Feature extraction other than convolutions for images?

Question: Are there approaches other than convolutions to learn features from images? Has there been any research to use approaches such as hashing (e.g. p-hash, diff-hash etc.) in lieu?
Answer: Some more complex and better outcomes are those that include the MPEG-7 developed by the MPEG group.
These descriptors specify the video standard in question. They are split for color, shape, texture and movement.
1. Color Descriptors
Color Space. Specifies the data type of the color space in which they are expressed or work other color descriptors. Color spaces that it contemplated are: RGB (Red, Green Blue), YCrCb (Luminance, Chrominance), HSV (Hue, Saturation, Value), HMMD (Hue, Maximum, Minimum, and Difference).
Color Quantization. This descriptor defines a uniform quantization of a given color space.
Dominant Color(s). This descriptor is the most suitable to be used in images, or regions, in which a small number of colors is sufficient to characterize the information of one determined region.
Scalable Color. This descriptor consists in a color histogram in the HSV space. It is useful in image to image comparisons or searches based on color characteristics.
Color Layout. This descriptor allows representing the color spatial distribution within the images in a very compact way, so the recovery is realized with great efficiency.
Color Structure Descriptor. This descriptor characterizes the color distribution in an image. It builds a color histogram, which assigns most importance to the colors that appears most often and spread across the image. GoF/GoP Color (Group of Frames/Group of Pictures). This descriptor is an extension of the Scalable Color descriptor, which, unlike the latter, is applied to video sequences (a collection of images) instead of only an image.
2. Texture Descriptors
Homogeneous Texture. This descriptor emerged as an important tool when looking for and choosing within large collections of images of great visual similarity.
Texture Browsing. This descriptor specifies the perceptual characterization of one particular texture, and pretend be similar to the characterization that a human eye makes, according to regularity terms, coarseness and directivity.
Edge Histogram. It is a descriptor that gives us information on the type of contours or edges that appear in the image.
3. Shape Descriptors
Region Shape. The object´s shape in an image may consist of a single region or a set of regions, so this descriptor is useful for this type of characterization.
Contour Shape. It is characterized by very well represented contour features which facilitates subsequent search and retrieval; it is robust to motion, to occlusions and to different perspectives; it is extremely compact.
Shape 3D. The Shape 3D allows to describe in details the shape in 3D. This tool is very useful today due to continuous development of multimedia technologies.
This was taked from my paper: The MPEG-7 Visual Descriptors: a Basic Survey
Best regards
Answer: I think your question addresses the fact that convolutional neural networks utilize convolution and not some other mechanism. This answer addresses other feature extraction techniques you can use on image. In general, there are a number of other feature extraction mechanisms you can look into.

Histogram oriented gradients. Counts the occurrences of gradients in an image and generates bins. These bins can be then used directly as features.
Color data. You can extract color histograms of various granularities and use this data to train a model.
Hough Transform - Can identify shapes and lines and other spatial features.

On top of these we also have numerous techniques on top of convolutions like gradients, curvature finding, corner detection, and ridge finding.


Stereo or mono keyboard effect?

Question: I've finally found a decent 'swirly Rhodes' sound, using keyboard and an effects pedal. The problem is now that when recording, or on stage, I prefer to go stereo, as that gives other sounds - strings, Hammond, etc.- a much better airing. Trouble is, the phaser pedal, really designed for guitar (mono) only works with one channel. So, the effect isn't so, well, effective. How have other keys players got around this. Do I go out with a phaser on each channel, or make do with the not-so-good mono from one speaker?
Comment: BTW you'll probably find the majority of live sound systems are either completely or effectively mono.
Comment: Maybe try purchasing a stereo-supportive phaser pedal?
Comment: @Qweevs - of course that's an option, and I have 3 or 4, but they don't, to me,  sound as good as the MXR Phase 90.
Comment: @ToddWilcox - I tend to go out self-contained working with live bands, but when having to use the house p.a.(sadly, sometimes) , will pan two channels l.& r. I appreciate most of an audience won't notice much difference, but I like it!
Answer: I wouldn't try anything like trying to synch two MXR Phase 90s. There are several phasers with stereo outputs, presumably with each output 180 degrees out of phase in their respective cycles?
One idea is to simply have the Phase 90 in one channel. From recording experience I've found that a phaser on one side of the stereo field can still sound like it is effecting the other side of the stereo field, because you are hearing the dry signal in reference with a signal with a constantly changing phase effect applied to it.
The stereo effect applied to a Rhodes quite commonly on records comes from the tremolo built into some Rhodes models, which basically pans between two channels. From memory this effect is utilised on some Pink Floyd and Jeff Beck records (there will be countless others).
Comment: Thanks. It's not merely a panning effect, but a change of sound, either like a leslie or a phasing. As heard on Billy Joel's Don't go Changing, and also some Paul Simon stuff. I tried it on only one channel, and don't like the effect it has on the sound.
Answer: Be careful over stereo on stage.  Even if the PA is stereo, few of the audience will receive the intended effect.  And be careful over stereo even when recording.  Are keyboards SO important to the song that they should take up the full soundstage?
If you're sub-mixing your keyboards on stage, and have your own stereo monitoring, you could put the phaser as a send effect and feed it back to both channels.  You can then get off on the sound!  But don't be surprised if a good sound guy narrows the stereo image you send him considerably, so as to give ALL the band members some space.
Comment: I've found that reasonably decorrelated stereo sounds that are panned wide take up *less* space, or at least leave a lot of room in the important center of the image for bass, vocals, and anything else more important. When I record mono guitar or keys, I usually double track it and pan the tracks in opposite directions or I pan guitars one way and keys the other or something like that. Layering stereo guitars and keys is much easier, IMHO, especially for pop or dance style sounds that focus on the vocals and/or drums and bass.
Comment: Panning hard left and right isn't going to 'take up the full soundstage'. It leaves plenty of room in between for all the other instruments, and doesn't get in the way of central vocals.
Comment: That could be because the "stereo" effects merely send the same information to each channel with reverse polarity.
Comment: @laurencepayne That's what I meant by "reasonably decorrelated" - not merely sending polarity reversed audio to one side. Doing that is not mono compatible either and doesn't sound wide, it sounds weird. Polarity reversed audio is actually highly correlated to the original.
Answer: I've been searching for the same thing for my Rhodes. I am very partial to putting a Phase 90 on just one channel as mentioned by ABragg. But for less subtle effect I sometimes put a mid-speed Phase 45 on one channel and a low-speed Phase 100 on the other. This interview with Don Fagen of Steely Dan fame describes using 2 Phase 90's in parallel.
For a 1-pedal solution, there's the MXR Phase 99 - two phase 90's with independent speed controls and outputs, built into one box. It's mono in, stereo out, so it'll need to be the first pedal in the stereo portion of your effects chain. I just bought one but haven't received it yet so can't comment on sound. The pedal has a "parallel/stereo" feature, which is cool but I'm only interested in the "parallel" mode. It was a limited release and most retailers only have a few left in stock, FYI.
Comment: I'm interested to find out what it's like in reality, SugarKeys. Please come back when you've played with it, so to speak.
Comment: Arrived in the mail today, just plugged it in and tried it. Sounds great! It does exactly what I says on the tin - two Phase 90's. There are a bunch of YouTube vids, take a look.
Comment: As I predicted, the setting I like is Parallel mode, the Vintage switch engaged, and Sync off, with the speeds at 9 and 10 o'clock, just slightly different so as to create stereo width. It is a more intense phasing than putting just one p90 on one stereo side, as you might expect.

Hope that helps!

Stereo or mono keyboard effect?


Is church attendance and/or participation in Communion a requirement for Roman Catholics?

Question: Is church attendance and/or participation in Communion (i.e., Lord's Supper, Eucharist, Mass) considered a requirement for Roman Catholics?
Answer: Attending church on the Lord's Day (Sunday) and other holy days of obligation is a requirement for Roman Catholic Christians.
According to the Code of Canon Law (CIC) 1247 (cp. Catechism of the Catholic Church (CCC), 2180),

On Sundays and other holy days of obligation, the faithful are obliged to participate in the Mass.

Frequent participation in the Communion (i.e., Eucharist, Lord's Supper) is encouraged, as long as the pre-requisites for participation are satisifed (CIC, 912-923).
According to the Code of Canon Law, 898,

The Christian faithful are to hold the Most Holy Eucharist in highest honor, taking an active part in the celebration of the most august sacrifice, receiving this sacrament most devoutly and frequently, and worshiping it with the highest adoration. In explaining the doctrine about this sacrament, pastors of souls are to teach the faithful diligently about this obligation.

In particular, Roman Catholic Christians are obliged to participate in Communion annually.
According to Code of Canon Law, 920 §1-2,

§1. After being initiated into the Most Holy Eucharist, each of the faithful is obliged to receive holy communion at least once a year.
§2. This precept must be fulfilled during the Easter season unless it is fulfilled for a just cause at another time during the year.
Comment: It's interesting that the Church of England also has this at-least-once-a-year-at-Easter precept.
Comment: @kutschkem The Mass always includes reception of communion by the priest, but it is possible to have a Mass in which the other people present do not have the opportunity to receive communion.  It is also possible for people to receive communion outside the Mass.
Comment: Does that mean that the Eucharist is not always part of the Mass?
Comment: @kutschkem: AFAIK it is, but you can't partake of the Eucharist unless you satisfy the prerequisites for participation.
Comment: @AndrewLeach The rules goes back to the [Fourth Council of the Lateran](https://en.wikipedia.org/wiki/Fourth_Council_of_the_Lateran), so the Anglicans just did not end this practice.


What does "push to close" mean?

Question: Can anyone who watched "Jurassic Park" explain me this moment?
Dr. Hammond tells Ellie to push a button which says "push to close" to turn on the power.
Answer: By pushing the "Push to Close" button, Ellie closed the breaker.
(When such a breaker is closed, it is in the "CLOSED" position1.)
By doing so, she closed the circuit, and they got the power back to the system.
(We need a closed circuit so that the current can flow in an electrical system.)
This "Push to Close" button was on the main circuit breaker. As it happened in the movie, when the main (circuit) breaker was closed (and they got the power back), she still had to close each individual breaker to close the circuit of (i.e., to power) each part of the park.
It's quite obvious that the main circuit breaker was a Westinghouse / Cutler-Hammer SPB breaker. It's unclear exactly which SPB model it was, though. Here is a photo of an SPB-65 breaker I found on National Switchgear's website:

According to basic operation instructions in an SPB Breaker manual I found on the web, here are the relevant parts that Ellie did to "close" the breaker.

4-1.1 HOW TO CHARGE MANUALLY
  To manually charge either a manual or electrically operated breaker, push or pull up on the charging handle. The handle is shaped to make manual charging easy when the breaker is located in either a low or high position with a switchboard enclosure. Four full strokes or several partial inching strokes can be used. When the spring is fully charged, the yellow "CHARGED" indicator will appear in the stored energy window on the breaker front cover. When the mechanism is fully charged the handle stops and will return to its normal position when released. Manually operated breakers have multiple charge-close provisions which allow the following possible operating sequence: Charge-Close-Rechage-Open-Close-Open.

(Before Hammond told Ellie to push the Push to Close button, he told her to pump up the primer handle. That action was to charge the breaker.)

4-1.3 HOW TO CLOSE
  All that is required to close the breaker locally is to push the mechanical "PUSH-TO-CLOSE" pushbutton. Precharged breakers may be closed remotely via a spring release solenoid which is standard for electrically operated breakers and optional for manually operated breakers (Section 5-3). For special applications, local manual closing may not be desired. Provisions are available in the form of a manual closing blocking adapter to prevent this action except by authorized personnel (Section 5-11).
Before attempting to close the breaker locally, the yellow stored energy window must read "CHARGED." Electrical interlocks are provided to prevent remote closing unless the closing energy is fully charged and the mechanism is ready to be closed.

(Ellie did this by pushing the mechanical "PUSH-TO-CLOSE" pushbutton.)

1The manual uses the term "position" to cover all kinds of positions of the breaker (OPEN, CLOSED, CHARGED, DISCHARGED, TEST, CONNECTED, DISCONNECT, WITHDRAWN, FULLY WITHDRAWN, and so on). A position of the breaker could refer to its Stored Energy Condition (CHARGED or DISCHARGED as indicated by the "Stored Energy" indicator), Contact Position (OPEN or CLOSED as indicated by the "Contact Position" indicator), Drawout Mechanism's position (TEST, CONNECTED, DISCONNECT, and WITHDRAWN, which is indicated by the "Position Indicator", but only when the breaker is "mounted", i.e., installed on self-contained extension rails; also note that it's DISCONNECT rather than DISCONNECTED in the manual), or other possible physical positions (such as FULLY WITHDRAWN and FRONT). In the photo, the breaker is in the "DISCHARGED" and "OPEN" position.
Comment: +1 for finding what looks like the exact same model of panel used in the movie :)
Comment: +1 but there is a typo which could lead to much confusion. Your second sentence should read: *(When such a breaker is closed, it is in the "**CLOSED**" position.)* "Closed" means "connected" in this case. "Close" as an adjective (which is how you used it in your second sentence) only ever means "nearby". The breaker is not in the "nearby" position, it is in the "connected" position. "PUSH-TO-CLOSE" uses "close" in the *verb* sense, meaning "connect" in this context.
Comment: @ToddWilcox Thanks for the catch! You're exactly right. It should read "CLOSED" position indeed. Fixed. (Note that "CONNECTED" could refer to the position of the drawout mechanism as well. I've added a footnote describing "positions" of the breaker to my answer.)
Answer: This clip from the movie showing the steps leading up to the moment in the question will help with context : https://youtu.be/PscRUlsvhtI
The system is a power plant and  you have to follow a sequence of steps to get it back on-line. First Ellie has to prime the circuit and then Dr. Hammond says "under the words contact position there is a green round button".
If she switches the "contact position" to closed, she will complete the circuit and power can be restored. If the contacts are in the "open" position, current won't flow, similar to a light switch. You turn the light switch "on" but you "close" the circuit so the power can flow to the light.
Not exactly relevant to your question, but there is a reference in a later Jurassic Park movie related to this moment:

Before embarking to Jurassic World, mom Karen (Judy Greer) tells her sons Gray (Ty Simpkins) and Zach (Nick Robinson) to be sure to answer the cellphone when she calls by "pushing the green button." That's an homage to the scene in Jurassic Park when John Hammond (Richard Attenborough) tells Dr. Ellie Sattler (Laura Dern) to restore power to the park by pushing the "round, green button." (Source)
Comment: Note that this technical use of "close" in "to close a circuit" is the exact opposite of the use of the word, common in Indian dialects, to mean "turn off". The expressions "open the light" and "close the light" are derived from analogy with a gas valve
Answer: The phrase

Push to Close

is only used as an instructional summary on the button, the fact that it is a green button would indicate something will start or proceed (red would indicate stop), that something needs to be closed in order for the process to proceed.
Comment: Each is a certain function: open, charge, close; and the user has to "push" the button (it's kind of redundant since there isn't much else one can do with that type of button)
Comment: Then what do other buttons means, like "push to open"? It's like "push to off"? I'm interested because the panel obliously has several buttons, to open, to charge. I thought each of them has certain function.
Answer: Push to close is a type of switch, you push it to close the contacts i.e. turn it on, a door bell button is a push to close switch.
My understanding of the terms open and closed when related to electronic switches derrives from an analogy to a gate, when the contacts are "open" the circuit is imcomplete, when the contacts are "closed" the circuit is complete, as electricity only flows in a closed loop, an open loop is the same as being off.
With electronic switchgear i.e. big circuit breakers such as the ones which control the electric fence, you would use a low voltage control circuit to operate the highvoltage breakers, so in this case push to close would mean you push to close the low voltage circuit which would energise the low voltage side of the the relay causing the high voltage circuit to be completed, thus restoring power just in time to zap tim...
Comment: The doorbell analogy will make a lot of sense among the non-engineers in the room, good description.
Comment: For the doorbell analogy, note that a doorbell is a **momentary** switch: it will remain the closed position *only* so long as you hold it down with your finger. Compare this to a lightswitch, which will remain in the closed position until you actively switch back to the open position. Here the "PUSH TO CLOSE" button is likely momentary as well; it energizes the low-voltage circuit which then acts to close the non-momentary high-voltage breaker.

What does "push to close" mean?


Why do two 'transverse waves' travelling in same medium have the same wave speed?

Question: Why is it that two transverse waves travelling in same medium have same wave speed? What does the medium has to do with it? I have searched through the web, but I couldn't understand. I have found that wave speed is a property of the medium $$\sqrt{\frac{\text{tension}}{\text{mass per unit length}}}$$
but also that the velocity of wave determined by $$\text{velocity}=\frac{\text{angular frequency}}{\text{wavenumber}}$$ Are both of these equations the same ? Or are they different?
Comment: Re, "What [the] medium has to do with it...?" A wave is not a physical thing. When you see a wave propagating through a medium, the only physical thing that is present is the medium itself. The wave is just the medium reacting to a disturbance in itself, and propagating that disturbance to other parts of itself.
Comment: Can you explain why you think they should be different?  I presume we are talking about an isotropic medium.  Both of your equations are true; are you saying that they appear to you to be inconsistent with each other?
Comment: Like wave velocity depends on tension and mass per unit length so by just seeing the formula how can we say that different transverse waves in same medium will have same ratio of tension and mass per unit length.ok I wanted to confirm both forms of velocity are correct or not
Comment: Waves don't have "mass per unit length." That's a property of the medium.
Comment: But the string has mass per unit length.
Answer: Your first equation determines the wave speed based on the properties of the medium the wave is propagating through. Your equation is specifically for a wave on a string. The equation makes sense qualitatively. If the string tension is greater, then the wave will propagate faster because there is a larger restoring force in the system. If the density of the medium is larger, then the wave will propagate slower because there is a larger inertia in the system that "resists" the restoring force. Any wave in this medium is subject to these same considerations, so any wave will have the same speed.
Your second equation is different. It is a true relationship between wave speed, angular frequency, and wave number.$^*$ This equation does not not say that frequency or wavelength determines the wave speed, for the wave speed is physically determined by your first equation. The intuition here is that since the wave covers a certain distance in some time as determined by its speed, then there has to be a set ratio between how long it takes in both space and time for the wave to "repeat itself". In other words, this equation is just a statement about what must be true for waves that propagate at a certain speed. It is not a statement of how the frequency or wavelength of a wave sets its speed.
An appropriate application of these two equations would be something like (I am not sure how physically realistic some of these numbers are, but that isn't the point here)

A string is kept at a tension of $10\,\mathrm N$, and the string has a linear mass density of $10\,\mathrm{kg/m}$. Therefore, a wave on the string will have a speed of $$v=\sqrt{\frac{10\,\mathrm N}{10\,\mathrm{kg/m}}}=1\,\mathrm{m/s}$$
If we then drive one end of the string with an angular frequency of $\omega=5\,\mathrm{rad/s}$, we know that the resulting wave will have a wave number of $k=5\,\mathrm{rad/m}$.

An incorrect application from the above example would then be

If we then drive one end of the string with double the angular frequency $\omega=10\,\mathrm{rad/s}$, then because $v=\omega/k$ we will then double the wave speed to $2\,\mathrm{m/s}$

The above is incorrect because our second equation does not determine the wave speed. Since we have not changed any property about the medium itself, the wave speed will remain constant. Correcting our mistake then:

If we then drive one end of the string with double the angular frequency $\omega=10\,\mathrm{rad/s}$, then because $v=\omega/k$ remains constant, we will then have a wave with double the wave number: $k=10\,\mathrm{rad/m}$. The wave speed is still $v=1\,\mathrm{m/s}$.

$^*$Or others might be more familiar with $v=f\lambda$ where $f$ is the frequency of the wave and $\lambda$ is the wavelength of the wave.
Comment: @JoeIddon Idealizing a situation isn't misleading. There are certainly situations where we can ignore dissipative effects. The question is obviously considering the idealized case, so I stuck with that. Would you say that people ignoring air resistance in projectile motion problems are being misleading? There are always caveats. You have to choose what to keep and what to ignore. You will never be able to take everything into account.
Comment: Great answer at explaining what the equations mean. I wonder if you also found this hard to approach due to the "why?". It's one thing to state an equation and say "yeah, that seems to agree with what I would expect", but to really *know* that the wave speed doesn't depend on something is quite difficult. For instance, this speed of a wave on a string wouldn't apply if the string were in treacle due to the different restoring force (frictional term in the DE), I would expect. Is the treacle part of the medium? What do you think?
Comment: @JoeIddon "*...but to really know that the wave speed doesn't depend on something is quite difficult*" Not really. All you have to do is change the property you are proposing. If the wave speed doesn't change, then you have shown that the wave speed does not depend on that thing. Of course this question an answer assumes an ideal case with no dissipation. If you have a question about how this analysis changes with dissipation, then I would recommend asking a new question. The comments of an answer is not the place to have such discussions.
Comment: Sure, feels slightly misleading to state definitively that this **is** the speed of a wave on a string, when there are caveats. I suppose this is the case with most equations.
Answer: I would question: what else would a transverse wave's speed depend on, apart from the properties of its medium?
Would you expect the wave to travel faster if it was night rather than day? Would you expect the wave to travel slower if it was a Tuesday rather than a Wednesday? Obviously not.
If you had any reasonable suspicion of some other condition that could be determining the waves speed, then either imagine or actually set up an experiment where that condition changes, and see if the wave speed would change.
So far as experiments have shown, for the simple case of, say, a ripple travelling along a rope, the only thing that determines the speed of the wave is - how thick and dense the rope is (mass per unit length), and how taught it is pulled (the tension). Nothing else changes the speed of the wave. (Obviously we are accepting a slight idealistic approach here where we don't consider factors like "hairiness of rope" which may play a tiny factor, but usually negligible).

Maybe you would be convinced reading this passage:

For example, there have been many experiments running rats through all kinds of mazes, and so on—with little clear result.  But in 1937 a man named Young did a very interesting one.  He had a long corridor with doors all along one side where the rats came in, and doors along the other side where the food was.  He wanted to see if he could train the rats to go in at the third door down from wherever he started them off.  No.  The rats went immediately to the door where the food had been the time before.
The question was, how did the rats know, because the corridor was so beautifully built and so uniform, that this was the same door as before?  Obviously there was something about the door that was different from the other doors.  So he painted the doors very carefully, arranging the textures on the faces of the doors exactly the same.  Still the rats could tell.  Then he thought maybe the rats were smelling the food, so he used chemicals to change the smell after each run.  Still the rats could tell.  Then he realized the rats might be able to tell by seeing the lights and the arrangement in the laboratory like any commonsense person.  So he covered the corridor, and, still the rats could tell.
He finally found that they could tell by the way the floor sounded when they ran over it.  And he could only fix that by putting his corridor in sand.  So he covered one after another of all possible clues and finally was able to fool the rats so that they had to learn to go in the third door.  If he relaxed any of his conditions, the rats could tell.
Now, from a scientific standpoint, that is an A‑Number‑l experiment. That is the experiment that makes rat‑running experiments sensible, because it uncovers the clues that the rat is really using—not what you think it's using.  And that is the experiment that tells exactly what conditions you have to use in order to be careful and control everything in an experiment with rat‑running.
Answer: The defintion of medium , or more precisely the true sense of the word Medium over here in physics is not what you encounter normally. In waves on String, medium means a string of same mass per unit length and of same average tension, in sound waves in a gas, medium means a gas with same adiabatic constant and temperature , you must take the feel of the statement rather than the literal meaning. So what you grasp from here is that what is medium in Physics is not precisely the same in language. But the converse is also true. Consider a steel wire and a jute wire with same tension and mass per unit length. If the definition of medium is taken in a literal sense then a wave should not have same speed in them since they are different material, but in reality they do. I hope you understand now. Critisisms welcomed


Would bio-kinetic metabolism allow the user to also absorb kinetic energy too?

Question: I am trying to base a superpower around bio-kinetic metabolism where the user can not only generate a massive amount of kinetic energy but can also absorb a massive amount of kinetic energy. Is there a way that the power bio-kinetic metabolism can do this. Here is a link to a site that explains bio-kinetic metabolism.
Comment: Your story, your universe, your rules
Comment: You've already answered your own question. "...but can also absorb a massive amount of kinetic energy".
Answer: Remember that "energy cannot be created nor destroyed, it can only be transformed".
To absorb kinectic energy, you need something to transfer that energy to you. In order to transform it into other forms, the collision must be inelastic. That is on you.
That energy will become heat/sound and deform the character. They will be able to spend that energy by reverting back to their original shape - just like a bow!
Answer: The boring answer is "no". Kinetic energy is just the energy of motion, so it can only be stored in a moving object such as a flywheel. Scale down the storage mechanism to cellular level and you're soon talking about molecular motion, which is just another word for heat. To turn heat back into macroscopic motion requires something like a steam engine. Unless you could get all your molecules to start moving in the same direction, but then you'd have to explain yourself to Boltzmann, and he was notoriously hard to reason with.
But then, who wants to be boring. Instead of storing energy as motion, store it as mechanical potential energy, i.e. tiny molecular springs. Then you can absorb external kinetic energy (a punch, a thrown ball, being hit by a bus...), store it in those springs and return is when needed in the form of muscle movement. This is essentially Renan's answer.
The fact is that inefficiencies on the molecular level would still produce a lot of waste heat and, in effect, cook your superhero. But, being a cool lady of a certain age, she will shrug that off as hot flashes and keep right on heroing.


Parish registers for Belper, Derbyshire, England

Question: Does anyone know of a good searchable (i.e. CD or Web site) source for parish registers for Belper in Derbyshire (UK)? I have tried to contact the Derbyshire family history society for information but haven't received any response at the time of writing. Their CDs-for-sale don't seem to cover Belper specifically. The Web site belper-research looked very useful but it relied heavily on LDS records, and they point out that the interface to FamilySearch has been broken by recent changes made there. The LDS records do contain some Belper data but it looks like they are not complete and does not include the names I'm looking for. I have subscribed to the RootsWeb mailing list for Derbyshire but I don't think I've seen a single message since then so I'm guessing that it doesn't really get much use. I recently joined eastmidlandsgenealogy but their Derbyshire coverage doesn't yet include Belper.
Answer: Derbyshire Record Office holds the original parish registers, some of which have been transferred to DVD and microfilm.  Their holdings for Belper are on page 23 of http://www.derbyshire.gov.uk/images/Parish%20Register%20Guide_tcm44-17013.pdf .  It appears only 20th cenutry records are on DVD, and I suspect the older records have not been digitised.  I suggest you contact Derbyshire RO for clarification and access.
Comment: Thanks Sue. I'm interested in 1830-1880 here in order to solve a riddle so I will check with the RO.
Answer: From your question it is not clear which "LDS" records you have seen.
This statement comes from https://www.familysearch.org/learn/wiki/en/Belper,_Derbyshire#Church_records

Belper St. Peter was created as a chapelry in Duffield parish in 1783, with St. John the Baptist chapel built in 1824, and made a civil parish in 1843. Parish registers for baptisms start in 1783 and burials in 1794, while marriages begin in 1847. The original registers are held at the Derbyshire Record Office (call no.: D2609A/PI/1/1-2, D2609A/PI/2/1-6, D2609A/PI/3/1-7, P1928/PI/4/1, D1928/PI/5/1-4, D2609A/6/1/1-3). They have been microfilmed and are available through the Family History Library [emphasis added]. The records include an index.
Comment: Thanks @Fortiter. I contacted the RO just yesterday by phone since my previous email had "fallen through the net". There are no digital versions of these records that they have available, leaving me with the only choice of a 400-mile journey. LDS does have some Belper transcriptions, but no images that I have found. Some of the specific events I wanted do not seem to be present either, and the RO confirmed that the LDS set was incomplete.


Compact gears and chains

Question: Wanting to know if you can use a compact crank and also use a compact cassette , I have placed both on my bike but the chain seems to be at the extreme when placing the chain in the smallest gear and then also the biggest gear.
Or is this normal?
Comment: when you say "I have placed both on my bike", do we take from this that you had a previous crankset/cassette, and you replaced them with a different crankset/cassette, but left the chain alone? Can you elaborate on what crankset/cassette you started with, and what you replaced it with? Talking about a compact crankset makes perfect sense, but there is no such thing as a compact cassette.
Comment: What is a compact cassette? My understanding of a compact crank is that it has a smaller BCD than traditional cranks and usually comes in a 50/34 flavor.
Answer: This is probably normal, but if the chain goes slack in small/small or completely taught in big/big, you may need to adjust the length of your chain accordingly. If it does both, you likely need a longer cage derailleur, but keep reading and you'll know how to check on that last case and know for certain.
Each cage length for a given derailleur is designed to take a minimum sprocket size, a maximum sprocket size, and a maximum number of teeth difference between running the bike in big chainring/big sprocket and small chainring/small sprocket known as "maximum capacity" or "total capacity". That final number basically defines how much extra chain the derailleur cage can take up and thus how wide of a gear range you can run. For example, a Shimano 105 RD-5700 rear derailleur has a minimum sprocket size of 11t, a maximum sprocket size of 28t, and a total capacity of 33t. To find out whether your drivetrain is within the total capacity range of the rear derailleur that you're running, use the following formula:
([teeth on largest chainring] + [teeth on largest cog of cassette]) - (teeth on smallest chainring] - [teeth on smallest cog of cassette])

for a 50/34 crankset in combination with an 11/23 cassette, you would have
( 50 + 23 ) - ( 34 + 11 ) which is equivalent to 50 + 23 - 34 - 11 = 28. You might see different orderings of this formula, but it's simple arithmetic so the number will come out the same.
If the number comes out to less than or equal to your derailleur's total capacity rating then you should be fine.
It's worth noting that you can push this if you feel comfortable doing so, but it's likely that the gears you're supposed to stay out of anyway (the aforementioned big/big, or small/small) will become totally unusable. For this reason it's probably best that you just adhere to the manufacturer's rating.
Answer: You need to adjust your chain length. If you just replaced your chain rings and sprockets with smaller ones, that is to be expected. Either visit your local bike shop or do it yourself. See Sheldon Brown's article on the subject of derailer adjustment that also covers chain length.
Comment: Not necessarily. This may be the case but you can't say for sure until you know op's before/after setup.
Comment: @PeteH: I suspected "I have placed both on my bike" means "I removed the original stuff [most likely "normal" components] and put on the small gears". If that's not the case, you're certainly right.
Comment: Yes, possibly, but when he says his chain is "at the extreme", that sounds like he means that its stretched to its limit. I wouldn't expect this if all he's done is gone from 53/39 to 50/34 (for example). If anything I'd expect the chain to be looser. Its a bit ambiguous, that's why I'm hesitant to offer an answer just yet.
Answer: I don't know what a compact cassette is either, but any derailleur will have an upper limit on the size of the biggest cog (shortest gear).  Maybe you need a long cage derailleur?

Compact gears and chains


What happens to ICO tokens released to a wallet that does not support ERC20 tokens

Question: If during a crowdsale you provide a wallet address that does not support ERC20 tokens will the Team send your tokens to a generated Ethereum address to be retrieved later with a private key and if so how?
Answer: No, most of the ICOs give you several warnings before sending the money about using an address whose private key you do own.
If for some reason you still used an incorrect address, many ICO devs will allow you to contact them to let them know and find a solution BEFORE they distribute the tokens.
If they already assigned/distributed the tokens your money and tokens are probably lost.
Comment: Thanks for the response, This is for a friend and I'm sick about it because he invested in Power Ledger on my advise but he used a Bitcoin address from Blockchain.info wallet and Power Ledger sent him an email saying it was sent to an ethereum address that he doesn't control, how can he get the key to that address? How did they decide where to send it because that is not the address that he gave them?


What kind of seeds/pods are these?

Question: I purchased these on the WISH app. They were under $1 and advertised as Monstera Seeds. I knew 100% that these were NOT monstera seeds, but had to snag them to try to figure out what they are. At first glance, they look to be bamboo - but I'm still not solid with that. Any guesses on what these could be?
Comment: Need more detailed info. Is this a samara type seed (like ash/maple tree for example) where the seed is integrated into the tip of a wing designed to let the seed flutter in the wind as it falls? If it is a pod, crack one open and what do you see?
Answer: Those seeds really look like American Tuliptree (Liriodendron tulipera) seeds. It's very strange that someone would mistake them for monstera.

What kind of seeds/pods are these?


Schengen Visa and International Students

Question: I am planning on taking a trip to Europe and require a schengen visa. As an international students, I keep substantial amount of my savings outside of the country, but also have UK bank account. For the Schengen Visa application in London, can I use my non-UK bank account, which is denominated not in Euros,Dollar or Pounds? I believe my UK bank account may not satisfy the visa officer because I deposit money in the account non-constantly and balance is not constant as well.
Thanks
Comment: Why would you not use both? You do want to get the visa, right?
Comment: Assuming the non-UK account is in your name, you can access the funds readily (eg it's not a fixed deposit) and provide recent statements, why would you not be able to use it as proof of financial means?
Comment: @MichaelHampton that sounds like an answer.
Answer: The purpose of submitting bank statements with your visa application is threefold:

Demonstrate that you can support yourself
Demonstrate that you have strong ties to your home country - a fixed constant income every months shows you receive a salary of some sort, hence you have a job
Demonstrate that you lead a financially healthy lifestyle

With this in mind, you should provide the statements of the accounts which best help you represent your case. Keep in mind that you must be able to explain the provenance of the funds, and the reason behind the transactions.

can I use my non-UK bank account, which is denominated not in Euros,Dollar or Pounds?

Yes you can. The bank account does not have to be in the currency of the destination country. The important thing is to keep in mind exchange rates and cost of living. There are plenty of examples questions on this site in which applicants get rejected because they do not meet criterion 1: supporting oneself. If the bank account statement shows a monthly income which is too low compared to the average monthly cost of living in the destination country, then it is likely that the application will be rejected.


Star wars chronology

Question: I have not seen any Star Wars movies till date. I don't have any idea about the timeline of Star Wars but recently after the release of Solo: A Star Wars Story, a curiosity has been awakened in me. So I would highly appreciate if anybody can tell me the order in which I should watch these movies to get a better understanding of the Star Wars universe.
Comment: Possible duplicate of [In what order should a newcomer watch Star Wars episodes?](https://movies.stackexchange.com/questions/2063/in-what-order-should-a-newcomer-watch-star-wars-episodes) & also https://movies.stackexchange.com/questions/65237/in-what-spot-would-the-new-star-wars-movie-rogue-one-go-in-the-machete-order
Comment: https://scifi.stackexchange.com/questions/1520/in-what-order-should-the-star-wars-movies-be-watched
Answer: Film & TV Series Cannon Chronology Event Order

Episode I: The Phantom Menace
Episode II: Attack of the Clones
Star Wars: The Clone Wars (Animated TV Series. New Season is coming!)
Episode III: Revenge of the Sith
Solo: A Star Wars Story
Star Wars: Rebels (Animated TV Series)
Untitled Andor Cassian Rogue One Prequel (Live Action TV Series Comming 2020 Disney +)
Obi-Wan Mini-Series (Live Action TV Series Coming 2020 Disney+)
Rogue One: A Star Wars Story
Episode IV: A New Hope
Episode V: The Empire Strikes Back
Episode VI: Return of the Jedi
Star Wars: Resistance (Animated TV Series. Premiers October 2018)
Star Wars: The Mandalorian (Live Action TV Series. Premiere's November 12th 2019)
Episode VII: The Force Awakens
Episode VIII: The Last Jedi
Episode IX: The Rise of Skywalker (Released December 20th 2019)

Note that the "Episode" films are the Skywalker [family] Saga Films. "A Star Wars Story" are anthology films, but Solo might have been a trilogy. There is talk of a TV series, but nothing confirmed. There are also 2 other potential trilogies: one from The Last Jedi Director Rian Johnson and one from Game of Thrones EPs, David Benioff and D. B. Weiss. And there may be film coming from Kevin Feige of Marvel MCU fame.
I have given the chronological event order of the films, but there are several theories and/or preferences for "best viewing", as some feel that watching them in different/non event order (such as by release date), is better than watching them in event order. But since that is opinion based, I did not specify any preference, only giving you a layout to where everything is "suppose" to go in terms of the event history. You can look for opinion-based preferences by doing a Google search.
In addition there are several comic and book series. Some are tie-in material that expand on the films/TV shows.
Comment: I disagree.  Watching them in the order of release introduces the basic concepts and central characters.  The prequels are intended to provide origin story.  Seeing them first would only serve to disappoint.
Comment: Everyone has their viewing preference, but I didn't take the Q as opinion based. I just listed them chronologically in terms of the actual event history order so they could see where everything is suppose to be. There are plenty of arguments and points to be made watching them in non event order, but I am not sure if that is what the Q was asking and/or still feel they should be able to see the event order and then decide on other people's preferences, including release dates.
Comment: Choosing chronology over production order is an opinion, though.
Comment: If one was writing a story they still need drafts/outlines of events before they may decide later to change the order of things they wrote. IMO this is no different. I even stated that I made a layout and pointed out that there are several ways people believe they should view the films. If someone wants to provide another answer, they can. Q specified they didn't know the timeline.
Comment: Also it doesn't matter now that this is considered a duplicate Q.
Comment: How can it be a duplicate when the other only covers they 2012?
Comment: @CrossRoads While I would agree that the answers are out of date, because most of them don't include new films made this past decade, it is same @ and this thread can still be found and is linked with that Q now.

Star wars chronology


INUS conditions for invalid arguments

Question: Is it a necessary and sufficient condition that invalid arguments have a false conclusion?
Comment: The only thing ruled out by an argument being valid is that its premises are true and its conclusion false. Also, this is nothing to do with INUS, which refers to an analysis of causal relations.
Answer: 1) An invalid argument may have a true conclusion:
Consider the invalid argument: "Because Socrates is mortal, all humans are mortal." Nevertheless the conclusion is true: "All humans are mortal."
2) An invalid argument may have a false conclusion:
Because Socrates is Greek, all humans are Greek.
3) A valid argument may have a false conclusion:
Because all humans live in Africa, also Socrates lives in Africa. (this kind of valid argument is named "ex falso quodlibet")
4) A valid argument may have a true conclusion:
Because all humans are mortal, also Socrates is mortal.
Answer: You may want to look at the answer to The validity of the definition of a valid argument
but having a false conclusion is neither a necessary nor sufficient condition for an invalid argument.
The definition of validity (assuming we're not working with Tarski's model theory) is that

an argument is valid if it is the case that it cannot have all true premises and a false conclusion.

Thus, a valid argument can have a false conclusion if it is not the case all of the premises are true.
Conversely, an invalid argument can have a true conclusion and/or all true premises.
For instance,

Pigs can fly. Therefore, apples are a fruit.

false premise. True conclusion. Invalid argument. (Because it would be possible for the premises to all be true and the conclusion false).

If pigs can fly, then Obama is president. Therefore, Japan is a country.

True premise. true conclusion. Invalid argument. (Because it would be possible for the premises to all be true and the conclusion false).

INUS conditions for invalid arguments


clarity in understanding the moment of inertia matrix D and Coriolisis and centripetal matrix C as per attached equations

Question: Would appreciate if anyone could help me understand the how if equation 6 and 7 are derived. Helping with any one D22 and C32 would suffice.
Comment: The definitions of D and C are given in equation 4 of that text.   Are you having trouble computing them, or do you want more information about what they represent?
Comment: I have issue in understanding how those equations are arrived at. I seek clarity in understanding how the Ixx, Iyy, Izz elements of the inertia tensor matrix are derived.
Answer: Where did this example come from? It looks like maybe a class handout or similar. I don't agree with all of the formulas given, but I'll try to explain where I think they should be coming from.
The $\bf{D}$ matrix is pretty straightforward - the key here is to understand the parallel axis theorem, which is a formula for finding the moment of inertia at one point given the moment of inertia at the center of mass and the mass:
$$
I_{\mbox{new}} = I_{\mbox{center of mass}} + mr^2 \\
$$
The linkages form a kinematic tree, where each joint "feels" the mass of its "downstream" link and the effective masses of all links attached after it as well.
So, start with the last term in the matrix - $\bf{D}_{44}$:
$$
D_{44} = I_{bu} + M_{bu}r_4^2 \\
$$
This is exactly the parallel axis theorem. You transfer the moment of inertia from the center of mass of the bucket to the stick-bucket joint, because that's where you're rotating. The next step is a little tricky because everything has already been reduced. I'll walk through the derivation of $\bf{D}_{33}$ and then hand-wave the rest saying the method is similar.
The distance from $O_2$ to $O_3$ is $a_3$. The distance from $O_3$ to $G_4$ is $r_4$.
If you wanted to get the distance from $O_2$ to $G_4$, then you could use the Pythagorean theorem, but that's only applicable for right triangles, so what you have to use instead is the law of cosines, which is a generalization of the Pythagorean theorem that applies to all triangles:
$$
c^2 = a^2 + b^2 - 2ab\cos{\gamma} \\
$$
Where $\gamma$ is the angle between $a$ and $b$. Side note: for right triangles, they're "right" because the angle between $a$ and $b$ is a right angle (90 degrees), so the cosine of 90 is zero, so that term drops off and you're left with the Pythagorean theorem.
So, for your example, you need not just the angle of the stick-bucket joint, but also the angle from that joint to the center of mass.
The angle of the stick-bucket joint is $\pi + \theta_4$, per the drawing, and now you need the angle from the $O_3 - O_4$ joint to the center of mass of the bucket; this is given as $\alpha_4$.
Now, going back to the parallel axis theorem, if you wanted the moment of inertia for the bucket about the stick-boom joint, you need the moment of inertia for the bucket at the bucket's center of mass, and then you need the straight-line distance from the bucket-stick joint out to the center of mass of the boom.
Call that distance $c$, call the distance from the boom-stick (joke) joint to the stick-bucket joint $a$, and the distance from the stick-bucket joint to the bucket center of mass $b$, then what you get is:
$$
I_{\mbox{bucket about boom-stick joint}} = I_bu + M_{bu}c^2 \\
$$
$$
c^2 = a^2 + b^2 - 2ab\cos{\left(\mbox{joint angle} + \mbox{center of mass angle}\right)} \\
$$
$$
c^2 = a_3^2 + r_4^2 - 2a_3r_4\cos{\left(\left(\pi + \theta_4\right) + \left(\alpha_4\right)\right)} \\
$$
Now a little regrouping in the cosine term:
$$
c^2 = a_3^2 + r_4^2 - 2a_3r_4\cos{\left(\pi +\left(\theta_4 + \alpha_4\right)\right)} \\
$$
And finally a period shift identity:
$$
\cos(\pi + \theta) = -\cos{\theta} \\
$$
And you get:
$$
c^2 = a_3^2 + r_4^2 - 2a_3r_4\left(-\cos{\left(\theta_4 + \alpha_4\right)}\right) \\
$$
Distribute the negative:
$$
c^2 = a_3^2 + r_4^2 + 2a_3r_4\cos{\left(\theta_4 + \alpha_4\right)} \\
$$
NOW FINALLY plug this $c^2$ back into the shifted moment of inertia equation:
$$
\begin{array}{ccl}
I_{\mbox{bucket about boom-stick joint}} & = & I_{bu} + M_{bu}c^2 \\
& = & I_{bu} + M_{bu}(a_3^2 + r_4^2 + 2a_3r_4\cos{\left(\theta_4 + \alpha_4\right)}) \\
& = & I_{bu} + M_{bu}r_4^2 + M_{bu}(a_3^2 + 2a_3r_4\cos{\left(\theta_4 + \alpha_4\right)}) \\
\end{array}
$$
Now recognize that $D_{44} = I_{bu} + M_{bu}r_4^2$, meaning that:
$$
I_{\mbox{bucket about boom-stick joint}} = D_{44} + M_{bu}(a_3^2 + 2a_3r_4\cos{\left(\theta_4 + \alpha_4\right)}) \\
$$
So that's the moment of inertia of the bucket about the boom-stick joint, now you also need to add the moment of inertia of the stick about the boom-stick joint,
$$
I_{\mbox{stick about boom-stick joint}} = I_{st} + M_{st}r_3^2 \\
$$
Put it all together and get:
$$
\begin{array}{ccl}
I_{33} = D_{33}& = & I_{\mbox{stick about boom-stick joint}} + I_{\mbox{bucket about boom-stick joint}} \\
& = & I_{st} + M_{st}r_3^2 + D_{44} + M_{bu}(a_3^2 + 2a_3r_4\cos{\left(\theta_4 + \alpha_4\right)}) \\
& = & \boxed{D_{44} + I_{st} + M_{st}r_3^2 + M_{bu}(a_3^2 + 2a_3r_4\cos{\left(\theta_4 + \alpha_4\right)})} \\
\end{array}
$$

Short P.S. -
The trouble with calculating the Coriolis force (why I'm not willing to do it at the moment) is that it's a cross-product. You're looking at a singular plane, but it looks like the axes are flipping for some reason; $O_3$ and $O_4$ seem to be rotated about the y-axis? Or maybe the y- and x-axes? I can't tell if that's a typo or not.
Anyways, you should take the cross-product and then keep the terms about the axes you care about; the forces about the axes in the plane don't affect the solution.
But, there are a lot of typos in the document;

$D_{44} = I_{bu} + M_{bu}R_4^2$ should be $D_{44} = I_{bu} + M_{bu}r_4^2$,
$D_{24} = D_{42} + D_{34} + (...)$ should probably be $D_{24} = D_{42} = D_{34} + (...)$,
I think that the signs are wrong on the off-diagonal $D$ terms, but I'm not willing to study the problem hard enough to verify,
there are $\dot{\theta}_{234}$ terms that aren't defined, etc.

I would definitely question the source/author of the paper you've acquired. Generally speaking, the method is as I've described above. Start where the only force is the local one, then work your way up (or down) the kinematic chain. Subsequent forces are the new local forces plus all of the previous forces expressed relative to the local frame.
Comment: I've got to run at the moment, but this should be enough to get you started. The Coriolis forces should work the same, but I'm a little confused in that I would have expected them to go the "other direction" down the kinematic chain. The Coriolis "force" is a fictitious force that exists to "explain" how an object moves because of rotations elsewhere, like how a bullet "curves" because the Earth is rotating. I'm not sure then how $C_{44} = 0$; I would have expected $C_{22} = 0$.
Comment: Hi, Thanks a ton for enlightening me. I owe my respect and gratitude to this community and contributors for being instantaneous and courteous to help. Honestly, I have been battling with this for about 3 weeks. I would go through the discussions and revert on questions if any. The paper reference is  https://www.researchgate.net/publication/225972318_Modelling_and_Remote_Control_of_an_Excavator


How can I soft-wrap a word to a new line?

Question: Using textwidth (tw=74) a word will be moved to the next line (with an indent usually) with a newline character at the end of the line avoiding over-length. This is a hard wrap, and resizing the window will not change the location of the wrap. Using :set wrap, soft wrapping sends the text that would fall off the right side of the window to the next line instead, keeping all of a line's text visible. I'd like to combine some of each function, such that a word moves entirely to the next line after a certain point, but does not get permanently sent there in the file with a newline character.
It doesn't matter if this sending to the next line occurs only immediately after a string broaching the set number of columns.
Answer: I think you're looking for the 'linebreak' option:
:set linebreak

See :help 'linebreak' for details, including the use of 'breakat', 'breakindent', and 'showbreak'.


Is this truly a story-id question?

Question: There's this question which is definitely a valid question. However, it's tagged with story-identification. Is this a valid tag and why? I honestly don't think it matches, but there doesn't seem to be another matching tag (e.g. scene-identification).
Answer: The story-id tag is for the generic identification of any science fiction or fantasy property. It doesn't strictly have to be a (written) story. It could also be a game, song, film, book, movie or whatever as long as it fits within the site's scope.

Use for identifying a work of SF or Fantasy, including novels, movies, comic books, fanfic, TV series, video games, etc. Use with other tags to specify the type of media, eg. [short-stories]. Use [episode-identification] for identifying a single episode of a known series, whether TV, book, or comic. Use [actor-identification], [character-identification], [music-identification], or [object-identification] for those specific ID requests.

It would help if OP qualified it with one of the media tags, but in this case, they don't actually know whether it's a TV show or a film so any attempt to additionally qualify it would be pointless.
Comment: Couldn't it be [tag:episode-identification] because it's part of the greater Marvel thing?
Comment: @Stormblessed - Theoretically. Except that OP has no idea whether it's from a TV series, a film, a comedy skit or anything else.

Is this truly a story-id question?


How can I automatically connect my phone to the stronger Wifi signal around it?

Question: I have a Google Nexus 4 and have two wi-fi networks that I use in my home. Since they are in some range of one another my phone stays connected to the router that's farther away from the one I'm closer to. Is there a way or app that can connect me to the stronger wifi signal around me when I move around my house?
Comment: Are those wifi networks sharing the same channel?
Answer: Unfortunately, there's no native method for this (at least to my knowledge). But WiFi Switcher does exactly that. According to its description:

The tool checks the registered WIFI networks every 20 seconds. If one of these networks has better signal strength than the currently one, the tool changes the WIFI network to this better one.

But it's not that well rated (3.2 with 75 ratings). The alternative WiFi Jumper has a better rating (4.1@194), but is not free:

Automatically connect to the strongest available WIFI (scaninterval configurable)
Even unknown, but unsecured networks can be used automatically (configurable)
Optional: create Wifi Zones based on one or more Radio Cells to automatically start and stop Wifi Hardware.
Comment: This also might be a battery drain due to the inherent inreliability/fluctuations of/in Wi-Fi strength measurements. It can differ based on a lot of factors, so doing this at all might be a bad idea to begin with, but I'm not sure.
Comment: @bigbadonk420 +1 yes, continual scanning can suck the battery juice, wait and see if Android 4.3 resolves this, as apparently it's supposed to be able to scan without activating wifi...
Answer: You can do it manualy by using Wifi Analyzer and then connecting to the strongest wifi around you. I don't know an app that could automate this for you.
Link to app
Comment: You might want to correct the first sentence of your answer -- see mine :)
Answer: There is another third-party method using "WiFi Connect" as a plugin for Tasker. There is a tutorial on YouTube, described as follows:
Switch to Strongest WiFi Signal on Android

Based on a request from a viewer, in this lesson we create a profile
  and task to test the strength of the current WiFi signal and switch to
  another one if it's weak.  Best utilized in a house or business where
  there are multiple hotspots/connections, we cover several new topics
  including Splitting Variables, Testing Text to see if it contains a
  word or character string, Flashing variable info, and Reading/Writing
  files.  (This lesson also makes use of a Tasker plug-in called WiFi
  Connect.)


Has an idol been clearly defined as to what is an Idol that makes it Avodah Zarah?

Question: Has the Hebrew word for an "idol" been clearly defined as to what is an Idol and what is not?
Comment: @DoubleAA, Ali, re the requirement to destroy it? re the ban on worshiping it? re the ban on owning it? re the ban on deriving benefit from it? re the process of 'nullifying' it? For what purposes are you asking? There may be different answers depending.
Comment: For what purposes? I imagine there may be multiple definitions in differing contexts (though maybe not).
Comment: For judging an object to be an Idol .
Comment: @msh210 Perhaps for purposes relating to [tag:avodah-zarah]?
Comment: Your title doesn't match the body.
Comment: @DoubleAA does it now?
Comment: @msh210 all of them , how can a definition of idol changed based on how it is used , doesnt idols have intrinsic qualities that make them soo?
Comment: Ali, I'll venture a guess that _idol_ is not a word that appears in any classic Jewish sources: they're mostly in Hebrew (though in some other languages too). So you're really looking not for a definition of _idol_ at all but for a definition of a Hebrew word corresponding to _idol_. And it's certainly possible (though I don't know) that there's more than one such word depending on context, or that such a word has more than one meaning depending on context (much as _r'shus harabim_ has very different meanings for _nezek bor_ and for _haavara arba amos_).
Comment: @msh210 and for _safek tuma_... As for Hebrew words consider צלם פסל מסכה or צורה
Answer: Yes it is defined but as often occurs in Jewish law, there's a tremendous amount of nuance from case-to-case. But I will simply point out that one can theologically violate "worshipping something other than God" without necessary rendering a specific object an "idol." (E.g. if someone walks onto my yard and bows down to my apple tree and tries to worship it, he is committing idolatry, but he had no ownership of my tree and therefore didn't render it an "idol." I can still use that tree. Versus a tree that was planted for the purposes of worship is prohibited from use.)
The Talmud's tractate of "Avoda Zarah" (foreign worship) devotes its third chapter to this, what's called an idol and what's more likely a decoration. E.g. a rule of thumb had been that a Greek/Roman statue of a person holding a globe, staff, or bird was likely actually idolized, whereas a statue of a person holding something else (e.g. a torch?) was probably just symbolic. Similarly there's the story of a Greek bathhouse with an image of Aphrodite on it; a rabbi still used the bathhouse. Asked how he could do so,
he explained (after exiting the bathhouse, as we don't discuss Torah in a bathhouse): "you Greeks didn't say, let's build a bathhouse to glorify Aphrodite. You said, let's build a bathhouse because we want one, and we'll put an Aphrodite on it to glorify the bathhouse!"
Later works such as Shulchan Aruch discuss many more cases (e.g. the Hispanic-products aisle in many supermarkets contains candles with pictures of saints on the glass jar -- while I strongly recommend buying regular candles instead, if this was the only candle available, a rabbi should ask -- was that truly made for the purpose of worship, or was that made by Acme Candle Co. who would just as happily put SpongeBob Squarepants on the jar if it sells better?)
Comment: Good andwer You have not addressed the issue of people making the Idol as a medium of worship to one God.
Comment: @shalom it wasn't a picture if Aphrodite it was an actual statue if I remember correctly
Comment: @knowit Not sure how that's necessary for this question.


Can we assign same fields to different page layouts. How can we achieve this requirement

Question: Can we assign same fields to different page layouts. How can we achieve this requirement. I have created few fields and assigned one page layout ( Account Lead), Now i want to assign the same fields to a different page layout ( Supply account). Please help me with this requirement.
Answer: In general, an option one always has is to "clone" an existing page layout and save it with a new name. You can then edit it to remove or add any fields you wish.
In the particular situation that you're describing, Supply Accounts would seem to have a different Record Type. You can create a unique Page Layout for displaying objects with that Record Type. That would easily be done when you specify a unique Record Type. You may want to look at creating Object Specific Actions which would help facilitate that. They're well covered in the Force.com Fundamentals as well as in the Salesforce Help. Other references that may be useful to you would be the Force.com Workbook, Tips and Hints for Record Types and the VisualForce Workbook.


How to get past stalled initial station search in NextRadio?

Question: I have a phone with an FM chip. To make use of it, I installed NextRadio. During onboarding, NextRadio is supposed to look up local radio stations. However, it hangs on this step, displaying a throbber but going no further and not responding to any input. How can I get past this step so I can use the app?
Answer: With data networks (cellular data, Wi-Fi) disabled, NextRadio's station search will fail immediately instead of hanging.
Try enabling airplane mode, then re-opening NextRadio. Instead of stalling and showing the activity indicator, it should give you a message that it couldn't find a station listing. Tap "OK" to proceed.
Now disable airplane mode, as it also disables the radio. Using the basic tuner, you can add stations as favorites to assign a name to them.


If all I have are US dollars when I first arrive in the Philippines, is it okay to tip with that?

Question: I assume that people would prefer to have foreign currency to no tip.  But should I absolutely make it a point to covert some currency first thing so that I can tip in Pesos?
Answer: In general I would always arrive in a country with a least a little local currency (if it's legal to do so, which it isn't always but is in the Philippines). There's been a couple of times I've been close to stranded on arrival because I didn't. You probably need money to get from the airport (unless you've pre-arranged transport), and exchanging money in the airport isn't the best deal (plus the counters aren't always manned).
In Manila airport there are ATMs just outside customs that will take international cards.
You can certainly tip dollars, be aware that people will probably getting a very poor exchange rate for them. You'll need to pay transport in pesos. Try and have some smaller bills if at all possible, taxis (airport taxis in particular) will often claim to have no change to force you to pay them 1000 pesos for the trip. ATMs will dispense down to 100 peso notes if you request an amount they can't make in larger notes.
Answer: You can, but I would strongly advise to you get some PESOS at the airport. Paying or tipping in USD will attract unneeded attention and you will be assumed to be carrying a lot of USD. Not good. It attracts greedy people! Remember 5% tipping is all you need to give since tipping is not a custom in the Philippines, and giving USD will be leaving a very large tip! It promotes greed in future dealings with foreigners!
Comment: My observation (in Cebu, at least) was that simply _having white skin_ was sufficient to attract such attention, regardless of what currency you used for tips. As a side note, some places (like the airport's immigration fee collection desk) would accept USD but _would not provide change_ if you paid in USD, so you could end up way overpaying.


EE3 best option for multilangual site

Question: Which one is best for multilangial site? Using expressionengine 3 multi site manager or transcribe?
Answer: Although it is (apparently) a few weeks away from being released for EE3, Publisher is an awesome multi-language plus workflow system.  So unless you are in a rush, it might be worth waiting...   More at Boldminded website.
Answer: I have been using Transcribe for a while and it is simple and elegant. The support is a bit slow but most of it is self-explanatory. LTR and RTL languages play well with Transcribe.
NavEE goes hand-in with Transcribe, to solve the menus related obstacles.
Answer: I have used Transcribe a lot, and i really like it. Publisher is ok too, but if you don't need the workflow features i'd choose Transcribe.
Answer: I'm using Republic Variables or Low Variables.. if your site is simple.. i should be enough.. I'm out of the office but if you need more infos i can explain more..
Comment: Please expand on this answer; it isn't clear how it resolves the question.

EE3 best option for multilangual site


How do I mention a video game in a formal piece of writing?

Question: What is the proper convention for mentioning the title of a video game in a formal research paper? Would I place the title in quotations, like the name of a short story ("Myst"), underline it, like the title of a book, or italicize it (Myst)? I would prefer an answer backed up by a formal standard such as MLA, APA, Chicago, or AP, if they cover this.
Answer: According to Diana Hacker's Research and Documentation (Bedford-St. Martin's), the MLA citation for a video game should follow this format:

From the same source, the APA citation for a video game should follow this format:

(You can't tell from the example of Sims 2, but in an APA citation, only the first word of a title is capitalized. Therefore, Call of Duty would be listed as Call of duty.
These are the formats for a Works Cited/References entry. In the text itself, the title of the video game should be capitalized and italicized, just as the title of a book would be.
Answer: The APA does in fact cover this, though under the broader category of "software."
In text, the title of the video game should NOT be italicized (p. 210). When citing the video game, you'd use the following convention:

Copyright Holder (Year of Publication). Game Title [Software]. Location of Producer: Producer.

Note that Copyright Holder and Producer may be the same.
Source: APA manual, 6th edition. I'll confirm with MLA and Chicago when I get home.
Comment: OP, thanks for accepting my answer, but please see the revised answer! I left out the most important word, "not." The titles should not be capitalized. For added reference, I included the page number.
Answer: Chicago Manual of Style 8.190. In running text video game titles are italicized.
Answer: According to this blog post, you simply capitalize the title when writing it in-text. The citation style in the previous two answers appears correct.


Is it bad if Guided Access is always running?

Question: Since Guided Access restricts only one app to be opened, would it prevent other background processes like app updating, memory cleaning, data fetching and cause apps freezing? My old iPad 2 sometimes lags, and I'm not sure it's because it's designed as is, or because Guided Access is not exited regularly. It's also rarely restarted.
Answer: I have guided access running all the time, however i am not experiencing any slow-downs (using an iPad Pro).
I doubt guided access is different than any other app, so the background tasks should execute.


Estimating piston-engine thrust on take-off

Question: In my Uni course I've learnt how a piston-engine produces a constant power, as opposed to a constant thrust like in a jet engine, which can be estimated as Thrust = Power / Velocity. However, using this formula I calculated that a Spitfire should be able to go from idle to take-off in under 1.5s (as opposed to 9.5s irl). So my question is this: what else is going on that makes the true take-off time so much longer than my calculated take-off time?
Comment: What does your formula give as thrust a 0 velocity? Or near zero... is that a realistic value?
Answer:
Thrust = Power/Velocity

Refers to the energy state of the aircraft.  Units are mv$^2$/s for Power.
People often confuse this "power" with the power output of the engine, which in its most basic form is fuel burned/second multiplied by efficiency factors giving horsepower output,  described as torque at a given RPM.
It doesn't end there.  Now we have to further consider the efficiency of the prop at a given airspeed.  This is why it is very rare to see prop driven aircraft listed as having a given "thrust".
In reality, the horsepower is consumed by the drag of the propeller, or more properly, the drag torque of the propeller, which is drag force summed from a center of resistance not unlike the "sweet spot" of a baseball bat.  Props can also be geared so engine rpm and prop rpm are better matched.

The thrust output is the "lift" the prop airfoil creates.

That is the Force pushing against the inertia, tire friction, and aerodynamic drag of your Spitfire as it accelerates down the runway.
As with the other airfoils on your plane, the wings, quantifying prop "lift" in units of force can be approximated by determining mass flow of air created by the spinning prop as action/reaction forces.  Also, thrust at V 0 can be measured (as with model aircraft) "on the bench" by attaching a scale to the back of the engine/prop mount and applying full throttle.
Answer: I propose the following method: the rate of change of momentum has the units of force. When you are standing still on the brakes with full power applied, the prop is taking air which is essentially standing still (zero velocity) and applying a force to its mass which accelerates it to some exit velocity. That force is opposed by the brakes and is equal to the thrust being applied to the airframe by the bearings in the engine case as the prop tries to pull the engine forward.
This means if you know the air mass flow rate through the propeller disc, you should be able to solve for the momentum change and get the thrust that way.
We eagerly await Peter Kaempf's (yes I know it's spelled wrong) opinion on this method!
Comment: The spelling is fine for someone on a US keyboard.
Answer:
So my question is this: what else is going on that makes the true take-off time so much longer than my calculated take-off time?

Findings: If evaluated considering propeller thrust, resisting drag, and weight of the aircraft, an accurate and realistic time and distance for reaching take-off velocity can be determined.  An adequately developed computational procedure must be used, however.  Aspects considered include propeller diameter and blade dimensions for the estimation of thrust, and influence of the propeller slip-stream on lift.  Results for two Spitfire aircraft, for which adequate factual information was available, show computed times and distances to takeoff that are comparable, with little difference, to reported field measurements. For aircraft K.9793, a well documented Mark 1 machine, the computed take-off-run time and distance was about 12.39s at 321 yds, while the field reported time and distance estimate was 12.5s at 320 yds, given no wind and standard atmosphere conditions.  An incidental investigation regarding computational adjustments to determine take-off time and distance in wind provided similarly comparable results.  A brief overview of the basic computational process for take-off time and distance without wind is provided. $^*$A short end-note gives a perspective of the time required to answer this question.

Your very interesting question involves somewhat more than meets the eye, particularly when trying to make an assessment of a plane of this type.  A direct solution can be determined only if a number of variously different factors are considered.  You see, in order to obtain realistic results to determine the take-off time and distance for the Spitfire, one must, in a literal sense, fly the airplane on paper.  This means accounting for various factors of significance that affect the outcome of the determined result.
Three basic factors are at play, namely, thrust, drag, and weight.  From the outset, we would have to consider these three factors to determine the required take-off time and distance of a Spitfire.   Specific issues in accelerating an aircraft to take-off velocity primarily regard propeller thrust, drag due to rolling resistance during the take-off run, aerodynamic drag of the fuselage and lift-induced drag of the wing, and ultimately, weight of the aircraft and consequent lift produced by the wing during the take-off run.  In determining our answer, by assuming the process-forces are linear with respect to the square of the velocity of the aircraft, we only need to consider the mass of the plane, velocity at takeoff, and mean force of acceleration thru the take-off run.
Let's take a closer look.  During takeoff, aerodynamic drag, lift-induced drag, and rolling resistance comprise forces opposing the accelerating thrust of the propeller.  During the take-off run, lift of the wing reduces rolling resistance by taking weight off the landing gear.  However, as the aircraft is accelerated, lift from the wing also creates drag and the force of this drag increases as speed of the aircraft, and hence force of lift, increases.  Included in resisting forces is aerodynamic drag of the aircraft itself (i.e landing gear, canopy, antenna mast), as well as drag caused by portions of the aircraft in the slip-stream flow of the propeller.  So, for any plane to take off, especially in still air, the force of acceleration must, at the start, move the aircraft against resisting forces that are due to the initiation of lift and dead weight (mass inertia) of the aircraft itself, drag caused by resistance of wheel bearings and landing-gear wheels rolling on the ground, aerodynamic drag caused by the aircraft fuselage and other appurtenances such as cowl vents, induction intake, and engine-cooling inlet.  All of these opposing forces must be overcome by thrust of the propeller. That thrust is developed through rotation of the propeller by the aircraft engine.
There are also several unknown factors.  For instance, given the presumed surface condition of the runway, and still air, we could assume minimal rolling resistance and optimum conditions for aircraft performance upon which to base an analysis.  With little information regarding piloting practice with this airplane, we have to presume the most conservative practice in operation of the aircraft, and use that as a starting point.  And we need additional information about the airplane and its propeller.  Some historical data and relevant information are available, however.  Most of the field test data for Spitfire take-off measurements, among other things, were measured at grass airfields near sea-level.  Data during these tests regarding wind, temperature, and pressure, were noted.  A host of specific information about the aircraft being tested was carried in the test reports.  These data include engine type, propeller blade dimensions, and all-up weight of the aircraft tested.  Exactly the information needed upon which to make an assessment of aircraft take-off performance.  With this information, the propulsive force during takeoff can be estimated, as can the time and distance required for takeoff.  These estimates can be compared with field measurements.
But there are additional, basic primary considerations: This aircraft has a tail wheel.  Consequently, as this aircraft is accelerated to take off, the tail is raised while keeping the nose slightly elevated.   In attempting to determine the most reasonably short time and distance to takeoff, one would presume the aircraft would leave the ground at airspeeds just above stall velocity.  For instance, a rather basic standard procedure in computing take-off airspeed for an aircraft of this type, is to a) assume a representative take-off lift coefficient at stall and determine the consequent stall velocity, then, b) multiply that velocity by a factor of 1.2 to assure sufficient airspeed to be in the positive command region of the power curve as the aircraft achieves flight velocity.  This assures that as the pilot folds the landing gear and the aircraft leaves ground-effect, sufficient airspeed is available to maintain control.  However, on takeoff, as the aircraft is near its lowest possible flight velocity and throttled at full power, the propeller slip-stream will have a significant influence on lift.   Consequently, to examine the Spitfire time-to-takeoff problem given a general approach and relevant factors, as just previously discussed, we must also consider the propeller slip stream and its influence on lift.    And finally there is aircraft pitch.  In addition to the propeller slip stream, we must account for the attitude of the wing in generating lift at takeoff.  By adjusting pitch, take-off velocity can be closely determined so that calculated take-off time and distance can be adequately compared with actual field measurements.   Essentially, this total process gives us a reality-check on our results.
The propeller is, perhaps, the most significant element in aircraft performance regarding this airplane.  Spitfire aircraft were operated on takeoff by advancing the throttle to rated take-off power at full boost.  As this occurs, the propeller generates tremendous thrust by inducing airflow through the propeller disk. As aircraft motion is initiated at the start of the take-off run, the force of this thrust can well exceed 2400 lbs.  As this flow passes behind the propeller, the diameter of the induced flow is contracted and the flow velocity is increased by a factor of about two.  This accelerated flow is the propeller slip stream, which then flows along and over the fuselage, and consequently over the near-fuselage, inner portion of the wing.  A resulting favorable consequence is that this higher-velocity slip-stream flow augments lift of the wing.
So what happens as the aircraft begins to move?  With full power, thrust of the propeller, the accelerating force moving the airplane, is at maximum.  This thrust, at zero forward velocity, is called static thrust.  Just as the plane begins to move, thrust becomes no longer static yet propeller efficiency increases.  Once in motion, available thrust from the propeller is consumed by opposing resisting forces due to rolling resistance of the aircraft as the run begins, and ultimately just aerodynamic drag, induced drag, and lift remain as the aircraft achieves flight.   The sum of these resisting forces over the course of the take-off run is taken to reduce available thrust of the propeller in linear relation to the square of the velocity of the aircraft. Consequently, one may calculate the accelerating force available from the propeller as a linear function of the square of the velocity of the aircraft.   The aircraft, of course, will achieve flight at the moment that lift is equal to weight of the aircraft.  Nevertheless, in order to determine the time and distance this will incur, we must know the aircraft weight (of course) and landing gear rolling resistance at the start of the run, area of the wing, slip-stream velocity due to the propeller, the resulting effective lift coefficient being developed by the wing, and ultimately, velocity and drag of the aircraft at takeoff.
And now a word from our sponsor –

Suppose we know the velocity at which an aircraft will take off, and the thrust – the force of acceleration – necessary to accomplish this, then what is the time and distance necessary for the aircraft to achieve this velocity? $  $ Let's look at the math…
We work with variables $m$ = mass, $F$ = force, $t$ = time, $V$ = velocity, and $S$ = distance.  In this case, we take $F$ to be the mean force thru the path traveled.  If we already know $m$, and forces opposing $F$ are linear with regard to $V^2$, then these aspects follow:
$$F = m \cdot a$$
$$a = \frac{F}{m}$$
$$a \cdot t = V$$
$$V \cdot \frac{t}{2} = S$$
$$so \       \ V = \frac{2S}{t}$$
$$but \      \ t = \frac{V}{a}$$
$$therefore \     \ t =  \frac {m \cdot V}{F} .$$
Consequently, with already given mass $m$, if we know the take-off velocity $V$, and mean accelerating force $F$, then we can determine the time to takeoff.  Now, however,
$$given \     \ a = \frac{F}{m}$$
$$then \     \ V^2 = 2\ \ \frac{F}{m}\ S $$
$$reworking, we find \     \ S = \frac{m V^2}{2 F}  .$$
Consequently, again, with given mass $m$, by just knowing the take-off velocity $V$ and mean accelerating force $F$, we can determine also the distance required for the take-off run.

Given what we need to know, how was Spitfire take-off time and distance calculated?  In the abstract, one must calculate the take-off velocity first, and then determine the time and distance needed for available thrust to achieve that velocity, presuming available thrust, opposing drag, and consequent acceleration, are linear in relation to the square of velocity.  Available thrust is estimated as being equal to static thrust less opposing drag.  For the question at hand, the calculations were based on an empirically based understanding of propeller thrust, an accounting of the slip-stream influence on lift just as the aircraft achieves flight velocity, and conceptually direct aspects regarding drag, acceleration, velocity, and distance.  Resulting time and distance are dependent on a determination of the mean force of acceleration thru the takeoff run.  In short, all we need to know to determine take-off time and distance, is the velocity of the aircraft at takeoff, and mean thrust (force of acceleration) during the takeoff run.   That mean force is determined in relation to the thrust at the start of the take-off run, and thrust as the aircraft achieves flight.
Let's take a quick descriptive overview of the computational accounting of thrust, drag resistance, lift, and velocity at takeoff.  Remember, the aircraft is very near or at its stalling velocity at takeoff save for the higher-velocity, propeller-accelerated slip-stream flow over the wing. The significance of the results will be summarized.  Here is the process –

Calculate the estimated stalling velocity at takeoff using a simple estimate of maximum $C_L$ at stall.  Adjust $V_{stall}$ by a factor of 1.2 to obtain estimated take-off velocity, $V_{t.o.}$.  Derive the estimated $C_L$ at takeoff from the estimated $V_{t.o.}$.
Calculate propeller static thrust and slip-stream velocity.  Then, for estimated dimensions of the fuselage frontal area, determine the slipstream diameter and region of the slipstream flowing over each wing.
The revised $C_L$ allows us to calculate the effective $C_L$ due to the slip stream. This requires knowing the specific wing chord and span dimensions, and consequent free-stream velocities relative to the wing, both interior to and exterior of the slip stream. We will also need to know the aircraft pitch and resulting angle of attack of the wing for each of the wing areas relative to the slip stream.  For the total wing, the effective $C_L$ and $V_{t.o.}$ is now determined.
Using the aircraft polar, calculate the force of drag on the aircraft at takeoff velocity.  Also, determine the rolling resistance force of the aircraft at the moment the take-off roll begins.  The mean thrust of acceleration due to the propeller is determined at the start of the run, and end of the run, using these values.  The mean force of acceleration is determined as $$F = \frac{F_s – F_e}{ln (\frac{F_s} {F_e})}$$ where $F_s$ is static thrust less rolling resistance starting the run, and $F_e$ is static thrust less total aerodynamic drag just as flight velocity $V_{t.o.}$ is achieved.
Determine consequent time and distance for takeoff using the mean force of acceleration during the run, and the determined velocity at takeoff.  Note: The mean force of acceleration is naturally biased toward the end of the take-off run.  Consequently, within limits, errors in the initial determination of propeller static thrust have a minimal consequence to our final answer.

The actual field assessment reports of performance of these WWII UK Spitfire aircraft can be reviewed at this site.  Calculated performance of two aircraft, K.9793, and P.7280, was compared with field tests.  These two aircraft had published results estimated for zero wind and standard atmosphere given time-at-test conditions at, or very near, sea level.  Calculated results, herein, are taken at sea level. Note: In order to be comparable with field measurements, without error, all results were calculated in English-system units, and are so presented, herein.
For aircraft K.9793, a Mark 1 machine, the calculations were for the aircraft as equipped, and the salient following were ascertained:  Propeller diameter, 10 ft 09 in.  Blade chord at standard 0.7r position, 8.72 in. Rated power at takeoff, 1030 hp @ 3000 rpm.  Reducer, 0.477:1. Static thrust estimated at takeoff, 2413 lb.  Mean thrust thru the take-off run, 2316 lb.  Aircraft take-off weight and pitch, 5,935 lb @ +3.4deg.  Take-off run time at distance, 12.39s at 321 yds.  Documented time and distance, estimated for no wind - standard atmosphere:  12.5s at 320 yds.  Propeller fitted: dual pitch, 3-blade de Havilland with forged and machine-finished duralumin blades.
For P.7280, a Mk-II machine, the standardized aircraft was as follows: Propeller diameter, 10 ft 10 in. Blade chord at standard 0.7r position, 10.5 in.  Rated power at takeoff, 1175 hp @ 2850 rpm.  Reducer, 0.477:1.  Static thrust available at takeoff, 2859 lb. Mean thrust thru the take-off run, 2750 lb.  Aircraft take-off weight and pitch, 6172 lb @ +6.0 deg.  Take-off run time and distance, 9.48s at 215 yds.  Documented time and distance, given for no wind - standard atmosphere:  9.5s at 230 yds.  Propeller fitted: dual pitch, 3-blade Rotol of machine-finished hygdulignum (birch/phenolic-resin laminate) blades.

Summary: So yes, we can calculate realistic numbers for take-off time and distance for the Spitfire.  Several aspects must be considered.  As previously noted, the Spitfire evaluation was accomplished by initial calculation of take-off velocity given the aircraft at its full performance with fitted propeller and Merlin engine.  Initially calculated factors include propeller static thrust and slip-stream velocity for the propeller being evaluated, slip stream influence on lift, and determination of effective lift through the take-off run. Known are aircraft weight and wing area.  We will know propeller thrust and rolling resistance at the start of the take-off run, total aerodynamic drag and velocity at takeoff, and remaining propeller thrust at the end of the run.  We only need to sum thrust and drag and determine take-off velocity to determine distance and time essentially by simple integration. Lift at takeoff is equal to the weight. The slip stream from propeller thrust augments this lift.  Time and distance are derived from the mean of the force of acceleration at run initiation and as the aircraft achieved flight, given the initially determined velocity of the aircraft at the moment of flight.  In setting up the calculation process, we need aircraft pitch to be varied and consequent results noted.  Other than given data regarding the aircraft, we only need, essentially, two resulting numbers in order to determine time and distance to takeoff.  These two resulting numbers must be calculated based upon the developed information.  Those two numbers are velocity of the aircraft at takeoff, and the mean force of acceleration thru the take-off run.

$^*$As a brief trailing end note:  Problem assessment, conceptual evaluation, background research to obtain adequate information upon which to base an analysis, mathematical development and computational procedure assembly, results assessment and validation, as well as development of the text for posting of this answer, required approximately 2.3 months from start to completion.
This was a very interesting question.  Thanks for asking!
Answer:
what else is going on that makes the true take-off time so much longer than my calculated take-off time?

I think that the poor propeller doing the whole job in front (on in the back) of the piston engine has been totally forgot! The piston engine is producing power but then it's the job of the propeller to convert this power in a thrust. The easiest way to account for propeller thrust, is just by using basic physics.
Being $P$ the power supplied to the propeller by the engine, the propeller changes this power in a thrust $T$ moving the airplane at a speed $V$. In this process, some 20% of the power (at the design point) is lost in inefficiencies which are incorporated in an efficiency factor $\eta$:
$T=\eta \frac{P}{V}$
$\eta$ depends on the speed, with a typical trend visible in the following plot¹:

As visible, $\eta$ depends on the blade pitch (as conventionally measured at 75% of the span) and on the advance ratio $J=\frac{V}{nD}$, where $n$ is the rotating speed and $D$ the diameter. The theory behind this plot and therefore the plot itself is valid for a more or less broad range around the peak: at $V=0$ it gives $\eta=0 \Rightarrow T=0$ which is not realistic since also at zero speed the propeller provides thrust. For that part of the thrust (so called static thrust) you can refer to this answer.
Just try to redo the math taking this into account and let's see if you get a more realistic result.

¹from: McCormick B.W. Aerodynamics, Aeronautics & Flight Mechanics. John Wiley & Sons, Inc.
Answer: Prop takeoff calculation is a bit tricky since so much changes between standstill and flight. The most important part is propeller efficiency $\eta_P$ which theoretically would become zero at rest if you use the usual formulas.
The trick is to not take flight speed but the speed in the propeller plane for realistic values. This can be assumed to be half of the eventual speed increase of the air going through the propeller disk $\Delta v$. Then even the efficiency formula for flight can be used throughout the takeoff run. The expression
$$\eta_P=\frac{v_∞}{v_∞+\frac{\Delta v}{2}}$$
becomes
$$\eta_{P_{at\,rest}}=\frac{\frac{\Delta v}{2}}{\Delta v}=\frac{1}{2}$$
which is consistent with reality as the upper theoretical limit for propeller efficiency at rest. Viscous and induced losses reduce this by about 20% for a constant speed propeller and possibly much more for a fixed pitch propeller and the two-position variable pitch prop of early Spitfires.
The proper form of this equation is
$$\eta_P=\frac{v_∞+\frac{\Delta v}{2}}{v_∞+\Delta v}$$
Strictly, this is the correct efficiency equation for the full speed range, but was a bit impractical in the time before computers because using it requires an iterative process in which thrust and $\Delta v$ must be balanced. Therefore, all books of authors who blindly copy what has been published before will show you only the first equation. The error is small once $v_∞$ becomes large, especially since $\Delta v$ drops with increasing flight speed.
But there are more losses. Once the prop is running, the airplane will produce aerodynamic drag even before it has started to move. The propwash flowing over hull, tail and wing root will produce viscous drag which of course only grows once the airplane picks up speed.
A very interesting paper on the efficiency of an installed propeller can be found here. By comparing the gliding qualities of a Luscombe 8E with drag in level flight, the authors measured the drag increase of the airframe caused by the propeller wake. A drag increase of 30% from the propeller effect was measured, resulting in an overall propeller efficiency of only 62% when the propeller alone had an efficiency of 81%.
The smallest bit that is still missing is rolling resistance. This adds maybe 2 - 3% of overall drag and goes away as the wing lifts the airplane up. The price for this is induced drag on the wings, of course.
Since you post on Stack Exchange, it is safe to assume that you have a computer at hand and know how to use it. Write a small program which calculates all forces and integrates them for a small time step, then repeat at the new speed until you reach lift-off speed. The correct take-off time and distance will be a byproduct of this procedure.
Comment: Please see [attached](http://www.epi-eng.com/propeller_technology/selecting_a_propeller.htm) article graphs.
Comment: @RobertDiGiovanni The author also makes the mistake of zero prop efficiency at zero speed. This contradicts his own thrust curve which looks quite realistic.