Carrying a shield, but not using it

Question: Suppose an arcane caster is carrying a shield as part of a disguise. The wizard is not proficient with the shield and is just carrying it in one hand. If the wizard decides to not use the shield, would they still suffer from the negative on the attack roll just by having it in hand but not using it?
Comment: The real question is, why are you trying to make an attack roll as a wizard?
Comment: @Cyberson Because ranged touch attacks still require a touch roll, and at 1st level, every little bit helps.
Answer: In Pathfinder, shields have to be strapped to your arm to be considered worn, and can be carried in your hand without being worn.
In the real world, some shields are used by helding them by a handle, rather than wearing straps to support their weight.
The buckler, for instance, was hystorically held afar from your body, trying to meet your opponent's sword, while in patfinder it is strapped to your arm and leaves your hand free unlike all other shields.
So, helding a shield without wearing it is going to be extremely suspicious in the PF universe, at this point it would be equally good for your disgiuse to just carry it on your back, where it does not interfere with your attacks or initiative at all.
Comment: Actually, its only a naming mistake. What d&d, and pathfinder by consequence, calls a *Buckler* is actually a **Targe**.
Comment: @ShadowKras so D&D has no bucklers at all?
Comment: Visually, sure. Mechanically, there is no difference between a (real) buckler and a (d&d) light shield. Bucklers are represented on the art of several characters in the books, even the [iconic swashbuckler](http://paizo.com/image/content/PathfinderRPG/PZO1129_Swashbuckler.jpg) (PF) has one. But mechanically they dont occupy your hand.
Comment: Actually, on a second read. No, it doesnt have a version of our real world buckler. All shields have straps in Pathfinder. If anything, the closest thing would be the [Quickdraw Shield](http://www.d20pfsrd.com/equipment/Armor/quickdraw-shield): *This light steel shield is specially crafted with a series of straps
to allow a character proficient in shields to ready or stow it on
her back quickly and easily.*
Comment: What about [rondache](https://en.wikipedia.org/wiki/Rondache)?
Answer: I'd say the Shield would have to be equipped for your example. This means, regardless of if it's practical to do so, you are using the Shield, and therefore have the negatives associated with it. The only exception is if you can come up with some convoluted explanation for how it is being visibly held but not equipped without giving away the fact you are not who you claim to be... So, you're back to having it equipped. Just drop the Shield at the first chance you get, and you should be fine. If you want, tell your DM in advance that you're readying to drop the Shield the moment somebody seems to uncover your charade. The problem is, I can't think of where it actually says anything about this specific type of thing, but I am pretty sure that is because what you're describing is meant to be, in essence, "Equip".

Carrying a shield, but not using it


How do I create a factory_boy Factory that generates all fields automatically?

Question: I'm trying to migrate Django code from milkman to factory_boy.
Suppose I have a model:
class BlogPost(models.Model):
    title = models.CharField(max_length=200)
    content = models.TextField()
    number = models.IntegerField()

I write a factory:
import factory

class BlogPostFactory(factory.Factory):
    class Meta:
        model = BlogPost

However, factory_boy generates invalid values for these fields by default:
In [17]: bp = BlogPostFactory.build()

In [18]: print "title: %r content: %r number: %r" % (bp.title, bp.content, bp.number)
title: u'' content: u'' number: None

In [19]: bp.full_clean()
ValidationError: {'content': [u'This field cannot be blank.'], 'number': [u'This field cannot be null.'], 'title': [u'This field cannot be blank.']}

However, milkman can generate values for these fields automatically:
In [22]: bp = milkman.deliver(BlogPost)

In [23]: print "title: %r content: %r number: %r" % (bp.title, bp.content, bp.number)
title: 'A8pLAni9xSTY93QJzSi5yY8SGQikL7YGrcTZVViAFS72eqG2bLWHSh0lNLSA2FbH7kSCXDktCQxUO288HTXdYUcRNUikoH4LQ4QHmy6XRwrRzbbmwXL6pLW7tapJM3FTpx8oBbTUw7nCOZew73xjWsID666FKh05ychptiF2peEZHdQd6gnHqXtFkL5kyEIhFvinOCmS' content: 'RUcSHCxs' number: -709949545

I know that factory_boy provides fuzzy attributes, but you have to explicitly use them or use tons of model/field reflection.
Is it possible to create a Factory with factory_boy such that all fields are automatically populated with legal values?
Comment: Does this answer your question? [Can Factory Boy auto generate Django model field values like Model Mommy does?](https://stackoverflow.com/questions/35545424/can-factory-boy-auto-generate-django-model-field-values-like-model-mommy-does)
Answer: You can use the Extra Fields:
http://factoryboy.readthedocs.org/en/latest/orms.html#extra-fields


What is it like to be a Twitch chess streamer?

Question: I want to make a Twitch stream channel with my friend, and I want to know what the experience is like. Can explain it better to me or share their knowledge and experience?
Answer: First, it would be interesting to know what your goals with the channel will be. If it is to have enough revenue that it can become your job, you will need to offer something that others are not already offering, or do what they are doing a lot better. You need some kind of "angle".
For most chess channels, the angle is that they are Grandmasters, and since I looked you up on FIDE.com for another question previously, I know that you are far from that (I am not trying to be mean there). The other channels that are very popular by weak players also have something in common: Cute girls with good personalities. Alexandra Botez and Gold Dust Tori come to mind. Frankly, Tori is so weak, I could not imagine watching her although I have seen her for a few minutes here or there when a chess.com broadcast I was watching ended, and my channel was "raided" (users that are automatically transferred to another channel). Be prepared to change your approach after some time if you not getting any followers.
I am not saying that you cannot do it, but you will need to find something that makes you very unique. One idea for someone else might be: If you had been about half your age, like 6, it could have been to follow the little boy from novice through to Grandmaster, and grow with him. You are considering trying to stream with a partner. Partners seem to do well here (and on radio and television). A partner allow for more conversation, and for you to bounce things off each other.
Once you have your idea, then there is patience, and promotion. Assuming that you want to make money (if just for fun to have a channel, then all bets are off...just have fun), you would need to understand that it would be a job. You will need to spend many hours streaming for little, or no, money in the beginning until you have a following. Unlike YouTube, Twitch is more about live playing against various opponents, and you discussing what it going on for the audience.
Did I mention that it is a job? (Yes, I know I did.) You would need to take it seriously, and be consistent about your streaming, and that means probably every day, 7 days a week in the beginning. Famous streamers, like Hikaru Nakamura, can take stream as they like since people will show up when they show up (Naka puts his schedule on Twitter, for example).
Promotion. You will need to learn how to promote your channel via social media so people can find you among the multitude of channels. You will need to read books and websites from experts on how to do that. I do not know much about this, but you would need to find out how the system for "raids" works. That might be about building personal relationships, aka partnerships, so established channels are willing to let you take their audience when they are done.
It is a numbers game: You will need follower first, and then maybe they can turn into subscribers. Not all subscriptions cost money since Amazon owns Twitch, and they allow Prime members one free subscription per month. I usually back chess.com or Naka, personally with my Prime membership.
I wish you good luck if you try to do this.
"Tips for becoming a Twitch video game streamer"
Answer: For too many it feels like spewing streams into the void with nobody watching.
https://news.ycombinator.com/item?id=17541600
Just how many people are out there watching at all?
How many streamers are there?
So how does it feel to stream stuff into the great bit bucket of the cosmos?  That strictly depends on you and your psychological problems.
Personally I would feel stupid wasting my time doing it.
Twitch.tv is a video-game broadcasting and viewing platform where viewers can "donate" to their favorite players. ... Video game players broadcast themselves playing the game, usually with an audio commentary.
I would feel more stupid wasting my money on it.
Do I have to pay for twitch?
Select Subscribe | $4.99 to choose the default monthly subscription fee of $4.99 USD. Or, pick All Paid Tiers to choose the $9.99 or $24.99 payment option and see a list of perks for each subscription tier.Jul 1, 2019


Complex time theories with spacetime $\mathbb{R}^3\times\mathbb{C}$

Question: Are there any well-developed (string?..) theories assuming that, what we perceive as a (3+1) Minkowskian manifold, is a projection/compactification of a 5-dim spacetime, locally obtained via complexification of the usual time? And this additional imaginary time direction is also the one we use for Wick rotation in QFT
Answer: Complex time has been studied and has a name ("spacekime"). There's a whole group who study it, their web page is here. I'm not sure if they've looked at connections with QFT though, as I recall they've mostly done classical theories... but I've only briefly looked at their work, I may have missed something.


What is the correct usage of "sometimes" as a prefix?

Question: For example, if one might describe themselves as an "occasional writer;" or, identifies as a writer, yet only "writes occasionally." Would "sometimes-writer" be a more laconic way to express this?
Answer: This is a personal take on the question (nothing even remotely authoritative), but I think the three usages mean slightly different things.
I take a description of an individual as an "occasional writer" to mean that they undertake many actions or activities, one of which is writing. A manager of a department might have to write descriptions of accomplishments or proposals for future projects. They do not write "full time" but they do engage brief episodes of writing as a regular part of their duties.
I take a description of an individual as one who "writes occasionally" to mean that they are known to write but only infrequently. A board member might be called upon to write a grant proposal when the executive director is otherwise occupied. They do not write "full time" and when they do write, it is comparatively rare and typically of moderate duration.
I take a description of an individual as a "sometimes writer" to mean that they have written (more-or-less fulltime) in the past and that they might do that again in the future. A football player wrote a memoir a decade ago, published a sports-oriented novel two years ago, and talks about a follow-up memoir to be written in a year or two. They do not write all of the time but when they do write, it tends to consume most of their energy.
I value precision in writing and in word choice. If the context of the usage is a casual comment made by one character about another, then perhaps the word choice is less important. If the context is a narrative description of a major character, it is more important.
And, for the record, I have written occasionally, been an occasional writer, and have aspirations of being a sometimes writer.
Answer: I don't think 'sometimes writer' is correct.   The final S is the problem.   Compare 'once upon a time' with 'once upon a times'.  'Sometime writer' means at some time I have been/am a writer.
If there is no reason to ditch 'occasional' then I'd stick with that if that is an accurate description of bursts of creativity.


Is there a way to add the recipient_email field using the composer in Freeform

Question: Is there a way to add the recipient_email field using the composer in Freeform. We want the customer to be able to use the composer to edit a form and need to be able to send email notifications based on a dropdown selection field on the form.
Answer: I have done this in the past with JavaScript - dynamically selecting fields etc. This is some example of ways you could do it:
Dynamic recipients:
https://solspace.com/expressionengine/freeform/docs/form/#recipients
using JS
Getting Recipient Names/email address in Notification
Composers:
Freeform and Dynamic Email Recipients


Detect Mouse Enter on An oval shape image in unity

Question: I have an image that is attached to a panel and I want to detect On Pointer Enter and exit. The event is working fine but currently, it is working on the full image while I want to detect this event on an inner oval shape. Actual the remaing are of the image is transparent.
Answer: Assuming you have the bounding rectangle that wraps the ellipse. There is a transformation from that to a circle. You can create the transformation that maps that rectangle to a square.
You can use it to transform the position of the mouse pointer, and then check the distance to the center and compare with the radius (the same as the radius of the square you mapped to), and that will tell you if the mouse pointer is in the ellipse or not.

I have an implementation of an ellipse touch joystick in GDScript. The following is based on that.
We will need a rectangle defined in "global coordinates" (meaning the same coordinates of the mouse pointer). That rectangle is the rectangle that bounds the ellipse.
Let us say that:

size is a vector with the width and height of the rectangle.
position is a vector with the left and top of the rectangle.

We define offset as size * 0.5. And center as position + offset.
Then we convert from "global coordinates" to "local coordinates" (meaning coordinates with center = (0,0), and center + offset = (1,1), meaning that the rectangle goes from (-1,-1) to (1,1)) like this (GDScript):
func global_to_local(global_position: Vector2):
    return (global_position - center) / offset;

Once we have the "local coordinates", just checking the length of the vector will do.

This is my interpretation of global_to_local in C#:
Vector2 GlobalToLocal(Vector2 globalPosition)
{
    var diff = globalPosition - center;
    return new Vector2(diff.x / offset.x, diff.y / offset.y);
}

Check GlobalToLocal(mousePosition).magnitude <= 1.0f.

I suppose another way to go about it is GetComponent<Image>().sprite.texture.GetPixel(x,y).a > 0.0f. Which would be getting the pixel color and checking if it is not fully transparent. I don't know how to about the transformation to get the right coordinates to query the texture. I suppose it is similar to what I describe above, except mapped to the dimensions of the texture.
Mapping (-1,-1) to (0,0) and (1,1) to (w,h) is
return new Vector2((p.x + 1.0) * 0.5 * w, (p.y + 1.0) * 0.5 * h);

Thus, doing the transformation I described earlier (except for the rectangle of the panel instead of the rectangle of the ellipse) and then this transformation should give the coordinates for GetPixel.
Answer: By far the easiest solution would be setting the Image.alphaHitTestMinimumThreshold to anything other then 0. This is a property, so you can't set it in the inspector. Also note that you need to set the Sprite import settings correctly. In my test I had to set the following but there might be others, so if anyone finds any other that need to be set, please comment on this answer...

Read/write Enabled (Unity will throw an error if you don't do this)
Mesh type set to full rect (In my test it didn't follow the transparent edge correctly when set to tight)

Example code would be:
[RequireComponent(typeof(Image))]
public class Example : MonoBehaviour
{
    private void Start()
    {
        GetComponent<Image>().alphaHitTestMinimumThreshold = 0.5f;
    }
}

Where 0.5f is hardcoded in this example, but could ofcourse be set to your needs.
If you need a more sophisticated way of determining which parts are clickable and which parts aren't, you could also implement ICanvasRaycastFilter with your own custom logic.


Tablets and SSD degradation

Question: Does the iPad use any type of controller for drive wear leveling? It seems like Sandforce is the only player in the field.
Answer: Apple iPad does not use an SSD. It uses a flash based drive.
UPDATE: In response to the differences between SSD's and Flash Drives, here is the following excerpt explaining the difference.

'Flash Drives' are a generic term which used for anything from USB memory sticks to SSDs. An USB flash drive uses lower quality low performance NAND flash with just 1 or 2 channels. Its durable, cheap but slow. An SSD on the other hand uses high performance NAND with mutliple channels. ( 12 or 8 is not uncommon), and there is a  memory controller on a SSD which is much better and both can store data even if its not powered.
Flash drives (USB) are slow storage devices where as SSDs are high performance drives. They're much faster than normal HDDs.
A USB flash drive uses USB, which is generally a slower interface than the Serial ATA interface. A USB flash drive is generally thought of as a removable device by the OS and is managed as such. A SSD is treated similarly to a hard drive, and is often recognized by your OS as a type of fixed disk.
USB flash drives and solid-state drives are both based on flash memory. Most of the flash memory use  NAND memory, which are available as single-level cells (SLC) and multi-level cells (MLC). Single-level cells store a single bit in a single memory cell, whereas multi-level cells store more than a single bit in a single memory cell. The MLC accomplishes this by allowing each memory cell to store multiple electrical states, therefore, allow one MLC cell to store more information than one SLC cell. For example, a MLC that uses 4-levels can store 2 bits of information.  MLC are cheaper, as they can store more information per memory cell than SLC. Cheap, large SSDs and USB flash memory use MLC disks, although not necessarily. MLCs sounds great in terms of storage density, but it does have a catch. MLCs are  slower than SLC. Therefore, the large capacity USB flash drives and SSDs tend to be slower. Solid-State Drives (SSDs) have no moving parts, high reliability and longer life-span than traditional hard drives
Taken from here
Comment: @klutch2 An SSD is "8 - 12", and a flash drive uses "1 - 2"? What does that mean?
Comment: Flash [IS](http://en.wikipedia.org/wiki/Flash_memory) basically the same technology as SSD only the performance of SSD is higher and accordingly the price. @Brian Carlton has a more relevant answer to the question.
Comment: @klutch2 Just to clarify, I was quoting your ambiguous comment, not implying inches.
Comment: Solid State Drive is very different from a flash based drive. Learn to do your research before voting down. SSD uses more NAND than a normal flash drive (which is in the iPad), SSD is 8 - 12, while a flash drive (which is in the iPad) uses 1 - 2.
Comment: Also, check the iPad tech specs from the Apple web site. 16, 32, and 64 GB flash drive. Not SSD, if it was SSD it would be clearly labeled that way.
Comment: Not inches, NAND Flash Memory chips.
Comment: I'm not voting down but I do think this answer is not clear in making a distinction between the electrical/physical interface (eg USB or PCIe) versus the memory technology (eg NAND or flash, see: https://en.wikipedia.org/wiki/Flash_memory#Write_endurance). The term "SSD" doesn't imply either one of those options; it only refers to large amounts of non-volatile read-write memory that is not directly addressable by the CPU and acts like the non-volatile memory that used to be provided by a spinning disk.
Answer: This isn't a big concern since you will likely be writing to flash less than you would on a desktop.  Streaming video will go to DRAM.  I'm an electrical engineer who uses flash and I would be ok buying an iPad; I expect the battery will fail long before the flash.  Additionally when a sector goes bad, it will be skipped on future writes.
Answer: Whether Flash is used in an SSD (SATA interface) or just as a Flash memory hanging off any other internal bus, the Flash wearing out issues are the same. Unless Apple has done something in system software to minimize write cycles (caching schemes?) the wearing out risks are real and only Apple can explain how it is mitigating it. Yes, SandForce controller is the only one that claims Write cycle reduction and thus extend the Flash endurance by minimizing the write cycles.

Tablets and SSD degradation


Can someone launch a DOS attack on my IP

Question: Suppose, I have a static IP on my PC and is known to others. None of my softwares listen for remote connection. Is it still possible for someone to DOS attack me in such cases? If yes, how it is possible?
Answer: Sure, that's possible. For a very simple denial of service attack, an attacker just floods the downlink of your internet connection with garbage, thereby preventing any real incoming data from arriving at your computer.
Comment: @VarunAgw There are only two real protections against this: Either keep your IP secret (e.g. using Cloudflare for servers) or have more downlink bandwidth than what the attacker can send you.
Comment: Sure, anyone can send you as many packets as he wants, no matter whether you're running a server or not. I'm unable to find a link to an article about this though, sorry.
Comment: Any clue where I can read more about this specially protecting from it
Comment: Sorry, Actually I don't understood your answer. That's why I asked for link. Can anyone flood my downlink even if I don't have any HTTP server installed? Also, I am talking about a personal computer with limited bandwidth and speed and not a web server
Comment: @thejh I think the link you're looking for is [Ping (networking_utility)](https://en.wikipedia.org/wiki/Ping_(networking_utility))
Answer: DDoS is not specific to HTTP or any service, a Distributed Denial of Service simply means that are multiples sources for the attacker trying to make it so your network connection is non functional.
A denial of service could happen by making your system crash or become unresponsive (if its not on, it won't respond),  by filling up all your bandwidth (your pipe), or most simply by physically severing the connection. Distributed denial of services attacks can be started by using multiple clients the attacker controls or by tricking innocent clients to participate.
Refer to the OSI Model or the TCP Layers. HTTP is going to be at the application layer, but you can attack at any layer to cause denial of service.

A very simple example of a lower level DDoS attack, would be the smurf attack. In this attack you take advantage of a broadcast message to all stations on network responding to the spoofed source target, which is the victim.
A similar attack, is the DNS amplification attack, where you trick a bunch of DNS servers into giving unsolicited responses to the victim.
Alternatively, if the attacker controls a botnet they can just send any type of unsolicited traffic and clog up your pipe or clog up your workstation with requests, pings, etc.
Answer: Yes.  At a bare minimum, they can perform a simple ping flood or UDP flood attack, where the attacker sends data at a high rate of speed, without worrying about whether or not your computer has a program listening for that data.
Answer: If you are not running any kind of server, your computer and router firewall will reject incoming connections, but this does NOT protect you against a denial of service attack. The reason for this is that by the time the packet reaches your router and your router blocks it, it's already too late - the packet has already essentially reached you and has consumed some of your bandwidth. In other words, the attacker literally does not have to care whether the DoS traffic is being accepted or rejected; as long as the attacker is sending packets at a higher rate than what your connection can accept, your downlink will be saturated.


How do I make a spider farm in my kitchen to eat flies in the house?

Question: I am planning on making an area set aside in the kitchen to breed and grow spiders to kill flies in the kitchen. This is completely theoretical right now, just something I am pondering, so I don't really have all the details fleshed out. What I am planning to do is to make this triangular box so that it will fit in the corner of the kitchen. Then, I will coat the bottom of the box with whatever flies are attracted to (I think it was vinegar?). Finally, I'll need to get some spiders, I probably have a couple of them crawling around the house. However, I am not sure what to use as the lid of the spider farm so that no spiders or baby spiders will escape while also letting flies and vinegar get in. Any ideas? Also, do you think my spider farm idea is effective for getting rid of flies or as stupid as it sounds?
Comment: I'm voting to close this question because it's not about home improvement.
Comment: Get some Venus fly traps :)
Comment: This seems like an animal-husbandry and insect/arachnid behavior question, not a Home Improvement question.
Comment: Politely, this is not an improvement to a home.  Finding and remediating the source of what attracts the flies would be a better solution.   Consider relocating sources of smell, like trash cans.
Answer: I'm not an entomologist, but...this isn't going to work. My non-expert intuition here is that spiders don't want to live in a box, and they especially don't want to live with other spiders in a box. Also, if you're going to the trouble of luring flies into a box, maybe just put some fly paper in there? Sometimes simpler is better.
P.S. The expression is "you catch more flies with honey than with vinegar," but actual non-metaphorical flies seem pretty crazy about dog poop, so I don't think they're too fussy.
P.P.S. Please don't put dog poop in your spider farm.
Answer: The idea is fine.   But you can't chicken out.   As long as you get enough spiders and let them cover a good deal of your kitchen in webs, the flies will be gone in no time.  You really have to go all in on this and not sure how sanitary that is for a kitchen.   But you have to continue having a small fly problem or the spiders could turn on each other.
Or you can just keep your doors closed and be careful about the produce you bring in the home and how you store it.    I don't get the "fly problem" unless you live really close to others and they are causing the issue.   You should figure out why flies are getting into your home and stop doing those things if you want it to stop.   Yes I have had flies in many houses.   And no there was never a house that stumped me on why flies where a problem.   This is not like other bugs that are sneaky.   Flies a very robotic and are produced and travel in very "programable" patterns.


Implementation of the NServiceBus/MassTransit IContainer with DryIoc or LightInject

Question: I had used DryIoc and LightInject in most of my .Net Web API 2+ solutions. Using new architecture, I would prefer to use NServiceBus or MassTransit for my next ESB implementation. However, I could not find any useful code reference that could help me to do Implementation of the NServiceBus/MassTransit IContainer with DryIoc or LightInject. Other IoC is not an option for me as the requirement from my company is to choose only from both of the above mentioned. Greatly appreciate any help from the community.
Answer: Will this help? "If you have your own container that is not already supported by a NuGet package, you can create a plugin centering around the IContainer abstraction. Once this is created and registered, NServiceBus will use your custom container to look up its own dependencies."
Comment: Sean, thanks. I had made my decision to use [rebus 2](https://github.com/rebus-org/Rebus), as it has the container adapter for light inject. At least the performance is close to DryIoc. I had came across the link that you gave me. Still I found that it is not helpful. They should demonstrate further as the element of using container is very important on the implementation their ESB framework.


How to add a VFR map coordinate grid in QGIS?

Question: I want to add a coordinate grid like in the link below to my map. A simple grid is no problem, but I would like to know how to add the fragmentation of the lines.
Comment: By 'fragmentation' I assume you mean the tic(k)-marks along the grid lines? I'm not sure this would be possible *as* a graticule. Maybe if you could change the linetype and customize tick spacing and such. You can potentially overlay multiple graticules, but then you get them out in the middle too. It might only be possible by creating a custom vector grid layer(s).
Answer: For the ticking mentioned by Chris W, you can use the Station Lines Plugin:

Note that the Station lines layers are memory layers. You have to save them to disk into another format to use them again.


What does "transfer" of angular momentum mean?

Question: The Moon's gravity produces tidal deformations or "bulges" in the Earth. Because of the Earth's rotation, the line that goes through the bulges is not aligned with the line between the Earth and the Moon. This misalignment produces a torque that transfers angular momentum . I am not clear how the transfer of angular momentum occurs
Comment: It's the same thing as transferring regular momentum, which is what happens whenever you push on something. Here, the Moon just pulls on the tidal bulges to make the torque.
Comment: In the same way that the gravitational force between two objects transfers linear momentum between them.
Answer: The angular momentum is conserved in central force motion (like what we have in the case of Earth-Moon system). In such a case, the force $\vec{F}$ and the radius vector $\vec{r}$ are parallel so that the resultant torque is zero
$$\vec{\tau}=\vec{r}\times\vec{F}=o$$
This means the angular momentum ($\vec{L}$) of the of the Moon about the center is a constant (since $\displaystyle{\vec{\tau}=\frac{d\vec{L}}{dt}}$). Hence the moon while orbiting earth conserves it's angular momentum. The angular momentum is given by
$$\vec{L}=\vec{r}\times\vec{p}$$
This means, to conserve the angular momentum the moon exchange the distance and velocity as they move about Earth. The Earth's angular momentum is distributed between it's spin (rotation) and it's motion along the orbit (revolution). Hence to keep the angular momentum conserved, the spin and orbital angular momentum of earth is exchanged by several mechanisms. The moon could exert tidal forces on Earth. This acceleration causes a gradual recession of Moon in a prograde orbit away from Earth (direction of motion same as rotation of Earth). How the tidal forces of moon are exerted on earth, you can see here. To conserve the angular momentum, the Earth have to manage to counteract the tidal torque on it.
The extra torque acts in the direction of the angular momentum of earth due to the spin of Earth. So, to nullify this additional torque to zero the Earth's rotation slow down and cause a gradual increase in the Moon's orbit. This is how angular momentum is exchanged in between the Earth-Moon system by exchanging the radius and velocities.
Comment: How does slowing  down of earth's rotation increase moon's orbit ?
Comment: When earth slows down, it creates an additional torque in the opposite direction so that it cancels the additional torque. i.e., in effect the earth add some torque on moon in the reverse direction of what the moon applied to earth. So the effective torque exerted by moon now decrease. To avoid that and to conserve momentum, the moon increase it's orbit so as to retain the torque.
Answer: It's worth thinking about why the tidal bulges1 are not lined up with the line between the bodies (which is where you would naively expect them to) and then thinking about how that affects the gravitational interaction between them.
Because the moon takes about one month to orbit and the Earth takes one day to turn, the naive location of the tidal bulges should move east-to-west across the surface of the Earth in order to stay on the line between the bodies. However, that would represent an actual flow of water and the water in motion interacts with the ocean beds and shores. The net results is a frictive force between ground and water that (on average2) retards the motion of the water and causes the bulges to be east of the line between the bodies.
Finally, the bulges (which on average leading the Moon around the Earth) represent an aspherical component of the Earth's mass distribution and their gravitational effect on the moon can't be reduced to a point-mass approximation. The near bulge leads the moon pulling it slightly forward. The far bulge trails and pulls slightly backward, but it is farther away so it's effect is smaller. The net result is that the moon is pulled forward in its orbit and the Earth is slowed.
It is the usual contrariness of orbital mechanics that turns a steady forward force on the moon into a combination of outward motion and reduced speed.3

1 It's possible also worth mentioning that the real tidal bulges are not the same as the idealized one often presented in a first treatment of this subject because the oceans are not deep enough to treat the bulges as free moving surface waves.
2 In addition to friction the bulk motion can excite resonant modes in the ocean basis, and cause the phase angle between the actual location of the excess water and the line between the bodies to either lead of trail. With the right arrangement of continents the process can actually run backward.
3 This has been treated several times in accessible language in science fiction. Heinlein did a nice job in The Cat Who Walks Through Walls, but I think the pithest version comes from The Integral Trees:

"East takes you out, out takes you west, west takes you in, and in takes you east." --Larry Niven


Grid tie inverters and islanding

Question: How do modern grid-tie invertes which are commonly found in solar pv panels and wind turbines actually stop islanding from occurring when the utility grid is down? I know there are a lot of methods which are used to prevent islanding but which method is the most common?
Answer: Answer from a non-electronics person who's been reading up on this over the last few days. Depends on standards and things (VDE-AR-N 4105 being a common one), but here is a non-exhaustive list:

Voltage change
Frequency Change
Rate of Change of Frequency (RoCoF, dF/dt)
Vector shift

Most of them makes intuitive sense I think, at least if your generator is mechanical in nature. A change in load usually causes your engine/power source to slow down, causing a drop in voltage, a change in frequency, and a vector shift. The vector shift is when a momentary slow-down causes a cycle to take sligthy longer than the previous cycle, so for example on a 50hz grid where a cycle is supposed to take 0.02 seconds, it might take 0.22 seconds for just two cycles before returning to normal, but that might be enough of an indication that islanding has occured.
Answer: They use anti-islanding measure with the help of phase locked loop(PLL) to detect the frequency of the grid.In case of absence of grid the PLL output sensed that is passes through a phase detector and then compared to a dc offset allows the system to acknowledge the absence of grid.

Grid tie inverters and islanding


T&P valve is really tight, not able to remove it

Question: I have the below T&P valve, I'm not able to remove it to replace a new one.
I saw there has some declaration above the valve which said it's the combination of the water heater, does this mean I can't remove it? If no, how to remove a very tight valve. Thanks a lot.
Answer: OK, that warning label is telling you that the valve is protecting the appliance from both over-heating and over-pressure (combination). The part about removal from point of installation is a warning that relocating it to another part of the system will not provide adequate protection (back in the day they sometimes located a pressure-relief valve on a pipe outside the home). You can remove and replace it. Pull off that plastic cover so you can see the threaded part. Get a bigger wrench, at the factory they use a pipe compound that sets hard. Your tank is iron and unlikely to be damaged
Comment: My tank is more than 10 years old, I worried about will break the screw there, then not able to tighten the new one properly. I already got a 14inch pipe wrench but doesn't work, so you think I need a bigger one like 18, 24 inch. besides, the cover not able to peel off as new picture attached. @Jimmy Fix-it
Comment: I have attached a pic for comparison between the old and new PRV, do you think that work?
Comment: It absolutely *will* work, if it has the same temp. and pressure ratings (your old one is 150 p.s.i. and 210°F). The pic does not reveal the rating of the new one.
Comment: how about a longer neck than those two above, I mean the one has a shorter exposed length of the probe, is this matter? Attached a pic for the that one. @Jimmy Fix-it
Comment: No, probe length relates to function. Even if it had the same temp. rating the location of the probe in the tank would be different. Use the one with the probe position closest to the original. Why are you proposing to use the "long-neck" one?
Answer: First, try to tighten the relief valve to break the hold of the dope and threads. It should be easier to tighten than to remove. You only have to move it a little to break the thread hold . Then remove the safety valve with a bigger wrench, say an 18" or 24" crescent wrench. The tightening is easier since the strain on the threads is in the direction of tightening.
Answer: If the TP valve is bad, you have to replace it, even if it's risks damage to the threads. I had the same problem and borrowed a long pipe wrench to get it off. You can try to break it free a few ways:

Use a longer wrench or put a pipe over the handle to make your lever longer
Rock it tighter and looser to get the threads moving
While the tank is hot, drain below the valve and apply ice water or dusting spray to the valve to try to change the size to loosen
Use a penetrating oil or something like CLR (you should be able to pull back the plastic cover to get to the threads)

Try to use even force to try to keep from tearing the threads.
If it does tear out the threads you may need to clean them out or even repair the threads with a tap.


Helping a child with selective mutism

Question: I am a first grade teacher to a selectively mute girl, age 6.  She has been in my class since August 2014 and will not speak to any adults at school.  Occasionally she will whisper to me, but usually only nods as a response.  She will speak to kids in the class at recess.  At times, she seems terrified and chews on her fingers when she is nervous.  She also moves robotically through the school, shuffling around slowly and making no eye contact.  How can I help her?
Comment: Have you discussed the issue with her parents? What was their response?
Comment: How familiar are you with Selective Mutism?
Answer: I pulled the following advice from "What is Selective Mutism?" -- while the advice is directed at parents, it would at least be a start. Not pressuring her to speak seems to be the focus, since it's related to anxiety and therefore drawing attention to the issue will simply make her more nervous.

The main goals of treatment should be to lower anxiety, increase
  self-esteem and increase social confidence and communication.

Don't focus on the fact that she isn't speaking and look for ways to help her communicate non-verbally. Praise her work as you would any student, focusing on what she is able to accomplish in order to boost her confidence levels.
Bringing the issue up (non-judgementally) with her parents is going to be really important for long-term success, though. You'll only have her as a student for a few more months, and hopefully they will be able to establish a plan to help her throughout her school career. Not all her future teachers are guaranteed to be as understanding.

Helping a child with selective mutism


What is Object storage really?

Question: I searched about object storage a lot, all the articles say the same thing. Object storage is a data storage architecture that manages data as objects, it includes the data itself, and a variable amount of metadata.
Object storage is the future of how data being stored.
But how does a object store in a disk. Or it's just an idea, I can use a file storage along with a MySQL to store the metadata, and claim it is a object storage. Or if it is compatible with the AWS S3, it's an object storage system.
I am very confused about this idea, or it's just another fancy word like ajax.
Answer: This post sums it up fairly well - https://www.druva.com/blog/object-storage-versus-block-storage-understanding-technology-differences/
Typical differences you'll see between object storage and traditional file systems/block stores are -

slower response from object stores due to network latency
object stores don't implement file hierarchies although S3, for example, mimics a file hierarchy in the AWS Console
object stores are typically eventually consistent where block stores provide strong/immediate consistency

In the case of S3, each object/file is created with an object key. This allows you to mimic a file system hierarchy and is helpful for uses such as embedding metadata in the key name. This is also beneficial for use cases such as using S3 in place of HDFS with Hadoop based systems. Additionally, S3 allows you to tag objects with key value pairs similar to other AWS services.
Comment: thank you for your reply.I still don't get it. I can use a ftp or http server to do the same thing just like S3 does.It has metadata,just being stored in the database,You give me a id,I'll find the meatadata and the path to the ftp.
Comment: ceph stores the data as blocks and claim it is a object storage.
Answer: I completely understand your confusion.
Imagine a bowl. Into the bowl, you put differently-sized balls that are uniquely labeled. The balls would fall into the bowl without any structure, and they are only differentiable by their unique labels.
You can think of object storage systems like that. Each ball in the bowl represents one piece of data such as video, audio, text, email, etc. The size of the ball corresponds to the file size. Each object (i. e., file) is given a unique global 128-bit identifier in object storage, so the ball's label is its identifier.
You can think of the bowl itself as the object storage provider. Nowadays, it is mainly AWS S3 buckets that use such organizational schema.
I have also read through your comments. You suggest storing the file itself in file storage and storing the metadata in a database table.
However, object storage systems came into existence solely to avoid such operations as storing data into tables. You see, to store anything in a table, you need a cleverly-designed database schema that makes data retrieval easier for future operations. All these extra details and requirements for storing data into tables are cost-heavy and entirely unnecessary for people who just want to store their files somewhere without thinking about structure.

What is Object storage really?


Withdrawal of coins to Trezor did not happen, Where are my coins?

Question: I set-up Trezor yesterday and withdrew coins from my exchange to store in the Trezor. I entered the address and conifrmed.
However, an hour later, Trezor said Network error. It was unable to receive the coins.
The address I entered is also not showing up on Trezor today.
How do I get my coins?
Answer: If you used the correct address, you have received that money already even if your Trezor doesn't yet know about them.
If the public blockchain (not the unrelated business who use that name) shows your address has the money, you already have it. The public blockchain is the only true record.
You won't be able to spend that money until you fix whatever problem is causing that reported network error (or until you use your safe backup copy of the seed phrase or private-key in another wallet)


How to discourage subordinates from unnecessarily interrupting their manager?

Question: This is a habit that tends to form in some people (admittedly including myself), when seated near a manager:  the subordinate tends to ask the manager questions all day, often about very trivial things.  Often the answer is very basic ("just refresh the browser", "try closing everything and open it again")
The interruptions are significantly detrimental to the manager's performance, and affect concentration.  However, we don't want to discourage the subordinate from asking questions when they get stuck, because otherwise they may sit around being unproductive, or make mistakes that are costly to fix.
(This is assuming that picking up a laptop and moving to to a quieter place is not an option)
What is an effective strategy to handle this?
Comment: Joe's comment is 100% valid, your role in this is pretty vital in terms of an accurate useful answer.  And for the record, people can down vote a question **without providing a reason**, and that is ok.  Name calling will *not be tolerated*.
Comment: Are you a manager who is experiencing this issue?
Answer: If the subordinates are asking questions which can really be answered with a "refresh your browser", it looks like either they are looking for micromanagement or just to look like they are doing something.
You don't mention where this is based, so I cannot tell if it's part of the local culture to have this sort of interaction.
In my own experience the most effective way for reducing the amount of superfluous questions is to simply bounce them back:"how would you do it?" or "what have you thought of?".
On one side this will train the asker to think beforehand about the problem, and very likely avoid asking self answered questions. On the other side it will help the manager to guide the asker in following the "right" mental path for problem solving.
Comment: @JoeStrazzere Whoever receives the question. I have seen this technique used by both managers and colleagues.
Answer: How often does the manager provide employee feedback?  If it is only tied to the end of year review, you need to increase it.  Perhaps even weekly.
Have the manager then raise the point in the setting which was designed for providing this kind of feedback.  The conversation should look like:

Stephen, I appreciate how you are willing to come to me to point out
major issues and seek support; but, I'd like you to become a little
more independent.  I want feedback on any issue that I need to take
action on; but, if the request is about a problem you might be able to
figure out in five minutes, I'd appreciate it if you took those five
minutes to try to find a solution.  If it is a bigger problem, or one
that can only be solved by management, please bring it to my
attention; but, please hold back on the very small items so I have
time to my job as a manager, which benefits the whole team.  I don't
expect you to change overnight; but, I will be paying more attention
to interruptions, and providing your more feedback in the future, so
this can be addressed before any end-of-year employee review.  I don't
want to surprise you with feedback that's too late for you to do
something about it.

If you're not providing this kind of feedback at least once a month, then you're probably only managing up; which is valuable, but unlikely to fix any managing down kind of issues.


All of my shortcuts open same program

Question: My Shortcuts on Windows7 was just opening VLC, and I right-clicked one of them to change the default program and it eventually opened. But because I chose for it to always open in the default program, all shortcuts did the same - they opened that same application.
Apparently I had associated shortcuts to that application. How do I re-associate shortcuts to act as a shortcut to their own applications?
Please help me understand the way shortcuts work in other to rectify the problem.
Thanks.
Niyimagic
Answer:
start (click)
search programs (click)
Regedit (you need to write this and open it)
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.lnk
(you need to find these sub-folder by clicking through the keys)
UserChoice (you need to find and delete this folder that's the
problem that you made)
Close and restart windows
Comment: using win-r then regedit would be an easier way to get to regedit. I do suspect you can search registry as well.
Comment: I know this post is old, but just used it to solve my problem. Thank you for your answer.
Comment: in my case regedit and all other exe files didnt run by explorer so i write answer below for this case
Answer: Well, in order to try and recreate your problem, I was sitting here with the same problem without any clue how to fix it.
When you try to change the file type association again, there is no option to revert to the original state.
How I fixed it eventually is through the use of this website:
http://www.sevenforums.com/tutorials/19449-default-file-type-associations-restore.html
There is a howto on the site itself, but the procedure is very simple. Look for the link to LNK filetype on the page, download the zip which include a .reg file. Open that .reg file, agree to the security message and after it is done, log off and on and the .lnk file type will be reassociated to its original state.
Answer: Right click any file again and choose Open With > Choose default program...

Select the program, and choose Always use the selected program to open this kind of file
Comment: I think he associated program shortcut files with a particular application. Which is useless, no matter what application you choose.
Answer: Head over to Control Panel\All Control Panel Items\Default Programs\Set Default Programs
Then you can choose each application and set their defaults back
Answer: in my case all exe files also cant opened by explorer
so regedit.exe didnt run as well
so only way that solve problem is create new user (as administrator)  and move all documents there.

All of my shortcuts open same program


Cucumber-jvm - Retrieving embedded image from TestCaseFinished event

Question: I have a cucumber plugin where I post my test case results to TestRail using the TestCaseFinished event. It works so far, but on failed steps, I use the scenario.embed method to add a screenshot of the failed step. The TestCaseFinished event does not contain this (or the scenario.write method)
Is there any way to retrieve this information using a cucumber plugin? I considered, during the @After hook, when taking the screenshot, to save the image temporarily in the target directory but this seems like a long drawn out process, when it seems like it should be available in the event. If not, any particular reason why it isn't included?
Answer: You can subscribe to EmbedEvent to get all embeddings. The event also has a reference to the current test case.


Power Point 2007 won't automatically advance to linked presentation

Question: I'm using PPt 2007.  I've successfully linked 3 PPt presentations; however, I can't advance from the last slide in, for example, presentation #1 unless I click.  I would like PPt to simply advance from the last slide on the 1st presentation to the 1st slide on the 2nd presentation and continue on.
Answer: Unfortunately, that's the nature of links ... you have to click them to activate them.
Is there some reason you can't combine both presentations into one?


Do browsers count requests from different subdomains as different hostnames?

Question: According to this message in the AWS forums, I should serve my static assets from different hostnames because I can achieve more parallel downloads with the client's browser, do I need a totally different TLD, or will unique subdomains (like: static1.example.com, static2.example.com) work?
Answer: Separate hostnames within one TLD will work, and is the traditional approach.
That said, there's a good reason to use a different TLD: cookies.  If you're serving user-supplied files, you definitely want a different TLD with no access to the sign-in cookies.
Even for trusted content, if you have cookies over a domain .example.com, then avoiding serving the images/whatever from inside .example.com leads to lighter requests and responses.  How much this matters depends upon how carefully you're tuning performance to keep overheads small and how bloated your set of all cookies is.
Answer: The trade off is between parallel requests and additional DNS requests, note many modern browsers have upped the limit from 2 to 6 or so.
http://developer.yahoo.com/performance/rules.html#dns_lookups


When using campden tablets to dechlorinate water, how much sulfite makes it into the final beer?

Question: I have a friend who is allergic to sulfites in wine, so he sticks to drinking beer.  I use campden tablets to dechlorinate my water, at a rate of one tablet per 10 gallons.  How much sulfite makes it into the final beer when treating water this way?  How does it compare to sulfite levels in wine?
Comment: Unless you use lab equipment and do a titration, you are always going to have either leftover sulfite (if you use too much) or leftover chlorine (not enough). You can however use Vitamin C (ascorbic acid) instead to remove chlorine. That is what is in part 2 of travel water sterilizer tablet kits (part one is a chlorine or iodine tablet)
Comment: You should be able to get a water quality report from your water utility. It should tell you how much chlorine or chloramine is in your supply. 1 tablet for 10 gallons is twice as much as would be needed for my tap water which has 4 ppm chloramine. So none of the off-gassing methods describe below would be effective. The chlorine that is evolved from the metabisulfite should be effectively removed in the boil.
Answer: Using campden is less expensive, faster, and more effective than using a filter.  Basically, there is no sulfite left.  According to BYO "The reaction converts chlorine into chloride and the sulfite is converted to sulfate."  (http://www.byo.com/stories/wizard/article/section/121-mr-wizard/475-clearing-chloramine-a-historical-hopping-mr-wizard).
Comment: That article does not seem to say that no sulfite remains, just that the amount that does react with chlorine compounds in the water will be converted into harmless chemicals.  This may or may not be all of the sulfite that you added to the water, it seems to me.
Comment: I think it says (maybe it was another article I read) that used at the recommended rate, all sulfite is converted.
Comment: Not true in terms of effectiveness of campden v filtering. I know this from my own analytical chemistry experiments. Faster, yes, if he were using it at the standard (.44 g per gallon) rate. He is using it at a much lower rate than the standard brewing rate, understandable because he is just using it to remove chlorine/chloroxides, so the article you link to doesn't really apply to his question.
Comment: The chemistry involved is that the bisulfite reacts with the chloramine to produce ammonium (Mr Wizard mentions this), sulfate (also mentioned by Mr Wizard) and chlorine gas, not chlorides. The reason some people boil the treated water (Mr Wizard mentions this) is to drive off the dissolved chlorine gas. So campden isn't really faster either. And there is always some remaining sulfite, but that is irrelevant (as I mention in my answer) because the original concentration is lower than what is allowed for "sulfite-free" wine.
Answer: That would be hard to know accurately.  A better way to remove the chlorine would be to use a Brita or Pur filter (an activated carbon filtering system), or expose the water in a colorless carboy or container to intense light for several hours with the top open to allow the chlorine to escape (this is a common way to allow the chlorine to escape when prepping for fish tanks). These do not add sulfur compounds.
At the rate that you are using the campden, the sulfite levels would be less than the typical ppm in wine. Before the metabisulfite reacts with the chlorine and chloramine, the concentration would be about 7 parts per million (using standard .44 g tablets). Sulfite levels of less than 10 ppm in wine are allowed for a wine to be called sulfite free ( see http://wineintro.com/glossary/s/sulfites.html). So even if none of the campden reacted, at the rate that you are adding it, the concentration would be below that accepted as "sulfite-free" in wine.
I use a brita filter and have experimentally determined that chlorine and other contaminants are reduced to sub part per million levels. BTW - the same filters also remove sulfite and sulfates. Be certain to use a relatively fresh filter.


Install Windows XP over elementary?

Question: It's a good os however runs slower than windows 10 on my low-end computer. How do I change the os back to Windows? I have a USB stick and it isn't being read on elementary (it is working properly on my laptop)thanks in advance.
Answer: There is currently no way to do a change back/rollback to Windows XP, or any previous Operating System that you had before the install.
If you have a Windows (XP, or any other version of Windows) installation disk, then you could use it to install Windows on your computer. As far as drivers go, I wish you good luck.
A better option, is that you have a backup of your previous system. (This includes the entire disk.) Then you could restore the previous system from the back up.
Wish you good luck.
Comment: When I see "XP" in a post involving Windows it rears a number of concerns. Chiefly among those is the security vulnerabilities that are opened up by using an OS that went end of life almost four years ago. That, along with the financial implication of buying a newer Windows version (which could cause the same issue on a lower spec machine) would cause me to look at a "lighter" Linux distro. An unprotected, outdated OS could spell certain disaster in the end.

Install Windows XP over elementary?


What exactly is a solubility product, and what is its use?

Question: What exactly is a solubility product, and what is its use?
I've come across this term while reading, and don't have access to anyone who can help me understand this concept.
Answer: If we take small particles of a sparingly soluble salt, say AgCl, then one or two particles may dissolve in water and a saturated solution is obtained pretty soon. Upon adding extra AgCl to the solution precipitation of AgCl starts. At this stage, you'll find an equilibrium is established between the dissolved and the undissolved AgCl.
$$\ce{AgCl(s) <=> Ag+ (aq.) + Cl- (aq.)}$$
And for this equilibrium if you're to find the equilibrium constant, let's call it  $K_{sp}$, you get:
$$ \ce{K_{sp} = [Ag+] \cdot [Cl-]} $$
(Both the concentrations are the ones taken at equilibrium.)
This $K_{sp}$ is called solubility product. It's useful to predict whether or not more solute can be dissolved in your solution or not. We do this by comparing it to something which is called the ionic product.
Comment: I think that a sentence about the meaning of 'saturated solution ' can be useful
Answer: The solubility product is an equilibrium constant for the dissolution of a sparingly soluble but highly ionised electrolyte. It does not apply in principle to strong soluble electrolytes or to compounds that exist in an unionised state in solution, such as $\ce{HgCl2}$.
In a  reaction such as
$$\ce{AgCl <=>Ag^+ + Cl^-}$$
which must have reached equilibrium, which means that  some solid is present together with the solution (and so the solution is saturated), the solubility product is
$$\ce{[Ag^+][Cl^-]=}K_s $$
In the general case $\ce{A_nB_M <=> nA + mB }$ then $\ce{[A]^n[B]^m=}K_s$
(The thermodynamic derivation of $K_s$ depends on using activities which may be replaced by concentration when the concentration is low as it is in the case of sparingly soluble / insoluble salts)
The solubility product illustrates a quantitative application of Le Chatelier's principle. If, for example, the concentration of $\ce{Cl^-}$ is increased by adding sodium chloride some AgCl  is precipitated until equilibrium is re-established, i.e. $\ce{[Ag^+]}$ is reduced until $\ce{[Ag^+][Cl^-]=$K_s$} $. Similarly if $\ce{[Ag^+]}$ in solution is reduced by forming a soluble complex, such as by adding ammonia, then more $\ce{Cl-}$  will be produced as more solid AgCl dissolves until equilibrium is established.
The solubility product $K_s$ can be used to calculate the concentration of an ion in solution and hence its total amount in a solution. In the case where there is a common ion it can be used to determine how solubility varies with common ion concentration. Thus it can be used to answer questions such as 'How much $\ce{Ag^+}$ is there in 100 ml of a solution of 0.1 M potassium chromate  saturated with silver chromate'.


What percentage of my stock portfolio should be international (non-US) stocks?

Question: I recently read that, based on capitalization, US stocks no longer make up the majority and that to be diversified would mean to hold 50% or more in non-US stocks.  Is this good advice?
Comment: Depends if you plan to retire inside or outside the US :)
Comment: Does it though?  The end goal is to grow and maintain buying potential, no matter where I plan to retire.  For example, you wouldn't want to be 80% invested in a country when it suffers a financial collapse.
Answer: Rephrasing your question: Am I diversified if I have more than 50% US stocks?
I would say that you can certainly be diversified and have more than 50% of your portfolio invested in US Stocks.  I view the amount of international stocks (non-US) as a risk choice.  My observations have been that my international stocks have higher risk which comes with a higher reward.   I'm not comfortable with putting too much of my portfolio into a very high risk category.
I personally invest 25% directly in mutual funds that invest in foreign stocks.   When you couple that with the money I invest in US stocks via mutual funds that have foreign interests (Coke, GE, etc.), I'm somewhat over 25% international in my portfolio.
Answer: Without knowing anything else about you, I'd say I need more information.
If all of your investments are in stocks, then that's not really diversified, regardless of how many stocks you own.  There are other things to invest in besides stocks (and bonds, for that matter).
What countries?  "International" is pretty broad, and some countries are better bets than others at the moment.
If you're old, I'd say very little of your money should be in stocks anyway.
I'd also seek financial advice that is tailored to your goals, sophistication, etc.
Comment: I'm interested in focusing in on just the stock holdings in a portfolio, no matter what percentage of the overall portfolio they represent.

As for which countries, basically I'm interested in discussing the concept of weighting countries by their fraction of global capitalization.  Something of a global index, if you will.


Darlington transistor for driving coils

Question: I try to drive two small pcb coils. The coils have a resistance of around 14 Ohms (i dont know the L value). I have a PIC10F200 controlling the base of a BCV27. However i dont seem to get much more than 0.1V across the coils.
Did i make a mistake, or is there something fundamentally wrong with my approach?
Thanks!!
Comment: Probably something fundamentally wrong but, you haven't stated what your aim is.
Comment: What is your VDD voltage, and does it stay steady when you turn Q1 on?  Your diode should be from the collector to VDD to prevent inductive kick, BTW -- you may have killed your transistor on the first try and now you're just seeing that.
Comment: Report every node until Ohm's law and the datasheet conflict
Comment: If the transistor is operational, similar [values](https://imgur.com/a/jPqJ7Ln) should be measured at each point. The base current is unnecessarily high. R1 could be of much greater value.
Comment: 1&3 backwards on U1?
Answer: A fundamental error involves D1. Its anode should go to Q1's collector, not to GND.
A capacitor should be added from +5V DC supply to GND. This is not a fundamental error. But it will keep transient voltages from destroying your processor, and act as a local charge reservoir that will give your solenoid more "punch": something in the hundred(s) of microfarads.
When a solenoid is switched off, its stored energy dumps via D1 into the DC supply. The capacitor absorbs this energy and keeps the DC supply from momentarily rising...even a short transient above that which the processor can stand will cause destruction.
This processor seems to have 4 GPIO pins, one of which you are using to activate the solenoid. The other three pins are left open-circuit: their default state is to be GPIO input pins. Leaving high-resistance input pins floating is not good practice. Either change them to be outputs, or tie them to known logic states (high or low).

Darlington transistor for driving coils


In the attached image of the Hoffman development of Arup design, the wing is shaped in a somehow anhedral way. Why?

Question: Most airplanes of its days had a Dihedral, or a wing thickness tapering with a 'V' shape, this one is the opposite, hints exist as done to avoid: 'Dutch Roll', or that the ordinary way will impair performance. What is it??

Answer: This plane is very interesting as it highlights a few design options.  Firstly, in seems to have neither significant dihedral nor anhedral, but it does have landing gear underneath it, lowering its CG for stability.  Being low aspect ratio, the builder probably decided to forego dihedral as cross wind gusts could make for a rolly, uncomfortable ride.  A slight sweep in the leading edges of the wing would provide some "dihedral effect" when rudder was applied.
Now for the wing itself, not albatross or eagle, we'll go flying squirrel here.  But notice how low the landing speed is.  This is a virtue of lower AR wings, though not as efficient as high AR (albatross) wings, they do stall at significantly lower speeds.  This design was also applied to the Navy "flying flapjack" and it performed well.
And thanks for the article, the ads made good reading too!
Comment: Send me everything listed -- look at those balsa prices!
Answer: I don't think it's a deliberate anhedral. It's just a geometrical consequence of having an airfoil with flatter bottom. If you imagine a plane connecting the leading edge and the trailing edge, it will be flat. Or likewise, if the airfoil had a completely flat bottom, the lower surface would be flat, and the top one sloping down.
Comment: The question focuses on inferior side of Hoffman wing being flat, upper side thinning from root to tips, opposite as the Johnson Circular Wing plan, that probably never flew. In YouTube: 'Wingless wonders'; the Hoffman flies. Johnson's has a flat upper wing side, some kind of a dihedral in the inferior side, close to NASA 'Flying bathtub' lifting body. This dihedral-like, besides providing stability, if too much, it could induce 'Dutch Roll', raise drag, decreases chances of noxious Ground effect on landing, more possible with the flat bottom approach [![R B Johnson Round Wing 1931][1]][1]
Comment: Raoul J Hoffman was the engineer who changed the concepts of the podiatrist Snyder into the well flying Arup line of airplanes. No 'visibility' problems exist today for Short AR designs as cost of a TV camera and screen is below that of a full gas tank
Comment: These low aspect ratio wings had a vertical speed at landing higher than more common designs, but speed respect to ground was low, this can help in aircraft carriers and some dangerous airports, landing is along an inclined line, not a curve tangent to ground.


defining the dimensions of a bucket elevator chain link

Question: how to define the shape of a heavy duty chain link when the pitch of the chain and the traction load that the chain is subjected to is known?
lets say i consider the traction load as the maximum load the chain can support, how can i do the back calculation from that to find the required dimensions?
Answer: Assuming you have the load on the Conveyor belt and dynamic load factor, usually from 3 to 10, let's call that load Ft.
The pitch of a chain is the distance between two bushings in mm.
Ft is supported by shear stress in the pin and is 0.6 times the tensile strength.
You decide what steel alloy you use and calculate the surface area of the pin that is adequate to take the Ft, from there you have the diameter.
There are many types of chains and depending on the task same are better. the following is a quote from a handbook of design based on ISO standard. I added the link to the handbook at the end of my answer.

Block chains have a high tensile strength for a reduced width. They are used to convey heavy loads, abrasive loads
  or when violent shocks are expected (e.g.: draw benches).
  To increase the service life of the chain (better wear resistance), the blocks are sometimes bushed.

design conveyor belt handbook.


Baire property and $F_\sigma$ sets

Question: I am currently reading a proof for a theorem which concludes that a set A does not have the Baire property, if (1) is correct. So, $(1)\Rightarrow$A does not have the Baire property is shown. The proof is by contradiction and starts like this: Let $F=\cup_{n\in\omega}F_n$ be any meager set of type $F_\sigma$. My question is, if every set which does have the Baire property is a $F_\sigma$ set and if the converse statement does hold .
Answer: Every $F_\sigma$ set has the property of Baire; however, the converse is extremely false. Indeed, every Borel set (even every analytic or co-analytic set) has the property of Baire, and $F_\sigma$ sets represent only the first two levels of the Borel hierarchy, which has uncountably many levels.
It doesn't stop there, either. For example, it is consistent with ZF+DC (assuming large cardinals are consistent) that every set has the property of Baire. A way to bring this into the ZFC-world is: it follows from large cardinals that every set of reals in $L(\mathbb{R}$) has the property of Baire ($L(\mathbb{R})$ is a bit technical; roughly, this means that any set you can define in terms of real numbers has the property of Baire - in particular, every set you've ever heard of is in $L(\mathbb{R})$).

By the way, although it doesn't seem material to your actual question: what is property (1)?
Comment: The set A is a filter on $\omega$ and the filter can be considered as a subset of $2^\omega$ as stated in my question here: http://math.stackexchange.com/questions/1842206/meager-subset-of-2-omega. (1) actually is the following statement: For every partition $\{I_n:n\in\omega\}$of $\omega$ into finite sets, there exists $X\in\mathcal{F}$ s.t. $X\cap I_n=\emptyset$ for infinitely many $n\in\omega$.
Comment: But then, i don't understand the proof. The author should have started like this: Suppose $A$ does have the Baire property... This is a contradiction to ...
Comment: Re: your second comment, I can't comment on the proof without seeing more of it. But if you're trying to prove that $A$ **does** have the Baire property by contradiction, then you do **not** start out by assuming it *does* - you assume it *doesn't*. (Or was that a typo?) Can you give a link to the proof you're reading?
Comment: I am trying to proof that A does not have the Baire property. The proof can be found in chapter 4.1 as Theorem 2 in the book Set theory  on the structure of the real line by Bartoszynski. Shall i add it here?
Comment: @peer Well, I answered the question you asked in this post. If you want me or others to help with a specific proof, then yes, you should post that proof here.
Comment: Concerning my first comment: you asked for (1) in your answer.

Baire property and $F_\sigma$ sets


How does cell phone display image or video even before you start to capture?

Question: When a cell phone is used to take a photo or capture video the display continuously displays what a camera can see, does that mean the ccd/cmos device is exposed to light continuously? or is it displayed by some other means(with out involving ccd/cmos)? Is the difference between displaying and capturing a video(or photo) is only storage? Is cellphone continuously taking pictures for displaying, even if you don't take a picture?
Comment: [You already posted this question](https://android.stackexchange.com/q/190621/12442) on [android.se]. Don't post the exact same question on multiple Stack Exchange sites. It leads to information being split up and it wastes the time of people who are trying to help.
Comment: I'm voting to close this question as off-topic because it is about the inner working of a phone unrelated to the topic of computer graphics.
Answer: The answer is: it depends.
When the preview is active in your camera app, the camera is always taking pictures so that it can provide a live preview image.  The CCD is constantly binning and resetting charge accumulated from photons hitting it.  The phone is also processing the captured image and displaying it - all this requires battery power.  So if the live preview is not active then it will likely not be taking pictures to save on battery.
However, some phones have a smart sensor where you can unlock it with your face.  It might be taking pictures of your face even though it is not showing you a preview.  Some phones also have a mode where it takes pictures of you to see if you are looking at the screen.  This takes more battery power to leave engaged but it also will not show you a live preview so it saves some processing power there.  It all depends on the mode the camera is in.
Your phone will also continually adjust other settings though such as sensitivity, exposure time, and focus.
In a dark environment, the "preview" image that is displayed during live capture will be taken with high sensitivity (high ISO) with a short exposure time.  But when you take a photo, it might switch to a lower sensitivity (low ISO) and use a longer exposure time, which should produce a higher quality image -- provided you can hold the phone still for the entire exposure time.  Some phones will provide "modes" like sports mode or night mode, that will prefer either a short exposure time (to prevent blur - as in sports mode) or a higher quality image (as in night mode).
Also, in a dark environment in video mode, before you hit record as it displays a live preview, it might use a higher sensitivity and longer exposure time (but effectively lower frame rate - like maybe only 5-10 fps) but then when you hit record, in order to maintain 60fps it could only take pictures with an exposure no more than 16ms, which might make the video appear darker than the live preview was showing, but motion will be smooth.
Also, when you use a flash, the phone goes through a variety of different settings, switching between live preview, and flash on/off for focus and exposure estimation vs the conditions under which the final exposure are taken.
There's a lot of tweaking that goes into creating a good camera application.  And the front and back facing cameras can work in concert to provide other features beyond the camera application - and may be active even when not providing a preview image - depending on the application.
Answer:
does that mean the ccd/cmos device is exposed to light continuously?

Unless there is a physical shutter it will be continuously exposed to light.

Is the difference between displaying and capturing a video(or photo) is only storage?

yes.

Is cellphone continuously taking pictures for displaying, even if you don't take a picture?

If the data from the capture chip is not collected then it is lost. The phone will only capture the data when it needs to (either for displaying or storing). It can also cut power to the sensor to save battery.


Every 30 minutes on the sharp

Question: If the firework happens every 30 minutes from 7:00 7:30, 8:00, 8:30, ... 19:00
Can I say: There will be a fireworks display every half hour on the sharp.
Answer: I've never heard on the sharp before. It would be more idiomatic as: on the dot, or 7:30 -- sharp.
For this pattern, you could say: 7:30 to 9:00, on the half-hour.
Some other ideas:

on the dot and the thirty(-minute mark),
every half-hour, punctually or precisely
Comment: @walterhuang Either "every half hour", or "on the half hour and the hour".
Comment: so can i just say: The firework happens on the half-hour. thx
Comment: @user814064 thx
Answer: The phrase "every half hour, on the half hour" has the exact meaning you are looking for here.
Sharp relates to punctuality, and as such "at 7:30 sharp" would suggest that failing to arrive at 7:30 would result in a sanction (if you were obligated to do something or be somewhere) or that you would not be waited for and so miss whatever the scheduled event was.
On the dot refers to precision, and as such "at 7:30 on the dot" would mean 7:30 precisely, and not 7:29 or 7:31. Just how precise such precision would be in practice is another matter, but the figurative "dot" here is the precise point in the line or field of possibility.
"On the sharp" is not an idiom on would use, the closest I can think of it is "on the sharp end" meaning the area within a field or issue with the most pressing difficulties.
Comment: thx for the explanation. i will vote you up when i got 15 rep

Every 30 minutes on the sharp


screen coordinates to real world coordinates in opengl

Question: This is actually mixing artoolkit and opencv.
Opencv gives screen coordinates of my fingers top.
Artoolkit gives modelview of marker,which in turn gives modelview of the object drawn over the AR marker
For the finger i have screen coordinates.
I need to compare them to check where did finger hits hit.
So how do I do that?
Answer: this post explains very nicely how to convert from image to world coordinates.
Opencv virtually camera rotating/translating for bird's eye view
It is an extremely well-explained code. Now, if you need some of the parameters that go in those equations, this is another problem, and it can be only solved for specific situations. (Camera field of view,  rotation angles and translations)


unistall sql server 2005

Question:
I hope someone can help me . I 've Unistall all components sql server 2005 in the control panel but the configuration tools still there.
I try to open HKEY_LOCAL_MACHINE > Software > Wow6432Node > Microsoft > Microsoft SQL Server > 90 but did not find it .
how the solution of my problem ?
Comment: Why do you need to do that?
Comment: I want to uninstall sql server 2005 , because I have deleted some files in C : \ Program Files \ Microsoft SQL Server inadvertently . then I want to reinstall sql server 2005
Comment: Have you tried to run Setup->Repair?
Comment: yet, how? but I had to uninstall sql server 2005 in the control panel but the configuration tools still there.
Answer: Not sure if it will solve your issue but you can try something like this:
<code>start /wait <CD or DVD Drive>\setup.exe /qn INSTANCENAME=<InstanceName> REINSTALL=SQL_Engine REBUILDDATABASE=1 SAPWD=<NewStrongPassword>
</code>
See more at: https://technet.microsoft.com/en-us/library/ms144259(v=sql.90).aspx

unistall sql server 2005


App with proper PDF page numbering?

Question: I have a pdf file that has irregular page numbering (Roman numerals, then regular page numbers, then odd numbering scheme, etc..) created with Adobe Acrobat. Does anybody know of an iOS app that supports odd page numbering? When opening the PDF file in preview and Adobe Reader, the page numbers appear as they should, but when copied to an iOS device, the page numbers don't appear properly in iBooks or Adobe Reader for iOS, they just start at 1, 2, etc...
Comment: The expected behavior is that the pdf viewer will display proper page numbers (the page numbers embedded in the PDF with Adobe Acrobat). Both preview and Adobe Reader on Mac show the page numbers correctly (starting with page I, page II, all the way through until the number parts start) however, when copies to the iOS device via iTunes, neither Adobe Reader or iBooks display the page numbers correctly. I was asking for a PDF reader that will
Answer: I've finally found a solution that supports logical page numbers like the other PDF readers I have tried, but also respects custom page numbers embedded within the PDF. GoodReader shows the page numbers properly. It's $4.99
Answer: How do you assume that there's something wrong with all PDF viewers you've tried so far? Maybe simply page numbers are incorrectly embedded in the document which then has been saved to PDF?
If that's true, then there's nothing wrong with the viewer itself. Simply your document should have all page numbers regenerated. If it originally comes from Word, try to correct page numbers there and save to PDF once again. Open in Preview and check numbers in the footer.
Comment: The page numbers are all correct in preview and Adobe reader (the custom page numbers were created with Adobe Acrobat). However in both iBooks and Adobe Reader on iOS, the page numbers DO NOT appear correctly with the exact same file.

App with proper PDF page numbering?


Lord Kelvin's wonderful prediction

Question: My question is straight forward. How did Lord Kelvin accurately determine that -273.16°C is absolute zero. I guess this was not determined by experiments cause the equipment was not so developed. ( Please note that I am not sure that it was Lord Kelvin only who gave the concept of absolute zero.)
Comment: You *do* understand the [physics principle involved](https://en.wikipedia.org/wiki/Absolute_zero#Limit_to_the_"degree_of_cold"), don't you?
Comment: I recommend that you familiarize yourself with some elementary termodynamics, before asking this question. It is explained there.
Answer: Long ago I had to make a project about this topic. I disagree with other answers: Lord Kelvin, with the help of Joule, did actually find the absolute scale, because there's much more you are missing.
It's true that it was well known that $T=-273 ºC$ was acually the temperature at which wolume predicted for ideal gases gets zero. You can see it in many books like Callen thermodynamics.
However, setting $T=ºC+273$ is NOT enough to consider it an "absolute scale", because it still depends on the instrument you use. You must DEFINE temperature in such a way it doesn't depend on the substance used. You always measure a physical property related to T, but not directly T. What Kelvin did was finding a relationship between T and energies, heats and works, which are universal physical quantities that do not depend on the sustance. For this, he used the results of the ideal Carnot's engine.
Liek this, it doesn't depend on the substance but on measurable energies/heats. This is now indeed an absouet scale.
For the full development, check this book:

Gray, Andrew (1908). Lord Kelvin: an account of his scientific life
  and work

which you can find here:
https://archive.org/details/lordkelvinanacc01graygoog
Answer: It was observed that if you change the temperature of a gas at constant pressure, its volume changes linearly with the temperature (Charles' law), at least if the temperature is low enough.  The slope of the line turns out to be proportional to the volume of the gas at some reference temperature, say $T_0 = 0^\circ$C, with the proportionality constant $\alpha$:  $\Delta V / \Delta T = \alpha V_0$.  That means if you extrapolate the $V$ vs. $T$ line back to zero volume, you get a minimum possible temperature $T_\text{min}$, which is given by $T_\text{min} = T_0-1/\alpha$.  Furthermore, that minimum temperature turns out to be the same for different gases,  or for the same gas at different pressures, or for different initial volumes $V_0$. That is, it's a universal constant and not the property of a particular gas.  Gay-Lussac first measured it in 1802 to be $-267^\circ C$, and more recent measurements have put it at $-273.15^\circ C$.
Answer: He didn't accurately determine the value - just the principle that there was an absolute zero temperature scale.
Although probably fairer to say he popularised it, or put it on a firmer theoretical foundation, since Guillaume Amontons  seems to have made a reasonable experimental estimate of absolute zero 150 years earlier.

Lord Kelvin's wonderful prediction


How can I select the games from a backup drive to restore on Steam?

Question: I have a USB drive with CSGO, Portal, Portal 2, half life 2 on it, and I own all the games. I put in the drive and do the usual, but it's asking fora CD key. That's because there's a game in there that I don't own, but I own all the others. What can I do?
Comment: Can you remove the game that you do not own? And why do you have an unowned game on your USB?
Comment: It's my friend's usb, he has a bunch of games backed up
Comment: You and your friend are sharing a USB drive to back up each of your separately owned games?  Why don't you each just get your own USB drive?  Also, regarding the games you do own, why don't you have a CD key for them?
Comment: Basically I have a 2Mb/s internet connection and it will take very long to download all those games. He came from the US with all those games since he has a 180 Mb/s internet speed. I just bought all the games, so I don't think I can get the CD key
Answer:
Open Google and type App ID "game name". This will be the game you do
not own (e.g. Dota 2 would be "570").
Go to the backup directory and open "sku.sis" in Notepad.
Scroll sideways until you reach the section where it says "Apps".
Look inside the brackets for the App ID in question. The first number will indicate the listing number off the backup and the 2nd the App ID. (e.g. "0" or "570").
Delete the index number and App ID of the game in question (e.g. "0" or "570").
Save and close Notepad and try restore from backup again.
Answer: Separate the game you don't own onto different storage or your SSD if you have space. For example, I have Tales of Zesteria (but I don't own it on Steam) installed on my SSD and everything else that I own on my external hard drive. Also, do not import the non-owned game into Steam, otherwise, it won't run (for obvious reasons).


what is grid hosting

Question: I went to GoDaddy.com for hosting. They have menus like
1)website hosting
2)grid hosting
what is the difference between the two. I am new to this hosting and webapps stuff..
Answer: Grid hosting usually means that the web space you rent is not located on one (potentially shared) machine, but is more like a "virtual machine" (think VMware) which is hosted on a cluster of servers (a grid).
While resources on a single machine are limited and might run out, especially if it's a shared host and you have to share your resources (memory, bandwidth) with potentially hundreds or thousands of other users who are hosted on the same machine as you, grid hosting is more flexible, as your virtual website could leverage resources from more machines in the cluster if necessary. This of course also increases reliability of the website, as the failure of one grid node doesn't matter, another server takes over, while the failure of your dedicated or shared host takes your website offline.
I would assume that they refer to the single machine as "website hosting".
Update
GoDaddy has an FAQ about their grid hosting, which should answer all additional questions you might have.
Answer: A reply from Godaddy Support:

Please be advised while there is unlimited compute cycles for site server and not for database.
Answer: From wikipedia:  Grid Computing  | Cloud Computing.  I haven't seen 'grid hosting' as a common phrase, but it could be taken to mean using one of the earlier two concepts to host a website in a scalable manner.
However, if godaddy is offering 'grid hosting' I suspect they're offering to grid computing to you in such a way that has nothing to do with hosting a website.  They're offering to sell you large amounts of processor power with low communication requirements, as opposed to selling you web hosting which is typically high communication requirements with low processing requirements (relative to one another of course)
Answer: Grid computing is a collection of computing resources from multiple locations to reach in a common location. Grid is also called distributed system.it is similar to a VPS but generally has more storage then VPS Servers.
Answer: Grid Hosting is a form of distributed hosting is when a server cluster acts like a grid and is composed of multiple nodes.
Currently, various hosting service types are available..you can find details for them from here..
From above these, you can select your desired hosting provider and type.

what is grid hosting


Finite Element method Implementation

Question: I have written a program for the finite element method for an elliptic one dimensional problem.Initially I assumed a mesh that had only 10 points , but since the error was far above my tolerance level, I changed my mesh size to 30 points.But while applying the FEM for the mesh with 30 points , I had to run my program all over again with N=30.
My question is -:
 Even though I have found the exact values of the solution at 10 points( for FEM for 1d case ,the fem solution can be proved to be exactly the actual solution at the nodal points), why should I start the process all over again and find values at 30 nodal points.Why can't I do it for just the newly added 20 nodal points.Is there a way to do so?
Answer: When you apply the FEM to a differential equation, you first write the problem in the weak/variational form, for a narrower solution space, for example
$${V} = \{ { \omega :| \omega  | +  |\omega ' | < \infty } \}.$$
Then, to actually solve the problem, you have to discretize that solution space, i.e., you have consider a finite subspace of the solution space. Most likely, you decide to consider your solution as a linear combination of hat functions and hence
$V_h = \left\{ {{\omega _h} \in V:{\omega _h}{\textrm{ is piecewise linear, continuous on the chosen mesh}}}\right\}$
and the basis of this space consists of $\{\varphi_j\}^{N}_{j=1}$, where
$${\varphi _j}\left( x \right) = \left\{ {\begin{array}{*{20}{c}}{\frac{{x - {x_{j - 1}}}}{h}}&{,x \in [{x_{j - 1}},{x_j}]}\\{\frac{{{x_{j + 1}} - x}}{h}}&{,x \in [{x_j},{x_{j + 1}}]}\\0&{,x \notin [{x_{j - 1}},{x_{j + 1}}]}\end{array}} \right. , j=1,\cdots ,N.$$
At this point, I hope you've already figured out the answer to your question :)
Each time you modify your mesh, you also modify your hat functions, that is, the basis of your discrete solution space. Thus, to find your new solution in the new basis, you have to perform the calculations all over again.
-EDIT-
If you're looking for a method that allows you to avoid computing your solution all over again, then you should read about Structure Adaptive Mesh Refinement (SAMR) used within the finite difference method (FDM) framework.
A good way to get a grasp of the concept is by reading the following master thesis:
"A patch-based partitioner for
Structured Adaptive Mesh Refinement" by A. Vakili
Comment: That's precisely my question, why should I throw away the previous solution that I have got.Is there a method(surely not FEM !) that calculates the solution for the refined mesh( coefficients for the new leaner basis functions) , using the previous solution.
Comment: I've edited my post to answer your question.
Comment: That's a good way to do it.Solving the problem locally on each refined element.Yeah, I somewhat get it.

Finite Element method Implementation


what is the best way to export data from Filemaker Pro 6 to Sql Server?

Question: I'm migrating/consolidating multiple FMP6 databases to a single C# application backed by SQL Server 2008. the problem I have is how to export the data to a real database (SQL Server) so I can work on data quality and normalisation. Which will be significant, there are a number of repeating fields that need to be normalised into child tables.
As I see it there are a few different options, most of which involve either connecting to to FMP over ODBC and using an intermediate to copy the data across (either custom code or MS Acess linked tables), or, exporting to flat file format (CSV with no header or xml) and either use excel to generate insert statements or write some custom code to load the file.
I'm leaning towards writing some custom code to do the migration (like this article does, but in C# instead of perl) over ODBC, but I'm concerned about the overhead of writing a migrator that will only be used once (as soon as the new system is up the existing DB's will be archived)...
a few little joyful caveats: in this version of FMP there's only one table per file, and a single column may have multi-value attributes, separated by hex 1D, which is the ASCII group separator, of course!
Does anyone have experience with similar migrations?
Answer: I have done this in the past, but using MySQL as the backend. The method I use is to export as csv or merge format and them use the LOAD DATA INFILE statement.
SQL Server may have something similar, maybe this link would help bulk insert


Arm cortex-m3 mov and ldr

Question: I don't get why I can't write mov r1, #5000. Why I have to use ldr instead? R1 is 32 bit register and 5000 fits in range. And as I discovered I can mov r1, #255 but can't  mov r1, #256. It seems weird for me.
Comment: This question has already been asked dozen of times.  See: [Contants on ARM blog](https://community.arm.com/groups/processors/blog/2010/07/27/how-to-load-constants-in-assembly-for-arm-architecture).
Answer: read the documentation on the instructions, in this context the instructions are fixed length, so you dont have room for both the instruction information (opcode, etc) and a 32 bit immediate in the 16 or 32 bit instruciton, not possible so some limitation on the immediate is required.  With x86 for example it is variable instruction length so they can have long instructions, but it is easy to argue that doing a pc-relative load or a few fixed length instructions of the same size have no significant extra cost with a pipeline.  so six of one half dozen of another.  The mips fixed instruction length move immediate solution has its strengths and weakness and for each of the arm instruction sets each has its own solution with strengths and weaknesses.
for arm the assemblers (certainly gcc, probably arms toolchain, keil, etc) there is a shortcut you can do and the assembler will choose the simpler path
ldr r1,=immediate

if it cant encode it into a single instruction (note there are some move negative, math with the program counter and other tricks it can play that you might not be thinking of at the time or not knowing the pc might not be able to use), if it cannot then it may encode it as multiple instructions mov immediate then an orr, or encode it as a pc relative load.
The specific limitations for each instruction sets mov immediate is well documented in the arm architectural reference manuals,  you can just get the armv7 one and it has all the encodings for that and prior architecture versions.  with that knowledge you should be able to determine yourself whether or not the mov will work before having the assembler tell you.
Answer: In ARM Cortex-M3 MOV is 16bit instruction with following definition MOV<c>{<q>} <Rd>, #<imm8>
Immediate values are stored as part of opcode in arm instructions
opc[15:11]='b00100 =>which identifies instruction.
opc[10:8]=<register no>
opc[7:0]=<imm8 value>

So, with above instruction you can have 2^8 -1 =>255 as maximum immediate value
Though by specifying instruction specifier .W you can force assembler to pick32 bit encoding for MOV, but that will only have 11bit of immediate value
You can use T3 version of MOV having 16bit of immediate value support
where you can move 0 to 65535 to a register
So instead of mov r1, #5000
you can use following instruction to load any value to a register from 0 to 65535
MOVW r1, #5000

Arm cortex-m3 mov and ldr