Is it possible to wipe SSD with strong magnetic force?

Question: I know it is possible to wipe a hard disk, but I'm wondering if something similar can be done to SSD disks as well?
Comment: Actually it's really not that practical to reliably wipe a normal hard disk drive with a magnet unless you have some industrial grade magnets : http://www.pcworld.com/article/116572/busting_the_biggest_pc_myths.html. The article also mentions flash based storage: "A magnet powerful enough to disturb the electrons in flash would be powerful enough to suck the iron out of your blood cells" - Bill Frank, executive director of the CompactFlash Association
Comment: Do you want to wipe it or are you wondering whether there is risk of it being accidentally erased?
Comment: To securely wipe a flash drive, industrial *shredders* would be more practical than industrial magnets.
Comment: I'm curious if it is possible
Answer: Flash memory uses floating gate transistors to store data, rather than the magnetic method used by hard disks. The presence of a magnetic field is not necessarily a problem for an SSD, but the rate of change of magnetic flux could cause damage:

CFs [Compact Flash drives] aren't magnetic media, so they can't be erased like, say, a floppy disk or a hard drive. However, depending on the strength of the magnetic field, a CF isn't completely safe. For instance, if you were to do an MRI of your CF (or any other piece of sensitive electronic circuitry, for that matter), it would be toast. It's not simply the strength of the magnetic field that matters, so much as the rate at which the field changes. If you go from strong field to no field very quickly or vice versa, then the change in magnetic flux can generate small voltages over wires, traces, etc. If the voltages are high enough, then they can cause damage. I don't know, practically, in the real world, what sources of magnetic fields might pose a danger to a CF -- or a camera -- or a lens.
Comment: I'd like to emphasize that this isn't a **practical** danger:  you're not going to wreck your SSD drive by using your magnetic screwdriver, or even waving your [singing monkey balls](http://www.thinkgeek.com/geektoys/cubegoodies/8c94/), near it *(in fact, magnetic screwdrivers are pretty safe to use near normal magnetic hard-drives as well)*.
Comment: What about a geomagnetic storm  https://en.wikipedia.org/wiki/Geomagnetic_storm?
Comment: @VojtěchDohnal Not a problem unless you're in space, where you need specialised electronics anyway (by adding three zeroes to the price tag).
Answer: I was just exploring this in my science class the other day (my friend and I had finished early so we had a good 15 minutes or so to muck around with what the teacher called super magnets) and I can safely say that it depends what you do with the magnet, the strength of said magnet, and on the USB stick itself. If you simply leave the magnet sitting on top of the usb, they will be attracted but the USB won't be wiped. If, however, you swipe the magnet over the USB many times in rapid succession, then you may wipe it, and depending on the speed and strength of the magnet you could also render the USB unformattable. My friend's USB was renered completely and utterly useless after this experience, while mine (which was put in pretty much the same kind of conditions) was perfectly fine, even after I threw it at the fan a few times (don't ask haha). Now, I have a magnetic USB! It even manages to stick to the fridge, supported by nothing but it's magnetic powers. But it still works. By the way, my USB is a $10 Kodak 8 GB which I bought from target, but my friend's was a $20 USB from a very reputable computer shop. So money doesn't always matter.
P.S My friend's USB broke when I threw it at the fan :P
Comment: Very unscientific experiment, but so crazy and fun that I just have to upvote it.
Answer: No, because flash memory devices do not use magnetism to store data the way hard drives do.  For example, SanDisk SD cards are rated to withstand static (not changing) magnetic fields of up to 5000 gauss.
However, as sblair noted, sufficiently strong, changing magnetic fields can damage any electronic equipment, including flash memory devices.  This is due to electromagnetic induction producing electrical currents inside the circuitry that are strong enough to damage the hardware.
For reference, according to Wikipedia, an MRI scanner can generate magnetic fields ranging from 600 to 70000 gauss, depending on the model and operating mode, while a typical refrigerator magnet generates about 50 gauss.  Note that MRI scanners generate changing magnetic fields which can easily damage most electronic equipment.  However, unless you're moving a strong magnet at high speeds (such as by rapidly rotating it), normal, everyday magnetic objects will not damage an SSD or other flash memory device.  Also, you can use a Faraday cage to protect devices against electromagnetic induction.
Answer: No.  Flash memory is a silicon-based technology where traditional disk uses magnetized particles.  I suggest the use for Darik's Boot and Nuke (DBaN)

Comment: Thanks, I should have been more clear that I'm just curious if such thing is possible. +1 for good alternative altough
Comment: or `dd if=/dev/random of=/dev/sdb` or whatever the block device is.
Answer: yes, It is possible for flash memory to be wiped but not simply, by a magnet, It has to be exposed to a changing magnetic field for a certain period of time; the induced current will interact with your flash media overtime rendering it useless.Short term exposure may not affect your flash media, however the longer the exposure the more the damage that occurs to your device. I have proven it though not purposefully, my 8G unirex microSD got stuck behind the screen of one of my devices for an extended period. When it was finally removed and i placed it into an adapter and loaded it onto my laptop I found that the usable memory was reduced to 30mb. Also, it was rendered unformattable.


Fixing a hardwood floor mistake

Question: Following a YouTube video, I tried to minimize some scratches in a hardwood floor (installed by previous owner) with Weiman Wood Floor Polish and Restorer, and instead made them look worse. See photo. How can I undo this? Thanks!
Answer: The only issue I can see is that the scuffs lack the sheen of the original finish. I'd try a wax or other polish to try and get some of that shine back. That might be all it takes.

Fixing a hardwood floor mistake


How can I let the user choose his own background image?

Question: Dear Stackoferflow Fourm I would like to have a function in my Android Game Programming that allows the user to choose his own background image (I would like to let the user change the plane image) Unfortunately I have no idea how I could do that. If someone knows how to do it I would be very happy.!
Comment: Where is the new texture supposed to come from? Do you have a set of textures to choose from build into the game? Local filesystem? Internet URL?
Comment: I want the user to upload his picture from the local filesystem.
Answer: At it's most fundamental, you need to load an image into a texture and then apply that texture to a material. You can do that as follows:
<code> public void SetImage(string filePath) {
     // Create a variable to hold the texture
     Texture2D tex = null;
     byte[] fileData;

     // Check file exists
     if (File.Exists(filePath)) {
         // Read contents into a byte array
         fileData = File.ReadAllBytes(filePath);

         // Create a new texture and load the image data
         tex = new Texture2D(2, 2);
         tex.LoadImage(fileData);
     } else {
         Debug.LogWarningFormat("{0} not found", filePath);
     }
     // Set the main texture for the material on the current object's renderer
     this.GetComponent<Renderer>().material.mainTexture = tex;
 }
</code>
The more interesting part comes when you want to do this with a user-selected file.
First of all, you need to work out which platforms you want to support. A file browse dialog on Windows is radically different to one on Android.
Next, you need to decide how long this will persist. If it's just until the game closes, you're fine.
If, on the other hand, you want to persist across game restarts then you need to do one or two things:

Pick/develop a mechanism to allow you to remember which file (the|each) user chose.
Optionally make a "safe" copy of the image somewhere in your application's data directory, so that if the original is deleted, you can continue to show it in-game. [again, this will depend significantly on which platforms you support]


What might be eating my butter bibb lettuce plants?

Question: I live in southwest MN and have started growing some vegetables in containers. We had a big storm, so I put the pots on the ground beside my porch because they always get blown over. Today, I noticed that my butter bibb lettuce is essentially gone. It's been consumed by something. I looked at what was left and saw tons of little black bead looking things all over. They look like caviar. I can't tell if it's excrement or eggs of some kind. Every bit of the leaves are gone except the spiny part. I have 5 other pots of veggies around it but this is the only one this happened to. Does anyone have an idea what these things might be? Thank you.
Comment: closeup picture please
Comment: Sounds either like caterpillar poop or slug eggs...
Answer: Definitely need pictures.  Sounds like rodents if the size of these pellets are the size of caviar! Either that or a big ole cut worm...and it takes only one cutworm to make this kind of damage.  I'd go out tonight with a flashlight!  If you find a big caterpillar that curls into a ball when disturbed...sigh, just cut him in half with scissors.  Send pics so we can tell whether the poop is from rodents or insects.  Cutworms are easy and my money at the moment would be on cutworms...rodents love fruits like tomatoes, eggplant. If it is cutworm, go out for a few nights to kill (sigh) the few you will find.  Never ever have seen more than one or two but terrific damage.  No pesticides are indicated!  Do you have slugs?  You should see 'slime trails' and again going out at night for a few nights to (sigh) chop these guys in half works better than any pesticide or other treatment I know about! You HAVE GOT TO SEE what it is that is doing this damage!!  It is a BIG no-no to guess and do treatments without knowing for certain what you are dealing with.


How do you change the titles displayed inside infowindows in Carto?

Question: The titles in my infowindows are copied straight from my column headings in the underlying data... So it says "STREET_ADDRESS" when I'd like it to display "Address" or "YEAR" when I'd like it to display "Year registered"
Usually, Carto is point and click for these kinds of options, but I'm hitting a wall.
Answer: There is toggle "HTML" in bottom part of the screen. This opens view, where you can edit more data, including title headings within
 element.
Answer: In addition to @JaakL response, you can also rename the column name with a custom value. As you said, it just (double) click and point!


Taxi to spot?? Hot spot? What is meant by this?

Question: I heard ground controller at KPHL say taxi to spot so and so?
What do they mean by this during taxi procedures.
Comment: Can you provide an audio link or something? It's sometimes a little tough without context
Answer: The word "spot" just means a designated place, or part of the airport where the aircraft is to be parked and shut down.  Sometimes they are numbered.  Presuming the pilot knows where that is, the controller is simply clearing them to go there.
Answer: A spot will be just a place on the airport surface. Generally these are termed as specific locations such as the blank ramp for example. A "Hot Spot" is a specific location that is a known hazard for aircraft for one of numerous reasons. These reasons could be from a history of confusing pilots or just from common sense and logic. Some Hot Spots are designated where several taxiways and or runways intersect. They can be Considered hazardous because pilots in the past have confused taxiways for runways and/or runways for taxiways. Some Hot Spots are considered hazardous because Towers view of that area is blocked by obstacles or obstructions. Known Hot Spots are marked and numbered on some airport taxi diagrams to alert pilots of the hazard.
Answer: The airport layout is represented in terms of aprons, taxiways, Ramps, gates, bays and sometimes uncommon words like loops, spots etc. The same is very clearly marked on airport charts and is easily locatable if one cares to look.
Hot spots are typically intersecting taxiways where there is a possibility of conflict of aircraft on the move. These are also marked on the airport charts and are recommended to be briefed between pilots.


Headlights won't turn on & taillights won't turn off

Question: I have a 1998 Nissan Altima. My headlights won't turn on, but my parking lights and tail lights won't turn off unless I unhook my battery. Any ideas what the problem might be? Or a solution?
Comment: This sounds like the parking lights are grounding through with a fault. For some reason (I need to look it up to confirm), I am thinking that the lights (parking, signal, brake, and head) use the power in a different order than does most other things. When you switch something on, you are actually switching the ground on, not the power. So, what can happen is, if you get a ground fault, it could actually turn your lights on without the switch ... and leave them on when you don't want them to be. This wouldn't answer the headlight issue, though. Just a thought, not an answer.
Answer: The first place to look for the headlights would be the fuse panel(s). Often there are two: one inside the passenger compartment, either at the driver or passenger kick panel or on the side of the dash where the door covers the dash on the driver side. The other is the engine compartment (in a black plastic box--diagram will be on the inside cover or on the internet).  Next check the headlight relay(s). These are usually (but not always) in the engine compartment in a black plastic box.
If the fuses are okay, the relays are easily checked by finding an identical # relay in the box that you know is working (sometimes the horn relay is a good one to try) and swap it into the position you want to test, then test it.
For the lights that are staying on, there could be a ground in the switch stalk that is keeping a relay energized (yech ... replacement stalks are not cheap and can be a pain, especially if you have air bags), or the relay could have failed in the "on" position.  If you pull that relay, the lights should go off. Again, swap it with a good relay and if the lights come on again, you know the problem is in the switch wiring. If they don't come on, you know the old relay was bad.
Let us know what happens.
Answer: It won't turn off - Tells you the light switch is bad. Get a new one.
Comment: @GabrielMongeon - I disagree with you saying this is not an answer. *It is an answer*, just not a very well written one. I vote to leave it alone, but would suggest it should be fleshed out some as to the *why* this is the answer. It should hopefully tell the OP *why* this is the issue.
Comment: This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post - you can always comment on your own posts, and once you have sufficient [reputation](http://mechanics.stackexchange.com/help/whats-reputation) you will be able to [comment on any post](http://mechanics.stackexchange.com/help/privileges/comment).


Relation of Digital Logic Design to Electrical Power Engineering?

Question: I'm an undergraduate student of Electrical Power Engineering currently in 3rd semester, one of the courses we  study is Digital Logic Design(dld) and I have found much interest in it but I am unclear whether the subject would have application in our field i.e. power engineering or not....Could anyone guide me that how should I study dld with what things in mind related to future perspective?
Answer: Below is a job description for a Senior Electrical Engineer position at Princeton power systems to help you with future perspective. Princeton Power System makes power inverters for the Renewable Energy market. As you would see few key words that address the relationship between Digital Logic Design and Electrical Power Engineering.

FPGA – Field Programmable Gate Array
Power Electronics
Microprocessors

Senior Electrical Engineer
Job Description: You will be a key member of the Product Development
team developing state of the art Power Conversion products for use in
Alternative Energy, Renewable Energy, Energy Storage, Micro-Grid, and
Backup Power applications. Tasks will include design of power
conversion systems, design of electrical control circuitry,
development of control algorithms and software, performing
system-level analysis and design, printed circuit board design, and
supporting fabrication and testing of components and systems.
Responsibilities:

Control system and auxiliary electronics circuits design
Overall system architecture and schematic design
Printed circuit board design and design supervision
Simulation or analysis of electronic circuits ranging from small electronics to high-power electronics
Software development for microprocessor and FPGA-based control
systems and PC-based graphical user interfaces
Electrical system test procedure development, testing, and test reporting
Analysis of system design reliability and design for reliability
Generation of electrical schematics and manufacturing-related documentation

Required:

At least a Bachelor's degree in Engineering or other pertinent field.
Detailed understanding of modern electrical engineering principles and practice
Experience with printed circuit board design

Ideal:

Experience with high-power electronics
Software development experience
Experience with system simulation

Most of Supervisory control and data acquisition (SCADA) have microprocessor and/or FPGA, thus the close relationship between Digital Logic Design and Electrical Power Engineering.
Hope this helps with some ideas related to future perspective and the relationship between Digital Logic Design and Electrical Power Engineering. Investigating Renewable Energy Industry and power electronics related supervisory control system might be a good start.

References:

FPGA implementation of a fastflex supervisory control and data acquisition (SCADA) remote telemetry unit
RTU hardware design for SCADA systems using FPGA
Answer: Having studied electronic and electrical engineering, I covered both the power/analogue and the digital part. There were certain power designs where using a digital microcontroller (to generate a square wave of a certain time period and duty ratio) helped.
There are methods of obtaining oscillators using discrete analogue components (a Wien Bridge oscillator), but incorporating a 555 timer (digital) makes things much simpler.
Digital Electronics are used in systems control, so it still has relevance to eletrical engineering.
Digital Logic Design and VLSI technology were still my favourite topics as it shows how the theoretical boolean logic is implemented using hardware a nano-scale.


Equivalent of Oracle's RowID in SQL Server

Question: What's the equivalent of Oracle's RowID in SQL Server?
Comment: Stephanie: the assumption is that there is a unique key in the data, which assumes the data is normalized, which is an incorrect assumption sometimes. Thus, what's the equivalent to Oracle's RowID in SQL server.
Answer: From the Oracle docs

ROWID Pseudocolumn
For each row in the database, the ROWID pseudocolumn returns the
address of the row. Oracle Database rowid values contain information
necessary to locate a row:

The data object number of the object
The data block in the datafile in which the row resides
The position of the row in the data block (first row is 0)
The datafile in which the row resides (first file is 1). The file
number is relative to the tablespace.

The closest equivalent to this in SQL Server is the rid which has three components File:Page:Slot.
In SQL Server 2008 it is possible to use the undocumented and unsupported %%physloc%% virtual column to see this. This returns a binary(8) value with the Page ID in the first four bytes, then 2 bytes for File ID, followed by 2 bytes for the slot location on the page.
The scalar function sys.fn_PhysLocFormatter or the sys.fn_PhysLocCracker TVF can be used to convert this into a more readable form
CREATE TABLE T(X INT);

INSERT INTO T VALUES(1),(2)

SELECT %%physloc%% AS [%%physloc%%],
       sys.fn_PhysLocFormatter(%%physloc%%) AS [File:Page:Slot]
FROM T

Example Output
+--------------------+----------------+
|    %%physloc%%     | File:Page:Slot |
+--------------------+----------------+
| 0x2926020001000000 | (1:140841:0)   |
| 0x2926020001000100 | (1:140841:1)   |
+--------------------+----------------+

Note that this is not leveraged by the query processor. Whilst it is possible to use this in a WHERE clause
SELECT *
FROM T
WHERE %%physloc%% = 0x2926020001000100

SQL Server will not directly seek to the specified row. Instead it will do a full table scan, evaluate %%physloc%% for each row and return the one that matches (if any do).
To reverse the process carried out by the 2 previously mentioned functions and get the binary(8) value corresponding to known File,Page,Slot values the below can be used.
DECLARE @FileId int = 1,
        @PageId int = 338,
        @Slot   int = 3

SELECT CAST(REVERSE(CAST(@PageId AS BINARY(4))) AS BINARY(4)) +
       CAST(REVERSE(CAST(@FileId AS BINARY(2))) AS BINARY(2)) +
       CAST(REVERSE(CAST(@Slot   AS BINARY(2))) AS BINARY(2))

Comment: On SQL Server 2005 you can use the undocumented and unsupported virtual columns %%LockRes%% instead
Comment: absolute correct. %%LockRes%% is not the "correct way" - only use if for qucik and dirty fixes to data on old versions of sql servers pre 2008
Answer: I have to dedupe a very big table with many columns and speed is important.  Thus I use this method which works for any table:
delete T from
(select Row_Number() Over(Partition By BINARY_CHECKSUM(*) order by %%physloc%% ) As RowNumber, * From MyTable) T
Where T.RowNumber > 1

Answer: If you want to uniquely identify a row within the table rather than your result set, then you need to look at using something like an IDENTITY column. See "IDENTITY property" in the SQL Server help. SQL Server does not auto-generate an ID for each row in the table as Oracle does, so you have to go to the trouble of creating your own ID column and explicitly fetch it in your query.
EDIT: for dynamic numbering of result set rows see below, but that would probably an equivalent for Oracle's ROWNUM and I assume from all the comments on the page that you want the stuff above.
For SQL Server 2005 and later you can use the new Ranking Functions function to achieve dynamic numbering of rows.
For example I do this on a query of mine:
select row_number() over (order by rn_execution_date asc) as 'Row Number', rn_execution_date as 'Execution Date', count(*) as 'Count'
from td.run
where rn_execution_date >= '2009-05-19'
group by rn_execution_date
order by rn_execution_date asc

Will give you:
Row Number  Execution Date           Count
----------  -----------------        -----
1          2009-05-19 00:00:00.000  280
2          2009-05-20 00:00:00.000  269
3          2009-05-21 00:00:00.000  279

There's also an article on support.microsoft.com on dynamically numbering rows.
Comment: This is true, but that fits the definition of ROWID that I see in the Oracle docs: "The external datatype ROWID identifies a particular row in a database table"... but I see you're saying this because of my typo at the top. :) Thanks for pointing that out.
Comment: I think an identity column uniquely identifies a row in a table but not in a database.
Comment: A row "number" is not a ROWID. The ROWID contains the physical location of the row it something different than a unique number. Especially it's unique accross all tables in the database (with some exceptions when special storage techniques are used)
Answer: Check out the new ROW_NUMBER function. It works like this:
SELECT ROW_NUMBER() OVER (ORDER BY EMPID ASC) AS ROWID, * FROM EMPLOYEE

Comment: I think this is a replacement for rownum and not rowid.
Answer: Several of the answers above will work around the lack of a direct reference to a specific row, but will not work if changes occur to the other rows in a table. That is my criteria for which answers fall technically short.
A common use of Oracle's ROWID is to provide a (somewhat) stable method of selecting rows and later returning to the row to process it (e.g., to UPDATE it).  The method of finding a row (complex joins, full-text searching, or browsing row-by-row and applying procedural tests against the data) may not be easily or safely re-used to qualify the UPDATE statement.
The SQL Server RID seems to provide the same functionality, but does not provide the same performance.  That is the only issue I see, and unfortunately the purpose of retaining a ROWID is to avoid repeating an expensive operation to find the row in, say, a very large table. Nonetheless, performance for many cases is acceptable.  If Microsoft adjusts the optimizer in a future release, the performance issue could be addressed.
It is also possible to simply use FOR UPDATE and keep the CURSOR open in a procedural program.  However, this could prove expensive in large or complex batch processing.
Caveat: Even Oracle's ROWID would not be stable if the DBA, between the SELECT and the UPDATE, for example, were to rebuild the database, because it is the physical row identifier.  So the ROWID device should only be used within a well-scoped task.
Answer: If you want to permanently number the rows in the table, Please don't use the RID solution for SQL Server. It will perform worse than Access on an old 386. For SQL Server simply create an IDENTITY column, and use that column as a clustered primary key. This will place a permanent, fast Integer B-Tree on the table, and more importantly every non-clustered index will use it to locate rows. If you try to develop in SQL Server as if it's Oracle you'll create a poorly performing database. You need to optimize for the engine, not pretend it's a different engine.
also, please don't use the NewID() to populate the Primary Key with GUIDs, you'll kill insert performance. If you must use GUIDs use NewSequentialID() as the column default. But INT will still be faster.
If on the other hand, you simply want to number the rows that result from a query, use the RowNumber Over() function as one of the query columns.
Answer: From http://vyaskn.tripod.com/programming_faq.htm#q17:

Oracle has a rownum to access rows of a table using row number or row id. Is there any equivalent for that in SQL Server? Or how to generate
  output with row number in SQL Server?
There is no direct equivalent to Oracle's rownum or row id in SQL
  Server. Strictly speaking, in a relational database, rows within a
  table are not ordered and a row id won't really make sense. But if you
  need that functionality, consider the following three alternatives:

Add an IDENTITY column to your table.
Use the following query to generate a row number for each row. The following query generates a row number for each row in the authors
  table of pubs database. For this query to work, the table must have a
  unique key.
SELECT (SELECT COUNT(i.au_id)
        FROM pubs..authors i
        WHERE i.au_id >= o.au_id ) AS RowID,
       au_fname + ' ' + au_lname AS 'Author name'
FROM          pubs..authors o
ORDER BY      RowID

Use a temporary table approach, to store the entire resultset into a temporary table, along with a row id generated by the IDENTITY()
  function. Creating a temporary table will be costly, especially when
  you are working with large tables. Go for this approach, if you don't
  have a unique key in your table.
Answer: if you just want basic row numbering for a small dataset, how about someting like this?
SELECT row_number() OVER (order by getdate()) as ROWID, * FROM Employees

Comment: But it works for quick added id which some viewers will be looking for, not knowing what ROWID is.
Answer: ROWID is a hidden column on Oracle tables, so, for SQL Server, build your own.  Add a column called ROWID with a default value of NEWID().
How to do that: Add column, with default value, to existing table in SQL Server
Comment: Isnt this more of a comment?
Answer: Please see http://msdn.microsoft.com/en-us/library/aa260631(v=SQL.80).aspx
In SQL server a timestamp is not the same as a DateTime column.  This is used to uniquely identify a row in a database, not just a table but the entire database.
This can be used for optimistic concurrency.  for example
UPDATE [Job] SET [Name]=@Name, [XCustomData]=@XCustomData WHERE ([ModifiedTimeStamp]=@Original_ModifiedTimeStamp AND [GUID]=@Original_GUID
the ModifiedTimeStamp ensures that you are updating the original data and will fail if another update has occurred to the row.
Answer: I took this example from MS SQL example and you can see the @ID can be interchanged with integer or varchar or whatever.  This was the same solution I was looking for, so I am sharing it.  Enjoy!!
-- UPDATE statement with CTE references that are correctly matched.
DECLARE @x TABLE (ID int, Stad int, Value int, ison bit);
INSERT @x VALUES (1, 0, 10, 0), (2, 1, 20, 0), (6, 0, 40, 0), (4, 1, 50, 0), (5, 3, 60, 0), (9, 6, 20, 0), (7, 5, 10, 0), (8, 8, 220, 0);
DECLARE @Error int;
DECLARE @id int;

WITH cte AS (SELECT top 1 * FROM @x WHERE Stad=6)
UPDATE x -- cte is referenced by the alias.
SET ison=1, @id=x.ID
FROM cte AS x

SELECT *, @id as 'random' from @x
GO

Answer: You can get the ROWID by using the methods given below :
1.Create a new table with auto increment field in it
2.Use Row_Number analytical function to get the sequence based on your requirement.I would prefer this because it helps in situations where you are you want the row_id on ascending or descending manner of a specific field or combination of fields
Sample:Row_Number() Over(Partition by Deptno order by sal desc)
Above sample will give you the sequence number based on highest salary of each department.Partition by is optional and you can remove it according to your requirements
Comment: `ROWID` is the unique identifier for an existing record in the server; `ROW_NUMBER()` gives the position (by some specified ordering) of a record in a query - both useful, but *completely* different concepts, without even a tiny sliver of overlap
Answer: Please try
select NEWID()
Source: https://learn.microsoft.com/en-us/sql/t-sql/data-types/uniqueidentifier-transact-sql
Comment: `ROWID` is the unique identifier for an existing record in the server; `NEWID()` is "create me a random guid" - both useful, but *completely* different concepts, without even a tiny sliver of overlap


What strings can I use to get a high-quality sound out of a travelling guitar?

Question: I've just purchased a Washburn Travel Guitar. I know I'll never get full guitar sound out of it, but I was wondering what strings I could / should get to (perhaps) maximise this little guy.
Answer: The same string choice compromises apply with a travel guitar as with any other guitar.
How does string gauge affect a guitar's sound and playability?
So you need to choose.

For loudness: heavier strings
For ease of fretting: lighter strings
For resistance to accidental bending: heavier strings
For ease of bending: lighter strings

If the purpose of this travel guitar is to practice when you're away from your full size guitar, then I would recommend having the same gauge strings on both. You want to replicate the feel of playing, even if the sound is less full and loud.
If the travel guitar has a shorter scale, then it may be worth using slightly heavier gauge strings, to replicate the tension on your main guitar. Use the D'Addario String Tension Guide to look up the tension of your existing strings, and what gauge would approximate the same tension on your travel guitar.
As for factors other than gauge -- the precise alloy used, and so on -- I'm going to lay my cards on the table and say that the differences are too subtle to worry about.
Comment: Cheers buddy thanks for the advice. I've only started playing recently so I won't notice or appreciate subtle differences just yet. I'll probably choose heavier strings just to get a louder, meatier sound.
Comment: @ajmccall I think that's a good idea, if for nothing else than just getting some extra volume out of the guitar =)  +1 slim, good answer.


What component of an aircraft generates its electric power?

Question: What component of an aircraft generates the electric power to start the aircraft's engine?

For a Rotax 912 engine, I think the magneto generates the electricity, but I'm not sure; I also think about the ignition coil or electronic ignition.
Comment: Magneto generates the electric power for spark ignition, not starting.
Answer: For most small planes, it is the battery, which turns the electric starter motor. A generator driven by the engine or by a small propeller in the slipstream then charges up the battery while the plane is flying.
Some history:
a few older and small planes had a pull cord in the cockpit with which the pilot could pull-start the engine, like a lawn mower. For engines with no starter at all, the pilot or their assistant would grab the propeller and swing it around by muscle power to start the engine (be careful!).
Some very old planes had starters operated by a crank that you stuck into a hole in the engine cowling, and turned by arm power. This worked for small engines but was too hard to do for bigger engines. In that case, the crank turned a small flywheel up to great speed and then the engine was geared into the flywheel through a reduction gear drive, and the energy stored in the rotating flywheel turned the engine to start it. This was used in the P-26 "Peashooter" plane.
In later years, a small electric motor spun the flywheel up to speed instead of a hand crank. The Antonov An-2 still uses this type of starter, called an inertia starter, as does the Dromader crop duster with the radial engine.
Another method of starting an airplane engine was to explode a blank shotgun shell in a closed chamber and send the hot gas through a tube to a special cylinder geared onto the crankshaft, which thereby turned the crankshaft to start the engine. This is called a Coffman starter and it plays a key role in the old movie "The Flight Of The Phoenix". In some versions of this principle, the gases from the shotgun shell were sent right into one of the cylinders of the engine itself, forcing the piston down and turning the crankshaft.
This idea saw use in more modern times, where a jet engine could be started by burning a charge of solid rocket motor fuel called a cartridge inside a sealed chamber and using the hot gas to spin up the exhaust turbine. F-4 Phantom jet fighters could be started with cartridges like this in just a few minutes even in Alaskan winters- without the use of a start cart.
Comment: "Another method of starting an airplane engine was to explode a blank shotgun shell in a closed chamber and send the hot gas through a tube to one of the cylinders in the engine, forcing its piston violently down and thereby turning the crankshaft."
Wow!!!!
Comment: @RafaelVega, yes, it's called a coffman starter and it plays a key role in the movie "The Flight Of The Phoenix".
Comment: The battery doesn't GENERATE the electric power, it merely stores generated power for later use.  In many light planes, electricity is generated by an alternator, just as in a car.  In fact, the alternator on my Piper Cherokee was a '60s Chrysler part.
Answer: The magneto generates the spark for the ignition system. While the engine is running it drives an alternator which produces electricity to recharge the batteries and provides power to the aircrafts systems. When the engine is off, the aircrafts power is derived solely from the battery. The battery is used to power the starter motor which gets the engine going.
Comment: Critically there are two sources; the battery to turn the engine over and the magneto to generate a spark.  Although other ignition systems are commonplace in automotive engines these days, magnetos are still used in aircraft engines because they are very simple and therefore hopefully reliable.
Answer: As your question goes, "power to start the engine" may be understood as the power needed to rotate the engine until it is able to rotate itself by its own power. It may or may not be electrical in nature.
It may be the pilot's muscle power in very small engines (just like in smaller motorcycles), a starter battery for bigger engines (just like in cars) or power from a land-bound infrastructure (for big jets).
If you think about the electricity in the spark plugs of a piston engine, there is a catch - electricity for sparks is needed not only to start the engine, but for running the engine as well.
"Magneto" is just a small synchronous generator mounted directly on the engine crankshaft. It serves two purposes - providing power and timing for the electric spark. It is used in small engines (not only in aircraft) that can be started without electricity present (think motorcycle or a lawnmower). The magneto circuit is completely separate from the other possible electric equipment.
Bigger engines that are started by a battery power usually don't have a magneto. Their electricity needs are served by the starter battery (when starting) or by an attached generator (when running) - just like in most cars.
The ignition coil doesn't produce electricity. It just transforms it to the voltage needed for the sparks.
The electronic ignition is just a method to control the ignition coil. It doesn't produce electricity by itself.
Answer: A larger turbine-powered aircraft such as a Grumman G-1 Gulfstream uses an auxiliary power unit to start each of two 1800 hp Rolls Royce turbine engines.  The APU, as it is called, is a self-contained unit in the tail portion of the aircraft.  Specifically, the APU is started by battery, usually from a ground assisted cart.  The cart is essentially a truck with a self-latching-plug electrical cable connected to a male-to-female receptacle on the aircraft.  Such cart services are provided by most executive airports in the United States.  Quite typically, while the aircraft is in ground operation (pre-flight for instance) the APU powers the aircraft.  Use of the APU is discontinued when all aircraft systems are flight ready.


Inconsistent rep behaviour

Question: I recall seeing a mention a little while back about changes to the SE sites that mean rep adjustments are made "on the fly" and recalcs are no longer necessary. I think it's broken, at least on SF. I don't see my rep changing when I cast downvotes and recently my rep suddenly went down by several hundred points, which could really only be the result of a recalc.
Answer: The global reputation recalc is responsible for your rep loss, this happened globally across the network.  Previously, reputation was not real-time or anywhere close, so things that negatively affected reputation were not applied and your actual value vs the highly denormalized value you see got way off sync.
This round of changes aimed to fix that, we not keep your reputation in sync, in most cases instantaneously, in other complicated cases, within 5 minutes.
Downvotes are instantly reflected on your reputation, though the confusion here may be that questions do not penalize you 1 rep any more, only downvotes on answers do this.
Comment: Thanks Nick but, as I mentioned in my question, I was under the impression that recalcs were a thing of the past. Did I misunderstand what I thought we were told or has there been another change?
Answer: The change to instant rep was rolled out gradually to all users. Yours was applied on the 28th of March, however allegedly your rep only changed by one point (and it went up).
However, downvotes are now free for questions so you won't see any rep change because of that. I just did a test by throwing a -1 on a spam answer, and I saw my rep change immediately after refreshing the page.
Hopefully a dev will see this and cast more light.
Just noticed you did spend 500 rep in September 2011 on a bounty. Kudos to you for throwing out a big bounty...
Comment: I think the lost rep was last month (been on leave for 3 weeks and lost track of time completely). As for the bounty, I've often wondered why so many people are so stingy about it. If I want an answer badly enough to put a bounty on it I'd be perfectly happy to offer 10 times the amount. It's not like I'm getting any real value out of having it anyway. The practical difference between 3K and what I have now is not worth a mention.
Answer: Down-votes on questions are free these days, which could be part of it.
The drop by several hundred bit is interesting though. Your history doesn't show any recent recalcs that adjusted to anywhere near that magnitude. The last big one was March 2nd, which was a global rep-recalc.
If the rep-drop is more recent then that, I can't dig out the cause from here. Theoretically the only thing that would cause something of that magnitude is a recent post of yours earning a lot of rep that then gets deleted. Historic questions getting shredded no longer dings rep like it used to.
Comment: It could well be the March 2nd, I really can't remember. It's not that I care about the rep, one way or the other, it's just that I didn't think it should be happening any longer, although Mark's answer addressed that part.

Inconsistent rep behaviour


Number of days of Creation

Question: How many days of "Creation" where there? If the answer is 7, then why is shabbos considered a day of Creation?
Comment: @ShmuelBrin It seems that he was asking 6/7 days, considering his second question.
Answer: The days of B'raishis are referred to commonly by Hazal as Sheishes Yimei B'raishis. However it does say "Vayichal Elokim BaYom HaShvi'i which means the Almighty finished on the 7th day. Rashi is bothered by the fact that the verse said right after Yom Hashishi that "The heavens and Earth and all their hosts were completed". Did Hashem finish on the 7th or the 6th? He answers that Shabbos brought the concept of Minuha, rest to the world. Without the concept of rest the world was not yet complete. The concept of rest means to stop creating. So by stopping, Hashem completed creation. Avin Ezrah (yes, that is how it is pronounced! see http://onthemainline.blogspot.com/2010/01/how-should-we-pronounce-ibn-as-in-ibn.html) says that Hashem resting means He set the laws of nature as constant. It is all there in your Mikraos Gedolos Humash.
Comment: That ניקוד (although I realize not the main point of your post) is blowing my mind. I think this gets back to the question of whether it is more appropriate to pronounce a person's name the way they would pronounce it or the way it is universally pronounced. See: http://mi.yodeya.com/questions/461/did-rav-moshe-feinstein-pronounce-his-last-name-feinstain-or-feinsteen/465#465
Comment: Yes, it blew my mind as well! I just thought it would be interesting to share. BTW, that blog is full of mind-blowing ideas.
Comment: Very interesting use of "Het" and "Sav"
Answer: shabbos is the creation of rest. hashem is teaching us that even he, who created the world, took a day to rest, and so should we.
Comment: yudi b, Welcome to mi.yodeya, and thanks very much for adding your insight here. If you could add a source to your answer, it would be even better. Please consider clicking on "register," above, to create your account. This will give you access to all of mi.yodeya's features and will allow you to take full credit for your contributions.

Number of days of Creation


Life is fleeting, "vitae est labilis"?

Question: Can someone please tell me the appropriate translation for "life is fleeting". So far I have come up with "vitae est labilis".
Answer: This, I guess, is drawing on Horace's Ode to Postumus:
"Sadly, the fleeting years slip away."

Eheu fugaces Postume, Postume, Labuntur anni,

vitae labilis  (without est ) means 'slippery lives,' or 'stumbling lives.'
For 'Fleeting years' Horace chose Fugaces Anni.
'Life is Fleeting,' if you would like to follow Horace, would be Vita Fugax, or Fugax est Vita.
Fugax Fugax II. Trop. A. www.perseus.tufts is the reference.
Comment: *Fugiō* is a good verb for this, cf *tempus fugit*
Comment: Thanks for the quick response, would it be better to simply have vita fugax or something like vita est fugaces or vita fugaces?
Comment: @Hugh *Vitae **sunt** fugaces*? The singular form is a far better choice, though.
Comment: @Draconis Can you write a separate answer around that idea? It's worth more than a comment.
Comment: Not 'vita est fugaces' because -st f- is awkward to pronounce; and it would have to be 'vitae **sunt** fugaces' "lives are fleeting". Not 'vita fugaces' because it means 'Avoid the runners.' Vita Fugax or Tom Cotton's Vita Brevis are really your best choices.
Answer: Ars longa, vita brevis is an ancient translation from the Greek of Hippocrates, occurring in the first lines of his Aphorismi.
The aphorism is well-known and understood in English. The best answer in my view is undoubtedly vita brevis.

Life is fleeting, “vitae est labilis”?


Does electric charge vary between observers?

Question: I understand that certain observations such a length and mass vary depending on observers in different frames of motion and gravity.  I was wondering if the electric charge changes in a similar way.  I was of the impression that this cannot be the case because of the iron-clad law of conservation of charge, yet I discovered there are formulae that seem to link charge to the speed of light.  If the speed of light slows in a gravitational field would that imply that gravity also would change charge?
Comment: If a conservation law were sufficient to imply frame invariance, momentum would be frame-invariant.
Comment: possible duplicate: https://physics.stackexchange.com/q/248688/84967
Comment: Can you explain where you saw such formulas?
Answer: Charge is Lorentz invariant, meaning it is the same in all frames of reference. This means that four current is a four vector. This is because, for example, the time-like component is charge density, $\rho =\frac{dq}{dV}$. Because length only contracts in the direction of relative motion, volume only decreases by a Lorentz factor, the same as length. If charge is a scalar the  charge density transforms as a component of a four vector. This gives Maxwell's equations their relativistic form
I can't speak with certainty but I imagine it is invariant under diffeomorphisms in general relativity too.
Answer: The core of the issue is the determination of inertial frames, where an inertial frame is defined as being a frame in which the laws of mechanics are the same. But, which laws? If it is Newtonian Mechanics then the Galilean transformation will shift from one frame in which Newtonian Mechanics works to another.
But, when electromagnetic theory is considered the Galilean transformation is wrong, it does not preserve Maxwell's equations.
The Lorenz transformation is one that does.
https://en.wikipedia.org/wiki/Lorenz_gauge_condition
But, there are many other options.
https://en.wikipedia.org/wiki/Gauge_fixing#Coulomb_gauge
The choice between them is the matter of a choice of a scalar gauge field. The Lorenz transformation is the one that also preserves the charge density.
To put a bit of context there, while a moving observer sees the equations of electromagnetic theory to be unchanged, they nevertheless see different electric and magnetic fields. In the general case of transformations that preserve the equations, the charge density - treated simply as a field of real numbers - also changes.
The Lorentz transformation is the gauge choice that preserves the speed of light. And it also preserves the charge density. This is not a coincidence, as there is, in the general case, a relation between the charge gauge (interpreted here as the charge on the electron, for example) and the speed of light.
Accelerating frames are more of a problem. You cannot preserve the electromagnetic equations in an accelerating frame. In physical terms, it is not inertial - so we should not expect the equations to be the same. This leads to interesting conundrums, paradoxes, and controversies.
If an accelerating electron radiates, does it radiate in its own frame? Since gravity is equivalent to acceleration, should not an electron held stationary on the surface of the Earth radiate - due to that acceleration?
https://en.wikipedia.org/wiki/Paradox_of_radiation_of_charged_particles_in_a_gravitational_field
Answer: I would a give widespread example, probably mentioned in Griffith. Electric charge is invariant under Lorentz transformation. Take Helium atom, for example; the electrons are moving in relativistic speed. If charge was varient then the net charge of atom would been positive (not neutral).
Comment: I did not think the electron had any classical velocity inside atomic orbitals.  Otherwise they would emit light and collapse.
Answer: You seem to have two questions here; I'll answer them both in turn.
I) Is the charge of a particle dependent on its speed?
No, it is not. The charge of a particle stays the same no matter what speed it is going at. However, the fields produced by the particle do change depending on the speed which one is moving, which are probably the source of the formulae you found. Charge doesn't change upon movement to a boosted inertial frame, but the fields the charges produce may. It will all produce the same equations of motion in the end, however. If you are familiar with the theory of tensors, one can find how to transform it quite easily using the electromagnetic field tensor, defined as
$$F^{\mu\nu}=
\begin{pmatrix}
0 & E_x/c & E_y/c & E_z/c \\
-E_x/c & 0 & B_x & -B_y \\
-E_y/c & -B_x & 0 & B_x \\
-E_z/c & B_y & -B_x & 0
\end{pmatrix}$$
To find new components of the transformed tensor, simply use $$F^{\rho\sigma}=\Lambda^\rho_{\;\mu}\Lambda^\sigma_{\;\nu}F^{\mu\nu}$$
where $\Lambda^\alpha_{\;\beta}$ is the matrix describing the Lorentz transformation you want to use.
II) Does gravity change charge?
No. Again, the fields produced by a charge may change, but the charge of a particle is absolute. The electromagnetic field transforms and evolves in an incredibly complicated and nonlinear way in general relativity (more information here), but the charge of the objects remains the same.
Comment: What is the difference between charge and electric field? I mean how can you measure charge if the electric field is distorted?
Comment: @Derek Seabrooke Charge is the property of matter that causes it to experience a force in an electromagnetic field. An electromagnetic field is the force field of electromagnetic theory; it shows how strong the force is at a location. The field is not distorted; one in reference frame may see a field as magnetic, whilst another may see it as electric, but the same motion will be predicted. In the new frame, you can measure charge however you normally would; because the same motion is predicted no matter what frame, you can still predicted the charge.
Answer: The above answers seem to nicely summarize why charge is conserved in every frame of reference. I would like to take a different approach as to why that makes sense, and why the charge conservation law holds.
1. Charge, current and conservation:
The most simplest way to state the conservation of charge is to say, $$\frac{dQ}{dt} = 0$$
That the rate of change of charge in time is $0$, implying that the quantity of charge is a constant.
But, sometimes charge can decrease in a system. This does not violate the supreme principle, but rather states that charge can 'leak' or flow through an area, causing the charge in the system to decrease, and the charge outside to increase. So, the amount of charge in the entire universe is the same, but for smaller systems the above equation may not hold true.
Consider a box with some charge inside of it. The charge can flow out through any of the faces of the box, thus decreasing the overall charge inside (it can also increase if the charges are instead entering the box). So, you need to take into account this flow of charges, called a current to make sure that the conservation law holds. The resulting mathematical form is:
$$\frac{d\rho}{dt} + \nabla . J^i = 0$$
where the $\rho$ represents the density of charge inside the box, and $J^i$ is the current vector, because current can flow through the $x$, $y$, and $z$ axes; so we use a vector to keep track of them all. What the above expression says is: the rate of change of charge in the box and the rate of change of current flowing in or out of it, is going to be conserved.
2. Four vectors, dot products and Lorentz invariance:
In Relativity, we use something known as four-vectors, which are 4 dimensional vectors. Usual vectors have only three components: one corresponding to each dimension of space; in Relativity, we consider a fourth dimension: time. So, vectors in Relativity have four components, one corresponding to time, and three to space. We denote these vectors by $$A^{\mu}, \mu = (0, 1, 2, 3)$$
where the $0$ index corresponds to the time component and the other three to the space components.
Now, let's move on to Lorentz invariance. In Special relativity, whenever we want to consider events from a different reference frame, we use something known as Lorentz transformations. I am going to leave a few nice resources in the further reading below, but for now, that is enough information.
If a certain quantity does not change when the Lorentz transformation is applies to it, we say it is Lorentz invariant.
So, some of the things that are always Lorentz invariant are the dot product between two four-vectors. Again, for length purposes, I will leave a link to some resources below, but simply put, dot products between two vectors can be denoted as: $$Product_{dot} = A^\mu B_\mu$$
The only constraint is that the index of the four vectors should be the same and they should be repeated upstairs and downstairs. Expanding this expression, we get: $$A^{\mu}B_{\mu} = -(A^0 B_0) + (A^1 B_1) + (A^2 B_2) + (A^3 B_3)$$
which is a scalar and is Lorentz invariant. These scalars are called Lorentz scalars.
3. Bringing it all together:
In Special Relativity, we denote the charge and current of a particle as a four vector $J^{\mu}$. The time component is $\rho$ and the space components are $J^i$. There is another four vector $\partial_{\mu}$ which is defined to be: $$\partial_{\mu} = \left  (\frac{\partial}{\partial t}, \frac{\partial}{\partial x}, \frac{\partial}{\partial y}, \frac{\partial}{\partial z}\right)$$
Okay. Now, particles have some properties, like mass and charge that do not change when you shift frames. Similarly for the conservation of charge, you can write it as $$\partial_{\mu}J^{\mu} = 0$$
which is a dot product, so it is naturally a Lorentz invariant.
4. So, can charge vary for observers?
I took an unconventional way of answering here, by first showing the true way of expressing the conservation of charge and then going through a long way to show why the law hold even when our frames change.
By doing this though we can mathematically say, that charge cannot vary with respect to observers. We can be sure about this, because the conservation of charge holds, whatever the situation.
Going back to the box situation, imagine that there is no current, or flowing charges at all. Then, by the proof of the fundamental upholding of the charge conservation law, we can clearly agree that the charge does not depend on observers. Rather than just stating it up, we derived that answer as a consequence of the conservation law. If you try and negate the answer, then you would get a contradiction between the above proof, one of the most fundamental laws of Nature, and your new results. If the conservation law stays put, so does the charge; it has to.
Further Reading:
One of my answers with a lot of ore stuff on four vectors, and Lorentz invariance; it also shows why mass is an invariant: Why is mass an invariant in Special Relativity?
More about four-vectors in relativity: http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/vec4.html
And a brilliant introductory series on the topic of vectors by 3Blue1Brown: https://www.youtube.com/watch?v=fNk_zzaMoSs&list=PLZHQObOWTQDPD3MizzM2xVFitgF8hE_ab
Some more on conservations: https://en.wikipedia.org/wiki/Continuity_equation#General_equation
More on Einstein summation notation: https://mathworld.wolfram.com/EinsteinSummation.html and https://en.wikipedia.org/wiki/Einstein_notation
Lorentz transformations: https://en.wikipedia.org/wiki/Lorentz_transformation and https://www.khanacademy.org/science/physics/special-relativity/lorentz-transformation/v/introduction-to-the-lorentz-transformation
Dot products: Question about dot product of four vectors? and https://www.youtube.com/watch?v=eyxC4YJ0YH0
Answer: A lot of people have already pointed out how charge is conserved locally in special relativity. Conservation of charge is just an application of Noether theorem (must have a equation of form $\partial_{\mu}J^{\mu}=0 $) so if we're giving description of a phenomenon and we don't have a continuous global symmetry then we can say goodbye to our iron-clad conservation of charge law. When we talk about conservation of electric charge we have at our disposal Maxwell equation (which describe Electromagnetism) and Minkowski or Curved background.
For Minkowski the derivation (which I like) is as follows $$\partial_{\nu}F^{\mu\nu}=J^{\mu}$$
$$\implies\partial_{\mu}J^{\mu}=0$$
because of antisymmetry property of $F^{\mu\nu}$. Now $Q$, the charge which will be conserved is $\color{red}{defined}$ as$$Q=\int d^3xJ^0$$
if you take its derivative $$\frac{dQ}{dt}=\int d^3x\frac{\partial J^0}{\partial t}$$
$$=\int d^3x\hspace{4pt} \partial_iJ^i$$
applying gauss theorem $$\oint dA_i\hspace{2pt} J^i$$
which vanishes because $J$ goes to zero at large distance and $dA_i$ is normal surface element at the boundary of $R^3$.
Main reason why I provided above derivation is because of its close parallel to the derivation in curved background. Now Maxwell equation in curved sptm is given by $$\nabla_\nu F^{\mu\nu}=J^{\mu}$$
where $\nabla$ is our covariant derivative. Here proving $\nabla_{\mu}J^{\mu}=0$ goes by different route than SR since there partial derivatives commute. We just have to use the commutator of covariant derivative along with the antisymmetric property of $F^{\mu\nu}$
$$[\nabla_\mu, \nabla_\nu]F^{\mu\nu}=R^{\mu}_{\alpha\mu\nu}F^{\alpha\nu}+R^{\nu}_{\alpha\mu\nu}F^{\mu\alpha}$$
after manipulating above equation we get $$\nabla_{\mu}\nabla_{\nu}F^{\mu\nu}=R_{\alpha\beta}F^{\alpha\beta}$$
The RHS of above equation vanishes because $R_{\mu\nu}$ is symmetric while $F^{\mu\nu}$ is antisymmetric thus giving us the desired result of $\nabla_{\mu}J^{\mu}=0$. In SR derivation we used $\int d^3x$ to define $Q$ here we use a spacelike hypersurface $\Sigma$. Now $Q$ is defined as $$\int d\Sigma_a J^{a}$$ why? because it is then a constant. Here why is it so $$\nabla_{\mu} J^{\mu}=0$$ $$\implies\oint d\Sigma_{a} J^{a}=0$$ if $J$ goes to zero at spatial infinity then two spacelike hypersurface can be chosen such that above integral becomes $\int_{\Sigma_1}d\Sigma_{a}J^a-\int_{\Sigma_2}d\Sigma_{a}J^a=0$ which by our definition is just $Q-Q=0$ thus Q is conserved and this is what we call the electric charge in GR. There is another way of writing $Q$, $$Q=\oint_S F^{\mu\nu}dS_{\mu\nu}$$ here we have used Maxwell equation followed by another stokes theorem. $S_{\mu\nu}$ is the directed two surface boundary of $\Sigma$. $Q$ is conserved because we have define it to be that way. Judging by your question I think you might have come across formulae for speed of light in a medium and how it is related to the free charge of the medium so it might be confusing you. But note the speed of light there is determined by the charge provided by the boundary so if the speed is different you can infer there is some change in the charge at the boundary but it doesn't mean charge is not conserved. A much stronger statement to say when our system is isolated is this since we know charge is conserved and we also know charge at the boundary of the medium is less or more than by conservation of charge the influx or the outflux has to be present somewhere within the system. This is the power of conservation laws.
Further comments on conservation of electric charge. When dealing with classical system conservation of charge is guaranteed because we get $$\partial_{\mu}J^{\mu}$$ in some way or the other because of Maxwell Equations we don't have into dwell into Noether theorem. When we go for QFT and use Lagrangian density formalism electric charge is conserved charge(charge which appears in Noether theorem can as well be energy, momentum something which doesn't change with time(when I picked the term time I have lost the covariance of GR where the formulation is different)) related to the global continuous symmetry of the Lagrangian, $$\mathcal{L}=-\frac{1}{4}F^2_{\mu\nu}+i\bar{\psi}\not\!{D}\psi-m\bar{\psi}\psi$$ is invariant under the transformation $$\psi\rightarrow e^{-i\alpha}\psi$$ where $\alpha$ is a constant. Associated with this symmetry is our electrical charge given by $$Q=\int d^3x J_0$$ where $$J_0=\psi^{\dagger}\psi$$ and associated current is $$J_{\mu}=\bar{\psi}\gamma_{\mu}\psi$$ There is another way to get conservation of electric charge using only Lorentz invariance and soft limit of photon.
It basically goes like following

You tack on photon on external legs of Feynman diagram and then take soft limit of photon which means its 4-momentum satisfies $E^2=|\vec{p}|^2$ and E can be made as small as possible
We then take Lorentz transformation and see how polarisation vectors transform.
Making similar argument as coming up with Ward's identity and we get the result of charge is conserved in an interaction.

Even though we have charge conservation in QED but when we do renormalization of QED it's non trivial fact that charge conservation still survives for example anomaly (symmetries which are present in classical lagrangian but when we construct quantum theory of them the
symmetry doesn't survive) to read further about how charge is conserved even after renormalization you can refer to Schwartz paragraph just below $(14.143)$.
Further reference:

Relativistic toolkit
QFT Schwartz


Solving VRPTW using OptaPlanner

Question: I have tried to run example https://github.com/droolsjbpm/optaplanner/tree/master/optaplanner-examples/src/main/java/org/optaplanner/examples/vehiclerouting
as it is written here:
 http://docs.jboss.org/optaplanner/release/6.3.0.Final/optaplanner-docs/html_single/index.html#downloadAndRunTheExamples with data set cvrptw-25customers.xml . When I changed readyTime and dueTime in some customers, it didn't result in any change in score. It looks like this program doesn't care about time windows. Should I change something in Java classes? My goal is to get time needed to drive to all customers, taking into account all time windows.
Answer: This should work, I 've done it several times myself. Potential causes:

Did you load the xml file again? Try changing the VehicleRoutingPanel code so it's obvious which customer you changed and if indeed the values changed. Compare the screenshot of before and after your change (or duplicate the xml file so you keep the original).
If some arrival times and dueTimes change, the score doesn't need to change. Try making very small time windows, at annoying times, that should definitely impact the score and make it worse.

Solving VRPTW using OptaPlanner


Ubuntu and ubuntu-10.04 tag synonyms

Question: Wanted to create a synonym there but being a version synonym it's not possible for mortals. How are the policies about versions and softwares btw?
Answer: For the big ones we seem to like a single monolithic tag for the entire product (windows) and another tag for specific versions (windows-2008-r2). Same for the Linuxes out there. It gives the lazy an easy tag, allows the pedantic to cover all the bases, and allows people Interested in tags to just add one instead of an entire constellation.
Tag synonyms are odd. You need to meet some rep-requirements in-tag before you can suggest one, or enough rep overall (like 20K or better) to just do it to anything. In-tag rep is hard to get on SF outside of the big ones like linux or networking.
If you see one that needs a synonym and you aren't able to suggest one, a meta-post is just fine to get the discussion started.
Comment: @coredump Yeah, we want to keep the 'Ubuntu' tag generic. Retaggers can add a version once it becomes clear which one the questioner is talking about.
Comment: Windows is a better tag then Vmware.  Vmware is a company name not a product line.  If there was a `Microsoft` tag, it would be equivalent to Vmware.  A large number of the questions in the Windows tag apply to almost every version of Windows released in the last decade.  If we got rid of `Windows`, we should get rid of `linux` while we are at it.
Comment: Can we have ubuntu and ubuntu-10.04 then?
Comment: @coredump We have ludid and lucid-lynx already as synonyms of 10.04. What did you want to add?
Comment: hmm. Ubuntu? But that may start to get confusing.
Comment: I don't know if this is really a good idea. Tag wildcards like `windows-server-*` are a better approach. The [windows] tag is meaningless by itself, which means it's a meta-tag. If I spent HOURS cleaning the site of [vmware] you CANNOT tell me that [windows] is a good idea.

Ubuntu and ubuntu-10.04 tag synonyms


Is it wrong for a Muslim to say hallelujah?

Question: I have searched about both the literal and religious meaning and context of the word "Hallelujah", and I learned it is a Hebrew word, meaning "praise to God".
Is it okay for a Muslim to say Hallelujah?
Comment: Alhamdolillah means almost the same and is used by [Arabic speaking Jews and Christians](http://horsehints.org/IsraelBaruchHashem.htm), in addition to Muslims.
Answer: In regards to your inquiry that asked:

Is it okay for a Muslim to say Hallelujah

So, in case even it supposedly can be halal (God knows best), but there could be a significant point to pay heed. This point is related to the promotion of Jews. Actually whenever you use such Jews phrases or even symbols of the Jews, consequently you would promote their language from an aspect (except positive meaning of the words or phrases which you are saying). Then it would be nicer to ignore using such phrases that non-Muslim use them. Then try to use Islamic phrases instead. Such as Alhamdollelah and other Islamic (Arabic) phrases.
May Allah guide us
Comment: Yes that would be appropriate to use Islamic and specificlly Arabic terms in such cases and to avoid using other terms. May Allah Guide Us All. Amen
Comment: yeah dear Ali Malik. Hence we'd better try to promote Islam in different manners even in Talking. God bless you.
Answer: I'm not a scholar (I could be wrong too). But according to my knowledge I think it's better NOT for Muslim's to use the phrase, "Hallelujah." The reason is simple, even though the meaning is considered a good/halal in Islamic context, when you simply say 'Hallelujah' it reflects a thoughts of a Jewish/Christianity view of praising God which is NOT good and our prophet always advised not to do anything what the Jews/Christians would do. In this case, I think it's better to avoid such phrases and say 'Alhamdulillah' which has 2 things together with a broad meaning (Nouman Ali Khan explains). One is the appreciation as "Praise is for Allah," and the second part is "Thanks to Allah." So you decide, which is better? Hallelujah or Alhamdulillah.. The latter is always beneficent.
Peace.
Comment: P.S. I suggest you watch Nouman Ali Khan explaining, 'Alhamdulillah'.
https://www.youtube.com/watch?v=rLB75MaHgCk
Comment: Yes i have watched it and now have more clear thinking about it. jazakAllah
Answer: Hallel a Hebrew word and also used in Arabic, since childhood when told to hallel means to say la illah illallah (God is one)  repeatedly, it's quite sad when you find a Muslim who is talking about Islam in English and speaking English with Arabic words mixed in there, confuses so many people, God is the English name for the Almighty which English speakers use, Allahis the Arabic name for the Almighty use by the Arabic speaking to Christian and Muslim every language has a different name for the Almighty.
The main objective of the Scriptures is to acknowledge the one true living God of the heavens and earth and as I mentioned earlier what hallelujah (hallel) means in Arabic, saying God is one acknowledging that he is one constantly is a way of praising God you're mighty, as I mentioned every single language has got a nine weeks for example Mary in English, Miriam in Arabic also Marie, Maria, this goes out to all the people from all different religions who try and divide and can't see that every language has only a different name for the same thing.
Answer: It means " praise to GOD" as it is not Hebrew or Arabic word. The apostles where anointed by Holy Spirit and they speak in different tongues.It is a word from heaven. Heavenly language..
Comment: Pointing some references would be good.
Answer: its haram to say hallelujah cuz it is the name of THEIR GOD and they usually use that word in church.i got this info from an ustadz. that's mean as a muslim we can't use that word to praise god/Allah or hear a song with hallelujah in the lyric its haram
Comment: name of their God? Whose God?
I'm a Catholic, and no, it's not a name of God.
It means praise the Lord.


How do I correctly install libpcre3-dev:i386?

Question: I want to install libpcre3-dev:386 onto 64-bit Ubuntu 14.04.
I have libpcre3:i386 installed, as well as the :x64 -dev version. But if I run 'sudo apt-get install libpcre3-dev:i386', apt wants to remove "all" of my build tools:
Reading package lists... Done
Building dependency tree
Reading state information... Done
...
The following extra packages will be installed:
  libc6-dev:i386 libpcrecpp0:i386 linux-libc-dev:i386
Suggested packages:
  glibc-doc:i386 manpages-dev:i386
Recommended packages:
  gcc:i386 c-compiler:i386
The following packages will be REMOVED:
  build-essential camlp4 dkms dpkg-dev g++ g++-4.7 g++-4.7-multilib g++-4.9
  g++-4.9-multilib gcc gcc-4.7 gcc-4.7-multilib gcc-4.9 gcc-4.9-multilib
  gcc-multilib hardening-includes lcov libtool lintian ocaml
  ocaml-compiler-libs ocaml-interp ocaml-nox pepperflashplugin-nonfree
  sa-compile virtualbox-dkms
The following NEW packages will be installed:
  libc6-dev:i386 libpcre3-dev:i386 libpcrecpp0:i386 linux-libc-dev:i386
0 upgraded, 4 newly installed, 26 to remove and 11 not upgraded.

Any idea what it's doing and/or how I can get it to install the 32-bit -dev library?

Disclaimer: I installed GCC 4.9 from a PPA (ppa:ubuntu-toolchain-r/test). After installing, I removed it as a repository; if I re-add it, then gcc-4.9 and its associated packages disappear from the list of things that will be removed:
The following packages will be REMOVED:
  build-essential camlp4 dkms dpkg-dev g++ g++-4.7 g++-4.7-multilib gcc
  gcc-4.7 gcc-4.7-multilib gcc-4.8 gcc-4.8-multilib gcc-multilib
  hardening-includes lcov lintian ocaml ocaml-compiler-libs ocaml-interp
  ocaml-nox pepperflashplugin-nonfree sa-compile virtualbox-dkms
The following NEW packages will be installed:
  gcc-5-base gcc-5-base:i386 libc6-dev:i386 libpcre3-dev:i386 libpcrecpp0:i386
  linux-libc-dev:i386

I see GCC 5 in that list. Is that causing the problem somehow? I'll leave it enabled for everything else here.

If I download the .deb for libpcre3-dev directly and try to install it with dpkg -i, it says:
dpkg: dependency problems prevent configuration of libpcre3-dev:i386:
 libpcre3-dev:i386 depends on libc6-dev.
 libpcre3-dev:i386 depends on libpcrecpp0 (= 1:8.31-2ubuntu2).

Earlier, I tried installing libc6-dev:i386 but it gave me the same list of packages that would be removed.
Also, now if I try to run apt-get again, it complains
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 libpcre3-dev:i386 : Depends: libc6-dev:i386 but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).

and if I try to run apt-get -f install, it gives me the same list of packages to remove.
(Incidentally, I've obviated the need for actually installing this for now, by manually unpacking the .deb file in a different location. So now advice for getting apt back into a happy state is more important, though I would still like to know what was going wrong originally.)
Comment: Possibly  something from that ppa. On 14.04 here it would install cleanly, adding 7 packages -  gcc-4.8-base:i386 libc6-dev:i386 libpcre3:i386 libpcre3-dev:i386 libpcrecpp0:i386 libstdc++6:i386 linux-libc-dev:i386, what's your current gcc-4.8-base package?
Comment: I am editing more info into the question, including PPA name. 'dpkg -s gcc-4.8-base' shows 'Architecture: amd64, Multi-Arch: same, Version: 4.8.2-19ubuntu1'. Is that what you want?
Comment: Well adding that ppa doesn't really hurt here, just adds a few - `The following extra packages will be installed:
  gcc-5-base gcc-5-base:i386 libc6-dev:i386 libpcre3:i386 libpcrecpp0:i386
  libstdc++6 libstdc++6:i386 linux-libc-dev:i386  The following packages will be upgraded:
  libstdc++6`
Did you happen to use trusty -proposed before then disable? (it's not enabled now.
Answer: See this StackOverflow post. It's trying to purge your package (and dependencies) and redownload it all back. Instead, try running sudo apt-get install --reinstall libc6-dev-i386
Comment: I tried running that. It did seem to do something ("Preparing to unpack...", "Unpacking...", "Setting up...") but it didn't do anything to help the main problem.
Comment: What makes you think that the issues are related?


EXM Open rate is not updated right away

Question: I am working in EXM, I have created an Automated Email campaign and sent mail by using the form action. After opening the mail, I checked the EXM dashboard, but it still shows an open rate as 0.so is there any way to update the open rate immediately?
Answer: There could be many reasons for the open or click rate not updating on the EXM dashboard.
But before checking the logs and config settings, make sure you've checked the below points:

Check if you've configured the default settings correctly, mainly the base URL parameter. This URL should be correct and should be reachable from the machine you're opening the emails. Check this link https://doc.sitecore.com/developers/exm/90/email-experience-manager/en/edit-the-exm-default-settings.html

Go to Email root in the content editor (/Sitecore/content/Email) and look for this field Track Message Open and confirm this should be checked.

EXM sends an IMG pixel with each email, which is responsible for tracking the opening of an email. This img tag is present at the end of the email (if you see the HTML source code of the email), something like this:
<img height=3D"1" width=3D"1" border=3D"0" style=3D"border-color: transparent;" src=3D"https://somedomain.com/sitecore%20modules/Web/EXM/RegisterEmailOpened.ashx?ec_eq=3DkRYrGM5CERgrLsiuJXSZKP0aZchMDm7E4MnZLnTXwPKnAKAb3iNP4gBPbUUkKsfBlNdK4SmTkm2hfAs2bbg23aVWCUHaAVhZa41n%2bXlJ6E96JHQtOmewSJr4Oja0Ph0aDrnNLc34pDduPIStgMtgjoOuLX%2fvkqS4ixd95eXk%2b7UTkFKsWodkftuZaaCBfy84zVEI%2fQdmWp%2faKOAxGjCLSg%3d%3d" alt=3D"" />

So, make sure this tag loads correctly. Take the src URL and check if this URL is reachable.

EXM Open rate is not updated right away


How best to request a particular question/topic to be revisited/addressed according to latest circumstances?

Question: Sometimes there is a question of interest to me that was last active, say in 2010, and there's a desire to check if new possibilities have surfaced in 2011. I don't think a new question (How to do XXX, but in 2011) is warranted, but is there a better way than asking in the relevant chatrooms? (as the reach may not be ideal)
Comment: did you consider editing question or raising a bounty?
Comment: I am not sure if editing the question would be a good idea since it may affect the interpretation of the existing answers. Bounty is a  general solution to get more responses but I don't feel it is the best way.
Comment: well _if editing the question may affect the interpretation of the existing answers_ that makes a strong sign of a new question to me... Hm at the risk of getting close as dupe I'd rather open that new question (with the reference to old one of course)
Answer: You could start a bounty with the reason "Current answers are outdated". This will place the question in the Featured section and hopefully draw some new answers to it.
Comment: The only problem with this is that I have no idea if current answers are outdated or not, although I would like someone to vet them and update if necessary, which is the whole point of my question.
Answer: What makes you think there are new possibilities? The answers are not enough in your opinion? Then you should, in my opinion, edit question to notice that this answers do not fully answer the problem stated in question, even if there is accepted answer.
However, if you have similar, but not the same problem, or some changes in technologies have occured, than, I think, you should ask new question linked to previous.
A real-life example in web technologies: a new version of browsers have been made (IE 9, FF 9 etc.) so you ask a question about how they work with some solution, noting that some question was made when the last version of IE was 8 etc.
I've asked something similar: I want to feature an old question without a good answer, the answers provided me valuable hints about what is seen positive by SE users.
Comment: Technology changes every year (could be more or less frequent depending on topic), so I may want to know if subject experts have updated content (I don't know, but they may) for a certain question
Comment: Maybe a question like 'is there other way to do X as the way Y described in topic Z?'


When installing a three way dimmer switch, does it matter which switch is the dimmer?

Question: My grandmother called me the other day to troubleshoot from half way accross the country. She installed a three way dimmer switch in her dinning room at the location most used. It turns the light on and off, but does not dim. It is an incandescent fixture and it has incandescent candelabra lamps. Even as a wireman I have been racking my brain to figure out what else it could be. After reading some other Q&As, I noticed some people suggested that a dimmer should be on the line side, doesn't the power need to go through both switches? And, therefore, shouldn't it dim regardless? I suggested she try to find dimmable bulbs as the first, easiest, and cheapest attempt to solve the issue. If it does matter which side the dimmer is on, would it help at all to have a dimmer on each end?
TIA
Comment: Does she have a lifetime cache of incandescent bulbs squirreled away somewhere? Or will be swiching to advanced tech lamps at some point in the future? Those are the options available, there is no third.  The dimmer choice needs to account for that, or it will need to be replaced eventually.   Modern dimmers often need neutral, which may be the issue.
Comment: Is it possible that she has a smart switch with some brains in it as the other 3 way switch? My other guess is if you add a dimmer to the lights on a ceiling fan, sometimes ceiling fans have their own dimming controllers installed to work with a remote control and that would make the same symptoms.
Comment: My 2 cents: if the dimmer turns on/off but doesn't dim, either the load is non-dimmable or it's a bad dimmer.
Comment: Can you have her send you photos of the insides of the light boxes?
Answer: I know it sounds pretentious, but it really does depend on what dimmer or set of dimmers or dimmer kit you buy. If you're a wireman you can probably go online to a manufacturer like Lutron and look up a set of specification sheets to help you select a proper dimmer.
Answer: Replacing a 3-way switch with a dimmer should be an easy project.  It doesn't matter which switch gets replaced as long as the three wires are hooked up correctly.  If it's wired incorrectly, the lights will not turn on and off as expected (maybe only one switch will work, maybe nothing will work).
So, turn the dimmer up all the way, and turn each switch on an off.  Do the lights turn on and off as expected?  If that works, but the lights do not dim, it's either because the bulbs/light fixture are not dimmable, not compatible with the dimmer you selected, or in rare cases, the new dimmer could be bad.
If the light bulbs are not just plain incandescent bulbs, I'd bet they are not dimmable.  Right now, dimmable LED and CF bulbs are common, but in the past they were hard to find or unavailable.
Comment: If you are installing a smart/home-automation dimmer, these are odd beasts and each manufacturer has their own constraints and quirks. There are ways to set them up as three-way, but some require another smart switch at the far end, some require the dimmer be the switch at the beginning of the branch circuit, and gods only know what else. Download and read installation manuals before sinking money into these; they're great once set up but setup is not usually a direct replacement.
Answer: The problem could be an older wired home with incorrect neutral switching. She needs a professional electrician to troubleshoot the problem and not some handyman and make the necessary corrections. A good electrician will have the problem diagnosed the first ten minutes he is there.


Adding Version number as well as Document ID Value to a Sharepoint Online Word document

Question: I've read many articles on this now but it seems the the {version} tag it's no longer possible to add the {version} tag as an option in a content type information management policy in the  label format field in sharepoint online. In addition, it looks like the label field is no longer shown as an option in Word Quick Parts any more (unlike the document id value). Anyone know how I can do this please?
Answer: Per my test, I can create a {Version} label in Information Management Policy settings in SharePoint Online library.

And I can also insert the label in Word after open document from SharePoint Online library.
Comment: That's really strange as I dont get those options.  Where are you creating those policies please?
Comment: I create a policy via library settings->Information management policy settings->click the relevant content type->tick the enable label option.
Comment: Ah I did try that but I get a message stating "You cannot change policy settings for this content type because it inherited the settings from its parent content type or a site level content type. To change these policy settings, change the settings for the parent of this content type. " so I went back to the root site and tried tghe same there under Web Designer Galleries > Site Content Types and selected Document there and that's where I get the "The label reference, Version, could not be found." message when I put "{Version}" in the Label Format box.


What is this articulation mark that looks like a short upside-down slur?

Question: From Jamey Aebersold's "Cantaloupe Island," Maiden Voyage, vol. 54.
Answer: This is called a bend!
It (normally) means exactly what it sounds and looks like: you start on the pitch, bend it down, and then return to the original pitch. More rarely, composers will notate bends to also mean you scoop up into the pitch.
Bends are really reserved for brass and woodwind players, so the fact that this is in a piano score suggests that it's probably an arrangement of a chart played by brass/wind players.
Edit: After hearing the example here, two things become clear:

The notation here is for the latter intention mentioned above, where one is to scoop up into the note.
It's played by piano, so the notation actually creates a bit of a grace-note E♭ that scoops up and resolves to F.
Comment: Bending can be done on the piano as well, if you have a hydraulic press....
Comment: After hearing the actual recording, I've edited my answer.
Comment: @ScottWallace You don't even need a hydraulic press. Just get a woodwind, climb onto a piano, and play that as notated. Bam, bending on a piano.
Comment: Or it could be a synthesizer part?
Comment: Well, you could try, sort of, to imitate a bend by moving from the Eb to the F while holding the C
Comment: @NicHartley - woodwind players can warp anything.
Answer: This example is from a c.1991 Hancock arrangement for a treble clef solo workbook. The articulation is indeed traditionally called a bend and does not appear in other charts of this standard tune.  I've never seen it on a piano part but I would perform it as a kind of reverse mordant on the top note F. The middle finger bounces on the Eb while the fourth finger sustains the F, etc.
If playing right-hand synth, you may also bend by briefly flicking the pitch bender down during the note, having set the synth to top-note-only pitch bend mode.
I don't know about brass but on sax the bend can be done by slightly dropping the tongue and jaw quickly during the note.
Comment: My first DX7IIFD had that feature!  It's really nice to have when using the sustain pedal a lot.
Comment: I didn't know that you could set a synth to "top-note-only pitch bend mode." Good to know!
Comment: **Thank you!** to everyone who responded.  This makes a lot more sense now, especially with the preceding grace note.


Does monism imply that computers can have consciousness?

Question: According to The Basic Theory of the Mind, the mind is not a different entity from the brain, but an emergent property of the brain.  Based on this assertion, can it be concluded that computers and any other information processors have or can have consciousness and mind?
Comment: You may also like these questions: [When can we say that machines are conscious?](https://psychology.stackexchange.com/q/10551/7001), [Can a sufficiently complex ANN simulate consciousness?](https://psychology.stackexchange.com/q/15667/7001), and [How can machine possibly possess consciousness if computation is a human idea?](https://psychology.stackexchange.com/q/5275/7001).
Comment: That might be better. I think of them as sort of separate ways of looking at the problem but it's possible someone has argued for or against connecting them. As a scientist I'm more interested in the empirical evidence than the philosophy, though.
Comment: It doesn't seem like this "basic theory of the mind" is anything more than Chirapat Ukachoke's book, who is not someone I am familiar with publishing in (academic) consciousness research. Not that it makes it invalid, there are just way more involved researchers who have published theories in this area, both from perspectives of philosophy and psychology/neuroscience, and I don't see much evidence that this book is influential at all. It's very unlikely that anyone here is aware of or has read this book.
Comment: I'd also add that the idea that the mind is an emergent property of the brain is not at all unique to this theory.
Comment: @Bryan, thank you for your comment. So, if the question is rephrased to involve monism rather than the basic theory of mind, then can computationalism be implied? Arnon has mentioned that there are still debates on this but I can't see any doughtful stage in monism to computationalism conversion: If mind is just a property of the brain, and if brain is only a computer, then mind can be emerged from a computer, one example of such a computer being the human's brain. I think they are exactly equivalent to each other, but I need to know what scientists think; I am only 18 afterall.
Comment: True, thanks for your comment.
Answer: Note: While "The Basic Theory of the Mind" may potentially be well researched and possibly accurate, it is (as far as I know) a self-published discourse by a non-researcher, that is not peer-reviewed.  As such, I will not address it specifically.
Monism, the view that the brain and mind are one entity, is often associated with a family of philosophy of mind viewpoints called functionalism - the idea that mental states are defined solely by their functional role.  A related approach is computationalism - the idea that mental states are defined by their information processing function.
Thus, computationalism's answer to the hard problem of consciousness (the question of how the brain gives rise to the mind under monism), is that the mind is an emergent phenomenon due to information processing in the brain.  A well-known theory that supports this particular view with evidence is Integrated Information Theory (IIT).  While this is a popular view, it is not the only one, and hence it is not fair to say that monism implies computationalism.
A list of monistic alternatives to computationalism can be found on Wikipedia.  A couple of interesting examples:
Physicalism: The physical properties of the brain also matter (ie, not just its information processing properties).  This implies that a brain made of silicon, performing the exact same information processing as a brain made of carbon, may not share the same conscious experience, because they are physically different.
Eliminative materialism: Conscious experience does not exist.  That is, people's common-sense understanding of the mind is incorrect, and the mind is essentially reducible to the biological properties of the brain.
Wikipedia also mentions functionalism, behaviourism, type physicalism, and emergentism.  Other alternatives worth mentioning:
Representationalism: The mind is an internal representation of the brain - ie, not a physical phenomenon, but an interpretation of physical phenomena.
Philosophical zombies: The conceivability of a zombie, physically indistinguishable from a human being, but having no conscious experience (no mind), suggests that computationalism is incorrect.
Idealism: We are making a mistake trying to determine how the mind arises from the brain, because it is the other way around - the mind is the fundamental reality from which all else arises.
Cognitive Closure: We simply lack the intellectual capacity to understand the brain-mind relationship.
Comment: Thanks for this great answer. So computationalism is supported by only some of the monistic theories, and not all.
Comment: [The bibliography of the author](https://mindtheory.net/contact/ "Contact - The Basic Theory of the Mind") says that he is a neurologist


Path format for intermediate data while sharing models

Question: I didn't fully understand using relative paths in models yet. I have already asked a question on this topic (EDIT3 - summary: I always check "Store relative path names", but when I move the model, this often/ always uncheck and I don't know why), and now I'm trying a more concrete approach. In this help page sharing whole directories was suggested. Now I try to do this - I have created similar directory structure and set scratch workspace (in ArcToolbox - Environments, not per model).
Now I face a problem: what path should the intermediate data have? When I left it blank, the result was ERROR 000735 for tools using the intermediate data as input or output, regardless of whether the data were managed or not.
Another way suggested here was to use %scratchworkspace% variable substitute. Now the errors are not so uniform, but none of my models work.  Most errors were caused by a typo in scratch workspace variable (thanks to @danb for finding this). Still, errors some other models (in functions converting shp to raster) last : ERROR 999999: Error executing function. Can't save to disk (check for space, write permission, or name).
Again, being managed or not means no difference.
One of the models previously failing due to the miss-spelled variable now works when the scratch workspace is a folder but not when it is a geodatabase. The error message is as follows:
ERROR 000875: Output raster: d:\Fav\APA\Lidar\ArcheoLidar\Scratch.gdb\FilterRaster's workspace is an invalid output workspace.
ERROR 000581: Invalid parameters.
Failed to execute (Focal Statistics).

I'm almost sure that the scratch workspace can't be blocked by anything. There could be problems with folder/geodatabase scratch workspace, but I tried both options and the errors are the same.
So how to share my model in the "ZIP and share well-organized system folder" manner? There must be some solution/ workaround for these problems.
Comment: Did you copy paste that error message from the tool? if so, your scratch workspace variable is not spelt correctly. **%scratchworkspace%**
Comment: ..Remove the **.tif** from your output name. No extension is required when saving to a geodatabase.
Comment: @danb: while using .gdb as the scratch workspace, the same error is returned with and without the extension. While using a folder as scratch workspace, it works both with and without the extension.
Answer: i see the problem.
Unable to create the output raster: d:\Fav\APA\Lidar\ArcheoLidar\Data.gdb\rt03_idw1.tif
you cannot create a tif in a .gdb just remove the .tif
and yes use %scratchworkspace%
Answer: Firstly did you set the option for relative paths?
 "If you want all your new maps to be stored with relative paths you will need to specify relative paths as the default. Click Customize > ArcMap Options to open the ArcMap Options dialog box, then click the General tab. Check the option to Make relative paths the default for new map documents. This setting is stored in the registry".
If so you should be able do zip your data directory and your gdb and mxd and have everything work correctly unless i'm missing something about your setup or intention.


Can I make baccala (Italian salted cod) at home relatively easily?

Question: I would like to make some Italian baccalà dishes. However, I am unable to get my hands on baccalà. Also I have a box of frozen cod fillets sitting in the freezer that I don't want to waste. Can I make baccalà at home? Any easy way to do so? All I can find on Google with "baccala" are recipes that call for baccala, not how to make this important ingredient.
Comment: There are many recipes on the internet to make your own salted cod; have you look at them ?
Comment: Italian baccala and Spanish baccala are often made from cod that's been imported from colder waters (like Ireland, Norway or Finland).  So you should search for one of those countries for how to actually salt the cod : https://cod.fromnorway.com/norwegian-cod/salted-cod/
Comment: @Max Maybe I wasn't thorough enough? My searches all included the keyword "baccala". I went five pages without seeing one Google hit about making baccala. Almost every hit was about _using_ it. I wanted to find how to make baccala specifically, because I needed it for Italian recipes. I wasn't sure if regular salted cod was made the same way because, well, I didn't know how to make baccala.
Comment: I googled "dry your own cod"
Comment: @Max Darn it. I should have known people salt their cod the same anywhere in the world. :P Seriously though, I honestly and reasonably thought there would be differences in making salted cod. Japanese, Korean, Greek salted fish roes are all made quite differently. Not to mention cured meats or cheeses around the world. So it wouldn't be a stretch to believe baccala was unique in its own right, would it?
Answer: Yes, you can.  Instructions from the book The Cuisines of Spain:

Get several cod filets, preferably skin-on
Cover the bottom of a large non-reactive pan or dish with coarse salt (such as kosher salt)
Put the filets side-by-side on the salt.
Cover them with coarse salt.  They should be completely covered, with no fish showing.
Place the pan, uncovered, in the refrigerator for 48 hours.
Every 12 hours, pour off any accumulated liquids.  This will wash away some of the salt, so add salt as needed to re-cover the fish.
Lift the fish out of the salt and wipe it down with damp towels to remove the outer salt.
Use or freeze within a couple of weeks.


Asking for extension in submission of revision

Question: I submitted a paper to one of Elsevier journals. It got major revision and the submission time given to me was two months. Now the time is very near (10 days) and I think I cannot complete all changes to be incorporated. I asked for extension in due date of submission through editorial system using my login. Even after 4 days, there is no response. I am confused what should I do?
Is the deadline really hard and if I submit after a week or so, it will be rejected?
Comment: In general, these deadlines are to keep things in a timely and organised manner. It shouldn't be a problem getting an extension. I would send a polite reminder on the date of the deadline.
Answer: Counting the days, you asked for an extension on 24.12. Not everyone has to be around during the holidays so next time ask maybe a little sooner.
It may depend on the field and journal, but this summer I asked for an extension and I got it. Also considering how certain deadlines are handled around the academia (like 3 months taking the referee to review a revision of the paper just to say its OK), you are probably going to be just fine.
Edit: I just remembered that some time before Christmas I was sent a proof to answer the questions from Journal of Mathematical Physics with a deadline of 48 hours. I guess it took maybe even more than 3 days to send it back and nobody did complain.
Comment: If you are sure you sent the message correctly, then probably you do not need to do it again (it may even cause some confusion on the side of the journal). Maybe as pointed out in the comment bellow your question just let them know on the date of the deadline.
If you want to ask for extension for another paper then it is probably best to do it as soon as possible.
Comment: Do you think I should wait before again asking for extension?