is pleasant self-learner text.  Plenty of nice exercises.
On the higher-end of the knots textbook world, Burde and Zieschang's "Knots" covers quite a lot of ground in much detail.   Kawauchi's "A survey of knot theory" covers much more ground but in less detail.  Hillman's "Algebraic invariants of links" is more specialized and tends to focus on ideas such as Alexander modules, but it goes into them in more detail than I've seen anywhere outside of Jerry Levine's papers.
Chuck Livingston has a very nice looking book just called "Knot theory".  It appears to have a fair bit in common with Rolfsen's book, in that the central theme appears to be the Alexander polynomial.  I haven't read it yet (should arrive in a couple days) but it looks promising.
Answer: I love the book "On Knots" by Louis Kauffman. It's got a playful style, yet he develops a lot of deep mathematics. I read this in high school, and I got quite a lot out of it, and as my mathematical knowledge progressed, I got more and more out of it.
Answer: My intro to knot theory graduate course used "An Introduction to Knot Theory" by Lickorish.  The early chapters on Seifert surfaces and polynomials are quite nice.
Comment: +1. I came into this thread specifically to recommend that book. (I came across it through working on Seifert surfaces, so I appreciated that part as well.)
Answer: This answer is a little less popular of a suggestion, but it was how I first learned about knots, and I really enjoyed it. This book is primarily focused on Vassiliev Diagrams, and is currently unpublished, but available through the authors webpages. Yay! free stuff!
Here is a link to the CDbook by Chmutov, Duzhin, and Mostovoy. It is the first link on the page.
I personally found the focus on invariants very useful.
My second favorite would be Rolfsen, as Ryan suggested.
Good luck!
Answer: Two books I would recommend are:
Knots and Surfaces, David Farmer and Theodore Standford (American Mathematical Society; 1996)
Knots and Links, Peter Cromwell (Cambridge U. Press; 2004).
Answer: V.O. Manturov,  Knot theory, freely available online. The first chapter gives an elementaty introduction. To continue, you have to know basic topological concepts, e.g. fundamental group.
Answer: Although, in my opinion, it is strongly influenced by Rolfsen's Knots and Links, Prasolov and Sossinsky's Knots, Links, Braids and 3-Manifolds: An Introduction to the New Invariants in Low-Dimensional Topology is nice because there are references to recent articles in the appendices of each section. Moreover, it is the one of the very few books which gives an introduction to Vassiliev Invariant.
Answer: I'd certainly recommend all of the titles presented above; I personally worked from the Colin Adams book.
Here is a YouTube channel which I've found is helpful for those studying elementary knot theory.
Comment: The link might need editing.
Answer: Reidemeister's classic "Knotentheorie" (even its flawed English translation) is still the best, although it misses all the more modern stuff. --Ken Perko firstname.lastname@example.com.
Comment: Ignore all those out-of-date textbooks (except for Neuwirth's "Knot Groups"). You'll learn a lot more from by my Researchgate blog. --Ken Perko


Can I remove the stock camera app from iOS 9 or later?

Question: I would like to be able to remove the stock camera app from an iOS device without disabling the camera itself (because I would like to replace the camera app with a non-stock app).  I know MDM applications allow the camera to be disabled via the iOS mobileconfig restrictions, but can I remove just the (original) app while keeping a functional camera?
Answer: Short answer: no.
As of iOS 10, here are the stock apps that users can remove:

Calculator
Calendar
Compass
Contacts (iPhone only, contact information is retained in the Phone
app)
FaceTime
Find My Friends
Home
iBooks
iCloud Drive
iTunes Store
Mail
Maps
Music (if removed, you won't be able to use it with CarPlay)
News
Notes
Podcasts
Reminders
Stocks
Tips
Videos
Voice Memos
Watch app (you'll have to unpair your Apple Watch before deleting it)
Weather

As you can see, the stock Camera app is not one of these. I imagine there are ways to forcibly remove it, but you may lose that functionality of your iPhone permanently.
Answer: There is no way of making the non-Apple Camera app the default, (by swiping the lock screen, for example,) if that is your intention.
On the other hand, if you want more advanced photography abilities, I've found the apps Camera+ (for full manual control of the camera settings,) CameraBag, and TrueHDR very useful. Using these apps does not require the stock camera be removed at all.
Disclaimer: I'm not affiliated with, or have any financial stake in the developers of any of these apps.


How much can be developed the low pecs of chest

Question: i have visible low pecs but i don't know if i ended on that spot or i can develop it much more.My question concluded the previous sentence is how much can be developed the low pecs of chest?I think it can't be more "visible" more "down" or more "out".Have a limit those?No drugs,only workouts and proper intake foods meals.I want to ask the "distance" it can be obtained the low pecs.How much can it "grow"
Answer:
As you can see the pectoral major doesn't have much growth potential sideways as it is limited by it's attachment points to the arm, but there's really nothing limiting the forward growth of the pectoral that give it the thickness from sideways, well nothing except the natural ''physiological'' limitation of cellular growth.
No drug can alter the natural limit of muscle growth(which is equal for everyone), when a muscle cell becomes too big it dies out. But even then there is no evidence than any human has ever reached a limit in muscular growth.
Answer: For 'lower' pec work, do decline bench, dips and cable crosses with active mind muscle connection and heavy weights. 3 times a week setting two days for volume (lighter weight more reps) and another for heavy weight. Hit that with daily 8 hours of sleep as well as sufficient protein/nutrients. If you're at a good body weight right now, I might even go for a 3 month slow bulk to optimize growth.
Comment: I am not asking how to grow the lower pec,but I ask how much this muscle can be increased,the limit it has of growth
Comment: That's a pretty subjective question and i'm not sure tbh, it depends on the person, their age, diet, sleep etc. Way too many factors for me to make a broad statement.
Comment: Indeed,but it can't be length ,example more than 0.40 cm. Do you understand? Even in the best age it needs the chest can reach the full potential,diet ,sleep etc the chest low pec can't be so much bigger it has a limit.


Term for altitude of the sun?

Question: The sun travels in an arc across the sky. Where I live, during the summer the arc rises higher, but in the winter the arc is lower. Once might speak of highest altitude or elevation the sun reaches during any given day. In the old days this was called "high noon" when the sun had reached the highest point in the sky for that day. The town clock would be set to 12 at this point.
Is there a term for the elevation of the sun in the sky?
Comment: It's ["altitude"](http://heavens-above.com/glossary.aspx?term=altitude) and not "elevation".
Comment: The "arc" you talk about is called the Ecliptic (https://en.wikipedia.org/wiki/Ecliptic). This is the path the sun takes in the sky, and would stay stationary if the earth weren't tilted, but as it is tilted the suns path in the sky varies over a year giving us the seasons.
Comment: @rgettman I think both terms are used interchangeably. Something like "solar apex" might be an answer, but not really sure.
Answer: The term for when the sun is at its highest is "solar noon".
https://en.wikipedia.org/wiki/Noon#Solar_noon It is the moment the sun crosses the meridian. The meridian is an imaginary half-circle that goes from the northernmost point on the horizon to the highest point directly above you and then to the southernmost point on the horizon. The sun is always at its highest point in its daily path when it crosses the merdian.
You're right that in earlier centuries, each town would set its clocks at noon for when the sun was at its highest point. Those of us who are familiar with astronomy and history would call that type of timekeeping "apparent solar time". You can't guarantee an exact 24 hour day with "apparent solar time", so some people used "mean solar time" instead. (Historical note: Having each town choose its local noon became a nightmare for railway companies that wanted to set train schedules. So the railway companies urged the creation of 4 time zones in America and encouraged each small town to use "standard time" instead of "apparent solar time".
And as rgettman already mentioned, the term for the sun's height above the horizon is "altitude". Astronomers use the term "elevation" for a person's distance above sea level.
Comment: Astronomers use the term "elevation" as a synonym for "altitude". Some examples: https://dept.astro.lsa.umich.edu/ugactivities/Labs/outdoor_series/constellations/constellations.html , http://www.astro.caltech.edu/~mcs/CBI/pointing/ , http://www.gb.nrao.edu/GBTopsdocs/primer/horizon_coordinate_system.htm .
Comment: Actually is it always at the highest point when it crosses the meridian? Eg-  In the Northern Hemisphere, between mid-March and mid-June might it be slightly higher a few fractions of a second afterwards? (Genuine question, not just being an annoying pedant)
Comment: @adrianmcmenamin Good question. I thought the solar noon was defined to be the moment of crossing the meridian. Maybe the sun is slightly higher a few seconds before or after because of the analemma. https://en.wikipedia.org/wiki/Analemma The analemma shows us the sun's noon position changes a bit from day to day, making a slender figure 8 in the sky.
Comment: @adrianmcmenamin One might imagine an exception for when somebody is standing at the North Pole on the longest day of the year. Then the sun just goes in a circle above the horizon each day. That's the one time and place (in the Northern Hemisphere) where the sun is always at the highest altitude for every minute of the day. Even then, it is at its highest when it crosses the meridian simply because it is always the same altitude for every minute of the day.
Comment: @adrianmcmenamin http://astronomy.stackexchange.com/questions/937 addresses the question of declination change being fast (for the moon, not the Sun) enough to alter the highest point. Could you ask your comment question as a separate question? I think it might be interesting to see how many seconds it really is.
Comment: Actually, http://astronomy.stackexchange.com/questions/1213/ already asks this other question.
Comment: The Sun crosses the meridian twice a day. Once in the highest, and once in the lowest point - when it's usually below the horizon, but during polar day it may happen it's above the horizon in both cases.
Answer: A word for the highest point (not elevation) is zenith. See: http://www.merriam-webster.com/dictionary/zenith , second definition:

the highest point reached in the heavens by a celestial body

So 'solar zenith' would describe the highest point the sun reaches.'

Term for altitude of the sun?


PhD in Mathematical Physics

Question: I am currently an undergraduate math major and have hopes of attending graduate school in applied math. I also have a love for physics and thinking of minoring in physics. After some research, I found that many departments have professors in the research area of mathematical physics. Is having a minor in physics a good background to pursue research at the graduate level in mathematical physics?
Comment: Despite the name, mathematical physics is part of mathematics. It should really be called "physics-inspired mathematics". Having a physics background helps, in order to understand the motivations etc, but you can get by knowing just mathematics.
Comment: Many natural science profs will think it's an early Christmas if a mathematician turns up, speaks their "language" and wants to work with them. Just as an alternative, if you're also OK with math that is applied very *badly*. ;-)
Comment: I don't think a lot prof in physics department doing mathematical physics though. Probably among 0 ~ 5mathematical physicists for each school
Answer: It depends on what courses you end up taking as part of your physics minor. Mathematical physics leans heavily on Lagrangian and Hamiltonian mechanics, quantum mechanics, statistical mechanics, and electrodynamics.
I don't know how many credits you have available for your minor and what the requirements are in your university to take those courses. At the very least, make sure that you have taken both classical mechanics and quantum mechanics. Your math background in real and complex analysis will put you in great shape to learn the formalisms of the other theories.
Good luck!
Answer: Degree names don't matter: coursework matters
It really depends on what subjects you've taken courses in and what subjects you've learned in your free time. Grad schools don't particularly care if your degree label lines up with what they're offering, they care if your coursework and professional experience does. In the US, many graduate programs explicitly list the courses they want you to have as a minimum background. Contact their admissions office or look through their websites for the required background coursework.

PhD in Mathematical Physics


Pomegranate = 613 seeds?

Question: Has anyone ever counted the seeds of a pomegranate? Is it true that each pomegranate has 613 seeds?
Comment: I counted once when I was younger and I only got 407
Answer: When I was young, my older brother and I counted a bunch of pomegranates. Some totaled 607, 624, and other numbers in that area. Although none totaled exactly 613, in our series of counting the average came out to 613!
Thanks to msh, at the bottom of R. Zivotofsky's article I found that someone has an ongoing experiment regarding just this question and so far the average seeds in a pomegranate is ... you guessed it! 613!
Comment: It'd be hard to come up with a sampling plan that doesn't end up relying on some non-trivial assumptions, so I don't think you could really come up with One True Average. We should probably content ourselves with the idea that most pomegranates that we tend to see will have *about* 613 seeds.
Comment: On average there are "about" 613 mitzvot :)  It all depends on if you combine the list of Mitzvot according to the Ramban or the Rambam as well as other lists :)
Comment: The international experiment is almost as anecdotal as yours. The results indicate clearly that different regions' pomegranates have different average numbers of seeds. To get an international average, you'd have to weight the contribution of each region by that regions contribution to the world pomegranate population.
Comment: The Parshblog entry cited by Dave essentially makes this argument in more detail.
Comment: I agree that the "experiment" as well as my experience is hardly a scientific conclusion. What if someone really had a lot of extra time on his hands and did a real sampling ...
Answer: See Ari Zivotofsky, "What's the Truth about... Pomegranate Seeds?" for a general discussion about the claim that the fruits have 613 seeds each; his final footnote discusses the מציאות (facts on the ground).
Answer: Just to contribute a tiny bit of data (while agreeing with the other answers that the count varies):
Tonight I was dismantling a pomegranate while waiting for dinner to cook, and one thing led to another, and I found that this single data point had exactly 613 seeds.  I only eat about one or two pomegranates a year, so I am unlikely to collect a statistically-meaningful sample in my lifetime.  But there existed at least one, anyway. :-)
Answer: Yes I have.  No it's not literally true.
In light of Alexander Haubold's study, I now eat my words.
Comment: or your pomengranate
Comment: That study is debunked in the Parshablog post I linked to.
Answer: Parshablog cites a [somewhat dubious] study which claims that the average number of seeds in pomegranates worldwide is 613. He also states that Malbim is the source for the 613 claim.
Answer: I heard that "filled with mitzvot as a pomegranate" is not a reference to a certain number, or even an abundance, but the "fullness".
The phrase אפילו ריקים שבכם מלאים מצוות כרימון is explained as being full like a pomegranate. When a pomegranate grows, its seeds fill it up leaving no space, as opposed to other fruit we know that have some extra space or inedible parts. The pomegranate fills all available space - so we wish to fill every ounce of ourselves with mitzvot, and even the "empty" among us are as full as that.
(Will edit upon finding the source. blndr)
Answer: It isn't true. In terms of the Malbim about 613 seeds in a pomegranate, see it inside, as well as a nice discussion by me and others, here:
http://parsha.blogspot.com/2010/11/how-many-seeds-in-pomegranate.html
Comment: Your work precedes you :) http://mi.yodeya.com/questions/3848/pomegranate-613-seeds/3854#3854
Answer: In the new Artscroll biography of Rav Chaim Kanievsky zt"l - p.215 it notes how Rav Chaim was asked this question by Rav Zilberstein shlita.
Apparently Rav Chaim started thinking through the sources, and after a few seconds declared that it is not listed in Bavli. A few more seconds passed and he confirmed it was not in Yerushalmi. This repeated itself with statements that it was neither in the Midrash or Zohar.
Finally he asked for a Shir HaShirim with the commentary of the Malbim. It writes in Shir HaShirim 4:3:

כְּפֶ֤לַח הָֽרִמּוֹן֙ רַקָּתֵ֔ךְ
Your brow behind your veil, [Gleams] like a pomegranate split open

The Malbim writes there:

כפלח הרמון שהוא מלא תרי"ג גרעינין
Like a pomegranate split open - which is full of 613 seeds.

He then showed R' Zilberstein a Derashos Chasam Sofer Vol. 2, Shabbos HaGadol 5591 where it writes:

It is known that a pomegranate has 613 seeds, corresponding to the 613 mitzvos...I say that if the seeds represent the mitzvos, pomnegranate nectar - which is the primary part of the fruit - symbolises Torah, which is a fount of sweet pomegranate nectar. Thus, a pomegranate that is intact alludes to a scholar who engages in the study of Torah, which contains the 613 mitzvos, and who fulfills them.
Answer: Of course not all pomegranates have 613 seeds; however, when I Googled - average number of of seeds in a pomegranate, the answer in the snippet block at the top of the search results page was 613. The source was: https://www.aquaphoenix.com/misc/pomegranate/
Comment: See here for why this does not show the average to be 613. http://parsha.blogspot.com/2007/09/613-seeds-in-pomegranate.html
Comment: Dead link......
Comment: works for me. I just tried.

Pomegranate = 613 seeds?


How can I avoid rakk attacks?

Question: Rakk, those bat-like things that serve pain from above, seem to have attacks that are impossible to avoid.  Even if I jump at the last second, they still end up somehow scoring a hit on me.  Is there a way to dodge their attacks?
Comment: Are you _strictly_ interested in dodging or are ways of killing the rakks before they hit you good too?
Answer: You are playing Borderlands 2, not Hitman: Absolution, last I checked.  Nothing in Borderlands 2 should scream STEALTH, rather, it should scream, SHOOT!
Shotguns work great against rakk, as the spread of the pellets allows for almost insta-kills at close range.  Trying to use weapons that have higher spreads should allow you to shred through rakk quickly.  Avoid using snipers or rocket launchers; rakk move fast, and can easily dodge your attacks.
That said, if you really want to dodge a rakk attack, try strafing to the side and jumping.  That usually makes them miss.
Comment: On the "attack is best defense" side of things, if you're the Commando, the turret is a blessing against those things.
Comment: @leokhorn Deathtrap (from Gaige) makes short work of just about anything in the air as well.
Comment: Sniper rifles are just as good as anything to kill rakks. They fly in a straight line at you, so they're impossible to miss.
Answer: Rakk always attack in  a straight line. Pay attention to the mini-map to see where they are in relation to you, then rotate to face their attack. Any rapid-firing weapon should be sufficient to take them down. I've successfully used shotguns, assault rifles, and pistols (both repeaters and revolvers).  A well-timed melee attack will also take them down.
If none of these work, you can always equip a shield that provides elemental damage (such as a Maliwan Spike shield). When the rakk hits you, it takes damage, and usually enough to kill it.
Answer: Equip a spike shield which damages all melee attackers, and the Rakks will kill themself when they attack you. Rakks have quite low HP, so when you have a good shield and they aren't too high-level, their first attack will be their last one.
Answer: Presuming you actually want to avoid them...
In general order of priority...

Some rakk flocks are just hanging around, especially early on. If you don't shoot at them, they won't attack. (Later-game flocks seem to be a lot more aggressive though.)

And that's roughly the limit of how to not poke the bear, so to speak. Next up is "how not to get hit while killing them".

if you can get to somewhere with overhead cover, that will often prevent them from getting an attack run in.
Less effective but still useful is to get against a wall - not only does it prevent the attacks from that side, the rakks tend to get hung up on the wall trying to finish their swoop, which makes them easy targets.
If you're in open space, getting a vehicle makes life easier (both because you have infinite ammo and a bigger stack of health). I'd recommend the machine gun turret.

In all those cases (and the worst-case "stuck in the open with no vehicle"), you want a shotgun, SMG, or assault rifle, watch your minimap to see where they're coming from, and pour fire downrange. Rakks attack straight-line and don't have huge health bars, so it's fairly easy to drop one.
Answer: The strategy that works best for me is to run backwards while aiming to the entire flock. They tend to fly in a line so you'll have a good angle to shoot one after another as they fall.
Some rapid fire weapon (i.e. any good Vladof gun) should dispose of them easily. If they get close, switch to a shotgun. Rather than dodging, don't give them the chance to approach you.
This is quite class-agnostic. There might be a better option based on your character class AND skills.

How can I avoid rakk attacks?


Ltspice Transformer Simulation

Question:
I am trying to simulate a transformer with a turn ratio of  1:1. The voltage of the primary and secondary are equal but I am getting a different current in the winding (why?). Also I see some DC offset in the primary current (why?). Please correct me if I am simulating design wrong.
Thanks
Comment: Its because of load resistance R1, may be.
Answer:
I am getting different current in winding(why?)

The primary current contains the load current AND the magnetization current. The secondary current is only the load current.
Magnetization current is due to the voltage supply being attached to an inductor (with secondary open circuit).
You'll need to be clearer about what DC offset you are seeing but i suspect it doesn't really exist after the first few cycles of AC have passed.
Comment: Or, I(L1) has the current flowing into a 10mH inductor plus the current flowing into a 10 ohm load. So that's a peak of 3.8197A into the 10mH and a peak of about 1.188A flowing into the load. Added together as per \$\sqrt{A^2+B^2}\$ and you get 4 A peak in primary
Comment: To see the magnetising current alone, disconnect the load.
Comment: sorry I am not able to comprehend the explanation.If it is not a problem can you explain with equivalent circuit of transformer
Comment: What is it you are unable to comprehend and how well do you read English? The words I have used are fairly simple I believed but I'm not about to guess what you don't understand so please be explicit.
Comment: My English is fine.Is there a way we can see both component of Primary current i.e. load and magnetising current?
Comment: Look at the phase of the current. As your load is resistive the current relative to it is in phase with the supply, the magnetising current is 90° ahead.
Comment: Also try powering the circuit when the source voltage is at 90 degrees on switch on and not at 0 degrees - this is your problem with the so-called DC offset.
Answer: As @Andyaka said, the primary current is the sum of the load current and the magnetizing current. The secondary current is just the load current.
If you want to see them separately you can use the equivalent circuit of the transformer. To make an ideal transformer you set the inductance to be high enough (ideally infinite). Then you add a magnetizing inductance in parallel with the primary equal to your transformer inductance (10mH in your case).
As you can see I(L1) and I(L2) now match perfectly. I(Lm) is the magnetizing current. I(R2) is the primary current that you were seeing in your simulation and is the sum of I(L1) and I(Lm).

Ltspice Transformer Simulation


Does Bruce Wayne have a middle name?

Question: Does Bruce Wayne have a middle name? I have heard many different ones so I want to know if he has a middle name and what it is.
Comment: You might want to consider changing your acceptance now that the canon has changed to include a middle name
Comment: I believe it's Fountainsof.
Comment: Okay no wait, I've got a better one now. In an enormous troll directed at Commissioner Gordon, he changed it to "Atman".
Answer: According to a web article from Bleeding Cool, published April 5, 2017, by Rich Johnston, titled "Lois Lane's Last Name And Bruce Wayne's Middle Name, Both Revealed Today (SPOILERS)", since the DC Rebirth (May 25, 2016–November 29, 2017), Bruce Wayne's full name now is apparently (now anyway), Bruce Thomas Wayne.

Batman (Rebirth) #20
Comment: I've taken the liberty of editing in the picture that the article is actually referring to.
Comment: When I saw this question I thought it would be Thomas for his father. I'm happy I was right!
Answer: Bruce Wayne does not have a known middle name, but there are some common propositions for a middle name among them are Bruce, Robert, Anthony, Alen, or Thomas.

Bruce: Possible if his real first name is Robert.
Robert: Coming from Robert the Bruce, one of 2 names Bruce was named for by Bob Kane.
Anthony: Mad Anthony Wayne, the other of the 2 names.
Alen: His Grandfather's first name.
Thomas: His father's first name.

Thomas, Jr. was used in several places as a name for a Brother to Bruce. So Thomas is the least likely. Alen is likely due to him knowing a bit about Alen Wayne which means he was likely told as a child and usually that comes from parents saying "you were named after x. That's how you got your name"
Comment: Indeed. Thanks for pointing it out ^.^
Comment: Surely Alen and Thomas are his Grandfather's and Father's first name, not last?
Answer: We know that Kate Kane is Bruce's cousin especially in arrowverse (Earth 1),
Kate Kane's(Batwoman) father is Jacob Kane and Martha Wayne is his sister.
Martha Wayne's middle name is Kane.
(Martha Kane Wayne)
So Bruce is (Bruce Kane Wayne.)
Comment: Can you cite a source for this, or is it just speculation?
Comment: Welcome to SciFi.SE! I'm afraid I'm struggling to understand your logic here. Wouldn't "Kane" have been Martha Wayne's *maiden name*, not her middle name? And why then would she have given Bruce "Kane" as a middle name? What evidence in the comics is there to suggest that she did that?

Does Bruce Wayne have a middle name?


Why is it not recommended to use server-side stored functions in MongoDB?

Question: According to the MongoDB documentation, it isn't recommended to use server-side stored functions. What is the reason behind this warning?
Answer: I am sure I have stated the list a couple of times despite the Google search result being filled only with people telling you how to do it:

It is eval
eval has natural abilities to be easily injected, it is like a non-PDO equilivant to SQL, if you don't buld a full scale escaping library around it it will mess you up. By using these functions you are effectively replacing the safer native language of MongoDB for something that is just as insecure as any old SQL out there.
It takes a global lock and can take write lock and will not release until the operation is completely done, unlike other operations which will release in certain cases.
eval only works on Primaries and never any other member of the replica set
It is basically running, unchecked, a tonne of JS in a bundled V8/spidermonkey envo that comes with MongoDB with full ability to touch any part of your database and admin commands, does that sound safe?
It is NOT MongoDB and nor is it "MongoDBs SQL", it runs within a built in JS environment, not MongoDBs C++ code itself (unlike the aggregation framework).
Due to the previous point it is EXTREMELY slow in comparison to many other options, this goes for $where usage as well.

That should be enough to get you started on this front.
Comment: Are the issues around locking/concurrency/performance still valid?  The current documentation suggests that as of version 2.4, the default JavaScript engine now "allows multiple JavaScript operations to execute at the same time" without acquiring locks.  http://docs.mongodb.org/manual/core/server-side-javascript/
Comment: Ok, thanks! About this statement: "Due to the previous point it is EXTREMELY slow in comparison to many other options...". I believe when you wrote this, you mean slow in read operations, right? My problem is: I have perform a function over each document of my collection, and read-update-write is really slow when using mongodb-nodejs-native driver. Any thoughts on this?
Comment: @EduardoMelo Any operation, the JavaScript will be slower in execution than the C++ code any day, not only that but it isn't natively put into JS, i.e. the JS enigne is started up, a thread made and then the C++ code passes the JS function to be run by the engine. Hmm if it is over every document then it sounds like a one time command, I would do this via the console on the same server as the master MongoDB
Comment: @StevePerkins I am unsure I have not tested it to be frank however, it is still not the native C++ code and optimisations you can garnish in the aggregation framework or native C++ code in MongoDB will not exist
Comment: @StevePerkins can you please guide me what is proper and good approach to use stored function, or if these are not  recommended that which the best option ??


Why do the highest temperature levels occur at midday?

Question: I also see that weather forecast sites show temperatures decreasing starting from 3 to 4 pm, but the thermometer shows that it starts droping at sunset.
Comment: This is called diurnal temperature variation.
Comment: https://www.thoughtco.com/high-and-low-temperature-timing-3444247
Answer: The highest temperature of the day typically occurs well before sunset but well after local noon (which in summertime is about 1:00 PM in areas that use daylight savings time). The reason for the lag between noon and the time at which temperature reaches a maximum is because is that the Sun continues to warm the ground, water, and air well after noon has passed. It's only when the Sun gets low enough on the horizon that radiational cooling to space exceeds the diminishing radiational heating from the Sun.
There's a similar four to six week lag between the longest day of the year and the hottest days of the year. Just as the Sun continues to provide warmth during the day well after local noon, the Sun continues to provide warmth during the year well after the summer solstice.


Is a rogue with the Use Magic Device feature considered proficient in armor and weapons?

Question: In the Dungeon Master's Guide for the Use Magic Device feature of a rogue it says on page 141 that "your proficiency bonus does apply" for a magical staff. Does this count as being proficient in the item? If so could a rogue wear magical platemail or use a longbow with no downside?
Answer:
Spells [...] A magic item, such as certain staffs, may require you to use your own spellcasting ability when you cast a spell from the item.
  If you have more than one spellcasting ability, you choose which one
  to use with the item. If you don't have a spellcasting ability-perhaps
  you're a rogue with the Use Magic Device feature- your spellcasting
  ability modifier is +0 for the item, and your proficiency bonus does
  apply. (DMG 141)

I have quoted the whole paragraph and the title to clear up the misunderstanding. The half-sentence you quote refers only to casting spells from a magic item and the use of a spellcasting ability when you do so. It does not mean that you are considered proficient with all uses of the item, just spellcasting.
Answer:
USE MAGIC DEVICE
  By 13th level, you have learned enough about the workings of magic that you can improvise the use of items even when they are not intended for you. You ignore all class, race, and level requirements on the use of magic items.  [PHB, pg 97]

You do not gain proficiency, only the ability to use.


Customise sorting in User Manager (Backend)

Question: I would like to add another field for sorting users in User Manager. I can't find in google what I need to edit (what files to edit, where fields should be created). I am new to Joomla, so I don't know if there are hooks available, I don't want to edit core files. I have a custom field for the sorting already, it is named Company name (Название огранизации). I need to sort users according to this value. How can I achieve that?
Answer: To start with you can create a override of the list page, your first image, by going into the Administrator Template you are using on your site, by default the drop down will display Site so you need to change it to Administrator.

Select the Tab Create Override and then going to com_users at the bottom of the Components list, expanding the selection and select the last file, users.

Then select the Editor Tab and make your way to the file you just created.

That is the relative easy bit, you have got a copy of the core file that you can edit and make your changes that wont be lost during upgrades etc. You can find out more about Overrides by reading the Joomla Docs or the may tutorials people have written to understand overrides in templates.
The more difficult piece of your requirement is getting the custom field value to place in the column of the display.
When you create a custom field for a component, in your case the com_user component, the field and its value are not stored in the components database tables but in the tables of the com_field component. You can see the tables #__fields_fields, #__fields_values, #__fields_group, #__fields_etc. When you see the custom fields displayed in a components output, there is separate processing that has occurred to retrieve the values of the custom field.
Because you can't override the Model or View for com_user that gets the data for the page you will need to add your own code in the override file you have created above that retrieves the value for the company custom field and display it in a new column. I expect you will need to read up on how to retrieve the custom field(s) but to point you in the right direction it will probably contain something like this;
$user           = Factory::getUser();
$customFields   = FieldsHelper::getFields('com_users.user', $user, true);

Comment: @mickmackusa that's the obstacle I didn't know about, I thought automatically created override file should actually override standard `default.php` file but that didn't work for me. I had `default2021-06-26-091595.php` that worked after I had renamed it.
Comment: Thanks a lot! I will mark your answer as right but I need to research how to retrieve custom field value to add this info to your answer.
Comment: @high sorry but I didn't see any value in your suggested edit on this answer.  Telling researchers to rename the `default.php` file as `default.php` seems nonsensical to me.  Feel free to comment to Irata if you wish for him to improve this answer.


Passing an array from shortcode-function to filter-function

Question: This might be a php question more than it is a wordpress question. I am not sure though, but please guide me if so. I am working on a trial plugin that I use for my training in the first stages of plugin development.
Here is a simplified example of the structure:
class trial{

    function trial() {
        add_shortcode( 'shs_ref', array( &$this, 'shortcode' ) );
        add_filter( 'the_content', array( &$this, 'after_content' ));
    }

    /*Run the shortcode*/
    function shortcode( $atts , $content = null ) {

        if ( !isset( $this->entries ) )
            $this->entries = array();

        array_push($this->entries,$content);

        return 'What number of shortcode is this: ',count($this->entries);

    }

    /*Add after the page content*/
    function after_content( $content ) {

        foreach($this->entries as $entry) /*This one is empty?*/
           $content .= $entry;

        return $content;
    }

}

new trial();

In the shortcode function, an array $this->entries is being filled with the content $content that the user has wrapped inside the shortcode clamps. For every new occasion of the shortcode, its content is appended to the array via php's array_push. I can then do something with this growing array $this->entries (for example count its contents, as in the example).
All this is fine and works.
The issue comes when I want a filter-function to use that same array. I want a list of all the collected shortcode contents to be added at the bottom of the page. At the top of the code, I use an add_filter which passes the_content to my other function called after_content. This works and the entire page content can be handled by the function. But the $this->entries array is empty. It kept its content while being used iteratively in the shortcode function, but it loses its content when it is used in the after_content function afterwards.
I have tried setting the $this->entries array as a global variable, for instance by adding var $stored_entries outside the function and then global $stored_entries; $stored_entries = $this->entries inside the shortcode-function, but it makes no difference. The content of $this->entries as well as  $stored_entries is NULL.
The question is mainly:

How can I pass the array on to this other function?

And secondarily:

Why is that array stored between iterations of the shortcode-function but forgotten when we enter the filter-function?
Answer: Okay, it turns out that I was missing a tiny little number in the add_filter command. The line:
add_filter( 'the_content', array( &$this, 'after_content' ));

should be:
add_filter( 'the_content', array( &$this, 'after_content' ), 12);

And now all works. The array is accessible inside the filter-function. This number is a priority variable: https://developer.wordpress.org/reference/functions/add_filter/, but if anyone will add a comment on the usefulness of it, please do so.


Question about Cavendish experiment

Question: I got a question. In Cavendish experiment was used lead in both of spheres. Can we repeat that experiment with balls made from stone  or anything else. Because lead could be a byproduct of radioactive decay and by that emit ionizing radiation. And by ionizing lead it can create positive charge and to be attracted.
Answer: Naturally found lead is not radioactive. Its longest lived isotope has a half-life of approx. 15 million years, which means that over the course of geological time this isotope would have disappeared. Unless it gets contaminated by radioactive isotopes of other elements or its produced by decay, as you mentioned, it does not radiate.
Having said that, you are correct that one has to be very careful about these kinds of error sources in precision experiments, especially when the error, as in this case, would have the exact same functional dependence as the effect that we want to measure! In case of the Cavendish experiment this is easy: you make the entire apparatus conductive so that all electrical charges are shorted out and the electric field it produces is zero.
The experiment, more exactly, it's modern equivalents, have been repeated with many types of materials to test the equivalence principle. That is one of the most important experiments in all of physics because general relativity and with that the entirety of modern cosmology depends on the equivalence principle being valid.
Comment: What would a video prove? The Cavendish experiment is only being done in high schools and on the college level these days, there are far more precise experiments of its kind. Some of the best versions are being done at the University of Washington: http://www.npl.washington.edu/eotwash/
Comment: Can you give me link to  video, with that experiment done with anything but lead.
Comment: *"Naturally found lead is not radioactive."* OK, let's have a trivial moment. For the purposes a very low background experiments recently mined lead is radioactive enough to be a problem because the lead-210 daughter of the radon chain is generally present. This makes lead from classical roman shipwrecks (known to have been above ground for many half-lives) valuable for such specialized purposes.
Answer: You can, of course, do the experiment with any kind of weights.  However, heavier weights give a stronger force and thus a better signal-to-noise ratio.  Charge non-neutrality due to radioactive losses are totally negligible, since macroscopic matter tends to neutralize very swiftly.  I have actually done the Cavendish experiment with much more radioactive depleted Uranium and the improvement in sensitivity over less dense lead was substantial.
Comment: I have a feeling that you didn't quite understand, though, why the experiment you did with Uranium wasn't sensitive to charge effects. It wasn't because those charges got neutralized quickly on their own. Somebody made an effort to make sure that there was no charge buildup on the experimental hardware.
Comment: No, there was no grounding apparatus or anything.  Had we been trying to do a state-of-the-art measurement, more carry would have been needed, but our experiment was precise enough for what we wanted.
Comment: What, exactly, did you want? The Cavendish experiment is pretty much obsolete except as a high school or college level physics lab experiment. Even there it's controlled for charge, even if you didn't notice.
Comment: The apparatus was for pedagogical purposes, for college students, but it was capable of 1% precision without electrical contacts.  I've never seen a version for students for which anything more than touch grounding was used (and we did not touch ground the U-238).
Comment: One does not need electrical contacts to control weak charges and one would not use any for something like this. It's all about selecting the right materials for the experiment.
Comment: Well, yes.  I'm not sure what point you're trying to make though.
Comment: Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/33469/discussion-between-curiousone-and-buzz).

Question about Cavendish experiment


Can I set the "Exercise" goal for my Apple Watch Activity app?

Question: The Apple Watch Activity allows for setting an overall "Move" goal, but I don't see how to change the green "Exercise" goal from the default 30 minutes. Is there a way to accomplish this?
Answer: No there is no way to accomplish this.
From Apple - Apple Watch

You close the Exercise ring when you reach the globally recommended 30 minutes of exercise per day. And you don't even have to do it all at once, which means you're more likely to fit it into your day.

From all searches I have performed I have not found any possible way to change it and the above quote suggests that 30 minutes is the amount Apple has fixed on (the call it "recommended").
Comment: This answer is out of date. It's possible to [change the exercise goal](https://apple.stackexchange.com/a/401973/18101) starting with watchOS 7.
Comment: @Nic Please post a new answer for this.
Answer: You aren't limited to one time around the ring in the Activity app. You get a double arrow for 1 hour of exercise, for example. You also receive awards for doubling or tripling the exercise ring.
You can use the Workout app to set whatever exercise goal you like. And you get a custom ring to fill in that app, based on target calories, distance, or time.
Comment: It's not 12 hours of standing it's standing once an hour for 12 hours.  They want you to stand up and walk around once per hour for 12 hours
Comment: Wow, this is beyond lame. I'm a knowledge worker and 12 hours a day of standing is never going to happen. I would've been happy to get 8 and feel a sense of achievement for that.
Answer: Most of the answers in this thread are incorrect. As of posting this, you can not change the exercise goal. As stated in the first answer this is set firm.
Additionally, the exercise ring always has a double-arrow. The icon does not change.
Answer: watchOS 7 enables changing the green Exercise Goal.

Apple Watch > Activity app > Scroll to Bottom > Change Goals

https://kirkville.com/change-activity-goals-on-the-apple-watch-in-watchos-7/
https://daringfireball.net/linked/2020/09/24/mcelhearn-watchos-7-goals
Answer: You open the activity app on your watch, then use force touch to adjust your daily goals. However, you can only modify the daily move goal (calorie goal), but not exercise or stand goal at this time.
Answer: I know exactly what you mean...When setting up the Apple Watch, they ask you whether you want the 30 min. for MOVE to be easy, medium, or strenuous. But once it's been set up there is no way to change it to either of the other levels.
Comment: Where's that setting?
Answer: On your watch, press hard on the activity screen in the activity app. You can increase/decrease the daily calorie burn goal. Doesn't look like you can change any other as of yet.
Comment: That's not the question.


How to learn Libreoffice Calc?

Question: I would like to become a good Libreoffice Calc user. How should I learn to use it, as I don't have any real business cases to solve but I would like to learn those? I have studied a good skills on Python and a very basics of R. I don't want to spend money more than 100 € for learning.
Comment: Define what it requires to be a good user. When you've defined it, notice that you also have created a todo list on what to learn.
Comment: It is unclear why you're mentioning Python and R. What is your intention with Calc? Given the mentions of Python and R, I infer you're not just trying to put some data in a tabular format.
Answer: It's a bit hard to answer since you have no stated goal, so we need to speak in generalities.  To learn LibreOffice Calc, you can:

Explore the interface and familiarize yourself with the different features and tools, like entering data, creating formulas, formatting cells, creating charts, filtering and sorting, and pivot tables.
Read through official documentation and user guides.
There are plenty of tutorials available on the LibreOffice website and on YouTube.
Create some practice projects for yourself.  Here are some challenges you might consider: https://ryanstutorials.net/programming-challenges/spreadsheet-challenges.php or https://en.wikiversity.org/wiki/Spreadsheets/Spreadsheet_challenges

Good luck!

How to learn Libreoffice Calc?


How do you set a range of number as an errorlevel in batch?

Question: I have this script in batch and got a range of questions 1 - 12.
All my code works, but I just can't seem to find a code to throw into my batch to throw out an error message for invalid ranges selected
Example: If I choose 13, which is not part of the options, it automatically goes to 1.
I want all number from 13 up, to show "invalid option" and then default back to the choice menu.
I am not using the shift command in my batch as I just used the following code instead
set /p choice=Type the number that corresponds to the Step you want to take.
if not '%choice%'=='' set choice=%choice:~0%

Notice the ~0 allows me to use numbers passed 9 instead of using the shift command.
Nevertheless, I need code that will say if the user type 13 or up and error appears.
Any ideas? In other words if choices are in ranges 13 - 999 show error.
Update
ok so, I looked at my code and realized I missed one line of code. which is
 @echo "%choice%" is not a valid selection/option
It seems that my coding was right where I gave '%choice%'=='' I just didnt leave an echo to say the selection was wrong. Turns out I didnt need any errorlevels in there.
Hope this helps someone
Answer: Just to clarify: The following code will output an error statement if the choice is greater than 13, and set the inputted value to the first character entered
@echo off
SET /P choice=Type the number that corresponds to the Step you want to take.
IF %choice% GTR 12 GOTO Error
ECHO You entered %choice%
GOTO End
:Error
ECHO %choice% is not a valid selection/option
set choice=%choice:~0,1%
ECHO %choice%
:End


Cannot connect to wireless router with TL-WDN4800 card on ubuntu 12.04

Question: My wifi card detects my router, but can't connect to it. On windows 8.1, it connects with no trouble. I have made sure that I selected the right security mode, and I have entered the router's mac address and ssid manually. I have TL-WDN4800 wireless adapter and a cisco x3500 router. I have tried changing my router's security mode to wpa and also tried disabling security, and my computer still won't connect.
Answer: I have finally found the solution to my problem. There are only Linux supported drivers for the TL-WDN4800 V1... I figured out I actually have the TL-WDN4800 V3 and the v1 drivers are not supported with the V3 for whatever reason. The windows drivers for this card can be found from the official TP-Link website and can be installed on to linux with Ndiswrapper.
Answer:
Reset your router to its default factory settings. This will ensure nothing esoteric is set in the configuration. See your manual, but best is the 30/30/30 reset. While powered on, hold the reset button down for 30 seconds - don't release it. Pull the plug while holding the reset button and leave power off for 30 seconds - don't release the reset button. Reconnect power while holding the reset button for 30 seconds. Release the reset button. Power off, then on.
The default config on the router should be IP 192.168.1.1 and it should be handing out addresses via DHCP. Your computer should pick it up as a viable network and connect. As should your smart phone. Nice to use the phone to confirm that the network is actually up.

If your phone doesn't connect and your computer doesn't connect, there is likely something amiss with the router itself. Or, you don't have any networking services running on it. Since you say your computer sees the router, neither of these seem likely.
When your equipment connects, it should do so with addresses like 192.168.1.xxx.

Open a terminal window and type ifconfig. The results should show that your network card has an IP address. Also try ping 192.168.1.1 and you should get responses from the router.
Comment: Hi, I have tried both of your suggestions, and still, it won't connect. My phone connects fine, and the router's ip address is as you said it should be. I have installed the latest drivers for my WiFi card, and tried connecting to my friends's router: it works fine. Any other suggestions?


I've had this lighting bug for quite sometime now. Can't figure out how to resolve it

Question: So, I got a new computer awhile ago, there's this bug whenever I play that makes everything look bright, even if there's no torches down. It may seem like a good thing, but when mobs are spawning around you and you can't see light levels, it kind of sucks. Does anyone know how to fix this?
Answer: This is allbright and it's a feature in optifine, some resource packs, and a few mods.
Answer: Your problem is that you have somehow enabled Fullbright. Go into your settings and change your brightness to any brightness and then change it back to what you normally have your brightness on. This should fix the issue.


Why was a complete test flight of Hughes Hercules H-4 (Spruce Goose) never undertaken?

Question: I get that ,the max altitude it was flown to was 70 ft. after its 3rd test taxi.I also am aware that even this was done to prove a point. But,why was there no attempt later on to complete a test flight and to check if it was Air worthy? Was no one curious at all ?
Comment: no-one wanted to front the money for the extensive test flights and see if it could fly away from the ground effect
Answer: By the time the government had pulled the plug on the program. Even that hop got Hughes into trouble because they had been expressly forbidden from taking off (he got off on a technicality, claiming it'd been unintentional, unexpected behaviour from an experimental machine, etc.).

If it had been anyone except Hughes I'm pretty sure the H4 would have been destroyed rather than preserved as a museum piece, the US government was that intent on killing the project there and then. They had a lot of air bases with long runways to find a purpose for, and long range air travel was an excellent purpose. They also wanted to find customers for the thousands of surplus transport aircraft (and bombers to be converted to that role). So getting rid of the traditional way to fly intercontinental, the flying boat, was important.

Were people curious? No doubt. But they also were budget conscious, the H4 had no more military application so there was no money coming out of the Pentagon. It had no civilian application, as for large payload ships are cheaper and for small, fast payloads it was too large. So even if there had not been active hostility towards the flying boat concept at the time from people with the power to release or deny budgets, there would have been little point in implementing an expensive flight test program (which usually requires multiple vehicles...) for an aircraft for which it was highly unlikely there would ever be any peacetime orders.

Of course 50 years later the idea was kinda revived with a short period of interest in Wing In Ground effect vehicles to fly troops and supplies over the feared Soviet submarine fleet in the Atlantic. But that didn't start up until near the demise of that threat in the 1990s and nothing ever made it past concept drawings (except paradoxically a few Soviet craft in the Caspian and Black Sea regions, the Ekranoplans).

I've little doubt the H4 would have worked as advertised, seeing it it looks sound in design, basically a scaled up B314. But there was just no market for it. It was an example of too big, too late.
Comment: Can you give the dates and maybe some references?
Comment: I get that the government was trying to pull the plug,but the aircraft was ready and had passed three taxing test-runs ,so why was no takeoff attempt made even after it was handed to a museum in pristine condition
Comment: @Qwe don't understimate the power of marketing & politcs. If politics used the excuse os unworthy to fly how they can look if they are proven wrong?
Comment: @Qwe the government owned the aircraft, not Hughes. The government grounded it, and didn't issue the paperwork that would have allowed its future owners to fly it even as an experimental.


Can hair short an electrical circuit?

Question: Taking this as an example - if a strand of hair gets in say in cpu socket of a PC or any other slot of device, what would be the consequences, rather the symptoms if the hair gets in between those pins:
Answer: No, not at this voltage. But it could 'open' the circuit and change the impedance of the circuit in the case of a CPU socket. If hair got in between one of the pins and the contacts there could be a problem.
Hair resistance is probably in the MΩ range, I couldn't measure anything with my meter and it goes up to 10 MΩ.
The pins on a processor need to make contact, hair is not going to help that situation and could open the circuit. Use 'dust off' or something to get it out.
Comment: It depends what kind of hair you use. Human hair should be ok up to 2.2GHz, but if you use cat then it's fine up to 3.2GHz. Dog hair is useful for low power applications, as it limits the frequency to 1.5GHz which uses less energy.
Comment: I'm imagining someone using an LGA socket as a hairbrush
Comment: @BeB00 Nicely done :)
Comment: @BeB00 They would use a [PGA chip](https://en.wikipedia.org/wiki/Pin_grid_array), probably an old Pentium.
Answer: A quick google shows that most of the time hair is an insulator, so a hair getting in will make it mechanically hard to plug it and possibly cause an open circt.
First however, define your hair.... Wet/with hair gel/oil/spray/dog/cat/dyed/etc then use google (or alternative) to find the conductivity of it. (Alternatively, experiment yourself)
Comment: So would the pc boot?
Comment: Depends which socket and which pins and so on. Assuming it's blocking the pins on the CPU socket, the motherboard will boot up and think that there's no CPU. Then it depends on the motherboard, but I'd expect some fault message would come out in some way.
Comment: Apart from some fault message or beeps or trouble of 'clean boot',would there be performance issues?Lesser performance of that system...
Comment: Possibly, but I wouldn't expect it. It could be temperamental I suppose... It's a 1min job to take your CPU out if it's a concern of yours, so check it.
Comment: Hey @puffafish,dont have any additional thermal paste,if the cpu has to be removed...and minute sized hair is undetectable..:-(
Answer: As others have said, breaking the contact is the biggest issue.
Dry hair is a good insulator, but hair is also great at absorbing moisture...
It can, under certain conditions absorb up to 45% it's weight in moisture. Add a little sweat salts and you have a conductor. As such a stray hair in a high humidity environment could introduce a current path that is detrimental to the functionality of the device.
Comment: Can that be detected by any software?without removing the components..
Comment: @SomaPaul Very unlikely.  Either the computer will work fine, or it will malfunction.

Can hair short an electrical circuit?


How to view plugin ratings?

Question: So I recently submitted my first plugin, and have since got a 1-star rating. Is there a place to review ratings and comments on my plugin?
Comment: Tried the stats tab?
Comment: just gives me a number of downloads...nothing on ratings.
Answer: There's no way to see the individual ratings, but you can see the total number of ratings and what they average out to. In the bottom left of your plugin page (in the repository) there is a section for "What others are saying", and it will display any posts from the WordPress forum talking about your plugin.
Comment: Is this your plugin http://wordpress.org/extend/plugins/op-archive/ ? if so, one thing that you could definitely do to improve it (purely on the presentation front) is to write out a much more detailed description, include screenshots, and just explain more about how the plugin works, how people use it, etc.
Comment: Pippin, thanks for the words of advice. I'll be updating the description and adding much more functionality. I only uploaded it to the repository so soon to get a feel for how the process works to publish plugins.

How to view plugin ratings?


Lost RAR password, is there any way to access my data?

Question: I lost my winrar password of my file. I need to access it. Is it possible? If yes, how?
Answer: It depends on the strength of your password. Winrar implements proper AES-128 encryption with 262144 iterations of KDF, there's no known bypass for that. You need to estimate the number of possible passwords (what's the length, what characters were used, did it contain words, etc.), and if it is large enough to not be bruteforceble there's nothing you can do, cryptographically speaking.
The other avenue is to find the password. If it was stored in a file then you can recover it for some time after the deletion, this may well be the easiest way.


Fingers touching adjacent strings while playing guitar

Question: Need advise, bought guitar last week and gone throught 100s of vids on youtube for biginners, how to hold, tune,chords all that but one thing that is discouraging me is my fingers touching the other strings!! No matter how much i try to keep my fingers perpendicular to strings, bottom part of fingers keeps touching the adjacent strings. I am feeling like my fingers are not for guitar. Can anyone help how to avoid this touching thing, does fingers gets thinner when callus builts  up?
Answer: It only really matters when your finger touches a string that needs to be sounding, and stops that happening. Touching another string that isn't played is not a problem. And in fact, you'll find out later that touching some strings in that very way is actually a necessary skill to achieve!
It does take time and practice to get accurate fretting when one is a beginner, so just keep going, bearing in mind that often you will be pressing too hard, and that in itself will spread your finger onto adjacent strings.Examine which fingers you are fretting with, and if possible, use the thinner fingers.
It may be worth considering a different guitar, with a wider fingerboard, thus wider spaced strings. Maybe not what you want, but classical guitars usually have wider fretboards.
I've played for a long time, still do most day,(guitar and bass) and haven't had callouses for over 60 years. They're often the product of guitars that need a good set up, or not-so-good technique. Some players swear by them, they're welcome! Anyone reading this, please tell why you disagree!
Comment: I find it's just the opposite.  The callouses are nice a hard when I maintain a regular practice schedule and soften when I'm rusty.  And I have a light touch.
Comment: Tend to agree about callouses - i tend to get them when my technique is rusty, then find that they soften up again as I get back into the groove and am able to use a gentler touch again!
Comment: @topoReinstateMonica - thanks for the feedback. Maybe we're the only two in the world who have that point of view...to some at least they're a badge of honour!
Answer: It looks like you're trying to get your fingers perpendicular to the strings, with the finger centred on the string its fretting. But you don't have to do either of these things: often the most comfortable hand position that lets the chord ring clear won't allow you to have all the fingers centered and perpendicular. Try to get into a cheater's mindset: on that bottom E string, for example, you can move the finger a little more towards the edge of the fretboard so that it doesn't foul the A string.
It's very important not to just try to do the shapes with your fingers : move your arm around to find the wrist position that works best for each chord. One of the reasons it takes many beginners a long time to learn chords shapes is that it takes them time to learn to move the arm and wrist around like this; if you can remember which wrist position works best for each chord, you'll learn a lot faster.
Also make sure your guitar setup is good, so that you're not having to press too hard with any of your fingers.
Answer: There are a few problems with your had position. First of all the edge of the fingerboard should not be touching your palm.  The only points of contact should be your thumb pad in the back, and your finger tips when playing fretted notes.
Second, it looks like the string is touching your finger right up at the finger nail and you don't need to place the string that far up on the finger tip.  Also, your nails are a bit long and jagged which might impare your ability to fret notes correctly.
In general the correct position is to use the finger tip and not the pad, but that also depends on the situation.   There are times when you have no choice but to use the pad.  But there is no need to severely bend the finger until the angle is 90 deg.  Having the flesh of your finger touch other strings is not a big issue unless you are trying to play a chord with some open strings, then you must not touch them or they won't sound.  It takes time and practice to find the right touch but is you move your finger up a little, and pull the palm away from the finger board that should help.
Comment: My nails protrude up to 3mm - way longer than those of the OP. Never been a problem at that length.


Why in this problem the phase shift due to reflection from wall is not considered?

Question: I know in reflection from rigid surface the path difference occurring is $\lambda/2$; where $\lambda$ is wavelength. But in this problem they did not consider that. Is the solution to this problem correct?
Comment: It is not possible to understand from the graphic you show just what you are asking. However, in general phase shift of a reflected wave depends upon the boundary conditions at the interface.
Comment: Hi Anik and welcome to the Physics SE! Please note that we don't answer homework or worked example type questions. Please see [this page in the site help](https://physics.stackexchange.com/help/on-topic) for more on what topics you can ask about here.
Comment: @John The OP is not asking for an answer to a homework question. In fact they have followed the instructons in the link you provided quite well as the question has been tagged "homework" and the OP has narrowed their question to one particular issue that is adjacent to the homework question. Could you please remove your comment as I do not believe it appropriate and could be taken as discouraging further posting by the OP.
Comment: I have not asked any solution to this problem .I just want to know the solution is correct or not ?if it had been a homework question I could have it clarified from my tuition teacher . John Rennie have you gone through the problem .? Did it seem to you a homework question ? Well it's an illustrative example . I would request you to remove the homework exercise tag . And mind to answer to the point what I asked yet.
Comment: Note that's questions of the form "Is this right" tend to be poor fits for this site because the answer is too short to be a valid answer
Answer: We are used to the fact that you get a 180 degree phase shift when a wave impinges on a denser material - for example in the difference between Lloyd's mirror and Young's slits.  You do not get one when travelling from denser to less dense, i.e. glass to air.
So it looks like the question forgot this... until you think further.
This is about sound waves rather than light. Now the speed of sound in the wall is not given but generally the speed of sound in solids is much greater than the speed of sound in air. (Makes sense as the atoms are directly linked, not flying around.) So the concrete or brick is (counter-intuitively)  actually less acoustically 'dense' than the air.  So there is no phase shift and the question is correct.
Answer: The solution is flawed, by more than just this. "The minimum distance x for which a maximum occurs at detector, the path length will be $\Delta = \lambda$" as a statement has not been justified and is completely untrue. A minimum for x requires a maximum for \Delta which you can see if you plot the two or differentiate. If we were to ignore the phase shift like is done in the answer this would give x=0 the minimal distance.
And yes you are right. There should be a half wave phase shift.


Set active object in Outliner

Question: In 3D view, click one of the selected objects while holding shift would set it as the active object. My question is how to do this in Outliners instead of 3D View? Because sometimes the object I want to set as active is very small or obstructed by other objects and it's hard to select in 3D View.
Answer: Hold Ctrl then click the object name in the ouliner.
Comment: With Blender 2.90 outliner select the object with normal click and Ctrl + Left Mouse Button can be used to toggle selected items without affecting other selections (that is, it adds/removes the clicked object to/from the selection). Unfortunately, the logic seems to be different from Viewport where you have to click with Shift to get the same behavior.

Set active object in Outliner


Sealing threaded PVC pipe

Question: What is recommended for Connecting 1" Schedule 80 PVC threaded fittings to prevent leaks. I have tried pipe dope, but leaks developed between nipples and elbows. Do you have any suggestions.
Answer: We use liquid sealant all the time with great success at 1-1/2" diameter and less.

Make sure you are coating the threads completely and evenly.
Some dopes require coating both male and female ends over certain sizes.
Maybe try a different brand.
Might just use teflon tape instead.
Plumber we know for a large local company uses teflon (to seal) and
pipe dope (to lubricate) at the same time although we do not practice
the same.
If these don't work, look at your threads and make sure they do not
have a scratch or nick in them.
Comment: I've had the best success so far with "PTFE pipe dope" (which is to say, try a different brand and or type, yes.)

Sealing threaded PVC pipe


3 stage evolution pokemon vs 2 stage evolution pokemon

Question: So, some pokemon have 3 stage evolution and some have 2. Are 3 stage evolution pokemon stronger than 2 stage pokemon? In pokemon game series, of course.
Answer: It depends on the Pokemon, here you can see all the base stats of every Pokemon in any evolution stage.
You can see other generations by clicking on the links in the most above section of the post.
Answer: No, a 3-stage evolution does not necessarily make that Pokemon stronger than a 2-stage evolution. Take, for example, Butterfree, which is a 3-stage, and Lucario, which is a 2-stage. Butterfree has base stats of 60/45/50/90/80/70, a grand total of 395. Lucario has base stats of 70/110/70/115/70/90 for a grand total of 525. And that's not even the Mega Evolution, which is even stronger than that. This shows that a place in an evolution chain does not denote higher or lower strength in any way.
Answer: Short Answer
On average, the final evolution of a 3 stage Pokemon is stronger than the final evolution of a 2 stage Pokemon.
Explanation
Average Base Stat Total of Fully Evolved Pokemon, by Stage

I pulled data from bulbapedia here, which lists the stats of all fully evolved Pokemon, and threw it into a spreadsheet. This gives me the base stat totals of all fully evolved Pokemon.
I cross-referenced with another page showing the length of evolution lines. For Pokemon with a recognized "Baby" stage on Bulbapedia I do not count the baby for determining the number of stages in their evolution. This means that for example, Blissey counts as a 2 stage evolution, not a 3 stage. I then calculate the average base stat total for Pokemon with the same number of stages.
I omit Mega and Primal Evolutions (which are not permanent/true evolutions), and only count the first entry for Pokemon with multiple forms (So Rotom, for example, will only be counted once, not 6 times)
As a side not, 1 stage Pokemon are the strongest, likely due to legendaries dominating this category.
Answer: It all depends on the pokemon. Especially if your including Mega Evolutions. Like a Lucario (3-Stage) can be overpowered by an Espeon (2-Stage) because of the Type Matchup.
Comment: Actually, Lucario is a Steel type too, so it hasn't the Psychic weakness. Morover, MLucario can learn Dark type moves, and has a base Speed stat greater than Espeon.
Comment: Lucario is a 2-stage pokemon, mega evolution is a separate thing
Comment: I understand that but he did not specify whether he wanted to include it or not
Answer: the average 3rd stage evolution pokemon is much better than the average 2 stage or single evolution (discounting Legendaries)


How do I prevent white box(es) (face detection) from showing up on my Canon EOS 60D?

Question: I use a Canon EOS 60D to shoot a separate angle facing the audience at my Church. It works pretty well, except I have one huge issue. Whenever I point it to the audience, a bunch of white boxes start showing up singling out everyone's face, or just a particular face and then I get to switch from face to face. The only way I have been able to take it off is by switching to a large white square box, which is even worse. I'm sending out the camera shot via HDMI Mini- HDMI. How do I prevent my EOS 60D from having these white boxes appear?
Answer: Go into the menu system and look at the fourth page from the left. You should see AF mode, second option down. Select this and you will see three options, Live mode, :-) Live mode and Quick mode. Chances are your camera is set to :-) Live mode which is the face detection mode, select one of the other two modes and your boxes should disappear.
Comment: This just changes the nature of the overlay, for me :'(


Wine Gaming Problems

Question: Can someone please give me a step by step way in how to use wine I've checked a lot of you tube videos and their pretty old because i'm only seeing people using 32bit installation of it while there's a 64bit as well and I have a 64bit system and because I tried to run Need for Speed Most Wanted on xubuntu while using play on Linux to guide me  and the performance was terrible but on windows it ran normal and someone please guide me in how to properly using it and configuring it please thank you :)
Comment: No i actually haven't tried any linux games but as i watched some youtube with wine it seems pretty smooth to me even smoother than windows but i did realize that linux seems to be running on computers with alot of computing power which i don't necessarily got yet :(
Answer: Wine is not perfect especially for "intensive" programs such as games. Since its not translating every command correctly(or can't translate it at all) there will be problems. For better performance, try turning down every graphics setting you can. Also there are official instructions for wine from winehq.org detailing the process for your system. Ubuntu and other debian based systems should do this.
Purge any previous wine packages with
sudo apt purge *wine*

Next get the repo info
wget -nc https://dl.winehq.org/wine-builds/Release.key
sudo apt-key add Release.key
sudo apt-add-repository https://dl.winehq.org/wine-builds/ubuntu/
sudo apt update

Then finally install your choice of wine
Stable version
sudo apt-get install --install-recommends winehq-stable

Staging version:
sudo apt-get install --install-recommends winehq-staging

Development version(not recommended for normal use):
sudo apt-get install --install-recommends winehq-devel

Wine Gaming Problems


average calculation vs rms calculation in rectifiers

Question: In rectifier \$R_{load}\$ we calculate \$P_{load}=V_{avg}\cdot I_{avg}\$ why cant we take \$V_{rms}\$ and \$I_{rms}\$ as we are taking like in electrical calculations and also what is the use of calculating rms value in rectifier \$R_{load}\$?
Comment: I think you are taking something out of context. Are you trying to find average voltage output of a capacitor smoothed rectifier?
Comment: kollipara, I'm just projecting for a moment. Bear with me. Are you talking about a situation where there is a bridge diode rectifier and a resistor as the load?
Comment: I'm saying that load dc power calculation in rectifier r-load is vavg *iavg why couldn't we take rms values like as in electrical calculations i.e 1phase ac supply with rload
Comment: @kollipararajkumar What exactly is the meaning of "rectifier r-load" to you? Edit your question (you can do that) and use the schematic editor that is available. Draw out the schematic. Yes, I understand "1phase ac supply" and I understand "rectifier" and I understand the words themselves. I just don't understand how you put them all together. It's not working in English. Best is to shift to pictures. That will bypass any language issues. A useful answer will be based upon the details. Your question is right to ask in many circumstances. But in a few, there is a different answer.
Comment: @kollipararajkumar If you want, I can completely ignore your situation (because you've not communicated it sufficiently well) and propose for your consideration a case where a "rectifier r-load" and "1phase ac supply" would, in fact, find that "pload=vavg*iavg" as an acceptable approximation (though not perfect.)
Comment: What i mean to say is that in an upload image everywhere like in google,textbooks equation 1 is correct but why we wouldn't take equation 2 as dc power
Comment: @kollipararajkumar Your question has been completely transformed into something much more specific and meaningful. My only wish is that you rotated the image. I'll do that for you.
Comment: Sir,please clarify my doubt
Comment: @kollipararajkumar Are you reading from Malvino's lousy "Electronic Principles?"
Comment: @kollipararajkumar You'll want to use the RMS values, not the average as you show.
Comment: Yes why are we using average values for calculating power  in rectifier circuit and why we are using rms values for average power in 1 phase r load
Comment: @kollipararajkumar Because you are being taught by idiots, most likely? Malvino's book tends to create them. (I watched a teacher teach their students what you seem to have been taught.) For voltage or current measurements you use RMS to move them towards power estimates.
Comment: @kollipararajkumar Do you need a short write-up? (If you are not comfortable with integrals then some of what I'd write must be accepted and then skipped.)
Comment: In the usual way of speaking about things, the diode is the rectifier, and \$R_{load}\$ is a resistor.
Comment: @jonk i want short write.
Answer: In the case of resistive loads (loads that cannot temporarily store energy), the power is the product of its current and the voltage across its terminals. For cases where this current and terminal voltage is steady over time, this is easy since they don't vary and you can just multiply them out.
If you are only measuring one of them, whether just terminal voltage or just current through the resistor, then you have to infer the other facet. That's done easily enough and it results in using either the voltage squared or else the current squared. That's based upon various re-arrangements of the very familiar Ohm's Law.

For cases where the current and terminal voltage varies over time, you have to keep track of all the little product-bits over time (and divide by that time) to get the average (mean) power.
There is an instantaneous power, too. But it's for only an instant of time. In continuous systems, we are almost always interested in how that averages out for the period of interest. (In the case of fuses there is more of an interest in those instantaneous values.)
Note that for cases where the device's current/voltage varies over time and where we want to calculate the average power that results, we can't use the average of the device's terminal voltage or its current in order to get its average power.
For example, suppose the \$10\:\Omega\$ resistor's terminal voltage is \$1\:\text{V}\$ for \$1\:\text{s}\$, then \$3\:\text{V}\$ for \$2\:\text{s}\$, and then \$1\:\text{V}\$ for \$1\:\text{s}\$ more. We want the average power for those \$4\:\text{s}\$. The average voltage is exactly \$\frac{1\:\text{V}\cdot 1\:\text{s}+3\:\text{V}\cdot 2\:\text{s}+1\:\text{V}\cdot 1\:\text{s}}{4\:\text{s}}=2\:\text{V}\$. But the average power is \$\frac{\left(1\:\text{V}\right)^2\cdot 1\:\text{s}+\left(3\:\text{V}\right)^2\cdot 2\:\text{s}+\left(1\:\text{V}\right)^2\cdot 1\:\text{s}}{4\:\text{s}\cdot 10\:\Omega}=500\:\text{mW}\$. If we wanted a single value to represent the changing terminal voltage, where we could just use \$P=\frac{V^2}{R}\$ then we'd need \$V=2.236068 \:\text{V}\$!
Where would that come from??

RMS voltage and RMS current is really about creating just that value -- a value that somehow matches up with the DC-equivalent heating that results from a device's varying voltage/current. To compute the power, you want the DC-heating equivalent. In the above example, that's \$V=2.236068 \:\text{V}\$.
So let's just define \$V_\text{RMS}\$ as being the DC-heating equivalent of some \$V_\text{DC}\$, with the only caveat being that when we say RMS we are implying that things are ever-changing and probably not DC. But for the purposes of average power computation with a resistive load, \$V_\text{RMS}\equiv V_\text{DC}\$. In the case of DC, then these two things are exactly the same thing.
In general, this DC-heating equivalent, for voltage, is:
$$V_\textrm{RMS}=\sqrt{\frac1{T}\int_0^TV_\textrm{t}^2\:\textrm{d} t}$$
In the earlier example, we can compute this:
$$V_\textrm{RMS}=\sqrt{\frac1{4\:\text{s}}\cdot\left[\left(1\:\text{V}\right)^2\cdot 1\:\text{s}+\left(3\:\text{V}\right)^2\cdot 2\:\text{s}+\left(1\:\text{V}\right)^2\cdot 1\:\text{s}\right]}=\sqrt{5}\:\text{V}$$
(Note that the integral here was just the sum of each part.)

In the case of a sinusoidal AC voltage and a single diode rectifier (so that half of the cycles are missed), we find that \$V_\text{AVG}=\frac1{2\pi}\int_0^\pi V_\text{PK}\sin x\:\textrm{d}x\$. (The diode drop is considered zero here.) The goal for analysis is to pick a convenient period of time that makes the calculations easier. In this case, I chose one cycle of exactly \$2\pi\$ duration (timeless, but the idea is the same.) But the integral only goes from 0 to \$\pi\$, as you can see, because half the cycles are skipped. It turns out that the solution for this is \$V_\text{AVG}=\frac{V_\text{PK}}{\pi}\$.
So you really do have the right answer for the average voltage. But by now you also realize that, like a stopped clock that is right twice per day, the average voltage is almost never the right one to use with time varying signals in order to compute the power, directly. You should use the RMS values, instead.
Also in the case of a sinusoidal AC voltage and a single diode rectifier (so that half of the cycles are missed), we find \$V_\textrm{RMS}=\sqrt{\frac1{2\pi}\int_0^\pi \left[V_\text{PK}\sin x\right]^2\:\textrm{d} x}=\sqrt{\frac{V_\text{PK}^2}{2\pi}\int_0^\pi \sin^2 x\:\textrm{d} x}=\sqrt{\frac{V_\text{PK}^2}{2\pi}\cdot\frac{\pi}{2}}\$ and that's obviously just \$V_\text{RMS}=\frac{V_\text{PK}}{2}\$. (In this particular case! Do not project this into other cases.)
So you also really do have the right answer for the RMS voltage. And this is the value to use for average power computations.
Comment: @kollipararajkumar The average voltage or average current can be used where computations do not involve powers. So you can use the average voltage along with time to compute Webers for an inductance in some situations, for example. You'll find these times when you do find them. I cannot provide a glossary of every possible case.
Comment: Thank you sir i understand it clearly lastly i also have some doubt on average voltage,average current i know its meaning but i want to know where it used
Answer:
In rectifier \$R_{load}\$ we calculate \$P_{load}=V_{avg}⋅I_{avg}\$

That's incorrect. Consider the case without using an ideal diode rectifier. The power will be: -
$$I_{RMS}^2\cdot R_L$$
So, with a rectifier, only half the power is delivered to the load hence, the power will be: -
$$\dfrac{I_{RMS}^2}{2}\cdot R_L$$
Where the above RMS current value is the equivalent continuous RMS current should the diode be shorted.
If we use peak values instead we would have: -
$$\dfrac{I_{PK}^2}{(\sqrt2)^2\cdot2}\cdot R_L = \dfrac{I_{PK}^2}{4}\cdot R_L$$
This tells us that the true RMS value of a rectified sinewave current is \$\dfrac{I_{PK}}{2}\$
In other words, the power delivered to a load resistor via a rectifier diode has got nothing to do with average values (unless of course you then change those average values back to RMS or peak values of the applied sinewave).


Learning Kubernetes

Question: So I am trying to learn Kubernetes on Azure so doing the tutorial: https://docs.microsoft.com/en-us/azure/aks/tutorial-kubernetes-prepare-acr
Problem is on the login step the command does not work:

Log in to the container registry To use the ACR instance, you must
first log in. Use the az acr login command and provide the unique name
given to the container registry in the previous step.
Azure CLI
Copy
az acr login --name <acrName>
The command returns a Login Succeeded message once completed.

What i get returned is that this command is not supported in Azure CLI!

jeff@Azure:~$ az acr login --name Z-------01

This command requires running the docker daemon, which is not supported in Azure Cloud Shell. You may want to use 'az acr login -n
Z-------01 --expose-token' to get an access token, which does not
require Docker to be installed.

I have done that yet from there I still cannot seem to get logged in to move on to the next step.  Any advice?  I don't mind using token but couldn't find the proper syntax to use it successfully.  Love how their simple tutorial doesn't even work, not confidence inspiring to say the least Microsoft.
Please note I put the - in to mask the name.
Answer: So I figured out what i was doing wrong. To do this you need to download and install Azure CLI to your local OS, not run command from cloud shell in azure (which is how i prefer to do things so is my default, well Powershell really this is new foray into Azure CLI) To get the Azure CLI local go here: docs.microsoft.com/en-us/cli/azure/… It does say that at the top after rereading it, guess it was late and i was tired so missed it. I hope that helps some other newbs who miss that, enjoy! –

Learning Kubernetes


How does one find project details on Freelancer.com?

Question: I will often open up a project, such as the this one, and see an extremely vague description. However, people are giving bids for the project, so that means that they approximately imagine what it entails. Is there any place to ask questions about a project, or to find out further information about it. In fact, how do I find out more information about the project that I linked, other than the title text and the seven word description containing "payment gateway, chat window and messaging integration."
Comment: It says "in progress", 5 ½ years later. The other options appear to be "open" and "completed".
Answer: I totally disagree with "Helping Hands" above.
Don't waste your time trying to get more information.
Just run away from projects like that.
I'm a former client on Freelancer.com (no longer).
Surprising to see the level of cheating and scamming by some clients against freelancers.
Vague descriptions "pull" responses from hungry and desperate freelancers.
And vague descriptions allow nasty clients to claim later on, "You didn't fulfill all my requirements, so I won't pay you," while they get some free coding anyway.
If a client can not, or will not, be clear and specific, you don't want to do any work for them.
Answer: Sometime it happens that employer post project/job and wanted to share more details about project with some shortlisted candidates only. So in this case you can ask for more details while sending proposal.
You can start proposal like :

Can you please share more details about your requirements/Project? I would
  like to know detail requirements which will help me to decide project development
  time estimation and cost estimation.

Above is example to ask for detail requirements with proposal. You can change it depends on project.