Travel to Australia with new passport (with visa in old passport)

Question: I was granted a visa to Australia few months ago. I'd like to travel to Australia in few days. However, I've just renewed my passport and I don't have enough time to inform them about my passport renewal. Can I travel to Australia by carrying both my old and my new passports?
Answer: According to the Australia Department of Immigration and Border Protection, you need to notify Australia of your new passport before you travel, even if you have a visa label in your old passport. Australian visas are linked to your passport number, and travelers might not have a visa label in their passports at all.
If you read the form instructions for the notification form, it states that you can complete this form online. So you may be able to do this quickly enough to be able to travel.
Note that the form instructions state that you will not receive a reply. You can log in to ImmiAccount to check the status.
If your old passport has a visa label in it, you should bring it with you when you travel. Do not try to remove the label and place it in your new passport.
Comment: @TejasUnnikrishnan That IS the latest on this.
Comment: What is the latest on this? I have a new passport and old cancelled passport with valid visa. The visa is electronic and travel document on visa is old passport.


Phantom Voltage When Near Outlet?

Question: I am pretty new to electronics, and have mainly worked with DC circuits. I'm majoring in Computer Science, but I also find electrical engineering interesting, so I am learning as much as I can. Well, my multimeter measures about 0.050 to 0.100mV when not connected to anything. As soon as I move close to the wall outlet, it creeps up to 0.1 volts, then 2 volts, then when I am pretty close to it, it reads about 4 - 6 volts. Also, when I plug one lead into the hot or neutral, why does it read 6 volts or more? And between neutral and ground, it usually reads 0.4 volts when there is minimal load on the outlet. I heard that that is normal, but is 4.4 volts from neutral to ground normal when a 1300W heater is running? Thank you for your help. I'm still learning, so these questions may sound stupid. And yes, I am taking safety precautions so that I do not get shocked.
Comment: Are you measuring AC or DC voltages?
Comment: I am measuring AC voltage on a wall outlet.
Comment: Depending on where you live you may get 110 to 220 Vrms . So the current that your heater needs is 1300 /220 =6 A . Even a small resistance like 1 ohm could easily create 6 V drop
Comment: I would be concerned about 4.4v when there's a heater running **if** you are in a jurisdiction that mandates PME (Protective Multiple Earthing). I can't imagine earth bonding straps that would allow such a large voltage drop, without them being loose or defective in some way. If PME is not mandated in your area, then that sort of voltage could easily arise without problems.
Comment: Assuming 110V and 9Ω at the heater, this basically means ~400mΩ of resistance until to the point where N and GND meeet.
Comment: BTW, "[phantom voltage](https://en.wikipedia.org/wiki/Phantom_power)" is actually a thing (but something completely different from the effects you describe).
Comment: Thanks. I was just reading up on it, so I might have mixed up the terms.
Answer:
0.050 to 0.100mV when not connected to anything

This is pretty normal. It's not a big number and probably just represents the noise floor of your multimeter.

As soon as I move close to the wall outlet, it creeps up to 0.1 volts,
  then 2 volts, then when I am pretty close to it, it reads about 4 - 6
  volts.

Also pretty normal. The electric fields emanating from house AC wiring can make a multimeter show these kind of voltages when close up. It's mainly due to the electric fields capacitively coupling to you probes with your body acting as a capacitor to ground. It would be interesting to see what the voltage drops to when you stop holding the multimeter - I would expect it to still register a number but a smaller number.

between neutral and ground, it usually reads 0.4 volts when there is
  minimal load on the outlet. I heard that that is normal, but is 4.4
  volts from neutral to ground normal when a 1300W heater is running?

4.4 volts is certainly no un-heard of. Usually neutral is connected to earth at some point between your house and the local sub-station and given the volt drop down the neutral wire when passing several amps this would be fairly commonplace.
Comment: Does the 4-6v reading when "close" to the outlet demonstrate the principles that a Non-contact voltage detector would use to warn a user of a live circuit?
Comment: @JPhi1618 I guess so but without looking at a circuit I can't be 100%.
Answer: These days we are swimming in EM fields (Electromagnetic) and signals flying all over the place.
Your multi-meter probes measure the potential difference between the 2 probes and are like receiver antennas too. With both probes just floating, you are just picking up the time averaged e-field that's in your immediate vicinity.
Most multi-meters display the RMS value of what you are measuring too.
Without a proper reference aka one probe just "floating" its possible that that probe will get "pulled up" to the probe that is touching a strong voltage and you see the difference over the internal impedance.
And as the other guys said there is coupling, inductive and capacitive.
Changing magnetic fields give rise electric currents, and electric currents give rise to magnetic fields.
Still today most of electrical engineering is based on Maxwell's equations, despite quantum electrodynamics being the complete picture, we still go back to Maxwell, Faraday, Gauss and Ampere.
Theres a great website called maxwells-equations.com which gives a great overview of the 4 great equations, without being too scary with the maths.

Phantom Voltage When Near Outlet?


Simple solidity code not returning any value with remix ide

Question: pragma solidity ^0.4.24;

contract practice {

   int a = 10;

   function trial() public returns (int) {
       return a;
   }

}

Answer: Functions can either be invoked via transactions or calls. Transactions are used for functions that mutate state, and transactions do not have return values. Calls cannot mutate state but do have return values.
Remix uses a call only when the function has the pure or view modifier. Just add view, and things will work how you expect:
function trial() public view returns (uint) {

Answer: Change your function definition to include view. Then it will return the value of a in Remix IDE.
function trial() public view returns (int) {
    return a;
}


V Fork happened yet?

Question: I purchased 1 monero coin several months ago and is being held in a Freewallet. Has the Fork happened yet? Do I have 10 coins now or just 1?
Answer: There is no support for MoneroV in Freewallet. Unless they support the fork, you will not be able to claim MoneroV.
As a reminder, Freewallet controls your private keys. If you used a different application such as Monerujo, Cake Wallet, or X Wallet, you could restore your Monero (including possibly claiming coins) on another device.
Answer: You may have 1 XMR and 10 XMV but freewallet is a scam, you may just have nothing.
Also to claim your 10 XMV airdrop, you must enter your private keys in XMV wallet, which could be a scam to get your XMR as the wallet code has not been disclosed, and you may also be part of a global privacy attack against monero.
Luckily for all of us (and that's the reason it is a scam) freewallet own the private keys (and therefore own your coins) and you would not be able to claim the airdrop shitcoin, neither you're even sure you could withdraw your XMR on a real, safe, wallet.
Answer: If we decide to support XMV, our users will be credited with XMV coins accordingly. No private keys will be required for that.
As it was mentioned here, the fact that some platform does not support XMV shall not mean a wallet provider is a scam. We still consider the possibility to support this fork and will notify our users by email, on Facebook, and on Twitter if we start supporting these coins.
Comment: "No private keys will be required for that" is incorrect.

V Fork happened yet?


What determines crank length?

Question: Without getting really technical what determines the length of the cranks that you would use on your bike? I was wondering if longer cranks without being ridiculous would act as a fulcrum and make climbing easier in a higher gear ratio.
Comment: Sadly cranks longer than 175mm are uncommon because they're expensive, and they're expensive because they're uncommon.  Repeat.   I suspect more people would use them if they were more available.
Comment: @Criggie Longer cranks make ground strikes more likely and most people aren't actually very sensitive to crank length. So, for most people, cranks longer than 175mm have a disadvantage but no real compensating advantage.
Answer: As an opener to your question....

Femur length.
Theoretically. The longer the femur - the longer the crank length.
The old pros used to favour the longer crank lengths 175mm to
180mm being common. Iirc Pantani who was a short rider even
favoured a slightly longer 172.5mm for reasons of leverage as you
mention above. There has been a trend towards shorter crank
lengths - which lend themselves to a slightly faster cadence.
Natural cadence speed.
Most riders find when they switch to shorter cranks, their cadence
increases.
Flexibility.
A longer length will bring the upper leg at the top of the stroke closer to the abdominal cavity.
Answer: You are correct that a longer crank arm acts as a longer lever resulting in greater peak torque output on the power stroke of the pedaling cycle. That might lead us to think that longer cranks are better. However, the optimum crank arm length is that which enables a rider to produce maximum power which does not necessarily correspond to maximum peak torque.
The most important factor determining optimum crank arm length is obviously the length of the femur (between hip and knee joints), but there are other physiological factors that mean a given rider may prefer a slightly longer or shorter crank arm.
Really, there's no simple way of determining optimum crank arm length. Pro riders who really want to do the optimization will do controlled tests with different crank arm lengths and a power meter.
Comment: I'll add to that, that you should rarely use full peak force anyway. If the lever of your cranks is relevant to your power, your gear is too high. Concentrate on power output, and let your gears convert that into the right torque at the wheel. That's what gears are for.
Comment: Wow, thanks guys. I really didn't expect that much interest.
Answer: You have two questions there.
What determines crank length?

Personal preference
Equipment availability
Drive train type
Stories you read on the internet

Not necessarily in that order.
Do long cranks make climbing easier on high gear?
Increasing crank length increases torque and reduces pedaling speed (gears can be used to convert RPM to torque and vice versa). Whether your body accepts such trade decides if it makes your climbing easier. You will still need to output the exact same power.
Comment: Research has been done, and the result is that efficiency and peak power are almost constant for wide range of crank lengths. Personal preference is usually fine.
Comment: Quite a lot of BS has been said and written about crank length. There is certainly a great myth about the correct length which probably doesn't exist. Feeling comfortable is most certainly the best answer.

What determines crank length?


Why the quantities are dimensionless in curves plots?

Question: In a lot of plots they use dimensionless quantities, why really we don't let quantities in their physical dimension and plot the curves normally.
Comment: In my opinion, the dimensionless forms are special.  Once you have a plot which is dimensionless on both axes, the line or curve on that plot describes all combinations of the variables that were involved in the dimensionless quantities on each axis.  And as pointed out below, there will not be a requirement for multiple lines or curves on such a plot ... one line or curve tells you everything that you need to know.
Answer: Dimensionless constants have a special significance in physics. This is well described in the answers to the question Dimensionless Constants in Physics.
Having said this, whether or not you use dimensionless quantities in data analysis is to some extent a matter of taste. In my time as an industrial colloid scientist I generally didn't manipulate plots to be of dimensionless quantities, but then this was very much applied physics. If I were studying fundamental issues, e.g. at CERN, I might be more inclined to work with dimensionless quantities.
Answer: The reason why this is done is because dimensionless data usually follows a single curve rather than multiple curves for different values of the parameters. This is nice because the figures become nicer and the data more organized.
This dimensional reduction of data occurs because, by the Buckingham-$\Pi$ theorem, there are fewer combined dimensionless parameters than there are individual dimensional parameters. These dimensionless parameters give more information about the underlying phenomena than the dimensional parameters do by themselves.
Let's take an example; below is a figure of transient heat transfer through a semi-infinite solid. If you look at the top figure it shows that at different times the cross-sectional temperature profiles are different; this makes sense because the solid is heating up. However if you properly scale the temperature and spatial coordinate and make them dimensionless:
$$\theta = \frac{T-T_i}{T_s-T_i} \quad \eta = \frac{x}{\sqrt{4\pi t}}$$
then all profiles (for limited short time scale) collapse onto a single curve, the figure below.

I think this single curve in general is much more useful because it no longer depends on the values of the individual parameters (e.g. initial and wall temperatures) but on a dimensionless number which i can replicate if i ever have a similar situation but with different values for the initial and wall temperatures. I can then still apply this graph.
In my opinion most scientific figures should be presented in dimensionless form. Then it also doesn't matter anymore what units system the author worked in; he can use imperial units and i can work in metric units, it doesn't matter as long as the combination of parameters into dimensionless parameters is the same value.


Why does my cat "catch and run"?

Question: I have one of those feather toys on a long stick. If you move it around fast enough, it sounds like feathers flapping. All the girls go nuts for it, as they run and jump around trying to get this fast moving "bird". When my youngest catches the "bird" she pulls till I let go of the stick, runs around the house with feather in mouth and stick dragging on the ground behind her, she does a full lap or two around the house before coming back to me and dropping the feather in front of me. What in the world is my little cat doing? Is she doing like victory lap, what purpose does it even serve? It's funny and I love it, I'm just curious why she does it.
Answer: That is how cats hunt in the wild.
While hunting small animals like mice only requires a well timed paw strike, cats employ different tactics for slightly larger animals. They usually bite the neck. Later, if they can, they pinpoint the prey and if they can't, they drag the prey until it can't resist.
Victory dance also fits to general cat behaviour. Many cat owners woke up to their cat bringing presents. I had a cat who waited by his kill every time until someone takes the poor animal to a trash can. He really was proud of his kill.
So, I would say it is not nuts, it is a healthy way for a cat to engage in game play. I'd also say he is quite lucky to have an owner who plays regularly.
I hope this helps.

Why does my cat "catch and run"?


NEC 2016 AFCI question

Question: I am currently dealing with a little confusion regarding arc fault protection and how it would be enforced by 2016 NEC code. I'm not a licensed electrician, I'm doing an apprenticeship and the guy overseeing my work is unavailable right now, was hoping for some advice.  I ran a branch circuit to a shared switch box consisting of 2 - 3 way switches powering independent lighting circuits. I used a 14/3 cable not being aware he was enforcing this code. (I haven't seen it enforced much around here in my experience). I was am now being told that you can not share a common neural and still arc fault protect them. I think I may have found a way if I were to use a 2- pole 15 amp breaker they would only need one neutral, correct? Is this violating any other NEC codes in the process by them having a common trip? Also I am finding GE has discontinued 2 pole afci breakers. I would have to order online to match the load center but does anyone have any idea as to why they stopped making them? Were they having trouble with the functionality? Any advice you guys may have would be a big help. Thanks
Comment: @Mike -- this was actually a design revision known as MOD 3 -- see my answer below
Comment: @Mike, you should give ThreePhaseEel the best answer check mark.  I was wrong, wrong, wrong!
Comment: The local electrical supply house doesn't have double pole AFCI's?  If not, why can't you order it?
Comment: I'm being told ge doesn't make one anymore and I'm worried it was due to safety issues. Have a ge panel
Comment: Multi-wire branch circuits are much more complex than they seem, and are loaded with pitfalls. I have fixed many serious mistakes in them; I seem to know more about them than my town's career electrician   I am saying take the time to become very well-read in their various complexities, do your own learning, and have very close attention to detail when working with them.  You will become more cautious about using them at all, and will probably stop calling them "shared neutral" :)
Answer: GE (THQL) AFCIs don't come in two pole any longer -- because they don't need to
Your apparent lack of ability to find two pole THQL AFCIs is actually due to a manufacturing revision to the single pole units.  Mod 3 single pole THQL AFCI breakers can be handle-tied for multiple pole applications, as they do not use a CT-based trip for arc-to-ground detection.  (You still need to wire the load neutral to one of the AFCIs, but either one will do -- you don't need to connect it to both.)
See this GE handout for details.
Comment: That's interesting. I'd like to cut one of those open, to see how it works.
Answer: Unfortunately most AHJ's these days require some form of fault protection... whether it be GFCI,  AFCI, CAFCI, or the newer DFCI.   DFCI's have class A GFCI protection ( 5mA trip) unlike their former cousins CAFCIs which are more of an equipment GFCI (30mA trip) with Arc fault protection too.
Maybe you can use a discontinued double pole AFCI.  Good question on why they discontinued some of the AFCIs. Probably not enough demand and not required by Code.
By the way, the guy overseeing your work should technically be your Boss, legally he cannot sub you out as a independent contractor since you're not liscesned.
Comment: CAFCI (Combination Arc-fault Circuit-Interrupter).   DFCI  (Dual Function Circuit-Interrupter). GFCI (Ground-Fault Circuit-Interrupter).
Comment: Well in this aspect he is, but overall we are partners in a business. I am a general contractor. I recently merged with my brothers electrical contracting company. I am very capable of doing the work just haven't done much with arc fault and the 16 code book. So my question now is short of ripping open walls is there anything I can do too be code compliant off the 1 neutral?
Comment: DFCI would only be required where both AFCI and GFCI were required, right?  Should be no need for DFCI in a living room, for example.
Comment: Yes, living rooms and similar area could be on a plain AFCI...no GFCI protection required.
Comment: Exactly, all I need is afci as it is a billiard room. I didn't realize he was enforcing this code because it isn't enforced in my area yet everywhere. I only have one neutral for 2 separate lighting circuits. Can I carry a common neural some way or do I have to rip walls open to get a second neural to the panel. Everything is 100%finished and I'm looking for an alternative option
Comment: Updated answer... Sorry I was a bit off on some things.
Comment: Thank you for your help guys, it seems as long as I can confirm ge didn't recall for safety I can order one online and carry the single ground. I got 40' of sheetrocked ceiling going to a flush mount sub panel on a finished wall. Crown all around and 2 walls to get past. Been stressing this since I talked to the inspector earlier. Thanks for dumbing the theory down for me also
Comment: The correct answer is that GE AFCIs only come in one pole because the Mod 3 H/W can work on shared neutrals when handle tied...

NEC 2016 AFCI question


Is there a way to get an process exit status after many more commands have been issued in linux?

Question: If I have a lot of commands I've issued and I want the exit status of a process that exited say 100 commands ago. Is there a struct, file location, or variable in linux I can access all of exited processes and see information about them?
Answer: If BSD process accounting was enabled (accton on was issued), with GNU acct 6.6.3 or above, you can get that information from lastcomm --debug or dump-acct /var/log/account/pact (or wherever the process accounting data is stored on your system).

$ perl -e 'exit 123'
$ lastcomm --debug | grep perl
CURRENT REC: perl            |v3|     0.00|     0.00|     0.00|  1000|  1000| 26328.00|     0.00|     332|    8530|     |     123|pts/1   |Wed Sep 19 20:21:26 2018
$ dump-acct /var/log/account/pacct | grep perl
perl            |v3|     0.00|     0.00|     0.00|  1000|  1000| 26328.00|     0.00|     332|    8530|     |     123|pts/1   |Wed Sep 19 20:21:26 2018

You get the exit code in the 3rd last field and whether it was killed or not (but not the signal number, see @mosvy's answer for that) in the 4th last one.
Answer: If you're on debian, you can install the acct package in order to enable process accounting, but notice that neither lastcomm --debug nor dump-acct show anything like the exit status or the signal that terminated a process.
If order to get that data, you can use a script like this:
$ cat pacct.pl
#! /usr/bin/perl
use strict;
use Config;
printf "%-7s %6s %6s  %8s %8s  %s\n",
        'STATUS', 'UID', 'PID', 'BTIME', 'ETIME', 'COMMAND';
my @sig = split ' ', $Config{sig_name};
$/ = \64;
while(<>){
        my @f = unpack 'CCSL6fS8A*', $_;
        my ($flag, $version, $tty, $exitcode, $uid, $gid, $pid, $ppid,
                $btime, $etime, $utime, $stime, $mem, $io, $rw,
                $minflt, $majflt, $swaps, $cmd) = @f;
        my $s = $exitcode & 0x7f;
        my $status = $s ?  "SIG$sig[$s]" : $exitcode >> 8;
        printf "%-7s %6d %6d  %02d:%02d:%02d %8.2f  %-16s\n",
                $status, $uid, $pid,
                (localtime $btime)[2,1,0],
                $etime / 100,
                $cmd;
}

# perl pacct.pl /var/log/account/pacct
# tail -f /var/log/account/pacct | perl pacct.pl

This assumes the version 3 of the log file format -- see acct.h.
Notice however that this isn't that useful, because only the process/thread name is included in the log file (ie the basename of the executable, truncated to 15 bytes, and which could be easily faked with prctl(PR_SET_NAME)), not the path of the executable or the arguments it was invoked with.
If you want to extend that script to also display the stime, utime, etc fields, this may be useful:
# translate comp_t to float
# utime, stime, mem, minflt, majflt are in the comp_t format
# io, rw, swaps are never set; they're purely decorative
sub comp2f {
        my $m = $_[0] & 0x1fff; my $e = $_[0] >> 13; $m * 8 ** $e;
}

Note: Instead of installing the acct package, you can also turn process accounting on with:
# mkdir /var/log/account
# perl -e 'require "syscall.ph"; my $f = shift;
  open my $h, ">>", $f or die "open >>$f: $!" if $f;
  $! = -syscall SYS_acct(), $f // 0 and die "acct $f: $!";
' /var/log/account/pacct

Comment: What version of Debian did you try lastcomm --debug/dump-acct on? It worked for me on Debian unstable and on Ubuntu 18.04 (though doesn't give the signal number for those processes that were killed)
Comment: Note that it's not the _command name_, it's the _process name_ (changed by each `execve()` call the process makes to the first 15 bytes of the basename of the executed file). You can't change it with overwriting `argv[0]`, but with `prctl(PR_SET_NAME, newname)` or `execve()`. When you do `env sh -c 'exec bash -c "exit 123"'`, that's one process that runs in turn `env`, `sh` and `bash`. The pacct log will show only one entry for `bash` (the name of the process at the time it exited)
Comment: @StéphaneChazelas stretch(stable)
Comment: Yes, you need GNU acct 6.6.3 or above. stretch has 6.6.2.
Answer: The
  set -o pipefail

is pretty close to what you want; it will

A  pipeline  will not complete until all components of the pipeline have
   completed, and the return value will be the value of the last non-zero command
  to fail or zero if  no  command has failed.

So if you have 40 commands piped together, and the third command gives a return code of 8, and the rest complete successfully, then the overall return code would be 8.  To figure out which command gave the bad return code would be tricky.
Comment: Yeah thanks. There's a PIPESTATUS[0] environmental variable as well for pipelines. This would be just in general.
Comment: There is no indication that the commands are issued as part of the same pipeline.
Comment: Good point; I didn't read the question closely enough, but I'll leave the answer just in case someone may benefit from it.  It was one of my nice surprises I found when moving from Solaris to Linux.


What issues are most important to cover in Corporate Security Policy?

Question: What about a Privacy Policy? Both internal, and external.
Comment: It would be nice to see industry specific recommendations, if applicable
Comment: The referenced Area51 proposal "has been deleted." Can someone reference or copy the original proposal here, or delete the reference if it's no longer applicable?
Comment: @JohnnyUtahh not really relevant, that was just when we were bootstrapping the site, from a set of merged proposals...
Answer: Key points:
It should outline the security acceptance/appetite of the organisation in order that the standards which support the policy can be defined in the correct environment.
It also needs to define responsibilities, ownership and sponsorship.
Updated just to provide some examples, as I did leave this pretty light. At high level you should have at the minimum policies to allow you to measure, understand and regulate your technology risk. These will also be required from a governance perspective in a lot of environments -

Information Security Policy
Information Classification Policy
Acceptable Use Policy
Data Retention Policy
Data Protection Policy
Risk Assessment Policy

You will probably also want to look at the following if you provide services or products to larger organisations, as they may run a governance scheme which includes their 3rd parties -

Corporate and Social Responsibility
Policy
Environmental Policy
Equal Opportunity Policy

In the UK you must define your data protection requirements with respect to the Data Protection Act 1998. You should also construct your policy framework taking the ISO27001 family of standards into account, as many security audits and assessments for the regulator and for the IT piece of statutory audit are structured around 27001.
Answer: A corporate security policy should be short, easy to read, and in general terms. It should basically list what the overall threats and risks are to the business and the general approach for mitigating them.
For example, if you have a company who's value is in the data it stores in a database, a corporate security policy may state that the database should be protected with multiple level security controls including network access controls and encryption controls, and perhaps that sensitive data should be stored in systems which exist under strict change control.
The implementation of those details is going to depend more specifically on the system itself and the chosen standardised technologies by the business and so should be detailed in lower-level documentation.
Answer: I agree with the above comments - the "right" policy largely depends on your organization.
However, it may be helpful to review the ISO/IEC 27000 series, which is a set of standards for information security management often adopted by large IT organizations (http://en.wikipedia.org/wiki/ISO/IEC_27001, http://iso-17799.safemode.org/).
For example, 27002 is a "code of practice" which covers things like:

Risk Assessment And Treatment
Security Policy
Security Organization
Asset Classification and Control
Personnel Security
Physical and Environmental Security
Communications and Operations Management
Access Control
System Development and Maintenance
Information Security Incident Management
Business Continuity Management
Compliance

Even if you don't fully adopt it, I'd start with that standard to develop a draft table of contents for your policy.
Answer: That depends: what are the biggest risks to your business? Security policy shouldn't be about mandating anti-virus because all the cool kids have anti-virus, it should be about understanding what threats it's most important that you mitigate, and defining a strategy (though not tactics) to perform such mitigation.


Location of Certain Location words

Question: I have a couple of Chinese sentences that I have been struggling with. I know basic grammar order: Subject, Time, Place, Verb, Object but I am unsure how to construct sentences of this nature:
ex. I want to have practice outside
I want practice to be outside
I want to practice outside.
In Chinese, would all of these questions be phrased the same?
Answer:
I want to have practice outside -  我想在外面進行練習

In this sentence, "have" is a verb "practice" is a noun.
"have practice" means "to engage in practice" which is "進行練習" in Chinese

I want practice to be outside - 我想練習在外面進行

In this sentence "practice" is a noun object, "to be outside" implies " to be held outside",  which is "在外面進行" in Chinese

I want to practice outside - 我想在外面練習

In this sentence "practice" is a verb, and "outside" is a  preposition & adverb, which is "在外面" in Chinese
Comment: Thank you. Just one question- I have always learned location comes before verbs. Why does 想 come before the location words?
Comment: @Beginner  "我想 (I want)"  is the main phrase, "在外面練習(practice outside)" is the relative phrase, As you can see, in "在(外面)(練習)" , it does place the location 外面 before the verb 練習, If the sentence is just "我在外面練習" (without the verb 想), it would be a common sentence,  with location come before verb

Location of Certain Location words


External Air Conditioner Condenser Capacitor replacement

Question: I have a couple of questions about testing and replacing the capacitor on my home heat pump external condenser unit.
1. How can I reliably  test the capacitor (what tools do I need?)
2. What safety precautions do I need to take when handling the capacitor (aside from the obvious task of shutting off power to the interior blower and external units). This is a capacitor and it stores electrical current. I'm assuming I need to wait a period of time after I've killed power to the unit before handling it.
Comment: The techs have a capacitance mode on their multimeters. They remove all the connections and test the capacitor. They know what the values are supposed to be. If you remove wire connections, be sure you label them or take a picture so you can reconnect them properly.
Comment: Always short caps prior to messing with them never trust the discharge resistors if they have them those resistors fail and getting a hard jolt from a cap can hurt.
Comment: short them out, wait 30 seconds, short out again; a lot of caps can actually (partially) self-recharge without adding charge.
Answer: Changing a cap is easy you have the basic idea. First pull the fuses or disconnect the power to the unit the disconnect should be close to the outside unit. Next if your cap has 3 connections use a screwdriver to short the common or c post to the fan then common to herm , if 2 post just short them together it only takes a second to fully discharge a capacitor. Make sure to note the wire colors connecting to the posts. To check the cap if your meter doesn't have a capacitance meter built in use the ohm meter (no wires connected to the cap put in ohms and put the meter on the cap you are looking for a slowly raising value if it shows totally shorted the cap is bad if there is no charging or slowly increasing resistance try swapping the leads and now it should be discharging or the valve dropping, this is a crude test but it will point out a bad cap in most cases. Other things to look at, of the cap is bulging at the top or bottom or both even if it reads good it's time to change it I just had a 5/55 fail to start a unit this week measured the cap it showed good but then I noticed the top was really bulged, I replaced the cap 15$ if you can wait and get it on line or 2x from a local parts house. Make sure the voltage is the same or higher on the new cap, you want the same capacitor values but if you can not find the correct one one with a value within 10% will usually work fine. The 5/55 on the cap I just changed is 5 micro fared and 55 micro fared and the voltage was listed as 400v  that is a common size so the parts house had it. I installed the new cap making sure the strap was tight and not over the size info (if the name and size can get worn off I write them on the case or inside the unit so the next time it is available). Depending in the age of the unit I might change out the contactor a bad starting cap can cause damage to the contactor, so if it's an old unit or a really cheap contactor it's only another 20$ to do this now and will prevent call backs. Once the covers are back in place it's ready to see if this did the trick.
I am mentioning this next part because many times I think a low charge has caused harder starts wiping the cap out. I have found more than 50% of the time when changing a cap the super heat and sub cooling values are off (loss of some of the charge) I will add as needed to bring the system back up to the proper temperature/pressures and double check for leaks but almost never find them. The majority of the time it takes 2-6 lbs in residential systems from my experience if the system takes more than this I can usually find a leak or the system is very old and has not been serviced since install.
So make sure with the power off to short the terminals of the cap's, if any bulging they need to be replaced, it is much easier to toss a bulged cap than clean up several hundred feet of foil/plastic & oil if the cap blows apart.
Hope that helps and good luck


Investment options for f1 visa students in USA

Question: I am foreign graduate student in USA. I recently completed my undergrad (from USA) and have a bit of money saved up. I know that F1 students cannot work off campus and other business activities such stock trading etc are prohibited as well. I wanted to know if opening an account in an investment management firm like Charles Schwabb or Betterment is allowed. I would not be working but I will still be earning a small interest on my deposits. If that is not allowed, are there any good and legal ways for foreign students to earn a little interest on savings?
Comment: Why do you say stock trading is prohibited? [Provided you have a tax ID number, you should not have a problem.](https://www.quora.com/Can-F-1-visa-holders-invest-in-US-stock-markets)  "Day trading" is probably not an option, but purchasing of shares for investment should be fine.
Answer: There's no limitation on what you can invest in, including trading stocks (as long as trading is not a business activity, like day-trading or investing for others).
You just need to make sure you have a tax ID (either ITIN or SSN) and pay taxes on all the gains and dividends. Also, consider your home country tax laws, since you're still tax resident in your home country (most likely).


What's the difference in baking bread in a loaf pan vs. in a Dutch oven?

Question: When I bake bread, I always use my loaf pan. Recently, I've seen some people who bake bread in a Dutch oven (or something similar). Why is this? What are the differences between the two?
Answer: There's two important distinctions:

The dutch oven is preheated, so the oven conveys a lot of heat, rather quickly.  This causes some steam to be pretty much immediately made.
The dutch oven is covered.  This traps the steam previously made.  This is trying to replicate steam injection and the goal of most methods that cover the loaf.

Steam keeps the crust from hardening and promotes better oven spring and crisper crust.  The steam basically allows the bread to 'swell' more in the oven.  Steam also gelatinizes the starches in the crust and formes a better 'shine' and 'crisp' on the finished product.  The dutch oven is then uncovered after awhile and the crust hardens.
Comment: Protip: Don't forget the uncovering part >.>
Answer: In addition to rfusca's quality points, the dutch oven is very helpful for eliminating hot spots in the oven, leading to a more even rise across the loaf.
Answer: Another difference is shape. A loaf pan directs the dough into a specific shape as it cooks (and as the oven spring makes it expand), while loaves cooked in a dutch oven are free to expand outward. This results in a lower, broader loaf.
I believe that the loaf pan's restriction may also result in a tighter crumb, and I would be grateful to anyone who can confirm or refute this.


Eliminating STPP taste in seafood

Question: All of the IQF shrimp in local stores contain sodium tripolyphosphate. I am apparently very sensitive to the taste, or at least more so than my family members. It renders these shrimp inedible to me. Is there anything that I could marinade the shrimp in to possibly reduce some of the taste?
Comment: Out of curiosity - what does it taste like?
Comment: @logophobe It is almost a smell, not a taste, so very strong seasoning can mask it, but I describe it as tasting the way laundry bleach smells. I've had fish with STPP in it, and I don't taste it; I only taste it in shrimp, but never in fresh shrimp.
Comment: ...I can see why that would be extremely offputting!
Answer: Shrimp can have up to 0.25% STPP, fish even more!
STPP reacts with calcium or magnesium salts. These are commonly found in pool PH buffers, or as gypsum (food grade gypsum is used as a tofu coagulant)
1 Kg of shrimp could have up to 2.5g of STPP, so a 1/2 tsp of a calcium or magnesium salt dissolved in hot water, and diluted to 1 l, would make a neutralising bath for 1 Kg of shrimp. Leave it in for 10 or 20 minutes and rinse thoroughly
It may also react with citric acid (used in baking), or just use the juice of a small lemon instead
The only problem with this is it may leave a soapy taste

Eliminating STPP taste in seafood


Classical guitar: how to figure out the fingers

Question: how do I play a piece of classical guitar when the fingers (pima) are not indicated, do I just figure it out??
Answer: Playing guitar does not have to involve strict adherence to someone else's ideas about how a piece should be played.  The guitar as an instrument, lends itself quite well to creative interpretation and adaptation.
When someone writes the notation for a piece of guitar music and adds the finger indications (P I M A), those can be treated as "suggestions".  The suggestions often have some merit and might represent the easiest and most efficient way for most guitarist to play the piece.  But you will be playing the same notes regardless of which finger you use.  So if you find it easier to play a particular note with your index finger than your ring finger, you can play it that way - regardless of the "suggested" finger.
So to answer your question - yes.  In the absence of someone notating their suggested fingering, you simply figure out what works for you.  You may see that the notes can be played using a finger picking pattern that you are comfortable playing.  If so, use that pattern.  Typically the bass strings (5th and 6th) will be played with the thumb and the middle and treble strings with the index, middle and ring finger, depending on the pattern.
Some guitarist rarely use their ring finger, preferring to use only the thumb, index, and middle finger and seem to play quite well.  So they would generally ignore any "suggested" fingering that included the ring finger.
You might need to experiment - measure by measure, to see what you are most comfortable with.  Then you can write the P I M A notation yourself if you feel the need to memorialize what you work out.
Good luck and keep it fun.  And don't be afraid to experiment.
Comment: Certainly agree with your first statement. That's where tab is a let down - it's doing exactly that - someone's idea of how something should be played. Not PIMA, but a similar concept (or misconcept?)
Comment: @tim I suppose it depends if they've watched a video of the music's composor and got a note-by-note transposition, or just made it up!
Comment: @Mr.Boy  Even a direct transcript from the original composer is nothing more than his/her idea of how it should be played.  Does not make it right or wrong, or mean that someone else can't improve upon it.  Jason Mraz totally changed the way he plays the song I'm Yours because some kid on YouTube did a cover and showed him a much better way to play his own song.  He ended up inviting the Kid on stage at a concert to play it.  There are several YouTube vid's about it including some where Jason tells the story about the kid who taught him a better way to play his own song.
Comment: True but that's an exception. If a band is just (not that this is bad) trying to imitate the original artist then the version they do is at the very least a good reference.
Comment: @Mr.Boy True - if your goal is to emulate and sound just like the original artists, then tabs or notation that show what the original artists played it like once is a good reference point.  But original artist often change their arrangements after they start playing them live and discover different ways to play them.  Some rarely play the songs the same way twice.  I personally like to develop my own interpretation of how a song should be played vs. attempting to replicate the original artist.  I know that I will never sound exactly like the original artist so my thing is "why try?".


Is it appropriate to directly ask users to alter their behavior?

Question: Some comments or answers ask users to alter their behavior on Stack Exchange. For example, critics may ask the questioner to modify their question, comment, or answer to fit some particular characteristics the critic has in mind. I understand there are the obvious feedback mechanisms like downvoting and flagging, but is it ever appropriate to act as "Stack Exchange police" and directly ask users in comments or answers to behave differently on Stack Exchange? If so, when, why, and how?
Comment: If we're SE police I better get a Tazer
Comment: There's nothing wrong with nudging users in the right direction provided that the comment is polite and well mannered.
Comment: Timing of this post is aweaome, since Today itself, I was planning to go on a downvote spree on bad-quality/link-only/code-only answers on SO--since nobody else seemed to want to do it :P
Comment: **Yes.** That is what the comments are for. Stack Exchange [is not a forum](http://meta.stackexchange.com/questions/92107/is-stackoverflow-a-forum), [it works differently](http://meta.stackexchange.com/a/128554/156722).
Comment: Possible duplicate (or opposite) of http://meta.stackexchange.com/a/2373/167443
Comment: @Tim I do this daily. Don't feel left out.
Comment: @TheE It's easier for you, you have extra rep over 20k. I don't care much about privs on SO, but I'd like to keep my 500rep abilities :). So I'll earn rep, burn it, earn, burn, and so on ;-)
Comment: @Tim Ah, in that case, you could just leave `-1 blah blah blah` comments. [Just the *thought* of being downvoted is enough to make some people cry themselves to sleep at night](http://meta.stackexchange.com/questions/132719/warn-when-downvoting-newbies). It should send a powerful enough message ([coupled with some constructive advice](http://stackapps.com/questions/2116/autoreviewcomments-pro-forma-comments-for-se)), without costing you any rep.
Comment: @theE good idea, but I think burning rep is fun on SO.. I'm not really planning on posting a lot there, and it's too hectic for me (so extra privs won't help me much) Yesterday I got 100 SO rep just because I asked for clarification of policies wrt an answer of mine here on MSO. I plan to have fun using up 50 downvotes :D. Yeah, commenting will be a given, at any rate.
Answer: In general, yes. That's called "Community moderation" . Telling users that so-and-so is discouraged/against the rules is a good thing. We work differently from a forum, and this is what comments are for--to help others improve their post(s).
The cases you're talking about may be different, it looks like you're talking about people who are being over-nitpicky. Examples please?
If you see something you don't quite like in a comment, flag it. If it gets declined, the decline reason may be informative (you can see a list of your flags if you click the number next to "helpful flags" on your profile)
Comment: This is especially true for new users who may not be aware that SE is different from a forum (as noted by @Ephraim), that community standards require you to "be nice," that saying "thanks" is best done by upvoting, etc. etc.  A lot of this stuff is not intuitive and people may need help figuring it out.
Comment: @Scott the whole engine is nonintuitive :P Good point though, added a bit.
Answer: Stack Exchange is actually pretty complicated, and we have pretty high quality standards. SE really doesn't work without this sort of community moderation. The FAQ can't explain everything nor can moderators; there are too many users and too many things to explain everything to everyone unless the whole community is involved.
When a user doesn't quite "get" how something works or should works on Stack Exchange, you help them and the community by nudging them in the right direction in a polite and civil manner. It's not "policing" or "changing their behavior" so much as it is teaching them.
Answer: YES.
If users are asking questions that are out of line with the StackExchange model (such as gimme teh codez questions or broad, subjective, discussion-oriented questions), they are going to get a lot of downvotes, closures, and deleted questions.
If left unchecked, this will lead to clutter of things the rest of us don't want, and the user will likely get question-banned.
It is best to let users know what they are doing wrong, why that particular is not a good fit for the site, and what they can do to improve. This leads to less garbage content, more acceptable content, and the user not getting question-banned.

As for the "when, why, and how" (or at least the when and how, since I believe I've covered the why), comment on their post and politely explain the reason their content is not appropriate, and (if possible) suggest how it might be fixed. Alternately, depending on your reason for needing to direct their behavior, you could directly edit the post, and then leave a comment (or use the edit summary) to explain why you made the edit.
Lasty, the when. Whenever you see content in need of improvement.  Seriously. If it needs a fix, or a user needs some advice, step in and lend a hand before they get barraged with downvotes or question-banned..
Comment: Definitely *lead by example* when possible. Trying to describe to someone how they should edit their post is far less efficient than simply making the edits and then explaining why. Of course, that's not always possible... But when it is, jump on it.
Comment: [Further reading](http://meta.stackexchange.com/q/135/167443)


Google Chrome Helper Using Up Too Much Memory

Question:
Google Chrome Helper is appearing in Activity Monitor a dozen times and overall using a ton of memory.  How do I curtail this?  Most advice columns say to go to my plugins and check "Play on click", but Google updated the browser and this option is no longer available.  What can I do?
Comment: Each "helper" is an open web page/tab. None of those are truly excessive, though definitely a bit heavy. Chrome is a well-known [anecdotally] memory-hog. Your 'fix' is to not leave tabs open if you aren't using them, unless you have sufficient RAM to spare.
Comment: Access the Chrome task manager: **More** (icon on top right) > **More Tools** > **Task Manager** to see which of your tabs are using memory and where you can also end process for tab.
Comment: idk, but they do. I have tabs open here varying between 50MB & 1GB. Google's 'helpers' don't actually help you much as they don't include the URL. If you try the same in Safari you can at least see which tab is using the most [or site, as the URL is just the top level].
Comment: Is there another way?  How can 1 tab be using half a gig of memory?  That makes 0 sense!
Answer: Every "Helper" is either a tab, a subframe, a core Chrome process or an extension.
You could reduce RAM usage by uninstalling extensions, or just using less tabs.
Answer: I figured it out. It was eating up over 300% of my mac's memory and making my computer heat up like an oven even though I've only had it for a few months. To solve this I opened Activity Manager (located in the utilities folder in the applications), and control-clicked on the google chrome helper until I got a window (had to double click). At the bottom of the window there was a quit button and I clicked it and it closed it out and my chrome still works fine.
Answer: I have quite a good experience with this "Google Chrome Helper" and how to debug the notorious problems on Mac.
1. CHROME EXTENSION
In this case go to the 3 dots you find on the right upper side of your browser and then More Tools > Extensions, here you can have an overview of all your extensions.
Deactivate all of them and relaunch Chrome.
If the issue is resolved we can now point out that the issue was related to one of your Extension. But what extension? You can now reactivate one by one while you have your Activity Monitor open and see when the "Google Chrome Helper" is trigged.
2. CHROME EXTENSION OR CHROME SYNC
Sometimes you can find the Chrome extension that is draining your CPU but you have to work and keep that Chrome Extension available. Or maybe that Extension is managed by your Company and you cannot disable it.
In this case you have to click on your Chrome account on your browser and sigh out from all of your Accounts.
Now close your browser, reopen it and "Google Chrome Helper" shouldn't bother you at all. Well, this is normal, because you are not signed in. Now Sign in into Gmail but don't never ever click on the "Turn on sync..." button

Now you can also install the Chrome Extension that was giving you pain and you shouldn't experience any problem. Just don't touch that "Turn on sync..." button.
3. I STILL HAVE PROBLEMS
Well, in this case you are facing something I haven't faced myself. The only suggest you I can give you is to debug the issue by yourself. When the CPU is spiking high open the Activity Monitor and target the "Google Chrome Helper", look at that line and take the PID number (in the picture that you can see in the question is 29048).
Now open a terminal and run:
killall -9 29048
This way you have now killed the process itself. Try to spot what has changed in your Chrome: maybe an Extension has been deactivated, maybe a tab was closed, maybe a webpage has become unresponsive. Dig and you will find the solution.
Answer: You NEED to disable Flash in Chrome preferences/advanced/content.


The Khan's impression of Marco's description of his desert

Question: During the TV-show Marco Polo, when the Khan asks for the Polo's description of his desert, they gave a bland and stunted account, describing it as a "sea of death" and finding not a bird in sight. It seemed to offend the  Khan until Marco gave a more flowery and detailed description of his desert. Why did the Khan ask for the Polo's to describe his desert?
Answer:
As for you merchants you crossed ocean and mountain the great Takla
  Makan Desert. One not many men survive. Describe for me my desert,
  hmm?

I can think of three possibilities, which repeat in a subsequent scene, probably with similar motivations:

Basic curiosity and information gathering for the court -- the Mongolian Empire was so vast that he may never have personally been so far West (the journey would take 3 years each way).
A test of their respect for his empire and their gratitude for his gracious license to open trade deals on his Silkroad -- when Marco's father and uncle described his desert, his land, his empire, as a "sea of death," the Great Khan was visibly irritated. Marco recognized this and quickly launched into a poetic, favorable description.
To assess the merchants' intelligence -- based on Marco's eloquence, Lord Kublai complimented him, says he has a "clever mind".

After Marco is secured, he is asked again:

When you and your father crossed Central Asia you passed through
  Badakhshãân. Describe for me, in the way that you do how you made the
  passage, what you saw.

Kublai is snacking on the throne, and possibly desired some
entertainment and distraction from his worries by satisfying his
curiosities.
A test of his new subject's powers of perception -- he intended to
use Marco to gather intelligence from an objective source; we hear
the recurring phrase, "Report to me what you saw as you saw it"), as
he knew his courtiers didn't always paint an accurate picture.
A way to ascertain whether Marco was now going to show respect,
another test he almost failed -- and in a way, Marco was testing
Kublai, too -- but he instantly acquiesces following the order to
"stuff his mouth with the shit of pigs." If Marco thought he would
be set free if he acted impudently, he immediately realizes his
miscalculation.


Archiving classes into non-accessible packages

Question: hello I've an android application created in Eclipse ,
 i want to convert the solution into archive so no one can use this code if i give it to him.
I've searched Google on how to do such thing , but I've found nothing
is there a way to do this ??!
Answer: Convert your source code to a jar and use it in your Android Project.
Check this post How to create jar for Android Library Project
Step #1: Create a regular Android library project, and get it working.
Step #2: Copy that Android library project into another directory.
Step #3: Create a JAR from the compiled Java classes from the original Android library project, and put that JAR in the libs/ directory of the copy you made in Step #2. You should be able to run ProGuard on this JAR manually, though I haven't tried that.
Step #4: Remove everything inside the src/ directory of the copied library project, leaving behind and empty src/ directory.
Step #5: ZIP up or otherwise distribute the copied Android library project.
This will give you an Android library project like the Play Services one, where the resources are available, but the source code is not.


Multiple edit of a database table in one form

Question: ok heres my problem.
I have a database table that i want to edit multiple rows by using one form.
I am looking for a way to be able to display a form in which i will be able to edit the rows and save the entries in a grid view kind of way.
Can this be done by dynamically letting the user choose which fields he wants to edit or provide an excel sheet kind of interface where changes are made and saved to this already existing database table.
Answer: Using PHP, if you name the form fields as nameoffield[] they will arrive in the request back to the server as an array. Just make sure empty fields have some place holder when they get sent back to the server and just parse through them one by one performing updates/inserts as necessary.


Do two moral values exist, such that both imply the other?

Question: Two moral values exist, such that one implies the other. Example: "One should be nice" -> "One should not kill".
Do two moral values exist, such that both imply the other? Would two such moral values be exactly equal, making a differentiation of the morals meaningless?
Comment: You mean a differentiation between those two mutually indicative moral values, right?
Comment: yes, that's what i mean
Answer: That's an excellent question and I don't know of any article or other reference about it. AFAIK, there should be such two values, although in the end it all hinges on what you call a value and whether you think that the use of implications is appropriate in this context. Why should there be such pairs of values?
Take any common variety of goodness like e.g. medical goodness or hedonic goodness, and a statement like (1) that can be read in that way:
(1) This apple is good.
Then it seems that we should be able to give explanations like (1) means
(2) This apple is healthy for you right now.
or
(3) This apple gives me pleasure right now.
But this, it seems, essentially means that something is good in the medical sense of 'good' if and only if it is healthy to you, and that something is good in the hedonic sense of 'good' if and only if it gives you pleasure. So here you have your biconditionals.
However, there are numerous problems with this view. One of them is that one could argue that it confuses synonymy with explication. Logical positvists like Carnap and Ayer were careful to keep the two apart and not to conflate explication with statements of synonmy. Perhaps the biconditional (in the sense of "material implication in both directions") is not the right way to think about problems of value equivalence. Still, any intuitively understandable variety of goodness should have a corresponding explanation that can (to some extent) be substituted for it.
Another problem is whether you are willing to call different meanings of "good" values at all - "good" seems to be a very special case. Perhaps it always combines different (real, underlying) values as a sort of shortcut.
Comment: Nice answer! Welcome to philosophy.SE!
Answer: i'm not sure what you mean, but i can't "comment" so will "answer".
of course if i ought not kill homo sapiens i ought not kill humans... likewise if i am obliged to honour my mother and father then i am obliged to honour mr and mrs user [and visa versa]; this is a less trivial moral equivalence.
being nice and not killing, could be one and is more interesting because it seems that being nice does not necessarily contain not murdering... and if that can be shown, that it is possible to be a nice murderer [or to murder nicely], then it seems to me that they cannot strictly imply each other.
we might also ask: what about other forms of inference? perhaps i can justify the claim that murder is not nice by confirming all the cases of nasty murders; then even if a nice murder is only contingently impossible it is still so [and we can go the other way too: all the nice deeds that aren't murders].
so it seems to me that yes obligations can entail each other - by a priori, or by a posteriori necessity, or by less strict inference.
which may go some way to answering your question, at least the best I can do without knowing why you ask
Comment: not sure this answers the question.
Comment: i don't really understand what "differentiation" means here. obviously don't kill your parents and don't kill your mum and dad say the same thing. but practically speaking, anyone who struggles to realize that probably does need reminding of both
Comment: the question is about circular implying :-  be nice implies don't kill, but don't kill doesn't imply being nice.  So that's not an example of circular implying.  That example is given as something that is NOT an example of what the question is looking for


Can this frame be used or is it done?

Question: I have a cheap mens Huffy mountain bike which I noticed has 2 holes in the frame. Would this be too unsafe to ride?
Comment: I've seen worse (including one -- still ridden -- with a broken downtube), but it's unreliable at best and certainly not worth spending money on.
Answer: If it were mine I wouldn't ride. It appears there is a crack connecting the two holes. This would indicate there has been enough flex to cause the frame to crack.
Answer: I wouldn't chance it. The entire frame appears to be extremely rusty.
Comment: Agree. I can stand the two holes, but seeing them -and- the rusty collarbone around the headtube makes a scary ensemble ...
Answer: The fork does not seem aligned with the headtube. So, yes, the bike is unsafe to ride.
If by chance the fork is straight, the two holes you see there are just a sign of what can happen to the other spots rusting here and there on the frame.
And they are in dangerous positions.
Finally: think about yourself sprinting through an intersection (possibly green-turning-yellow traffic light), the frame cracks and your bike comes to a sudden stop (frame hitting rear wheel, rear wheel locking). It is not dangerous, as long as a truck is not coasting for the red-turning-green traffic light in the other direction ...
Answer: Bike frame is the main part of the bike, this rusty bike frame can't ensure your riding security. Even if you replace other components, it also is a very dangerous thing whlie you riding this bike on the road.
Comment: I agree but this doesn't seem to add anything to the existing answers.

Can this frame be used or is it done?


What was the importance of the ISOs in Tron: Legacy?

Question: I never really understood what the movie said about what makes the ISOs special.  Flynn found them to be something amazing, but I don't think the movie made it clear what made them even more fantastic than the grid.  Can someone clarify what the importance of the ISOs is?
Answer: The ISOs were a spontaneous artificial lifeform - which is pretty spectacular... And then these lifeforms appeared to have the power to help solve a lot of problems:
http://en.wikipedia.org/wiki/Tron:_Legacy#Plot

Flynn discovered a new series of sentient "isomorphic algorithms" (ISOs), self-produced Programs that spontaneously evolved in the system, which carried the potential to unlock mysteries in science, religion, and medicine.

http://tron.wikia.com/wiki/ISO

ISOs differ from standard programs with distinctions in their appearance and capabilities, but where they are truly unique is in their code base. While regular programs conform to the rigid structure defined by their users, ISOs have evolved, complete with a genetic code of sorts that even Kevin Flynn can scarcely comprehend. This inner structure of their code has allowed ISOs to develop beyond the capabilities of regular programs.
Comment: From what I remember about the lore of Tron, the non ISO programs are not spontaneous - they're all programmed by users, but happen to reside in the grid...
Comment: @HorusKol is correct.  The other programs in Tron and Legacy were all *written* by someone.  The ISOs are emergent AIs; they appear of their own accord.  That's pretty incredible.
Comment: But aren't the programs in the Grid already artificial life?  So the thing that's special about the ISOs is that they're more artificial?
Comment: Apparently, what makes ISOs special is that they can walk off the grid just like a User.
Comment: Not so special - wasn't Clu able to go off the grid (and his entourage - although they were probably just attached to him)
Answer: Canon:
Flynn says that everything that man knows is up for grabs, that the ISOs were infinitely wise and infinitely naive, and mentions bio-digital jazz.
Speculation:
Basically the ISOs seem to be missing that humans have, my guess is that they know nothing of the world and are like children, i.e. not jaded by life. As such, they have an unclouded view of things and generally want to be able to change things to make life better (as seen in the newest Tron game).
Also, the ISOs have a TRIPLE helix DNA strand. This might explain how the ISOs could change medicine.
Not to mention, bringing beings who spontaneously generated inside a computer, and having proof of this fact (REALLY hard to fake a triple helix of DNA in a person) into the physical world would cause one hell of stir;throwing out a lot of what we know, philosophy, religions (imagine the reaction of Creationists) and medicine.
Edit:
The field of computer science, which I am studying, would be all over the ISOs, the Grid and so much relating to the ISOs just trying to gain a glimmer of what brought about the ISOs. IF humanity could find out how to create digital life, humanity would experience it's greatest renaissance:
-AI could actually be attainable.
-People with terminal illness could be brought into the grid and healed (as Quorra's arm was) because code is much easier to fix than cancer or AIDS or diabetes.
-All forms of research could be done in a few days rather than years via the time dilated effect the grid has.
Flynn was right to say that the revelation of the ISOs and the Grid to the world could do so much for humanity.
Answer: Programs are created by humans. And the ISOs' were a form of technological evolution congruent to the evolution of life here, but with more of a twist after that gets more technical. Once you think about it genetic algorithms cannot be all theory. "Fiction" can never truly be proved as just imaginative thoughts. Technology is constantly evolving and one day it will catch up to us (sooner than we know) and then it will pass us.
Answer: Isomorphic algorithms alter themselves as per the input parameters to give a final output. Its very helpful since the procedure changes by itself to giv a definite output. Diseases can be broken down and remedies can b created, complex relation btwn religion n science can b solved. In short, isos r believed to b t ultimate answering machines, according t Flynn.
Answer: all the other programs on the grid were designed to be perfect. so they are destroyed once there's a flaw in their code (e.g. getting hit by the disc). isos on the other hand were not designed to be perfect so they're not destroyed with a single flaw. they just won't function properly (quora in the end of line club)
Comment: This answer doesn't address the question asked.
Comment: Also, for the record, ISOs weren't "designed" at all. They were an emergent phenomenon.


Writing a simple 12-tone row

Question: A few days ago my instructor taught me the basis of the twelve-tone system and taught me how to write a dodecaphonic row and its retrograde, inversion, and the inversion of retrograde. Now I have no more classes with him for a few months and he is not reachable. One thing I am confused about is that he said in the basic row there shouldn't be a formation that represents any known chords. What does that mean? How can I write the simplest dodecaphonic row that follows this principle? Does that mean that each time I write a dodecaphonic row I should check each three adjacent rows and see whether they form a 'known' chord? What does that 'known' chord refer to?
Answer: It sounds like your teacher is asking you to write a row without any inherent tonal qualities. We're not looking at three adjacent rows here, but rather tones that are next to each other within a single row. Take, for instance, this 12-tone row from Berg's Violin Concerto:

Notice that the first three pitches spell a G-minor triad; pitches 3--5 spell a D-major chord that becomes a D7 when you include the next pitch, and so the first 6 pitches spell i--V7 in G minor! (You can find more triads to, if you keep looking.)
So when your teacher tells you not to represent any known chords, he's telling you not to do what Berg did! Instead, he's asking you to do something more like Webern did in his Op. 30 Variations:

Note that no adjacent pitches create a triad; this is what you're being asked to do.
(PS: You can ignore the other markings on that Webern image!)
Answer: There is nothing wrong with triads in a tone row, and it certainly is not against the rules. Having said that, perhaps your teacher wanted you to experiment with less standard melodies and harmonies.
Keep in mind that because the tone row includes all twelve pitch classes, it can take a lot of work to avoid jarring harmonic transitions if you do employ the common minor and major triads.
And yes, you should check each 3 adjacent rows (or columns, your choice!) and avoid standard major and minor chords, and perhaps diminished triads as well.
Be careful of inversions, as well.

Writing a simple 12-tone row


Minor purchasing alcohol?

Question: In the United Stated, to my understanding, it is illegal for anyone under the age of 21 to purchase, consume, or otherwise be in possession of alcohol. Therefore, would it be illegal if someone who was under 21 (Person A), went to dinner with someone (Person B) over 21 (parents, older relative, date, etc.) and Person B ordered an alcoholic drink and Person A didn't, and when the check came, Person A decided to pick up the tab? Could the police arrest this person and charge him/her with purchase of alcohol by a minor, and subsequently charge Person B with allowing a minor to purchase alcohol (I.e negligence?) And then fine the restaurant for allowing a minor to purchase alcohol?
Comment: This is a fun hypothetical situation to think about; technically it seems like it violates the letter of the rule. Although it'd be hard to think this would actually hold up in court.
Comment: This is regulated by state law.  What state?
Comment: @NateEldredge North Carolina - Interesting. I didn't know that States had their own individual regulations on this.
Comment: Yes, underage drinking has always been a matter of state law.  Every state has 21 as the minimum age to purchase alcohol because of the federal [National Minimum Drinking Age Act](https://en.wikipedia.org/wiki/National_Minimum_Drinking_Age_Act), but the details continue to vary by state.
Answer: The police can arrest and charge anyone if they have a reasonable belief that a crime has been committed so: yes.
However, if the question is: can they secure a conviction the answer is a resounding no.
North Carolina law has three prohibitions on minors and alcohol: supplying to, possession of and buying.

Possession is easily dealt with: the minor never possessed the alcohol.
Supplying is also dealt with perfunctorily: the supply went from the restaurant to a person 21 or over.
This only leaves buying. Now, buying something requires a contract (or since the object is illegal, what would be a contract but for that). Did the minor have a contract with anyone? That is, were they under an obligation to pay for the alcohol? No. If the pair had skipped out on the bill, the restaurant would pursue the adult for payment because that is who they have a contract with. Any arrangement between the diners as to how they will split the bill is a private, unenforceable arrangement, not a contract.
Comment: I think you reach the right conclusion, but I'm not convinced that the reasoning is correct or at least so clear. Certainly someone age 20 could enter into a binding contract but not purchase alcohol, and I'm not even convinced that the 20 year old couldn't be bound to pay the bill jointly with his dining companion. The answer in this context, I think is that buying and financing are viewed as distinct acts in light of the purpose of the law.
Comment: But what if the under 21 person had reached majority? E.g. someone who is 18 is a full adult, and can form a full legal and binding contract.
Comment: An interesting situation leads on from this. If the person over 21 who consumed the alcohol left half way through the meal and the other person (aged 18-20) remained for another 2 courses. Could the restaurant legally present the check at all? Would they remove the charge for the alcohol and present a modified check?

Minor purchasing alcohol?


Can we say that bosons attract each other?

Question: We know that bosons donot follow Pauli exclusion principle, thus they can occupy the same state. But is it equivalent to say that bosons attract each other?
Comment: Related: https://physics.stackexchange.com/q/160104/
Answer: Using a statistical physics approach, you can indeed show that the properties of bosons and fermions result in an effective potential that is attractive for bosons and repulsive for fermions:
In a statistical mechanics framework, you can construct the partition functions for both classical, interacting particles in a potential $V$
$$Z_N=\frac{1}{N!} \bigg( \frac{V}{\lambda^3} \bigg)^N \int \frac{\mathrm{d}^{3N}q}{V^N}e^{ -\beta \sum_{i<j}V(\vec{q_i}-\vec{q_j}) } $$
If we now do the same for quantum gases, we get
$$Z_N \approx \frac{1}{N!} \bigg( \frac{V}{\lambda^3} \bigg)^N \int \frac{\mathrm{d}^{3N}q}{V^N}e^{ -\beta \sum_{i<j}V^S(\vec{q_i}-\vec{q_j}) } $$

Comparing these two equations, we see that the statistics of bosons
  and fermions express themselves as an effective potential under a
  configurational integral. This we call the statistical interaction
  $$V^S(q)= -k_BT \log (1 \pm e^{-2 \pi (q/\lambda)^2}) $$
  with the thermal de-Broglie wavelength $\lambda=\sqrt{\frac{2 \pi \hbar^2}{mk_BT}}$ giving the range of the interaction.

The effective potential, attractive for Bosons ("B") and repulsive for Fermions ("F") is shown below. Note, that this "potential" follows only from the statistical properties of the particles.
For a detailed derivation, I recommend Huang's Statistical Mechanics textbook, Figure 9.3 and onwards.
Answer: Saying that bosons attract each other would require a careful analysis of what do we mean by attraction. In classical physics (and in everyday life), attraction between two subsystems implies the existence of some force which makes more probable to find the two  subsystem close each other rather than distant. Thus, the presence of an attraction is accompanied by an increase of the pair correlation at short distances with respect to the uncorrelated case. The other way for repulsion.
Quantum systems display a peculiar behavior of pair correlations which does not originate from interactions but from the symmetry or antisymmetry of the wavefunctions. Short range correlation between bosons is always higher than what would result from the interaction only, so it is tempting to interpret it as resulting from a physical attraction, even though no attractive term is actually present in the hamiltonian.
At the lowest perturbative level, it is even possible to obtain an expression for an attractive potential (see Wasserwaage's answer) but one has to take into account that it cannot be used in a consistent way in a non-perturbative case.
Answer: No. When we say that two particles "attract," we usually mean that there is some intermediary field causing the attraction, i.e. a "force carrier." You can easily make theoretical models of bosons which do not attract. (These would be called "free particles.") However, sometimes people say that bosons "like to be together." This is because it takes less energy to put bosons "near" each other than fermions. However, that doesn't mean they attract. You could make fermions attractive or bosons repulsive by tweaking the intermediary force carrier. It's just that, all else being equal, bosons take less energy to put next to each other than fermions. So while there might be a fuzzy sense in which bosons "attract," I would say that this is an abuse of language that mostly just causes extra confusion.


Is there an update to AuthorizeNet.php with SHA-512 to replace MD5 check?

Question: Is there an SHA-512 replacement for the AuthorizeNet.php module yet? If not I can work on it
Comment: You might want to follow https://lab.civicrm.org/dev/financial/issues/39
Answer: Lesley, CiviCRM 5.11.0 doesn't use anymore MD5 check on authorize.net. This PR removes the check. However there is still not PR submitted by anyone to support SHA-512 check.
If you can submit a PR to support this would be very useful to the community.
Cheers
Pradeep
Comment: Hi Pradeep I can work on it - it would be a patch that would need to also allow Admin/Process Payment form to input SHA-512 key, not just update AuthorizeNet.php. In the meantime, thank for pointing out the latest pull request.
Comment: I have submitted fixes in the past using Issue Tracker, and I see that now Civicrm is using Gitlab, not JIra, etc.  I 'joined'/registered, but now, do I need to 'request' joining a group? Can I not simply submit this as an issue for review, this is an update, not an extension. Can you send me the url I need to go to 1) submit this change as an issue and 2) git clone the latest release?
Comment: https://docs.civicrm.org/dev/en/latest/core/contributing/


Robust stream cipher using AES encryption block

Question: I am implementing a stream cipher in a microcontroller that only has an AES128 encryption block. According to this page, a block cipher based on an encryption only module can be converted into a stream cipher using CFB, OFB and CTR modes. Assuming I have a unique IV, which is the most robust method to use?
Answer: You should use CTR mode. You will not need to have random IV every time, rather you will use incremental counter and set it to zero once you change the KEY. You should not encrypt more than ${2^{n/2}}$ blocks.
CTR mode allows both parallel encryption and decryption without padding. You can even precompute the CTR encryptions in Idle time and just Xor it with input stream to generate ciphertext once required.
OFB mode have cyclic issue and if cycle is small, the generated key stream will start repeating itself.
In fact you should use GCM to get authenticated encryption. see Disadvantages of various Authenticated modes of Operation or how to choose between CCM and GCM
Here is a List of Advantages and Disadvantages of Modes of Operation
For good comparison of mode of operations, please see
Evaluation of Some Blockcipher Modes of Operation
Comment: When only AES is accelerated on a not-so-fast microcontroller I would consider AES in CCM or EAX mode before GCM mode.
Comment: This is a morning comment, so I had it wrong first; AES-CBC is not an option then and you should rely on CTR. As CBC-MAC and therefore CMAC, CCM and EAX only use AES in one direction it seems they are still available.
Comment: I think he has only block encryption available. so cant use CBC or CC mode of operation. moreover CCM wil use two 2xblock encryptions for each block
Comment: With block encryption you can implement any mode. The GMAC component of GCM requires a 128 bit multiplication per block so if you've got a constrained CPU it may still be relatively slow and possibly slower than the double AES if that has been accelerated. Testing is the only real way to be sure.
Comment: can we implement CBC mode decryption once AES decryption block is not available? or does the AES encryption block availability means it can perform both Encryption and Decryption?
Comment: The AES block can only perform encryption, not decryption.
Comment: @mr_js so there is no possibility of using CBC mode.
Comment: It would seem not, since this relies on the AES decryption block.


Creating artificial mitochondria to power nanobots

Question: To power nanobots, we are trying to create artificial mitochondria that's small enough to fit in these nanobots.  But we are not sure of how to make these artificial mitochondria, which we imagine wouldn't be as simple as replicating the original mitochondria with mechanical parts.  What's the best way of doing this? Edit: the there was an answer where we should use natural mitochondria, but it would be too large to fit in the nanobot, the nanobot is about the size of synapses.
Comment: You could maybe use something like the proposed method of powering [respirocytes](https://en.wikipedia.org/wiki/Respirocyte).
Comment: Are these nanobots powered by [adenosine triphosphate](https://en.wikipedia.org/wiki/Adenosine_triphosphate)? Mitochondria are specially adapted to support living, eukaryotic cells. They are not general-purpose power-generators.
Comment: It would run on electricity, something like sugar fueled bio battery.
Comment: @XIAOLONGGAO Mitochondria do not generate electricity.
Comment: I'm sorry, I meant as nano sized sugars battery that convert chemical energy of sugar to electricity using cathode pathway and enzymes.
Comment: Are you asking for a research process to figure out how to build these? Or are you asking for the best hypothesis available today about how they would work?
Comment: Best hypothesis today, we just need a theoretical ideas that's plausible.
Comment: Related [How to power the nanobots](http://worldbuilding.stackexchange.com/questions/35975/how-do-you-power-all-the-nanobots?rq=1)
Comment: @ApproachingDarknessFish That's not exactly true. The mitochondria creates an electrochemical gradient that it then uses to phosphorylate ADP into ATP. But as a result there is a voltage or electrical potential across the inner membrane of mitochondria.
Comment: Note: this is considered a hard question in today's science.  We're still trying to to figure these things out.  However, worth noting is just how small you are talking about.  A glucose molecule is about 1nm in diameter.  That means that, if you want to use sugar as a food source, you're only about 60x larger than your foodstock.
Answer: Just use natural (possibly tweaked) mitochondria.  They are perfectly fine nanomachines already, and (because the dangerous reactions need to be sequestered) are already fairly stand-alone independent units.
If your nanobot tech is powered by ATP, it probably is already borrowing heavily from natural life.  Why do you need to engineer a different device to burn sugar and charge up ADP→ATP?
Comment: Why reinvent the wheel? Nature does a so much better job at it than mere mortals. No intellectual property restrictions either. What else is biology but nanotechnology implemented on a large scale, running on conglomerations of so-called organic chemicals?
Comment: Thanks for the answer, but natural mitochondria would be too big to fit in the nanobots (the nanobots are about 60nm by 60 nm).
Comment: You should update the question.
Answer: The Mitochondria pretty much already works on a atomic level, you can "build" a smaller one of course. But if you make a new mitochondira half the size of the ones you find in Eukaryotic cells you'll also have half the energy production.
I think using genetic engineering to decrease the amount of internal membranes wil be relatively straightforward. Like I said, these membranes is where energy is produced in the form of ATP.
I have one note, Mitochondria 'burn' things to charge up their ATP's (mostly sugar) this isn't really a resource that is traditionally around nanobots, so unless these nanobots only survive leeching off of biological systems it may be an idea to base its energy production of Photo or Chemosynthesis instead.
Answer: If you're trying to power nanobots, using an entire artificial mitochondria would probably defeat the purpose of using nanotech. If you want a nanobot to make ATP from glucose you technically don't need a mitochondria. Upon entering a cell, glucose is first processed through the glycolysis pathway with produces some ATP and some products that enter to mitochondria to make additional ATP. The mitochondria makes a lot more ATP, but cells (or nanotech) can run without them. For example, the mitochondria of many cancers are too damaged to function and they get all their ATP from glycolysis. Also, when you do cardio and you have low oxygen levels in your muscle tissue, mitochondria can't work right so your cells just use glycolysis. (but in that case, you also get a buildup of lactic acid, which is the cause of muscle fatigue, that has to be cleared from the system)
However, if you're hell bent on using a mitochondria-like system, the minimal components you would require are the initial glycolysis pathway, the TCA cycle enzymes, a lipid membrane (for the separation of high and low hydrogen ion concentrations), the electron transport chain enzymes (that sit in the membrane), and the ATP synthase enzyme (that also sits in the membrane), and lots of oxygen (as an electron sink for the electron chain transport).
Although, if I was building nanotech in the brain (as your synapse comment suggests) why not just use the same voltage potential that neurons use? There are a ton of ions in the brain. Just use a voltage gradient between the inside and outside of the nanobot as a battery.


Difference between Host record and A record

Question: What is the actual difference between a Host record and an A record? Both points to an IP  so what is the difference?
Answer: There is no such thing as a Host record in the actual DNS specification.  Host records are generally a logical construct in DDI (DNS, DHCP, and IPAM) solutions  like Infoblox and others.  They comprise various DNS record types (A, AAAA, PTR, CNAME, etc) and other metadata associated with a "host".
Answer: As others have stated, there is no such thing as a "host" record in the DNS specification. Most people confuse hostnames and DNS records because DNS is frequently used to store the relationships between hostnames and IP addresses, represented with A, AAAA, and PTR record types.
DNS is a lot more than that though:

DNS is a widely distributed, hiarchical database that can be used to store any number of things. It just happens to specialize in mapping names to IP addresses and vice versa, because that's what the internet needs most from such a database.
All hostnames are legal DNS labels. (label = the left hand side of a DNS record)
Not all DNS labels are legal hostname entities. This is where people get confused. Wikipedia covers this topic pretty well, but the short version is that there are many characters that will pass a syntax check for DNS that are not legal for use in hostnames. This is a pretty significant hint that DNS is not enslaved to the hostname specifications.

To wrap up and reinforce the above topics, I'm going to drop a hefty wall of text from RFC-2181:

Name syntax

Occasionally it is assumed that the Domain Name System serves only the purpose of mapping Internet host names to data, and mapping Internet addresses to host names.  This is not correct, the DNS is a general (if somewhat limited) hierarchical database, and can store almost any kind of data, for almost any purpose.
The DNS itself places only one restriction on the particular labels that can be used to identify resource records.  That one restriction relates to the length of the label and the full name.  The length of any one label is limited to between 1 and 63 octets.  A full domain name is limited to 255 octets (including the separators).  The zero length full name is defined as representing the root of the DNS tree, and is typically written and displayed as ".".  Those restrictions aside, any binary string whatever can be used as the label of any resource record.  Similarly, any binary string can serve as the value of any record that includes a domain name as some or all of its value (SOA, NS, MX, PTR, CNAME, and any others that may be added).  Implementations of the DNS protocols must not place any restrictions on the labels that can be used.  In particular, DNS servers must not refuse to serve a zone because it contains labels that might not be acceptable to some DNS client programs.  A DNS server may be configurable to issue warnings when loading, or even to refuse to load, a primary zone containing labels that might be considered questionable, however this should not happen by default.
Note however, that the various applications that make use of DNS data can have restrictions imposed on what particular values are acceptable in their environment.  For example, that any binary label can have an MX record does not imply that any binary name can be used as the host part of an e-mail address.  Clients of the DNS can impose whatever restrictions are appropriate to their circumstances on the values they use as keys for DNS lookup requests, and on the values returned by the DNS.  If the client has such restrictions, it is solely responsible for validating the data from the DNS to ensure that it conforms before it makes any use of that data.

The last paragraph is particularly important. The DNS standards are very open ended in terms of what is legal to store within DNS, but other standards can dictate how a service consumes DNS and can impose any limitation on what an application should (and should not) expect to find there. This is exactly so in the case of hostnames, which are defined by RFCs outside of the DNS standards.
Answer: DNS specifies A records as one possible record type. A records are sometimes referred to as host records. They are the same thing, but I would prefer using "A record", since that is what it's officially called.
Did you encounter both concepts in a situation where they seem to mean a different thing? I know Infoblox DNS appliances support the concept of a 'host object', which is a data structure in their configuration which is translated into an A and a PTR record in the DNS server.
Comment: AAAA  would also be a host record.
Answer: A records and AAAA records are "address records" (hence the "A") that map a hostname to an IP address. So, when you create an "A record" for example.com, you map that to an IP address, ex. 22.214.171.124. Because of that hostname -> IP mapping, some people refer to those records as "host records".
AAAA records are the same concept, except for IPv6 128-bit addresses. A records are for IPv4 which are 32-bit addresses.
Answer: Yes, I was dealing with Infoblox.  And you guys were correct - Host Record is an object created by Infoblox to create both A record and PTR record at the same time.
Also individual forwards and reverse lookup also can be created. Though a bit slow while searching a large database, Infoblox is good for a lot of things.
Thank You for the inputs. Learned a lot :)
Comment: "does not allow/create the reverse lookup" - Nope, that's incorrect. Infoblox most definitely does support creating reverse PTR records both directly or virtually via a Host record. In both cases a standard DNS PTR lookup will return the name for that IP.
Comment: @RyanBolger Thank you for pointing out the error. I have corrected my answer.
Answer: The only real differentiation I have encountered between HOST records and A records is within Infoblox Grid Manager.  In that application, you can distinguish between setting up either type of record.
There are a few additional options available when setting up an A record within Infoblox, but as far as the rest of the world is concerned, both records are interpreted exactly the same.


Numerical calculation of the Berry connection

Question: I'm doing some numerical calculations involving Hermitian matrices, and derivatives of the eigenvectors.
Essentially, I have an n x n, Hermitian matrix H(x), which is dependent on some continuous parameter (x). I then need to calculate the Berry connection for this system. So suppose $U^\dagger(x) H(x) U(x) = \epsilon_n \delta_{nm}$, I'm essentially computing $i U^\dagger(x) \partial_x U(x) = \hat{A}$.
To do this, I tried to evaluate $H(x), H(x+\Delta x)$, and obtained $U(x),U(x+\Delta x)$. I therefore approximated $\hat{A} \approx i U^\dagger(x) (U(x+\Delta x )- U(x))/(\Delta x)$. This is carried out in LAPACK, using HEEVD (CHEEVD), since H is Hermitian, and parametrized with double precision.
However, since the diagonalization at every x carries with it a random phase (apparently), the object $\hat{A}$ contains errors, and no longer represents just the derivative of the rotation matrix $U$. In fact, it even turns out to be non-Hermitian at some x points.
I imagine the solution has to be some sort of uniform gauge condition for all $x$, ensuring the smoothness of the connection. Is there anyway to add this, or implement this within LAPACK? I have so far been unsuccessful.
Thanks!
P.S.
Naturally, the Berry connection is not gauge invariant, so it won't directly enter any physical observable. The issue is, however, that errors in the evaluation of $\hat{A}$ propagate directly to observable quantities, like the berry curvature for example. Quantities $i[A,A]$ suddenly contain disallowed imaginary parts, coming in from errors in $\hat{A}$.
Answer: If you want to fix the phase you can refer to the gauge-fixing method adopted by the paper [Journal of the Physical Society of Japan Vol. 74, No. 6, June, 2005, pp. 1674–1677].


What are the options to auto populate metadata for data received from external sources?

Question: We receive quite a many spatial data from various sources and export to our enterprise database (Esri). But no metadata is available in Description table. I am looking for a tool or method to get all the attributes, which can be easily populated from the files e.g. spatial extent, projection etc.
Answer: You could try the "synchronize metadata" tool from the Conversion Toolbox (Metadata Toolset).  It will populate the fields you mention (extent & spatial reference, and more! : attribute list, geometry type, number of objects, ... or number of bands, cell-size & depth for raster, to mention only a few) by reading the data structure, encoding, spatial & geometric features.
When you display a detailed view of the metadata in ArcCatalog, all fields marked with a "*" are synchronized fields, which can be updated by Synchronizing the metadata with the data structure & contents.


Search and Matching model with 2 agents?

Question: I would like to know if you know any model with Search and matching framework (Mortenses-Pisarides style) with 2 types of workers (like Ricardian and rule of thumb consumers for exemple) ? I would like to see such a model featuring different wages, hours worked and unemployment rates between the 2 consumers. In the end I would like to implement such a framework to a DSGE model with Ricardian and rule of thumb consumers. Thank you.
Comment: Do you mean two types of workers?
Comment: I'm not sure about exactly two, but if you google "mortensen pissarides heterogeneous workers," many papers show up.
Comment: Yes that is right.
Answer: I am not sure if this is exactly what you are looking for, but this paper has model that sounds like what you want:
Shimer, Robert, 2006. "On-the-job search and strategic bargaining, "European EconomicReview50, 811—830.
Have a look at this one too:
Shimer, R. (2007). Mismatch. American Economic Review, 97(4), 1074-1101.