Undefined terms

Question: How do we introduce the use of undefined terms and why are we allowed to do so? What is the difference between setting the rules of usage/manipulation and actually giving a definition?
Comment: In a "formal" setting, *undefined* terms are introduced through axioms: the axioms are the "rules of use" of primitive terms.
Comment: In an "informal" setting (a philosophical treatise) *undefined* terms are "elucidated" through discussion and comments.
Comment: Every *defined* term must be defined by way of previous introduced terms. Thus, we have to start necessarily with some undefined ones.
Answer:
"How do we introduce the use of undefined terms?"

In a formal context (such as logical foundations of mathematics) this can be done with implicit definitions. The locution "implicit definition" refers to the idea that a term is not defined by an equivalent relation, but used in axioms, and that the axioms somehow "define" the meaning of the term. So for example, "bachelors are unmarried men" would be an explicit definition because it's an equivalence relation, whereas "number" in Peano's axiomatisation of arithmetics is never explicitly defined, but used in the axioms, and a number is taken to be something that satisfies the axioms of arithmetics.
The idea can be extended from formal languages to the terms of scientific theories. Notably, force and mass in Newtonian physics can only be defined on the basis of one another, so that some authors view the axioms of the theory as implicit definition of its terms.
It can also be extended to natural languages, and some, such as Wittgenstein, went as far as claiming (roughly) that meaning is use. But even without emphasis on usage, some people think of meaning in terms of direct reference to natural properties or kinds, and in this context, no explicit definition can be given a priori, because the term acquires meaning by direct ostentation (for example, a tiger is "this kind of animal" (while pointing at a tiger)).

"What is the difference between setting the rules of usage/manipulation and actually giving a definition?"

One formal difference is this: in the case of explicit definition, the term can be replaced by its definition in every occurrence without any change in meaning (think of bachelor and unmarried man), whereas this is not possible with implicit definitions.
In the context of philosophy of science, this plays a role for realists who want to argue that a term such as "mass" or "species" still refer to the same properties even when theories change (this is combined with the idea of meaning as direct reference mentioned above). One can argue that the aim of theorising is to find essential characteristics of real properties, which will take the form of revisable implicit definitions, and that a certain continuity in theories is good enough to claim that we're still "taking about the same properties". This would be more difficult to maintain if all terms were explicitly defined.
More generally, if there's no explicit definition, operationalist epistemologies (the idea that the content of scientific theories strictly reduce to operations and observations) are difficult to sustain.
So the consequences are quite important.

"why are we allowed to do so?"

In a formal context, the rationale for this is that explicit definition of a term must use more basic terms--but how shall we define the most basic terms? Implicit definitions make it possible. This is why we are "allowed to do so": because there's no other option! This is clear in the case of numbers.
The same reasoning can probably be extended to scientific contexts, where we need "fundamental properties" to start with.
In natural languages, one rationale for this is that dictionary definitions are always a posteriori: they attempt to make explicit how words are used, but usage comes first. Quine observed this, and claimed that explicit definitions can only be given in very particular cases (when a new technical term is introduced explicitly), but that most dictionary definitions are more like attempts to capture usage.
Another possible rationale could refer to all arguments in favour of direct reference, such as the fact that all we think we know about a term (that gold is yellow...) is in principle revisable by experience. Those arguments were put forth by Kripke. Arguably, if they are valid, then no explicit definition can be given to a term, or at least, not a priori.
Comment: So realist epistemologies "would be more difficult to maintain if all terms were explicitly defined", but "if there's no explicit definition... operationalist epistemologies are difficult to sustain". Damned if you do and damned if you don't? I do not think defining *everything* explicitly is even an option (in terms of what?), and since operationalist descriptions are essentially "implicit definitions" why would there be any difficulty? If there was it would seem that non-operationalist epistemologies would be equally difficult to sustain since they can not get by without those either.
Comment: Well the project to define everything in terms of sense data has been entertained for a while. And operationalism was initially introduced by Bridgman in terms of explicit definitions: equivalence between theoretical terms and manipulation/observations.

Undefined terms


In computer science how is using passive voice regarded?

Question: A soft question, when I was in high school and in University I took scientific writing classes and people told me I should use passive voice as much as possible to sound objective, but when I entered grad school people told me I should not use passive voice unless I work in Chemistry. So Which one should I follow?
Comment: I'd recommend you read papers in conferences and journals in your field, and do what the top researchers and authors do.
Comment: Adding to @Patrick87's advice, make sure to observe 1) which authors are native speakers, 2) who are "natives" to your discipline and 3) whose prose is actually digestible. Unfortunately, wide-spread practice (e.g. if a subcommunity mostly hails from, say, Germany or France) does not always mean the choice makes sense.
Answer: The bottom line advice is: Use whichever voice best aids understanding.
Many people over-use the passive voice, thinking that it makes them sound more scientific.  In practice, it's more common for the passive voice to make sentences harder to follow.
Therefore, as a rough guideline, it's helpful to use the following principle: use the active voice whereever possible.  If you find yourself writing in passive voice, check whether your sentence would be clearer, simpler, or easier to understand if written in the active voice.
I recommend you read style guides on clear writing.  You'll find they tend to warn against over-use of passive voice: active voice often makes sentences simpler, more direct, more forceful, more vivid, and thus both more concise and more memorable.  Strunk & White have some good examples of this guideline; see, e.g., Rule 11 and Rule 12.
There are some special cases where there are conventions or norms within the field that are worth following.  See, e.g.,

Use of "I", "we" and the passive voice in a scientific thesis
Is it recommended to use "we" in research papers?.
Comment: Sentences in the passive voice are often ambiguous because they can omit the agent and causality. That makes the entire article difficult to follow.
Answer: There is some discussion of passive voice in CS papers in this comprehensive but no-so-well publicized "insider" reference (which apparently hasn't been officially published even by the authors except recorded electronically as class notes) by a leading authority in the field Knuth & teaching cohorts. Generally both passive and nonpassive ("active" or "imperative") forms of writing are used in CS with some major examples of each. They discuss use of style analysis programs which also automatically score the passive versus imperative sentence constructions, and can be used for guidance, different uses in the abstract versus the body, and so on. Overall, it comes down to style preferences and guidelines. Overuse of either form is generally to be avoided.
Mathematical writing by Donald E. Knuth, Tracy Larrabee, and Paul M. Roberts.
See page 110, and also search for "passive" and "imperative" keywords in the document.

Paul now moved on to the final area of discussion: Style.
  Rule #6 in § 1 suggests that we use 'we' to avoid passive voice. This use of 'we' is equivalent
  to "the reader and 1" . Paul says that even better is to avoid both passive voice and the
  use of 'we' through judicial use of imperative and indicative moods along with an outlying
  kind of non-sentential phrase.


How to check if a normal user has super user privileges

Question: I want to check if a normal user has super user privileges(means root privileges). My OS is RHEL 6 and i checked /etc/passwd configuration file, but no use. Please tell me any method to find the current privileges of users in the Linux Machine.
Answer: In the past root model in Unix world was easy. uid 0, you are root and you have full power to everything. Things have changed a bit, though.
suid bit
Files can be granted with suid bit so they can be run as root even by ordinary users. OK, this might have been in the original Unix. :-)
groups
If a user belongs to group 0, he might not have full root privileges but still might see lots of stuff not meant to see. Also in some distributions wheel group is something to keep your eye on - users belonging to that group can su their way to root if they know the root password.
sudo
In addition to traditional su, the sudo command allows one to restrict certain users/groups to perform only some commands as root. Check that out with visudo.
ssh access
With ssh it's possible to generate an ssh key with which you can connect as root, but only use commands x, y and z. This is generally used in tasks like backup, where the backup process must have access to every file in system.
capabilities
Linux kernel has gained capabilities which can grant access to certain subsystems such as network interfaces or block devices. See this list.
SELinux roles
If security framework SELinux is enabled in your system, also SELinux has role-based access. See Fedora's guide about SELinux.
Answer: Superuser privileges are given by being UID (userid) 0. grep for the user from the /etc/password file. The first numeric field after the user is the UID and the second is the GID (groupid). If the user is not UID 0, they do not have root privileges. This does not cover extra permissions they may have by being in an appropriate group (wheel, nobody, etc), but those are not superuser. If you are still uncertain as to what this user can and cannot do, simply su to that user (su - username) and see what you can do. Can you touch a file in a directory you do not own? If not, you are not superuser.  I hope this helped.
ex: nobody:x:99:45:Nobody:/:/sbin/nologin
Nobody is the username, 99 is the uid, 45 is the gid.
Answer: A user can gain indirect "superuser" rights by giving the right through a program called sudo.
With sudo you can specify which user or which group can execute certain programs with superuser privileges.
Answer: A user usually has no super user privileges.
But there are 3 ways that came to my mind that a normal user (i.e. UID != 0) can get root privilieges.

He executes something with s-bit from root. You can find that by searching your whole filesystem for such files (use find).
He changes userid (su command) - but that can every user do, as long as he knows the root password (so give none your root password to prohibit it).
sudo. Just check /etc/sudoers which users are allowed to executed what with root permissions.


MySQL - Add index to low cardinality text column?

Question: I'm working on project where an enum column is being converted into a text column (I cannot change this). The cardinality of the column is low (7 unique values). Would I gain a performance increase by adding a 10-15 char index, or is the cardinality low enough where the index would result in diminishing returns?
Comment: If the column names truly contain significant revealing information, just sanitise them and you can give Rolando the info he requested *in order to give you free help*, without ruining your business model.
Comment: Please run `SHOW CREATE TABLE tablename\G` on that table and post it in the question.
Comment: Unfortunately I cannot as the design is proprietary.
Comment: Uhhh it's not so much the data contained therein, it's the schema, hence the 'design'.
Comment: @MikePurcell, Actually the answer depends on whether you are optimizing for writes or optimizing for reads.
Answer: The size or datatype of the column is irrelevant. It is the unique values that matter. If you only have 7 unique values that means 14.286% of the rows have to be considered.
Instead of giving the MySQL Query Optimizer the stress of figuring out that out, you should partitioning the table by hash:
CREATE TABLE mytable
(
    id INT NOT NULL AUTO_INCREMENT,
    ...
    ...
    myenum INT NOT NULL,
    PRIMARY KEY (id)
)
PARTITION BY HASH( myenum )
PARTITIONS 7;

No need to have the myenum in any indexes. Leave it to the MySQL Query Optimizer to search the correct partition should any SELECT query have a WHERE clause that includes AND myenum = ....
If you ever have to increase the number of unique values, you will have to increase the number of partitions.
Give it a Try !!!
UPDATE 2013-10-24 17:57
As I said in the comments, you should partition by the enum with the highest cardinality.
What about the other enums? DO NOT INDEX THE ENUM BY THEMSELVES !!!
If your SELECT queries include WHERE enum2... AND enum3=...`` AND enum4=...`, you should think about making compound indexes of enums.
For example, if you have enum2, enum3, and enum4, you could make compound indexes like these:
ALTER TABLE mytable ADD INDEX (enum2,enum3,enum4);
ALTER TABLE mytable ADD INDEX (enum3,enum4);

Which order should you choose?

CARDINALITY(enum2) > CARDINALITY(enum3)
CARDINALITY(enum3) > CARDINALITY(enum4)

CAVEAT : Again, I like to emphasize, if you partition by enum1, there is no need to index on enum1.
Comment: Interesting, didn't even consider a partition. So a partition like this would be faster than adding an index? What if there were multiple enum cols?
Comment: If you have multiple enum columns, you should partition by the enum column that has the `highest` cardinality. That produces the smallest possible table within each partition.
Comment: This would be better than indexing a low cardinality column. Given such an index, the MySQL Query Optimizer may never want to use it.
Comment: Interesting. Thanks for the insight. I'll post back with a status update.
Comment: I ended up fixing the lower layer code to accept enums, but convert to varchars, so now I can add indices. Thanks again, as I learned something new.
Answer: I could hardly disagree any more than I already do with the accepted answer, for two reasons.
First, all the talk about the optimizer not using low cardinality indexes is overblown.  Its true that the optimizer may not prefer it, and it's true that the optimizer may sometimes choose to disregard it, but I have seen posts suggesting that if more than "x" percent of the rows match an index, it wont be used.  And that's absolutely not true.
I'm sitting in front of a table with over a million rows in it.  It has an indexed enum column, along with a number of other indexes, but I'm showing that index below.  Note the cardinality is 2.
mysql> show indexes in xxxxxxx;
+---------+------------+---------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table   | Non_unique | Key_name            | Seq_in_index | Column_name         | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------+------------+---------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| xxxxxxx |          1 | target_xxx          |            1 | target_xxx          | A         |           2 |     NULL | NULL   |      | BTREE      |         |               |
+---------+------------+---------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

So, does the optimizer use this index?
mysql> explain select * from xxxxxxx where target_xxx = 'default';
+----+-------------+---------+------+---------------+------------+---------+-------+---------+-----------------------+
| id | select_type | table   | type | possible_keys | key        | key_len | ref   | rows    | Extra                 |
+----+-------------+---------+------+---------------+------------+---------+-------+---------+-----------------------+
|  1 | SIMPLE      | xxxxxxx | ref  | target_xxx    | target_xxx | 1       | const | 1269015 | Using index condition |
+----+-------------+---------+------+---------------+------------+---------+-------+---------+-----------------------+
1 row in set (0.23 sec)

Yes, it does.  It uses the index for rows that match, and it also uses the index to almost immediately tell me that no rows match if I used a value in the where clause that is not found anywhere in the table in that column.
The myth of low cardinality indexes not being useful or used... seriously needs to be discarded.
Give the optimizer choices.  That isn't something you want to avoid.
Second, if you partition the table as discussed, then every query that does not reference that column in its where clause now has all 7 partitions to deal with (and 7 sets of indexes).  Unless there is something really significant and meaningful about this column that means you'll be interrogating it in most of your where clauses, partitioning on it doesn't seem like a particularly good plan.
Partitioning is not a magic bullet.
It is, however, a bullet of a different kind -- and it tends to point toward your foot unless appropriately used.
Comment: Nice. Appreciate the write-up. I actually ended up converting the enums to varchars, then added the indices. Took some refactoring on the lower level api, but seems to work well.
Comment: Seems like a pretty misleading example.  How often do people query against a multi million row table where the desired result is half the table?  Add another more typical query with higher cardinality and does the optimizer choose to use that index?  Your answer implies that indexes have no cost, when in fact they eat up space which is detrimental to the effectiveness of result set caching.
Comment: @gview There is no intention to imply that indexes are somehow without cost.  Indexes, of course, require space to exist and resources to maintain.  The example is an attempt to dispel the pervasive myth that low cardinality indexes in MySQL are not worth their cost because the optimizer won't use them... and for exactly that reason, it is a deliberately extreme example, with an index "less useful" than OP's question contemplates.  Yes, indexes consume space in the InnoDB buffer pool, but that memory is not shared with the query cache, which is the only place MySQL caches actual result sets.
Comment: I probably should have written "innodb block cache" rather than result set cache, but the idea is the same.   The smaller the dataset, and less indexes involved the faster the db performs.  This is why people avoid low cardinality indexes -- because they eat up valuable storage and are frequently not used.  I don't disagree with the gist of your post, but it could easily be interpreted to mean "create low cardinality indexes -- just in case".


Is reputation earned when the reputation limit expires?

Question: Last night I reached the limit of 200 reputation points per day, that means I have to wait 24 hours (or something) to keep gaining reputation, but it turns out that before the 24 hours, someone votes one of my posts, this clearly does not generate reputation , however I would like to know, if when the 24 hours are fulfilled, those points of the votes in my posts will be awarded to me or will they simply be lost?
Comment: They are simply lost, as far as I know. Never been there myself, but the limit would need nothing if it were only delaying the votes.
Comment: @FélixGagnon-Grenier you should try it. It's awesome :)
Comment: I'd be set for quite a while if that were the case
Answer: Reputation points above 200 on a given day are lost (except for points gained from accepted answers). Those points will not be retroactively applied in the next 24 hour period. When that clock resets at UTC 0:00, you'll start gaining reputation again, but only with new upvotes.
Answer: You don't get them.
The rep cap is per UTC day. So, when the next UTC day starts after you hit the cap, you'll start gaining rep from upvotes and such again. But the previous votes are not held in a pool- That would defeat the purpose of the cap.
Any rep you gain from the non-exempt methods is just 0 until the next UTC day.
If something happens down the road, such as a post deletion, to recalculate your rep, then the rep you gained for that day may change, and the votes that counted for that day may change. Short of that, however, nothing will make those votes count for rep.
Answer: You don't receive delayed rep. Upvotes received when you're rep-capped just don't give you rep.
Answer: Those reputation points are essentially lost.
I find it useful to keep 'Epic' or 'Legendary' badges as 'next badge' on your Activity page, because if you click on them, you can see how many points you can still earn this day by simple upvotes. If you notice early in the day that you will probably lose more than 50 rep-points because of the rep-cap, you can use the points for a bounty (on your own, or on someone else's question). That's the only way I'm aware of of how not to "lose" those points completely.
(Well, actually... If you are keeping a list of really bad answers, you can go and use the extraneous points on downvoting the bad answers. But who would do that, really? ;P )
Answer: The points normally awarded for votes on your questions or answers are lost.
But the reputation cap applies only to votes on questions & answers. Not on bounties or accepted answers.
But all isn't lost:

all votes you collected on your answers after the cap is effective still count for the tag badges awards.
a very good question or answer (lots of votes, generally 8 votes) appears in the 10k tools (questions/answers with extreme votes), and may attract more upvotes the next day, and those will bring rep.
more than 200 points per day counts for the "epic" and "legendary" badge, although you don't need rep. capping for that. 200 with accepted answers or bounties count.


Is there a step by step tutorial on how to compile from source for Monero cli on ubuntu 16?

Question: Is there an easy to follow step by step guide on how to compile monero from source? Alot of the times I compiled previously it stops due to something missing, which goes for many times installing anything from source it seems.
Answer: This is what I did on a ubuntu 16.04.
Dependencies
First I installed all the dependencies show here

sudo apt-get install libssl-dev build-essential cmake pkg-config libboost-all-dev libzmq3-dev libunbound-dev libsodium-dev

And build this dependency manually.

sudo apt-get install libgtest-dev && cd /usr/src/gtest && sudo cmake . && sudo make && sudo mv libg* /usr/lib/

Source Code
Next get the source code via git.

git clone --recursive https://github.com/monero-project/monero

If git is not found install it via

sudo apt-get install git

Than go into the monero folder and build it via:

cd monero
make

On a oDroid c2 mini pc this took about 8-10 hours.
For me the tests fail in the end but the executables were in
<code>monero/build/release/bin
</code>
All this information can be found in the readme from the monero repository here
Answer: Compiling from source is not easy, even for experienced users.
You sure you want to compile from source or are you really asking how to get the Cli version working on your Ubuntu software?
Comment: yes i want to learn how to compile from source.
Answer: If that's what you want, I would start Googling questions.  I don't think you'll find a step by step guide here.
Answer: google:
monero compile site:github.com
Almost related
Compile on Centos 6

Compile on Centos 6 #2085
  @knutov opened this issue
  11 months ago
How to compile on Centos 6?

Comment

@moneromooo-monero
  commented 11 months ago
make, or make release-static
Install all the things it needs and complains about.
If errors which aren't due to missing dependencies, post here

Pretty much common way - fighting complains.


Does 'yuki' really mean happiness?

Question: Besides the obvious 'snow', someone listed the name Yuki on a name website as also meaning happiness, blessing, or good fortune using the characters 幸き. Dictionaries list that 幸 can become こ / さき / さし / さっ / とも / ひろ / みゆき / ゆ / ゆき / よし. Yu and Yuki are listed at the end, but is it accurate to say that this name means happiness?
Comment: I think that the most common word to happiness is 「幸せ」 which share the same kanji with 「幸き」. I'm not exactly sure, but it seems likely!
Comment: This is a case of [nanori](https://en.wikipedia.org/wiki/Nanori) where a kanji can have specialized readings in Japanese names. For example, [元渕 幸(Yuki Motobuchi)](https://ja.wikipedia.org/wiki/%E5%85%83%E6%B8%95%E5%B9%B8)
Comment: AFAIK, it's rare ([but possible](https://japanese.stackexchange.com/questions/6744/)) to mix kanji with hiragana/katakana in someone's name; usually, they just use either kanji 幸, or hiragana/katakana ゆき/ユキ, but not 幸き. So, to answer your question directly: yes, it's possible to use either (though the former looks weird to me, but I'm not a native speaker). On the other hand, all the readings stated in the question can be represented by a single character 幸 if it's used in a name.
Comment: @AndrewT.  In your example, Yuki did not need the き character. Can it be spelled either way as 幸き or just 幸 with more or less the same idea, depending on what the person wants?
Answer:
Does 'yuki' really mean happiness?

I feel like this is a loaded question, so let's break it down.

The character 幸 means "happiness".
If the name ゆき is written using this kanji, then it also means "happiness".
ゆき by itself does not necessarily mean anything—ゆ and き simply represent sounds.

However, context could easily provide a meaning to those sounds, and ゆき as a word has several different meanings.
If you knew someone named 'Yuki' who spelled it simply ゆき (or possibly ユキ), it might not have any meaning.

If you see someone's name written as 幸, you'd be wise not to assume it's read as ゆき (or anything else).
Answer: The question is asking about the word yuki and its relation to the meaning happiness. Kanji spellings do not always reflect the meaning of a word.
Looking up yuki in several monolingual dictionaries, we find other words pronounced yuki, such as 裄 (some part of a kimono) or 斎木 (some tree used in rituals), but these do not seem to be related.
The word 幸 with the reading saki or sachi means happiness,  fortune, luck (or products of the sea). This reading is closer to yuki, but offers no explanation how we would get from saki to yuki.
Now, checking a kanji dictionary for 幸, it lists the reading miyuki as a kunyomi (Japanese) reading for the kanji; and elaborates on its meaning:

みゆき。天子が出かけることをいう敬語。▽思いがけないさいわいの意から。 (学研漢和大字典)

That is, miyuki is a respectful expression referring to the emperor going outside or taking a trip. Furthermore, the dictionary attributes the kanji spelling to it being a metaphor for likening the emperor showing himself in public as an unexpected ― but fortunate ― happening.
The word miyuki seems to me to be a combination of the honoric prefix 御【mi】 and 行【yu】き (noun form of yuku, to go). Checking a dictionary such as the 大辞泉, they seem to agree.
This also nicely separates the word into the two parts mi and yuki. So my assumption is that the reading yuki derives from a shortening of miyuki. In this case, I'd say it is related to happiness, but does not mean that.
As for personal names, if the parents give their child a name that is read with yuki and spelled with 幸, there is a good chance they intend the meaning of happiness and I guess in that sense it could be said to mean happiness.
Comment: This answer is the most accurate and complete one IMO.
Answer: I have found that sometimes parents are very creative with their use of kanji when naming children.  You see a similar thing happen in the United States when people start getting creative with the spelling of names (like Aleks instead of Alex).
Jisho.org says the kanji means the following: happiness, blessing, fortune.
You ask:

Yu and Yuki are listed at the end, but is it accurate to say that this name means happiness?

I say that you are quite possibly right, but it may be difficult to know for sure without having talked to the parents.  I would imagine that your understanding is correct though.

Does 'yuki' really mean happiness?


What is IP address management ? Why its needed ? How does the vendors like Bluecat Networks and Infoblox solves the IPAM problem?

Question: Recently I heard a term IPAM i.e IP Address management. Theoretically I got the definition from Wikipedia, but couldn't understand its actual need. Since for that we have DHCP then What is the need for seperate IP management service or hardware.
Comment: Please don't require an open-ended discussion of IPAM solutions;  it would be very helpful if you explained what exactly is confusing in your research thus far.
Answer: IPAM is the solution to using notepad to manage thousands (sometimes millions) of IP addresses. If you have a large enough IP space to manage, it's necessity will become immediately understood.
DHCP would be great if all hosts always got their addresses from the server, but that isn't always the case. If you were a provider that had a downstream network, it wouldn't be common to service their IP space.  Maybe someone deploying assets at your site wants to hardcode the addresses.  There is an infinite amount of 'what-ifs' when it comes to thousands of devices.
Most modern IPAM solutions provide additional features that you just can't be offered by DHCP, such as

Automated subnet polling
IP usage logging
Subnet usage statistics
DNS lookups

This is by no means an extensive list, just a listing of some of the common features most people look for. If you want more detail on some tools that are fairly popular, check out IPplan.
Comment: I didn't understand `DHCP would be great if all hosts always got their addresses from the server, but that isn't always the case.` I still think that all the Internet Service Provider uses DHCP to allocate IP address to its customer and DHCP have the capability to allocate and reclaim the IP address.
Comment: I simply dont see any use of why people will assign manual IP address to the networked devices and keep their accounting.
Comment: @Surfing_SO That isn't how it works. If an ISP allocates a certain subnet to a customer, the burden falls on the customer to provision those addresses how they wish.
Answer: We use Solarwinds' free IPAM for managing several aspects of our network. It's easier to assign our HVAC damper (and other devices) controllers IP addresses manually than to have DHCP running. IPAM allows us to all work in the same management database, reserve addresses, make notes about addresses, detect nodes that are offline for a while, and several other cool things. We also use it to manage the server network. The whole 192.168.169.0/24 network is assigned to our server network, and we seperate devices by scope, where active directory starts at 192.168.169.10, ans exchange starts at 192.168.169.25. This is all entered in the database for managing IP addresses, and reservations, comments, and other basic information. I'm not sure about Bluecar or Infoblox specifically, but those are just a few of the benefits and uses for IPAM suites.
I know several people that use them in network connected manufacturing robots as well as other industrial applications. I believe some software suites will tie into CRM and Monitoring solutions as well.
Comment: Why on earth you want to assign IP address manually to to the networked devices. Can you provide an example where manual allocation is the only sample and not using automatic allocation like DHCP.
Comment: You can start by reading the above comment by @Fizzle (which it seems you have). There are a lot of good reasons to assign addresses manually. I am not going to have a DHCP server giving my servers their IP addresses. That's just not how things work. People may disagree about an automation or probe network, and to each his own. My experience has taught me that my setup is easier, more effective, and more reliable; even in the face of having to make network changes that affect those controllers. With proper planning, this should almost never be a concern.
Answer:
Recently I heard a term IPAM i.e IP Address management. Theoretically I got the definition from Wikipedia, but couldn't understand its actual need. Since for that we have DHCP then What is the need for seperate IP management service or hardware.

DHCP is just address assignment, usually just for users.
Most networking isn't just assigning user space addresses. Got to keep track of router-router connections, the DHCP server itself (it can't get DHCP from itself), those devices that you just want to static (set and forget type stuff) without setting up DHCP to assign static, and then you have to deal with equipment that must always work, no matter if DHCP is there or not. Then there are the networks that you just don't put a DHCP server -- either because it's a pain, a bother, faster than DHCP, or really not needed.
IPAM is just to keep track of all IP address assignments, not just the user space. Most are better than a spreadsheet and anything is better than reading the routing tables when managing networks. Smaller networks, especially home networks, would never need IPAM. The software only really becomes useful after a certain scale; before then too expensive to justify, after then just another network tool.


If a product doesnt meet one claim of a patent, would it get patent infringement notice?

Question: If there is a patent for a product that has 16 claims and I sell a similar product and my product falls under 15 claims of the patented product but not the 16th claim then is it sellable? Or would I still get patent infringement notice?
Answer: Each claim is taken on its own. If your product meets everything laid out in any single claim then your product infringes that claim, and therefore infringes the patent.
You may have have heard that you need to have all elements of a claim to infringe - that is correct, all elements of any claim, not all claims.
You and your product may or may not attract the attention of the patent owner.
Comment: Thank you so much George for your valuable answer. Just a small follow-up question; this infringement of claim on individual basis applies to both design and utility patents?
Comment: Design patents, by definition, only have a single claim although they can have multiple embodiments.
Comment: From the MPEP A Single Claim

A design patent application may only include a single claim. The claim defines the design which applicant wishes to patent, in terms of the article in which it is embodied or applied. The claim must be in formal terms to "The ornamental design for (the article which embodies the design or to which it is applied) as shown." The description of the article in the claim should be consistent in terminology with the title of the invention. https://www.uspto.gov/patents-getting-started/patent-basics/types-patent-applications/design-patent-application-guide#single


How do I design a translucent vinyl glass door sticker?

Question: I have to make a sticker for a pair of glass doors. It will be printed on vinyl and has to be translucent. Is there any specific process to incorporate the translucency? I've designed clear stickers before but I'm unsure about a translucent one. Do I reduce the opacity of the body or do I leave it for the printers?
Answer: The material itself is translucent. So you you need to visually/mentally factor that in when selecting colors to print. Think of it this way - if you print your solid blue on a clear plastic, an opaque white card, or a translucent vinyl - how that solid blue will look? It depends what that ink hits from medium to medium. The only way in my experience anything looks "solid" on a clear or translucent material is if spot white ink is additionally used. Have you read your product specs from the printer, or asked them?
Answer: 1) Ask your PSP (Print Service Provider). Always ask them how they want this handled in special conditions such as these.
2) If only one element in your design is translucent - say a given field colour (fill inside a design element) but not say the primary linework - almost always the answer is that they have a specific spot ink callout they want used for the special translucent ink - if not, you choose a spot colour and designate it only for that translucent colour.
3) If the whole piece is translucent, I'd simply ask your PSP what colour system or even colour space they'd prefer you to use - they may have a specific set of Pantone Colours they prefer, or they may say "Oh, generic RGB" or even something highly specific to the colour profile of their given output device "Use Adobe RGB 1998" or "Use RGB Wide Gamut" or "CMYK - our machine has an in-line RIP we prefer to use, as designer's tools all seem to goof the colour when we let them go RGB"; they might even provide you a colour profile file to install and use - it's up to their process and their device.


What needs or works better with DC than with AC electric?

Question: Solar power is becoming more popular, and it seems a lot of people who have solar panels have a DC to AC inverter. It seems ironic to convert DC electric to AC, and then the the AC gets converted back to DC to run a computer. I believe all digital hardware runs on DC power. Do LED light bulbs, LED TVs, LCD TVs, have to convert AC to DC? How about motors. What are the trade offs between AC and DC motors?
Answer: TVs, PCs and LED bulbs all run off varying DC voltage, although you'll find interestingly enough that the most efficient DC->DC converters are actually DC->AC->DC converters. (See resonant converter)
I'll expand a bit more on the motor front. AC induction motors (that run directly off AC mains) have been the standard industrial power source for many many years. They are cheap and very reliable. A large portion of the electricity generated (see below) is used to drive a AC induction motor in one form or another (as a water pump, air pump, conveyor belt and so on). Newer more efficient AC synchronous motors (being used in some electric cars, washing machines and more), have variable-frequency inverters inside them anyway, and so can be fed with AC (which is rectified) or DC with minimal loss in efficiency. DC motors are usually much smaller than both these types by comparison, and even then, they are often used with pulse-width modulated (PWM) drives which would rectify any AC before adjusting the voltage.
Induction motor usage stats:
30% of total energy (according to http://www.mpoweruk.com/motorsac.htm)
80% of total mechanical energy (according to http://electrical4u.com/construction-of-three-phase-induction-motor).
No actual studies provided by these sites though.
I found some similar questions
Why is high voltage AC more common than high voltage DC?
Why are the power transmission/distribution systems AC and not DC?
Neophyte question about AC vs. DC (especially for powering a home)
Comment: I think you forgot to finish your first sentence.
Answer: I'll bet real money that the AC vs DC war question has been asked here before.
AC is hugely advantageous for long distance transport of electricity (i.e. the 'grid'), because it can be stepped up to much higher voltages with a relatively simple & reliable transformer.  With higher voltage, to deliver any given amount of power you need less current - less current means thinner wires - and over tens, hundreds or even thousands of km/mi, less cooper means far far $cheaper, because power loss in wires is proportional to the square of the current.
But for short distances & several reasons, DC distribution is indeed seeing a come-back, in server rack power distribution, in small-scale renewables systems, etc.
Comment: FYI (or FOPI): [War of Currents](http://en.wikipedia.org/wiki/War_of_Currents).


Are big corporations the biggest beneficiaries from farming subsidies?

Question: I've heard that big companies are the biggest beneficiaries of agricultural subsidies (in the US and other western countries). This would to me seem to be the opposite of the intention of those policies, and I'd like to know how true this statistic is.
Comment: I don't think that is the opposite intention at all... The intention has always been protectionism both in the US and EU. And since you say "biggest" that is self-evidently true. Big farms get big subsidies.
Comment: intent of government is to max out power, get bigger and share the spoils to rent seekers.
Comment: One example of this idea being published with regards to the UK: http://www.monbiot.com/2013/07/10/the-landed-mafia/
Comment: @Lennart: Good points.
Answer: I'm unsure of where to find this for other countries, but I was able to find THIS report from the Government Accountability Office. The report may be a bit dated (2001, so 10 years old), but in looking through the first part alone, I see nothing but tables and charts showing that big farms receive more subsidy payments than medium or small farms.
Skimming aside, the report quite clearly states:

...the 7 percent of farms nationwide with gross agricultural sales of $250,000 or more— received about 45 percent of the payments.

As Lennart pointed out though, larger farms are, by definition, producing more crops. Subsidies (unsure of units, but say payed per volume or weight), therefore, would be paid in higher proportion to those producing more goods.
I did find the chart below, which suggests that small farms may actually be getting more payments per value of their establishments compared to large farms:

This bit preceded that table:

For example in 1999, large farms received 45 percent of the payments, while accounting for
46 percent of the planted acreage and 52 percent of the value of production of the eligible crops. Small farms received 14 percent of the payments and accounted for 10 percent of planted acreage and 8 percent of the value of production.

I was actually curious about this, wondering if large farms received a proportional payment per volume of crop compared to small farms. It seems that they actually receive less by value than small farms!
The report does give some explanations for the smaller payments to smaller farms, one being the obvious one already mentioned that larger farms produce more product. Another, however, was based on the type of goods typically produced by the farm sizes:

...beef is not one of the commodities for which farm payments are generally made. According to the Economic Research Service officials, beef is the primary commodity of about 40 percent of small farms, compared to 20 percent of medium farms and 10 percent of large ones.

So, small farms are substantially more targeted toward a non-subsidized product compared to their larger counterparts, and thus aren't receiving subsidies for those goods.
It would be great to see more current data on this topic, as the intro to the report states (addressed to the Chairman of the Committee on Agriculture at the time):

Dear Mr. Chairman,
...Concerned that farm payments are not being effectively targeted to aid the
survival of small farms and the entry of young people into agriculture, you
asked us to (1) determine the distribution of farm payments over the past
decade by farm size, operators' age, state, and crop and (2) identify the
major barriers that make it difficult for young people to enter farming.

This leaves me wondering what the results were -- were the findings that the situation at the time was fair, or was action taken to rectify anything, have payment distributions changed much in 10 years, etc.? If I find answers to these questions, I'll update the answer to include them!
Comment: and how does it play out if you compare subsidies as a percentage of turnover? If a company making $100M a year gets $1M subsidies, it's 1%. A company making $100K a year that gets $10K, it's 10%. Of course the "all it does is making big corporations richer" crowd deliberately doesn't mention such poignant little pesky details that derail their entire non-argument.
Comment: Excellent point. It would make sense that smaller farms receive a smaller portion of total payouts. If I get a chance, I may try to find out the total amount of payouts and look at the cash distribution (%) compared to the % of cumulative revenue generated by farms of a particular size (as in, if there's vastly more small farms (higher n), their total market share might be comparable to smaller medium/large sized farms).


iPad photo blogging recommendation

Question: Simple question:
What is the simplest, most minimal app for both creating/managing blogs and posting photos from the built-in camera?
Answer: I don't know what the simplest is, as I cannot claim to have used them all, but I can suggest using a Tumblr blog with the Tumblr iOS client (or one of the various other Tumblr compatible ones), as it's pretty straightforward at both the web and iPad client end.
Comment: Unfortunately the official tumblr client requires many taps/decisions and occasional forays to safari in order to fully manage a tumblog.
Answer: Posterous might be the easiest solution.
They have a proper app and stuff, but afaik you can control it mostly through email. So setting up a blog requires you to email firstname.lastname@example.com with your first email. That'll get posts up online. To add more posts, you just keep emailing them there. To be fair, to manage stuff, you do need to visit the website (or use the app - never tried it myself.) But in terms of actually updating, emailing photos and text is something that the iPad and iPhone do very well.

iPad photo blogging recommendation


Vintage Car Models

Question: I've been looking for a recording of a '68 Plymouth Barracuda or something close that has a v80 engine, but I can't seem to find it anywhere. Have any of you guys recorded this car and are willing to share? I need the start of the engine, and an idling and driving of the car while it's on for the scene. Thanks!
Answer: I recorded a V8 Cuda years ago for a film, will have a look
Comment: I have a bunch of onboard recordings (exhaust mic + engine mic) and some exterior start/away/passbys etc... recorded back in 2001 so 16bit 44.1k on a Tascam DAP1 DAT recorder...
Comment: ps what do u mean by 'idling' of the car when driving? either its idling & stationary, or its driving (med? slow? fast? accelerating? decelerating?)
Comment: try these:
http://www.musicofsound.co.nz/transfer/cudaV8.zip
Comment: Ah, the venerable DAP1. I did a lot of recording with one of those over the last 15 years...
Comment: Thanks Tim! These shall work. I meant to put an "idling and driving of the car."
BTW can't wait to hear the tortured piano library man.
Comment: Isn't Social Sound Design the best?

Vintage Car Models


Create ebooks from books

Question: I have seen that there are many ebooks available on web. How are they created from a book or do you actually write one by hand? If they capture an image from a book, how are the fonts made copyable?
Answer: for most part, the masters are digital, and its a simple matter of saving it as a pdf (in fact some publishers even release the books as e-books before the physical copy is released)
Otherwise its a matter of scanning the books, using OCR to convert the bulk of it to text, re-proof reading it, and adding any images back. Fonts are fairly standard, or a close enough font is used.
Answer: In the past eBooks were mostly in PDF format but the ebooks that are read on the Kindle are in .mobi format and the books that are read on any other reader are in ePub format. Both formats are based on HTML, the type of markup that is used for webpages. PDFs come in two forms  - if you scan anything then the scans can be turned into a PDF, but that is just a picture of the document. What's important is the OCR process that turns the text in the document into machine-readable text - the type of text that you and I are using right here. OCR isn't perfect but there are some methods that are better than others. Once the text is in machine-readable form it can be marked up in HTML and put in .mobi or ePub format.

Create ebooks from books


Is the CAPM beta equivalent to the coefficient estimate of an OLS regression?

Question: The $\beta_i$ of an asset or portfolio is defined as its covariance with the market (which itself therefore has a beta of $\beta_m = 1$). The CAPM looks a lot like a simple linear regression model. Is its $\beta$ equivalent to the coefficient estimate obtained from an ordinary least squares regression on the CAPM equation?
Comment: the beta from a CAPM is founded using beta from regression rates of asset minus risk free rate on market rates minus risk free rate
Comment: so $\beta=\rho\frac{\sigma_x}{\sigma_y}$ where $\rho=Corr(X,Y)$ and $X=$ asset rate minus risk free rate and $Y=$ market rate minus risk free rate
Answer: They are actually exactly the same thing. CAPM say that expected risk premia are "explained" by the risk premium on the mean variance efficient (MVE) portfolio
$$
R^i_{t+1} - R^f = \delta (R^{MVE}_{t+1}-R^f) + \varepsilon_{t+1}
$$
De facto, you are saying that the systematic risk is just the projection of risk premia on MVE risk premium, and OLS are exactly the same thing as a linear projection. Indeed it must be the case that $$\delta= \frac{Cov(R^{MVE}_{t+1},R^i_{t+1})}{Var(R^{MVE}_{t+1})}=\beta^{OLS}$$
And by the way, when investors price by means of discounted expected payoffs, i.e.when
$$
p_t^i=\mathbb{E}_t \frac{d_{t+1}}{1+R^i_{t+1}}
$$
expected returns always admit a beta representation, i.e. we can always rewrite
$$
\mathbb{E}_t R^i_{t+1} =\alpha_0 + \beta\lambda
$$
Answer: No.  The CAPM is an equilibrium model.  It describes relationships between expectations.  With OLS you typically estimate a distribution for realized returns in the future (or sometimes even only in the past...).
$R^i_{t+1} - R^f = \delta (R^{MVE}_{t+1}-R^f) + \varepsilon_{t+1}$
is not an equation from the CAPM.
The CAPM SML is: $r+E(r_i - r) = r+\beta_i E(r_M-r)$
There is no index $t$, and no random term, as the CAPM describes only expectations, and only for one period.
an equation like this:
$\mathbb{E}_t R^i_{t+1} =\alpha_0 + \beta\lambda$
can always be estimated for any pair of dependent and independent variable and any data set, no matter how investors price anything.
It's sad that so many use historical data only to estimate betas - as it reads on any retail mutual fund fact sheet, that past performance is no guarantee for future performance...  the same holds for distributions...  of course.
But then, let's say you're a publicly traded corporation, how you estimate beta to get a discount rate for a future risky cash flow, should depend on how you believe the market estimates beta.
In principle, though, any approach you find convincing, could be justified, as Sharpe pointed out:
"Much confusion has arisen concerning the relationship between the equilibrium results of the CAPM and the underlying relationships among security returns. As can be seen, the CAPM makes no assumptions about the "return generating process". Hence, its results are completely consistent with any such process." William F. Sharpe, Capital Asset Prices with and without Negative Holdings, Nobel lecture, Dec. 7th 1990, Economic Sciences 1990, p. 320
Answer: I'm not sure I'd use the word "equivalent" but you have the right idea.  Instead, I would say OLS regression is a very common way of estimating CAPM beta.
CAPM is a linear model to calculate the an appropriate return of an asset given its non-diversifiable risk.  OLS is really a method for solving certain types of linear models.  So OLS can be used on the CAPM model but it is used on many, many other models as well.
Also, there are other methods used for estimating CAPM betas other than OLS.  Some may even have better predictive power, but OLS is by far the most common.
Comment: What are these other methods? Do they rigorously fit into the framework of CAPM?


How to change the favicon in Joomla

Question: So I am new to Joomla, and am trying to change our favicon. I already have a 16*16 .ico image, but can't figure out how to use it. I don't know how to use cPanel. What do I do?
Answer: The favicon.ico file needs to be copied to the default template folder. For example, if you are using the Protostar template, the file would be copied to:
/templates/protostar/favicon.ico

You might also wish to copy the favicon.ico file to the root folder of your website e.g. /public_html or similar as this can improve performance slightly and reduce error messages being logged when the file is not found.
When you log in to cPanel, look for File Manager which you can use to upload files to the desired locations.
Alternatively, you could use an FTP client (the credentials are usually the same as cPanel credentials) to upload the files.
Answer: That really depends on the template you're using.
For most cases all you need to do is upload the favicon.ico file into the root directory your website (it can be: public_html , htdocs , httpdocs etc.)
Sometimes you need to copy the .ico file also into the template directory, which is under: /public_html/templates/your_template_name/
Please use browser tool "Inspect Element" and determine where you should put that file.
You can always provide us with your site name and we will be able to check this for you.
Comment: It does depend on the template but the usual location for the favicon file is the template folder: https://docs.joomla.org/changing_the_site_favicon
Answer: Answer provided by Neil is my vote for "The Answer" - but if you're looking for a more robust favicon option, you can do so with this favicon generator:
http://www.favicon-generator.org/
It will provide you with a favicon file, and meta data to include in your header. You just need to adjust the file path accordingly.  The advantage of using this is that it will generate icons for a variety of devices. That's nice if you anticipate your users will be saving the site to their phone icons.
Comment: Thanks! A similar icon generator website (created using Joomla) is http://iconifier.net. Full disclosure: I created iconifier.net. :)
Comment: Well, nice work!
Answer: I had to comment out the following line from joomla template.
<jdoc:include type="head" />

Now when reloading the homepage, the new favicon appeared, after which I un-commented the above line.
Comment: This will deactivate the output of the head, you shouldn't do this..
Comment: Yeah but only temporarily, once the browser updates it's cache we are going to "un-comment" that line. (re enable the above code).

How to change the favicon in Joomla


Brake issues 2004 Pontiac Grand Prix

Question: Intermittently, my brake pedal will drop slightly, and there will be a loud clunking noise, metal on metal sounding.  Normally happens at slow speeds, weather conditions don't seem to be a factor.
Comment: That does seem way odd. Is the metal to metal clunk inside the passenger compartment or outside?  Two minute test.  Turn the car  off, vehicle in Park, key out of the ignition, flashlight in hand.  Open the drivers door, carefully kneel on the ground outside of the car and look underneath the steering wheel area.  Push the brake lever with your hand. Do you see anything not connected? Do you hear the metal on metal clunk when you do this? If outside, it's possible there are loose bolts at one of the wheel cylinders.  If so, that is dangerous and needs to be fixed pronto.
Answer: sounds like something to do with the brake hydraulics. possibly brake booster?
Need to state more information like HOW & WHEN things happen... What CAR? etc.
...
The noise is very odd, but MIGHT be attributable to sticking brake components that suddenly come loose.
Possible that some other kind of electronic control on your brakes is acting up as well, whether in reaction to sticking calipers or not. (Traction Control, Electronic Stability, etc.). Not sure if your car has these slightly more techy features.
...
Unless you work on cars, take it to a mechanic and get it diagnosed and fixed.
Brakes are safety critical so you dont want to leave it alone or do shoddy work.
If you want, u can get it diagnosed and come back here to help you not get swindled.

How hard are you braking when you experience this?
Do you know what the feeling of ABS turning on feels like? The pedal moves a little back and forth and you will feel the movement when braking, sound similar?
I am pretty sure there is some procedure to test the ABS. If anything, you most likely can at least do a resistance check on the electronic components, which takes like 10 minutes and no $$$ at all. Have someone do some sort of REAL diagnostics before simply replacing parts.
Comment: it's a 2004 Pontiac Grand Prix.  It usually happens when slowing down or braking into a turn.  I took it to a mechanic, they looked at all the brake parts and couldn't see anything.  They drove it repeatedly and of course it wouldn't do it for them.  Hubby is a gear head, thinks it may be a sticking caliper?  Mechanic says it might be the ABS module (BIG bucks) he's pretty trustworthy, but stumped and suggested I get other opinions before we go the route of replacing that part. I'll mention the brake booster and see what they both think.
Comment: (edit/include that in your question)
i also think it could be a sticking caliper, but ABS is a good thing to check. (if you mentioned the pedal moving, i think thats probably why the mechanic thinks its abs).
Comment: Car has traction control and stability features, fully loaded for a 2004 model. Has ABS also.
Comment: Braking pressure is normal for slowing down/stop light, braking into a turn.  It's never happened during hard braking or at high speed braking. Hubby and mechanic are stumped and we all want other opinions before we start replacing parts. Thanks agent provocateur for your advice.  I'll ask about resistance check.  The pedal moves down quite a bit when this happens, almost as if there is a problem with the brake lines (pumping brakes to get them back up) The pedal moving more extreme than the ABS coming on and off.  car also has Traction Control an tried with on / off too, makes no difference.
Comment: Got it figured out, it was the front wheel bearings and the ABS sensor.  Total repair cost $224.48.
Comment: thats not bad. nice, happy for you.

Brake issues 2004 Pontiac Grand Prix


Pocketwizards vs wireless transmitters?

Question: What are the differences between a set of Pocketwizards and a set with a wireless transmitter and receiver. Don't they do the same thing?
Comment: Why do you think  Pocketwizard isn't a wireless transmitter/receiver system?
Comment: I just thought that they were two different things. That is why I asked.
Answer: Radio flash triggers are a type of device.  PocketWizard is a specific brand of radio flash trigger.  So, yes, they do the same thing.  But while all PocketWizards are radio flash triggers, not all radio flash triggers are Pocketwizards.
In addition, PocketWizard has the highest reputation for reliability, and are the oldest radio trigger brand that's still on the market. Their triggers are built in to some Sekonic flash meters. And they have the best backwards compatibility with older units, but in order to retain this compatibility, they're using the same radio frequencies they always have. From the PocketWizards website:

In North and South America (and some parts of Asia) we use the 340 – 354 MHz range because it is the least crowded frequency range for our class of wireless triggering devices.  Other choices like 433 MHz, 900 – 930 MHz ISM band, or the 2.4 GHz band have many more interfering devices on them.

Most of the newer, less expensive triggers that you see operating on 2.4 GHz, because it doesn't require licensing.  But it's also where Wi-Fi and Bluetooth operate.

Pocketwizards vs wireless transmitters?


Gaussian distribution is isotropic?

Question: I was in a seminar today and the lecturer said that the gaussian distribution is isotropic. What does it mean for a distribution to be isotropic? It seems like he is using this property for the pseudo-independence of vectors where each entry is sampled from the normal distribution.
Comment: In general, a multivariate normal distribution can be anisotropic depending on the covariance matrix.  There has.  clearly been some miscommunication somewhere along the way.
Comment: Isotropy can refer to invariance under rotation, or that the covariance matrix is the identity. (Those two are generally not the same). A reference for the first definition is "Stochastic and Integral Geometry" by Schneider & Weil, a reference for the second is "High-Dimensional Probability" by Roman Vershynin.
Answer: TLDR: An isotropic gaussian is one where the covariance matrix is represented by the simplified matrix $\Sigma = \sigma^{2}I$.
Some motivations:
Consider the traditional gaussian distribution:
$$
\mathcal{N}(\mu,\,\Sigma)
$$
where $\mu$ is the mean and $\Sigma$ is the covariance matrix.
Consider how the number of free parameters in this Gaussian grows as the number of dimensions grows.
$\mu$ will have a linear growth.
$\Sigma$ will have a quadratic growth!
This quadratic growth can be very computationally expensive, so $\Sigma$ is often restricted as $\Sigma = \sigma^{2}I$ where $\sigma^{2}I$ is a scalar variance multiplied by an identity matrix.
Note that this results in $\Sigma$ where all dimensions are independent and where the variance of each dimension is the same. So the gaussian will be circular/spherical.
Disclaimer: Not a mathematician, and I only just learned about this so may be missing some things :)
Hope that helps!
Comment: The variables of the multivariate Gaussian may not be independent, even if they have zero covariance. Covariance is a measure of only linear association. Independence implies zero covariance but not vice versa. See this [example](https://stats.stackexchange.com/questions/12842/covariance-and-independence).
Comment: @mloning, your comment is a bit misleading here.  When a random vector has as a multivariate normal, 0 covariance does indeed imply independence.  All of this gets its own wikipedia page: https://en.wikipedia.org/wiki/Normally_distributed_and_uncorrelated_does_not_imply_independent

The notation above suggests to me multivariate normality, so, it's fine.

Another way in which the normal distribution is magical
Comment: Yes, wasn't aware of that, thanks for the clarification!
Comment: Another motivation:  The conjugate prior of a multivariate normal distribution with unit variance is isotropic normal.  Like you say, there's no need for all those parameters!
Comment: Easy to understand for beginners. As I am not a native English speaker, I was confused by the word `isotropic`.
Answer: I'd just like to add a bit of visuals to the other answers.
When the variables are independent, i.e. the distrubtion is isotropic, it means that the distribution is aligned with the axis.
For example, for $\Sigma = \begin{pmatrix}1 & 0 \\ 0 & 30\end{pmatrix}$, you'd get something like this:

So, what happens when it is not isotropic? For example, when $\Sigma = \begin{pmatrix}1 & 15 \\ 15 & 30\end{pmatrix}$, the distribution appears "rotated", no longer aligned with the axes:

Note that this is just an example, the $\Sigma$ above is invalid since it is not PSD.

Code:
import numpy as np
from matplotlib import pyplot as plt

pts = np.random.multivariate_normal([0, 0], [[1,15],[15,31]], size=10000, check_valid='warn')

plt.scatter(pts[:, 0], pts[:, 1], s=1)
plt.xlim((-30,30))
plt.ylim((-30,30))

Comment: This seems to contradict the other answers, the matrix [1 0;0 30] is a diagonal matrix, but it can't be written as $\sigma I$ since not all diagonal entries are the same. I'm not sure which one it should be
Comment: Isotropic means the same in all directions which the distribution in this example clearly is not. Aligned with the axes is not the same as isotropic in general, in fact it is only the same when the covariance matrix can be written as $\sigma I$ as other commenters have noted.
Comment: The example is incorrect. Isotropic means the probability density is equal (iso) in every direction (tropic). In gaussians this can be achieved with a $\sigma^2 I$ covariance matrix.
Comment: This answer is incorrect, the covariance matrix [1 0; 0 30] is not an isotropic Gaussian.  You should edit/remove this as it's somehow accrued +16 points and could mislead people.
Answer: I am not a math major student but I will give a try to describe my understanding: an isotropic gaussian distribution means a multidimensional gaussian distribution with its variance matrix as an identity matrix multiplied by the same number on its diagonal. Each dimension can be seen as an independent one-dimension gaussian distribution (no covariance exists).
Answer: Thanks to Tomoiagă, valuable learning opportunity. Explanation for psd in his answer.
w.r.t material in course Probabilistic Deep Learning with TensorFlow 2 in coursera.
the definition for positive semi-definite:

A symmetric matrix $M \in \mathbb{R}^{d\times d}$ is positive
semi-definite if it satisfies $b^TMb \ge 0$ for all nonzero
$b\in\mathbb{R}^d$. If, in addition, we have $b^TMb = 0 \Rightarrow
> b=0$ then $M$ is positive definite.

In one word: the valid covariance matrix should be symmetry and positive (semi-)definite. However, how to check the $\Sigma$ satisfied with the requirement?
Here comes The Cholesky decomposition

For every real-valued symmetric positive-definite matrix $M$, there is a unique lower-diagonal matrix $L$ that has  positive diagonal entries for which
\begin{equation}
     LL^T = M
 \end{equation}
This is called the Cholesky decomposition of $M$

Let's build some codes.
Given a psd matrix $ \Sigma = \begin{bmatrix} 10 & 5 \\ 5 & 10 \end{bmatrix}$ and a non-psd $ \Sigma = \begin{bmatrix} 10 & 11 \\ 11 & 10 \end{bmatrix}$ as the covariance matrix
sigma = [[10., 5.],[5., 10.]]
np.linalg.cholesky(sigma)

Output:
<tf.Tensor: shape=(2, 2), dtype=float32, numpy= array([[3.1622777, 0.  ],
       [1.5811388, 2.738613 ]], dtype=float32)>

bad_sigma = [[10., 11.], [11., 10.]]
try:
    scale_tril = tf.linalg.cholesky(bad_sigma)
except Exception as e:
    print(e)

Output:
Cholesky decomposition was not successful. The input might not be valid.

For convenience, a lower-triangular matrix is easier to create.
Last, the demo with isotropic Gaussian and non-isotropic ones.
import seaborn as sns
import matplotlib.pyplot as plt
%matplotlib inline

## isotropic normal
sigma = [[1., 0.],[0., 1.]]
lower_triangular = np.linalg.cholesky(sigma)
print(lower_triangular)
sigma = np.matmul(lower_triangular, np.transpose(lower_triangular))
##

bivariate_normal = np.random.multivariate_normal([0, 0], sigma, size=10000, check_valid='warn')

x1 = bivariate_normal[:, 0]
x2 = bivariate_normal[:, 1]
sns.jointplot(x1, x2, kind='kde', space=0, color='b')

isotropic-normal
# #non-isotropic normal
# sigma = [[1. , 0.6], [0.6, 1.]]

non-isotropic-normal

Gaussian distribution is isotropic?


In Ingress, when are links destroyed?

Question: At what level of resonator damage are existing links destroyed?  I had heard that the portal must have more than two resonators remaining for any links to stay up, but I can't find any documentation of this.
Answer: I can bring you my experience on the field: the links on a portal are destroyed when there are two or less resonators remaining.
Sadly, the "official documentation" is more a collection of FAQs than an actual manual, so you'll have to rely on external resources or your direct experience to gather this kind of informations and become a better Agent.
Comment: Right. A Portal needs 3 Resonators to keep his links alive. To link from or to a portal the portal need to be full. Regardless of how charged they are
Answer: After further testing, it appears that all links are dropped once there are only two resonators remaining.  The energy left in the resonators does not seem to matter.
Answer: How far you can link form portal depends on the total energy of the portal.
From my observations, but no calculations:

The link goes down when the energy of the portal goes below energy needed to create that link.

When attacking a portal with multiple links they get destroyed consecutively, not all at once. This supports the above theory.
Answer: The link(s) are dropped once all resonators at the portal are at critical level.
manual source
Answer: As Kappei  said, usually  links go down, when portal has 2 or less resonators, but, I think thats is caused by the total of energy remaining in the portal. (i'm not really sure about it).
Just remember that, you CAN'T make a link from portal A to portal B if some one has less than 8 resonators, namely, the links are made between full portals
Answer: According to Google Ingress help:
Destroy an enemy controlled Link by attacking the Resonators that are deployed on the Portals that anchor the Link. For example, you can fire an XMP to damage a Resonator and reduce its XM health. When all eight resonators have their XM health reduced to the Critical level, then the Link will fail.
Link to text: https://support.google.com/ingress/answer/2808353?hl=en
Answer: I read somewhere, that links drop out, once all the resonators are below a critical energy level. This could be why some links appear to depend on the last 2 resonators?
As in, 6 resonators have faded/destroyed, but the remaining 2 have say 20%. Critical level is 10-15%, so the link stays. The logic that ALL 8 portals are below the critical level, will fail, as the two remaining are above. I may be wrong, but thats how I read it. Keeping two charged up, should therefore hold a link. Might even work with one? But not had time or patience to test this.

In Ingress, when are links destroyed?


Can I bake oatmeal drop cookies in a bar form?

Question: I am making oatmeal cookies for a family get together and was wondering, can I make them as a bar cookie like as in chocolate chip, rather than a drop cookie.
Answer: Most drop cookies that are made by creaming butter and sugar turn out fairly well as bar cookies.
One thing to think about is the additional baking time - since they are thicker, you may have an underdone center even once the top is golden brown.
You should probably bake them slightly longer than you would normally, and check them fairly frequently. I prefer my cookies chewy (almost like cookie dough) in the middle, so I tend to bake them for less time.
Answer: Yes; just spread the dough in a well-greased pan.  I'd use a pan size such that the bars are not too much thicker than the cookies would be, or the cooking time/temperature will be trickier.
You will likely need to lower the oven temperature (I'd try 25 degrees cooler.) and bake for longer.  If you notice the edges browning and the center is still very raw, go ahead and turn the oven down a bit more.  Make sure to pull the pan from the oven when the center is not quite baked through, since it will continue to cook for a few minutes once it's out of the oven.


How can I renew my non-current Indian CPL?

Question: I have not renewed my Indian CPL since 2001 and would like to renew it. what is the procedure as the CAR says nothing about renewing licence below 5700 kgs category.
Since there is no rule what can be done. I am flying regularly on my FAA licence.
Answer:
This is for CAA , each country might have a different rule but in general this is the rule . If you haven't flown in India since 2001 then your license has been expired. So I assume that if you have any other license valid , you have to go to Indian civil aviation with your current  log book and they will request a confirmation from the country that you have got your license from to be sure that your license is still valid in that country.Then you have to do the conversion requirements which generally are 4 exams (for most countries are Law,HP,Nav, Met) and then you also have to go to any ATO in India and you must undergo sufficient ground and flight training for the same category aircraft that you have your other license on , and then do a oral exam and flight test .
If you haven't flown in the last 10 years , you have to do all CPL exams again .
Good luck.


Does a property owner with beach frontage need to post the beach for it to be considered trespassing to walk across the property?

Question: In MA, is it legal to cross someone's property on the ocean beach if the beach is not developed and is not posted?
Comment: It's complicated. See http://massrealestatelawblog.com/2012/07/20/footprints-in-the-sand-massachusetts-beach-access-law/
Answer: In many US states, beaches, or at least the tidal areas of beaches, have unlimited public access. In MA this is not so, although some notification, such a s a sign, will generally be required before any law against trespassing can be enforced.
According to an article published by a real estate law firm:

Massachusetts has a unique set of laws giving coastal property owners more extensive private rights to beachfront area than other states. In most coastal states, there is unlimited public access to beachfront areas and you can walk unfettered along the beach. In Massachusetts, however, that is not the case. Here private coastal property owners own the beach area adjacent to their properties down to the mean low tide area, with some limited public access exceptions. This is how the concept of "private" beach areas have been established.
The origin of this law dates back to the Mayflower days. In order to facilitate coastal development, under the Colonial Ordinances of 1641-47, the Massachusetts Bay Colony conveyed most, but not all, rights of ownership to the area between the average or mean high water mark and the low water mark (up to 100 "rods," or 1,650 feet, from the high water mark) to all private coastal landowners. The land—but not the water—between the two tide marks is known as "private tidelands." This typically includes all of the wet sand area on beaches.
Answer: You are not trespassing until you are told you are
Being told may be verbal or by a sign or by a fence or by common expectation (e.g. you can walk to someone's front door but not have a picnic in their garden) but until you know you are on someone's land without permission you are not trespassing.


Upgrade Trusted Platform Module (TPM)?

Question: I have some systems that I am unable to enable Bitlocker on. The TPM wizard reports that the version of the TPM is inadequate to function with bitlocker.
Is it possible to upgrade a TPM to 1.2?
Answer: Maybe. Check with your vendor to see if there are any firmware updates. Most computers have the TPM module built in, so it's not replaceable/upgradeable, but some do have modules that can be upgraded.

Upgrade Trusted Platform Module (TPM)?


Taking notes with a stylus on a capacitive touch device - how do you prevent your hand from causing multi-touch problems?

Question: When taking notes with a stylus on a capacitive touch device like the ipad or android tablets how do you prevent your hand from causing multi-touch problems?  When you write, both the stylus and your hand are touching the screen.  Does the presence of your hand screw up your touch entry just as accidentally placing a second finger on the screen at the wrong time would?
Answer: You are not going to be able to solve this with just the iPad. Typically, tablets like Wacom's will have Palm rejection technology. The screen can detect when the stylus gets close to the screen and switches to stylus mode.  The stylus itself isn't a typical piece of plastic.
I believe the stylus outputs some sort of signal or field that the screen can pickup to switch states.
Now it is possible to code the application to detect which inputs are your hand and which is the stylus, but this is application specific and the capability is not provided by the iPad itself.
Answer: While iOS does not have an OS-level palm-rejection algorithm, many apps have implemented that feature in one way or another.  Some have a specific "writing window" in which you have to write, while others have a "palm rest" area that will not respond to touches.
A few of the many options for iPad: Notability, Notes Plus, Penultimate.  By no means a comprehensive list but these are some of the top sellers and best reviewed. I've used all 3 and enjoy each one for different scenarios, but any one of them would be good for the vast majority of uses.
In addition, another solution you can pursue is using a stylus that promotes a grip style that doesn't necessitate resting the palm.  e.g. The just-released Cosmonaut by Studio Neat, which I'll be trying out as soon as they ship it to me.
Finally, there's a project on Kickstarter for a new "active" stylus technology that is being developed for iPad. This is a different approach that seeks to give finer control than the other styluses out there. Palm rejection is an inherent feature because the stylus generates an active signal recognized by the sensor. The downside to this approach is it will only work with apps that implement the SDK for the stylus.
My recommendation is to start with one of the apps I mentioned, since that's the cheapest solution to try. Step up to the stylus options only if you find that's not working for you, or you want more control.


How can I install Boot Camp drivers in Windows on an external SSD disk?

Question: I am going to install Windows 10 on an external SSD disk, so I will need the Boot Camp drivers. How can I install the drivers manually?
Comment: see http://apple.stackexchange.com/questions/113297/bypassing-boot-camp-to-install-windows-using-a-non-standard-partition-scheme?rq=1
Answer: Open Bootcamp Assistant (In the Applications -> Utilities folder), then on the opening screen, click the 'Action' menu, then select 'Download Windows Support Software'.  You'll be prompted to select a location to save the downloaded files.  You can then put them onto a USB flash drive, restart into Windows and run the installer.
There are more details on the Apple Support website, here


What books, journals, and electronic resources are most valuable for expanding knowledge of GIS?

Question: What books, journals, and/or electronic resources have you found most valuable for expanding your knowledge in the GIS field, and why?
Answer:
This question has been converted to Community Wiki and wiki locked
because it is an example of a question that seeks a list of answers
and appears to be popular enough to protect it from closure.  It
should be treated as a special case and should not be viewed as the
type of question that is encouraged on this, or any Stack Exchange
site, but if you wish to contribute more content to it then feel free
to do so by editing this answer.

Not entirely a GIS Book but very helpful in many map design problems is Tufte's The Visual Display of Quantitative Information

PostGIS In Action by Regina Obe and Leo Hsu   http://www.manning.com/obe/

An excellent tutorial and resource on spatial databases in general and PostGIS in particular.  The book is currently available through Manning's Early Access Program in .pdf format, the paper version will be out relatively soon.

Geospatial Analysis: A Comprehensive Guide to Principles, Techniques, and Software Tools
Smith, Goodchild, Longley 2007
Entire text is online: http://www.spatialanalysisonline.com/

A solid guide to how geospatial analysis work, particularly with respect to GIS. The book emphasizes conceptual workflows, but still provides the basic math. I found the math quite helpful for creating my own code and also getting an understanding of what's happening under the hood in contemporary GIS.

Computational Geometry: Algorithms and Applications

The best computational geometry book. Very good at explaining (with illustrations) the various algorithms and concepts often used in GIS, such as triangulation, indexing, calculating intersection, shortest paths etc.

Map Projections: A Working Manual
(PDF, 380pages) by John P. Snyder
Answer: Here's my "recent" favourites, both cartography-related:

Designing Better Maps: A Guide for GIS Users by Cynthia Brewer

Making Maps: A Visual Guide to Map Design for GIS by John Krygier and Denis Wood

Unfortunately, and this is kind of sad, I have to admit that I haven't read a single GIS book in years.
The basic principles and practices of GIS haven't changed more than incrementally in the last half-decade, and the cool new technologies--commercial mapping APIs, KML, REST, location-based games and services, etc--have all been advancing at a frenetic pace since 2005 (note the publication date of the two books above)
If new technology matters to you (and it should) and you think you can rely on books, you may as well give up and go home.  To survive in this environment, you need to be adept with blogs and online documentation, and be willing to experiment.
Answer: Cartographic Relief Presentation by Eduard Imhof is the single best book I've read on cartography to date. Before ESRI Press republished the book in 2007 the only way to get was through inter-library loan via the University networks, and wait a number of months. It's still worth reading the original 1965 (Swiss/German) or 1982 (English) edition if you can as the reprint moves all the colour plates to the back of the book, and there is (an unavoidable) shift in colours and line detail. Cartographic Relief Presentation is more than forty years old, and still relevant. There's even an arcgis tool and photoshop method modelled after his Swiss Style Shaded Relief.

There are a hundred quotes I could pull out, but this is the one which strikes me today: "it is a mistake to believe the quality of a map depends primarily on the expenditure of money, time and labor. ...more decisive are the capability, experience, and expertise of the mapmaker. The expert always uses the simplest approach. ... He can show with a few lines what an unskilled worker would require many lines to depict. ...high density of information with poor selection is less efficient than a map with less content but good selection.

Section of school wall map of the Canton of Zurich, 1:50 000. 1934 (see exhibit)
Answer: I'm biased towards transportation, but here a few books (mostly reference type) I cannot live without:

Designing Geodatabases (ESRI)

GIS for Transportation

Field related: NCHRP Travel Demand Modeling (report 365)
Field related: Transit Quality of Service Manual - TCRP 100 Note there is an outdated rural version of this that I DO NOT recommend
Field related: Forecasting Demographics
Answer: Burrough and McDonnell's Principles of Geographic Information Systems is also a good one.  It provides you with most of the basic and higher level GIS concepts.  It is software agnostic which means you can very much apply the principles in any tool you use.
Answer: Desktop GIS: Mapping the Planet with Open Source Tools by Gary Sherman.

It's the first book I give out to folks when they're looking to learn a little about GIS and open source.
Answer: At the University of Tennessee Knoxville I took Quantitative Methods in Geography (as part of my undergraduate degree), and the text we used in the class was Elementary Statistics for Geographers 3rd Edition. I kept this book and reference to it frequently. It provides very thorough explanations of introductory statistics (descriptive and inferential statistics) with a focus on geography. The last two sections focus on spatial and temporal statistics.
Answer: The book "PostGIS in Action" was just finalized, printed and started shipping about a week ago.  At $50, it's not a bad price. It appears to be quite comprehensive @ 520 pages, and could be a valuable reference guide for anyone interested in PostGIS and its various components.  You can download the first chapter for free, which also includes a brief table of contents to give you an idea of what it covers.
Answer: GIS Tutor is a good starting point
http://www.gistutor.com/
specifically PostGIS - the wiki is a good starting point
http://trac.osgeo.org/postgis/wiki/UsersWikiMain
Answer: I really like Mapping Hacks by Schuyler Earle, Rich Gibson, and Jo Walsh.  http://www.amazon.com/Mapping-Hacks-Tools-Electronic-Cartography/dp/0596007035/

The book is divided up into 100 very creative 'hacks' that teach you about mapping, spatial data, opensource tools to work with data, and in the process inspire you to create or tackle the geospatial problems/hacks that you encounter in your work or personal life.  One of my favorites is 'Will the Kids Barf'.  It examines road sinuosity by comparing straight line distance with actual road distance to come up with an index to predict if the kids will get car sick.
This book It was published in 2005, so some of the references to APIs, etc. are a little dated, but the creativity, concepts, and inspiration are still very current.
Answer: Modeling Our World: The ESRI Guide to Geodatabase design (Michael Zeiler)

Great introduction into spatial data and geodatabases.
Otherwise, e.g. for code implementation, I rely more on blogs and forums.
Answer: I don't have room for the Klencke Atlas :(
http://mapperz.blogspot.com/2010/01/klencke-atlas-big-maps-in-big-book.html
Answer: Numerical Recipes, 3rd edition

Great book with algorithms with nice, clear explanations of the maths behind them and implementations, which are very robust and (usually) as fast as they get. Very good for matrices, fitting, statistics... The 3rd edition includes a chapter on computational geometry, which is especially useful in GIS.
Answer: This book on GIS Principles, which is part of an educational series form the University of Twente GIS department, gives very good explanation on the subject. People who are new to GIS can gather good basic information from it.

They also have a very nice book on the principles of remote sensing.

The best part of it is that both the Ebooks are available free online on their website here.
Answer: You also want to think about what your real interest is. Do you want to be a GIS developer versus a analyst in a particular field. You will see many places want to have a GIS person that has skill-sets in development as well as GIS.
But you can be a strong GIS user if you study Landscape Architecture, Civil Engineering, or even just starting as a CADD Analyst like me.
There are a lot of good generalist out there in the industry; who can just setup a basic spatial DB, slap a web-ui on a OpenLayers page consuming Bing/Google and be happy with that. Where you see the people who are most passionate about GIS is the ones who have it just as a tool in there box. Knowing your data domain is a great place to grow, to know what you want to build and support to be able to anticipate needs.
Core Hardware and Software are important in many areas, because if you can't see how you systems need to grow, then you won't be able to sustain the efforts.
What do you really want to do?
Answer: I'm using the AAG's GIS&T Body of Knowledge as a guideline for my studying efforts.
It doesnt contain theory, but indicates what's the next logical step and where I should look for it. It contains extensive references and explain the core learning units of GI and GIScience.
Answer: The Coming Singularity by Ray Kurzweil, has some food for thought, although I don't agree with a lot of what he says.  It won't take that much intelligence for a sentient computer network to realize the largest threat to his/her planet are the humans.
Perhaps GIS should be the fourth horseman of the apocalypse, next to Genetics, Nanotechnology and Robotics.
Update: OK, I guess I should suggest something more immediately useful:
Foundations of Multidimensional and Metric Data Structures by Hanan Samet is excellent if you want a clear explanation of algorithms.


Animations and complex graphics required?

Question: Hey guys I need some suggestions, I am developing a domain website on health care where   specialists surgeons doctors who treats specific health problem. Is having animations,sliders, gradients makes users(patients in this case)  difficult to use the site? Please suggest should I go with simple ui Or having all the above is ok for this.
Comment: What will these animations and complex graphics be used for? If it is for information display then simple is generally a safe starting point for conveying information.
Comment: Can you describe in more detail the purpose of the site? It's not clear what the role of "specialists surgeons doctors who treats specific health problem" is. It's not clear how patients will be using the site. It's not clear what the purpose of "animations,sliders, gradients" will be. Is the site intended to be an educational resource? An EMR with patient portal?
Answer: Using the animations design-wise and interaction wise makes the patients (users) to feel more confident and easy going, but using those must serve a purpose rather than just gimmicks then using those features gives more sense.


How do I turn off auto-accent in Windows 7?

Question: When I type in double e's like "teeth", the double e's are automatically replaced with ê. It's quite annoying as I can't type some double letters. How do I turn this off?
Comment: Are you using a localized version of Windows? If so, which?
Comment: Your d's seem to be off aswell.
Answer: In your Regional Settings, instead of an English | US keyboard, you have selected English | United States (International). Possibly, your default system language has also been changed from "US" to "United States / Intl"
Just change it back to US and it should be fine.
Comment: I didt had ê's, but instead apostrophe and tilde keys made a "flying accent" behaviour (e.g. apostrophe then a produced an á). Switching from US Intl to simple US fixed it.
Comment: Same problem on Windows 10. Described fix also works here.
Answer: Pressing ctrl-shift (using the left shift key) will toggle accents for some keyboard configurations.
Answer: If you need multi language support, it would be better to turn on Language Bar so you could switch input language on the fly on any program. If language bar is on your desktop already, you might want to try to switch it to EN to type in English without the auto corrections.
If you did not had language bar or just wanted to remove your non-English input support. Go to the "Region and Language" option in control panel, click on "Change keyboards and input methods". Then click the change keyboards button and from here you could add or remove the keyboards you want, then go to the Language Bar tab to configure where you want to show the language bar.
Comment: Also, check if you're using something like US international keyboard or similar.
Answer: It looks similar to using the Telex input method, which is a convention for writing Vietnamese.  How to type in vietnamese language using unikey ? please help? is what pointed me in this direction, but I don't know see that is a built in option of Windows 7.  I found Adding Asian IMEs (Chinese and Japanese) for Windows 7 for Chinese or Japanese IMEs, but no mention of Vietnamese in that article.  Follow the steps in that article and see if your keyboard is set to something other that English US.
Answer: I've checked all around MS's official help and knowledge bases and it doesn't seem like this is anything that Windows has built in.
The double typing of the same letter to make the accented letter leads me to believe that it's some sort of third party software.  It looks a lot like VPSKeys.
Check in your "Programs and Features" in Control Panel to make sure there's nothing there that you don't recognize.
Answer: This could be an AutoCorrect setting if you're using Microsoft Word or similar.
To check this, go into the relevant settings in Word; in Word 2007 you get to this by clicking the big menu button, selecting Word Options, then Proofing, then AutoCorrect options.
Have a look in there to see if someone has set ee to AutoCorrect to ê.


Homework integrals

Question: I suggest to filter them somehow. For example, who asks about integrals it would be obligatory to say  "I used computer algebra xyz, but it was unable to determine it, see the link here". Maybe, not the best method, but in many cases they forget(?) to tag with homework and check by computer. There are a lot of free possibilities, some of them is online on a web page.
Another suggestion is, if someone gives answer for a homework, to maximize the  reachable scores.
At least for me, it is strange that someone receives 55 votes for an answer to a trivial (sorry) question, while answering a "difficult" question he/she obtains 5 or 8 votes. One solution would be the "weighting". For example if the tag is "undergrad" then one vote implied two reputation, "grad" implied three reputation, or something similar. However it can happen that I don't know well the system, if this is the case, then sorry for me.
Comment: Not only for integrals, but generally it is true that simpler/faster answers receive many more votes than do deeper ones. This is probably because they are comprehensible to a larger segment of the community. Even if you browse the answers of some of our most knowledgeable users you will see that their highest voted answers are rarely their best (and, alas, some of their best answers received very few votes). Votes are not a good measure of any particular feature (except perhaps speed of answering).
Comment: Votes are a measure of the number of people who read your answer, thought they understood your answer and thought that it was correct, useful and/or amusing. They are not a measure of the amount of work or knowledge that went into the answer. While I agree that it can be annoying at times, I really think that overall, it works pretty well. It's not as if everyone is interested in answering trivial questions, so it is fine to reward it, too.
Comment: vesszabo, if you look down the right side of this page you will see, under the heading "Related", a long list of previous meta questions, many of them discussing the handling of homework questions. Perhaps reading through some or all of those earlier discussions will give you some idea of where the community stands, or doesn't stand, on the issues/suggestions you have raised.
Comment: @BillDubuque What is the policy about homework question in which there is no any effort, only the question? If the answer is they are well-come, then all-right, I accept it.
Comment: @BillDubuque I want to accept your comment as an answer, if it is possible.
Answer: That's just the way it is.

For many problems, it is impossible to know the difficulty until after you have done it.  Take Fermat's Last Theorem.  He assumed it was pretty straightforward.  Many problems in number theory are similar.
For just about any problem, it's impossible to give a difficulty level without ambiguity.
Even if the difficulty of every problem could be discovered, without ambiguity, it would take an enormous amount of time and resources to figure out the correct difficulty for each one.  Who wants to spend their time doing that?
Comment: 1. I would like to control only those questions where the origin is definitely homework. I suppose in this forum a lot of people knows the topics of undergraduate courses. I chose the integrals, because in this case what I suggested is definite and well-defined :-) In fact, in some cases in the webpage there are some details, not only the answer. May I give the url here? If you read the comments you will find that the first comment is often "What you tried, do you have any idea?, etc." I want to avoid to handle this forum as a homework aid. Such forums  already exist.
Answer: There's nothing wrong with a boilerplate link to, say, Wolfram Alpha, for questions that really are just interested in the result of an integral.
But this is not what homework questions are like because people need to show the steps or need to understand how to solve it.
It's fine if you do not want to answer homework questions at all, but pointing to the naked result from computer algebra is certainly not an answer to the question in that case.
Comment: I agree with you. I suggest Wolfram Alpha, because (maybe I'm too optimist) only the naked result could give idea to the solution. So it would be "step 0" before asking :-)
Answer: I thank for Gerry Myerson who encouraged me to browse the long list of related questions. Finally I could find two questions (discussions) which I think give satisfactory answers. A Consolidated Homework Policy and How do we enforce the homework policy?. I would like to quote from the last "I thought we had agreed not to give complete solutions to homework problems, but apparently some people didn't get the message. If this is not explicitly in the FAQ, it should be. Once that happens, how do we make existing math.SE users aware that this policy exists, and what is a reasonable way to enforce it?"
Before posting my discussion I checked the FAQ. I understand that for (very) active users reading almost the same questions can be annoying. I don't want this, so ask moderators to write an "official" policy in the FAQ. Thanks.
Comment: There is no official policy and quoting what a single person wrote in 2010, when M.SE was very young, is not going to change that. Some people hold very different views. See for example the gighest voted answer [here](http://meta.math.stackexchange.com/questions/1652/what-do-we-do-with-users-who-post-numerous-unlabeled-homework-questions/1661#1661).
Comment: @MichaelGreinecker I have _no_ (sorry, but probably my English is poor and misunderstand me) problem with homework in principle. My problem is mainly the "style" of some question. "Solve this equation", "Prove this and this". The questioner want to obtain a solution without any effort. Instead of saying give me only hint or I tried to solve it with this idea but I got stuck.
Of course, there are exception. Thanks for the link, I read it.
Comment: But then we should add guidelines for *asking* homework questions in the FAQ, not for *answering* them.
Comment: @MichaelGreinecker Yes indeed.

Homework integrals