Why doesn't rain fall down in streams (as opposed to drops)

Question: Why is it that raindrops don't collide and 'stick together' on their descent to Earth, arriving in streams rather than separate drops?
Comment: If you have access to a bridge or tall rooftop where it's safe to do so, try pouring a pitcher of water in a stream from a few hundred feet up.  Watch what happens to the stream.
Comment: Is it possible that the friction with the air prevent this?
Comment: Imagine dripping with sweat and you'll see why rain won't fall in streams. ;)
Answer: Have a look at the Wikipedia article on raindrop formation. You'll also find lots of articles on raindrop formation and growth by Googling raindrop formation or something like that.
Raindrops do coalesce, but they also fragment, and the eventual size is a balance of the two processes. The fragmentation occurs because of the forces from turbulent air flow. Turbulence can cause droplets to collide, in which case they may coalesce, however it can also break apart large droplets.
Incidentally, a stream of water is unstable at low flow rates because of the Plateau-Rayleigh instability so it's very unlikely you could get a continuous stream of rain even under ideal atmospheric conditions. The closest you would get is a series of droplets in a line. However in the real world even the slightest turbulence would scatter the droplets and lead to the random distribution of droplets that we see.
Comment: Having read Dario's answer, he makes a good point that I omitted. Raindrop growth (and fragmentation) happens inside clouds where the airflow is turbulent. Once raindrops have left the cloud the air flow is far less turbulent (well, as long as it isn't a hurricane I suppose) and no drop collisions occur, so the drop size doesn't change (much).
Comment: Then I think it is odd that you haven't upvoted Dario's answer (at the time of writing this, Dario's answer had zero votes).
Comment: Wow, you said what I was trying to say and more in lot less words! +1
Comment: @JohnRennie - A good deal of fragmentation happens shortly after a big fat drop of rain leaves the cloud base, and this happens even in a nice laminar flow. Very huge rain drops can form inside water-laden clouds where the rapid growth rate can easily overcome fragmentation. There is essentially no growth once a big fat raindrop leaves the cloud base, but the instabilities that lead to fragmentation are still present.
Answer: Water starts to fall from the clouds when the drop size reaches a critical point which depends on a lot of factors such as the strength of upward currents, but also air density and gravity acceleration. When the drops leave the cloud no more collisions take place and their size is fixed.
To create a water stream we need to concentrate water from a large area to a local point. This is done by each roof and gutter, but could this happen in the atmosphere?
Let's think about this: air currents will need to point from different directions to a local spot bringing there water from a large volume. This would require air to compress approaching that spot, which would divert this current. So, even from an intuitive point of view, this is not likely to happen.
Comment: Regarding the first paragraph: Droplet size is not fixed when raindrops leave the cloud base. That's when a good deal of the fragmentation that splits large raindrops into many occurs, particularly so in heavy rains. The drops leaving the cloud base of a heavy rain can be rather large. Large raindrops are unstable. The flatten and then form a parachute-like structure that quickly quickly breaks apart.
Comment: @DavidHammen that is the point of John's answer, but I think that in the context of my answer is just a useless complication.
Comment: Surely drops are not all identically sized and thus fall at different velocities and continue to collide - so there is both coalescing, and evaporation, and disintegration (as David Hammen pointed out) - so drops will continue to change size on their way from the cloud to the earth.
Answer: First of all streamline is a flow in which every drop at same position has same velocity, this is true for rain as long as wind is neglected!
What you seem to be asking is that why there is significant time lapse between individual drops of rain as opposed to a shower and/or why the flow is like a shower and not that of a tap.
Well the flow of a tap is based on water leaving the container through one opening, as the water particles crowd together at the opening they come out together. In a shower there are multiple apertures for the water to leave and hence the separate streamlines do not always coalesce unless the shower is curved to make them coalesce.
A cloud acts like both in different times,  mostly it behaves like a shower and has multiple openings sending separate streams of water, but sometimes it becomes one giant aperture (cloud burst) and all the water it contains comes down like that of a tap/waterfall resulting in flash floods at many times.
As to the othet part, in a normal shower the distance between drops is very less because the travel very less. Lets say the shower is at a height of 5m and a cloud is at a height of 500m, if droplets come one every second from both then lets watch 2 consecutive drops.
For the shower, when first drop hits the floor, the other drop is still in the shower but only at a distance of 5m, as rate increases the distance becomes negligible.
But for a cloud,  when first drop hits the ground, the next drop is 95m above the ground,  even after rate becomes equivalent to that of a normal shower there is noticeable difference and hence you observe drops than streams!


Replace A T5 Fluorescent to A T8 LED

Question: I currently have a T5 Fluorescent Fixture which one socket broke. I got a great deal on LED Bulbs which are a direct replacement to T8 Fluorescent bulbs. Would I be able to reoutfit the fixture with T8 Sockets, or would I need to change the ballasts too?
Answer: The T5 fixtures have several differences the first is they are shorter than a T8 so no you can't use the T8 lamps.
2nd would be,
The tombstones are smaller in a T5 and not compatible with T8 or T12.
Last the T5 fixtures and lamps I use require 54w ballasts where the T8 only require 30-40w this may be a problem for both the ballast and the new led lamp if you could make it fit.
A new fixture is the only real path forward for T8 but T5 tombstones are inexpensive if you want to save the fixture.
Comment: Typically an LED replacement for fluorescent is going to be no-ballast and directly wired to 110v, which means the reference to ballast power capacity isn't a factor. Certainly length differences would make it difficult for a swap.
Comment: Not true Fred_dot_u. There are more retrofits available that use the ballasts because of U.L. listing problems with 120v. If those that are out there many are single end powered because of U.L. I don't like those and won't use them. I have seen two many tombstones break, having 120 on each end makes sense to me but the mfg's that were shipping these for direct wire pulled them because of U.L. It makes no sense to me to use a ballast then transform the power again because some efficiency is lost but that is How the majority of retrofit LED lamps are designed.
Comment: Thanks for the clarification. It's not unlikely that my area resources have limited their stock to the 110v versions only. Curiously, two of my purchases stretched over a period of time resulted in a one-end model and a two-end model, both 110v without ballast. Clearly no real standard to make life easier for DIYers.
Answer: Maybe
T5 tubes are actually shorter than T12 tubes by about 2 inches.
In many native-built T5 fixtures, the fixture is built for that size, and that is that.  You can tell these because it would be physically impossible to fit an actually-47-3/4" tube.
Some fixtures are actually engineered for T12/T8 and use T5 extension tombstones to close the 1" gap on each end.   Those, you can just swap in T8/12 tombstones.
Other fixtures are notched in a way where they can fit either type of tombstone.
You will have to see what kind of fixture you do have.
Beware of "great deals"
Prices are dropping very rapidly and for instance I could get good Sylvania units for $6 each, last I checked.
These are all engineered products that take some careful match-up to work correctly, even if they can be made to fit.  For instance, direct-wire tubes will work well enough by modifying the fixture.  However plug-n-play tubes require the correct type of ballast.  A T5 ballast may not be a usable voltage or current.  Those made for instant-start ballasts will never work with a T5 ballast, as those are by definition rapid or programmed start

Replace A T5 Fluorescent to A T8 LED


Is the fingering the same for Hanon exercises when you play in a different key?

Question: For example, the fingering for Hanon exercise #1 in C is 1-2-3-4-5-4-3-2. Is the same fingering used for the other 11 keys? If so, does the rule hold for all Hanon exercises?
Answer: Hanon exercises are designed to be played on white keys, and it was not Hanon's intention they be transposed. However, transposing them can be an excellent exercise, in which case it's up to you how to finger them. My personal preference is to use the same fingering in all keys because of the variety of "problems" it presents as the configuration of black and white keys changes. However, it can also be quite useful to create your own fingerings as a way to practice different finger combinations or to find creative solutions to awkward key combinations.
Answer: I'll opine that you can play most with the same fingering but obviously elbow, rotations, in/out, up, down and shifting movements will change drastically.
I do not condone the use of Hanon for technique.  Technique comes from moving properly and obeying the laws of physics, not a book.  If you can't do something at the piano, you need an adjustment to how you move, not hours of practicing incorrectly. And, just because you practice slowly does not mean you are practicing properly. Slow wrong is still wrong.
That said, snippets from the Hanon exercises can make wonderful little jazz fills and leads.  So much time is wasted on Hanon.  Use it as a reference.  The instructions are greatly flawed, too.  He advocates isolating a finger and lifting it high.  While it is true that every motion must have an equal and opposite motion, there are more efficient ways to achieve that without isolating a finger which immediately creates strain as two muscles pull on one bone. The book lacks admonishment NOT to abduct and those exercises can very easily hard wire improper movement into your brain.  VERY. If your teacher doesn't know what a pronator is, abductor, long flexor, ulnar deviation or the laws of physics, your teacher can hurt you.


Co-Owned Property Rights

Question: I'm a co-owner of some commercial property in Louisiana.  One of the co-owners wants to rent out part of the property; however, I don't agree with the terms.  Apparently he has already granted access to someone to start setting up his business in that part of the property.  I never signed any kind of contract to allow this.  Can I do anything to stop this from happening?  As a co-owner, am I allowed to force the renter out of the building?
Comment: I would see a lawyer about getting a court order to "freeze" the transaction. You may or may not be able to "halt" it, but you may get the terms adjusted in your favor, or at least to a level accepted by a majority.
Comment: I would venture a guess in any jurisdiction but Louisiana where I don't trust my common law knowledge about co-ownership to apply.
Answer: Details may vary by jurisdiction but in general, co-owners of a property are common law partners.
As such, anything done by one of them is legally the same as if it were done by all of them. Assuming the lease/rental is other is otherwise binding, the fact that only one owner entered it does not make it non-binding. Your chances of ending or varying it without the tenant's agreement are virtually nil.
You may have a cause of action against the owner: partners have a fiduciary duty to one another and if they entered the contract knowing that you didn't agree with it they may have breached that duty. Depending on how such things have been managed in the past, they may be liable even if they didn't know your feelings if they failed to make reasonable efforts to find out.
Comment: FWIW, that would not describe co-tenancy in real estate in most U.S. jurisdictions. Co-ownership is not partnership in most U.S. states under the Uniform Partnership Act.

Co-Owned Property Rights


USB power isolation

Question: Here is the USB to Serial portion of Sparkfun's Stepoko board. Can anyone help me understand why the USB power is isolated from the +5V which is a separate onboard supply powered by an external supply? Nothing except the FT232 is powered by the USB. Hence would it be ok to just leave the F_SMALL fuse and D3 schottky diode unpopulated? Why do you explicitly need to isolate the two supplies?
Answer: If Vcc is higher than +5v + the forward drop of the diode the board will be powered from USB. If +5v is higher than Vcc - the forward drop of the diode then the board will be powered by the on-board supply. By removing the diode and fuse you remove the ability to power the board by the USB port.
You must isolate the two power sources because a USB device is not allowed to drive power onto the USB power lines. Only a host or hub is allowed to do that. The diode prevents the board power from going out through the USB port.
Comment: Thanks. `By removing the diode and fuse you remove the ability to power the board by the USB port` - I do not want this anyway. The whole board is way too much to be powered just through the USB port. The USB port powers only the FT232RL.

USB power isolation


Determine a polynomium $q \in P_3(\mathbb{R})$ where the coordinat vector $[q]_v$ is equal to v where v is a vector

Question: I have to determine a polynomium $q \in P_3(\mathbb{R})$ where the coordinat vector $[q]_v$ is equal to v where v is a vector given by
$$
v = \begin{pmatrix} \alpha \beta \\ -\alpha -\beta \\ 1 \end{pmatrix}
$$
My books has a note saying that the coordinat vector $[q]_v$ is given by the vector
$$
\begin{pmatrix} a_1 \\ a_2 \\ ... \\ a_n \end{pmatrix} \in P_3(\mathbb{R})
$$
where
$$
v = a_1 \cdot q_1 + a_2 \cdot q_2 + a_3 \cdot q_3
$$
where $Q = (q_1,q_2,q_3)$ is a basis given by $Q = (1,X,X^2)$. I am not really sure that I am explaining this correct so I have this is correct so far.
In regards I have then said that the polynomium q  will be
$$
q = \frac{1}{X^2} + \frac{-\alpha -\beta}{X} + \alpha \beta
$$
Is this correct? Or am I doing it completely wrong?
Thanks in advance.
Answer: It is not correct. We have
$$q=\alpha \beta q_1-(\alpha + \beta)q_2+q_3,$$
hence
$$q(X)=\alpha \beta -(\alpha + \beta) X+X^2.$$


EMC testing of polarity detecting circuit

Question: I am in the process of building a prototype and need advice on best way to ensure passing EMC testing the first time.  I am what most would consider a hobbyist and I am doing this project on a shoestring and I really can't afford to go through the testing process more than once. It seems from what I have been reading that EMI seems to be more of an issue at the kHz to MHz range. My device is very simple, consisting of 2 identical, polarity checking circuits in a plastic enclosure.  These circuits consist mainly of diodes but I have incorporated a LED that flashes at 2 Hz. There is also a 4 kHz piezo buzzer hooked up in parallel so that the "alarm" is in sync with the flashing. I don't imagine that the 2 Hz flashing would be an issue, but I am concerned about the 4 kHz buzzer. This is a simple DC circuit. Any advice offered would be greatly appreciated.
Comment: @JasonHan Well, that's an approach I suppose. Not one I'd take. But it could work out, depending upon circumstances. Personally, I'd recommend that the OP just disclose here the details they are working on and stop worrying that someone might steal the idea. If it does get stolen, ... oh, well. But the OP learns. If creative enough, they will come back into the fray with something more/better and will be smarter for the earlier effort. (I think ***good*** ideas are a dime-a-dozen; there are many more good ideas than sweat and tears to deliver them. Just work and let the rest flow out of that.)
Comment: Why do you need to throw good money away on a hobby? When we do EMC, it is mainly to profit and the money can be earn back.
Comment: @JasonHan Reading between the lines, this is a hobbyist who is now going out on a limb in order to create a product that would be sold for a profit. And that there is a recognized "threshold" that is crossed in whatever country they are in. If just a hobbyist interest only, I also suspect more details might have been advanced. (But I think the OP is being intentionally circumspect.)
Comment: Hi jonk. I would still highly recommend OP not to continue his EMC test. However it's better for him to join a company which do send their products for EMC, during a free time he could just throw his product in and do a quick 5 min scan.
Answer: It's the same basic set of rules for most products:

Ground plane, ground plane, ground plane. If it's a two layer board, make sure that as much routing as possible is done on the component side of the PCB. Keep tracks on the other side (on which you'll have your ground plane) as short as possible. Then fill the ground plane once all is routed.
Keep tracks as short and thick as possible, especially high frequency and power tracks - although yours are very low frequency. Thicker tracks mean lower resistance and inductance. Placement of components helps massively with this, spend lots of time getting your components in positions to make tracking as easy as possible.
Good decoupling for all power pins. Route power into decouplers and then out into the supply pin. One decoupler for every power pin. Send short, thick stubs to vias for connection to ground planes.
Follow advice in datasheets for specific components; there are often good notes for things like switching regulators about layout for example.
Keep your crystal as close as possible to the micro. Keep tracks short.
If you have connections to the outside world, think about protection as well as filtering. It's not just emissions you need to think about, but also immunity.  It's impossible to know what you'd need for this as there are so few details.
Ground plane, ground plane ground plane. This is so important it's worth putting twice to reinforce the point. As big and as unbroken as possible.

There are other rules for more specialised boards such as split grounds, but I'm assuming you only have one ground?
No idea where in the world you are, but in the UK, the cost of testing can vary a lot from place to place. Plus quality of advice varies greatly.
Comment: Can't believe someone down voted this!


Any python script to convert a geoPDF to a KML embedded with a jpg link?

Question: I have many geoPDFs. I want to turn them into KMZ or KML+JPEG using a python script.
Any suggestions?
SEE CODE BELOW
Answer: This code below may help guide some one wanting to convert many geoPDFs to KML-Superoverlay which can then be incorporated as web map overlays using Google Maps API or Google Earth API...
<code>import shlex
import subprocess
from subprocess import Popen, PIPE
import os

def step1_translate( input_file ):
    out = input_file + ".vrt"
    translate_command = "gdal_translate -of VRT %s %s" % (input_file,out)
    translate_args = shlex.split( translate_command )
    p1 = subprocess.Popen( translate_args) # translate
    print p1

def step2_warp( input_file):
    gdalwarp_command = "gdalwarp -of VRT -t_srs EPSG:4326 %s %s" % (output_file,output_file2)
    gdalwarp_args = shlex.split( gdalwarp_command )
    p2 = subprocess.Popen( gdalwarp_args   , stdin=p1.stdout ) #gdalwarp

def step3_tile( input_file, output_file, output_file2 ):
    gdal2tiles_command = "/home/boris/gdal/swig/python/scripts/gdal2tiles.py -p geodetic -k %s" % output_file2
    gdal2tiles_args = shlex.split( gdal2tiles_command )
    p3 = subprocess.Popen( gdal2tiles_args , stdin=p2.stdout) #gdal2tiles
</code>
Answer: I don't have a script available, but you could probably write one using the GDAL library. GDAL has input support for geoPDF and output support for JPEG. You would need OGR for the KML output (http://www.gdal.org/ogr/ogr_formats.html).


Android development, Source file organization/notation best practices?

Question: Android lists coding standards but does not seem to go into how source (Activity's, etc) files should be organized. As my project grows im wondering how I should be breaking up the classes or if I just just leave a mess of 20 files in the src folder. It does not seem like there is any sort of notation (like Hungarian) nor an way to id whats an activity, or other helper class. Are there any docs on these sorts of best practices?
Answer: If you look at the apps that come with the android source, like gallery, launcher ect. you will notice that those guys pretty much kept everything in one folder...
Quite a mess if you ask me.
I usually have a folder "widget" for all my views, one for activities, one for providers one for utilities whatever.
Browsing throug open source projects alot, i dont think there is any common standart for doing this. Use what works best for you.
Comment: yea thats what I thought was odd, I looked at the sample projects but most only required a few files. I guess I will use my normal folder for org.
Answer: We already had a little discussion about it here:
Android separate packages
Besides that, I think following the (pure) Java coding standards is a good practice.
Answer: Do you really have everything in your base src folder?  A good start would be to put your classes into packages.  After that, you could create a "util" package for your helper classes and name them as such (ie. MainActivityUitl.java).


Copying game files from friend who also owns the game Steam?

Question: My friend and I recently purchased Rainbow Six: Siege on Steam. However I have a very limited data plan so I can't download. Can I copy the game contents from his PC to mine?
Answer: Yes you can.
The only check Steam is doing, is that you have Steam running with a logged account possessing the game when you launch a steam game.
So you can totally take the game on the computer of your friend where he installed it and copy it into your Steam games directory.
Comment: @Saad No problem. I have a slow Internet connection like you so I always try to take large games on the computers of friends to not have to wait the entire night with my PC downloading. ;)
Comment: @Saad And if the answer is good enough for you, don't forget to accept it so that we know your problem is resolved.


What to use for performing operations on multiple records at once, Apex REST class or Bulk API?

Question: I need to insert/update/delete a variable number of records at a time from a webapp (so from javascript), are there reasons to choose the Salesforce Bulk API over writing a custom Apex REST class to do this or vice versa?
Answer: If the number of records is relatively small (10s or 100s) then a custom Apex REST method will be much simpler than using the Bulk API. The Bulk API is intended for asynchronous processing of thousands of records.
Answer: If you need to update a LOT of records (10's of thousands) the BULK API is the best method to do so.
For updates < 5-10k, the best method is the SObject Composite Collections that were added in v42.  There are two major benefits over the existing composite tree & batch endpoints.
1: You can update up to 200 records at a time
2: The updates take place in a single execution context on salesforce.  The other composite record create a context PER RECORD, which make it run incredibly slow for big updates.
Comment: @RohitKunal sure it does... I'm using it in a project for just that purpose. See https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/resources_composite_sobjects_collections_delete.htm
Comment: Please keep in mind that it doesn't work for DELETE operation
Comment: whoah, thanks for that! Can't believe I missed it!
Answer: Bulk API is an implementation or REST API. So whether you use Bulk API or simply the REST based API depends on your client application ( your webapp ).
The advantage of Bulk API is to dump a large batch of records to Salesforce and let it process it. This will reduce the processing and iterations you would need to do in your app.
If you use standard REST API, you would need to loop through and submit records one by one.
Comment: Question asks about custom Apex REST class, not standard REST API.


Symlinking a vagrant shared folder with puppet

Question: I'm needing to recreate a setup on an old server with vagrant where we served sites within the home directory. Its not possible to set a shared folder to /home in vagrant as this will remove the vagrant user. I therefore would like to create a shared folder that is actually a symlink to the home directory.
If I create a shared directory like this in my Vagrantfile:
config.vm.share_folder "v-www", "/webroot", "/Users/me/sites/vagrant"

and then try and create a symlink with puppet overwriting this directory like this:
class misc {
  file { '/webroot':
   ensure => 'link',
   target => '/home',
   force => true,
  }
}

It throws an error:

Error: Could not remove existing file
Error: /Stage[main]/Misc/File[/webroot]/ensure: change from directory
  to link failed: Could not remove existing file

When I log into the box and attempt this manually this also fails as i'm not actually able to remove the webroot - I assume this is because its created as some kind nfs share or something like that.
Any ideas how I can get around this?
Answer: Try adding a replace:
class misc {
  file { '/webroot':
   ensure  => 'link',
   target  => '/home',
   force   => true,
   replace => true,
  }
}


What is the difference between relative stability and absolute stability

Question: Is there any difference between relative stability and absolute stability?
Do all the control system analysis techniques (Root locus, Routh-Hurwitz, Nyquist, Bode plot) are able to find both stabilities?
Answer: Relative stability and absolute stability are not two different "kinds" of stability. Absolute stability is a binary thing, is the system stable or not?
Relative stability will tell you, if your system is stable, by how much can you increase the gain of the system or the phase lag of the system before it becomes unstable?
So any technique that tell you whether a system is stable or not could also be used to calculate these two relative stability metrics.
If for instance you have a system which becomes unstable if the gain is 100 but you currently have a gain of 20 then your gain margin is simply 100/20 = 5 = 14dB
If you plot the bode diagram of a system and you note that when the gain is 0dB you have -150 degrees of phase then you can see that you have -30 degrees of space between where you are and the border between stable and unstable, that means you have a phase margin of 30 degrees.
Answer: (RELATIVE STABILITY)it is measure of how fast the transient dies out in the system .relative stability is related to settling time. a system having poles away from the left half of imaginary axis is considered to be relatively  more stable compared to a system having poles closed to imaginary axis.
(ABSOLUTE STABILITY)If the system returns to it equilibrium state after the inputs given to the system are removed .


How to Get Web Access Panel After Installing NextCloud Server from Snap?

Question: I'm following a few tutorials to set up my laptop as a Nextcloud server and have just installed NextCloud from a snap package and verified that it is installed properly.
I'm looking to get to the web interface to create an admin account and proceed with the tutorial, but I can't seem to find the https://IP_OF_SERVER/nextcloud page. I've tried replacing the IP_OF_SERVER with some of the ip addresses from ip a, but this doesn't seem to be effective, and worse, this is a local ip address.
How would I access this from my phone when I'm out and not on the network?
How do I get the proper IP address to enter into the browser to create an account, and will this be visible to an android phone not on the Network?
I'm running Kubuntu 18.04.01 LTS.
Answer: check if localhost is listed in the trusted domains in config.php. If not try adding it. For me trying localhost.local worked (like server.local).


Hardware/software serial for HC-05

Question: can anyone please tell me the whole difference between hardware and software serial for the HC-05.
I read UART,USB cable, serial and I was like really confused
so what is the difference and advantages between both?
thank you...
Answer: Hardware serial uses pins 0/1 on the Uno. You can't change those pins. Those pins are also the pins that are used to communicate with your computer. You can use hardware serial on those pins to communicate with the HC-05 only if you don't want to communicate with your computer.
SoftwareSerial can be used on any pins so can be used at the same time as the hardware serial for communicating with your computer. However SoftwareSerial is somewhat limited in what it can do.
Bigger boards (such as the Mega) usually have more than one hardware serial port. These are connected to the TX1/RX1, TX2/RX2 etc pins. These are the preferred method of connecting to external serial devices since they work more reliably that SoftwareSerial and concurrently with the computer's USB connection.
Answer:
Hardware vs Software Serial: Most microcontrollers/Arduinos have at least 1 hardware Serial interface. That means, that for this Serial interface the actual communication protocol (the transmission and receiving of the actual data) is implemented in dedicated hardware inside the microcontroller (which also means there are fixed pins, where you can connect to them on the board). That way you don't need code for doing the complex communication protocol. Instead the main CPU is only involved to handle the received and to-be-transmitted data, which need to be placed in a buffer register. The dedicated hardware then automatically sends and received the data.
As the number of hardware Serial interfaces is limited and fixed for the Arduino board/microcontroller, it happens, that you need more Serial interfaces, than you have in hardware on your board/in your microcontroller. Then you can use SoftwareSerial. That is a library, which handles the complete communication protocol in software, by directly setting and reading the electrical pin states according to the protocol. The advantage is, that you can use this on any digital pins for such an interface. Disadvantage is, that doing such things in software is complex. You can only listen on 1 SoftwareSerial interface at a time and the baudrate is limited (depending on the actual used microcontroller, e.g. it's frequency).
UART vs Serial: UART is the technical term for the used communication interface. Serial is an Arduino term, which is not used that way in other contexts. The real interface type is UART and the Arduino framework just names that Serial to make it simpler.
Connecting over USB cable or pins: Let's take the Arduino Uno as example. It has 1 hardware serial interface. This interface is connected to the pins 0 and 1 (RX and TX), but also internally to an extra chip. That chip handles the USB connection and behaves as a USB-Serial bridge. When communicating with the Serial Monitor in the Arduino IDE, you are actually using this USB-Serial bridge to talk to the microcontroller on the Arduino. But you could also use the RX/TX pins to do that.

Hardware/software serial for HC-05


Can a pilot who is not a CFI give instruction?

Question: Can a pilot (other than an ATP) who is not certificated and current as a CFI give instruction in aircraft required for the issuance of a pilot certificate, e.g. a private pilot certificate?
Comment: Anyone can give instruction, however someone like you describe may not give instruction *which may be logged towards the issuance of a pilot certificate*.  You still need to receive the required instruction from an authorized instructor, no matter how much another pilot may have already taught you.
Comment: As I remember it (1970's) ground instruction did not have to be given by a pilot but the FAA did have a certification as "ground instructor". A quick look at 61.211-217 appears to have not changed. So, even a non-pilot can take the "ground instruction" test and log ground school.
Comment: There are quite a few instructors in a Part 142 training center that are not CFIs.  I don't know of any training centers though that would train private pilot candidates.  These centers usually train pilots for aircraft type ratings and ATP certificates.  I mention it because it is different than privileges an ATP pilot would have.
Answer: I'm assuming that you're asking about FAA regulations. Anyone can train anyone else - how effective and safe that training is is a different question! - but only an instructor can issue endorsements, including signing off on training time, endorsing solo flight, and accepting a student pilot application (see 14 CFR 61.193 and 61.215).
This is from 14 CFR 61.51:

(h) Logging training time. (1) A person may log training time when
  that person receives training from an authorized instructor in an
  aircraft, flight simulator, or flight training device.
(2) The training time must be logged in a logbook and must:
(i) Be endorsed in a legible manner by the authorized instructor; and
(ii) Include a description of the training given, the length of the
  training lesson, and the authorized instructor's signature,
  certificate number, and certificate expiration date.

In theory, a non-CFI could train a student to perform as required by the ACS. But, a non-CFI couldn't authorize the student to fly solo, and he couldn't endorse the student's training time in his logbook. The student would end up able to fly but unable to get a certificate because he'd have no official training time and no solo time. So it wouldn't really be helping the student much: he'd have to go and do the required hours over again with a CFI anyway.
Comment: I can see how it might help a student who has the REQUIRED hours but isn't yet comfortable with all the procedures needed to pass the exams. A family member or close friend who has the experience can then give some extra training sessions that while they can't be logged as training time can help increase confidence and skill level. Combined with more official lessons to get the endorsements this may speed up the learning process at reduced cost.
Comment: @TomMcW I doubt it. The PIC is always responsible, that's the law. And if he picked up a bad habit, the person handling his examination would fail massively if he didn't catch it.
Comment: @Someone-OnStrike most of Europe, and probably elsewhere. Only government licensed driving instructors are allowed to give driving instruction.
Comment: @jwenting That's true, but you have to weigh those benefits of a non-CFI  against him creating, tolerating or not even noticing bad habits on the part of the student. I'm sure there are some cases where it works out, though.
Comment: I would also be concerned if the non-CFI would be opening himself up to legal consequences if there was an accident. "So, Bill, why did you do X?" "Because that's what Joe taught me to do." So Joe ends up being sued for Bill's accident
Comment: @Pondlife true. I was going from my own experience learning to drive where I'd have benefited massively if I'd been able to drive my dad's car legally with him in the passenger seat a few hours before exam time. I was so nervous for the exam I made all kind of mistakes and failed the exam several times despite knowing everything inside and out. Some confidence building time would have helped me massively. As is, the driving school got to play that role and made quite a bit of extra money out of me :)
Comment: @jwenting where was that? Here in Oregon I had to log 100 hours with my parents (could have been any licensed driver over 21 iirc, but I did almost all with my parents). Had I taken a driver ed course, though, it would have only been 50.
Answer: A person who holds a Ground Instructor certificate can.  Persons who hold a Basic Ground Instructor certificate may provide ground instruction, knowledge test endorsements, and ground portions of a flight review required for Sport, Recreational, or Private Pilot certificates.  Persons who hold Advanced Ground Instructor certificates can perform ground training and the required endorsements to take a knowledge tests for any airman certificate or rating, except instrument ratings.  They may also perform and sign off any airman for the ground portion of a flight review.  Instrument Ground Instructors may provide ground training, knowledge test recommendations and training and sign off for the ground portions of an instrument proficiency check.  The person who only holds a Ground Instructor certificate cannot, however, provide any flight instruction, including instruction in a ground based flight simulator or flight training device.
Airmen who hold an ATPL may give ground and flight instruction, but this is limited to air transport operations as prescribed in §61.167, unless said individual also holds as Flight Instructor certificate.
Comment: I guess the relevance of this answer to the question, depends on how literally we are to take the meaning of the word "in" -- "Can a pilot (other than an ATP) who is not certificated and current as a CFI give instruction *in* aircraft required for the issuance of a pilot certificate, e.g. a private pilot certificate?"


What is the most efficient way to check whether a BYTEA column contains data, in PostgreSQL?

Question: We have an online platform where we sell eBooks. In the database, we have a "books" table, which contains the books' information. It also contains the book file, stored as BYTEA.
In various pages, I need to check if a book's file exists in the database.
But I have noticed that the pages load slowly, so I was wondering if it is being caused by the manner in which I am checking.
Currently, I am checking if "book_file IS NOT NULL". Does PostgreSQL read the whole file, in order to determine whether it is not null, which could be slowing things down? If so, is there another way to check if the file exists, without having to read the whole file?
I read up on some binary string functions on the PostgreSQL documentation and was wondering if functions like octet_length(string), substring(string [from int] [for int]) or get_bit(string, offset) might perform better?
Below is an example of a simplified query I am using to check for the existence of the file.
SELECT books.book_title
FROM books
WHERE books.book_file_pdf IS NOT NULL
ORDER BY books.book_id DESC

Does this kind of condition slow things down? If so, can this query be optimized, to check solely if the file column is not empty, without reading the file?
Answer: IS NULL / IS NOT NULL is the most efficient check for NULLness. You can speed it up with an index, if you really need to have it fast:
CREATE INDEX ON books (book_id) WHERE book_file_pdf IS NOT NULL;


How to secure embedded code containing REST api call

Question: I am making a Google Analytics like service where you embed generated code into your website and it tracks certain data. I have a backend REST api, but I am not sure how to securely implement a call to it in the frontend without all the authentication data being exposed. I am worried that if a user embeds this code into their website with authentication, such as a session ID or a user ID, anybody would be able to just take that data and make a call to the api before the session times out and mess with the user's data. Is there any way to prevent this risk and safely design the backend api and the call so that it is much more difficult or impossible for people to make calls to a user's private api?
Comment: In short, no, but this is why you write code secure against XSS, enable HTTPS, and use session tokens instead of raw login credentials to authenticate with. If your client is compromised, the attacker can do anything the client can, so you protect the client from being compromised.
Comment: Just to be clear, when you say "user" are you talking about a consumer of your web service who is putting your front-end code on a site they own, or do you mean an end-user who is viewing such sites with their browser? Depending on the design and the objectives, the security situation is going to be pretty different. (Also, obligatory comment: you ***cannot*** make anything that is designed to track people and cannot be spoofed, tampered with, or blocked. Your data will always have error.)
Answer: You can have something like a JWT token, where the user (front-end) will know, but can't read it. Then, for each request you send the JWT token and your back-end will know how to decrypt and validate if the user can perform or not this action.


Can multiple inquiries with only one mortgage lender over months hurt your credit?

Question: We applied for a home loan in the beginning of January and was told to wait 2 months. I want to know if multiple credit inquiries from only ONE lender will hurt or does it count as one creditor? Over a several month period.
Comment: Not really an answer but if you're afraid of them hitting your account multiple times you can always freeze your credit and only un-freeze it when they need to pull a report.
Answer: Typically, one lender should only need to run one "hard" credit inquiry when you are applying for the loan. They may also require a second inquiry just before closing to confirm your situation has not changed. What is counted for credit purposes is the number of inqiries, not the number of lenders. However, this level of activity should not impact your credit significantly.
A more problematic scenario is if you are also getting quotes from multiple lenders in a short period of time, which can impact your scores more significantly.


Give access to a folder for a specific person using email

Question: I have a processing machine that is running on Linux and is used by many people. This machine has only one user where people using this machine can login and use the machine. What I wanted to do is to create a folder for each person where they can place their data and it will be secured using their email and password for example, so that others will have access to everything except other people private folders. So for example in ~/Documents there will be a folder for each person where only this person can access the content of this folder. Any advice?
Comment: you need a separate account for each user.
Comment: @cas but they use everything in the machine all together, how I can do this? Like I want them to see and use everything in the machine (applications,....) except folders of other people.
Comment: if you only have one user account, there is no way for the system to know who is using it at any given moment.  The best you could do without individual user accounts is an "honour system" and hope that other people don't sneak a look at someone else's private files.
Comment: @cas What is an "honour system"?
Comment: an honour system is where you trust to the honour of people not to do bad things.  with predictable results.
Comment: @cas  Oh okay, so it's not a technical thing it's a moral thing
Answer: You need a separate account for each user.  There's no way around this if you want users to be able to have private files.
If you also need a shared documents folder (as well as each users private folder), then create a unix group, add all users to that group, use chgrp to set the shared directory's group-owner to that group, and chmod g=rwsX on the directory to enable all group members to read, write, cd into, list files, etc.  This s (sticky bit) in the g=rwsX  chmod mode makes sure that all files and subdirectories created in the shared directory are also owned by that group.
For example:
addgroup --group shared    # create group called 'shared'

addgroup username shared   # add username to group 'shared'. repeat for every user

mkdir /home/shared
chgrp shared /home/shared
chmod g=rwsX /home/shared

You can either create a symlink in each users' home directory pointing to /home/shared (and create one in /etc/skel too so newly created users get it by default), or just tell everyone to look for shared files in /home/shared.
Comment: what if I had 100 users? I'll make 100 user accounts on the machine?
Comment: yes.  alternatively, make accounts for those who want private space, and a shared account for everyone else.   BTW, it's not terribly difficult to script the process of adding accounts, just use the right command line options to `adduser` so that it doesn't have to prompt for everything (and use `--disabled-password` - you can set the passwords later in the script with `chpasswd`).   For passwords, generate a file containing a line 'username:random_password' for each user and pipe that into `chpasswd`.  Then give each user their  personal password and tell them to change it ASAP.
Comment: Thank you, I've upvoted your answer. Is it possible to update your answer with a script that process adding accounts? As I'm not good with commands and scripts. Thanks again in advance
Comment: here's an example: https://unix.stackexchange.com/a/79912/7696.   You'll need a list of username and real names (for the GECOS field).  You also need a list of usernames and passwords.  You can generate random passwords with tools like `pwgen` or `makepasswd`.  Your script will need to loop around the `adduser` command, once for each user.  You can just pipe the entire file with username:password into `chpasswd` in one go.   If you have trouble implementing that, post a **new** question showing what you've done so far and what you're having trouble with.
Comment: btw, you'll also need to distribute the passwords to the users.  one simple way is to print the username:password list with a few lines between each user, and cut it into small strips, one for each user with their login details.  remind them to change their password as soon as the log in.  or you can force that with `chage -d 0 username` (see https://unix.stackexchange.com/questions/173708/how-do-i-force-a-user-to-change-a-password-at-the-first-time-login-using-ssh)


Which thermoelectric effect is better?

Question: I am doing an experiment which requires the thermoelectric effect. I know about the Seebeck and the Peltier effects. Well, from what I have found till now on these topics is that they both can produce electricity through temperature differences and both can produce heat or cold through electricity, but have different ways of doing it. Can anybody tell me the comparison between both of them based on their pros and cons. I don't want to go very deep into this topic right now, but I just want to ask that if I have to buy a Peltier's or Seebeck's electricity generating module, then which one will be better. By better I mean what is the difference between the amount of power they generate and the difference between their costs.
Answer: If you're looking to produce power from a temperature differential, go with a device optimized for the Seebeck effect. Peltier and Seebeck effects are essentially the same thing, or rather flip sides of the same thing, but thermoelectric generators (Seebeck) are optimized differently from thermoelectric coolers (Peltier).
Comment: thank you, but can you tell me what will be the difference in the costs of both?
Answer: The Peltier and Seebeck effects are each others opposites so to say.

The Seebeck effect is described by the electromotive force or voltage $V$ generated at a temperature difference $\Delta T$ across the ends of a material:
$$V=S\Delta T$$
$S$ is the Seebech coefficient and is a material constant that depends on charge carriers, material density and much more.
The Peltie effect is the generation of a heat flow $Q$ from one junction to the other (heating of one end while cooling of the other) of a unicouple when a current $I$ flows:
$$Q=\Pi I$$
A unicouple is simply two fitting materials (semiconductors) that are put together end to end. $\Pi$ is the Peltier coefficient, which is a property of the unicouple.

Now, both a "Seebeck module" and a "Peltier module" can be reversed. They are both build as several unicouples in electric series (which is called a module). Apply a voltage to the Seebeck module and you get cooling/heating. Apply a temperature difference across a Peltier module and you get a voltage difference.
But as has been said in another answer, since the two modules are intended for each specific purpose, they might have been optimized only two that specific use. In the Seebeck module the Seebeck coefficient of the materials might be prioritized, even if it might mean some damage done to the peltier coefficient. And vice versa. Therefore, pick a Seebeck module for power generation.
The temperature range that you are going to use the module in has a large influence on the coefficients of materials. Look out for that specification.
Comment: Could you specify your sentence " In the Seebeck module the Seebeck coefficient of the materials might be prioritized, even if it might mean some damage done to the peltier coefficient. And vice versa."? As far as I understand, they are linked through Kelvin relation $\Pi = ST$, so a "damage" to either $S$ or $\Pi$ looks like a damage on the other one.

Which thermoelectric effect is better?


Journey Builder - BCC Email Address

Question: I configured a journey in Marketing Cloud where i sent an email. My requirement is adding BCC email addresses to this email, but I noticed that we can only add valid email addresses.
Could you confirm me that is not possible to add BCC /CC Address using personalization strings or Ampscript functions (e.g. Lookup) inside the Journey Email's settings?
Answer: I just received feedback from salesforce marketing cloud technical support and they confirmed me that at this time it is not possible to include a personalization string or ampscript function in the bcc or cc field of the journey builder email activity. It will only accept one valid email address.
Comment: This is no longer the case. You can add multiple addresses and personalization strings or inline AMPscript is now supported. Refer to [this answer](https://salesforce.stackexchange.com/a/325631/5449).
Answer: Now it's possibile to manage this use case ;)
Before you need to open a case to request the activation of the CC and BCC feature.

Journey Builder - BCC Email Address


Why are blue light-emitting diodes important enough to warrant a Nobel prize?

Question: I am using a miniature blue light as night bed room light since my childhood. For me blue light-emitting diodes almost look like miniature blue lights. I don't see any fundamental scientific breakthrough in it. So why are blue light-emitting diodes important enough to warrant a Nobel prize?
Comment: You might compare this post to your question. It too is a technological advance, not a fundamental breakthrough. Never the less, it is truly important. What is Chirped Pulse Amplification, and why is it important enough to warrant a Nobel Prize? Perhaps an answer that shows blue LEDs to be similarly important would be satisfactory? https://physics.stackexchange.com/q/432137/37364
Answer: From the Nobel press release...

This year's Nobel Laureates are rewarded for having invented a new energy-efficient and environment-friendly light source – the blue light-emitting diode (LED). In the spirit of Alfred Nobel the Prize rewards an invention of greatest benefit to mankind; using blue LEDs, white light can be created in a new way. With the advent of LED lamps we now have more long-lasting and more efficient alternatives to older light sources.

https://www.nobelprize.org/prizes/physics/2014/press-release/
They do not seem to claim that the prize is for the best science but for a use of physics that benefits humanity.
You may not agree with awarding the physics prize for this reason. Perhaps that would be more like a "Nobel Prize in Engineering" or perhaps even the Peace Prize if someone wants to argue that LEDs are good for the environment. However, they do not seem to think that the physics is revolutionary, just that the invention has a major positive impact on humanity.
Answer: There's nothing that I can see in Alfred Nobel's will that refers to fundamental scientific breakthrough.
What it does say is:
...to be distributed annually as prizes to those who, during the preceding year, have conferred the greatest benefit to humankind.
The blue LED arguably meets that criterion.
Answer: In addition to white LED lamps (as given in @Dave's answer)
there is one more technical application.
With the availability of blue LEDs, it became possible
to build LED color screens for TV and computers,
and replace the energy-consuming and bulky
screens based on cathode-ray tubes.
This was not possible by using only the previously existing
red, yellow and green LEDs.
Comment: ... and the white LEDs in your cell phone,  automobile headlights, and replacing tungsten and CFLs in your light fixtures.


LED frequency indicator for multiturn knob

Question: I'm designing a simple SW receiver for the 20m band and need a rudimentary frequency indicator activated by the multiturn rotary knob. The knob is part of a recuperated Pritt gluestick mechanism pushed into service as a PTO-drive for the VFO. The idea is to use reed switches to power the indicator LEDs on the frontpanel. On the glueholder a stick is glued which holds a magnet at the end. As the knob is turned, the magnet advances over 6 reed contacts, each in turn activating a corresponding LED on the frontpanel. Of course, as soon as  the magnet is advanced, the active LED is switched off and there is no indication for the duration of the next cycle until the next LED is turned on. Is there a way to make it so that the last LED remains lightened until the next is switched on? Of course this also need to work in reverse. Thanks beforehand for your help!
Answer: You are trying to describe a very Rube Goldberg type of mechanism for something that should be done in a much more uncoupled manner. You should come up to speed what microcontrollers are all about. Have the microcontroller (MCU) able to detect position of the knob (which can now be a simple potentiometer feeding an A/D converter OR a rotary encoder feeding quadrature waveforms to two inputs). The MCU would also control the display and run the VFO. You tie all this together with software that can easily solve the problem of when the display should change in relation to how the rest of the things change.
Comment: Thank you for your prompt and knowledgeable reply! I'm sure there are more elegant ways to solve this kind of problem but since this receiver is aimed at the beginner with basic knowledge of analogue electronics, solutions involving microcontrollers or Arduino are out of the question. It's ironic that you call my proposed mechanism a Rube Goldberg type of solution in this respect...
Comment: @ErikDevriese - You may want to revise your perception regarding microcontrollers. Things like the Arduino and the Raspberry Pi have completely changed the landscape of what beginners that barely understand electronics are doing these days.
Answer: For each reed switch you need a D type latch and specifically you need a D type latch that has a clear pin. For all D type latches you wire the "D" inputs to logic 1. For the D latch that is directly associated with a particular reed switch, the reed switch feeds its clock input.
This means that one side of the reed switch is tied to logic 1 and the other side that connects to the clock has a (typically) a 1 kohm to 10 kohm pull-down resistor.
That clock input also connects to the other D latch clear inputs via individual diodes to each clear pin. Ensure that there is a pull-down resistor on each clear input.
Step and repeat for all reed switches and D latches.
Or just use a microcontoller and software to control the LEDs
Comment: Is PR set to 5V for every D-flop? What is the value for the pull-down resistors in series with the diodes? Can I simply connect the the LEDS via a resistor to the Q-outputs from +5V supply? Thanks!
Comment: Which chip are you thinking of that has a PR pin? Pull down resistors are not series but from clear input to 0 volts and 1 k to 10k. What LEDs are you thinking of using?
Comment: This site explains the workings of a D-flop. It does not mention a particular chip: http://www.instructables.com/id/D-Flip-Flop-With-Preset-and-Clear/ I plan to use standard red LEDs. Sorry, my digital experience is very shallow!
Comment: I just want to be sure what you mean by a "PR" pin.


How to add a very big string as a default value of a custom field?

Question: In my salesforce app, there is an aura:component which contains a Html Page Builder. I use Bee Plugin to do that. When the user designs the page and clicks the Save button, Bee plugin will generate html and json code of that page. I will save those two in a custom field in a custom object, so that I can load the json code each time when the user opens this component. Everything  works fine. The only problem I have is that I want a particular template to be opened when the user opens the app for the first time. My plan was to set the json code as default value for the field that saves the json code. Lets call that field JsonCode__c. So, basically I want to set a 1000 lines of json code as default value for the field JsonCode__c. But, when I go to the salesforce Setup -> Object Manager, and tried to paste the code to the default value text area of the field, only few lines of the code is getting pasted. So, how can I do that? How to add a very big string as a default value of a custom field? The data type of JsonCode__c is Long Text Area.
Answer: Custom text fields only support 255 characters. You can try using a rich text area or long text area, but you'll have to use Apex to populate the field before the record is created (i.e as a default value).
In particular, you'll need to use a Before Insert Trigger.
Comment: i am using `long text area`. i think the problem is not with length because insertion works fine for 1000 lines of code. setting default value is the problem
Comment: @JayeshBabu When you set a default value, you're technically setting up a formula. It's possible your JSON exceeds the 4KB max size allowed for formulas, though I would hope Salesforce would have an error for that scenario.
Answer: You can set the default template value in the lighting component itself. When the user loads the record using your component and there is no data in that field just put the default value in the field. Also, you can put that value if it's a new record.
To be able to change the default template, without changing the code. Use the static resource to store it and load the resource in the component, so the admin can change the template whenever needed.


Who were the "craftsmen" in Zechariah 1:20-21?

Question:
[Zec 1:20-21 NASB20] [20] Then the LORD showed me four craftsmen. [21] And I said, "What are these coming to do?" And he said, "These are the horns that have scattered Judah so that no one lifts up his head; but these [craftsmen] have come to frighten them, to throw down the horns of the nations who have lifted up [their] horns against the land of Judah in order to scatter it."
Answer: Incidentally, some Bibles place this passage at the beginning of Zech. 2, rather than the end of ch. 1. In any case, two of the four horns are easy to identify while the four craftsman or smiths are not so clear.
Four Horns
Historically, around 690 BCE. Assyria nearly conquered Judah, capturing every major settlement except Jerusalem. Since this nation forced many citizens of northern Israel and other nations into exile it probably did so with leaders of the towns is conquered in Judah as well. Babylonia succeeded in conquering the whole country of Judah and taking many people as captives to Babylon (not to mention those who fled elsewhere). Persia is sometimes mentioned as a third candidate. Other possibilities are Egypt, Syria, Ammon, Moab and Edom. Some commentators suggest that the prophet's number four may not imply exactly four nations but the totality of military forces that cause people in Judah to flee.
Four Craftsman
The four craftsmen/smiths are harder to narrow down. What is clear is that they represent forces used by God to heal what was done by the four horns. In terms of contemporary people, Zechariah himself speaks of two "anointed ones" - apparently Zerubbabel and the high priest Joshua. Zerubbabel is mentioned specifically as a builder.

9 The hands of Zerubbabel have laid the foundations of this house, and
his hands will finish it. Thus you shall know that the Lord of hosts
has sent me to you. 10 For whoever has scorned such a day of small
things will rejoice to see the capstone in the hand of Zerubbabel.
(Zech 4)

Zerubbabel and Joshua were succeeded by Nehemiah and Ezra, who completed Jerusalem's restoration; and that does make four. So this may be the solution in terms of a near-term fulfillment of the prophecy. Historically we may certainly include Cyrus of Persia as a candidate along with later Persian leaders who helped restore Jerusalem and allowed Judah to reconstitute itself. Nations should also be considered: Persia allowed the Jews to return and rebuild. Greece and Rome also enabled significant building projects and a large degree of religious tolerance (with notable exceptions). The Maccabean leaders who revolted and established an independent Jewish nation in the second c. bce also should not be ruled out.
Long-view interpretations are literally all over the map. The Talmud speaks four anointed ones: the Messiah son of David, Messiah son of Joseph, the Righteous Priest and Elijah.

Who are these four craftsmen? Rav Ḥana bar Bizna said that Rabbi
Shimon Ḥasida said: They are Messiah ben David, Messiah ben Yosef,
Elijah, and the righteous High Priest, who will serve in the Messianic
era. (Sukkah.52b)

But as is often the case with the Talmud, other rabbis had different opinions. Four kingdoms that protected or would protect Judah is a frequent alternative. Modern Christian commentators often attempt to correlate Zechariah's craftsmen/smiths to the Book of Daniel's horns and kingdoms or similar imagery in the Book of Revelation. But when we get into interpretation of Last Days prophecy applied to contemporary events, the possibilities are too numerous to consider here.
The four craftsmen or smiths are a symbol that is open to very wide interpretation. Zerubbabel, Joshua, Ezra and Nehemiah are possible near-term candidates. Cyrus of Persia and his successors are other likely possibilities. Nations rather than individuals may also be "craftsmen." Beyond that, the candidates mentioned by various commentators are very numerous.
Answer: In Zechariah 1:18, there were four horns; in Zechariah 1:20, there were four craftsmen. According to the angel explanation;

He answered, "These are the horns that scattered Judah so that no one could raise their head, but the craftsmen have come to terrify them and throw down these horns of the nations who lifted up their horns against the land of Judah to scatter its people. (Zechariah 1:21 NIV)

Therefore the horns were Judah's enemies but the craftsmen were helping Judah against them. To understand who the craftsmen were, let's review some backgrounds.
It begun with Jeremiah's prophesy of 70 years desolation of Jerusalem and its subsequent promise from God;

10 This is what the Lord says: "When seventy years are completed for Babylon, I will come to you and fulfill my good promise to bring you back to this place. (Jeremiah 29:10 NIV)

The Lord did not just bring them back to Jerusalem, He promised their safety as well, that in the book of Ezekiel, He said;

25 "'This is what the Sovereign Lord says: When I gather the people of Israel from the nations where they have been scattered, I will be proved holy through them in the sight of the nations. Then they will live in their own land, which I gave to my servant Jacob.
26 They will live there in safety and will build houses and plant vineyards; they will live in safety when I inflict punishment on all their neighbors who maligned them. Then they will know that I am the Lord their God.'" (Ezekiel 28:25-26 NIV)

In Ezekiel 25-29, those nations the Lord rebuked included Amon, Moab, Edom, Philistia, Tyre, Sidon and Egypt. They were Judah's neighbouring nations and from time to time Judah had conflict with.
Now the book of Zechariah started with that seventy years passed and it's time for the Lord's commitment be fulfilled. It started with a vision of four horses or four horsemen. There was a man mounted on a red horse, standing among the myrtle trees in a ravine. Behind him were red, brown and white horses (Zech 1:8 NIV). The myrtle trees is an apt symbol for restoring and establishing the Lord's promises. It had mentioned in the book of Isaiah;

12 You will go out in joy and be led forth in peace;
the mountains and hills will burst into song before you,
and all the trees of the field will clap their hands.
13 Instead of the thornbush will grow the juniper,
and instead of briers the myrtle will grow.
This will be for the Lord's renown, for an everlasting sign, that will endure forever."

With these understanding, the word 'four' should not be read literally, instead its sacred meaning of 'completeness'. That is, the Lord promised to bring the exiles back to Jerusalem and would completely protect them from harm by scattering all their enemies, so that they could rebuild the temple in Jerusalem and restore their dedication to God in a peaceful surrounding.
Hence the four craftsmen represented the magnificent deeds of the Lord, as He suppressed all surrounding nations to protect Israel from harm.


C# File.ReadallText doing weird things

Question: What I'm trying do is read all the text in a file and if it contains the word "Share" do a regex.  Here is the code:
DirectoryInfo dinfo = new DirectoryInfo(@"C:\Documents and Settings\g\Desktop\123");
        FileInfo[] Files = dinfo.GetFiles("*.txt");
        foreach (FileInfo filex in Files)
        {
            string contents = File.ReadAllText(filex.FullName);
            string matchingcontants = "Share";
            if (contents.Contains(matchingcontants))
            {
                string sharename = Regex.Match(contents, @"\+(\S*)(.)(.*)(.)").Groups[3].Value;
                File.AppendAllText(@"C:\sharename.txt", sharename + @"\r\n");
            }

        }

When I debug I get...
contents = "\r\0\n\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0=\0\r\0\n\0+\0S\0h\0a\0r\0e\0 \0\\0\\0j\05\02\0\\0w\0w\0w\0_\0O\0n\0t\
\0S\0h\0a\0r\0e\
Not Share.  Any hints? tips or suggestions?
Answer: Looks like you've got a file which is saved as UTF-16 (i.e. Encoding.Unicode). Read the file with the right encoding, and all should be well.
Fortunately there's an overload of File.ReadAllText which takes an encoding:
string contents = File.ReadAllText(filex.FullName, Encoding.Unicode);

Unfortunately, that will then do the wrong thing for files which aren't in UTF-16. While there are heuristic ways of guessing the encoding, ideally you should know the encoding before you open the file.
Answer: Looks like it's a Unicode file, and you're trying to read it as plain ASCII.
Comment: Actually without specifying anything else, it'll try to read the file as UTF-8.
Answer: My guess is that the encoding is not set correctly, you might need to use ReadAllText(String, Encoding) specifying the encoding.

C# File.ReadallText doing weird things


Can we use Power BI to generate reports from SharePoint 2013 ON-PREMISE data (list and libraries)?

Question: There are a lot of articles talking about integration of Power BI with SharePoint online.
Can we use Power BI to generate reports from SharePoint 2013 ON-PREMISE data (list and libraries) ?
Answer: Yes, but you need the On-Premise Gateway running on a server on your network. Power BI accesses it through the gateway.
Comment: Be aware that there are two gateways - Personal and Enterprise. Personal GW is used only for one user and is running only when the user is signed in to PC. Enterprise gateway is running as Windows Service and is supposed to be used for all users but it requires Pro license for all users accessing the reports.
Comment: Thanks for the information. Can you please mention some suggested links having the details of the same ?
Comment: It's on the Power BI site when you log in. At the top right, where you see a series of icons, click the one that looks like an arrow pointing down at a line. The drop down menu has an option for Data Gateway.


Possibly bringing American XBOX One S to Japan

Question: When bringing the American version of an XBOX One S to Japan, how viable is it to buy games from a local Japanese store and play them on the American system?  Are there region settings blocking that?  Is there a difference in the programming that blocks it?  I think this was an issue with systems from several years ago, but am not sure if that's the case here.
Answer: Based on this Reddit thread (and some other Google results) it sounds like the answer is no, the XBOX One is not region locked.  (I assume this is also true of XBOX One S as they are considered the "same generation.")  So you should be able to play games from anywhere on your machine.
However, take note that it sounds like DVD and Blu-Ray playback is still region-locked based on whichever region the console was manufactured for.  I'm not going to link to the sources I found on that point, since they appear to be websites of questionable intent, and I'm not sure how Arqade views linking to such places.
Mind you, this only really matters if you're planning to use your XBOX as your primary movie machine (and you still buy movies on disc :P)
Answer: You should be fine. There's no region locking for games on the Xbox One, according to official Xbox support. However DVDs and BluRay discs are region locked, so you will have to be careful with that:

Each Xbox One console is manufactured for a specific Blu-ray and DVD region, following international standards. The Xbox One console can play Blu-ray discs and DVDs that are sold in the same region as the console. See the following tables for the countries in each disc region.
Some Blu-ray discs and DVDs are not region-encoded or are coded to all regions. Region-free Blu-ray discs and DVDs will play on any Xbox One console.
Note: Game discs for the Xbox One console are not coded to regions.


What does this mean. "Ce look-là" From french Extra

Question: I know it is wrong to translate from word to word, but can someone shed more light on this, please.
Answer: The words -ci and -là are particles you use with ce/cette/ces.  Generally, cette chose-ci would be translated as this thing and cette chose-là would be translated as that thing, so ce look-là would be that look.
If somebody says cette chose without a particle (which they actually do most of the time), there are two possibilities:

it's completely clear whether they mean this or that from context, so they don't bother adding the particle,
it doesn't make any difference whether you use this or that, so there's no need for the particle.

There are occasionally cases where French speakers say cette chose-là when native English speakers would use this thing. I've encountered these cases reading French, and they've puzzled me somewhat, but I'm not a fluent French speaker, so I can't say exactly when this happens.
Comment: Unlike the *this/that* clearly distinct meanings, the form *-là* tends to be used for both in French, possibly because *-ci* is perceived to be more formal. You hear more and more *Tu veux çui-là ou çui-là ?* instead of *Tu veux celui-ci ou celui-là ?*


How can pilots identify, in flight, the cracked layer(inner/middle/outer) from an impaired windshield?

Question: Depending on the cracked layer, there would be some actions from the crew.
The inner layer seems to be simple to identify, but if the middle and/or outer layer is cracked, how will pilots identify the right crack's position?
Answer: It is possible to identify whether the crack affects the inner layer by sliding over it with nail or something sharp like pen. If the layer is cracked, the slight indenting in the surface can be felt.
As far as I can tell, there is no way to tell whether the outer or middle layer is affected with any useful degree of certainty. It is also not possible to ascertain how many layers are cracked. So usually the procedure is so that if the inner layer is not affected, you can continue and fix the issue at destination and if the inner layer is affected, you have to conservatively assume all layers may be affected and descend.
Comment: @Sean, I don't think there will be any significant airflow through a crack. Certainly not to either hear it over all the other noise in the cockpit and even less so for the pressurisation to be affected (the outflow valve is quite big opening, even a hole in the window would be small compared to it).
Comment: Shouldn't it be fairly easy to tell whether all the layers are cracked versus just the inner layer, by listening for the noise of air whistling out through a full-thickness-cracked windscreen and/or checking whether the pressurisation system is suddenly having more difficulty keeping the aircraft pressurised than it was pre-crack?


Sony a7III starts shooting JPEG even after I choose RAW

Question: Despite the fact that I set to RAW, at some point the camera begins to shoot JPEGs only. My guess is that this is related to the space available on the SD card. If so, is there any way to turn this off and continue shooting RAW until the card is full?
Comment: Did you change the mode you shoot (A, M, S, P)?
Comment: I alternate between A and M.
Comment: Is it possible that you have a custom button set to "File Format" and are hitting accidentally? There isn't a function to revert to JPG when running out of space.
Comment: Is card almost full perhaps?
Answer: After doing some research I found 3 more people encountering this. At first I thought the same as you: the space does no longer suffise for another raw, so the camera fills the rest with jpgs.
However, this also happened to a wedding photographer in-midst a burst shooting. So there is no way, the person could accidentally switch any relevant setting while holding down the shutter button.
I believe you encountered a firmware bug.
You can find out your version number in the settings / setup-tag / version. With that information please go to the Sony website and check if that is the most current version.


The math problem is too difficult for `X` to work out

Question: There are four options: everybody, somebody, anybody and nobody.
Which one should be used in X place ?
Comment: *Nobody* would never be acceptable. Of the other three, *somebody* is unlikely, but just about feasible in certain contrived contexts - or maybe when *somebody* is a facetious usage meaning ***you*** (the person being addressed). The difference between using *everybody* and *anybody* is General Reference (if you use *everybody*, you're implying that *some, but not all* people can work it out; if you use *anybody* you're saying there aren't any people at all who can work it out).
Answer: As FF has pointed out, only everybody and anybody are acceptable
(everyone and anyone also work). They work, and the others don't, for the same reasons:

Too is a Negative -- too Adj to VP means 'so Adj that Not VP';
therefore NPIs like anyone work within its scope,
and so anybody is used here, instead of somebody.
That's also why nobody is ungrammatical here, because that would mean
*The math problem is so difficult that nobody can't work it out.
which is ungrammatical (that's what the "*" means).
Everybody, somebody, and anybody are all Quantifiers -- logically, ∀ and ∃.
By DeMorgan's Laws, propositions with both a negative and a quantifier are ambiguous.

Note the opposite orders of not (logically ¬),
  compared to some/any (∃) and every (∀) below.

I.e, Everybody doesn't like it
can mean
either
It is true that there is somebody who does not like it.
¬(∀x) φ(x) ≡ (∃x) ¬φ(x)
or
It's not true that there is somebody who likes it.
¬(∃x) φ(x) ≡ ∀(x) ¬φ(x)

So the two choices that are grammatical do not mean the same thing.

The test is too difficult for everybody to figure out means
'The test is so difficult that there are some people who can not figure it out'
The test is too difficult for anybody to figure out means
'The test is so difficult that there are no people who can figure it out'
Answer: Which of everybody, somebody, anybody and nobody should be used depends on the meaning to be conveyed. If the meaning is that the problem is so difficult that nobody can work it out, then (as other answers indicate) the best fit is:

The math problem is too difficult for anybody to work out.

If, however, the meaning is: Nobody finds the problem too difficult to work out, then nobody fits:

The math problem is too difficult for nobody.

Admittedly, adding back the (superfluous) to work out makes the sentence now sound a little awkward:

The math problem is too difficult for nobody to work out.

So I prefer:

The math problem is too difficult to work out for nobody

with appropriate prosody.
Answer: The fifth option is the pronoun one, as in The problem is too difficult for one to work out.
This usage is synonymous with the usage described by FumbleFingers above of anybody, but I believe is a more likely usage in dialogue or conversation.


Complete Condition in Banach Fixed Point Theorem

Question: Can someone provide an example to show that for the Banach fixed point theorem, that is if $T : X → X$ is a contraction in a complete metric space $(X, d)$ then $T$ has a unique fixed point that $X$ is complete is an essential condition?
Comment: It is not necessary for $X$ to be complete.  Take $T: \mathbb{Q} \to \mathbb{Q}$ defined by $T(q) = q/2$, where $\mathbb{Q}$ is the rational numbers with the usual metric.  $\mathbb{Q}$ is not complete.  $T$ is a contraction with a unique fixed point ($0$).  Did I misunderstand something?  Maybe you are asking why the fixed point might not exist if $X$ is not complete?  The answer below is an example.
Answer: $$T \colon \mathbb{R}\setminus\{0\} \to \mathbb{R}\setminus\{0\};\; T(x) = x/2.$$
Basically, all examples are of that form, since a contraction is uniformly continuous, and can thus be extended to the completion of $X$, and the extension is also a contraction. So the extension $\widehat{T}\colon \widehat{X}\to\widehat{X}$ satisfies the premises of Banach's fixed point theorem, and has a unique fixed point.


Would this be considered a malapropism?

Question: Would it be considered a malapropism to substitute a word or portion of a word in a phrase with another word or portion of a word, generally rhyming with the original word, and generally considered an offensive replacement? For example, the term "Election Day" substituted with "Erection Day" or the company name "Pizza Hut" to "Pizza Slut"?
Comment: Not really. Each of those would be known as a *play on words*. A malapropism is usually an unintended confusion of a word with one that sounds similar but means something entirely different. E.g. "They had a fine time at the party, dancing the flamingo" (flamenco).
Comment: Are your substitutions deliberate (and probably *designed* to shock) or accidental (what might be called a Freudian slip)?
Comment: With the possible exception of my stepmother, I do not believe in witches. Anyway, I am indebted to her for this fine example: "The two cars collided head on and were totally diminished."
Answer: I shall attempt an answer based on my having read Sheridan's great work, The Rivals, many, many years ago at school.
Of course, one of the play's characters, the redoubtable Mrs. Malaprop, has delighted generations of readers with a mirthful reminder that the English language is sometimes a source of amusement but also a potential provider of a sine qua non (there I go again, spouting Latin on ELU) for all who wish to cast aspersions on those of us who routinely blunder our way through the language with malapropisms aplenty. Even the late Christopher Hitchins, who harnessed the English language to become the media's outstanding polemicist and iconoclast of his generation, occasionally let fly with a chuckle-inducing malapropism. No one would think less of him, surely!
And I can't agree that a malapropism is always an "offensive replacement", as per the OP's comment. On the contrary, I see no reason to describe any malapropism per se as having this characteristic.
EDIT: Moreover, the OP's "Pizza Slut" for Pizza Hut and "Erection Day" for Election Day are examples of malapropisms which I find amusing and the kind of comical absurdity in keeping with the equally absurd and comical Mrs. Malaprop in Sheridan's 'Comedy of Errors'. I am not offended at all nor would I expect anyone to be other than those of a prissy outlook on life.

Malapropism: "The usually unintentionally humorous misuse or distortion of a word or phrase; especially: the use of a word sounding somewhat like the one intended but ludicrously wrong in the context". (Merriam-Webster)
Comment: A long answer that omits to address the OP's question "Would [these examples] be considered a malapropism?" Perhaps you could edit your answer to address this?
Comment: http://english.stackexchange.com/questions/57517/what-does-persay-per-say-mean
Comment: Peter Point, it's "per se" - Latin for "in itself".
Comment: @Chappo Thanks for pointing out my omission. I'll amend my answer accordingly.
Comment: @KateBunting My feeble attempt at a play on words in faux-Latin backfired! Mea culpa! I'll post an addendum later in the day.
Comment: You think *Erection Day* can be classified as ***unintentionally** humorous* ? Unless it was spoken by someone who doesn't aurally distinguish `L` from `R`, I can't imagine it's accidental. And forget about *pizza slut*....
Comment: @DanBron Quite so! We must down-vote Mrs. Malaprop accordingly. Shame on her, what?

Would this be considered a malapropism?


If each airline flight has a 2.6 in 1,000,000 of an accident and a person goes on 1000 flights, what are the odds for that person?

Question: I would like to understand the way to calculate this particular problem.
I understand that each flight still has a 2.6 in 1M chance of accident.
But a person who takes more flights would seem to be at an overall at higher risk.
Comment: Is this a homework question? If it is, please use the self-study tag.
Comment: Not a homework question and I don't want to do the math - was hoping for an answer and logical explanation of method. My spouse and I just talk about crazy things and this was the discussion in bed this morning. :)
Comment: Try a geometric distribution model.
Comment: Strongly related: http://stats.stackexchange.com/questions/137711/are-your-chances-of-dying-in-a-plane-crash-reduced-if-you-fly-direct/137726
Comment: Your post is not clear. Are you asking for the probability of at least one accident in 1000 flights? (If so, the easy strategy is to work out the probability of the complementary event -- no accidents in 1000 flights - assuming independence).
Answer: Under a simple Bernoulli experiment model setting, we may view each flight travel as an "experiment" with "success" rate $p = 2.6/1,000,000$ and "failure" rate $q = 1 - p$. Let $X$ denote the random variable that the number of flights a particular person travelled to suffer a first accident. Clearly $X \sim \text{Geometric}(p)$, and the odds you are asking is the probability
$$\mathbb{P}(X \leq 1000) \tag{1}$$
This probability can be calculated easily in R, by using pgeom(999, prob = p), results in $0.002596626$.
It is easily seen from $(1)$ that the more flights a person takes, the higher risk he/she suffers, as $\mathbb{P}(X \leq n)$ is an increasing function of $n$.
The above analysis of course depends on the Bernoulli model assumption. Stories could be different if you use other probabilistic models.
Answer: You need to formulate a sequence of conditional probabilities which can then be multiplied by each other. Single flight survival Pr(S) = 1=Pr(crash). So id p= Pr(crash), the probability of surviving all of 1000 flights is the probability of surviving a single flight raised to the 1000th power = (1-p)^1000 ...or with R: (And think of the frequent flyer miles you would have!)
(1- 2.6/1e6)^1000
#[1] 0.9974034

So the probability of having an adverse event prior to flight #1001 would be:
1 - .Last.value
#[1] 0.002596626

Technically these are not "odds" but rather probabilities. People often conflate those terms. In this case the distinction is unimportant.
Comment: I like this approach. Simple and clean :)
Answer: I'm going to give you a simple, almost math-free answer that is hopefully sheds a different light than previous answers.
Each time we fly, we have a small probability of accident 0.0000026. This means, on average, if each trip we take is independent of the other (eg. whatever happens in your first flight cannot affect the chances of accident on your second and so forth), then if we took 10,000,000 flights, we would on average experience 26 accidents. But what if we only took 1000 flights? What's the probability of at least one accident?
Instead of solving for the chance of at least one accident, which will include way too many cases (proability of one accident, proability of two accidents,...,proability of one thousand accidents),
let's solve for the probability there isn't an accident at all (known as the complement). If there is a 0.0000026 chance of accident in one flight, then there is a $$1-0.0000026 = 0.9999974$$ chance of having no accidents. Since there are 1000 flights, we need to take this probability to the power of 1000, or rather, the chance of having absolutely no accident whatsoever on 1000 flights is $0.9999974^{1000} = 0.9974033737$.
What we originally wanted was the probability of at least one accident. What we solved for was however to have no accidents, the exact opposite of this. To get the answers we want, then, we simply again take the complement of this probability $1-0.9974033737=0.0025966263$. In words: If we fly 1000 times, there is a $.3\%$ chance we will face at least one accident.
If some of these concepts (like exponentiating the probability or taking the complement) seem unfamiliar, I recommend reading the first chapters of "A first course in Probability" by Sheldon Ross.


How to install XAP files in a windows phone 8.1 device

Question: I tapped download and install manually option in Windows Phone store and I downloaded an xap file. I transferred the xap file to my Lumia 435 via bluetooth, but the OS does not install it, displaying "Cannot install company app..." I checked out This Microsoft Thread on how to install xap files. It says, "Tap more option on apps list and then tap install local apps (or SD card)." I don't see any such option in my apps list.
Answer: The XAP file is signed using a certificate - most likely from Symantec. That certificate has a corresponding AET - Application Enrollment Token. You need to distribute the AET together with the XAP file in order to allow installation (Microsoft calls it a sideloading process).
Assuming this is XAP that you got internally, just ask the developer for the AET. if it is XAP that you created as a developer, find out how to generate it here


How are Baltic and Slavic languages related?

Question: What are their common characteristics?
I was reading about it on Wikipedia but didn't understand much since I have no background in linguistics. I would appreciate if someone could just name some basic common features (without too much rigor if possible) and give examples. Thank you!
Answer: If you look at the aspect system of Baltic and Slavonic languages, Baltic systems actually resemble the earlier stages of Slavonic systems (Comrie, 1976). In Lithuanian, adding a prefix to a verb root renders it Perfective, sometimes resulting also in some other semantic change. There is also a suffix -inè, albeit with limited productivity, which changes these prefixed verbs back into Imperfective. Latvian is similar, though without this suffix.
This in fact echoes the paths of change in language such as Russian. In the beginning there was a verb, say Russian pisat' ('write'), to which would be added a prefix to form perfective form, either without change in meaning, as in Russian na-pisat' ('write'), or with such a change, as in vy-pisat' ('write out'). Latvian is still at this stage. Later, Imperfective versions of those verbs which gained more-than-aspectual prefixes would appear, so the Russian word vy-pisyvat appeared. Lithuanian is going through this stage.
Source:
Comrie, B. (1976). Aspect: An introduction to the study of verbal aspect and related problems. Cambridge University Press.
Comment: @MaxB The Russian words were intended to illustrate the paths only. There was no implication that cognates exist in Baltic languages, only analogous diachronic processes. I've edited the answer to clarify this; sorry if my original post was unclear.
Comment: the word you transcribe as *vy-pisyvat'* is what I know as a secondary imperfective. From what I understand in your post, the common ancestor to Latvian and Lithuanian did not have such verbs, but they are being innovated in Lithuanian. Why is this happening? Is there "something in the Proto Balto Slavic genes" that has made it separately appear in Slavic and Lithuanian? Or is it under influence from neighbouring languages somehow?
Answer: Lettish and Russian :
galva - голова(head), roka - рука(hand),
pardot - продать (to sell), dot - дать (to give),
zirņi (pea) - зерно (grain,seed), pagrabs - погреб (cellar),
Pērkons (lettish pagan god, and a thunder) - Perunas (lithuanian so) - Перун (rus. pagan god, arhc. lightning),
saule - солнце (sun), tu - ты (thou), mes - мы (we),
šis, ši - сии (these),kad - когда (when),
nē - не/нет (no), viss - все (all),
divi - два (two),tris -  три (three),
četri - четыре(four),pieci - пять (five),
seši - шесть (six),septiņi - семь (seven),
mazs - малый (small),cilvēks - человек (human),
māte - мать (mother),zvērs - зверь (beast),
zobs - зуб (tooth),sirds - сердце (heart),
ēst - есть (to eat),domāt - думать (to think),
mirt - у-мирать (to die),iet - идти (to go),
pelni - пепел (ash), medus - мёд (the mead(honey)),
sāls - соль (salt), uguns - огонь (fire),
brālis - брат(brother), diens - день (day),
nakts - ночь (night), ziema - зима (winter),
draugs - друг (friend) ...
et cetera...

The consructions like Lettish "Es esmu ..." and archaic Russian "Аз есмь ...",
the great similarity of the Case System, etc.

Baltic Swodesh List
Comment: Those word lists without any comment don't form an answer to the question. To make a point for Balto-Slavic you should demonstrate some innovations that are common to Baltic and Slavic, but absent in Indo-Iranian, Celtic, Hellenic  or other branches of Indogermanic.
Comment: Even that needs some comments and not just bare word lists.
Comment: Reinstate Monica, the question was : "What are their common characteristics?"
Comment: what are you means ? it's the rhetorical question, i don't ask you really - "whether or not the vocabulary of languages (especcially about words comparable to the Swodesh List) such the common characteristic", since it's obvious and i'm not interested in the arguing about this.
Comment: *cilvēks* and *domāt* are borrowings.
Comment: Adam... :> Is it means - these "balts", which were invented as this "balts" by one German philologaster in XIX c. only, they didn't domat before ?... all these words, in the their great amount, are comparable to the Swodesh List... :>> Your words are just unsubstantiated - domat ? :> –  Пилум 28 mins ago
Comment: Only half of these examples are indicative, the other half is shared by all IE languages.
Comment: Anixx, this yours sentence is a kind of demagogy, because 1. many from others IE not so similar. 2. Well... And what ? IE-connection is the connection too. Japan, Suahili or Ojibwe are not IE, but the languages too, right ? :>
Comment: Also - in English example-translation here we can see - how is it all this... for example :>


midpoint theorem connections to midpoint formula

Question: Is there an elegant way to prove that the midpoint is $\left(\frac{x_1+y_1}{2},\frac{x_2+y_2}{2}\right)$ using non-right angled similar triangles? I know that it's really easy to just by assuming this is true and proving by showing the distance formula gives two equal sides.
Or is there some other way I can relate the midpoint formula to the midpoint theorem (the line segment connecting the midpoints of two sides of a triangle is parallel to the third side and is congruent to one half of the third side).
Comment: The midpoint of what, and what are $x_i,y_i$ ?
Comment: i think $$x_1,y_1$$ and $$x_2,y_2$$ are coordinates of two points
Comment: How do you want to use triangles to prove the above if you only have *two points*?
Answer: The formula for the midpoint of $A(x_1,y_1)$ and $B(x_2,y_2)$ is $$M\left(\frac{x_1+x_2}{2},\frac{y_1+y_2}{2}\right)$$
The simplest proof of this uses vectors.
$$\overrightarrow{OM}=\overrightarrow{OA}+\frac 12\overrightarrow{AB}=\overrightarrow{OA}+\frac 12\left(\overrightarrow{OB}-\overrightarrow{OA}\right)=\frac 12\left(\overrightarrow{OA}+\overrightarrow{OB}\right)$$
Answer: To add to David Quinn:
Consider a line in your diagram passing through the midpoint of AB running parallel to AC. Where does it intersect BC?


Out of the box Light Switch HTML app has a null error in IE9?

Question: I am trying LightSwitch for the first time, and after making a new HTML C# App - I tried to run it just to see what it looks like.  IE9 freezes immediately and I get this error from Visual Studio 2013:
Unhandled exception at line 5, column 19701 in http://localhost:49609/HTMLClient/Scripts/msls-2.5.1.min.js
0x800a138f - Microsoft JScript runtime error: Unable to get value of the property 'cultures': object is null or undefined
Does anyone know whats going on?  Thank you!
Answer: I found the issue - I am running Lightswitch in an offline environment and these two scripts were 404'ing:
http://ajax.aspnetcdn.com/ajax/4.0/1/MicrosoftAjax.js
http://ajax.aspnetcdn.com/ajax/globalize/0.1.1/globalize.min.js
Once saved in the solution I loaded fine.
Answer: This impacted me on VS 2015 all browsers. I think this is because of a closed environment for the server.
Lin M is basically correct:
Download the two files into the Scripts folder:
http://ajax.aspnetcdn.com/ajax/4.0/1/MicrosoftAjax.js http://ajax.aspnetcdn.com/ajax/globalize/0.1.1/globalize.min.js
Next:
In default.htm  change:

to: