What does the "Copy of Record No" field on a naturalization petition index card mean?

Question: I found the following image, and would like to know where it is referring me. What does the line across it mean?
Answer: Working from information Robert Hoare provided in his answer, I found Ancestry.com has two similar, but not identical, collections that include New York's index to naturalization records. The earlier 2007 digitized collection is titled, "New York, Index to Petitions for Naturalization filed in New York City, 1792-1989." The later instance is part of a much larger collection (2010) titled, "U.S. Naturalization Record Indexes, 1791-1992 (Indexed in World Archives Project)."
2007 Collection:
In the earlier digitized collection, I located what seemed the entry/image GeneG had uploaded as part of this question. It cites a particular NARA Northeast Region collection "Soundex Index to Petitions for Naturalization filed in ... New York City, 1792-1989." In this particular digital collection, the 2007 version of the card was indexed as "Michael Dresher."
I searched the Ancestry index for this 2007 digital collections several times; even browsed images, but was unable to find the second referenced card. (Might my soundex be rusty?)
2010 Collection:
In the more recent digitized collection, I was able to locate the two different cards/entries that seem the same records Robert Hoare found.  Graphic below from Ancestry's database, "U. S. Naturalization Record Indexes, 1791-1992 (Indexed in World Archives Project"; cites NARA micropublication/microfilm serial M1674, "Soundex Index to Petitions for Naturalizations Filed in Federal, State, and Local Courts in New York City, 1792-1906," roll 64.
The upper card, which seems more complete, probably appears first on the roll (Ancestry's images 3500-3501); indexed as "Michael Dresouer"). The lower card (images 3502-3503) was indexed as "Michael Dresuer."
Answer: Presumably Volume 38 is a bound volume of naturalization records in the City Court of Brooklyn, and the record of Michael Dresuer was numbered as record 224 in that volume. Your next step is to write to the court with the 38/224 info and ask for a full copy of that record. They may write back and say it has been archived somewhere else and provide you with that info.
The line is labelled as "see" so it is simply referring you to the original record if you want to know who were the witnesses.
Answer: In that image set, there are two cards with that "copy of record no", the one you've shown, and another one that is two images earlier in the set. None of the other images have the same "copy of record no".
The second image has all the normal details that appear on these cards, and almost the same last name as the image in the question.  So it appears that the "<-- See -->" on the image means see the other card with the same number, as that is where the information is to be found.
To put it another way, the card above is a cross-reference card with an alternative name spelling, and it is pointing you to the other more complete card.
The more complete card is the other card with the same record number (that's what links them). The card for Michael Dresouer, on image 3500.  That gives details like the date and witness.  Looking at other records, it's likely that that is all that was on the original.
Comment: The cards are linked to each other by the record number.  I've added a paragraph to the answer.
Comment: Why do you think it would be two images earlier?
Comment: Sorry I wasn't clear, I've reworded my answer.
Comment: +1 Nice. (.....)
Comment: Thanks. I guess that means that there is no info on this card to link it to the other, more complete, card.
Comment: Robert, Is it okay for me to post a composite graphic to your answer?
Comment: GeneJ - go ahead, your answer is more complete.  I didn't realise there were two versions of the collection.  To find the image in the question, I just searched Ancestry for Michael Dresuer and it was it the  first result.  I then browsed a few images back and forth in the image set to get a feel for what it normally contains, and spotted the alternate card.
Answer: On this site displaying a similar image, you will read

Since the index card contained a bundle and record number I knew I could order his naturalization documents from the National Archives. I placed the order online through NARA'S website and for $10 I'd have copies of those records in a few short weeks.

If that is correct, you will not need to refer back to the court because these are NARA reference numbers that can be used directly.
The form itself is intriguing. A Google Image search correctly identifies it as a Naturalization Record, but among the dozens of images considered visually similar this not a very common type. It seems to have been used only in NYC and is distinguished by NOT having the names of any Federal Agencies on it. (Other types are clearly Dept of Labor INS). My guess is that this was a locally produced index card to reference records that had been taken away from the place they were created.


Can you use the Rpi compute module CM4 without the IO board?

Question: I want to use the raspberry pi for some projects, although the normal pi is too big and I want it to be as compact as possible.  I thought about using the compute module(without the IO board) since it is small.  I looked online to see if I could use just the module, but I couldn't find anything that said it was possible.  Is this possible?
Comment: @tlfonh01 Yes, I do too.  I just need the module for the size and the lack of ports.
Comment: #randomuser922, I fully agree with @Andyroo that the I/O board saves you time and money.
Comment: Well, my local E14 shop sells the I/O board for HK$270 (about US$35, with free delivery) is worth my money: CM4 I/O Board datasheet: http://www.farnell.com/datasheets/3160855.pdf
Answer: The IO boards are used to allow simplified software development and easy access to ports while you look at interfacing the Pi into the rest of the hardware.
Once you have completed the hardware / software development it is normal to do away with the board and use the modules themselves - sometimes in a carrier board but sometimes direct to the main circuit board.
The boards do simplify tasks (such as flashing emc with code) but long term are not necessary.
Do you need them from get-go?  No but you have to work out everything before you start (power / connectivity being the two main things) and only then can you get the software development going.  Time savings (therefore money) are significant to use development boards as a steppingstone.
Comment: Do you know how I would use the module  without the IO board?  For instance, how would I power the module?
Comment: That's what you have to design on your board - https://www.raspberrypi.org/documentation/hardware/computemodule/README.md gives many many links power for example is https://datasheets.raspberrypi.org/cm4/cm4-datasheet.pdf#page25  and connectors https://datasheets.raspberrypi.org/cm4/cm4-datasheet.pdf#page15 TBH I think you may have an uphill struggle  if you have never done anything like this as board layout (and line length matching) is a dark art.  Maybe start with https://www.instructables.com/Design-Your-Own-Raspberry-Pi-Compute-Module-PCB/ and build this into your board?
Answer: Question
Can you use Rpi CM4 without IO Board?

Answer
The short answer is NO.
(1) For hobbyist project development, I think the most efficient way is to use the Rpi's official I/O board.
(2) There are a couple of vendors designing "Carrier Boards" for developers and hobbyists, but they are not cheaper than official Rpi.
(3) I am playing with two cheap CM4 modules.  You are welcome to ask @tlfong01 to share his CM4 newbie experiences.

Appendices
Appendix A - The CM4 Modules I Recommend
The official Rpi authorized shop in my city only sells two boards in small quantities, minimum order is 1.  For the rest, you need to order at least 200.  The three boards I am learning is the following.


Commonly used example data sets

Question: Is there a place where one can get standard example data for various statistics tools to try on? For example, if one is learning about ARIMA models, where would one get data that can be modelled well with an ARIMA(2,1,2)x(1,1,1)12 model? Or data for a (5,1,1)x(0,0,0) model? Or multiple linear regression etc? I'm looking for something similar to this:
https://en.wikipedia.org/wiki/Lenna
Answer: There are several different places you could try, but I'll highlight two.
Help Documentation in Statistical Packages
One potentially great and easy-to-access resource is the help documentation in various vignettes in R packages.  Often times the vignettes/documentation come with built in datasets meant to facilitate learning about the procedures contained in the R package.
For example the R package twang is for the development of boosted propensity scores.  If you install the package, open it, and then type the name of a dataset associated with the package inside the "data" function call, you'll be able to see the data:
install.packages('twang')
library(twang)
data(lalonde)
> head(lalonde)
  treat age educ black hispan married nodegree re74 re75       re78
1     1  37   11     1      0       1        1    0    0  9930.0460
2     1  22    9     0      1       0        1    0    0  3595.8940
3     1  30   12     1      0       0        0    0    0 24909.4500
4     1  27   11     1      0       0        1    0    0  7506.1460
5     1  33    8     1      0       0        1    0    0   289.7899
6     1  22    9     1      0       0        1    0    0  4056.4940

How do you get the name of the dataset (in this case, it's called lalonde)?  If you want to see all the datasets in a package, simply type:
try(data(package="packagename"))

where packagename is the name of the package in which you want to look for datasets.  So for the twang example, typing:
try(data(package = "twang") )

opens a prompt that contains the following data sets in package 'twang':
Data sets in package 'twang':

    AOD                     Subset of Alcohol and Other Drug treatment data
    egsingle                US Sustaining Effects study
    iptwExLong              Example data for iptw function (long version)
    iptwExWide              Example data for iptw function (wide version)
    lalonde                 Lalonde's National Supported Work Demonstration
                            data
    lindner                 Lindner Center data on 996 PCI patients
                            analyzed by Kereiakes et al. (2000)
    mnIptwExLong            Example data for iptw function (long version,
                            more than two treatments).
    mnIptwExWide            Example data for iptw function (wide version,
                            more than two treatments)
    raceprofiling           Traffic stop data

If you wanted to see the datasets relevant for learning the rpart package, you'd type:
try(data(package = "rpart") )

and you'd get:
Data sets in package 'rpart':

car.test.frame          Automobile Data from 'Consumer Reports' 1990
car90                   Automobile Data from 'Consumer Reports' 1990
cu.summary              Automobile Data from 'Consumer Reports' 1990
kyphosis                Data on Children who have had Corrective Spinal
                        Surgery
solder                  Soldering of Components on Printed-Circuit
                        Boards
stagec                  Stage C Prostate Cancer

If you then want to obtain a more detailed description of the dataset and its contents, you can simply type the name of the dataset inside the help() function call.  So typing:
help(lalonde)

essentially launches your browser and opens up a description like the one here:  https://rdrr.io/cran/cobalt/man/lalonde.html
UCLA's IDRE
Another great resource for finding datasets relevant to specific analyses is the UCLA's Institute for Digital Research & Education website (IDRE).  The site guides users through different types of analyses and contains hyperlinks directly to datasets relevant to the analyses.
For example, if you wanted to obtain a SAS dataset relevant to Poisson Regression you could click the SAS hyperlink on the IDRE link (see above) and you'll see in the tutorial, a hyperlink to a SAS datset for example 3.
Answer: The U.S. National Institute of Standards and Technology (NIST) has a database online at https://www.itl.nist.gov/div898/strd/nls/nls_main.shtml with both test data sets and associated non-linear regression equations for use in the design and testing of non-linear regression software. Each has example fitted parameters for verification, and there are different levels of difficulty listed. There are also two sets of initial parameter values for for each equation, a "near" and a "far", which are near and far from the reference fitted values for the purpose of testing convergence from different starting points.
The creators of this online regression testing database are aware that in testing, final fitted parameters will not be exactly equal to the listed values and they state that results to within four or five decimal places of their listed values are sufficient.
I personally found these to be of immense value in the design and testing of of my pyeq3 Python fitting library, which is the core of my zunzun.com curve and surface fitting web site. These test equations and associated data sets are what gave me the (statistical) confidence I needed to put the site on the internet in the first place.
Answer: A good way to access data is to actually simulate data for a number of models to learn how to identify latent structure AND then introduce pulses into the data and learn how to identify data like this. Then introduce level/step shifts and/or local time trends and then learn how to identify data like this. Then simulate data where deterministic seasonal pulses are embedded in the data and learn how to identify data like this.
Then simulate data where the model parameters change over time and learn how to identify data like this.
Then simulate data where the error variance changes over time and learn how to identify data like this. Deterministic Error variance change can be detected following TSAY http://docplayer.net/12080848-Outliers-level-shifts-and-variance-changes-in-time-series.html while linkage between the expected value and the error process is remedied by Box_Cox When (and why) should you take the log of a distribution (of numbers)?
Extend this univariate discussion to include exogenous factors that not only are important contemporaneously but with lag effects .
That is what I would do and continuously do to motivate learning by data when no theory is pre-existent and to create robotic solutions to aid analyses.
In all of the above you have the knowledge  of how the data was actually constructed and you can learn about the strengths and weaknesses of alternative identification strategies
Comment: I'm not sure it's the "best" way.  Simulated datasets can often differ dramatically from data found in the real world.  But I agree, that producing simulated datasets can help students understand material, even if it's more time consuming and doesn't necessarily meet the assumptions found in real-life applications.
Comment: I'd recommend changing "The best way..." to perhaps "One method..."  "Best" is subjective and to a new learner, this could sound objective and authoritative.
Comment: I alluded to "real-world complications" being implanted to challenge the trivial solutions that are often proposed.
Answer: Here's a collection of datasets which I occasionally use in my courses:
Epina DataLab repository
The datasets at this site are available both as text files and as IDT files (which is DataLab's internal format, most convenient to be load in Epina DataLab). The datasets are suitable for a wide range of statistiscal methods, such as regression, LDA, PCA, HCA, PLS, etc.

Commonly used example data sets


Current Flowing in Antennas for Radio Signals

Question: How does current flow through antennas to transmit radio signals? From what I know, in order for current to flow, there must be a load across the circuit.
Answer: There IS a load.  Energy radiates from an antenna, so the equivalent circuit for that antenna has an energy-losing element, a resistance.   It doesn't represent an Ohm's Law compliant resistor with heat generation, in this case.   You have to consider that an antenna is a kind of coupling with a waveguide, and then (because it's in open space) remove the 'guide' bits.   A cable, or a waveguide, has a characteristic impedance, and so does an antenna in air.
Comment: How is the energy lost in the antenna quantified? Is it a constant amount? Does it rely on the frequency of the wave? The antenna?
Comment: Energy isn't 'lost in' an antenna, it's 'radiated by' an antenna.   Exactly matching a wavelength to an antenna is possible, but usually there's an LC network, a 'transmatch', with a simple bandpass region (a dipole has multiple passbands, a kind of 'comb').
Answer: You're right that there won't be a DC current flowing, but RF is all about high frequency AC. You can think of an antenna as a capacitor. You can shove some current in there for a little while and charge it up. Then you can pull current out and discharge it. The alternating current in the antenna will generate EM radiation.
Answer: How does the source know whether there is a load at the end of the wire or not?  It doesn't.
It takes time for that information to travel down the wire, reflect off the open-circuit end of the wire, and travel back to the source.  I think for coaxial cable, the information travels at about 67% the speed of light.  What this means is the energy source can start sending a wave down the wire but it won't now whether the wire is an open-circuit until the signal bounces back.  What ends up happening is the sent wave interferes with the bounced wave and creates a standing wave in the wire.  The frequency must be fast enough and the wire the right length so that the source gets through a cycle of the signal before the bounced wave returns and they constructively interfere.  Wikipedia has a nice GIF of this here.  Imagine the blue signal is the sent wave, the red signal is the reflected wave, and the right end of the GIF is the end of the wire.  The black wave is the sum of the red and blue.
This is why both frequency and length are important.  If you try to transmit a slow signal, lets say 1 kHz, the wire will need to be really long.  The period is 1 ms, so you need the wave to travel to the end of the wire, reflect back, and arrive at the source in 1 ms.  That means the wire would have to be:
(2/3)*c*0.001/2 = 100 km
Yes! 100 kilometers long.  So, we stick mostly to waves with higher frequencies because the antennas are practical lengths and we can send more information.


CP access: admin.php or system/index.php

Question: A site that I built last autumn had the CP url set as system/index.php (I think I was following Ryan Irelan's advice in that regard). It works fine. However, last night I did a quick install of EE Core and the bit of the installation wizard specifying 'URL to your control panel access file' pre-filled itself with admin.php. Either method seems to work (provided I appropriately specify the $config['cp_url'] parameter in my config.php file) but I am left wondering which is the 'correct' way? mydomain.com/system/index.php or my domain.com/admin.php? And is one way more secure than the other?
Answer: It's not that using admin.php is a security benefit in itself, it's that it allows you to move your entire /system folder outside of the web root. If you don't take that step then you will see no benefits whatsoever. In fact, if you leave both admin.php and /system in your public_html folder (or equivalent) that's arguably detrimental to security, as you've got two separate CP logins for people to stumble across rather than one.
Why move your system folder out of the web root?
It's a bit like living in an underground bunker rather than a normal house. Instead of having a ton of doors and windows for someone to throw a rock through you've just got the one. If there's an XSS exploit for system/expressionengine/third_party/dodgy_addon/mcp.dodgy_addon.php you aren't vulnerable to it as that file isn't publicly accessible. Any successful hack has to be routed through admin.php*.
Should I always move the system folder out of the web root?
Ideally yes, but you won't always have a choice over server environments or deployment practices, and sometimes it might not be feasible. So long as /system has been renamed it probably isn't worth losing sleep over, but if you have the option it's always worth doing.
* Short of server-level exploits which are really a separate issue.
Comment: Good points, Dom, thanks. I'm currently establishing a portable config.php/database.php setup for easy pre-configured rollouts, and for the time being I'm going to do that with the assumption that I *won't* have the option of moving directories above webroot, but will definitely do so where the opportunity presents itself -- in which case admin.php will evidently come into its own. In either case I'll probably leave admin.php in place as per Alex Roper's reasoning (see below).
Comment: I can't see why you'd be concerned about your system folder's URL appearing in your own request logs. They're your logs on your server and they shouldn't be publicly accessible. Referer headers are a slight concern but EE (and any smart addons) route external requests through `index.php?URL=X`, as Alex points out.
Answer: I believe the main and immediate advantage to using admin.php, wether you move the system folder above root or not, is that it hides the name of the system directory from http request logs. So if you have renamed your system folder (for security reasons), your browser is only making requests to admin.php, not secret_system_folder/index.php.
It's the same reason why when you click the name of your site in the upper right corner of the control panel, you're taken to http://example.com/index.php?URL=http://example.com. I believe this is to mask the referrer URL in server logs from recording your system folder.
Answer: You need to use admin.php when using MSM (Multi Site Manager).  The system folder is only present in one of the sites so if you want to access the Control Panel from one of the other sites you have to use admin.php.
First site in MSM looks like:
/
index.php
admin.php
-System
-Templates
etc

Each subsequent site just has:
/
index.php
admin.php
-Templates
etc

You can access the Control Panel for any site in the MSM from the master (for want of a better term) site via /system/index.php, in which case you don't need admin.php, but if you limit user's access to just one, or rather not all, sites then you will need to provide admin.php as the entry point to the control panel for each site.
EE Security is what you make it - /system/index.php can be secured simply by dropping in an .htaccess file and restricting by IP or something similar.  We tend to have our control panels only accessible from within our network and we can achieve this using either file.  We also remove everything but the front controller (index.php/admin.php) and static assets from the public web root - but that's the answer to another question :)
Comment: I've yet to use the MSM, Jon, but that's really useful info to know in case I ever use it in the future – thanks.
Answer: I personally never use admin.php. I delete it from installs altogether if I do not move system folder above web root. I do not use it with MSM installs either. The only ones I have got only allow for access via the "main" domain.
One less thing to worry about ;o)
EDIT:
That being said, here is a great ebook on securing ExpressionEngine by Mark Huot. Well worth the money/read. If possible, moving your system folder above web root is more secure, as others have indicated.
Comment: I didn't even know that that was permissible Jérôme! And having less things to fuss over is always cool. But after reading the answers below, I think I might stick with the admin route. Be interested to get your take on those extra opinions though.
Comment: Well, as others have said, admin.php is useful when moving system folder above webroot (not always available as a possibility, though). [Full ebook on securing EE installs by mark Huot here](http://mijingo.com/products/ebooklets/securing-expressionengine-2/). Well worth the read/money. As far as MSM sites go, on my install, you can only access the CP via the master domain so no need for it here for me. Whatever you do, rename both the system folder and the admin.php file
Comment: Cool, didn't know deleting it was an option. Always has confused the hell out of me this file :)
Answer: It depends on your needs. First, when changing the name of your system folder, also change the name of the admin.php file, if you plan to use. If not, delete the admin.php file.
Our go to set-up for ExpressionEngine installs are to move the system folder out of the 'public_html' folder (aka: html, www, public, etc.) So if your set-up is more like
/system
/public_html
   - admin.php

Then you want the admin.php file.
We do have old set-ups where /system is in the public_html folder. In those cases we:

Remove 'admin.php' if all control panel users are client's staff. If everyone with control panel access is also considered a trusted source (staff), then we delete the 'admin.php' file, but…
Establish Multiple Levels of Trust with 'admin.php'. In these cases, we may provide only sysadmins or designated staff access to the full system folder and provided everyone else access via the admin.php file. Users of the admin.php file, generally wouldn't have ssh or ftp access either, so they NEVER know the name of the system folder.

Our biggest use though is for using admin.php when the system folder no longer has public access. A good security measure, if you can do it.
Comment: Thanks for the input nonprofit_tech, especially the tip about renaming the admin file – I didn't realise that one could do that. I have a question though: re. your 'scenario 2' above, what benefit do you get from routing trusted staff direct to the system/index.php file rather than to the admin.php file, given that the latter is still available?
Comment: No additional benefit for the 'trusted staff'. We typically provide both urls to them and let them decide, since they know the system folder name. The benefit is more for staff or others 'without' server permissions, so that they never know the system folder name. You can't control, who on staff may give someone the ftp account to make their life easier. But, generally, we prefer the `system folder` to just **NOT** be in the public_html, so everyone uses the `admin.php` file. You could do the same in **all** scenarios.
Comment: Yes, fair enough. (I had wondered why you didn't get even the trusted staff to use the admin.php, but it sounds like it's simply a case of "since they know the system folder name we can't stop them"). In an ideal world I'll be moving the system folder above webroot as well, but recent install scenarios haven't allowed me to do that.
Answer: I like to have as little in the webroot as is humanly possible.
So i always have the system folder above webroot, and i always rename the admin.php file to something random that obviously the client will have to know as it is their only route in to the admin area.
Of course, those things aside, it is equally as important to make sure that you only use third party add-ons from trusted developers as a poorly written add-on will make all your hard work for nothing if someone can just attack you via the front controller anyway by exploiting a bad add-on.
As well as that, make sure your file permissions are locked down, your php version is kept up to date (i don't mean use php 5.5 or whatever, but just the latest php 5.3.x at the moment) and your server is locked down with a firewall if possible. These things will offer greater protection from nefarious types than just moving and renaming your system folder.
Comment: Good advice. Cheers John.
Comment: Well, someone doesn't think so, they've given this answer a minus score!


Combinations with symbols

Question: Suppose we have the following symbols: $\{a,b\}$. Now there are some rules. More than 3 $b$'s are now allowed and $aa$ is not allowed. So $ababab$ is allowed, but for example $abbbbaba$ not (more than 3 $b$'s). There is an easy way to get this working. Suppose you have a string of $n$ characters. Just add between every two numbers a new number so the string is correct. Decoding is not hard: just remove all numbers on even positions. So $abbbbaba \rightarrow axbxbxbxbxaxbxax$ and decoding is the same as just removing the $x$'s. But the problem is that the string size doubles. Is there a more efficient way to accomplish encoding and decoding? So encoding means encode all strings to valid strings and decoding means decode that string back to the original string.
Comment: Using extra symbols is kind of cheating (you can encode up to $|\Sigma|^n$ strings of length $n$ using alphabet $\Sigma$). So you can actually _compress_ a binary string using larger alphabet! Could you please make the question more accurate?
Comment: @Dmytro: The *x*'s in the original question stand for either *a* or *b* ... it is not hard to show that you can always replace the *x*'s with some combination of *a*'s and *b*'s to achieve a legal string.
Comment: Then it would be even possible to compress any random string to a string of length one (using a alphabet of unbounded size).
Answer: This is called run-length-limited coding, there has been lots of research done on it by the information theory community, and I will just refer you to the existing literature. After a brief glance at the wikipedia article I linked to, my impression is that you shouldn't rely on the references it contains, but do your own search of the literature.
One simple thing you could do that does better than doubling the string size is:
(1) add a 0 to the end of the original sequence,
(2) break the original sequence greedily into blocks of either 0, 10, or 11,
(3) encode using the encoding

   0 → ab
  10 → abb
  11 → abbb

Step (2) is always possible, since after step (1) the sequence ends with a 0. Except for step (1), which adds at most two bits to your encoded sequence, this cannot do worse than double the string size, and generally does better.
For example, you encode
0110100101 → 0.11.0.10.0.10.10 → ababbbababbababbabb,
taking 10 characters into 19.
If I did my calculations right, starting with $n$ random bits, this encoding gives an expected length of 11/6 $n$ bits, which is only slightly more than the optimal value of around 1.813 $n$ bits.
Comment: We have already proven that $1.81... \cdot n$ bit is the optimal value using recursive formula's and counting the `legal` sequences. How have you found that that is the optimal value? Are there even more effective ways than this $1.83... \cdot n$ algorithm?
Comment: @Rudy: I used recursive formulas and counting the legal sequences to get $1.813\, n$ as well. There are certainly even more effective ways than the $1.833 \, n$ algorithm, but I don't know whether any of them are as simple.
Comment: @Rudy: somewhere in the literature there should be theorem giving polynomial-time algorithms for doing run-length encoding with arbitrary constraints. So, yes, you can get more effective algorithms. But I don't have time to do the literature search for you, and offhand I don't know whether any of them are as simple as the encoding I give in my answer.
Answer: For the problem as you've posed it, it seems that you could simply replace every occurrence of an illegal sequence by a new symbol so that: aababbbaba -> xbayaba.
I guess that's probably too simple, but we'll need more information to provide a better solution (like the cost of adding symbols).
Comment: No, no new symbols are allowed, only $\{a,b\}$. So there are two symbols. We need to encode (il)illegal sequences to legal ones, and we must be able to go back to the original (il)legal sequences.
Comment: I see what you mean now: the x's represent a or b depending on the context. I'll have another think.

Combinations with symbols


overall energy and the boiling point

Question: i need help with the fractional distillation method of a couple of substances at least more than two substances , just like air actually what am i looking for is that why do substances in air with a low boiling point like nitrogen reach higher the fractionating column even if it looks like that substances with higher boiling point will absorb more energy and thus eventually result in greater kinetic energy (at least to me). please help . heres how i came to know that nitrogen rises higher the fractionating column
Answer: The gases in the distillation column boil off according to their boiling point.
<code>   Gas          Boiling point
   Nitrogen     77.355 K (−195.795 °C)
   Argon        87.302 K (−185.848 °C)
   Oxygen       90.188 K (−182.962 °C)
</code>
The distillation column shown is setup for continuous distillation. But imagine that a pot distillation was being done. Nitrogen would boil off first, then argon, then oxygen. So the various trays in the distillation column represent different temperatures. Nitrogen boils off at the top since it has the lowest boiling point, and oxygen collects in the "pot" since it has the highest boiling point.
Comment: that answered my whole question , thanks !
actually i did not knew that the trays in distillation flask are not of the same trempreature throughout .
But what about a fractionatig column with marbles in it ? it has no trempreature diffrences
Comment: The marbles would act as the trays. There has to be a temperature difference from the bottom to the top of the column or it isn't a "fractioning column."
Comment: but the laboratory setup for the marble distillation column does not show any trempreature difference !
Comment: In a typical pot chemistry experiment you heat the liquid in the pot and the vapor carries the heat up the column.
Comment: thanks !
for a second i thought that in the marble fractionating column
you need to collect the pure gas from below the container!
hopefully i was wrong , right ?
Answer: Distillation relies on the fact that, at the same stage (tray), all the substances are approximately at the same temperature. Then, at the same temperature, the vapour will be composed preferably by substances with a lower boiling point and the liquid composition will be dominated by higher boiling point compounds.
Very quickly, distillation works as follows. The vapour flow from one stage (i) is then richer in the light compound (with lower boiling point). That vapour is enters the immediately higher stage (i-1) making the composition richer in the light compound. The vapour from stage i-1 is even richer in the light compound. This process is repeated until you reach the top stage where the light compound can be almost pure. Likewise, the liquid of stage i is rich in the heavy compound and goes down to stage i+1. The liquid leaving stage i+1 is even richer in the heavy compound. At the bottom, you can reach and almost pure heavy compound.
Formally, the fractionation of a mixture is dictated by the relative volatility of the compounds (which for ideal solutions does not vary along the column). At low/moderate pressures and for an ideal solution, the relative volatility is simply
$$
\alpha =\dfrac{\dfrac{y_1}{x_1}}{\dfrac{y_2}{x_2}} = \dfrac{P^s_1}{P^s_2}
$$
We usually take the heaviest compound as the bottom line for comparison. In your example, at the pressure and temperature conditions of the column, the relative volatility of nitrogen/oxygen is higher than argon/oxygen. Therefore, nitrogen leaves the column at the top, argon at an intermediate stage and oxygen at the bottom.
Comment: that hopefully explains why at the same stage(tray) the substance with lesser boiling point dominates . but why do the higher melting points condense at a particular tray and the lower melting points rise higher ?
thanks in advance
Comment: I have edited my answer to respond your query
Comment: thanks , it explains everything now
is this your own opinion or have you taken it from a source
please mention if there is any
i am asking you this because i had a similar post and someone posted some diffrent explanation. i would had provided th link but the post is gone now
Comment: No, this is not my own opinion. You can take any textbook on distillation and it will say the same. I would recomend "Separation Process Principles" by Seader and Henley; "Separation Process Engineering" by Wankat
Comment: one second
i pondered over your explanation and it suggests that if we achieve the boiling points of any two of three liquids in diffrent containers , then in a specific interval of time all should have achieved the same height ? but we know that this is not the case ! please explain
Comment: I don't understand your remark. Achieve boiling points? Achieved the same height?
Comment: actually what i am saying is that liquids with diffrent boiling points if kept in diffrent containers and then  beginned to heat till they convert into gases will then the gas of the liquid which had higher boiling point travel farther or the gas with the liquid having lower boiling point ?

overall energy and the boiling point


Replacing donut spare on 2008 Toyota Prius

Question: I recently had a flat tire (right front) on my 2008 Toyota Prius.  The original donut spare, never used before, was used to replace it and I continued my 30 mile journey home, highway driving, before replacing the front tires.  I was told that I could use the donut again.  However, considering the age of the donut tire, would I be wise to replace it?  I hesitate to ask the dealer or my tire store. How much should it cost?  I don't feel confident in assessing the condition of the tire.
Comment: Welcome to Motor Vehicle Maintenance & Repair!
Answer: A donut spare is usually good for 50 miles at speeds of at most 50 mph.
You already did the 30 miles, presumably at about 50 mph because it was highway driving. So you can't expect the donut to last more than 20 further miles highway driving, considering tires age as a function of:

Speed: you were driving probably at the maximum speed for the donut tire.
Distance: you covered already 30 miles, which is 60% of the rated distance.
Age: an unused tire shouldn't be put into use if over 6 years old, and a tire that's over 10 years old should be removed from use. Your donut is already 10 years old.

Is 20 miles enough for you to get from all possible places to the nearest tire shop? For me, I would replace the tire based on the list items (1), (2) and (3).


Is link building still a factor for getting rank in Google?

Question: Is link building still a major factor for good ranking in SERP's of Google?
Answer: Backlinks still form the #1 contributing factor in getting a page to rank in Google.
Generally speaking:

High Quality back-links are better than high quantity back-links
Freely-given links are better than procured back-links (procure can mean artificially gained in any manner, not just bought)
Page Rank still matters in terms of the currency of back-links

So then it comes down to what you define as "link building"? If you mean providing rich, orginal content that other's find worth linking to - then yes. If you mean dropping links in forums, comments, directories etc - then no.

The biggest reason modern era search algos all love backlinks is because a trusted, organic link is still the hardest form of citation to acquire on the web...especially, at scale. (source)

More ranking factors are broken down here: http://www.seomoz.org/article/search-ranking-factors (this is accumulated opinion, not fact).
Answer: Yes, it matters the most. What's changed are some of the nuances of the linking.
There is some evidence that suggests that recent updates do more than simply count the anchor text from an external link but also more strongly consider the semantic content matching threshold between the pages. So, if you have a blog comment or forum profile that doesn't match semantically (too low) or is keyword stuffed (too high) it won't count as much as a more natural contextual page/link combo (just right).
Another nuance is thats been introduced is a more refined level of scoring the authority of links. This tends to be in flux and, therefore, is hard to nail down. But things like active age and authority of externally linking sites remain at the top of the list.
As Mike noted, SEO is mostly accumulated opinion and sometimes those who're accumulating opinions are trying to sell their SEO services or get SEO seminar speaking engagements so bear that in mind.
Comment: I don't think this is the case. The relevance of pages linking to another page has been around for a while and keyword stuffing has been for a very long time. The Panda update deals with low quality and duplicate content. Neither of which directly deal with relevance of links or keyword stuffing.
Comment: The relevance of pages linking to another page has been part of Google's algorithm for a while now.
Comment: My point was that it became more refined and widespread with the Panda update. Previously, some types of keyword stuffing, particularly related term stuffing, worked and was a common tactic used by certain pharma product spammers and others. But that doesn't work as well now.
Comment: It's a matter of degree of the relevance of the stuffing. The previous technique wasn't to stuff the same keyword combos over and over again as in circa 1999 stuffing but to stuff with semantically relevant phrases. For example, taking everything a Adwords keyword search listing and putting it in a post. Panda blunted this somewhat. This is a part of how they're judging content quality now although they're happy to misdirect people into thinking they have a "I'll be back" level of AI.
Comment: "_semantic content matching threshold_" - okaaaayy...
Answer: Yes Link building still plays an important role to rank your site in Google. As long as you acquire quality instead of spammy links and apply an advance link strategies. You can read this source for more info.
Answer: Yes, Google still determines a site's merit based on its association with other websites. The better those associations are, the better that site will rank.


My Raspberry Pi 3 B won't work with the touchscreen

Question: So i've got a KeDei 3.5" touch screen Version 6.3 and i installed an image of Kali with the driver that's given of KeDei's website (http://kedei.net/raspberry/raspberry.html) but it hasn't been working, the display doesn't display anything, it just turns on when the Rasp does, i have been searching all over for the answer to my problem but i haven't found it yet, i hope i'll be able to find it here.
Comment: read the info on the KeDei webpage .... do you have a supported RPi?
Comment: The fact that it "turns on" is a very good sign.  That is a test of pin assignment and some of the circuitry.  I would expect that to mean it is a software problem.  I trust someone here will be able to help.
Comment: jsotola : i do have a supported RPi, i checked and rechecked
Comment: SDsolar : if it's only a software problem, then i'm reassured, i was worrying i had to buy another one when i'm running low on money
Comment: @Bones, look again ... what three devices does Kali support? .... RPi B is not one of them.
Answer: 1.- check in the vendor page your device is supported by RPI3.
2.- check in the vendor page if your device supports the OS your RPI3 is running.
3.- check in the vendor page if your device need some special drivers for touch related to each OS.
4.- some screen devices are usable with raspbian, other OS's does not seem to work or at least not properly.
i bought like 3 chinnesse screens ( two of these with touch ), but at this point i haven't be able to make it work, other times they should be connected to make the touch work but the cables does not come within the package, and also you have to use the correct voltage to make all the screen work as expected.
Comment: thanks, i double checked everything and apparently it doesn't work with kali on a RPi 3 b


Format of NONCE in Initialization Vector (IV)

Question: When we talk about a Number used ONCE (NONCE) in Initialization Vector (IV), is it required to use numbers only? Is is possible to use letters or special characters?
Comment: It's just a string of bits, how you wish to interpret it is entirely up to you and irrelevant to the actual underlying cryptographic operations being performed (personally I like to use hex. representation for visual inspection as it's easy to compare bitwise, great for debugging)
Comment: An IV or nonce is a sequence of bytes, the concept of letters doesn't make much sense here. So what's your question? Are you talking about the ASCII representation of those bytes? Or the hex representation?
Answer: No. In the context of the Initialization Vector of a cipher operated in some mode, the most significant property of a cryptographic nonce is that it is not reused. It often matters that it is random and unpredictable (e.g. with CBC). It is immaterial that it represents a number or anything else under some particular encoding.
If an IV is chosen at random, it would be bad to restrict it to represent a number (say, restricting each byte to be a digit according to ASCII), in particular because it would dramatically increases the odds of reusing the same IV.
Comment: Removed "standard and best" about random nonce. It is good practice, but other forms of NONCE are also standardized, and "best" is subjective. If a message already has a unique identifier, it is questionable if it is best to use a random instead of the UID.
Comment: @owlstead: I'm OK with you change. However, using an UID as IV can be bad: in CBC mode, if the UID is predictable, encryption can be broken under CPA; in CTR mode, if consecutive UIDs differ only in the same low bits that are changed by counting, some keystream is reused. $\;$ In my opinion, the simplest (thus often the best) is: **if the key is used for a single session, use implicit zero IV; otherwise use a random IV.**


What does mastered mean on a commercial library?

Question: All the libraries I have bought/seen advertised say mastered at 24/96. Is this meaning simply that the audio was cleaned up, metadata was added and its ready for drag and drop use? Or is there something more?
Answer: In that context I tend to read "mastered" as audio that is edited, problems eq'd out, strange noises removed, etc.  Sometimes that can also imply downsampling from a higher sample rate.
I don't tend to read that as having anything to do with metadata.
I also don't take that to imply any sort of dynamics processing.
YMMV
Answer: While I've never used that term to describe my own libraries, I'd assume it just means it was produced, edited, processed etc at 24/96. It's a strange choice of words, as it obviously causes a bit of confusion. I always just say "24 bit audio" in the specs, 24/44 lately.


how to upgrade from magento 2.3.0 to 2.3.1 steps (composer)

Question: I want to upgrade my magento to the latest version. what are the steps to upgrade from Magento 2.3.0 to Magento 2.3.1 via composer?
Answer: upgrade Magento 2.3.0 to 2.3.1 over composer:
the below steps should work.
step 1 require latest version 2.3.1
composer require magento/product-community-edition=2.3.1 --no-update

step 2 apply updates
composer update

step 3 clean magento cache
bin/magento cache:clean

step 4 clear var and generated folders
rm -rf <Magento install dir>/var/cache/*
rm -rf <Magento install dir>/var/page_cache/*
rm -rf <Magento install dir>/generated/code/*

step 5 update databse schema and data
php bin/magento setup:upgrade

step 6 disable maintenance mode
php bin/magento maintenance:disable

step 7 apply static content (depending on your languages)
bin/magento setup:static-content:deploy -f nl_BE
bin/magento setup:static-content:deploy -f nl_NL
bin/magento setup:static-content:deploy -f en_US

that's it.
Comment: I have to mention one more command `bin/magento cache:enable` because my caches was disabled after update via composer.


What validation code should I use such that if any Column entry is changed it shows an error ?

Question: I'm basically trying to keep 5 columns of my list locked(uneditable) while the last column editable.
I'm a beginner and thought this would be the easiest way to achieve this.
Do kindly suggest any other alternative if possible.
Answer: This is not possible out of the box. You can limit it but not block it. ie User may still find a away of editing it if its smart.
Sharepoint is not transactional system and doesn't have something called field level security.
Now what you can do.
I have delivered something similar in the past using InfoPath forms.
WIht IP you can specify which IP view is showed for new and edit form. On 'New' view you make all the fields editable. On the Edit view you make only the last column editable.
There are as well some other ways of achieving it using javascript but I haven't used them so cannot give much advice in this area. (you embed js in the new/edit forms and make the fields view only. )
But with any of those options user can still go to the list switch to the datasheet view and edit value - so you can limit it but not block it as mentioned earlier.
Answer: To make the field read only on the edit form, you can use the script editor on Edit item page.
Add below code in the script editor:
<code><script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.1/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
     $(document).ready(function() {
           //Set the Field to Read only and change its background colour
           $("input[title='FieldName']").attr("readonly","true").css('background-color','#F6F6F6');
     });
</code>

You can repeat the read only statement for all other fields you want to make ready only(just make sure you are using right jquery selector).
Use following link to add script editor on page:
Add script editor on page.
Comment: have you tried this?


can i bottle cider at 150 sg it has been still for a month

Question: my cider started at 190 and now is 150 and has been still for about a month, can I drink and bottle it at this time?
Comment: Do you mean gravity readings of 1.190 and 1.150?
Comment: That would be rocket fuel! I'm guessing 1.090 and 1.050. If that's the case, my answer is "no". Pitch more yeast, and let it finish fermenting.
Comment: @TobiasPatton: Why would it be rocket fuel?  That's only 5.9% ABV.
Comment: @im1dermike I should have said "potential rocket fuel". Given the right yeast, a 1.190 must can produce 25% ABV wine.
Answer:
Can I drink and bottle it at this time?

Sure!

Should you drink and bottle it at this time?

Absolutely not.  It will be sickeningly sweet and will probably end up being bottle bombs.
Comment: Bottling something that's not even close to finished fermenting can lead to "explosive" pressures, commonly referred to as "bottle bombs".
Comment: @jsled: yep. That too.
Answer: Short answer: Q:What does it taste like right now?
In my circle (wine/beer/cider), we talk casually about a "gravity of 50" or "press it at 20", meaning an SG of 1.050 or 1.020.  As a scientist, an SG of 150 literally means a liquid 12x the density of mercury. An SG of 1.150 is something I have encountered occasionally, with late-harvest grapes. In cider making, Quebec producers create an "ice cider", which might have a starting SG of 1.150 if they cheat and add concentrate.
@Tobias observed that you likely have a current SG of 1.050.  That is a typical starting SG for unfermented apple juice. So either you are wondering about bottling "soft" cider and are worried if it will keep, or you added yeast a while back and nothing happened (store-bought juice preserved with sorbate/SO2), or your "150" means something else again. Maybe 1.005?
In a cider-making year in mid-December, I would be happy to have large amounts of cider at an SG of 1.005. That would have a nice residual sugar of 2% to 3%. I would put some in a keg, fizz it with CO2, and serve it over Xmas/NewYears pretending it is Champagne.
Getting back to serious hard-cider bottling:
If you are trying to produce a hard, dry, bottle-conditioned sparkling cider then you either need to "catch it on the way down" and bottle it at 1.000 to 1.005, or ferment it to dryness (0.996-ish) then add fresh strong yeast (such as EC-1118) and glucose at bottling (that's what I do). If you simply bottle it at 1.005, be prepared to wait through a warm summer for fermentation to start up again and finish the job.
If you aren't sure what to do, make sure you have added some SO2 (aka Sulphite), keep it well topped-up, and wait until June to see what happens. Never bottle out of uncertainty!
Comment: I should have been more specific. It is sweet, it originally tested at 1.090 (I added brown sugar)I added EC 1118 it went still after about 5 weeks, I tested it and it was 1.060 I again added the yeast and waited another 4 weeks before testing, this time it was 1.050 I added yeast yet again and let it sit for another 3 weeks before testing as I never saw any fermentation through the airlock. it still tests at 1.050. I just moved it to the secondary fermenter hoping it might make a difference. Thank you for the insight


Replying to an email with others CCed

Question: When replying to an email with others CCed in it,
do I address the sender only, e.g. Dear Sam, or address everyone, e.g. Dear all?
Comment: Was the original email addressed to you, or to everyone?
Comment: @LaconicDroid it was addressed to me, so should I do the same and address the sender only and keep the other cced?
Comment: @user52773 Based on that, I would have given the same answer as Joe Strazzere, below.
Comment: Rule of thumb; address those in the "To" list, not those in the "CC" list.
Answer: It's really context dependent.
Typically, the To/CC lines will give you a good indication. If there is a group of people in the To, generally that's a group conversation. If there is a single To but a group in the CC, typically that's a individual conversation with others being kept abreast.

If the communication is primarily between the two of you with other's cc'd to ensure they're aware of the communication, address it to the individual.
As a common example, you request information from me and cc your boss and my boss. I will reply all but address you specifically, unless I need/want information from one of our bosses. (Common etiquette would say I can request info from my boss, but should probably address questions I expect only your boss can answer to you and allow you to escalate).

To: user74164 CC: YourBoss, MyBoss
user74164,
Yes, coversheets are now mandatory on all TPS reports.

If you're talking to the group, address it to the group.
Example:

To: user74164, MyBoss, YourBoss, SubjectMatterExpert, ProjectManager CC: VP, PotUS
URGENT!!!
All,
I need your TPS reports (WITH COVERSHEETS!!!!) ASAP.

If you really don't know what to do, just don't address the email to anyone. I would guess that 50% of my replies are not formally addressed to anyone in particular.

To: user74164, MyBoss, YourBoss, SubjectMatterExpert, ProjectManager
TPS coversheets shall be in 11.5 pt font.

Occasionally, you need to address multiple people.

To: Joe, Sue CC: MyBoss, user74164, ProjectManager
Joe and Sue,
I need TPS coversheets in 11.5 pt font ASAP!

works, however, sometimes it can be better to

To: Joe, Sue CC: MyBoss, user74164, ProjectManager
Joe,
Can you please provide your TPS coversheet ASAP.
Sue,
Your TPS coversheet is in 12 pt font instead of the appropriate 11.5 pt font. Please remedy.
Comment: I don't think that last one is a good idea. If people see the main addressee is not themselves, they are likely to skim or ignore the mail and they won't catch the second opening further down. You might be better off sending two mails at that point.
Comment: Final example is a matter of personal taste, IMHO.  If it's the norm in a given office, it should be fine.  If it's not the norm in *your office*, adjust as required.  +1 for the TPS reports, though. ;)
Answer: Some good rules of thumb to follow

Address people on the "to" list
Put people on the "to" list that need to know and are directly involved
Put people on the "CC" list who need to be aware of what is going on but are not directly involved: People you are keeping "in the loop"
Only address people on the "CC" list if you are bringing up a topic that involves then.  "By the way Joe, our meeting on this issue has been moved to 2pm"
If you are addressing more than three people, "all" or "team" is acceptable
Answer:
when replying to an email with others cced in it do I address the
  sender only i.e. Dear Sam, or address everyone i.e. Dear all?

Address it only to the sender.
Answer: CC means Carbon Copy.
It usually denotes recipients that should receive a copy, but to which the original message is not addressed.
Hence, you just address everyone in the 'To:' field, and that is. In some cases you may want to let people know that some people have been included as CC. And, of course, you never mention anyone in BCC.
Answer: My standard practise is to add the people who need to read the email.
If my boss/someone above me sent it, I'll include everyone as he did.
If a colleague sent it, I'll usually check the to/CC to see if anyone is on the list unnecessary
For example, no matter how many people are in the To/CC, I'll do

Hi, Matt, Emily <- List of people I'm taking to
I've done x, y, z. The commit is in git v0.03. <- comment to both
Matt, What do you think of a, b? <- comment to one recipient
Emily, Can we test these changes this afternoon? <- comment to another recipient.
Thanks,
Stanri

This way, people can check the Hi line to see if their name is there. If not, they don't have to read the email. If their name is there, they can check further down to find their name.
I usually keep their names on the left, at the start of a new paragraph so someone skim reading can find their name.
I generally also keep my emails short and concise, and only group relevant things together in one email (different subject/project/etc different email).
Comment: I feel that having orthogonal points in an email is not a good idea.  You are asking both Emily and Matt to read things that are irrelevant to each other and increasing the chance that Emily will skip reading the email because the part relevant to her is not directly obvious.
Comment: @PeterM The intention of my last paragraph was to address this. The idea is that Emily and I would be testing x,y,z. If they were completely not related, I would start a new email thread. This is also why I try to keep the points short, so that people don't have trouble finding their name.
Comment: I understand what you are saying but i think that your example is problematic as it *assumes* that Emily knows that this email is about her tasks on x,y,z.  If Emily doesn't make that mental connection then that is where issues start.
Comment: @PeterM I'm assuming people will read the email addressed to them. This is just an example and I usually attempt to connect things together to a reasonable extent. I'll change the example to reflect this. Receiving parties need to do due diligence in at least attempting to parse the information received. I have used this format for years and never run into any trouble.
Answer: It is often not immediately obvious when reading a email that you got it only because you were on the CC list.  Therefore, as a courtesy to those CCed, I usually address the main recipient directly at top.
For example, if I'm sending a email to Gustav and CCing to Takashi and Naresh, then I'll start with something like "Gustav, the bobulator is ...".  That way Takashi and Naresh immediately see they are being copied in a message from me to Gustav.
Answer: I put Dear All just to make Everyone aware. Best thing to do I think.
Comment: If you're really addressing all, then they should all be direct recipients, not CCs.

Replying to an email with others CCed


Variations of the same song

Question: What is the name of the term used for when the soundtrack composer, creates a song and the other songs are variations of the same song. For example, in the movie Inception, The Last of the Mohicans, Requiem For a Dream
Comment: Not sure if this is what you're after, but the terms "reprise", "remix" & "alternate version" often accompany those derivative tracks in soundtracks and albums, usually in parentheses.
Comment: Do you mean like the Bond theme being used in music throughout the films?
Comment: @Walt yeah, but, I think that it isn't what I'm lookking for.
@CGCampbell nearly so. If you listen the soundtrack of `Incepction` you will understand better.
Comment: A very clear example is _The Long Goodbye_, in the film of the same name. John Williams (of Star Wars and Potter fame) created the title song, and it is rendered a number of times throughout the movie (via radio a couple times, live in the piano bar, live at the Mexican funeral, a bluesy rendition, etc.), different each time.
Answer: This really is just called a variation and it's not limited to soundtracks, Wikipedia says:

In music, variation is a formal technique where material is repeated in an altered form.

A famous example of this are the Goldberg Variations.
A Leitmotif is by definition the leading theme of the overall piece, which would be the film in this case, so it may be the main character's theme tune, or the title theme, which is then the most likely candidate to be the tune which is varied throughout the rest of the film depending on the tone of the scene or emotional state of the character(s).
Comment: Fun fact: when I was 14 I saw The Dark Crystal and bought the soundtrack. Turns out several songs used the same melody, just with different "moods" and orchestrations. I remember a swelling full orchestra version, as well as a lively "galloping across the plains" version. There are probably other variations that I missed (or can't recall now that I'm 46!).
Comment: @FelipeStoker I've added an edit to compare the two ideas
Comment: I've read about it. I also found the term `Leitmotiv`. Now, I'm confused, hehe.
http://pt.wikipedia.org/wiki/Leitmoti

Variations of the same song


Why is there a discrepancy between current inflation rate and I bond rate in the US?

Question: According to https://www.rateinflation.com/inflation-rate/usa-inflation-rate/, the November 2022 inflation rate is 7.11%, but the I Bond rate according to Treasury Direct is 6.89% (from November 2022 to April 2023). I know that there is a positive correlation between inflation rate and I bond rate, but why could be factors that could contribute to the discrepancy of one being 7.11% (I've compared multiple resources and 7.1% or 7.11% seem to be the one reported) and another being 6.89%?
Comment: @HelloDarkWorld Rate for I bonds is set every half a year on November 1st and May 1st.
Comment: 6.89 is not inflation but the combined rate as per my other answer (I compute the values).  The other answer may be misleading as they are only partially derived from inflation BUT not determined by inflation alone (although linked does not imply it is the only factor - it just does not mention another). Also, the rate is set on 1st of November, you do not even know the November rate yet. (which is a rate of change to the previous year).
Comment: Thanks. What do you mean by "the rate (what rate?) is set on 1st of November, you do not even know the November rate yet. (which is a rate of change to the previous year)"?
Comment: They pay interest as high as inflation?  That sounds too good to be true.  What's the catch?
Answer: The "inflation rate" for the i-bond is based on the past 6 months of CPI values, not a whole year.
Comment: what about the inflation rate for November 2022 of 7.1% based on multiple resources? Are they based on the past 6 months or?
Comment: 12 months (year-over-year)
Answer: It takes time to compute inflation. That's why the reset inflation rate in May and November does not use the values for May and November inflation (it is not yet available when the rate is announced). Conventionally, percentage values are computed as year over year YoY), meaning Nov21 - Nov22 in your example. Also, there are several inflation series available; seasonally adjusted or unadjusted, including or excluding volatile products like food and energy and the like. Details about the design of inflation indices would be a seperate (complex) question.
In any case, what is used to compute inflation for I bonds is this series, found in the section where it reads

Finally, the next grouping of data shows actually CPI figures from
1913 to present.
All Urban Consumers – (CPI-U) 1913-2022*

The computation is like this
For 1st of Nov, the inflation values (not percentage values, but the actual index value) for March to September are used because it is semi-annual and as mentioned above, the latest values are not available yet: 2968.08/2875.04 =3.24%, because it is rounded to two decimal places).

That is the inflation rate I showed in my other answer.
This answer replicates the calculation of the current value on the website of TreasuryDirect.
This answer explains why the formula

Composite rate = [Fixed rate + (2 x Semiannual inflation rate) +
(Fixed rate x Semiannual inflation rate)]

is designed like that.
Comment: 1st of Mai value is Mar 22 / Sep 21 (287.504/274.31) which is 4.81% on so forth.
Comment: Noc 22 CPI in % is change to the previous year (Nov 21) .  297.711/277.948, hence 7.11% according to this series. Note, inflation can be computed in numeous ways, and be seasonally adjusted, non seasonally adjusted... The link i provide above is the one used for I Bonds.


How to understand this question 'what did you shop for?'

Question: I clearly understand the meaning of 'what did you shop?' But I don't understand this 'for' at the end.
Comment: Welcome to ELL.SE. Context is very important to meaning—there are several different meanings of *shop*, for example—so we can only provide a definitive answer if you tell us the circumstances where you have encountered this sentence—who is saying it and what are the surrounding sentences? Please [edit] your post to include this information. I further encourage you to take the site [tour] and review the [help] for guidance on writing strong, answerable questions.
Comment: Compare:    Who did you write *to*?    What building did you live *in*?   What pony did you sit *on*?
Answer: There is a subtle difference between the verb "shop" by itself, and the phrasal verb "shop for".  In the context of ordinary commerce: By itself, "shop" simply implies the activity of going out and (potentially) buying things from shops.  "Shop for" instead implies the activity of buying some specific item from the shops.
Example:

Yesterday we went shopping (= we had no specific purchase in mind)
Yesterday we went shopping for [warm winter coats for the kids]

You cannot ask "What did you shop?" if you want to know the intended purchase.  Instead you must ask "what did you shop for?"  However you may ask more general questions such as:

When did you shop?
Where did you shop?
Who did you shop with?

or other questions that may not directly relate to the intended items.
Side Note: "Shop" has other, colloquial, and relatively uncommon definitions.  For these, "What did you shop?" might be fine.
Comment: I would take *What did you shop?* to mean *What did you try to* ***sell***? As in, *I shopped my idea to various clients.*
Comment: @JasonBassford  That's a different definition of "shop".  It could also be *'shop*, as in *Photoshop*, plus any other colloquialisms.
Comment: Quite right. There is nothing at all in the sentence *Why did you shop?*  that specifies a particular meaning. Aside from the fact that without a preposition it's the selling meaning that I interpret it as. If *for* is added, then I'd think of buying. So, your first two sentences are not really accurate. Barring context, there's more than just a subtle difference.
Comment: @JasonBassford  I wrote *"You cannot ask "What did you shop?" **if you want to know the intended purchase***.  In other words, in this particular context, it doesn't work.  For a different, colloquial definition of "shop", sure, it might, but that seems outside the scope of the question.
Comment: The question says, literally, "I clearly understand the meaning of 'what did you shop?'" Well, I don't because *shop* has multiple meanings. Nowhere does it mention purchasing anything. You added that yourself.
Answer: Shop is an intransitive verb: it does not take an object. The things we intend to purchase are expressed with a preposition phrase headed by for:

We shopped for clothes at Marks & Spencer.

Consequently, when you ask your respondent to name the thing or things they intended to purchase, the interrogative (what) must be cast as the object of for. When the interrogtative is fronted it may carry the preposition with it ('pied-piping') —

For what did you shop?

—or the preposition may be left in place ('stranded'):

What did you shop for?

Pied-piping is preferred in formal registers, stranding in informal registers.
Answer: Without any other context, shop in your first sentence can have an ambiguous meaning.

What did you shop?

The use of a preposition clarifies the intended sense of the word.

What did you shop for (this Christmas)?

This is asking what you purchased. It's the more common of possible meanings, but it's not the only one.

What did you shop around (to the executives)?

Here, it's asking what you were trying to sell. The expression shopping something around is often used in the sense of trying to market an idea or product.

What did you shop out (of the picture)?

Here, it's being used in the colloquial sense of Photoshop, the popular graphic-editing application. It might be styled as Shop or 'shop, but often isn't. This sentence is asking what element was removed from a picture.

In each case, the use of a preposition makes the intended meaning of shop clear, distinguishing it from other interpretations.
As I mentioned, context can also make it clear, and often context means you don't have to use a preposition. But without context, a preposition will aid in the prevention of any misinterpretation.


Sluggish Acceleration

Question: I have a 2003 Kia Spectra. Just replaced the radiator. The car does not overheat when running, no fluid leaking.  However, car is very sluggish when accelerating. Rpm goes up but car jerks into movement. There is light white smoke once car is fully warmed up.  I did not have this problem at all prior to replacing the radiator. I've read in a few places it could be an airlock so I tried running the car with heat on high and cap off radiator. The heater blew hot air as it should but once I replaced the radiator cap and tried driving it's still sluggish. I should mention I have only driven it at lower speeds through the parking lot and not on the highway. Should I drive it at higher speeds for longer distance to remove airlock? I don't want to blow up my engine. Please help.
Answer: Air in the coolant usually comes with a fluctuating idle.
White smoke usually means headgaket has popped as coolant is being burned in the combustion process.  It doesn't always mean it will overheat.
Comment: It actually ended up being a loose hose connected to the radiator. I was loosing transmission fluid.

Sluggish Acceleration


What is the relationship between Iranian president and supreme leader?

Question: In Iran, the supreme leader is the highest figure. I want to know, what is the relationship between him and the president. Does the president need the nod of supreme leader every time he makes a decision? if so, why do people in Iran always blame the government for incorrect policy? They dare not?
Answer: The role of the Supreme Leader is spelled out in Chapter VIII of the Iranian constitution (unofficial English translation).
The SL controls the president in the way that he* has large influence on deciding who can run for president in the first place. Any presidential candidate needs to be accepted by the guardian council, and six of its twelve members are chosen by the SL.
The SL is officially above the President and has far-fetching but mostly indirect rights. He controls the military and appoints many other important positions in the government. Among them is also half of the aforementioned Guardian Council which reviews all laws and can reject them for violating the constitution or the Islamic law. There is not much the SL decides directly, but his de facto influence is still very strong because he can instantly fire a lot of important people when they make decisions he doesn't agree with.
However, the president is not among those the SL can fire at will. The SL can try to impeach the president, but needs a two third majority of the assembly (parliament) to do so.
The duties delegated to the president are in Chapter IX of the Iranian constitution. Things the president can do without having to consult the SL are:

sign international treaties
plan the fiscal budget
state employment affairs (those which are not made by the SL)
appoint ambassadors
sign laws which were decided upon by the assembly (but sill need to pass the GC)

In these ways, the Iranian president is an executive leader while the legislative power is in the hands of the parliament.
Regarding the Iranian public "not daring" to criticize the Supreme Leader and blame the secular government instead: The SL is also the religious leader of Iran and Iran is still a quite fundamentalist state. Criticizing the SL can easily be interpreted as criticizing Islam as a whole. Apostasy is punished by the Revolutionary Guard which is also under direct control of the SL. So people need to treat lightly in this regard.
However, you did not specify for which "incorrect policies" people blame the government instead of the clergy. It's not unlikely you actually are talking about things which indeed are in the hands of the elected president and parliament.
* Considering that we are talking about an Islamic religious position here I believe I can forego using gender-neutral pronouns. I might have to do some research to find out if it might be theoretically possible for the SL to be a woman, but I think we can all agree that Iran isn't so far yet that a female SL is a realistic possibility.
Comment: The term "Supreme Leader" is a bit odd here, at least for us Iranians. he is actually called The Supreme Commanders of the Armed Forces meaning the leader of the Ground forces, Navy forces, Air forces, Sepah (IRGC) forces, Basij forces and of course, the Ghods forces. Btw, iranonline.com is not an *official* source for Iran's constitution's translation. these are the official sources: [Here](http://www.mfa.gov.ir/index.aspx?siteid=1&pageid=2157) and [Here](http://rc.majlis.ir/fa/content/iran_constitution), unfortunately not translated.
Comment: @Saeed "[Supreme Leader of Iran](https://en.wikipedia.org/wiki/Supreme_Leader_of_Iran)" is also what Wikipedia calls him. It might not be an *exact* translation from Farsi, but that's the term used in the English-speaking world.
Comment: yes I'm totally aware of that..


Accepting an answer although I did not understand the solution, is it ok?

Question: I sometimes have lost interest in the question or do not want to think through every Detail of an answer of somebody. Since I don't want to be rude I accept an answer so other People do not waste their time. Is there a better way to deal with those situations?
Comment: The title says you don't understand the solution; the body says you have lost interest in the question. These are two very different things. Which one do you actually mean to ask about?
Comment: Well it's sometimes connected I usually hope for a solution that I understand Right away but then I get a solution which requires some knowledge I don't have. Often it is a Problem that is if you have advanced understanding it is easy to solve. But since I don't have those prerequisits there is often some kind of trick involved.
Answer: Accepting is not mandatory. If the answer isn't helpful because you don't understand, then I hope you don't accept it, but instead, comment asking for more clarification (as long as it's within the scope of the answer. If it starts to get tangential, then posting a follow-up question is the recommended way)
From What should I do when someone answers my question?

Accepting an answer is not mandatory; do not feel compelled to accept the first answer you receive. Wait until you receive an answer that answers your question well.

Also, from What does it mean when an answer is "accepted"?

Accepting an answer is not meant to be a definitive and final statement indicating that the question has now been answered perfectly. It simply means that the author received an answer that worked for them personally.
(Emphasis mine)
Comment: From now on I will leave the Questions unaccepted then. About follow-up Questions however I did this a couple times but there is usually a commentor who tells me that I have already asked a similiar Question.
Comment: @RM777 It's not clear you've tried leaving a comment to the answer. With me at least several times, & I've seen it happen in other cases, the OP asks for clarification. With myself & at least a fairly large majority of other cases, the answerer responds to try to ensure it's understood. As far as I know, this was fully resolved for my answers, plus also for most other cases. However, if this doesn't work & you ask a new question, make sure you reference the original question & only ask about what you're unsure of. I've seen this done successfully a few times, even with somebody else asking!


Would it be worth it to start mining bitcoins at this point?

Question: My budget for mining hardware is $600. Would there be an ASIC miner that I could buy for this that would return this and also net a decent amount of profit within a month or so? Is it even worth it for beginners without tons of money to invest in it now?
Comment: The economics of mining guarantee that the answer to this question will always be "no". If it was that easy, everyone would be doing it, raising the difficulty until it was no longer that easy.
Answer:
Is it even worth it for beginners without tons of money to invest in
  it now?

Short answer
No.
Longer answer
I spent over $2400 in ASIC mining equipment from butterfly labs. I started out churning an impressive 120GH/s. I've been running 24x7 and am a little over a month in... I've mined ฿0.78
Last night my rig crashed. When it came back on I was down to 100 GH/s. I can only assume that one of the on board chips failed. There is apparently no recourse to this loss.
Couple things to note... The difficulty rate is increasing exponentially, at the start I was earning ฿0.03 ($33) per day today I'm done to ฿0.02 ($19) for the same rig and the same approximate contribution to the mining pool. In March, the new 600 GH/s miners come out, at the same price range as the rig I'm running now. I expect that my earnings with the current rig will tank, and at that point be less than the electricity I'm burning to stay hashing.
My expectations / hope is to recover the ฿2.5 necessary to break even before the rig's mining rate becomes a negative investment... it's unlikely.
Note that In my recovery cost calculation, I'm considering the 700w of power used to operate the ASIC chips only... my 'computer' is a raspberry pi and has a negligible power consumption rate.
So to answer your question directly... No, even with a large budget, the hamster wheel will keep you in the roughly same spot. It's likely a better investment to simply buy the btc on speculation through coinbase or mtgox than to waste your time setting up a rig that requires you to be a relatively competent system admin just to get started. What I mean by that, is that I had to 'flash' a unix system onto the pi and download / compile bfg miner just to get started. Additionally it makes ALLOT of noise, and finding a place to keep it from bugging the family was hard (and I have a large 2800 sqft house).
Comment: Bitcoin mining is almost a text-book example of a perfect competition market! You need to run ever faster just to stay in the same place - the only way to actually make money is thru continuous innovation.
Answer: It's impossible to predict the income from mining a month out, but it is extremely unlikely that anything on the market would break-even. This is mostly due to the laws of supply and demand - there is significant demand from people who either don't care about breaking even or don't understand the risks. As long as these people are buying miners, anything at a reasonable price is likely to sell out very fast.
Answer: I am not an expert, but according to your budget, it would not be cost effective.
For instance, for you to make enough coins to break even, you need to invest at least US$3000. But the problem is that there isn't any ASIC machine now that costs that much. You can try CoinTerra. They have a 2 THash/s miner that can make you a good amount of money, but you will have to expend about US$6000 dollars for that unit.
Answer: I have with a similar budget and bought ASICMiner Block Erupters (US$16/per, pre US$400 BTC). My goal was to learn about Bitcoin and cover the electricity cost of running a production server. My setup is earning about US$30 per month (at the present Bitcoin value) and the server consumes about 145 - 155 kWh per month. But then my objectives are modest, and I'm not expecting to contribute to my 401(k)... Good luck.
Comment: How much does the electricity cost you?
Comment: My states (OH) electricity cost is US$0.12/per KWh.  Update: My small setup is netting between US$12 and US$20 a month in Bitcoin (.01BTC).  And it's getting harder to mine as the hashing difficulty goes up and more people get in.  Started mining in November at .00008900 proofs per block (at 1Ghs) but now down to .00006900 proofs per block.
Answer: Your best bet is to just buy a Bitcoin (a full one while you can) and either:
a) wait until the price rises and sell for a profit
b) buy/sell daily for a profit/loss
c) invest money in an alt coin that you feel will succeed in the long run
Mining right now is really just a profit loss for anyone coming in that can't afford a couple thousand dollar miners


What does the term "trimming" most commonly mean in aviation?

Question: Why does an airplane need trim, and what does it do during the flight? Does an autopilot adjust the trim automatically?
Answer: In short: trimming neutralizes the force required to keep control surfaces in a specific position.
Most (if not all) aircraft have some sort of elevator trim control. For example, when the pilot has to keep pulling back on the yoke/stick during a climb, trimming "nose-up" will neutralize that force. The elevator will then remain in the same position without any force required on the part of the pilot. Trimming is usually done by means of a Trim tab on the control surface and is controlled by a trim wheel.
Elevator trimming is used:

During climbs: to maintain a constant air speed and rate of climb
During descents: to maintain a constant air speed and glide path
During level flight: to maintain altitude and speed

Although elevator trim is the most common, trimming can also be done on rudder (quite common) and ailerons (only on larger aircraft).
Rudder trim is used to maintain coordinated flight without rudder input by the pilot. Many single engine planes with powerful engines require rudder trim to offset the "left-turning tendency" caused by P-factor and propellor wash hitting the rudder. Aircraft without adjustable rudder trim will usually have a fixed trim tab on the rudder.
Most autopilots will control the elevator trim wheel because the servos controlling the elevator could easily be overpowered by the required force.
It's important to note that in most cases (especially on small airplanes) trimming doesn't actually move the control surfaces. It changes the force required to deflect the control surfaces. Although there are many types of trimming devices, the common trim tab makes the airflow do all the work. The trim tab causes the airflow to push the control surface in a specific position. On larger aircraft with hydraulically operated control surfaces, trim tabs are less common (see also this answer to another question)
Answer: The purpose of trimming is to free the pilot from having to exert a constant pressure on the controls. This is often used to maintain straight and level flight, however trimming can also be used at any phase of flight - for example to maintain a constant rate of climb or descent.
The most basic form, as found on most light aircraft is elevator trim. Usually operated by a wheel, it moves the elevator up or down by a small amount in the same sense as the yoke (back to go up, forward to go down). This can be used to settle the aircraft into straight flight.
Another form of trim is rudder trim. Often found in larger light aircraft and twin-engined aircraft it can be used to adjust for a crosswind to keep the aircraft flying straight. On multi-engine aircraft it can also be used to trim out the differential thrust caused by one engine failing.
Comment: Most autopilots do trim. Also, trimming is not just for straight and level flight. It's used in every phase of flight, including climbs and descents. In fact, it's even more important to trim correctly during climbs and descents.
Comment: Rudder (trim) is not used to adjust for crosswind (except on final approach, but that's another topic)
Comment: Trim is also needed to maintain constant attitude with changing performance.  E.g. as speed increases, without any control input, the nose will tend to pitch up and the aircraft will climb.  Concorde automatically moved it's fuel around to compensate for changing performance and shifting CofG.
Comment: Interestingly, I've also heard this same term used in submarine operation, in relation to climb and dive.  One trims the ballast
Comment: I've never heard of trimming to adjust for a crosswind!  (Also, you forgot to answer the portion of his question about the autopilot.)
Comment: @PhilippeLeybaert - Very true. Answer updated
Comment: In the small airplanes I fly, we adjust the rudder trim for cruise only (and typically it is already set where it should be this is the whole point no need to touch it unless it's off). Every other phase of flight is just dealt with by rudder pedal pressure. The opposite is true with elevator trim, it is used for climb, cruise, descent, and essentially anytime the aircraft needs to be stabilized at a certain airspeed.
Answer: Trimming is changing the stability of an aircraft in such a way that when no control inputs are given, the aircraft maintains its attitude and speed. It allows the pilot to release the control input without the aircraft deviating from the intended path. In general the aircraft is trimmed for straight and level flight, but it can also be trimmed for descent or even for turns.
There are various ways in which an aircraft can be trimmed.
Trimming most commonly refers to elevator trim. This involves changing the angle of incidence of a trim tab on the elevator in such a way that when the control column is released the aircraft does not pitch up or down by itself. In large aircraft, the angle of whole horizontal stabilizer can be changed to trim the pitch tendency of the aircraft.
Aircraft that have a fuel tank in the tail can move the centre of gravity by transferring fuel between forward and aft fuel tanks. Use of CG trim not only affects the pitch tendency of the aircraft but also reduces the fuel burn since less aerodynamic forces are needed to balance the aircraft, thereby reducing the drag.
Other forms of trim are aileron trim and rudder trim. These are used to nullify  any asymmetric characteristics of the aircraft. These characteristics can be caused for example due effects of propeller wash, mechanical deformation of the aircraft (or poor manufacturing tolerances) or engine out situations.
On most larger aircraft the autopilot uses elevator trim or horizontal stabilizer trim to control the aircraft in pitch in addition to elevator control. For turning, ailerons and rudder are used, the asymmetric trim is not used by the autopilot.
Comment: Nicely put, but I wouldn't say that trimming "changes the stability" of the aircraft.  If it is out of trim, it is still stable.  It just wants to stabilize out somewhere other than where you want it to.  :)
Comment: Haha, yes I do, but the very first sentence of your answer says that "Trimming is changing the stability of an aircraft...".  Just thinking that there is probably a better way to say that.  :)
Comment: @Lnafziger nowhere did I intend to imply that an untrimmed aircraft is not stable. I considered adding a sentence about ensuring that the poles are always in the left half of the complex plane, but I think that won't make it clearer for most readers. (you have a background in engineering don't you? :-)
Answer: Autopilot theoretically could not care about the trim but if you disconnected it and plane was out of trim in could depart flight path rapidly.
Comment: "Theoretically" it doesn't care about trim, but the servos of the autopilot are usually not powerful enough to control the elevators if not properly trimmed.
Answer: Say you have trimmed an Aircraft than forces on aircraft i.e Lift == Weight & Thrust == Drag. So aircraft is flying (straight and level) or climbing or descending at constant speed or rate(of climb or descend).
Simple to remmember, Trimmed Aircraft means Lift = Weight and Thrust = Drag thats it.
There are lot of way to trim an aircraft: Trim Tabs on control surface, complete surface moves to trim corresponding control surface (ex: stabilizer moves in response to pitch trim command) etc.
Comment: Lift != Weight when climbing or descending.  :)
Comment: @Lnafziger Now you've opened a can of worms...
Comment: @Lnafziger: Yes, during change of phase of aircraft (climb, cruise, descent etc) these forces will not be equal but during constant rate of climb/descent these forces (Lift = weight or Drag = Thrust) are equal. I usually remember trim to be analogous to inertial i.e unless there happens to be some change [rate/direction/..] on aircraft, its always in trim state.
Also, the below article can explain it much better : http://www.pprune.org/archive/index.php/t-268982.html
Comment: Trimming isn't a matter of equalizing lift to weight (for instance), it's a matter of equalizing forces on a control surface, by creating very little lift on the trim surface. This small force combined with the distance between the rotation axis of the control surface and the aerodynamic  center of the trim surface is sufficient to cancel any torque from the control surface, hence any feedback on the control used by the pilot. The trim force could be created using hydraulics (no trim surface, no lift change) as well, the result would be the same.


Seeking Supervised Classification Imagery for rooftops

Question: I'm trying to do a supervised classification in ArcGIS Pro that will allow me to find Tar and Gravel rooftops in Miami.
I have Landsat data but just wondering if there is imagery out there with better spatial resolution that might work better?
Comment: Plant has 3m and 72cm daily 4-band imagery: https://www.planet.com/products/monitoring/
Answer: Sentinel-2 has a higher spatial resolution (10x10 m  in VIS+NIR) compared with Landsat series (30x30 m, 15 m in panchromatic), so your results must be more accurate. Also, is a free to use sensor.
Here you can compare spectral resolutions:
Comment: I'm a bit new to this. I know spectral resolution is pretty important for image classification. Does the Sentinel 2 have as good a spectral resolution? Having a bit of trouble reading the image you posted. I know Landsat 8 has 8 bands. From what I've read Sentinel only has about half that.
Comment: @Beau Sentinel-2 has some bands in 10m, 20m and 60m. In 10m resolution, has RGB + NIR; in 20 m, has far red (a.k.a. red edge) + NIR  + SWIR; and in 60 m, has some bands to retrieve quality data.
Comment: Do you think RGB+NIR will be good enough for ArcPro to tell the difference between Tar and Gravel rooftops and everything else or that I may need more bands?
Comment: Spectral profiles of this kind of material are almost a line, so you should be ok. But 10 m isn't enough to compute differences on small buildings but is the better spatial resoution found on free imagery
Comment: Thanks for all the help! All the rooftops I'm looking at will be industrial and so should be a bit larger. Also they tend to be all one material. I'm hoping to get at least a sample of what should be Tar and Gravel, then do some ground truthing with Google Earth.
Comment: @Beau you welcome. IF you want, you can close this topic by checking this answer as accepted
Answer: Within the United States there is the National Agriculture Imagery Program (NAIP), which has 4-band imagery available every few years at 1m resolution. If you're using an ESRI product, it is very simple to load/analyze/export this data directly from the United States Department of Agriculture (USDA) Aerial Photography Field Office (APFO) via their Image Server: https://gis.apfo.usda.gov/arcgis/services
Note: This isn't a link that will open in a browser. You must add a new GIS Server in ArcGIS and point it to this address.
I have had great success with supervised classification between rocks and asphalt using NAIP and other 4-band imagery in the past.


Can I share /var and /usr among different distros?

Question: I currently have one very big partition in my laptop that runs Ubuntu. I have to install Fedora for work and I'd also like to try out OpenSUSE, so I'll have to repartition. Since I don't want to duplicate data, I will move /home to a different partition and mount it from all three. I'd like to know, can I also do this with /var and /usr? If so, would that mean that every program I install will be available from all three?
Comment: You may wish to install Fedora and OpenSUSE in their own virtual machines.  Saves having to repartition and reinstallation of Ubuntu.
Answer: No, you cannot. Programs/libraries in /usr could be different for each distro and may not be compatible as is. Also do not share. Likewise, /var cannot be shared as different versions of the same program that are present in different distros may treat the data in /var different.
I HIGHLY advise you do not do this if you want to maintain a working system.
If you need to understand what each directory does in general, please see this Wikipedia article
Answer: Yes you can, but don't.  The main point of having distributions, and not working with Linux raw, is that the people who put the distributions together have figured out how to have all these programs working together alongside each other.  As soon as you try to mix and match between them, you are going to be having to figure all this stuff out for yourself.  And the packagement management systems of the distributions will suddenly become your enemies.
Having said that, on my Mac Os laptop, I have been using two package managers alongside each other: the ghastly Fink and the equally ghastly, now defunct DarwinPorts, and it sort of works, because both of them take a little bit of care not to touch on each other's feet, or interfere with the Apple installation.  And they do that... by mainatining their own /usr and /var hierarchies, under /opt and /sw.  It's crap: I have three installations of Perl 5.8, and it's all I can do to make Fink believe that I have a 5Gb Tex Live installation and not add another Tex installation of its badly configured own.


Odoo Warning - Validation Error

Question: I've just installed odoo v9 on my Ubuntu server. It seems OK but if I update quantity on hand in product, it gives me this error. Can anyone help me resolve this?

The operation cannot be completed, probably due to the following:

deletion: you may be trying to delete a record while other records still reference it
creation/update: a mandatory field is not correctly set

[object with reference: weight_uom_id - weight.uom.id]
Answer: Odoo is saying about you should reference this product to some UoM (Unit of Measure) record. If you don't have any (UoM), create one and then try it again.

Odoo Warning - Validation Error


Designing PVC structure

Question: I am an electrical engineering student that wishes I could have taken some civil engineering courses. Anyways I'm trying to design a pvc structure that I will use as a somewhat complicated room divider. I have the basic design drawn out, but I'm not sure how to design for stability and loading (eg, how many supporting beams to build). I'm familiar with Solidworks and should be able to sketch up a design to do stress testing if that's something useful? I did some basic mechanics from first year, and know how to setup equilibrium equations but I'm not sure if that would be of any help in the design process. I'm open to learning new mathy thing and would love to treat this as a learning experience to solve a practical problem. A nudge in the right direction would be appreciated. Thanks!
Comment: Let's see this basic design drawing then!
Comment: You could by a book, if you're after a general way to learn the topic. You could easily for the universities library and borrow one. If you want more specific advice, you may want to ask a more specific question.
Answer: The analysis of the structure will greatly vary depending upon the loads, application, section size, etc. Expanding the description of the structure will greatly help in providing specific steps in designing.
The first step would be to estimate the loads on your structure (you most likely may need a safety factor). Your second step would be to have a rough guess at how many members, supports and size sections are required to sustain the loads and then analyse it by hand or using Solidworks. Making use of the stresses found, verify if the members you have selected provides adequate strength. Else design accordingly from first principles and complete the analysis again.
You may be required to reiterate the process a couple of times to get the ideal solution. Also considering it is a room divider, major design procedures will most likely not be required.

Designing PVC structure