Why are number of landings logged?

Question: I have flight logs for a WW II B-24 navigator who flew with a combat crew in China Burma India.  There is a column for number of landings.  The entries range from 1 to 5 or 6, mostly 1 or 2.  The time can be as long as 8:00 to 10:00 or more.  Why is the number of landings recorded?  Is that still done today?
Comment: When you say flight logs, do you mean logs for the navigator or for the aircraft?
Answer: Yes, it's still done today, at least in military aviation.
It's to ensure that the undercarriage does not excede the number of landings it has to endure before being checked/overhauled/replaced. Landing an aircraft can typically be the most stressful regime of flight in terms of loading of certain bits of the aircraft, so it is pertinent to log how many times it happens per flight.
Comment: That's correct.
Comment: `how many times it happens per flight` you mean that a touch-and-go would be/is counted as "landing"?
Comment: @LiamBaron is this aircraft logs, or pilot logs? As a GA pilot I've always logged landings for my own FAA records, but never for an airframe or in an aircraft flight log.
Comment: though the  question seems related to the logs of a crew member, not of the aircraft.
Comment: My answer is for aircraft logs. In military this record is always kept as part of the aircraft documentation.
Answer: I'm not sure if this is specifically a military question or a general question. In general aviation (FAA) you are required to do a certain number of landings every 3 months to stay current. So landings are logged for this reason.
The specific regulation is 14 CFR 61.57 (a) (1), which says (emphasis added):

[…] no person may act as a pilot in command of an aircraft carrying
  passengers or of an aircraft certificated for more than one pilot
  flight crewmember unless that person has made at least three
  takeoffs and three landings within the preceding 90 days […]

I am not yet rated for IFR, so I'm not sure on the specifics about IFR currency mentioned in this regulation. The currency for VFR related flight differs from day and night; however, 3 night landings in 90 days will count to keep you current, while 3 day landings will only keep you current for daytime VFR.
A note on military training:
I was able to find this book/article that alludes to the training of navigators during the second world war; on P.585:

Before 1933 instruction in navigation was given only as part of pilot training.

If the individual in question had a military career and joined before '33 he may have been a pilot first and simply continued with the same log book. Why the landings were logged may just be force of habit. Either way its an interesting read on how difficult it was to be a navigator at the time and exactly what it took to become one.
Comment: Pilot logbooks also have a column for number of landings as well. (At least they did when I was flying)
Comment: They still do, at least the Jeppesen one I use has it, I believe it is there for this very reason.
Comment: @dave if i read correctly it is logbook for navigator, not the pilot. Is there any info regarding navigator logbook as well?
Comment: I can not find anything specific but the navigator certification/position is not really issued or filled anymore and thus there is not really a need for navigator specific log books. That being said there may have been specific log books for them back in the day and the navigator certification may have also had a landing requirement but I do not know so I cant comment on it as it is not really addressed in the FAR currently.
Answer: Landing is not the easiest thing on an airframe! It imparts a lot of stress, and everything we build is designed and evaluated by some statistician to endure a certain number of uses + or - some standard deviation that he/she defines. Even the keys on your keyboard are meant to endure a certain number of presses.
Additionally, if you CAN collect data that you suspect may be useful later, why not? You never know when you may want to use it for something you didn't intend to.
Not sure about the navigator though.
Comment: It would also track take-offs, of course (+/- 1) which I guess are also stressful.
Answer: For aircrew, yes there are certain requirements including no. of LDGs to be conducted within xx timeframe (typically 3 months / 90 days) in order to maintain currency. This information is recorded in the Pilot Logbook. Mine didn't have a special column (NZCAA type) so you would just write what was pertinent in the narrative, using as many lines as required.
For part 91 & 135 GA aircraft I'm not aware of any that require records to be kept of LDGs. In the airline industry cycles are recorded - this pertains more to the number of pressurisations, but on some a/c I believe LDGs are recorded also.
On the McDonnel-Douglas A-4K Skyhawks (Scooter in USN) that I maintained in the '80s we recorded LDG cycles, as well as g-force excursions. This pertains to airframe fatigue and cycle life. During peacetime fighters often last many more years (decades?) than would be reasonable for designers to estimate under true combat conditions, hence airframes can actually wear out, by reaching design time/life limits. This is especially applicable to naval aircraft operating from carriers. Even when the RNZAF operated A-4s, land based only, the initial  "thump" of LDG usually produced more g, albeit momentarily, than a maximum performance ACM manoeuvre. They could have been landed "softly"; main RWY at their home field was ~2500m, but what the heck these were carrier aeroplanes and the pilots knew it. So they took delight in extending that 500mm or so of impact absorbing oil-damped undercarriage travel (top MX bikes have only 300mm) to its full effect. That was a good reason to log landings.
JSB
Answer: I suspect it has to do with the fact that pilots want/need records of that for certification purposes and Pilot In Command can  change in the middle of a flight. Seems silly for a navigator though.
Comment: Landing is one of the more important times where navigation is needed.
Comment: @fooot Finding the airport and landing there are entirely different skills.
Answer: All the answers to date seem to have missed the most obvious part: landing the plane is by far the most difficult (and arguably the most important) part of flying, at least VFR.  So the reason a certain number of landings within a given period is required to maintain currency is simply to ensure that the pilot remains practiced in doing them.  And the reason they're logged (and logbooks have a column for it) is so that you can show currency if you ever need to.
While landings might need to be recorded for some military or commercial airframes, it's simply not true for most aircraft.

Why are number of landings logged?


what is ?client&channel=mac_bm

Question: Macbook Pro
-Safari, preferences, general, new window opens with - Favorites.
-File, new window.
I see Favorites, right click on the google icon, click on edit address.
What I see here is https:/www.google.com/?client&channel=mac_bm.
What is this?
Even when I edit the address it will go back to this one.
How is this extra part starting with the ? even added on in the first place?
Answer: It is just telling Google the type of "computer" you have.
The client is you and mac is the type of computer you have.
Comment: Thank you for explaining that part. I guess Im wondering why the google icon is the only one in favorites with this extra information added on in the url address. Im sure that Google might make my searching extra fancy with flowers if that info is attached. Where can I locate on my computer the source of the settings for favorites? Is it a folder, or terminal command?
Comment: @LisaAnn Because google wants it?? Google is probably getting from the [User Agent String](https://en.wikipedia.org/wiki/User_agent) provided by Safari.
Comment: Can I set the default (so it will stay) to be just https://www.google.com? I will look up and figure out what you say if you can tell me what to do.

what is ?client&channel=mac_bm


What's the name of this suspense/sci fi TV show from the late 70's early 80's?

Question: I remember watching a show in the late 70's or early 80's that I would like to see again. Each episode had 3 on-going stories. So each episode adds a little to each story. The episodes don't stand on their own. The first story was a wild west story: mid to late 19th century, small town, gunfighters, etc. This was no ordinary wild west story as there were aliens. I think I remember 1 episode where they showed a spaceship. That's all I can remember about that story.  The second story was about a female investigative reporter. She finds out something really big is going to happen. She doesn't know what but it's big like a terrorist attack or assassination or something. The whole story is her following clues trying to figure out what this big event is. I thought it might have been Susan Anton but I don't recognize the names of her shows in the 70's and 80's on IMDB so I don't know if it was her. I don't remember anything about the 3rd story. I saw maybe 5-10 episodes and then I don't know what happened. It might have been canceled. That's not much to go on but that's all I can remember. Thanks for reading.
Comment: Any other clues? What language was it in? What country did you watch it in? It sounds like an American show, but that can't be assumed on this site.
Comment: I watched it in Canada in English. It would definitely have been American.
Answer: I am pretty sure you are talking about Cliffhangers

...three serials were featured - a mystery, a science fiction/western hybrid, and a horror story:
"Stop Susan Williams": Susan Anton stars as a beautiful TV journalist investigating the murder of her brother, and stumbling on a vast international conspiracy.
"The Secret Empire": the adventures of a U.S. marshal (Geoffrey Scott) in the Old West who stumbles upon a futuristic underground city run by aliens.
"The Curse of Dracula": starring Michael Nouri as Count Dracula, who is living undercover as a college teacher in 1979 San Francisco.
Comment: What about Cliffhangers matches the description?
Comment: @Locutus: When you come back, please click on the green checkmark to accept if you think it is the right answer.
Comment: Wow! Brandon, I think you nailed it. That was impressive. Looks like I was right about Susan Anton but wrong about a couple of other facts. I even recognize the title. Thanks.
Comment: phantom42, I think I was wrong about the spaceship but other than that what I wrote seems very similar to the description Brandon found and posted above. I'm pretty sure the show is Cliffhangers.
Answer: I do not remember the 3 on-going stories feature, but your description resembles Outlaws...
Outlaws
Comment: Outlaws looks like just 1 story so that can't be it. Thanks.


How does a spring generate a wave? AP Physics 1

Question: The answer is C, but why? At first I thought it was B because the springs would shake the block causing it to produce a wave and as more time has elapsed there would have been more time for friction to act on the block making the block slowly returning to equilibrium. My second possible reasoning that is assuming the springs both have the same spring constant the block would remain at rest because the force each spring exerts is equal and opposite to the other spring resulting in nothing happening.
Answer: The picture you see is called a wave profile, a photograph (snapshot) of the wave at one instant of time.

The wave is travelling from left to right which means that the part of the wave on the right was formed by the motion of the block at an earlier time than the time at which the photograph was taken.
At that time in the past the amplitude of the block's oscillation was larger than at the time the photograph was taken and hence the amplitude of the wave is larger at the right hand side.
Comment: Thanks for explaining but I just want to clarify, are you proposing that the waves produced by the object was initially B then slowly transformed into C as friction had more time to act on the system?
Comment: When the mass was first released it was displaced a certain amount & so the string was displaced by that distance. There were no other waves on the string.  At time progressed the more waves of smaller amplitude where produced and those which were produced earlier had moved down the sting.
Comment: If I was to label the wave profile as if it were a graph representing the motion of the block as a function of time the vertical axis would be displacement of the block. The horizontal axis would be time with, say, the left hand being labelled zero meaning at the time the photograph was taken and the times becoming more negative (i.e. position of block at times before the photograph was taken) as one progressed to the right.
Answer: I believe you have a small logical mistake: The blocks having the same constant (which is actually not necessary to consider here anyway) wouldn't lead to the block staying at rest. The springs follow the differential force equation which allows them to oscillate. Now, from rest they wouldn't start oscillating but here a small variation is given (at time 0 it's not at rest). But again using the force equation we find that the oscillation is damped. Now the string that is attached basically just shows you a few of the last oscillations (moving from left to right) and as their amplitudes get smaller C is correct as you already knew.
The force equation i mentioned before (for one spring, without friction) would be:
$m\ddot x = k x$ where the right side is hook's law.


Does a Feistel cipher structure have to be reversible?

Question: Not sure about this question. Have thought about it, but not entirely sure whether the structure HAS to be reversible or not.
Comment: See https://crypto.stackexchange.com/questions/91497/why-is-a-feistel-network-invertible
Comment: TL;DR: the Feistel _structure_ always yields a reversible transformation, regardless of if the _round functions_ are reversible or not.
Answer: No, not necessarily however by design it has an inverse. Even the $F$ function doesn't have an inverse, the Feistel network has its inverse by the design.
Invertibility means that we have a PRP. Invertibility is only necessary when you need the reverse of the Feistel network. The archaic mode of operations like ECB and CBC mode requires the inverse since they are designed with PRPs whereas CFB, OFB, and CTR don't require it since they can work with PRFs.
Although, one can modify the Feisthe network a little to have no inverse it is more common to use hash or PRF construction to produce a cipher in CTR mode like ChaCha20, etc.
Working with PRF is better since provides a wide range of functions and eliminates the need for reverse implementation either in hardware or software that helps to reduce the costs.


How can I remove the launchpad?

Question: I don't use the launchpad, especially as it has a lot of useless apps in there that you can't delete either. For things like the dock and the dashboard I found guides online on how to remove them, but none for launchpad. Is it possible to remove launchpad completely (on OS X 10.9.4)?
Comment: As you don't use the app, please: why is its existence a concern? The app uses less than 1.5 MB space.
Comment: @GrahamPerrin It's not like it causes me sleepless nights. I just don't like useless stuff. If someone knows a way to remove it like one can "remove" the dock or dashboard by killing a process or registry entry, then that is what I am looking for.
Comment: Launchpad it self or all the Apps in contains? (make it blank)
Comment: Indeed launchpad itself not the apps it contains. If you have resources on how to remove some of the forceware apps that ship with OS X, I gladly take links in a comment, but that's not really my question now.
Comment: What is the name of the LaunchPad system service? If I could figure that out, I could write a script to kill it and keep it killed...
Comment: Ah, I see, it's part of the Dock... boo...
Answer: It is not possible to remove it but you can disable it.
In order to do so you need to:

Go into System Preferences then under Trackpad and More Gestures you
can disable pinch to launchpad
Remove it from the dock
Use FunctionFlip to reassign the F4 key to something else
Comment: my pleasure hope you like it
Comment: I like @Buscar's answer on how to empty the Launch Pad of all the Apple apps, but this is still the one closest to what I am asking. I'll award you the bounty, but if possible I'll leave the question open for now, maybe in the future there will turn up some way to do this entirely.
Answer: It should not be removed since it is a part of the OS.

At best you can completely empty it and remove from Dock.

There is a way to empty Launchpad completely—removing even Apple's
  own apps. The crux of this trick is wiping out the contents of the
  database Lion uses to know what goes where in Launchpad. To do so,
  launch Terminal (which, as always, is in /Applications/Utilities) and
  paste in this sequence of commands at the command line:

sqlite3 ~/Library/Application\ Support/Dock/*.db "DELETE from apps; DELETE from groups WHERE title<>''; DELETE from items WHERE rowid>2;"; Killall Dock

Please do not be tempted to use the brute force Terminal command like the rm , since it can produce undesired results (more problems then gain) Specialy the rm- rf is dangerous (the f) would ignore any warnings and just irreversibly delete the file. As you can see there is a Warning about "do not delete" as it is required by your OS.
Comment: Complementary to this answer: http://apple.stackexchange.com/a/146332/8546 – please note that removing Launchpad.app from OS X 10.9.5 does **not** remove Launchpad functionality.
Comment: Emptying it with the described methods works, which is nice. Other things like Dock or Dashboard are also "part of the OS", but you can get rid of them. I am still hoping for an answer that achieves that.
Answer: Exactly what do you want to do? You can remove Launchpad from the Dock. Pick it up with your Mouse, and pul it off until it disappears in a puff of smoke.
You can also go into System Preferences, and go into the Trackpad Preferences (second row), select More Gestures on the top bar, and deselect Launch Pad by removing the checkbox. This way, you don't get into LauchPad via the pinch gesture.
You can't completely remove LaunchPad since it is system software and not a normal app, but you're not forced to use it. However, you remove it from the Dock and the pinch gesture should pretty much eliminate its use.
Comment: No. You cannot completely remove it because it's really a system service. Maybe this will help: http://www.technorms.com/18829/control-launchpad. This will tell you how to get rid of all the icons in LaunchPad and then fill them with only the icons you want.
Comment: Thanks for explaining the steps to disable shortcuts in detail. My question is as stated: `Is it possible to remove launchpad completely (on OS X 10.9.4)?`
Answer: The Launchpad application link can be removed using the Terminal tool rm -rf, but this is highly inadvisable, and it will not remove the Launchpad system service, just the Application link.
If you wish to proceed anyway, here are instructions:

Open Terminal under a user account with administrative privileges. Terminal is located in the Utilities folder of folder Applications of startup disk (usually named Macintosh HD)
Enter the following command:
sudo rm -rf /Applications/Launchpad.app
You'll be prompted to enter your password, enter it (it won't appear on-screen at all, like nothing's happening, but it's working nevertheless)
If you're definitely sure you want to remove Launchpad.app, then press Enter.

Launchpad will no longer be in the Applications directory, and the Launchpad icon in the Dock will display a question mark when you attempt to instigate Launchpad.
To discard the Dock icon, drag the Launchpad icon to the Trash (bin on the far right of the dock)
Answer: LaunchPad appears to be part of the Dock rather than a separate process, so it cannot be truly disabled or deleted without disabling the Dock too. The below commands are the closest I can come to neutralizing Launchpad—save them to a script and run. There will still be a few methods of activating the Launchpad overlay, but the screen should always be empty.
This process modifies system files, so make a backup! I've only tested it on OS X 10.9 Mavericks (because I love Mavericks), but it will probably work up to 10.14 if you disable SIP, and on 10.15 with some additional tweaks.
# Remove the Launchpad app shortcut
sudo rm -rf /Applications/Launchpad.app

# Disable Launchpad Gesture on current user account
defaults write com.apple.dock showLaunchpadGestureEnabled -int 0

# Disable Launchpad Gesture on any future user account
sudo defaults write /System/Library/User\ Template/Non_localized/Library/Preferences/com.apple.dock showLaunchpadGestureEnabled -int 0

# Fix permissions on user template folder now that we've modified it
sudo chown -R root:wheel /System/Library/User\ Template/
sudo chmod 700 /System/Library/User\ Template/

# If an an app's bundle id contains a ".", exclude it from Launchpad. In practice, this rule will apply to every bundle id, excluding all apps.
echo '<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"><plist version="1.0"><dict><key>launchpad</key><dict><key>ignore</key><dict><key>rules</key><array><dict><key>bundleid</key><string>.</string><key>type</key><string>contains</string></dict></array></dict></dict></dict></plist>' | sudo tee /System/Library/CoreServices/Dock.app/Contents/Resources/LaunchPadLayout.plist

# Reset LaunchPad
defaults write com.apple.dock ResetLaunchPad -bool true

# Restart Dock and Finder
killall Dock Finder

Launchpad bothers me greatly on a philosophical level—it breaks all of OS X's UI metaphors around app bundles, double-click behavior, and loads of other things. I don't know that this will be useful to anyone else, but I wanted it to be documented somewhere.

How can I remove the launchpad?


Oscilloscope with 400 MHz but only 100 MS/s?

Question: The Tektronix TDS430A is a 400 MHz 100 MS/s oscilloscope. I know other ocsilloscopes which could be toggled between analog mode and digital mode, so that these numbers would make sense. However, it seems the TDS430A is digital only. How could they possibly measure 400 MHz with only 100 MS/s?
Comment: We had a bunch from Agilent/Keysight in my lab with 25 GHz bandwidth but only ~40 kSa/s. The newer models have boosted that to ~80 GHz bandwidth with ~1 MSa/s.
Answer: They're stating that the bandwidth of the analog front end is 400MHz.  For a periodic signal then you could fill in the waveform by sampling successive sweeps.
So you could for example see a 400Mhz sine wave on the scope (though 3dB down) with this technique.
For a single shot or non-periodic signal you would be limited by the sample rate.
From the manual:
Comment: Ah, like the LeCroy RIS (Random Interleaved Sampling) mode?
Comment: @ThomasWeller Yes, exactly.
Comment: Do you happen to know what that function is called on the Tektronix? It certainly needs to be enabled somehow
Comment: @ThomasWeller Updated my answer with the relevant section from the TDS430A manual.
Comment: I have used many models of Tek scopes and never recall having to enable this feature, it is automatically enabled at small time scales. If you have a signal that is periodic, but slightly different each time, you will get some weird ghosting.


Negative aspects of dark color scheme (dark background with light text)

Question: I am using Light on dark color scheme in my WPF application.
My question is what are the negative aspects of this color scheme and why this color scheme is not widely used?
Please follow this thread at here
Comment: You might have better luck on http://ux.stackexchange.com/
Comment: It is on topic here, but it might get better answers from UI developers at [ux.se].  Also, light on dark is hard to read and annoys the crap outta me.
Answer: Darker color scheme are often used effectively in software that focuses heavily on visual content. For example Adobe Lightroom, Adobe After Effects, Microsoft Expression Blend, and Kaxaml are are interfaces that have a dark color theme. This allows the interface to fade into the background and let the content come alive
Why is it not widely used? I guess it depends on your crowd. For these application it tends to work out great but many people don't like dark interfaces. At my company I created an interface for a very complicated piece of software using a dark UI. It helped to simplify everything and bring attention to the necessary elements at specific times. The problem was, a lot of people complained. "It's too dark," "it doesn't look good on my laptop when I am using in the bright sun" etc. Some people just hate dark interfaces.
Bottom line: if your applciation is very content driven, esp with visual content, consider a dark interface but be prepared for some opposition.
Alternative solution: provide 2 themes, one light and one dark. This is done in Microsoft's Expression Blend (although the light theme looks quite awful, IMO)
Also, it is important to note it is often a bit more difficult to get a dark interface that works well. A little more care must be given to legibility of text on the dark background (i.e. making it bright enough to be legible but not so bright that it is distracting to read.
Answer: I have two major issues with dark color schemes:

Windows (and most other OS themes) are light by default, which makes most other applications light. It is nice when all applications have consistent graphical theme.
It is much less readable when there is a lot of light around (like sun shining on your screen), and today's glossy screens don't exactly help with this.
Answer: Most people (not all) find it harder to read light text on a dark background than dark text on a light background.
It was something that was pointed out to me in school when creating powerpoint presentations, and I noticed the difference when students ignored the recommendation and did a dark background anyways.
Comment: actually it's easier to me to work with applications like Microsoft Expression
Answer: I am developing a medical application which is intended to be used in somewhat darker ambients, such as radiology laboratories, so we are using a dark UI similar to Expression Blend Dark, because we noted a light UI is too glaring in those ambients.
The application is supposed to display color images, and subtle intensity changes should be discriminated by medical staff.
A similar thing happens with Photoshop and LightRoom and any other application where color discrimination is important: the user should not be glared, either globally by overall UI brightness, either locally by high contrast in small text, for example.
One reason why we have better visual acuity with light bagckgrounds is that more light makes our pupils compensate it by contracting, thus sharpening focus. On the other hand, dark background makes us adapt to dark, and a crispy glaring light-colored text tend to "overflow" over the background with undesirable results.
There is no absolute counter-indication for using dark backgrounds, it's actually a matter of making the "light" parts have the right brightness so that they are well-seen without being glaring, and maybe having different regions of not-pitch-black, to "buffer" that glaring a little.
Hope this helps.


Relating Temperature and Battery Performance (HELP)

Question: I am a grade 11 student performing a experiment on relating how external temperature affects the performance of a battery, so its voltage and current change. I've done so much research and cant find a formula that relates temperature to any parameters of a battery. The experiment plan is to get a battery and discharge it at different temperatures but the problem is that I need to have a theoretical formula that supports the results. Could any of you please help find some formulas that I could use. Thank You.
Comment: What battery? does it have a model #?
Comment: Lithium Ion Polymer Battery - 3.7v 100mAh
Comment: `I need to have a theoretical formula that supports the results` .... what if the results of a carefully conducted experiment do not match the formula?
Comment: Nothing really, It can be blamed on sources of error and other factors in the unideal conditions. I just need a way to calculate and determine the trend.
Answer: LiPo batteries have a nonlinear behaviour with temperature and varies widely with quality of construction, although there are some generalizations.
Assumptions

Battery model specifications take precedence over generic expectations
test with controlled constant current sink vs voltage must not stay under/over voltage for any significant time.
if specs define capacity and charge cycle life, these will affect temperature results
several batteries must be tested to determine standard deviation of the experiment
example specs

search "google images" for 100mA LiPo temperature performance graphs
search battery university site for experience
search "Google Scholar, Microsoft Academic" Research-gate

define test specs, test methods ( dry ice, thermometer, test point, self-heating), measurement intervals, estimate an acceptance criteria, choose CC sink design, automate test
have fun
Comment: Thanks I am starting to understand, although is there any specific equation I can use to determine the amount of power it could deliver at -10 C rather than at 10 C
Comment: Looking at the graph it drops from 90% to 65%. Can you use a spreadsheet with curve fit?


At what time of day does time value fall off of a call option?

Question: As days tick off of call options, time value decays. My question is does that happen automatically at 9:30AM at market open or does it get continuously deducted as the day ticks on?
Answer: The time value decay is theoretically constant.  In reality, it is driven by supply and demand, just like everything else in the market.
For instance, if a big earnings announcement is coming out after the close for the day, you may see little or no time decay in the price of the options during the day before.
Also, while in theory options have a set value as related to the trading price of the underlying security, that does not mean there will always be a buyer willing to pay a premium as they come close to expiration (in the last few minutes). You can't forget to account for the transaction fees associated with buying the options, or the risk factor involved.
It is rare, but there are times I've actually had to sell in the money calls at a penny or two LESS than they're actually worth at the time just to unload them in the last few minutes before the market closed on expiration day.
Comment: Probably a better choice of word would then be something like, "time value is continuously decaying"? Because the word constant means... constant. As in, something that doesn't change. But, as you seem to know, time value decay *does* change over time.
Comment: I said the time value DECAY is theoretically constant.  Meaning that it is constantly decaying, over a period of time; at least in theory.  I did NOT say that it is A constant. BIG difference.
Comment: "The time value decay is theoretically constant" - it's definitely *not* constant! Just open an options textbook and look for the formula of theta, using any option pricing model. You'll see that *time* is a variable there. That means precisely that it's not a constant.
Comment: Since this Question with Answers was linked to a current post, some comments.  Time decay is constant and is continuously marked down by the market maker. Demand drives option price and it overrides time decay.  In its absence, the MM marks the option down continuously.  As for a pending earnings announcement, little change in price from the previous day or even a jump in price has to do with demand and implied volatility expansion.  Theoretical value is less.  Actual value is higher.
Comment: As for options trading below a few cents below parity on expiration day, that's the MM screwing you in return for accommodating you.  OTOH, sometimes the haircut is much larger than "a penny or two LESS" and  if the commissions involved are less than the haircut, one can a save a few bucks by exercising and unloading the underlying.  I don't pay commissions for assignment and exercise so I often do this.
Answer: If you're talking about just Theta, the amount of decay due to the passage of time (all else being equal), then theoretically, the time value is a continuous function, so it would decay throughout the day (although by the day of expiry the time value is very, very small).  Which makes sense, since even with 15 minutes to go, there's still a 50/50 shot of an ATM option expiring in-the-money, so there should be some time value associated with that one-sided probability. The further away from ATM the option is, the smaller the time value will be, and will be virtually zero for options that are deep in- or out-of-the-money.
If you're talking about total time value, then yes it will definitely change during the day, since the underlying components (volatility, underlying price, etc.) change more or less continually.
Answer: It has been my experience as an amateur trader, theory aside, that I generally see the time value come off at market open and not much during the trading day.
Comment: Thanks, that was the answer/dynamics I was looking for.
Answer: The time value of the option (theta) decays constantly (by the millisecond)
As it is one of the inputs to the option pricing model, it usually has a lower impact on the overall option price than other changes in the market.
As the (US) markets price options in penny ($0.01) or nickel ($0.05) increments, you will only observe these changes when the impact of theta is big enough for the market maker to increase or decrease his bid or offer by another $0.01 or $0.05.
This will happen slowly throughout the day but should be more significant from one day's close to the next day's open particularly if there is a weekend or long weekend in between.
Answer: This has been my observation in the markets pertaining to option decay. Bulk of the decay happens in the first 15 minutes of trade at market open. Rest of the decay usually happens in pulses whenever market breaks out of ranges intraday. So if its call option and market breaks a range to the downside, call option will experience decay in proportion to time elapsed since open.


Any downsides to "Employee of the Month" edict?

Question: As the title states, is there any downside other than the obvious $350/month charge for the edict?  Will the workers have less fun, be more tired, or anything else one should be aware of?
Answer: Source

According to this, which is exactly what the game notes say aswell. The only downside is the fact that you're shelling out $350 per month.
Most edicts will out right tell you the downside or negative aspects of edicts.
Comment: Yes. However, it is also known that workers will leave the workplace when they need rest, they need food, and when they need entertainment. If they work double shifts there will be less time available for that - which might (should) lead to an overall drop in Happiness numbers for Food, Fun, and maybe Job. It's not so easy to confirm however.
Comment: Yes, I understand, but that's the whole point of this particular edict, you're paying a monthly fee to avoid them from complaining from them being overworked. Furthermore, I've never once had to use this edict.

Why don't you just play a map and run this edict nonstop and see what happens with industrial workers. It should be easy to confirm.
Comment: It should also be noted that this is one of these most expensive edicts in the game. So that should give you a clue that the only negative aspect is the monthly expense. If you have a small industral complex than you'll likely lose money. But if 7 to 8 finished goods industries running, then it might be worth it. But ironically if you had that many finished goods industries, you should be rolling in the money. So you wouldn't need the edict.
Comment: Right :-)  Well the whole point of raising the question here was to seek out, if anyone had already done any in-depth testing for any negatives _apart_ from the obvious $350 monthly charge. I will test it, as soon as I figure out a reasonably controlled way of doing so.
Comment: I've also taken it upon myself to ask this question on reddit on your behalf. https://www.reddit.com/r/tropico/comments/bdqvwo/any_downsides_to_employee_of_the_month_edict/


Temperature: Why a Fundamental Quantity?

Question: Temperature is just an indication of a combined property of the masses of the molecules and their random motion. In principle, we can explain "no effective energy transfer between two conducting solid bodies in contact" via a condition in terms of the masses of the molecules and their speeds such that due to the collisions of molecules of two bodies, net energy transfer between two bodies is zero. But it would be a complex calculative work to derive this condition analytically so we use the temperature scale just as a phenomenological parameter to easily determine the condition of "no net energy transfer between conducting solids" for practical purposes. But it does not denote any fundamentally new property of the body separate from the already known mechanical properties of the same. Then why do we call it a fundamental quantity, e.g. in the SI list of fundamental quantities?
Comment: on a micro scale temperature does in fact also have an (abstract meaning) as $T=\frac{1}{k_B}\left(\frac{\partial \ln (\Omega)}{\partial E}\right)^{-1}$. This is a definition used in statistical physics.
Comment: It's exactly that - it's easier, simpler, as well as easier to explain temperature. On a macro scale, it does appear fairly fundamental.
Comment: There is no such thing as an "SI list of fundamental quantities"; the concept you refer to is that of a *base* unit, and it is important to use the correct term. This question should be edited to use correct language.
Comment: What is your physics level? The equation Hagadol posted means that temperature is the variation of energy with respect to the number of microscopical states.
Comment: Temperature is an SI unit. It is not a fundamental quantity in the sense that you mean and is not called that in the SI system (joules, in contrast, is a more fundamental concept). Lots of units are not "fundamental" and are not measurements of something fundamental (see also, e.g., moles).
Comment: @Kvothe, what about temperature sympathetic links, are possible?
Comment: You will likely find [this post](https://physics.stackexchange.com/questions/231017/is-the-boltzmann-constant-really-that-important) interesting.
Answer: It is one of the fundamental questions in classical thermodynamics.
Temperature: Temperature is the
parameter that tells us the most probable distribution of
populations of molecules over the available states of a system at
equilibrium.
We know from Boltzmann distribution:
$$\beta=\frac{1}{k_B T} $$
The fact is that $\beta$ is a more natural parameter for expressing temperature than T itself.
Absolute zero of temperature (T = 0) is unattainable in a
finite number of steps, which may be puzzling, it is far less surprising that an infinite value of (the value of $\beta$ ' when T = 0) is
unattainable in a finite number of steps. However, although $\beta$  is
the more natural way of expressing temperatures, it is ill-suited to
everyday use.
The existence and value of the fundamental
constant $k_B$ is simply a consequence of our insisting on using a
conventional scale of temperature rather than the truly
fundamental scale based on $\beta$. The Fahrenheit, Celsius, and Kelvin
scales are misguided: the reciprocal of temperature, essentially $\beta$,
is more meaningful, more natural, as a measure of temperature.
There is no hope, though, that it will ever be accepted, for history
and the potency of simple numbers, like 0 and 100, and even 32
and 212, are too deeply embedded in our culture, and just too
convenient for everyday use.
Although Boltzmann's constant $k_B$ is commonly listed as a
fundamental constant, it is actually only a recovery from a
historical mistake. If Ludwig Boltzmann had done his work before
Fahrenheit and Celsius had done theirs, then it would have been
seen that ' was the natural measure of temperature, and we might
have become used to expressing temperatures in the units of
inverse joules with warmer systems at low values of ' and cooler
systems at high values. However, conventions had become
established, with warmer systems at higher temperatures than
cooler systems, and k was introduced, through $\beta=\frac{1}{k_B T} $, to align
the natural scale of temperature based on ' to the conventional
and deeply ingrained one based on T. Thus, Boltzmann's constant
is nothing but a conversion factor between a well-established
conventional scale and the one that, with hindsight, society might
have adopted. Had it adopted ' as its measure of temperature,
Boltzmann's constant would not have been necessary.
Conclusion: Temperature, actually is NOT a fundamental quantity. It is just for convenience and historical reasons we consider it as fundamental quantity.
Reference: Peter Atkins -The Laws of Thermodynamics: A Very Short Introduction
Answer: As I already commented one can introduce the Temperature of a gas by relatively modest assumptions. Here is a sketch of a derivation I hope to remember correctly:
The definition of temperature is then based on the concept that if two gases are brought together the entropy will maximize. This condition can be simplified to the condition, that the two inverse "temperatures" have to be the same. This yields the formula I already gave, namely $$\frac{1}{k_B T}=\beta= \frac{\partial \ln (\Omega)}{ \partial E}.$$
Here, $k_B$ is a scaling constant,$E$ is the energy and $\Omega$ something like the number of available states for the system with a given energy. For a proper derivation you can have a look in practically every book on statistical physics.
Answer:
So why do we say it a fundamental quantity?

You do not have to say such thing, but temperature is very basic and important concept. In thermodynamics, it is the only quantity that always gets equalized in transition to thermodynamic equilibrium - pressure nor chemical potential needs to equalize, but temperature has to (except perhaps for systems in strong gravitational field, where the lower parts are predicted to have higher temperature than the upper parts).
Answer:
"Temperature is just an indication of a combined property of the masses of the molecules and their random motion."

No! Temperature is not always limited to being a combined property of the masses of the molecules and their motion. Of course, this was the first scenario where the notion of temperature became apparent to the humans historically, but our modern notion of temperature transcends this primitive notion of temperature as being some kind of a measure of the kinetic energy of molecules. Rather, the temperature is a quantity that generically represents whether a given system will be in an equilibrium when kept in contact with another system. More specifically, it represents whether the two systems can exchange energy with each other and attain a combined final state with more number of compatible microstates than the number of microstates compatible with the combined initial state of two systems. If they can then they would evolve to that state and otherwise not. In fact, we don't even postulate that such a quantity must exist but it follows from the basic postulates of statistical physics that such a quantity would exist and then we identify this statistical quantity with the thermodynamic temperature to make a contact between our theoretical framework and the experimental results---as needed to be done in case of any theoretical framework.
Now, the key is that this statistical quantity that we identify with the thermodynamic temperature is rather general and conforms to our primitive notion that ''the temperature has to do with kinetic energies of molecules'' only if the Hamiltonian of the system is that of a classical ideal gas, $H=\displaystyle\Sigma_{i}\dfrac{p_i^2}{2m}$. There certainly exists very many Hamiltonians (that is to say, very many systems) where there might be many other terms in the Hamiltonian which do not represent the kinetic energy of molecules and there might not even be any notion of the motion of molecules at all (e.g., there are no kinetic energy terms in the Hamiltonians representing magnets etc.--and yet, the concept of temperature as a quantity defined in the statistical sense we discussed makes perfect sense on its own!) So, in short, the text in the blockquote is not really true in the light of our modern understanding of temperature.
Now, as to whether the temperature is a fundamental quantity or not, as clearly evident from the statistical definition of temperature, the quantity called temperature emerges from the more basic statistical considerations and is not thus fundamental in the sense that it is not irreducible to more basic notions. But certainly, it is a very important quantity for both theoretical and experimental purposes and can be regarded as fundamental in this sense. Whether it absolutely requires a unit of its own has a definite negative answer. But again, from a theoretical point of view, every quantity can be expressed in terms of just one unit, say $eV$---but clearly, it wouldn't be convenient and thus, it is certainly wise to use a separate unit for temperature (and other quantities as well) despite the fact that we can use a more unified framework of units.
Comment: "But again, from a theoretical point of view, every quantity can be expressed in terms of just one unit, say eV" We can actually go even further than that, fix G = 1 and express even energies as dimensionless quantities with the implied meaning as multiples of the Planck mass, just like dimensionless velocities are fractions of c and dimensionless actions are multiples of h
Answer: A quantity is called as fundamental quantity if it can't be explained in terms of other fundamental quantities:

we know temperature is the vibrations and collision of constituent atoms and molecules and
vibration can be explained by other known fundamental quantities.

Hence temperature is not a fundamental quantity.
But wait... Kelvin is a fundamental unit!
In the past, temperature was used for the measurement of "hotness". For that we (Humans) devised different temperature scale and laws like the Zeroth Law of Thermodynamics.
Then as we encountered more physical phenomenon such as thermodynamic equilibrium, we found that this quantity, the temperature, is the same for two systems in equilibrium.
At that time we usually dealt in macroscopic domains but as we  started to research microscopic domains, we can explain temperature as the vibrations and collision of molecules and atoms.
It's a lot easier to measure temperature than to measure the motion of component particles. Hence, we can accept it as a fundamental quantity.
Answer: It is just a scale to get thermal equlibrium problems easily but defined in such a way that it can not be expressed only in the terms of the other fundamental quantities.So it is a fundamental quantity.
Answer: Just as an adder to previous answers: in thermodynamics, you most often see temperature associated with R (or k in statistical thermo), i.e. most formulas have RT or kT as a parameter. The combination RT is thermodynamic temperature and the units are J/mol, so no need for another fundamental unit for temperature. Temperature can be fundamentally defined as length squared over time squared.
Answer:
But it would be a complex calculative work to derive this condition
analytically so we use the temperature scale just as a
phenomenological parameter to easily determine the condition of "no
net energy transfer between conducting solids" for practical purposes.

I'd say temperature is just a general "tool". Actually all concepts defined by statistical physics are such "tools". All properties of a system derive from its Hamiltonian and the underlying mechanical laws. Statistical physics introduces general concepts to bypass working with the explicit equations of motion, ideas that work for all Hamiltonians and all underlying interactions.
As mentioned by @youpilat13, the temperature defined in statistical physics is more general than the idea of kinetic energy per participle (more exactly per degree of freedom). The temperature is equal to the kinetic energy per degree of freedom essentially if the Hamiltonian has the form:
$$H=U(q)+\sum \frac{p_i^2}{2m_i}$$
where $U$ is a scalar potential. See: Statistical mechanics definition of temperature as the average kinetic energy. This is a consequence of the equipartition theorem.
The temperature is defined more generally as:
$$T=\left(\frac{dE}{dS}\right)_V$$
$V$ is not always the real volume, it can be used to refer to any external intervention. The second law implies that the temperature defines the direction of energy in absence of external intervention: heat flows towards the body with lower temperature. It is easy to see. Two bodies $A$ and $B$ in thermal contact but thermally isolated from the rest of the universe are such that:
$$ \frac{\delta Q}{T_A} - \frac{\delta Q}{T_B}\geq 0$$
This idea is general. Whenever a variable $X$ is both extensive and conservative like the energy $E$, you can define:
$$T_X=\left(\frac{dX}{dS}\right)_V$$
And then, $X$ will flow in the direction of decreasing $T_X$. An example is $X$="the number of particles of hydrogen". All this to say that what is more fundamental is $S$, and $T$ is somehow a little tool used about energy to predict the direction of exchange as it could be done for any other conservative extensive quantity.


WEHRE IN array values using stored procedure

Question: I have a select query that uses a WHERE IN clause in a MemSQL database. The list of values searched in are a result of another select query.
Before, I inserted the values for that clause as a string through a web service like so: (1,2,3..).
Now I want to move the second query into a stored procedure, and have the values mentioned above be a part of the parameters for that procedure.
Say I have a table:
create table t (num int);

Then when I try to create the sp:
DELIMITER //
CREATE PROCEDURE test (nums ARRAY(INT)) AS
BEGIN
ECHO SELECT * FROM t WHERE num IN nums;
END //
DELIMITER ;

I get:
ERROR 1064 (42000): Compilation error in function `test` near line 3: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'nums'

So apparently it doesn't work that way. Is there way I can get this to recognize the data type I'm inserting?
I want to avoid manipulating strings, but if there is no choice, would it require running the query as a string in the stored procedure?
Answer: Try adding nums in brackets so it can complete the required syntax.
DELIMITER //

CREATE PROCEDURE test (nums ARRAY(INT))
AS
BEGIN
ECHO SELECT * FROM t WHERE num
IN(nums);
END //
DELIMITER ;


Strange message declaring a Pointer[void] in a NativeCall perl6 module

Question: These snippets of code may seem odd, it's because I started with my original code and cut off pieces until I arrived to the minimal set of instructions that reproduced the error. So bear with the apparent uselessness.
There are two perl6 modules, one uses the other one, and a program.
This is the first module:
unit class test1;

use NativeCall;
use test2;

method test
{
  my Pointer[void] $dummy .= new;
}

The second module is included by the first one, but no part of it is actually used:
unit module test2;

use NativeCall;

class A is repr('CStruct') is export {
  has Pointer[void] $.wrongdoer;
  has int32 $.a;
}

The program creates a test1 object and calls the test method:
use lib '.';
use test1;

my test1 $t .= new;
$t.test;

This program outputs an error, apparently caused by the assignment in the class test1's method test:
Type check failed in assignment to $dummy; expected NativeCall::Types::Pointer[NativeCall::Types::void] but got NativeCall::Types::Pointer[NativeCall::Types::void].new(0)

If I comment out the $.wrongdoer in the second class, the program executes with no error.
I'm running rakudo 2018.06.
Is this a bug in the NativeCall module or something else I fail to see?
Comment: If you remove the `[void]` it doesn't generate that error.
Comment: Declaring `test1` and using it by itself also works... Declaring A and instantiating it causes no problem either, either in 2018.03 or 2018.06. Can you please try and check again?
Comment: I think this has been fixed. (A 2022 Rakudo doesn't generate an error.)
Answer: As suggested by Brad Gilbert, removing the [void] stops the spooky action at a distance.
Comment: I think this has been fixed. (A 2022 Rakudo doesn't generate an error.)


Should I learn the research methods first?

Question: I'm going to start my PhD in 10 month time. My general area will be HCI (Human Computer Interaction). Should I read papers and look at the method used in that paper then read about that method? or should I read about most research methods in the area before I start reading any paper?
Comment: It's not like you'll ever "finish" (or almost finish) reading the papers _or_ learning methods. If things go well, you'll still be working on both of those tasks for many many many years :) I would definitely tell my students to do both of these things in parallel!
Answer: Learning styles differ, but most people find it easier to understand a method as they see it applied. In order to grasp a solution, you need to understand what problems it is trying to solve.
I would probably start with one or more applied papers in the field. Though it's fine to jump into more detail about the methods as soon as you have questions. Really this need not be two separate activities.


Can I stay in Turkey for ~180 days by aligning two 180 day travel visas

Question: That is, I would like to stay in Turkey for 180 days. Is it possible to do this by first applying and getting the eVisa 90 days before my arrival in Turkey so the duration of my stay lasts through the second half of the 180 day window. Next, after those 90 days, I would leave the country for a day and get another eVisa, then enter the country again for another 90 days. This would essentially let me stay in Turkey for about 180 days. Is there some flaw in this plan?
Answer:
Is there some flaw in this plan?

Yes. They might not give you the second visa. And, even if they give you the visa, they might not let you in.
I don't know about Turkey but some countries aren't happy about people chaining together visitor visas to spend a longer period in the country than a visa normally allows. It's safest to get a visa that allows you to stay for the time you want to stay. If no such visa exists, then you must be prepared for the possibility that you won't be able to make the visit you want.


Can I turn off banner ads in code?

Question: I set up my app to show banner ads at the bottom. Is there a way to turn off the ads in code? I want to let the users upgrade to an ad-free version of my app. But since the presences of ads is specified in the build hints, there doesn't seem to be any way to turn them off once the user buys the ad-free version. Do I need to upload two versions of the app? Will the user need to download the ad-free version once they make the purchase?
Answer: There is no API exposure of the banner ads builtin to Codename One so there is no way to toggle them in code. You can use the interstitial ads or use that code as the basis for creating your own banner ad support.
Comment: You didn't mention the com.codename1.components.Ads class. Is this class not used anymore?
Comment: No, it isn't used by the banner ad code. It worked with older ad providers but doesn't work with modern ad frameworks.

Can I turn off banner ads in code?


Need Advice on designing ATL inproc Server (dll) that serves as both a soure and a sink of events

Question: I need to design an ATL inproc server that besides exposing methods and properties, also can fire events (source) and serve as a sink for a third party COM control that fires events.  I would assume that this is a fairly common requirement.  I can also foresee several "gotchas" that I would like to read up on before commencing the design.  My questions/concerns are:

Can someone point me to an example?
Which threading model to use?
Should I have a seperate COM object for the sink?
Should I, and how do I, protect certain memory.  For example, my server will receive data from the third party control.  It will save this, and in some cases, fire an event to interested clients.  The interested clients will request the data through a standard method or property.  I did try to research this myself. I can find many  examples of COM servers that are soures, and some that are sinks, but never both.  The only post I did find was this:
http://www.generation-nt.com/us/atl-control-an-event-source-sink-help-9098542.html
Which strongly advocates putting the sink on a seperate COM object.

Any leads, tutorials or ideas would be much appreciated.
Thanks,
Andrew
Answer: Check out ATL connection points, which will take care of the boiler plate code.  This link provides an over view and sample code: http://msdn.microsoft.com/en-us/library/h7kad5hw(v=vs.90).aspx


Will changing my Apple ID affect any apps that I have purchased?

Question: I want to change my Apple ID, simply just because I don't want to use that name or that email address anymore.  Will it affect any apps that I have purchased in the past with that old Apple ID? If I have deleted one of those apps that I purchased, will I have to repurchase that app again with the new Apple ID?
Answer: If you have an Apple ID that ends with mac.com or me.com then you probably can't, otherwise this FAQ covers how to change your Apple ID.

Go to http://appleid.apple.com/
Click "Manager your Account"
Login to your account
Click on the "Name, ID, and Email Address" option on the left
Next to Apple ID click the Edit button and fill out your new details.

Purchases are bound to your account, so short of deleting your account you should be fine. (In fact you can still access old purchases by logging into the relevant store with your old account according to the FAQ about Apple ID
Answer: Not sure if you have a @mac.com or @me.com apple ID.  Those can cause problems, and cannot be changed.
If not, I think you can change your email and name for your apple Id.
Apple has support directions in KB HE40 and an Apple ID FAQ in KB HE37.

How do I change my Apple ID Name or personal information?
You can change your Apple ID Name at My Apple ID. Select your country and language, enter your desired changes, then click the Continue button. Changes take effect immediately. You can also use My Apple ID to change your personal information, such as your mailing address or email address. See How to change the name you use for your Apple ID if you'd like more information.


Name change after 30 days?

Question: So I recall somewhere (probably in the Gemara) that if a person who is called by a certain name for +30 days, that name gets to be his new name, is that true? I know the sages always said stuff that has really important meaning behind it, so is this a deep meaning thing, something that we used to do, or literal thing that we still do?
Comment: There's a custom of giving a very sick person a new name; I wonder if that ties into this somehow.
Comment: Re "I know the sages always said stuff that has really important meaning behind it, so is this a deep meaning thing, something that we used to do, or literal thing that we still do?": Do you mean that if it's something we don't do and didn't do then it has deep meaning but if it's something we do or did then it has no deep meaning? Why can't it have deep meaning even if it's something done?
Answer: I think you're thinking of Bava Basra 167b. In context, the Gemara is questioning whether the scribe needs to know the man's and/or woman's names on bills of divorce or receipt ahead of time. The concern is that there might be two men with the same name in the city, or two women with the same name in the city, and the man may give it to a woman who's not actually his wife, she will think she's divorced when she isn't, and she'll remarry while still being married already. In that discussion, the Gemara asks:

וליחוש דלמא אזיל למתא אחריתא ומחזיק ליה לשמיה ביוסף בן שמעון וכתיב גיטא וממטי ליה לאיתתיה דהיאך
But we should be concerned that maybe he'll go to another city, establish a false name for himself as Yosef ben Shimon, write the bill of divorce and give it to the wife of another man [whose name actually is Yosef ben Shimon]!

The Gemara answers:

אמר להו רב הונא בר חיננא הכי אמר רב כל שהוחזק שמו בעיר שלשים יום אין חוששין לו
Rav Huna bar Chinana said to them, thus did Rav say: Anyone whose name has been established in a city for thirty days, there's no concern about him [that the name is false].

If this is indeed what you're thinking of, then it doesn't sound like this is something that was regularly done, so much as a theoretical case that they were addressing. When you ask it there's a "deep meaning" or if it's "something that we used to do, or literal thing we still do," the answer seems to be no to each of those questions.

Name change after 30 days?


Asp.net setting some context for a Custom UITypeEditor from parent form at Design Time

Question: Trying to craft a way for our designers to create custom asp.net webforms for our customers.  The basic idea is that we have a general set of fields that can be saved, with each customer using a subset of those fields, each customer may have it's own names for similar concepts (ie one customer may use 'patient' and another 'customer').  Staying in customer context will help the designers build the correct form to meet the customers needs.
Now to do this I need to get as much as I can into the design experience as possible.  I have a set of custom controls that derive from base controls like asp:TextBox and implements an interface to allows me to iterate over the controls and insert values from a data store, or fetch values to persist (Done).  All of these controls need to be bound to a data point in my record object.  I have a metadata system set up to allow the binding, but where I am running into trouble is in getting the list of available fields into a UITypeEditor.  Namely, I haven't figured out how to (at design time) set the customer context on the form, and then access and use that value on each controls custom property editor (also at design time).  Is this possible?  Am I looking at this problem the wrong way?  A form always has 1 and only one customer context.  So in my forms project, each form will have a different customer id set to it.
As a second question how can I debug these editors?  There is an expectation of web context in the editors, but there is no asp.net property grid.  and even if there was, the editors are winforms components that wouldn't run in a browser.
I can include the code I currently have if it simplifies the problem, but even a simplified example is a half dozen classes.
Answer: I resolved these issues, posting here in case a general solution can be useful to anyone in the future.
I was able to get around this problem a bit by going the other way.  My parent Page iterates over it's controls, and sets the CustomerId on all the controls that implement a specific interface.
As for debugging.  Some refactoring got me to a place where I can easily swap out the webforms specific parts of  my implementation for testing.


Boolean aura attribute not working in lightning component

Question: I came across a weird behaviour on our sandbox org which is currently on Winter 24. We have several lightning components that we use in all different kind of screen flows.
For whatever reason aura attributes from the typ "Boolean" are no longer working - no matter which lightning component. Basically it is not expection true/false anymore. I played around with other types like "String" and "Integer" which work totally fine.
Here is an example attribute:
<code><aura:attribute name="showCurrentUserAccounts" type="Boolean" default="true"/>
</code>
and this is what it looks like in the flow when trying to access it:

What do I miss? I cannot reproduce this in production:

Thanks in advance!
Answer: Well, looks like Salesforce just wanted to make a fool out of me. New day and it is working again...


Was the Pack's memory of eating the Principal ever mentioned again?

Question: In Buffy the Vampire Slayer Season 1 Episode 6, Xander and 4 other students are possessed and they eat a pig. At the end they are all freed of possession and Xander claims memory loss. However Giles tells him when they are alone that he knows Xander didn't lose his memory and I think Xander mentions this in a later season as well. My question is was the fact that 4 students killed and ate the Principal ever brought up again? I mean if Xander remembered eating the pig and being mean they should be in a bad mental condition when they remember killing and eating a human but I don't believe it's ever mentioned again. I'll take answers from any source of tv, comic, or interviews in the Buffyverse.
Answer: Snyder brings it up in The Puppet Show (1x09):

That's the kind of wooly-headed liberal thinking that leads to being eaten.

Buffy also asks Wood if he had heard about what happened to Flutie in Beneath You (7x02).
Other than that I don't think it comes up much at all. We certainly never see those students again.
Comment: Thanks it always seemed strange to me that the Pack's memories of killing and eating the principle was never mentioned again. Big missed opportunity for story there in my opinion. After all a lot of villains were recurring characters from the first season.


Android app for auto calls

Question: I need a free app for Android/IOS which allows user to make auto call. The app you can input your own audio, set phone number and time the calls would made.
Answer: Tasker does this and a lot more. It has Call action which allows you to Auto Dial a number. On newer Android versions or with custom phone call apps it could require help of AutoInput for the call to go through.
Unfortunately, audio part of it is (almost) impossible simply because Android doesn't allow apps to automatically talk to the other side - see e.g. this answer for more details. For obvious security reasons, as that could result in apps abusing permissions and advertising spam/scams whenever you make calls.
You could work around it by using 3rd party device next to the phone, e.g. some speaker, which is connected to a computer. Tasker could then contact the computer through various means (e.g. a HTTP request, IFTTT or an app like Join) and the computer would need to be programmed to play the sound through the speaker. Another option is 2nd phone.

Android app for auto calls


Relocating Floor Vent

Question: We are looking to place window bench over a floor register and relocate the register to the front of the bench. Currently the floor vent is a 4"x10" opening. We are considering using flexible ducting to attach to front of bench and use a 2"x12" wall vent cover to be integrated with the bench trim. Are there significant issues with reducing the ventilation area from 4"x10" to 2"x12"?
Answer: You're reducing the vent size by 40%. That will have a negative impact of the air flow in that room. It could also increase the sound level of the air leaving the smaller vent due to the increased pressure due to the smaller vent. I'd try to get a vent and duct closer to the original size.
Comment: One thing I have done in the past where I enclosed the area and had a "box" was to add multiple narrow vents on the bench but this depends on your plans but I would be cautious about reducing a vent close to a window, we put them there to off set the window.

Relocating Floor Vent


Why is my bloodstain sometimes short on runes?

Question: I haven't been able to discern a pattern, but sometimes when I retrieve my bloodstain after dying, it holds roughly 20% fewer runes than I dropped when I died. I've seen threads elsewhere on the internet that say nearby enemies will pick them up - and I have come across mobs (both hostile enemies and non-hostile creatures) with glowing gold eyes that drop far more runes than their non-glowing counterparts. However, there doesn't seem to be any relationship between these mobs and my mysteriously light bloodstains: I've come across them seemingly randomly in the wild (including two enemies in a tomb I'd never visited before), and I've thoroughly examined the surrounding environments when I've noticed my bloodstain is smaller than expected and come up with nothing - so if there is a relationship between the two, it's not an obvious (or geographic) one.
Comment: It's happened all over, inside and outside castles, in a number of different regions @Ꮢedacted
Comment: Just to know, are you by chance exploring a castle?
Comment: Golden eyed enemies are tougher versions of regular mobs that drop more souls upon defeat. They don't steal runes afaik. When you noticed your bloodstain had fewer runes than expected was it near a group of enemies?
Comment: @fez not always. I know it's happened during boss fights where there are no enemies between the nearest site of grace and the boss arena (the Four Belfries and the Chapel of Anticipation, for example)
Answer: I was noticing this too, particularly in Stormveil Castle when I was fighting dying to Godrick. Each time I collected the lost runes, I was noticing a decrease of what seemed to be about a third of what I initially had. It turns out this loss is due to an NPC you meet at the very beginning, when you first ventured into Stormveil Castle, when you met Gatekeeper Gostoc.
Gatekeeper Gostoc is the NPC you meet just next to the main gate to Stormveil Castle. He'll explain to you that you shouldn't take the main gate as it's too dangerous, and you should instead take the side passage next to him. Per the wiki:

Gostoc at first may seem to want to help the player, although in a suspicious manner. This is however just a facade. He will actually steal 30% of your runes every time you die in the castle, even if you enter it through the main gate.

So, while Gostoc lives, each time you die within the castle, you will permanently lose 30% of the souls you originally had. Gostoc's influence also appears to extend to a difficult-to-measure area around the castle, as his influence appears to be a bit larger than just Stormveil Castle. This influence appears to extend to somewhere between Stormhill Shack and Warmaster's Shack.
Once I learned that this was occurring due to him, I went and killed him, and I noticed that since then I wasn't losing 30% of my runes upon death.
You can find Gostoc stalking you in certain locations throughout the castle, which I suppose from a lore perspective explains how he's able to steal your runes each time you die: He's always watching. According to the wiki, he's also the reason you're locked in the room that contains the Rusty Key, as when the cinematic plays you can hear Gostoc cackle as the door slams shut.
Killing him will also give you Gostoc's Bell Bearing.
It is possible that there are other NPCs that will also siphon runes similar to how Gostoc does in other places throughout the game, but I haven't noticed this effect elsewhere yet.
Comment: @Kagemusha I cannot confirm or deny this statement, but some things I have read is that if you kill him *after* defeating Godrick he will *not* drop the runes
Comment: I just took another look at the map and the Chapel is clearly considered part of the castle
Comment: The only thing about this is I've seen it happen outside the castle - I know it happened at least once in the boss fight at the Chapel of Anticipation (from the Four Belfries, not at the beginning of the game) and once from fall damage in Stormhill (falling into the ravine below the giant).
Comment: @Wondercricket I can confirm that Gostoc does not drop runes when killed after defeating Godrick. Defeated Godrick the other day and killed Gostoc after talking to him. Received way to few souls compared to how often I died.
Comment: Also good to know from the wiki: When you kill him, "he will also drop all of the runes he stole from you if you died."
Comment: For some extra joy, kill Gostoc after beating Godrick (he'll be in the arena after you rest on a bonfire, doing something peculiar). You'll know why it'll be extra joyous once you do. Plus, I'm pretty sure you get some extra dialogue when doing it then.
Comment: Although....it occurs to met that the CoA boss _is_ Grafted, and there is another one in the castle. Lore-wise, it's plausible there's some connection between the grafted and the gatekeeper.
Comment: Gotcha! Glad that was the explanation then. Go kill Gostoc!
Comment: Several playthroughs and patches later, it might be worth adding - Gostoc's influence extends significantly outside that castle walls. I haven't done enough testing to determine _exactly_ what his coverage is, but it at least extends to somewhere between the Stormhill Shack and Warmaster's Shack.
Comment: Furthermore, completing Nepheli Loux/Kenneth Haight's questline adds an Ancient Dragon Smithing Stone to his shop inventory, which might be a reason to spare his life. Depending on how many runes you're losing to him, it might end up being a very expensive piece of upgrade material, but the ancient dragon stones are the only upgrade materials that are finite per playthrough


File transfer from PC to USB disk is very slow

Question: file transfer from PC to USB disk is very slow in my ubuntu 11.04(64bit) but the vice versa is not.transfer starts with like, for the transfer of 700MB file it starts with 30mb/s and towards the end it stops at 0s and stays put for like 3-4 mins to transfer the last bit. any help to solve this welcome
Answer: I assume your usb drive is formatted in fat32. Formatting your usb drive in ext3 or ntfs format will solve speed problem. But if you connect your ext3 formatted USB drive in another computer running windows, it will not work.
Answer: It is not a answer, and maybe is unrelated, but cheap USB Sticks are slow to write. When the OS is copying to the USB devices it starts fast because it is using main memory as a kind of write cache, but when it runs out of cache the speed decreases enormously.
Maybe, when its stop at 0s, the USB is still dumping all the cached data that it was not transfered yet.
Externals Hard Disk are usually faster and have a internal cache too, so this effect is not as appreciable as with usb memory.


Why does forgeContract receives a PubKeyHash?

Question: The forgeContract is responsible for minting NFT's and in the arguments we have a token name and amount, why do we have a public hash key for minting NFT?
Comment: Hello, I have been asked to review this question and have found that most people would not know which contract your on about. So can I ask you to link to the contract in the question. Thank you
Answer: The reason you have to provide a public key hash to mint an NFT is to verify that any future NFTs minted under the same policy are originating from the same private key.  The public key is a cryptographic identifier that only the developer/creator with access to the private key is able to reliably generate.  See Wikipedia's entry on Public/Asymmetric Key Cryptography for a good primer.
Deeper dive: "NFTs" are created using Cardano Native Scripts that declare: "this was minted by a specific secret key, [optionally before a specific expiration time], belonging to the NFT creator".  When you generate your policy ID for a Cardano NFT, that policy ID is actually hashed based off of the public key you are seeing in that minting script.  So long as the Cardano nodes agree that "this is the way we mint NFTs", no one will be able to create a new NFT under the creator's specific policy ID without the private key corresponding to that public key hash you are seeing.


What is a shadow ticket?

Question: I have been told that you can go online with Lufthansa and book a "shadow ticket" which makes a reservation for travel without payment and that you can renew this "shadow ticket" every 24 hours.  Has anyone heard of this or know who I could contact at Lufthansa to get this information?  Customer service had no idea.
Comment: Many airlines (and almost all the major carriers) offer 24 hour free cancellation. I use that option extensively when I see food fares that I want to think about for a bit before purchasing. https://thepointsguy.com/guide/airlines-24-hour-hold-cancellation-policies/
Answer: I never heard the term "shadow ticket", but some countries require a return (or onward) flight ticket as proof you are willing to leave the country within the allowed stay duration.
Right after you entered the country you can cancel the return flight and get the refund.
Answer: I have not heard of this (and I doubt Lufthansa would allow perpetually hold tickets for you at no cost).
What you can do - at Lufthansa and many other airlines - is to make a "price reservation". This "saves" the ticket price for you, and you have the option to buy it at a later date (at today's price) or not.
These options are valid for a limited time (48 hours for Lufthansa) and usually come with a small fee. For example: Lufthansa's reservation is free if you decide to buy the ticket, but if forfeit the option there is a 30 EUR "handling fee".
You can make a new reservation after your option expires, but only for the new, current price - not the original one from your first reservation.
As mentioned above, some airlines may also offer free cancellations during a limited time window - but you should check the terms and conditions beforehand.
A travel agent may or may not be able to hold a ticket for a limited time; but probably not for long.
Addendum:
On some airlines you can buy fully refundable tickets, but those are usually very expensive compared discounted fares. The same goes for "full flexible" tickets that can't be refunded but where you can change the travel date at will.
Still, it's sometimes possible to get good deals with those...
Comment: Aren't refundable or cancellable tickets sometimes available at (higher prices) directly from airlines?
Comment: Fully refundable are available on some airlines, though you obviously have to pay right away if you buy one. Also refundable "full-fare" tickets are often multiple times the price of the cheapest economy fare, so in many cases it makes no sense to use this to "reserve" a place.
Comment: Whether such a ticket "makes sense" to a particular traveler will depend on that traveler's circumstances, desires, and attitudes. Certainly in many cases such tickets will make little sense, but in others they may (forgive me) be just the ticket.

What is a shadow ticket?


travelling to Thailand as American/Belgian Dual citizen

Question: I am Belgian and American, born in California. I live in Belgium but my belgian passport has expired so I would like to know if I can go to Thailand only with my American passport and my belgian ID. My first plane goes from Brussels to Amsterdam and then another plane goes from Amsterdam to Bangkok. Do you have any advice ?
Answer: US nationals entering thailand with a valid US passport, and a valid return ticket, do not need visas for entering Thailand.
They also do not need a visa for Belgium as the EU has a visa waiver for US citizens.
So you should be fine to leave and return, provided your US passport is valid and provided you have a return ticket.
You will need a tourist visa for stays of > 30 days.

U.S. citizens carrying a tourist passport and in possession of an onward or return airline ticket do not require a visa to enter Thailand. The passport must have at least six months validity remaining to be allowed entry.  Upon entry, Thai immigration officials will place an immigration stamp in the passport permitting a 30-day stay in Thailand if arriving by air or land. This time limit may subsequently be extended for an additional 30 days by paying a 1,900 baht fee to the Thai Immigration Bureau office.  The headquarters of the Thai Immigration Bureau is located at Government Center Chaengwattana Building B, No. 120, Moo 3, Chaengwattana Road, Tungsonghong Sub-District, Laksi District, Bangkok 10210, 66-2-287-3101 through 66-2-287-3110.  For more information or additional Thai Immigration Bureau locations, please consult the Thai Immigration Bureau website.

https://th.usembassy.gov/u-s-citizen-services/thai-visas-americans/
Edited to add: You will need to show your Belgian ID when you exit NL, otherwise you will be questioned about your lack of a Schengen entry stamp. Your ID should be fine for this, as @CrazyDre addresses in their comment. And apparently you don't need to show your US passport on the European side, provided you have your Belgian ID.
Comment: If OP tries exiting the Netherlands with only their US passport, they'll be questioned as to the lack of a Schengen entry stamp. Hence they should show the Belgian ID (it's all they need to exit the Netherlands)
Comment: It's your answer - add whatever you desire. OP's not obliged to Show the US passport at European border control at all though, just saying - only the Belgian ID
Comment: That's a good point. I'll add it to my answer, if you don't mind.
Comment: I didn't realise a passport wasn't required on the European side. That's useful information!
Answer: Show the following documents:

At bag drop in Brussels (if applicable): US passport
At the gate in Brussels (if asked for ID): either document
At border control in Amsterdam: Belgian ID
At the gate in Amsterdam: US Passport
At border control in Bangkok: US passport

On the way back:

At bag drop in Bangkok (if applicable): either document
At the gate in Bangkok: either document
At border control on arrival in Europe: Belgian ID

So yes, this trip is 100% fine


Can't access multiple records being returned by sql via ADODB.Recordset object

Question: When I execut the sql direct it returns 4 records. when I execute the oraCommand.Execute the oraResults object shows only 1 record returned it should have a count of 4.
Hence I can get the value and name for the single record. Question is how do I get the other 3 records? I have tried set oraResults=oraResults.NextRecordSet() and I get error saying not supported!
Any help will appreciated.
This is the snippet of the code:
set oraCommand = CreateObject("ADODB.Command")
'set connection and sql statement
set oraCommand.ActiveConnection = oraConnection
oraCommand.CommandText =oraSQLStatement
oraCommand.CommandType = 1 ' commandText
oraCommand.Prepared = True

set oraResults = CreateObject("ADODB.Recordset")
'run the sql
set oraResults = oraCommand.Execute
oraResults.Fields(0).Name    - Name from first record is returned
oraResults.Fields(0)>Value   - Value from first record is returned

Answer: Try something like this: loop through the oraResults recordset and read the records:
Do until oraResults.EOF
   Response.Write oraResults("firstFieldName")
   Response.Write oraResults("secondFieldName")
   oraResults.MoveNext
Loop

Here's a link that might help.


Notes.app: Notes from iCloud show title but bodies are blank!

Question: I have been using notes.app for a while, especially for its ability to use iCloud to sync. Everything has seemed fine, though it seems like some of my older notes' bodies are showing up blank.
I suspect that this is merely a retrieval/format issue, but I am also concerned that by looking at a note triggers an automatic save, which in turn does in fact replace iCloud's copy of that note with the now-blank version. I have stopped looking at older notes pending a solution in case looking is destructive.
How do I download an archive of my iCloud notes that I may preserve and peruse at my leisure?
Notes have been left from Mavericks, Yosemite, and iPhone 5s with iOS 7.1.2. I am currently retrieving them using Yosemite.
Answer: Welcome to my world.
I had same problem and ended up killing the Notes in iCould.
Before that I moved my precious notes to "on my mac" at least the ones that were still there.
No more iCloud stealing my notes.


Example of "The eigenvalues of data covariance matrix, $\Phi^T\Phi$ measure the curvature of the likelihood function."

Question: I am reading PRML, Chapter 3.5.3, screen shot attached. I can understand the derivation and maths but hard to understand the meaning of "The eigenvalues of data co-variance, $\Phi^T\Phi$ matrix measure the curvature of the likelihood function.". Can you please help me understand by providing an example which can give me the intuitive meaning of the following statement. "The eigenvalues of data co-variance matrix, $\Phi^T\Phi$ measure the curvature of the likelihood function." __________________________________________________________
Comment: He doesn't actually say the quote that is being put in quotation marks. He says that the eigenvalues of $\beta \Phi^T \Phi$ measure the curvature of the likelihood function. This is a result of the fact that $\beta \Phi^T \Phi$ is the Hessian of the likelihood function (in this context), and the eigenvalues of the Hessian of a smooth function $f$ tell you something about the "curvature" or shape of the graph of $f$. This can be understood by thinking about the second-order Taylor series approximation of $f$.
Comment: Thanks but thats what my question is; $\Phi^T\Phi$ is the measure of data scatter (in data space), then how it playing a role in deciding the likelihood function (in parameter space)
Comment: I would start by looking at Fig 3.15 and equation 3.87 :)
Comment: What I can see, they are some what orthogonal. But is it always true?
Answer: The marginal likelihood here is
$$ p(t|\alpha,\beta) = \int p(t|w,\beta) p(w|\alpha) \text{d}w = c\int \exp(-E(w))\, \text{d}w $$
So the energy or error $E(w)$ basically determines the likelihood, where
\begin{align}
E(w) &= \frac{\beta}{2}||t - \Phi w||^2 + \frac{\alpha}{2} w^Tw \\
&= E(m_N) + \frac{1}{2}(w-m_N)^TA(w-m_N)
\end{align}
where $\Phi$ is the design matrix and $$ A = \alpha I + \beta \Phi^T\Phi = \mathcal{H}[E(w)] = \nabla\nabla E(w) $$ is the Hessian of the error.
Notice that the eigenvalues $\lambda_A$ of $A$ are real and positive since it is symmetric positive definite. Notice also that the eigenvalues of $A$ are directly related to those ($\lambda$) of $\Phi^T\Phi$ by a constant scale and shift:
$$ Av = \lambda_Av\;\implies\; \Phi^T\Phi v = \frac{1}{\beta}(\lambda_A - \alpha)v = \lambda v $$
In other words, $\Phi^T\Phi$ controls the eigenvalues of the Hessian.
Informally speaking, we view the second derivative (in this case, Hessian) as the curvature of the function. In this case, since $A$ is the Hessian of the error $E(w)$, and the error determines the likelihood, we can reasonably say that $\Phi^T\Phi$ determines the curvature of the likelihood through $A$.
But this can be made more precise.
Consider the eigendecomposition of $\Phi^T\Phi = U\Lambda U^T$, where $U$ is orthogonal.
Working in the orthonormal basis (rotation of weight space) defined by $U=(u_1,\ldots,u_M)$,
we can consider how $E(w)$ looks.
Notice that a level curve of the error in weight space forms an ellipse, with the width of the ellipse in each direction (aligned to some $u_i$) controlled by (proportional to) $\lambda_i$. A wide ellipse (small eigenvalue for that axis) means that a large range of the parameter space spanned by that axis $u$ have very little effect on the error. In other words, the error surface is not very curved (along that axis).
Essentially, smaller eigenvalues mean more contour elongation, which means less curvature (smaller Hessian).
He says:

a smaller curvature corresponds to a greater elongation of the contours of the likelihood function

The relation to the covariance of the (embedded) data somewhat makes sense.
Recall that the posterior here is written:
\begin{align*}
p(w|t) &= \mathcal{N}(w|m_N,S_N) \\
m_N &= \beta S_N \Phi^T t \\
S_N^{-1} &= \alpha I + \beta \Phi^T\Phi = A
\end{align*}
So in this case, the covariance-like quantity $\Phi^T\Phi$ inversely controls the posterior covariance of the weights. As the eigenvalues $\lambda$ get larger, the covariance of the posterior over weights gets smaller. This means that such parameters are tightly constrained to their mean (as straying too far will lead to a huge increase in error).
Why?! Suppose all your data is clustered around one point. The eigenvalues (data covariance) will then be small. But the posterior will be under constrained then! I.e., there are many parameter values that could let us explain that little cluster. We want many points, spread all over the space, in order to nail down a good function, with low posterior covariance.
So, greater (embedded) data covariance means larger eigenvalues, which means (1) smaller posterior covariance and (2) less elongation, which means larger error surface curvature (i.e., larger Hessian eigenvalues).
Comment: Thank you for such a great insight. I am still trying to understand it thoroughly :) Meanwhile I still have few doubts Q1. Can I always say that Error function, E(w) is -log likelihood function? which makes the error function a mirror image of -log likelihood function (this is what brings the inverse relation between Hessian and Covariane); Or it the case with generalized linear models only.
Comment: @ArunChauhan Glad to help. At least in ML, it is often fine to call the error a negative log-likelihood. The VAE literature for instance does this.


Is this mold in the crawlspace? Flip or flop?

Question: We are looking at putting an offer in on this house but are hesitant because it was recently flipped.  New everything cosmetic, looks like quality work. They also installed a new roof, HVAC +duct work, vapor barrier, and even a sump pump. This makes me wonder if there was a lot of moisture in the crawlspace previously and mold.  This is the main concern.  The house smells extremely strong of new paint, so it's hard to detect anything that way. But I did crawl under the house and snapped these images of subfloor beams and foundation blocks in the crawlspace. It's dry down there right now but I'm assuming there may be some residual water damage still. Like maybe they fixed the root cause with the gutters outside and the sump pump but I'm worried about residual mold.  Are the black dots insect droppings or something else? Also I noticed some white stuff that looks like mold, possibly where the master bathroom is above (we noticed a soft spot in the bathroom floor in front of shower) What do you think? I'm also including a picture of orange dots I saw in the coat closet upstairs which seemed strange since it's all freshly painted.. Any input will be so helpful as were first-time home buyers! Thanks!
Comment: The top pictures with the large areas look more like stains.  The bottom pictures with the small spots are possible mold or just stains also.  Can only tell if it is mold by having it tested and when tested they will you the type also, if dangerous or just icky looking.  If it not though out the house and just in a few spots, and the build quality of the house is very good, then it should not be the only reason of not buying, but might let you knock some of the price down.
Comment: Thank you for your input! yes I think I would definitely want to get those things tested and addressed before we closed on it.  The structure seemed around elsewhere , just those areas looked concerning.
Comment: Structure, electrical and plumbing are usually the most important.  If they are all good, a little mold is usually very easy to take care of, unless it is one of the very few types out of thousands that are very bad.  Testing is the only way to to tell.
Comment: The black spots look like mold.  This is not necessarily a deal killer, as in exposed places like this (floor joists in a crawl space) the mold is relatively easy (and cheap, compared to the cost of the house) to treat.
Answer: As mentioned by others they look like water stains. But the flippers may have fixed the problem. You should get it tested for moisture content. Buying a house is a big investment. I always hire an expert to check it out professionally.  They know the places likely to leak etc.
If you are borrowing money, it can be assurance for the bank.
If you want to do a preliminary test yourself, you can buy moisture testers online. Allowable moisture content should be in your local building code, it is here in NZ.
Answer: The black spots look like mold.  This is not necessarily a deal killer, as in exposed places like this (floor joists in a crawl space) the mold is relatively easy (and cheap, compared to the cost of the house) to treat.
And no, just wiping it down with a bleach solution will not kill the mold.  The mold actually sends little tentacles/dendrites(?) into the wood.  These are not affected by the bleach, and so the mold can grow right back again.
But, I would have them (the sellers) remove all of the fiberglass insulation in the crawl space.  That's a disaster in the making, because if it ever gets wet (which it could, all it takes is a high dew point), it will never completely dry out.