In Guitar Hero, what visual, audio, and score feedback does the game give for hit or missed notes?

Question: In Guitar Hero, what visual (e.g. the flame), audio, and on-screen score feedback did you immediately get when you hit a note accurately? And what visual, audio (the bad note sound?), and on-screen score feedback did you immediately get when you miss a note by playing it early/late, or by not playing it at all?
Answer: This video clip demonstrates what happens when a note is missed.
There is a small twang sound along with the song volume going down for a second. Along with those audio ques, the "note highway" will shake and you will lose your combo multiplier.
Comment: @Ghopper21 Part of the game is actually enjoying the music as you're playing. I imagine the first missed note is still audible to help with that, while the subsequent notes are quieter to provide better feedback to you that you're missing.
Comment: Thanks, I can see two missed notes soon after 2:48 or so in the video. Does the note still play at all when its missed? It seems like the first missed note plays very briefly in a truncated form, while no note is played for the second missed note. Is that correct? If so, why the difference in feedback for the two missed notes?
Comment: I'm no expert but I think it may be played very very quietly. Also the game may  make the twang sound louder if you miss notes in a row.
Answer: I'll start by noting that the feedback is mostly consistent across all of the Guitar Hero games and Rock Band as well. There's a few differences between some of the later Guitar Hero games, though, thanks to some mechanics added in. In any case, I'm not going to cover the stuff added by GH:WoR.
Visual feedback (on the note highway)
When you hit a note, the gem(s) for that note will either erupt in flame (Guitar Hero) or burst (Rock Band). In the case of sustains (long notes), the note tail will light up. Hitting all of the notes in a "Star Power" or "Overdrive" phrase correctly also produces its own feedback, which is either lightning bolts (Star Power in Guitar Hero) or a yellow pulse from the note highway (Overdrive in Rock Band). In Rock Band 3 in particular, when you have a 4x (6x on Bass) multiplier without Overdrive active, the note highway will have a blue background on it (which goes away if you lose that multiplier due to a combo break).
When you miss a note, that gem will not erupt in flame or burst, and in the case of sustains, the tail will darken and become grey. If the missed note was in a "Star Power" or "Overdrive" phrase (indicated by the gems being stars [Guitar Hero] or white [Rock Band]), the remaining gems in that phrase will revert back to their normal appearance.
Score Feedback
This is pretty much straightforward. There's a combo indicator (typically right next to the multiplier and, in later games, situated alongside the note highway). hitting successive notes correctly will build it up (until you have a maximum multiplier - 4x in most cases), making an error will cause it to reset.
Audio feedback
I am assuming you haven't touched any of the mixer settings, since some of them do affect audio feedback. Whenever you break combo (for any reason at all), the instrument channel for your part is immediately lowered in volume (to a certain minimum, which is different depending on the game). In the case of drums, missing a note entirely will only lower one part of the drum mix, while erroneously playing a note that isn't there will lower the entire drum mix's volume (if my memory serves me correctly). Playing correctly will bring that part's volume back up to normal. Playing notes where there are no notes (excluding certain sections on drums) will also produce a "miss sound" (which, in some games, can be disabled).
In the case of drums, both Guitar Hero (starting from Guitar Hero: World Tour) and Rock Band have "Drum Fills", although they're done differently in the two series of games. In the case of Guitar Hero, it's large sections of no notes being present where the drummer is allowed to play whatever he feels like without penalty (and in Guitar Hero: World Tour, they would actually gain one point for every note he played in a drum fill). In Rock Band, however, fills only appear for the drummer if they have at least half of their overdrive gauge filled, and at least 4 notes must be played during the fill (3 notes on any combination of surfaces and then a green note [red if lefty-flipped] at the end) to trigger Overdrive. There is no penalty for missing a drum fill in either case, but in Rock Band, the drum stem from the song is completely muted during a drum fill and is brought back up in volume on the next non-fill note.
Comment: Thanks @KitsuneZeta. By "break combo" you mean hit a note early or late or just wrong, right? So the miss sound only plays when you play a note that's not there, as opposed to when you hit a note early/late/wrong -- in which case all the happens audio-wise is a lowering of volume?
Answer: I can add that, if you have calibrated lag, any feedback from above will be delayed by the amount of video or audio (depending on type) lag that is there (and that you have probably set.) So if you have a TV with a lot of lag, it can be a bit scary not to see the "flames" immediately after hitting the notes, even if it sounds in sync to you. I would say, with a lot of lag, trust your audio lag setting and what you hear over all else.
Other answers have pretty much described the feedback itself.


Determining number of clusters with SSE scree plot with Gower's coefficient of similarity

Question: I am researching cluster analysis, and I am interested in variables that are both categorical and continuous, for which I have read that a Gower's similarity coefficient is a good proximity measure. I am interested in first using an average linkage algorithm, and have found that some have recommended looking for the 'elbow' in the sum of squared error (SSE) scree plot as a guideline for deciding how many clusters to retain. I was wondering if the Gower's similarity coefficient (being non-metric and non-Euclidean) would allow me to create an SSE scree plot, or if that didn't make sense statistically.
Comment: SS of deviations ("error") from _what_?
Comment: SSE being the squared distance between each member of a cluster and its cluster centroid.
Comment: No, centroids call for euclidean distance. They make little sense with Gower coefficient. Search this site for "clustering criterions" and "number of clusters" for further info.
Comment: Ah, thank you, that was exactly what I was looking for.
Answer: SSE is the measure optimized by k-means.
It doesn't make much sense for any other algorithm than k-means. And even there it suffers from the fact that increasing k will decrease SSE, so you can mostly look at which point further increasing k stops yielding a substantial increase in SSE - that is essentially the vague "elbow method".
There exist other criteria such as Silhouette, Davies-Bouldin index, BIC, AIC that can be used to get an "alternative view" of what is actually optimal.
But in the end, that is just a mathematical heuristic. It may not work for real data.


How can I handle ArcMap events of CREATE, UPDATE or DELETE?

Question: As a developer I can use ArcPy (Python) or ArcObjects (.NET) to develop some extensions or tools for ArcGIS platform. But I need to handle some events. When a user connected to an Enterprise geodatabase and create an object in database table, can I handle the events of CREATE, UPDATE or DELETE? Is this possible?
Comment: INSERT, UPDATE, and DELETE are *database* events, not application events. Furthermore, in a versioned geodatabase, they are all modeled as INSERTs. The only way for an application to perceive database events is to control how they are requested.
Comment: If you're still looking for an answer to this question you can determine if the IEditor.EditWorkspace.Type == esriWorkspaceType.esriRemoteDatabaseWorkspace in the OnStartEditing event then wire the events for OnCreateFeature, OnChangeFeature and OnDeleteFeature from IEditEvents https://resources.arcgis.com/en/help/arcobjects-net/componenthelp/index.html#//00200000009s000000 which are the corresponding events in ArcMap. I should have some working C# or VB.net code if you're interested. I would have responded earlier but I was in hospital around the time you asked this question.
Comment: Thanks @MichaelStimson, I am still looking for an answer, yes. Should I create an extension for your solution? If you have some code can you share as an asnwer?
Answer: This is from working code, in this example 'timer save' a window pops up when a time has elapsed reminding the user to save, so I only use OnStartEditing and OnStopEditing events; It is important to note that this occurs in the form load event as there is an attached form:
private void TimerSaveForm_Load(object sender, EventArgs e)
{
    vSaveEditsWarn = DateTime.Now;
    this.FormClosing += new FormClosingEventHandler(TimerSaveForm_FormClosing); // to cleanup events
    IEditor pED = pApplication.FindExtensionByName("ESRI Object Editor") as IEditor;

    ((IEditEvents_Event)pED).OnStartEditing += new IEditEvents_OnStartEditingEventHandler(TimerSaveForm_OnStartEditing);
    ((IEditEvents_Event)pED).OnStopEditing += new IEditEvents_OnStopEditingEventHandler(TimerSaveForm_OnStopEditing);
    TimerSaveForm.CheckForIllegalCrossThreadCalls = false;
    this.TopMost = true; // ensure this form isn't lost under another window'
}

void TimerSaveForm_OnStopEditing(bool save)
{
    vTimer.Stop(); // System.Timers.Timer object
    StartStopButton.Text = "Start";
    this.BackColor = System.Drawing.SystemColors.Control;
    this.Text = "Auto SaveEdits";
}

void TimerSaveForm_OnStartEditing()
{
    vTimer.Start(); // System.Timers.Timer object
    StartStopButton.Text = "Stop";
    this.BackColor = System.Drawing.SystemColors.Control;
}

If you're writing a tool without a form you can wire it from the tool directly in the initializer. From the sounds of it you want to capture the On Start/Stop to grab your edit workspace then potentially OnCreateFeature, OnChangeFeature and OnDeleteFeature, which are wired in the same manner as the code shown.
When you start typing the event intelisense should finish the rest for you and offer to create the function wired to the event, I advise you to say yes and yes, not because I'm lazy but it saves mistyping and ensures that the event is correctly associated with the function.. if you try to create the function first Visual Studio may not recognize the association which will lead to hours of frustration trying to work out why an event isn't firing even though everything is spelled correctly.
Unwiring the events is a little counter intuitive, it's almost identical to the wiring but use -= instead of +=:
((IEditEvents_Event)pED).OnStartEditing -= new IEditEvents_OnStartEditingEventHandler(TimerSaveForm_OnStartEditing);

Comment: I want to run this code as a listener. I do not want to set it in a form or a tool. I want to add a listener extension on my arcmap..
Comment: https://gis.stackexchange.com/questions/148586/arcgis-sdk-c-addin-running-code-on-arcmap-startup - this will load the listener as soon as ArcMap is started.. you will want to create an application extension rather than an ITool as your active tool changes but the extension stays active http://resources.esri.com/help/900/ArcGISExplorer/sdk/doc/1595894d-154b-48f1-b03e-5f1f061931e4.htm should point you in the right direction.


How to measure strength of my own chess engine?

Question: I'm wondering how can I estimate ELO ranking of my own written engine. I figure out that I have to connect my engine with some well known engine (via UCI protocol?) to be able to play automatically many games. My first thought was to adjust ELO ranking of well known engine to finally have draw, eg. If I the result of 1000 games match between my program and other is about 500 - 500 then I'll know that my program has the same strength. The problem is that, as far as I know, we are not able to set any engine to play on particular ELO level. Do you have any other idea how to measure own engine ELO rating?
Answer: Implement UCI or Winboard protocol (just enough to play games).  Download some engines (e.g. via CCRL) stronger than your estimate and run a Gauntlet tournament in Arena/Winboard/Cutechess etc.  Hundreds of games at least.  Feed the resulting PGN output file into Ordo and it'll give you an ELO (for the time control you used).  Try different time controls etc if needed - depends on your target competitors.
https://www.chessprogramming.org/UCI
http://www.computerchess.org.uk/ccrl/4040/
http://www.playwitharena.de/
http://hgm.nubati.net/
https://github.com/cutechess/cutechess
https://github.com/michiguel/Ordo
For an initial quick ELO you could use Ferdinand Mosca's tool that makes an estimate based on your engine's performance with the Strategic Test Suite EPDs.
http://www.talkchess.com/forum/viewtopic.php?t=56653
https://www.chessprogramming.org/Strategic_Test_Suite
Answer: You can do a test on
http://www.elometer.net
This is a test based on problems
Comment: Those problems were designed for humans, not computers. Computers play chess very differently from humans.


is there a word or phrase for the family unit that only includes "immediate family" but not spouses and children?

Question: This word would include me, my brothers and sister as well as my mother and father.  It would not include my wife or kids.  And as a bonus, is there a word for the group that would only include myself, my wife and kids?
Comment: They're your ***birth family*** - as opposed to what I'd call your ***spousal*** family if pressed (the family you and your spouse create when you're an adult, as opposed to the family you were born into).
Comment: Indeed, I am talking about shared domicile, more or less.  I am trying to have someone fill out a form that is relaxed and conversational. I am looking to group the data on the people they are related to, but trying to keep it in small, manageable bites, if you will.
Comment: I should note that you cannot have an answer that includes "brothers and sisters as well as mother and father" (**parents and children**) on the one hand, but excludes "kids" (**children**) on the other hand. If a child is included, then a child will always be included. (Perhaps you had meant to say "it would not include my wife, if she were not a parent *my* children, or her children, if *I* were not a parent of them.") Similarly, "my wife and kids" also includes the siblings of each child.
Comment: Are you talking about genes or laws or shared domiciles? Genetically your first-degree relatives are those who share 50% of your genetics with you, which under most scenarios means parents, children, and full siblings — but under unusual cases can include various others as well.
Comment: The question seemed relatively clear, until the reference to a 'shared domicile' in one of the OP's comments made it confusing. Is the idea that, if a respondent lives in three-generation households, only a part of the household should be listed? If a respondent lives only with his spouse, should the answer be left blank? It is often difficult to be 'relaxed and conversational' and clear at the same time.
Answer: As for your second request:
Nuclear  family:

a family consisting of two parents and their children, but not including aunts, uncles, grandparents, etc.

(Cambridge Dictionary)
Comment: Why would this be downvoted? Because it only answers a part of the OP's question? Where that part is concerned, this answer nails it.
Comment: Agree with @lumbrjak. M-W defines *immediate family* as a person's parents, brothers and sisters, husband or wife, and children, and *nuclear family* as a family group that consists only of parents and children. This nails the first part, as the OP sought a word for himself and his parents, brothers, and sister. It also nails the second part, as the OP, his wife, and their children also constitute a *nuclear family*. Whoever downvoted this answer is a total joke. I'll do my part to undo the damage.
Comment: Nuclear family is excellent for the second answer, but I am looking for something more colloquial/conversational, if possible.
Comment: The terms *nuclear family* and *immediate family* do not distinguish between **two** families that a person may belong to: (1) oneself, one's parents, and one's siblings, and (2) oneself, one's spouse, and one's children. Both (1) and (2) can be characterised as nuclear and as immediate; the OP's question is seeking to distinguish them.
Answer: I agree with @FumbleFingers. It can be birth family.
Birth family is normally used to distinguish from adoptive family, but it refers specifically to parents and siblings (excluding wife and kids).
Answer: For the term for "group that would only include myself, my wife and kids," I disagree with nuclear family in this case, because that describes a type of family.
The clarification in comments added "I am trying to have someone fill out a form that is relaxed and conversational," and a form would not say "Give the names of your nuclear family". While nuclear here has a specific meaning ("forming a nucleus") it's entirely possible that it will be misunderstood, if it's understood at all in this context.
For this context, immediate family is to be preferred, I feel.
This term appears in OED describing what a "first-degree relative" is.

Designating a member of a person's immediate family, as a parent, sibling, or child. Chiefly in first degree relative.

The term itself is not defined in OED, although immediate is:

Said of a person or thing in its relation to another: That has no intermediary or intervening member, medium, or agent; that is in actual contact or direct personal relation.

While that definition might be taken to include parents or siblings, in normal usage it includes only those who are living together in a household.
And actually, the word household might also suffice.
Comment: My "immediate family" could be the family unit in which I'm a child (or was a child if I'm now an adult), or the family unit in which I'm a parent. OP is asking for terms that distinguish between those cases.
Comment: But a *household* can include more than two generations of a family, and can include people not in the family.
Comment: In that case, it's ***household.***
Comment: Which is exactly why *nuclear family* isn't right either, because that tends to mean "family members within the household". Perhaps there just isn't a term which is universally applicable.
Comment: @AndrewLeach I have to agree.  Can possibly use household.  I had used the phrase "family: growing up".  Not great but I think it communicates the distinction.  I appreciate all the input from everyone.  Will mark this as the answer.


Crumble added to muffins before baking

Question: I put a crumble on my blueberry as recipe called for, why did they caved in?  Could it be the altitude?
Comment: More info would be helpful here. A recipe, perhaps a picture, what is your altitude, and have you ever made them before? Welcome to Seasoned Advice, BTW.
Comment: The tops of your blueberry muffins have deflated--is that the problem?
Comment: yummmmmmyyyyyy!
Answer: If you're asking if the crumble is the source of your problem - it isn't.
Without a recipe and some indication of how you mix and bake your muffins, it is difficult to determine the cause of your cave-ins.  This is a common problem with muffins and cupcakes, though.  The most likely culprits are:  (1) too much liquid in your batter, (2) oven not hot enough, (3) chemical leavener is spent or you used too little, (3) you use too much leavener, (4) you didn't bake them long enough, (5) you used too much batter for each muffin (filling the cups too full), & (6) overmixing.
If you are following a respected recipe carefully and you know your leavener is fresh, then please make sure you are cooking in an oven that has been pre-heated fully to the temperature in your recipe - that temperature probably shouldn't be below 375°F (and, of course, altitude could be an issue here - how high-up are you?).  Most importantly, mix your ingredients only long enough for them to just barely come together (remember that it's OK if little traces of unincorporated flour are still visible) - mix by hand if you have used an electric mixer in the past.  Finally, avoid filling the cups in your muffin tin more than 2/3 full - using more better doesn't always make larger muffins - at some point, the muffin loses its ability to support the doming of the center.

Crumble added to muffins before baking


What's the deal with צרויה?

Question: Found out recently that צרויה as in (Yoav Ben Tzruyah) was actually Yoav's mom and not his father. Why is Yoav constantly referred to as the son of his mother, when the Tanach norm is to use their fathers' name? And what do we know of Tzruya? Any midrashim mention her?
Comment: Fun fact, she is the most mentioned woman in tanach.
Comment: @DoubleAA gonna start using that one ;)
Answer: In the commentary by the anonymous student of Rasag to Divrei Hayamim 1:2:16 he writes:

""and their sisters Tzruyah and Avigail" - And Tzruyah's husband was S'rayah, and not S'rayah who fathered Yoav, father of Gei Charashim (DH 1:4:14), but S'rayah son of Asael who lived in the time of David, and for this reason he named his son Asael, brother of Yoav,1 after his father Asael.2

His emphasis regarding the identity of S'rayah is interesting because Rav Hai Gaon wrote (Shaarei Teshuva (Teshuvot Ha'geonim), Siman 19):

"And that which you asked regarding Yoav ben Tzruyah, why was he named after his mother, for his father's name is known, as it says "S'rayah begot Yoav, father of Gei-Charashim", but since his mother was the sister of the king, he was named after her, so that his greatness would rise out of her..."3

So we see that in the Gaonic period there were two rival traditions regarding the identity of Yoav's father: Both knew his name was S'rayah, but there were disagreements on which person in Tanach the name referred to. In any case, we learn from Rav Hai's statement that Yoav was named after his mother because her yichus was more impressive than his father's. The rest of the siman includes other examples of this.
Similarly, Rabbi Yitzchak Notovitz wrote in Shulchan Ha'ma'arechet, Introduction, 4:

"It is the way of the text to attribute people after their brothers who are more important than them, such as "older brother of Yefet" (Beresheet 10:21), "wife of Nachor, brother of Avraham" (ibid 24:15), and among women: "sister of Nachshon" (Shemot 6:23), "sister of Aharon" (ibid 15:20), as well as attributing a man after his mother, [such as] Betuel son of Milkah, wife of Nachor (ibid 24:15), Avishai son of Tzruyah and Yoav son of Tzruyah, Yesha'yah son of Atalyah (Ezra 8:7), and so on."

More info on Tzruyah:
Her name, which might be a fusion of Tzori (balm) and the name of Hashem, is one of the circa 60 personal names containing contracted forms of the name of Hashem from the time of David and Shlomo (for more info, see Prof. Yoel Elitzur's essay here, in particularly nn. 16-17).
According to Malbim on DH 1:2:15, Tzruyah and Avigail were step-daughters of Yishai. Their biological father was named Nachash. After he died, his wife married Yishai. However, according to the gemara in Bava Batra 17a and Shabbat 55b, "Nachash" was a nickname for Yishai.

1 One of Yoav's brothers, killed by Avner (Shmuel 2:2:18-23).
2 It should be noted that the commentator spells S'rayah's father's name as עשהאל, like his Yoav's brother, but in our Tanachim we have עשיאל as the father's name.
3 This would make Yoav and his siblings the nephews of Otniel ben Kenaz. Incidentally, according to the gemara in Temurah 16a, Otniel's real name was Yehudah and his brother's name was Shimon. This is likely a reference to Shoftim 1:3, usually taken as a reference to the entirety of the tribe of Yehudah and the entirety of the tribe of Shimon, despite the use of singular forms.
Answer: She was Dovid Hamelech's sister as the passuk in Divrei Hayomim 1:2:16

וְאַחְיֹתֵיהֶ֖ם צְרוּיָ֣ה וַאֲבִיגָ֑יִל וּבְנֵ֣י צְרוּיָ֗ה אַבְשַׁ֛י וְיוֹאָ֥ב וַעֲשָׂהאֵ֖ל שְׁלֹשָֽׁה׃

Rashi adds:

ואחיותיהם צרויה ואביניל. מפני כבודו של דוד שהיו בני אחותו גבורים ואנשי חיל ושרים כך מפורש:
Answer: The Malbim [IISamuel 17-25] (https://www.sefaria.org.il/II_Samuel.17.25?lang=he&p2=Malbim_on_II_Samuel.17.25.1&lang2=he) writes about Yoav (and his two brother) כי אביו לא נודע בשם. This could either mean that his name wasn't known, or that he wasn't even worth mentioning by name.
The Metzudas Dovid (https://www.sefaria.org.il/II_Samuel.17.25?lang=he&p2=Metzudat_David_on_II_Samuel.17.25.4&lang2=he&w2=all&lang3=he) there suggests as a possibility that Tzeruya was a half-sister of David, as David's mother had previously been married to someone called Nachash, and Tzeruya & Avigail (mentioned in that Pasuk) were daughters of that marriage.

What’s the deal with צרויה?


Angular and linear velocity of a circle

Question:
Let's assume I have a circle of radius $r$ and I apply a constant force at a point on the circumference of the circle that is perpendicular to the distance vector which goes from the centre of the circle to the point. If I wanted to find how fast it is rotating (angular velocity) at a specific time, I can integrate the acceleration vector ($F/m$) to get the velocity vector and then do the cross product between the distance vector from the centre to the point and the velocity vector (and divide by $r^2$) to find the angular velocity. Now if the circle is tied down (or fixed) at it's centre, it will simply rotate in place. If it's not fixed, would it be correct to assume that on top of spinning around it's centre of mass, the centre of mass will also be moving? If so, how can I find the velocity at which the centre of the circle is moving (not rotating). We're not talking about a circle that is rolling like wheels, we're talking about a circle that is flat with the ground and we can assume that the circle has no friction.
Comment: Hi and welcome to physics SE. Please, consider rephrasing your question, because it is quite unclear right now. If you can include some pictures of what you're asking, that would help quite much as well. Thank you
Comment: ok I posted a picture, I don't know if it's clearer now. I want to know if the circle is not held at it's centre of mass, would it rotate in place or would it also move forward/backward. In other words, in this example, would you end up with the circle only rotating or also having a linear motion? Also how would you find the value of the linear motion if it does move.
Comment: Now I'm getting you, you're saying that you have a solid circle, right? I thought you had a particle in circular motion. Okay. Then the other answer is fine. One last thing: is the force constantly upwards or constantly perpendicular?
Comment: In reality the circle is actually a cylinder, but  I just want to know how it works in 2d first (on a disk, or a ring, doesn't matter at this point, I'm just trying to get a feel of how it moves when the center of mass is not tied down). You can see the problem as a cylindrical boat floating on water, with the force being an engine (assume mass of engine is 0) that is attached at that specific point and pushes the boat with a force perpendicular to the hull. I don't want to go into the details of the entire system since i still don't understand the basic as explained in the picture.
Comment: The force is going to be constantly perpendicular, so you can assume that as the circle rotates, the force shifts. So if it rotates by 45 degrees, now the force applied is at 45 degrees from the original one.
Answer: The center of mass moves with an acceleration given by $\vec{F} = m \vec{a}$, just as if it were a point mass.  You can then integrate $\vec{a}$ to find the position of the center as a function of time.
I should also note that the method you describe will only work for a hoop where all the mass is concentrated at a fixed radius $r$.  It will not work for a solid disk, for example.  The better method is to find the torque exerted by the force about the center of mass $\tau$, use Newton's Third Law for rotations ($\tau = I \alpha$) to find the angular acceleration, and then integrate that to find the angular velocity as a function of time.
Comment: Just want to clear something up. Once I find the angular acceleration (and angular velocity), in which direction does the centre of mass move? In the +x/-x, +y/-y or some combination of those or does it stay fixed? From the looks of it, it seems like the hoop should both rotate and move, kind of like how it works when you throw a baseball where it both spins and moves in a direction.
Comment: @SamuelSnerden It moves just as a point particle would move under the same force.  In particular, if the center of mass is initially at rest, then the object's trajectory will be along a straight line parallel to the force.
Comment: So we simply shift the force to overlap directly on the center of mass, find the velocity from that and that would be the direction it should be moving correct?
Answer: This is a problem of rigid body mechanics. The movement can be separated into trasnlational motion and rotational motion.
Translation of the center of mass.
The center of mass moves LIKE if all forces were acting on it. No matter where the forces are, the center of mass moves like if all forces were acting on the center of mass.
Then, in addition, you can have motion around the center of mass. In fact, you can describe rotation around any point, but it is usual to refer rotation to the center of mass, and your particular geometry is quite suitable for it.
To know how it rotates around the center of mass, you need to calculate the torque of the force w.r.t. the center of mass. Then, use the formula $\tau=I\cdot \alpha$, where $I$ is the moment of inertia of the disk, $\alpha$ is the angular acceleration, and $\tau$ is the torque.
Comment: okay, that's exactly what I was asking for. So just checking to make sure I understand it correctly, if we have a force, to find the translational motion, we simply take all the forces and apply it at the center of mass, then find the net force and integrate to find the velocity correct?
Comment: Yes, that's pretty much it. If you that, you'll find that the CoM also moves in circles, which makes sense
Comment: perfect thank you so much.

Angular and linear velocity of a circle


How to add songs to ipod from ubuntu 13.10?

Question: How can i add songs to my ipod from ubuntu 13.10. Is there any softwares similar to itunes.
I tried gtkpod ipod manager for adding music to my ipod but it crashes every time i try to add songs to ipod.Is there any other way to add songs to ipod?
Answer: The answer appears to be No! You cannot load music on your iPod with 13.10. I have tried every program I could find, and none of them seem to work. gtkpod crashes so often it is unusable. It is not clear to me that it does anything. Rhythmbox crashes frequently also. With Rhythmbox you cannot create new playlists on the device. They have removed every facility you used to use to do this. I cannot find a way to do it. Banshee deleted all of my playlists and also crashes a lot. Something is very wrong with this release. (This subject has not been good since about 10.04.) Best bet: go buy a Mac! I can't get Ubuntu to work with an iPod.
Comment: you are right.when i tried to add music from rhythmbox it crashes and my ipods album arts got the place of other songs and the shuffling system didn't work.so i had to restore my songs from windows
Answer: The answer for me was to install Banshee Media Player. I formatted the ipod for windows first using virtualbox and Windows 7 with the apple software- If this is a fresh out of the box ipod you will need to do this and remember to enable USB2 devices on your virtual machine. After that you should be able to drag things your Banshee library onto your ipod - ensure you have enabled the ipod support plugin in Banshee. Rhythmbox has never been that great with ipods so I have not tried that yet on my install.
Answer: it is possible but you will requires software like crossweaver which enable you to install windows software like itunes and your good to go.


Access Windows File System From Linux OS

Question: My sister's computer has stopped working.  I am not entirely sure what the problem is, but I think it is a Windows/software issue.  She really just wants to retrieve the pictures off it.  I am wondering if I could install a Linux OS (CentOS is the only one with which I am little familiar) on the free space and access her Windows file system.  I know there are several 'what ifs', but is this a possibility?
Comment: A safer alternative might be to use a live Linux distribution on a USB stick or some other removable media, then fetch the pictures to another removable media, e.g. external hard disk.
Comment: as SamiLaine said, I would certainly look at booting from a LiveCD or a USB disk before trying to install an OS on the disk's free space.
Comment: Have made a boot disk on SystemRescueCD.  I look forward to trying this out.  I hope it works.
Answer: Yes !
Better use a rescue distribution like SystemRescueCD.
It includes already all utilities you need including partition backup and windows File system support.
It's easy to use. and you can just run it from an USB Flash Drive.
Answer: First you'll have to make sure which hard disk and partition Windows is occupying, let's suppose it's on /dev/sda1.
Open a terminal, run
<code># mount -t ntfs /dev/sda1 /some/random/empty/directory/
</code>
Your Windows files should be accessible from the directory then.


Best karate book

Question: Is there any book advices for learning karate. Previously I have trained in kickbox , muay-tai.I want to start learning karate.What are the best books for learning karate ? Thanks in advance.
Comment: The answer will inherently be ephemeral. Tomorrow (and every day after that) someone will publish a karate book.  And the best book for learning Tang Su Do might not be the best book for learning Isshinryu.  The best book for a beginner will not be the best book for someone who has studied three other related arts.  The best book for a 98lb 78 year old marathon runner with arthritis won't be the best book for a 210lb weightlifter with a history of ACL tears.
Comment: As written, the question is both opinion based and too broad, but I suspect it could be refined to be better if the asker narrows down exactly what he is looking for.  There was a meta discussion related to this here:  http://meta.martialarts.stackexchange.com/questions/75/book-recommendation-wiki
Comment: Voted to close as being opinion based. Could also be closed as too broad.
Comment: The best "book" for learning any martial art is the official syllabus of that style.
Answer: Although not a "technique and kata" writer, I would recommend anything by Dave Lowry.  He is an excellent writer and will explain so much more about the etiquette of a Japanese martial art.
Answer: Are you interested in the technical aspects of karate, or in the philosophical aspects?  I've found that seldom are both well represented.  I would say a good mix of both can be found in Karate: Technique and Spirit by Tadashi Nakamura.  Nakamura is the founder of Seido, an offshoot of Kyokushin-Kai, but his technical demonstration in the book is well matched by his discussion on the role that martial arts can play in life.

Best karate book


Averaging a big number of pixels within a several km radius

Question: I work with ArcMap software and now I have the aim to average individual pixels within a several km radius from daily data for at least 1 month. So I made the grid with 4 km step (the step size is not important for the question) and now I have to average pixels according to the described method. How do you think what the tool from ArcTools window I should use for this?
Comment: Averaging for very large windows...this is exactly what the integral image transform is for. After performing this quick transform, you can extract the average of any sized (rectangular) shaped neighbourhood in linear time (three operations). It's how this particular problem is handled in the field of computer vision and graphics.
Answer: you can use focal statistics if you have the spatial analyst extension. This will compute the average of pixels in a moving window. if necessary, you can then resample at a lower resolution with nearest neighbour interpolation.
Comment: there are of course other software even or more efficient than ArcGIS for raster data (e.g. OTB, IDL), but what I mean is that you can use ArcGIS tools without adding the data in the data frame (which takes a long time, especially if you buil pyramids). for instance, right click on the tool and select "batch", or use an iterator in model builder, or use arcpy inPython script.
Comment: Thank you, but the problem is I work with a large amount of images and have to analyze them simultaneously so I tried to find the tool which could help to load at least few files to obtain a statistically significant signal, but focal statistics works just with one.
Comment: you can batch process all your images without adding them to ArcMap, this will speed up your process.
Comment: Sorry, but how I can batch process my images without ArcMap? Do you mean another software?
Comment: O my God, you are right with batch process, it seems it's the same I hoped to find out! Thank you very much! I also wanted to make specific - is Focal Statistics suitable for the averaging pixel values near the nodal points of the grid for the chosen area?
Answer: After ReSample to a larger pixel size (which, by the sounds of it, you have already done), then use CellStatistics (in spatial analyst toolbox/Local), which will derive a statistic from multiple raster inputs.
Maybe I am misunderstanding your problem. CellStatistics will give you the average for a whole pile of rasters per pixel. Perhaps your problem is in the re-sampling or allocation of pixels to locations. If the latter, would buffer (of the source locations), feature -> raster (with a unique id, OID(?) perhaps), then zonal stats to get averages per zone, then cellstats to average the pile of rasters....
Comment: You are right, it's necessary to use Resample to enhance the spatial resolution, but CellStatistics gives just mean values for pixels but I need to get averaged ones for some radius to indicate the source of emission.
Answer: I hope my answer can be helpful for you, first of all you need know what is Focal Statistics (Spatial Analyst)
The Focal Statistics tool performs a neighborhood operation that computes an output raster where the value for each output cell is a function of the values of all the input cells that are in a specified neighborhood around that location. The function performed on the input is a statistic, such as the maximum, average, or sum of all values encountered in that neighborhood.
Conceptually, on execution, the algorithm visits each cell in the raster and calculates the specified statistic with the identified neighborhood. The cell for which the statistic is being calculated is referred to as the processing cell. The value of the processing cell, as well as all the cell values in the identified neighborhood, is included in the neighborhood statistics calculation.
The neighborhoods can overlap so that cells in one neighborhood may also be included in the neighborhood of another processing cell.
after that I think this example that described in ArcMAP Manual can be useful also,

moreover if you have more than two raster and you'll run Focal Statistical in Batch mode follow this way shown below images:
[step1]
[]3
[Step2]

Finally when finished process you can by reclassify (spatial analyst)  get table  form result rater, I think you need to do reclassify.


FMC run for GFCI receptacle?

Question: I have a water heater room 5x8 that needs a GFCI receptacle added to the ceiling for a hot water recirculating pump. The heater is large and obviously hard plumbed in so cannot be moved and rigid conduit can not get around the back of it. Can FMC cable be used to get around it and strapped to the walls? This is San Diego commercial building. Work will be done professionally but I'm looking at the options. I've tried looking at the NEC but get lost.
Thanks
Answer: Nec Article 348 allows FMC to be used as a conduit system. However, NEC 348.12 (1) does not permit the use of FMC in wet locations. So assuming you water heater room is not wet during normal operations FMC can be used. However, if you determine that the wiring might cause a shock or burn hazard during non-normal working conditions some AHJ might have a problem with it.
Due to the fact that this is probably a short run and so material cost would not be a real factor, I would suggest you run it in LFNC "carflex" or LFMC "sealtite" and avoid any conflict.

FMC run for GFCI receptacle?


Memory details of a process

Question: How can I get the memory details for a process running on linux?
I need to find out specific details like stack size, heap size of a process.
Answer: You will find everything about your process in the /proc/PID directory. Especially in the smaps file where you will find the stack and heap size currently used.
Documentation here
Answer: For ubuntu: Grep returns only useful information
$ java -XX:+PrintFlagsFinal -version | grep -iE 'HeapSize|PermSize|ThreadStackSize'
For windows:
There is no grep in Windows, instead, we use findstr.
C:>java -XX:+PrintFlagsFinal -version | findstr /i "HeapSize PermSize ThreadStackSize"
The -XX:+PrintCommandLineFlags is used to print out the values that modified by VM only

Memory details of a process


If the General Counter-Spell exists, why are there specific counter-curses?

Question: If a combined Finite could stop Grindelwald's extremely powerful Protego Diabolica, and various spells like the ones in the Duelling Club orchestrated by Severus Snape and Gilderoy Lockhart, why are there specific counter-curses, counter-jinxes, counter-hexes, and counter-spells? If Finite was that powerful, why would there be a need for these other spells?
Comment: Possibly because only a small number of wizards and witches can cast a spell that powerful? Why do you need a million different types of keys when you can buy a battering ram that works on 99% of doors?
Comment: The key word is "combined". It's easier to cast a specific counter-curse than walk around with an entire team of Finite-casters.
Answer: Magical Arms Race
We know Finite Incantatum (Finite) can end many spells.  Likewise "protego" can block many spells.  But "many" is not the same as "all".  We likewise know that there's at least one spell, Avada Kadavra, that is unblockable by any means.  We also know that specific counter-jinxes/curses/spells exist.
Ergo, we can assume that there is some subset of spells that, for whatever reason, bypass finite and/or protego.  That makes them exceptionally good combat spells, since they not only ignore the "normal" general counter-spells, but more importantly can "trick" an ignorant opponent into trying to block them anyway because if you don't know "Spell X" bypasses protego/finite, you stand there and try to block it with protego/finite, get hit, and lose the duel.  On the other hand, if you know the specific counter-curse for "Spell X" not only can you stand there and block it (and therefor be able to fight back easier than if you were dodging all over the place) but you also gain some element of surprise against your attacker (who may not know the spell has a specific counter-curse or assumes you don't know it). I would argue that the more exotic spells we see in wizard duels (dumbledore v voldy in Book 5 for instance) are spells with specific counter-curses that bypass the "normal" defensive spells.  Which is why when harry watches Dumbledore v voldy he doesn't see signs that spells are ceasing (as in finite) or the bubble/shield of protego. Instead he sees both wizards conjuring up specific counters, because the normal ones simply would not work.
I should state that this is all conjecture as I don't believe the answer is said outright anywhere, but there's enough evidence for me to accept it as true until proven otherwise!
Comment: I like that answer. If Protego is a shield, it works against metaphorical arrows, swords, maces and so on. Then somebody pulls a magical variation of a gun. Your regular shield doesn't work, you need magical version of modern body armor and even then it will hurt and some ribs might get broken but you'll survive! Voldemort and Dumbledore were on completely different level compared to most wizards. Voldemort conjures a tank, Dumbledore sends a tank mine. And so on.


Customs when rechecking bag in the EU

Question: I am a German citizen and fly to Switzerland from the US with a layover in Paris, where I need to retrieve my baggage and check it in again. Do I need to go through customs in Paris and if so do I need to pay taxes on items I bought in the US even though I am not really staying in the EU?
Comment: I did buy two separate tickets yes
Comment: Did you purchase two separate airline tickets? If you bought one ticket, your bags will normally be checked through to Switzerland and you won't see them in Paris or take them through customs in Paris. If you bought separate tickets, that's a different story.
Comment: Where are you resident?
Answer: Depending on the airlines you're flying with, you might be able to check your luggage in all the way. Call the airlines to check.
If you have to pick up your luggage, then you will have to go through Customs. They might or might not ask you anything. French Customs officers in CDG are notoriously both lazy and aggressive. If they go through your luggage – an improbable but not impossible event – telling them you're just transferring might help, but it's not a very strong argument. Since you're entering the country, there's no way to prove you're not handing over some of your belongings in Paris. Especially not to a grumpy Customs officer.

Customs when rechecking bag in the EU


Better to use multiple email address fields or 1 field for invites?

Question: I am working on an interface that asks the user to add 5 or more email addresses. The invite email that gets sent is the same for all invitees. Is it better to use 1 field for the user to add all the email addresses or multiple individual fields for each email?
Comment: Probably the biggest problem with one field is keeping the addresses separate (especially if the copy-paste something like `"Fred Bloggs" `. If you _do_ go with one field, I'd probably make it a multi-line edit box and insist on one address per line.  Using _separate fields is probably cleaner still, but you then have to consider add/delete buttons etc.
Answer: One input will be much user friendlier especially if this filed will instantly tokenize and validate the input as it is done in almost all email clients
Comment: This would be the way to do it, if you can manage it. To slightly simplify the processing, you could have a text-box where you enter _new_ email addresses, that on completion get added to the "To:" list as "boxed" entries as shown above.
Comment: This is basically how it works, inline input box without the border. Solution is tricky to implement, but [there are controls](https://bootstrap-tagsinput.github.io/bootstrap-tagsinput/examples/) one can adjust to save implementation time.
Answer: Same as Jurijs, I would go with one field only. However, I'd use a textarea, clearly  explaining that each email should go on one line.
The reason for this is that is:

simpler
users probably have been exposed to this many times
cleaner
users will quickly understand what to do if they want to delete or modify a record.
a 5 lines textarea will quickly transmit an affordance, which is more complex on single line fields
scanning is really fast, as opposed to single line, or multiple lines with different fields

From the stakeholder view, it's really easy to implement, just one field and that's it. Having multiple lines will require controls for each field, and will have a way bigger friction. Not only you'll have a lot of control, but... what happens if the user wants to delete the 3rd field?

Will she think the 4th will move up?
will she think she'll have to edit rather than delete?

Simply put, you'd be leaving room for confusion, which means you'll lose time testing things that might not need any testing.
On the other hand, a single textarea will have very low friction, if any. Hence, my suggestion would be: go with a textarea and one email per line.


Solutions for videos and subtitles in Mac OS X

Question: What is the best way to merge a .srt subtitles file with a Movie, and have it subtitled online. I have a mp4 file and I've already made the subtitles in a .srt file. I've used the SubMerge software, but when I upload the generated mp4 to vimeo, there's no subtitles. It seems that subtitles generated by this software are some kind of meta-data inside the video. Is there any way to RENDER the subtitles whithin the video, so it can go online in any video website?
Answer: Submerge is what you asking for, you must be doing something wrong.

Go to File, select "Open file" and navigate to the video file you want to add the subtitles to.
Click the "Choose" ikon in the top left side of the main windows and navigte to and select the .srt file
The program now renders the subtitles, which actually means it's converting the text to graphics in order to embed them into the video.
assuming that the size and sync of the font is what you want, klick the export wheel and select your desired format. I use iPhone or AppleTV. Both are h264 and will upload fine to most video services.

Hope this helps.
/Ulrik
Comment: I did exactly this in this movie: http://vimeo.com/6094673 - as you can see, when I uploadit to vimeo, the subtitles are not shown on the vimeo flash player. But if you download the video on the same page (right corner, bellow) you'll see the video with subtitles
Comment: I finally discovered what was happening. If you export in Submerge using .mov format, it will add soft subtitles. Using mp4 export format, it creates the hard format, what I wanted. I've just uploaded the generated video to vimeo and the subtitless are there! THANKS!
Answer: What you did is…
you used -> Soft, non-destructive subtitles
I love them a lot because I can attach Japanese, English and German subtitles
(and also choose between several audiotracks). This is extremely flexible.
If you want the uploaded movie to always appear with subtitles attached you
need to export them hard burned / hardcoded. Like Ulrik said, all the pictures must be
processed aka the whole movie will get rendered again with subtitles.
Here are some software tips:

iSubtitle does the same thing
as Submerge, but maybe you can
handle it better. Try the demo.
Muxo for Soft Subtitles only :)
Handbrake  Great free
alternative to all things video
related, you can also to these hard
burned subtitles with it. Check it
out!

…learn more about hard burn subtitles here.
Comment: So, submerge doesn't have the option to create Hard subtitles?
Comment: I'm trying to use Handbrake, but it doesn't render subtitles. Is there any special way to do it? There's no field where I can choose the .srt file to be attached.
Comment: BTW, iSubtitle 1.4 is bugged in Snow Leopard. When I try to export the movie, it crashes...
Comment: Submerge should have no problem creating them. In fact it used to only to do in the beginning.

I doesn't remember exactly the settings for this, but you should be able to export it "flattened" or to "render subtitles". If one of those two options works I deserved a thumbs up from you :]
Comment: I finally discovered what was happening. If you export in Submerge using .mov format, it will add soft subtitles. Using mp4 export format, it creates the hard format, what I wanted. I've just uploaded the generated video to vimeo and the subtitless are there! THANKS!


A function $V : \mathbb{R}^2 \to \mathbb{R}$ is a (logarithmic) potential

Question: I'm looking for references given some sort of inverse problem in logarithmic potential theory. That is, given a function $V : \mathbb{R}^2 \to \mathbb{R}$, what is a sufficient (and perhaps necessary) condition for $V$ to be a (logarithmic) potential, that is that there exists a (signed) Borel measure $\mu$ such that
$$
V(x) = -\int_{\mathbb{R}^2} \log|x-y|{\rm d}\mu(y).
$$
This question seems rather natural, but I haven't come across anything similar in the literature for the moment. Note that I'm looking for solutions to this problem that might make sense only in a weak sense (i.e. distributions etc.). In fact, I'm also considering the Coulomb potential in higher dimension $d \geq 3$, so that references for this case (if any) are welcomed !
Comment: Do you insist that the function $V(x)$ is really defined for all $x$, or you want to treat $V(x)$ as a distribution? The problem is that there are signed Borel measures, even with compact support for which the RHS is not defined at all points but only defined almost everywhere (as an integrable distribution). This problem becomes easier if you restrict it to positive measures: then $V$ is defined everywhere if you allow $V(x)=-\infty$ at some points.
Comment: @AlexandreEremenko Thank you for your comment. I should have given more information on $V$. It's an integrable function w.r.t. to some measure (not necessarily absolutely continuous w.r.t. the Lebesgue measure). As such, it could potential take the value $-\infty$. Now, I think I might be able to restrict my attention to positive measure, since I have some *vague* results which tell me that **if** $V$ is $C^2$, then it is superharmonic. As such, the measure which generates it (if any) must be positive ! So, in this case (positive measures), what results are known considering this question ?
Answer: There are two kinds of conditions:
a) the local one: distributional Laplacian of $V$ must be a signed measure (difference of two non-negative distributions). I do not think that there is a simpler restatement of this condition.
b) the first global one. Once you know that the distributional Laplacian is a signed measure $\mu$, you want to know that the integral $P(z)=\int\log|z-\zeta|d\mu$ converges in some sense, at least for almost all $z$. Convergence of this integral almost everywhere implies convergence quasi-everywhere, so $P$ is defined on the spheres a. e. with respect to the surface measure.
c) the second global one: if a) and b) are satisfied you want to know that
the difference $V-P$ is zero (rather than some harmonic function).
The easiest way to ensure this is to check that
$$\int_{S_r}|V(z)-P(z)|d\sigma\to 0,$$
where $S_r=\{ z:|z|=r\}$ and $d\sigma$ is the normalized surface measure on the sphere. (This simplifies when $n\geq 3$, you can remove $P(z)$ from the integral.)
Everything simplifies if you restrict your class to potentials of positive measures.
Then for a) you can simply check that
$$V(z)\leq \int_{S(r,z)}V(\zeta)d\sigma,$$
for all $z$, and all $r>0$ where $S(r,z)$ is the sphere of radius $a$ centered at $z$ and for $n\geq 3$ check that
$$\int_{S(r)}V(z)d\sigma\to 0,\quad r\to\infty.$$
b) can be skipped in this case. These conditions will ensure that $V=P$ almost everywhere. If you want everywhere, you need to add the condition that $V$ is upper semi-continuous.
When $n=2$ it is slightly more comlicated. You can find $\mu(R^2)$ by the formula
$$\mu(R^2)=\lim_{r\to\infty}r\frac{d}{dr}\int_{S(r)} V(x)d\sigma.$$
and then $c$ becomes
$$\int_{S(r)}V(x)d\sigma-\mu(R^2)\log r\to 0,\quad r\to\infty.$$


6/3 NMB in non-metallic conduit?

Question: I'm running a 50A circuit using 6/3 NMB from my interior panel to a hot tub. I've got the required GFCI protected disconnect within direct line of sight of the tub (about 15ft from the tub). I have 3/4" LFNMC that is planned to use once the wire penetrates to the exterior of the crawl space. My question is....is it acceptable to run this cable through the conduit if I remove the romex jacket? It would need to be in the conduit for about 8ft from the crawl space to the disconnect and then about 25ft or so to get to the connection inside the hot tub. Thanks in advance for your help!
Answer: Don't make your life harder than it needs to be!
First off, shucking NM of its jacket is no good, because the wires inside NM cable aren't marked properly for individual use.  Second, pulling NM through outdoor conduit is unacceptable because NM is no good in wet areas due to the paper separator layer between the jacket and the wires (which wicks moisture up the cable, leading to hard-to-troubleshoot failures later), and all outdoor conduit is considered a wet location by NEC 300.9:

300.9 Raceways in Wet Locations Abovegrade. Where raceways are installed in wet locations abovegrade, the interior of these raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations abovegrade shall comply with 310.10(C).

Third, there's absolutely no reason to make your life this hard: pulling 4 6AWG THHN wires through your conduit (hot, hot, neutral, ground) will be far easier than trying to jam a cable through there.  So, I would simply get an appropriate amount of 6AWG THHN (black, white, green is fine) and use that instead.
Comment: If you're unable to get white THHN at the local big box store, you're allowed to mark the black wire (an 'ungrounded' conductor) as a white 'grounded' conductor using white electrical tape. The green 'grounding' conductor must be bare or green. You can't re-mark that one.
Comment: @ndemarco that only works for 4AWG and fatter wire, not the 6AWG the OP is using
Comment: @ndemarco yes, you are not allowed to remark individual wires in conduit.  Remarking white to hot  is only allowed in cable.  All the remarking rules go out the window for #4 and larger, because electrical supply houses have made clear they don't want to stock 3 colors of the big stuff.
Answer: You can shuck it if and only if the internal wires have markings, and the markings are appropriate for this use.  For instance if the interior wires said "THWN-2" that would be good enough.  But they won't.   Partly, THHN has a magical nylon outer coating which makes it slippery for pulling through conduit. Without that, good luck!
You're not allowed to assemble the conduit around the wire.  So you can't slide the conduit on one stick at a time.  You must finish the conduit pipe, then pull the wire through it in one shot.
NM will not fit in 3/4" conduit
Aside from the complete horrorshow of trying to drag stiff NM cable through conduit, it simply will not fit.  You would need bare minimum 0.85" inside diameter, and that is not available from any 3/4" conduit of any kind.
And as ThreePhaseEel says, you can't use NM cable anywhere outdoors, so that's the end of that.
Outdoor-rated UF-B won't fit. Worse.
The outdoor rated version of NM is called UF-B cable. Aside from the horrorshow of pulling that through conduit, UF really, really won't fit.  It needs a pipe minimum 1.68" inside diameter, and that means we need to kick up to 2" conduit.  Are you kidding me?
Enough with the masochism.  Back to the store the cable goes.  Get yourself THWN-2 wire.
Or use cable as cable is meant to be.
If you're none too thrilled about returning already-cut NM cable, then it's a simple matter. (but next time, buy the wire last!)
You can transition from one wiring method to another in any (large enough) junction box.  Run the NM cable as cable inside the house.  When you get near the outdoor transition, go ahead and install a junction box indoors.    Continue in conduit from that junction box.  In that conduit (junction box through disconnect through tub), run THWN-2 type individual wires.  The neutral must be white or gray.  The ground must be bare, green, or yellow/green.  The hot wires can be any other color(s) including black-black.
You will neeed 35 cubic inches in this box, so use a 4-11/16" deep square box.  The junction box must remain accessible forever, so it'll need to be in an attic, basement or just an unsightly blank cover somewhere.  You could put a recep in that cover, but you can't feed it from this #6 cable so you'd need to bring in a separate feed for the recep.
Liquidtight isn't
There simply is no such thing as water-tight conduit outdoors.  All outdoor conduit pipe is presumed to be 100% full of water 100% of the time. So liquidtight doesn't buy you anything unless Code requires it, but it still is not counted on to keep out water.  The moisture defense is in the skin of the wire itself.    Further, by being a flexible conduit, you don't get to use it as a ground wire as you could with regular metal conduit.
The GFCI
There is no requirement to have the shutoff switch also be a GFCI.  These are totally separate functions: the shutoff needs to be near the hot tub, and the GFCI needs to be anywhere it can protect the circuit. I for one am a fan of putting GFCI indoors (e.g. as a GFCI breaker in the panel) then use a plain disconnect switch. Being indoors is easier on the electronics.
Comment: Yes, I understand spools available for purchase are cross listed, but we know not all projects get inspected, and I felt it best to discourage the thought that it still may be safe if it's just missing the ink. We don't know that they don't make THHN specifically only for use in the miles of NM-B that they make.
Comment: You're throwing around THHN and THWN-2 and just a point to prevent confusion on the part of the OP, THHN is rated damp location, THWN-2 is wet location. Cut sheets for NM-b used to specify THHN conductors, it seems now they have removed references of wire type and only specify 90°F, but it is quite possible the actual conductors still may not perform safely in a wet location.
Comment: @NoSparks virtually all THHN today is cross-listed THWN-2.

6/3 NMB in non-metallic conduit?


When does Big-O notation apply to functions with arbitrary constants?

Question: I am having trouble understanding if I can apply Big-O notation to the following circumstance.
Suppose that
$$Mxk_0=\sum_{j=1}^{M}xk_j, \hspace{0.5cm}\mbox{where $0<k_j<1$.}$$
Regard all $k_j$ as being arbitrary in their collective interval. This leads me to believe that $k_0<1$ must be a constant. Now, let $g(x)=xf(x)$. We have
$$\frac{g(x)}{k_0x}=\frac{1}{k_0}f(x).$$
Thus, $$\frac{1}{k_0}f(x)=O(f(x)).$$
Is this correct? I think it uses Big-O notation correctly, but I don't feel satisfied in justifying it because $k_0$ feels weirdly fickle.
Comment: If $k_0$ is actually constant then yes, this is true.
Answer: You might be worried that since $k_0$ can be arbitrarily close to $0$, the factor $\frac1{k_0}$ can be arbitrarily large. It's still valid to carry out $O$-notation reasoning treating $\frac1{k_0}$ as a constant, though. The point is that even if $\frac1{k_0}$ is really large, as long as we hold it constant, eventually $x$ will get big enough (or small enough, depending on which version of $O$ we're using) that it doesn't matter. One can formalize this argument and prove it from the definition of $O$-notation.
Still, it's often useful/informative to keep track of which parameters the constant factor hidden in the $O$ expression depends on. E.g. a paper might present its result as "$g=O(f)$, with a constant factor that does not depend on $\epsilon$", which is a stronger statement than just "$g=O(f)$".
Comment: That was my worry, you are exactly right. This answer is helpful. Can you explain what is meant by "$g=O(f)$, with a constant factor that does not depend on $\epsilon$." What exactly is meant by $\epsilon$?
Comment: Oh, $\epsilon$ is just an arbitrary parameter that might appear in the definition of $g$ or $f$. Something like "For all $\epsilon>0$, there exists an algorithm $A_\epsilon$ that runs in $O(n^3)$ time (with a constant factor that does not depend on $\epsilon$) and outputs a solution whose score is at least $(1-\epsilon)c$, where $c$ is the optimal score."


Can't put .mov file in iMovie

Question: I'm trying to drag a .mov file into iMovie from Finder, but nothing happens when I try to drop it into the videos/images section. How do I put it in iMovie so I can edit it?
Comment: does it turn green with large Plus sign as you hover over iMove ? If not try moving around till it does.
Answer: You should be able to drag the .mov file into iMovie without any problems, so I'm wondering to where within iMovie you're actually trying to drag it?
Perhaps the best bet is to use the commandI shortcut to open the Import window. Once open, use that to navigate to your video file and import it.

Can't put .mov file in iMovie


How to remove Brush Size limit in sculpting

Question: In Sculpt Mode, the brush size is limited to 500 px which is good in normal monitors, but is not good in 8k monitor. It looks like a little brush in 500 px size, and I need to change the size by typing number which isn't  intuitive. How could I remove the lock, and let it go higher when pressing the F key ?
Answer: In sculpt mode, under the Brush menu, switch the radius unit from View (measured in pixels) to Scene (measured in scene units).
Comment: although im pretty much agreed that the current answer would be scene units currently but after reading "blender lake" answer it was hard for me to choose the true answer cause logically the true answer is that blender isn't capable of doing such thing currently , BUT your answer helped me alot didn't considered that one
Answer: Currently, you can't unlock the brush size limit in Sculpt Mode without changing the source code of Blender by yourself, because the feature of unlocking this limit is still under development.
In the year 2022 January, Joe Eagar was about to add this feature. However, after one year and a half, no further progress was reported. And now, Joe Eagar is no longer working for Blender development. He probably resigned.
I recommend you to contact Blender developers to push and realize this feature by commenting here.
Comment: i mean i actually can go above 500 pixels by typing the number ....


How can I quickly save an unflavorful curry?

Question: I prepared an Indian curry last night for this evening's meal.  The dish I made is based upon a lamb curry recipe, replacing the lamb with pieces of aubergine.  The main ingredients are aubergines (eggplant), yoghurt, ginger, turmeric, cumin and chilli.  Note that when I was adding in the aubergines, I was not paying close attention to the original recipe's quantities.
After cooking it, I gave the dish a taste test, and the flavor is rather bland. I think the problem may be having too low a ration of spices to aubergines.
 Tonight, I will not have much time to fix the curry's flavor before dinnertime.  Does anyone know what the best way would be to quickly add more flavor into this pre-made curry?  Is it as simple as adding some raw ginger and spices, or is there a better approach?
Comment: I can't really tell from the ingredients if this is supposed to be an Indian or a Thai curry... which probably speaks to why it doesn't taste like much... care to clarify?
Comment: @Aaronut - Indian. Have edited my post.
Answer: Indian curry traditionally has - in addition to the ginger, turmeric, cumin and chili (I assume you mean chili powder) that you used - a generous amount of garam masala, coriander powder, and garlic.
Sometimes you'll see "curry powder" used in recipes instead of garam masala; they are similar but not exactly the same.
Either one of these would be fine, and arguably the most important missing ingredient here. I'm not even sure you could legitimately call it a curry without one of the above.
Depending on your spice tolerance, you might need to add more chili powder as well.
Note that most spices in a curry will need to be heated before they'll really release their aromas (and therefore flavour), so you can't just add them cold, and I definitely don't think you'd want the taste of raw garlic/ginger in your curry, even if it is presently tasteless. Give it a good simmer after adding some garlic (powder is fine) and garam masala or curry powder and you might be able to salvage it.
Or you could try heating the new spices dry, for a very short time, to give them a bit of a head start aroma-wise; just be very careful not to burn them.
Comment: Good answer, but I have found spices to work better in oil than dry. I'd heat the new spices in a tablespoon or two of oil, then add only a bit of liquid (the choice of liquid can have important effect on the taste too) and simmer. That should produce an aromatic sauce you can mix in the curry. Also, consider adding something umami to the spice mix, this is probably the biggest difference from lamb.
Comment: Many thanks. That saved the curry nicely, turned out the be the nicest one I've ever made. I then went on and made another, even nicer one afterwards!
Comment: Sounds like a plan. Just a couple of questions. By dry do you mean without oil? Also are you including garlic in the spices to dry heat? Would I do this over low or high heat?
Comment: @MongusPong: You don't want to heat fresh garlic dry; garlic powder is OK. As for the heat, it's not really that important - medium or high is fine - what's important is that you take it *off* the heat as soon as it starts to get fragrant. You can use some oil too as rumtscho says, if you're not comfortable heating up spices by themselves.
Answer: if it was me, I'd blend garlic and ginger (and fresh chillies if you want) to a paste into a small blender/coffee grinder (not one you actually use for coffee though), I'd warm some cumin and coriander seeds in a dry pan, then grind them down in a pestle and mortar.
Then I'd heat a table spoon of oil, add the spices back to it, fry for a few seconds, then add the garlic/ginger/chilli paste, cook that for a few mins on a highish heat and add to the curry.  Then I'd season with lemon and salt/pepper.
you could also chop a handful of fresh coriander leaf and/or fresh mint and stir that through, which will give you a nice freshness and should compliment the lamb nicely.
If you have it, some tamarind loosened with a bit of hot water is a nice alternative to lemon, with a more savoury sourness, and can quickly add a bit of punch to a curry.
Comment: Mouth watering. Once nice touch is to stir in some lime pickle. It adds a sour, fruity tang.
Answer: First suggestion is to check your seasonings. Adding various amounts of sweetener, salt, or acid (vinegar, lemon/lime juice, etc.) is the easiest way to bring out the flavors already there. Remember that the key when seasoning is to bring out the flavors already there - your dish shouldn't taste like salt, sugar, or acid. You can certainly try and add more spices, but that won't make a difference if your seasoning is off.
Second suggestion would be to remove some of the aubergine. By itself it doesn't have much flavor, so removing some of it to bring the rest of the ingredients in balance might help.
Comment: I've made curries that were too bland and they just needed more salt for the curry flavor to come out.
Answer: In Indian curries, you almost always fry onions, and add the spices to the frying onions (and continue frying for not too long.)  It sounds like you're making "bangan bharta" like this recipe.  Notice this step:

Heat oil in a pan, add garlic ,green chilli and chopped onions and fry
  over medium flame until light golden brown. Add red chilli powder,
  garam masala powder and turmeric powder.

That's what you should do, and add the onions to the final product.  If you already have onions in your dish, just do this with less onion.
Also, don't forget the salt.  Salt can really affect how much you can taste the other spices.
Answer: If you have one medium bowl or dish that you need to rescue, try the below steps:

First cut an onion into small pieces.
Cut a medium size of the tomato (To make it tangier).
Now take two tablespoons of oil, heat in a pan and put a half teaspoon of cumin.
Put, the cut onion in the pan. Just add salt for taste and cover it with a lid. Keep the lid closed till the oil float on all the sides. All this should be done in low flame.
Now after the oil floats on all the side add cut tomato and stir it with a ladle.
close the lid and cook for 3 mins. Now add your bowl of curry to the pan and mix it well and keep the lid closed till the oil floats on all the sides in slow flame.
Now the dish is cooked. Add some chopped coriander leafs.

The dish is ready to serve !!!
Comment: Could you clarify what you meant by "oil floats on all the sides" please?
Comment: What is mean was, when oil is separated in curries normally after you have cooked spices or sauces for ~10-15 mins. You can tell by seeing "bubbles" appearing and the oil by making a thin layer on top of your sauces/curry and it floats on all the sides.
Answer: I recently made an eggplant curry using yellow Madras curry, onion, potato, sweet potato, fresh tomatoes, ginger paste, and coconut cream.
I sweated the onion first in some butter, added the dry spices and heated them before adding the harder vegetables (potato & sweet potato) and then added the softer tomatoes and eggplant with the coconut cream and let it all simmer.
My curry was great but still felt it was missing something; the next day I added heated it in a pan with a little lemon juice & a handful of fresh cilantro at the end.  The acid and hit from the freshly wilted herbs added dimension and helped the other flavours pop.  Lemon and cilantro are versatile since they can play nicely with either an Asian or an Indian spice palette.
Note:  the photo I have attached is from the first day I made it without the herbs added.


How do I create and configure a hidden service hostname?

Question: I read on many tutorials and websites that Tor will generate the hostname for you and put in a certain file, however it is not doing it and when I asked why, someone replied saying that is not what happens but that you need to create and configure it yourself. How do I do this?
Answer: Assuming the program that generated the hostname for you is working properly, it should give you 2 files, once called hostname and the other called private_key. Put the 2 files in one folder, for example /home/user/tor_private. The next step is to add a reference to this folder in your torrc file. Open your torrc file (it is in /etc/tor/torrc when you use some sort of GNU/Linux), and add the following two lines at the end of the file:
HiddenServiceDir /home/user/tor_private
HiddenServicePort 80 127.0.0.1:80

Finally, don't forget to tell your webserver (e.g. apache2) about the folder where you are putting your website files (your HTML files). Then, you'll have to restart Tor, and your webserver (e.g. apache2) afterwards, and your site will become accessible from the Tor network. The onion address of your website can be found in the hostname file you've put in /home/user/tor_private.
Few recommendations you should be aware of:

For security reasons, it is not advised to run Tor using the root user. Instead create a user for Tor. Some Linux distros such as Debian automatically create a user called debian-tor when you install the Tor package. Use the Tor user (you created or already created by the system) to run Tor.
Make sure only root or the Tor user have read access on the folder /home/user/tor_private. So the permissions on the folder should be 700.
Don't put your website files inside /home/user/tor_private. That folder is only for storing your private key. Put them somewhere else accessible by the webserver.
Don't share the private_key file with anybody. If anybody gets his hand on this file, you can take over your onion address and you'll loose ownership to your site!
Comment: My issue had been that tor was not generating either of those, and I had nothing else to generate them with. I now solved the issue, thanks for trying to help.
Comment: @CAllende Could you give us insights how you solved it?


Using Find my iPhone to track my daughters phone

Question: Can I use find my iPhone to track my daughters phone if we each have different apple ids?
Answer: Only the main Apple ID on the device (the one that has iCloud backups available) is available to log in to Find my iPhone. Any secondary iCloud accounts added to the device can not be used to track the device.
If she doesn't mind that her Apple ID won't be the main one, then yes, you can set it up with your Apple ID as the main one and that will work fine.
Also, if she doesn't mind, you can log in with her Apple ID.
If not, you can use Find my Friends since this works across multiple Apple IDs.
Comment: Keep in mind, this is partially incorrect. You can actually sign into *any* Apple ID when *viewing* FMI from the backend. So, the OP can sign into the daughter's Apple ID account (from iCloud.com or the iOS app) and then see the location of her phone. As for the config, both devices should be signed into their own accounts.
Answer: The consolidated answer is: YES, you can use Find My iPhone to track someone else's iPhone, so long as you know the main Apple ID and password that is being used on that phone.  To track the phone, install the Find My iPhone app from the App Store on your phone, then log into the app using the Apple ID and password being used on the other phone (i.e., your daughter's Apple ID).
If you don't mind your daughter knowing that you are tracking her location, then the Find My Friends app (also from Apple) is a better solution for tracking since it allows you to track multiple phones simultaneously without having to log into the their Apple IDs, and allows geofenced alerts (e.g. "alert me when my daughter leaves school").  One potential downside is that using Find My Friends will also share your location with your daughter (and anyone else you are tracking).
Answer: To directly answer your question, you may use Find My iPhone to track your daughter's iPhone using the Find My iPhone app that you can download from the app store - without any consequence to your own Apple ID that is in use on your device. All you need to do is sign into her Apple ID in the app, and it should show her device (as long as Find my iPhone is enabled on her device).
When using the Find my iPhone app, you can keep your Apple IDs completely autonomous, and all you need to know is her Apple ID.
Like @grgarside mentioned. Find My Friends would probably be a better option either way since you can set up geofence notifications, and such.
Answer: "Track" may not be the most accurate term.  You can "locate" (or find) your daughter's iPhone, but only if she has the app and iCloud enabled.  If she turns it off on her phone, then you will not be able to locate her phone (or her).  The app does not "track" in terms of showing you where she as been, from location to location. In other words, she could have it on when she's home, turn it off and go to the mall with her friends, then turn it back on when she gets home and you will not know - other than the app will indicate an "old location" when it attempts to find her phone and the app/ iCloud are turned off.
Answer: Answer for ios 13+:

On your daughter's phone, open the Find My app.
Select Share My Location
Select yourself to share her location.

https://support.apple.com/en-us/HT210514


In Outlook Office365 web interface, how to find all calendar events with attachments?

Question: I do not have access to the desktop application, only the web interface of Office365.
I commonly receive calendar invites with attachments, but cannot find them in my inbox after accepting the invite. If search in the calendar, there is a filter flag to find attachments, but it requires a search term and leaving it blank or wildcards return nothing.
The only way to consistently find them is to go directly to the event in the calendar.
I understand that this is easily done in the desktop application. Is there any way in the web interface?
My ideal would be a filter group that shows all my calendar events with attachments so that it is always up to date. Is this possible?
Answer: According to my research, I'm afraid that it is not achieveable. We could only use the filter to search among events with attachments.


3D Symbology for a Model Farm in ArcScene

Question: I am working on visualization of a model farm I have developed consisting of various types of grazing land, cropping areas and other. As I have constructed it myself, I don't have an image with it for display. I am looking for symbology options I can use in ArcScene to give it a realistic touch. I have tried to use picture but it doesn't work well. Here, the screenshots below shows the things I've tried with 3D texture fill sumbol and picture fill symbol. I don't have many options in the texture one and it looks all the same if I use the grass1 or grass2 as symbols for grazing or cropping land. As this is a created farm, not an actual one on earth, so I obviously don't have any aerial images or satellite images for the farm area, which would have been great, therefore, I am not sure how I can make it look real. I want to make a fly over animation from this once I make it look more real. I have draped a DEM on the farm landscape in ArcScene. Any ideas?
Comment: What do you mean by 3D symbology? Your second image appears to have draped your land use classification over a DEM. Are you looking for realistic textures to use instead of the flat colors used in the current symbology? Or are you wanting a current aerial/sat photo of the area which you can still see with your land use classification on top of it? Can you provide a screenshot of what you tried and didn't like?
Comment: Thanks Chris, you made my day again.......Yes I wanted to increase the size of the tile and by increasing the value in x and y, it worked! It looks more real now.
Answer: The problem is partially going to be a function of scale. Depending on the scale of your map, any given texture might look incorrect because of the pattern/detail it's trying to represent. Easiest to see just by going to Google maps and turning on sat imagery and zooming in and out and noting how crops just become a blur. In your example, if you like the individual tile but not the grid pattern it produces, try upping the x and y scale in the dialog box you show in your last image. That controls how big a single tile is, so with fewer (or one) tiles you may get the effect you want.
You could also go onto Google maps (or other imagery) and locate a land pattern you like, perhaps even at the right scale to match your map, screenshot it and crop it to a square tile, and use that instead of the included textures - also playing with the texture tile scale. Note that if you use this method it can be tricky getting a pattern that tiles together nicely without obvious seams (as evidenced in your first attempt there).


Should I add salt to my sauerkraut recipe if I add vegetables?

Question: I am following a sauerkraut recipe which calls for a specific amount of salt. They say I can add other vegetables, like carrots. Do I need more salt if I add more vegetables?
Comment: Are you making sauerkraut from scratch (fermenting it)?
Answer: If you are fermenting sauerkraut, then you should keep the salt content the same if you add other vegetables. The salt helps keeping undesirable bacteria in check, so you probably don't want to "dilute" it. Increase the amount of salt so the ratio between cabbage/vegetables and salt stays the same.
TL;DR: Treat any additional vegetables like cabbage when calculating the amount of salt.
Answer: The salt amount usage will depends to the weight of the vegetables and water.
For example, if your current recipe calls for 2 lb. of cabbage, but now you are planing to do less cabbage and substitute that amount with carrots, then you don't need more salt.
However, if you would use 2 lb. of cabbage (according to recipe) and wish to put 1 lb. carrots into your mix, then naturally, you will need more salt, since you have to use more water to cover the additional vegetables.


Is there a way to make a default roaming profile using Server 2008 on a 2003 domain?

Question: This domain uses roaming profiles for these specific users. I want to have files in the profile of every profile created. On a regular machine, I would put it in the All users directory. I can't do that here because it is a roaming profile. Thoughts?
Answer: Script it in Group Policy.  If I'm not mistaken, group policy logon scripts execute as the system account - this allows you to put in a script that copies files to the all users folder without serious concerns about permissions.  Reference the %allusersprofile% environment variable when creating the script to copy files - for example:
copy "\server\share\path\to\file to\copy*.*" "%allusersprofile%\desktop"


Unable to open chest in Assassin's Creed IV

Question: I have looted every chest in AC4 Black Flag. But the last chest at location 688,904 won't open. I walk to the chest, there is a loot option. But when I press the button to loot Edward just kicks the chest and nothing happens. Is this a bug? Please help.
Answer: Use the Eagle Vision then open the chest normally. It worked for me!
Answer: You might be on the wrong side of the chest. Try walking around. Although the loot button might look activated, you need to see the indicator above the box before you can loot it.
Also make sure you're at the right box. Try locking onto the box location on your map. Then you can see your distance from it and make sure you're at the right one.
Answer: Eagle vision on, right infront of the chest and hold the loot button. The eagle vision slows Edward just enough to complete the action before he returns to the hidden position. Takes a few kicks but it gets there eventually
Answer: Try moving the camera to the opposite side while pressing the 'loot' button. It should work. Just keep pressing the 'loot' button and move the camera to the opposite side or keep the camera rotated.


How to address a professor in letter?

Question: When writing letter to an academic professor (not necessarily from student to professor), what is the appropriate way to address his/her title?
I have seen in letters using
Dear Prof. X even when the addressee is not a full professor
Dear Dr. X though, knowing that the addressee is a full professor
Dear Mr/Mrs X though, knowing that s/he has an academic title
Comment: All faculty (in the US) can be properly addressed as "Prof. X".  We faculty are all professors, even though we are not all Professors.
Comment: I used to have an instructor who specifically didn't want to be addressed as "professor" because he wasn't a professor. He asked us to just call him by his first name. Though clearly I wouldn't suggest doing that unless they explicitly tell you to.
Comment: It also depends on the campus culture -- I went to St. John's in Annapolis, and the faculty were all called Tutors, and the *only* one we called Dr. was also a cardiologist.  Everyone else (including students) was Mr./Ms.
Comment: For this question to be useful you need to specify what country you're in.
Answer: The appropriate way to address someone is with their proper title. In your question, it seems you know what the title should/should not be. If you know, use it. If you don't know, it's generally safer to err on the side of formality.
While I personally prefer (and request) everyone to refer to me by my given name, I do feel it a little strange when someone I do not know / have never met addresses me in writing by my given name. Perhaps I am old fashioned but I expect introductions to be formal (and better to be too formal than too familiar) and then quickly get to preferred ways of addressing (i.e., to use my given name).
When corresponding (in writing or electronically) I would look to the signature. If they wrote:
Dear Professor Schmoe:

Blah blah blah

Sincerely,
John

-----
Dr. John Doe
Agri-science Department
University of Whatchamacallit

Then I would write back
Dear John:

Thank you for your letter. Blah blah blah.

Sincerely,
Joe

Comment: @andrea In the example in my answer, where I signed my letter "Joe" then I consider it completely acceptable for him to respond "Dear Joe" - however, to be even more clear, I _could_ add "Please call me Joe." However, since I've signed the letter "Joe" I would expect him to interpret that as an invitation to use my first name from here forward. If he continues to use "Professor Schmoe" I would think either he was a bit too formal or he didn't read the signal (my signature) clearly enough.
Comment: FWIW this is the convention I go by as well. If someone signs a letter or email with their first name only, that is an implicit invitation to address them by their first name in any future written communication. If they sign it with their first and last name, or their title and last name, that indicates you should stick to formal forms of address. I think this convention is widely known about.
Comment: I follow exactly the same rules. The only liberty I allow myself sometimes is to write "Prof. Schmoe" instead of "Professor Schmoe" in the very first letter if I am sure that he knows of me and wouldn't mind to communicate with me informally. However, I never start with "Dear John" or abbreviate in any way in an "official" message (like job application, etc.) that may be filed with the office rather than read in private even if the addressee is among my personal friends. Also it is better to make an error of addressing a secretary as Prof. than that of addressing a professor as Mr.
Comment: @earhling, at this point (i.e. after the original email and your reply, where you used a more informal `Dear John`) would you consider appropriate if John wrote back starting with `Dear Joe, thanks for...` or it's still better to use again `Dear Professor Schmoe, thanks for...`?
Answer: This is a sticky question.  Preferences for academic titles varies between countries, institutions and individuals.
In the US, any individual employed in an instructional capacity by an institution of higher education can be properly addressed as "Professor Smith", even if his or her official title is "Assistant Professor", "Lecturer", "Adjunct Instructor", etc.  Moreover, any individual holding a doctoral degree can be addressed as "Dr. Smith".
Of course, these two cases often overlap, and you are left to decide whether to use "Professor" or "Dr.".  The pattern I've observed is that at institutions where only some of the faculty have doctorates, those who do are more likely to prefer "Dr."; whereas at places where almost everyone has a doctorate, they will all prefer "Professor".
I think the safest default, and the one I most commonly see, is

Dear Professor Smith,

I would not abbreviate "Professor" as "Prof.".  It sounds too much like an annoying student saying "Hiya, prof!"
Comment: Note that in Germany (and possibly elsewhere) it is common practice to address someone with their full title (sometimes even in speech). For example, Professor Doktor Zweistein...
Answer: This depends on a number of factors, not limited to the country the professor is in, the actual title, the type of correspondence (formal/informal), and the professor's personal preference. In the U.S. in computer science, for instance, virtually everyone goes by first names, almost regardless of university affiliation or rank.
I would avoid Mr./Ms. if you know there is an academic title (and these days, unless you have demonstrable evidence that the person prefers it, never Mrs.). I happen to prefer people use my first name, but I have to admit that it does tweak me a little bit if someone who should know better calls me "Mr." instead of "Dr." ("I didn't spend six years in evil medical school to be called 'Mister', thank you very much!") I shake my head whenever I get an email from my PhD alma matter when they refer to me as "Mr." -- of all the places or people in the world that should get this right, they don't!
If you're in a country where it seems to matter (Germany comes to mind), call the person's office and ask explicitly (or figure it out by going to the professor's web site or the school site). Otherwise, I suggest that for a formal never-been-introduced letter you should use either "Dr." (if applicable) or "Professor" (for all ranks of professor), or if you're in a field where first names are standard, go with that. For unofficial correspondence, you will be safe with the formal titles, but shouldn't have a problem with a first name.
Comment: The only caveat I would have is unless you're in a field where the first name is the _universal_ default, don't address somebody by the first name until invited! (The "Du/Sie" issue in Germany is still a big thing in Germany, for instance—and violating that kind of protocol can get you into a lot of trouble!)
Answer: I am from Russian culture where the word "professor" is only used with PhDs. Many years ago (in 1998), in USA, I was hired at a community college as an Adjunct Instructor to teach a class. I had only a Bachelor's degree at the time. Every time, when I had college correspondence where they addressed me "Professor", I felt that I did not deserve that title. Later, I knew that it was quite a common way to address college instructors.
Now, I have had Master's degree for 18 years. It still doesn't feel right if they call me Professor. I don't think it is a commonly used title anymore, though. When it is appropriate, in correspondence, I would put "M.Ed." after my name, like when writing to a university with an inquiry.
I am not very excited with being addressed Ms., however there is no other way, so it is as it is. When I address someone, and I know he or she has a PhD, I will always address them Dr. (last name). PhD is the highest educational degree and a big personal merit - it has to be recognized and observed in a title.
As for the "du/Sie" in German, or "ты/Вы" in Russian - there are no guesses, grey areas, or "maybe". You call du/ты  only your husband, wife, close friend or a child. All other unknown people in formal environment, business people you call only the polite Sie/Вы.
Answer: Before writing be aware about: the context- formal vs informal (friend or someone you have been in touch long ago vs cover letter for a journal); In the latter context you always should address the person in cause by the academic position: Professor (be sure about his/her position- in the web - it is not difficult).
Answer: I will address Dr. X (if I know that my professor is holds a doctoral degree) and
I will address Professor X (if I am not sure that he is holding doctoral degree).
Not all professors hold doctoral degree I guess.
Comment: This is the start of a good answer, but perhaps if you can find a style guide to support this, or recommend HOW someone researches whether or not someone is a PhD?
Comment: In the UK this almost works the other way around - you know that most staff hold doctorates, but you may not know if they are professors, and indeed the odds may be low (that title is used really differently on the two sides of the atlantic). So I tend to default to "Dr X" as the least likely to offend.

How to address a professor in letter?


Who are John Uskglass and the Raven King in Jonathan Strange and Mr.Norrell?

Question: I think the series has some serious ambiguity for those who didn't read the book!
Who are John Uskglass and the Raven King? (In the series they said they are two different persons.) What do they want? Are they good men or not?
Answer: They're different names/titles for the same person.
John Uskglass is his human name - whether or not it's his real name, the one he was born with, is unknown, but there's nothing special about the name itself unless you know who it is. The title of "the Raven King" sounds much more impressive and mystical. Which name you use might indicate your stance towards him: "the Raven King" is a term of respect, whereas "John Uskglass" makes him sound more normal and mortal.
It's hardly feasible to write everything we know about him in the space of a Stack Exchange answer, but you can read more information about the character at the Strange & Norrell wiki.
As for whether he's good or bad, I don't think that question really makes sense. He transcends those concepts, like the fairies he grew up among. We might say the Gentleman with the Thistledown Hair is evil, but the truth is rather that he's neither good nor evil - he's just different, alien to us and our concept of morality. He's capricious, uncaring, and simply inhuman in the most literal sense. The same could be said of the Raven King. His acts might be seen as good or evil, but really he's neither.
Comment: Thank you... But about the last paragraph... I really thought he "meant" to be devil... as they were using words "depraved" and "cruel" for him.
Answer: In the book, John Uskglass was the Raven King, a historical figure who, like Arthur, is expected to be capable of returning.  He was a human child who was raised in Faerie, and whose magical powers exceeded all other humans.  (For, as the book points out, Humans are weak in Magic but strong in Reason; Fairies are the opposite.)  After re-emerging into the Human world, he gained a kingdom, presumably around Yorkshire (I believe Childermass comments about how the people there remember him).
At no point do I recall him being described as "evil" (as opposed to "good"), but he was powerful and inscrutable.  He is remembered as a protector of his people.
I cannot find my copy of the book now, but the footnotes do contain a lot of what is known about the Raven King.
Comment: Thank You... I found the dialogue made me puzzled: Mr.Norrell: "Surely John Uskglass is his name? That is the name of the Norman aristocrat who the Raven King, our John Uskglass, claimed as his father.
But that is most disputed."
Comment: When the child emerged from Faerie, he took a human name, as he'd been raised without one; the name he took was that of his putative human father.  But, of course, after you've disappeared into Faerie for some number of years, it's not completely clear you are who you say you are.  And in any case, anyone dealing with Faerie keeps their name private, as names have power - so for the Raven King to take on the name "John Uskglass" after his father was practical, controversial after time (because just "taking" a name always is), and meaningless in the large scheme of things.
Comment: Which is another reason he's known as the "Raven King"; it reflects that his identity is a little fluid and he prefers to be addressed by reference than by true name :)
Comment: Thanks for detailed answers