Why is WPA Enterprise more secure than WPA2?

Question: In personal mode WPA2 is more secure than WPA. However, I have read that WPA Enterprise provides stronger security than WPA2 and I am unsure exactly how this is achieved.
Comment: Where exactly did you read this?  There is no doubt `WPA2` is more secure then `WPA`.  I would argue that `WPA Enterprise` is an entirely different authentication model then `WPA`
Comment: You don't have to argue, it is.  WPA2 Personal uses Preshared Keys.  That means you have to know the key and it can be shared amongst users.  With enterprise, you have to have an account on a back end RADIUS server.  This means that you have to have a username and password to gain access to the Wireless network.
Answer: All earlier answers are missing a very important step and its implication and are misunderstanding EAP.
WPA2-PSK (aka WPA2 Personal) basically does the same thing as WPA2-Enterprise from the clients perspective: The client associates to the access point, authenticates to the access point using the pre-shared key and access point creates a 256bit PMK (pairwise master key) from the SSID and the pre-shared key (PSK). This PMK is then used to encrypt data traffic using CCMP/AES or TKIP.
The important thing to note here is that all clients will always encrypt their data with the same PMK, all the time. So it's easy to gather a lot of data encrypted with the same PMK. Should someone break the PMK, they could decrypt all data encrypted with that key, past/recorded and future/realtime.
WPA2-Enterprise is only a little bit different behind the scenes, but the security implications are severe: The client associates to the access point, authenticates to the access point, who passes this on to a backend RADIUS server (using EAP, but that's not important here, so more on that at the end). When the RADIUS server has authenticated the client, it gives the access point an OK, plus a RANDOM 256bit pairwise master key (PMK) to encrypt data traffic for the current session only.
Well, that's quite a difference. Instead of each client using the same PMK all the time (the seed of which is known plaintext, because the SSID is used as seed!), now every client uses a different PMK, it changes every session/association and the seed is random and unknown. Not only that, but this PMK will be 256bit real entropy (not a hash from a usually much smaller password containing words), so dictionary attacks are useless.
Should someone break a particular PMK, they only get access to one session of one client. Also (if the right EAP method is used) they don't get access to the users credentials, since they where individually encrypted. That's a whole lot more secure.
Also remember that this PMK is 256bit AES, this is currently "uncrackable" (128bit is considered safe for the moment, but not for long). The fact that the PMK of WPA2-PSK (also 256bit) can be cracked comes from the usually weak passwords (dictionary attack), the known seed (SSID) and the fact that all clients use the same PMK all the time, so a lot of ciphertext of known plaintext can be captured.
So, then a little about the Extensible Authentication Protocol (EAP). This is often understood as a security protocol in itself, but it isn't. It's basically a standard for passing messages from a client wanting to authenticate and a server that authenticates. EAP itself has no security features, it just specifies how the client speaks with the RADIUS server.
Now, you can encapsulate these EAP messages in a secure tunnel. Like HTTP (an insecure messaging protocol) goes over a secure layer, SSL/TLS to yield a secure connection to a webserver. Someone said in another answer that there are over 100 different EAP "methods", some very insecure. This is true, because EAP is old there were encryption standards implemented that are sub-standard today.
But in practice, if you need to support recent Apple or Android machines/devices and Windows machines, there's only two options, because others are simply not supported: Protected EAP (PEAP) and TLS-EAP (well, I lied: really there are a few more, but they are basically identical to TLS-EAP in functionality and security).
PEAP is just like a https server, a secure TLS tunnel is setup between the client and the RADIUS server (protecting the entire wireless and wired path between them), the server presents a certificate to the client (in companies often signed by their own CA) and a secure channel is setup on the basis of this certificate.
If the client has the CA as trusted in their certificate store it sends its username and password to the RADIUS server. If the CA isn't trusted, the user gets a warning about the certificate as with a https site that has something wrong with its certificate. The credentials are usually protected with the (old and now weak) MSCHAPv2 protocol, but that doesn't matter, since everything is already protected by 256bit TLS. The MSCHAPv2 protocol talks with the RADIUS server using EAP.
An obvious weak point is that you could setup a false access point, present a false certificate of which you have the private key, and hope that some idiot user gets a warning about an untrusted certificate and just clicks "trust" (and that option is not disabled by an administrator). Then you could maybe capture the client's weakly encrypted credentials that are fairly easy to crack (I'm not sure about this, as I know MSCHAPv2 can be easily cracked if you have the WHOLE exchange, in this case you'd only have the client side as you couldn't send a valid nonce to the client to complete the exchange, as you don't have the real hash of the users password).
While this may get you access to the real network with a lot of work (and I doubt it, but if you must know, look into MSCHAPv2 at http://www.revolutionwifi.net/revolutionwifi/2012/07/is-wpa2-security-broken-due-to-defcon.html), it wouldn't get you access to any other wireless data, as they are encrypted with a different PMK.
But for companies this may still be a problem. Enter TLS-EAP. TLS-EAP is basically the same as PEAP with the notable difference that the client also has a certificate. So the server presents its certificate to the client which must be trusted by the client (because the CA is in the trusted store, or an idiot clicked "trust"), but the client also has to present a certificate to the server. This can be a certificate that's been placed in the cert store when the device/workstation was provisioned, but it could also be from a smartcard etc. The server has to trust this client certificate, or you won't even get the chance to present credentials.
As many of you may know, such 2-way authentication can also be done for HTTP over TLS, but this is not often seen outside corporate settings. In that case, too, you can't access the website unless you first show a certificate that's trusted by the server.
So now the fake access point isn't very useful anymore. You may get the weakly encrypted credentials if the idiot clicks "trust" and you then blindly accept any client certificate, but since you don't have the private key of the client certificate you don't get access to the wireless network, nor do you get encrypted wireless data of this or other clients still courtesy of the random session-based PMK. You may get access to some intranet with the credentials, but if they went to the trouble to setup a CA for wireless they probably require a client cert for that too.
In corporations it's common to have such a client cert on a smart card, which employees then need to access all resources: logging in, network resources, mail using smtps, imaps, pop3s, intranets using https, anything that uses TLS can be setup to require a client certificate. Usually it's as simple as putting it in the keyboard and enter a PIN, then windows will present it when demanded by a trusted server running TLS.
So, I hope this clarifies a bit. The scale goes:
"basically unsecured" (WEP)
"crackable with some effort" (WPA2-PSK)
"partly social-engineerable" (WPA2-Enterprise w/PEAP)
"currently secure" (WPA2-Enterprise w/TLS-EAP and similar)
There are ways to make WPA2-PSK somewhat more secure, in that it would take months to crack it instead of minutes (pre-computed rainbow tables) or hours (dictionary attack): Set your SSID to a random string of the maximum length (64 I think), since it's used as the seed for the PMK, and use a random pre-shared key (PSK) of the maximum length. If you then change the key monthly you can be reasonably sure that nobody has a current PMK or had/has access to your network.
Though you can't get rid of the fact that someone could have stored a months worth of data of all clients and reads that once they do get the PMK of that month (which can be done, as it's not a key with 256bit real entropy as you're broadcasting the seed used).
Another drawback is that you will have a highly unique SSID, one that your wireless devices will broadcast wherever you go. If someone has your unique SSID of your home network it's a piece of cake to look up your SSID at https://wigle.net/ and find out where you live. So you're basically walking around with your phone/tablet/laptop announcing where you live...
If you're privacy conscious it's maybe a good middle way to keep your SSID set to one that's common, but not in the top 30 or so (that way it's unlikely to have rainbow tables for it available online) and use a random PSK of maximum length. You lose some entropy though.
If you want the same security as wired, use WPA2-Enterprise with TLS-EAP. (Well, for now... There's nothing stopping someone from capturing and storing all the data they want and decrypt it all in 20 years when we can all rent time on a quantum computer and factor all keys in minutes.
The NSA is said to have built a datacenter to do just that, store anything encrypted they encounter until they can crack it, so that problem also affects everything on wires if it crosses the internet. If something needs to be secure for all time, use a random one-time pad that you exchange out-of-band :)
All that said, while I'm paranoid and want the best security and thus spend two days making WPA2-Enterprise/TLS-EAP work, this is probably out of reach (and overkill) for most home users. If you don't already have a domain controller or some other directory service on your network, experience with RADIUS and have all expensive pro wifi gear that an enterprise would use then you most likely won't get it to work. You'd be better off just setting up an always-on VPN and run that over your wifi, that gives you all the security and none of the fun debugging EAP.
PS. For the sake of simplicity I also left out the fact that the communication between the access point and the RADIUS server is also encrypted by a pre-shared key (called the "shared secret"). Afaik this encryption isn't any good today (uses MD5 which is basically broken) but since you put TLS over it anyway that doesn't matter. You can use a decent key size (something between 64-128 chars = 512-1024bits depending on the implementation). I always set the largest secret possible, it can't hurt.
Comment: The obvious weak point you present is similar to the weak point of online shopping - some idiot user might provide his credit card details without seeing a green lock near the URL or when seen a red broken one. But I wonder about another thing. What if the attacker buys a TLS certificate for a domain he owns and sets up a rouge CA and presents this certificate for the rogue RADIUS server he set up? Sounds like this shouldn't work, but I don't see anything in your description preventing this, and unlike web browsing where you even a valid certificate for www.g00gle.com might make you suspect...
Comment: you don't see the URL of the RADIUS server you're talking to (at least not in Windows, iOS and Android).
Comment: The CA would have to match the client's cert, so that wouldn't work.
Comment: I wasn't aware of any client certificates in play in PEAP-MS-CHAPv2. I even see a TechNet article saying "PEAP-MS-CHAP v2 an EAP type that is easier to deploy than Extensible Authentication Protocol with Transport Level Security (EAP-TLS) or PEAP-TLS because user authentication is accomplished by using password-base credentials (user name and password) instead of digital certificates or smart cards." What client certificate are you talking about?
Comment: conio: Correct, in PEAP clients don't have certificates (only the server does, but username/password (which allows for capturing the creds when a MITM AP is setup). I said EAP-TLS added client certificates to the mix to prevent this.
Comment: conio: I see I never answered your question directly for PEAP. Yes, you could buy a certificate for a random host.domain.tld, and then setup a rogue RADIUS server that identifies using that certificate.

If a user were to manually select your rogue SSID, he wouldn't get a cert warning and would probably input his credentials.

Corporations usually use EAP-TLS to prevent this, but if they do use PEAP, they prevent this by pushing wireless profiles to their clients (for instance via Group Policy for Windows) that specify exactly which CA in the trusted CA list will be accepted for the SSID.
Answer: The PSK variants of WPA and WPA2 uses a 256-bit key derived from a password for authentication.
The Enterprise variants of WPA and WPA2, also known as 802.1x uses a RADIUS server for authentication purposes. Authentication is achieved using variants of the EAP protocol. This is a more complex but more secure setup.
The key difference between WPA and WPA2 is the encryption protocol used. WPA uses the TKIP protocol whilst WPA2 introduces suport for the CCMP protocol.
Comment: This answer isn't very informative. How is EAP "more secure"? Does it protect against more threats, or provide greater strength against brute force? What difference does TKIP vs CCMP make?
Comment: WPA2 Personal uses one key.  Everyone with the key knows how to decrypt your computer's traffic.  The WiFi segment is one big broadcast network.  Wired networks will generally keep your computer's traffic private as long as the switches are secured.  Your traffic goes along the wire and is handed to its destination only.  Even someone plugged in to another jack can't see the traffic unless the switch is not set up correctly.

WPA Enterprise gives every user their own private session key. This removes the broadcast effect.  Now the WiFi network behaves like everyone has their own wire.
Comment: EAP is more secure because the keying material is unique and created between client and AP rather than generated based on a known value (PSK).  In personal mode, the keying material is generated based off a known value (the PSK) and anyone with that known value is able to capture the key negotiation and therefore decrypt all the resulting traffic.  Additionally, with EAP, the keying material can be changed during the session, making it more secure.
Comment: @Unw0und No, EAP is an *authentication* protocol while TKIP and CCMP is an *encryption* protocol.
Comment: So when using a RADIUS server, an EAP protocol will be used instead of TKIP or CCMP?
Comment: I think I could make this clarification simpler again. Put simply every user has their own "password" (key) instead of using a shared one that everyone is using.
Answer: Say you have 10 users.
In PSK mode all 10 users are using the same passphrase to generate the same key. Therefore, the likelyhood of capturing traffic and analyzing it to find the key is higher with so much traffic, and that key will be good until all 10 users agree to change the passphrase (and therefore the key)
If those same 10 users use their own username and password to log in to an enterprise WiFi network, each user authenticates to the RADIUS server, which then generates a key for their session and hands that to the AP to use with their client.
Therefore the traffic with the same key is only one users traffic, so it is 1/10th as much data to work with, and the key will change the next time the user logs in. The password the user authenticates with may stay the same, but the key that that generates is unique to each session. Combined with good password habits, WPA enterprise is better. Also, individual users access can be revoked at any time without affecting other users.
Comment: "individual users access can be revoked at any time without affecting other users" I did't know that. Do you mean they can be revoked in real time? If that is the case, what would I user see? Just a disconnection and when tries to connect with his password an error message? If my RADIUS server is connected to a SQL database and I remove a user, will this user be removed in real time? Thanks a lot for clarification.
Answer: WPA2 is more secure than WPA as explained by Terry. You just need to understand the difference between personal (pre shared key) and enterprise versions of both the protocols.
The personal version is where all the users share a secret password that is configured in the access point. In the enterprise version there is a central authentication server and all the users have different sets of credentials that they use in order to access WiFi. So basically there is no single shared password.
Answer: The Enterprise (RADIUS/EAP/802.1X) mode of WPA or WPA2 provides the following benefits over using the Personal (Pre-Shared Key or PSK) mode of WPA or WPA2:

Overall it complicates the process of "hacking" the wireless.
Each user can be assigned a unique login credential (username or
password, security certificates, or smartcard) for the Wi-Fi, instead
of a single global password for all.
User-to-user snooping is
prevented, unlike with the Personal mode where connected users can
capture each others traffic, including passwords and session
hijacking.
Enables additional controls (authorizations) such as
Login-Time, allowing you to define the exact days and times users can
login, Called-Station-ID to specify which access points they can
connect through, and Calling-Station-ID to specify which client
devices they can connect from.

Though the Enterprise mode requires the use of a RADIUS server, there are hosted or cloud services out there.
Answer: There are lots of terms being mixed here.
WPA2 is an encryption scheme. The enterprise vs. personal refer to the authentication scheme but not the encryption scheme. The authentication scheme basically verifies your identity to the network owner before you are allowed to send encrypted data.
From an Encryption view point, WPA2-Enterprise and WPA2-Personal have the same 256-bit Encryption algorithm (I believe it is called AES-CCMP). So the difference between them lies in the authentication scheme.
Now, EAP and 802.1x can be thought of as one and the same protocol. They define signalling methods to allow the authentication to happen between (now this is important): the client, the access point and a third entity called the registrar which store the authentication credentials. EAP is used in Personal and Enterprise BUT the key difference is the location and the type of credentials that the registrar requires from the client before agreeing to grant it access to the network. In PERSONAL, it is common for the registrar to reside on the same physical entity as the access point (i.e. wireless router) and the authentication method is usually based on a pre-shared key (e.g. the ones that is pre-programmed with the router when you buy it or the one that the owner of the router would give you when you come to his place).  Changing that pre-shared key requires a global update whenever any of the old clients want to access the network again (i.e. you have to tell them that you changed the key and the key is XYZ). In ENTERPRISE the registrar is usually a separate entity that runs a protocol called RADIUS. It provides more manageability (e.g. pre-shared key for every user, the admin can revoke a key for a particular user, etc..).
Now something really important here (from a security view point), the encryption key (i.e. not the authentication) is derived from the pre-shared key, thus it is easier for someone who has the pre-shared authentication KEY in PERSONAL to recreate the encryption key and thus decrypt the data. In addition, PERSONAL allows for other methods to further simplify the issue of entering pre-shared key such as the push-button (push-button on routher and device at the same time and everything happens seamlessly). This method compromised the security if someone was listening on the channel and shown to be easily breakable (now the term easily is relative!!). Such method is not available in Enterprise. Therefore in summary yes Enterprise is more secure but is also more suited for someone who has the knowledge and resources to install and administer a RADIUS server. Good security is achievable over PERSONAL by choosing a strong pre-shared key and disabling the push-button method on the wireless router.
Answer: I am assuming when you ask whether WPA-Enterprise is more secure than WPA2, you mean WPA2-PSK (aka WPA-Personal). This is a bit like asking are vegetables healthier than an apple. WPA-Enterprise covers a spectrum of authentication methods (about 100 of them all under the extensible authentication protocol), some very strong, some very weak. WPA2-PSK is a specific means of authentication relying on 256-bit AES. The only feasible way to break WPA2-PSK is to capture the handshake packets and then run a dictionary attack against it. It doesn't matter how many handshakes you capture (i.e. whether it is one client or 100 that connect using the password). It's not like WEP. Hence if you have a good password (e.g. 20 characters and fairly random), it will be pretty darn secure. By comparison, WPA-Enterprise can use schemes that are weak, such as LEAP, which uses the MS-CHAPv2 handshakes. These are mere 56-bit DES encryption, easily crackable via brute force regardless of password complexity. Now, among the 100 EAP options, which range in cost and complexity, you can find something that would approximate the strength of a WPA2-PSK with a random 20 character password. But if that is your only goal, you are missing the point of WPA Enterprise. The main driver for WPA Enterprise is the granular control you can have over who or what connects to your network. WPA Enterprise can create credentials for each device and user. If you all of a sudden you need to cut out one user or a category of devices (e.g. mobile phones) you can do that. Of course in setting it up, if you botch the implementation by using something like LEAP, you just let those people/things that you turn away at the front door in through the back door. Unless you have the budget, resources, and need for WPA Enterprise, WPA2-PSK will be easier, cheaper and likely more secure. The three caveats: A sufficiently complex password that you change occasionally, you have no need for user or device specific control, and most important - disable that utterly stupid Wifi Protected Access (WPS) that comes on some access points.
Answer: It's not. WPA-Enterprise and WPA-PSK will ultimately create a PTK key to be used in the TKIP algorithm, because it is WPA, therefore less secure than WPA2, whether it is WPA2-PSK or WPA2-Enterprise.
Enterprise just offers encryption for the 4-way handshake, such as PEAP, or use of certificates, so WPA-Enterprise is arguably more secure than WPA-PSK but will ultimately meet the same fate. Enterprise also offers higher granularity over who accesses the network by using user accounts or per-user preshared key information from RADIUS or ultimately Active Directory for material to be used in CCMP key generation.


What is considered part of the beard?

Question: What is considered part of the beard, and what hair on the face is not, and therefore permissible to shave or trim?
Answer: The majority of classical Arabic linguistic scholars consider the lihya (from lahi) to be the hair on the chin, plus on the entire jawbone. A minority say chin plus front teeth only. The vast majority also include hair on the cheekbone as well, while saying that the hair below the eyes and on the throat is not part of the lihya. There is further a difference of opinion on the hair below the chin and above the throat.
Reference: The above is taken from a class on fiqh of clothing taught by Dr. Yasir Qadhi. Other answers directly referencing books of fiqh are preferred - I will delete my answer when those show up.
Answer: Majority of the Scholars understand beard from the linguistic definition of "lihyah" which means the hair that comes from the chin and cheeks.
Ibn Manzoor said quoting from Ibn Sayyidih:

Lihyah (beard) includes the hair that grows on the cheeks and the
  chin. Lisaan al-'Arab, 15/243

Similarly it also says in Fath al-Baari, p. 35; vol. 10, al-Salafiyyah edition:

It is a name for that which grows on the cheeks and chin.

Shaykh Muhammad ibn Saalih al-'Uthaymeen (may Allaah have mercy on him) was asked about what is meant by the beard. He replied:

The extent of the beard is from the cheekbones, level with the channel
  of the ears, until the bottom of the face. It includes the hair that
  grows on the cheeks.
It says in al-Qaamoos al-Muheet (p. 387): Lihyah (beard) is the hair
  of the cheeks and chin.
Based on this, the one who says that the hair that grows on the cheeks
  is not part of the beard must bring proof of that.

Majmoo' Fataawa Ibn 'Uthaymeen, 11/question no. 49
He (may Allaah have mercy on him) was also asked: Are the cheeks part of the beard?
He replied:

Yes, the cheeks are part of the beard, because this is what is implied
  by the language in which sharee'ah came. Allaah says (interpretation
  of the meaning):

"Verily, We have sent it down as an Arabic Qur'aan in order that you
    may understand"[Yoosuf 12:2]
"He it is Who sent among the unlettered ones a Messenger (Muhammad)
    from among themselves, reciting to them His Verses, purifying them
    (from the filth of disbelief and polytheism), and teaching them the
    Book (this Qur'aan, Islamic laws and Islamic jurisprudence) and
    Al‑Hikmah (As‑Sunnah)" [al-Jumu'ah 62:2]

Hence it is known that the meanings brought in the Qur'aan and Sunnah
  are the meanings indicated by the Arabic language, but if there is a
  particular  shar'i meaning it should be interpreted in that manner.
  For example, salaah in Arabic means supplication (as in du'aa'), but
  in shar'i terminology it refers to the specific, well known act of
  worship (prayer), so when it is mentioned in the Qur'aan and Sunnah,
  it is to be understood in the shar'i sense, unless there is any
  indication to the contrary.

As for the hair that grows on the neck, it is not part of the beard.
Imam Ahmad (may Allaah have mercy on him) stated that there is nothing wrong with removing hair that is beneath the pharynx, as it says in al-Insaaf (1/250), because it is not part of the beard.
Shaykh Muhammad al-Safareeni said:

The reliable point of view, as it says in al-Iqnaa' and elsewhere, is
  that it is not makrooh to remove hair that is beneath the pharynx.

Ghidha' al-Albaab Sharh Manzoomat al-Adaab, 1/433
Source and further reading: Definition of the beard and ruling on shaving the hair that grows on the neck,
What is the hair that it is permissible to remove and the hair that it is not permissible to remove?

What is considered part of the beard?


Are Chinese people aware of the difficulty of their writing system?

Question: How is the difficulty about the Chinese writing system viewed by native speakers? Is it a view they share with other learners around the world or do they see it the same way other speakers see their own language?
Comment: **NOTE:** I tried to fix your question so that it had a more constructive wording. If you want to claim that it's the "worst" writing system, at least you should give context as to what you mean by "worst" and how. I think it's not in any case, but at least you'd give something to answer to with arguments. Just saying it's the worst equals to it just being a rant.
Comment: To other readers: it's probably best to flag this question as offensive, rather than putting in a VTC or editing, since it's clearly of ill-intent.
Comment: @Maroon Personally, I find it more productive to turn the question into something meaningful. The offensive part then goes away.
Comment: @Maroon The question has been rephrased; it should no longer be offensive.
Comment: Writing systems should be hard enough to stay off limits for evil, stupid racists, such as the OP. Now, as @Maroon saw, the original  question is clearly of evil intent. It is a shame to reword it, thus enticing Chinese people to answer to it.
Comment: Yes, the current question is not offensive.
Answer: What would be the criteria for a judging writing system as "good" or "bad"? How well it matches the pronunciation? How easy it is to learn?
The Chinese are aware of the difficulty of their writing system - i.e. that it takes a long time to learn - and proposals to reform it go back to at least the late 19th century. Some people supported very radical reforms. For example, the Chinese author Lu Xun (1881-1936) supposedly said, "If Chinese characters are not eradicated, China will perish" (漢字不滅,中國必亡 / 汉字不灭,中国必亡: Hànzì bù miè, Zhōngguó bì wáng).
One such proposal that replaced Chinese characters with Latin script, was Latinxua Sin Wenz. (Note, however, that not every romanization system was meant as an effort to replace Chinese characters with the Latin script.)
Also around the beginning of the 20th century, Wang Zhao (1859-1933) came up with a system inspired by Japanese katakana, but the Chinese government banned the system.
For other examples, see, for example, John DeFrancis' book
The Chinese Language: Fact and Fantasy (University of Hawai'i Press, 1984)  and Jerry Norman's book Chinese (Cambridge University Press, 1988).
By the way, some other writing systems are also difficult:

The hardest language to spell (Tibetan, according to NativLang on YouTube)
World's Most Complicated Writing System (Thai, according to XidNaf on
YouTube)
The Hardest Writing System! - an animated rant about learning
Japanese (by NativLang on YouTube)
Comment: Although In the modern age English has to be a lot more illogical than Chinese (characters). I've never had a problem typing Chinese but I often can't figure out how To spell English.
Answer: As a Chinese native speaker, at least I didn't realize this problem until you ask. Well, we have Pinyin which is more like phonetic symbol to help us input Chinese characters into Computers. As for writing by hands, indeed, it is much more complicated than English.
However, this also made the variety of calligraphy of Chinese characters. Many masters are practicing how to write more beautiful characters through their whole lives. I have to admit that's difficult to learn. The fact is while you are judging it, it is used by the most people on this planet lol :)
Comment: Argumentum ad populum much? ;) My measure of a writing system being "good" is how fast I can write what I mean by hand. If it takes several second to write down just one syllable, then it's definitely not good :q  As for those calligraphy masters spent so much time of their lives on just writing those characters, that really means something :q  Imagine what other things they could have spent their lives on more productively if they could write fast ;)
Answer: I don't have good citations right this second,  but I'll look for some.
I can give a personal answer as someone in-country.
Do they think others must see it as difficult?
yes
They are very aware and proud of the written language likely being the hardest.  They don't expect foreigners to be able to learn it.
Everyone that goes through high school learns at least some English, and so has an idea of alphabetic language.  They understand the difference, and understand that Chinese is one of the only non-alphabetic modern languages.   (are there any others?)
This uniqueness makes it difficult for all foreigners, and this is understood.
Do they feel like it is difficult?  I don't think they long for an easier way.  As their first language, I would have to guess it is as natural for them as anyone's first language.
But it would be good to find some research.
From a more objective standpoint about difficulty...
As far as using the language, once you know it --- if you count the number of strokes to write the same sentence in Chinese and English it's usually pretty close.
And that's if you write the Chinese characters the perfect, standard way.
Because Chinese is often more efficient than English in the number of words, a native writer of Chinese using a reasonable handwriting style - with an abbreviated number of strokes - is probably faster than someone writing in English.
So we could infer they don't have a problem.


transaction confirmation for ethereum

Question: Is there a transaction confirmation for ethereum like there is for bitcoin?
I sent 73 etherium to an exchange and they show only 64. How can I verify that they received all 73?
Answer: Yes https://etherscan.io/ is the blockchain explorer for Ethereum Blockchain.
It is basically a search engine that allows users to easily lookup, confirm and validate transactions that have taken place on the Ethereum Blockchain
Answer: Get the transaction hash from your wallet or node, and search for it on etherscan.io.
You can see the inputs and outputs of the transaction, and verify that the funds were transferred to their account.
This should be enough to get you the proof you need.

transaction confirmation for ethereum


From which work of Jean-Paul Sartre did he write "Freedom is what we do with what is done to us."?

Question: In which work did Jean-Paul Sartre write this quote?
Comment: This quote expresses the core of sartrian viewpoint, and while the words were almost surely said by Sartre later than in 1940s they are in no contradiction with his 40s ideas expressed in Being and Nothingness, absolutely. In 1946 play _Morts sans Sépulture_ (known as Men Without Shadows in english) the cited maxim is the dominant idea.
Answer: Maybe a "free" translation from: L'existentialisme est un humanisme (1946):

Et en voulant la liberté, nous découvrons qu'elle dépend entièrement de la liberté des autres, et que la liberté des autres dépend de la nôtre. Certes, la liberté comme définition de l'homme ne dépend pas d'autrui, mais dès qu'il y a engagement, je suis obligé de vouloir en même temps que ma liberté la liberté des autres, je ne puis prendre ma liberté pour but que si je prends également celle des autres pour but. En conséquence, lorsque, sur le plan d'authenticité totale, j'ai reconnu que l'homme est un être chez qui l'essence est précédée par l'existence, qu'il est un être libre qui ne peut, dans des circonstances diverses, que vouloir sa liberté, j'ai reconnu en même temps que je ne peux vouloir que la liberté des autres.

English translation:

And in thus willing freedom, we discover that it depends entirely upon the freedom of others and that the freedom of others depends upon our own. Obviously, freedom as the definition of a man does not depend upon others, but as soon as there is a commitment, I am obliged to will the liberty of others at the same time as my own. I cannot make liberty my aim unless I make that of others equally my aim. Consequently, when I recognise, as entirely authentic, that man is a being whose existence precedes his essence, and that he is a free being who cannot, in any circumstances, but will his freedom, at the same time I realize that I cannot not will the freedom of others.
Comment: I think that this quote is a bit away from the question since it is about 'my freedom and freedom of others' topic.
Answer: In Critique of Dialectical Reason, vol. 1, Sartre wrote (translation from the Russian translation into English is mine)

For us a man is characterized first of all by his surpass of the
  situation - by what he succeeds to do out of what they have done with him [or: made him into],
  even if he never recognizes himself in his objectivation.

[Objectivation in roles, statuses, opuses, relations, identities etc. - everything that return us to ourselves in alienated mode]
Also, internet says (I didn't check that) that in Situations IX he wrote

You can always make something out of what you've been made into

From which work of Jean-Paul Sartre did he write “Freedom is what we do with what is done to us.”?


Notify on desktop using HTML5 Notifications API

Question: It would be nice to see opt-in notifications of activity on my desktop using the HTML5 notifications api. Here is the current browser support (all browsers except Internet Explorer).
MDN Article
Comment: In the meantime, do check out [**StackApplet**](http://stackapps.com/questions/83/stackapplet-bringing-stack-exchange-notifications-to-your-desktop-1-6-alpha-f) for something very similar!
Comment: Btw, StackApplet is currently broken. :-(
Comment: It's worth mentioning they already do this in chat.
Answer: Yes ! I believe this would be a very useful feature to have. I could get inbox notifications even when the browser is minimized, and I would not have to switch tabs to check if I have a new message all the time. Obviously, this feature should be opt-in.
It could look like this:

I think this would be very useful !
Answer: There is an extension for Chrome and Firefox on StackApps that basically does this: Real-time desktop notifications for Stack Exchange inbox ( Chrome / Firefox )
I find it very useful.


Papers about backtesting option trading strategies

Question: I am looking for all kinds of research concerning option trading strategies. With that I mean papers that publish results on different option trading strategies properly backtested with real-world data.
Comment: funny how much a bounty can actually wake up people....
Comment: "real-world data" as opposed to... "fake data" ;) Interesting question though.
Comment: @JSmaga: Well, not artificially created pseudo-random simulation data but historic real option price data.
Answer: I did some digging and found the following papers - most of them offering quite a distinct perspective compared to classical option pricing theory!

Stock Options as Lotteries by Brian H. Boyer et al. (2011)
The Efficiency of the Buy-Write Strategy: Evidence from Australia by Tafadzwa Mugwagwa et al. (2010)

The following is my favorite: You could do some backtests on your own with freely available data (using the VXO as volatility information) and with any spreadsheet - easy and elegant:

How Students Can Backtest Madoff's Claims by Michael J. Stutzer (2009)
Loosening Your Collar: Alternative Implementations of QQQ Collars by Edward Szado et al. (2009)
A Study of Optimal Stock & Options Strategies by Mihir Dash et al. (2008)
Is There Money to Be Made Investing in Options? A Historical Perspective by James S. Doran et al. (2008)

EDIT:
I will update this answer from time to time when new interesting papers arive:

15 Years of the Russell 2000 Buy-Write by N. Kapadia and E. Szado (2011)

EDIT 2:
I just published a blog post where I replicate the abovementioned paper by Stutzer (2009):

Backtesting Options Strategies with R

In the post, I provide the fully documented R code for your own experiments. For details please consult the post.
Comment: There seems to be a more recent version of the paper "Madoff Mess Motivates" under the title "How students can backtest Madoff's Claims" which reads very nicely.

Edit: heres the link: http://leeds.colorado.edu/asset/burridge/backtestmadoffsclaims.pdf
Answer: Since I, too, have been very interested in this question, I will share some of my findings in the dual hope of encouraging comments on the papers and eliciting more activity on this question.

Ammann, Skovmand, and Verhofen (2008): Implied and Realized Volatility in the Cross-Section of Equity Options
Ang, Bali, and Cakici (2010): The Joint Cross Section of Stocks and Options
Bali and Murray (2011): Does Risk-Neutral Skewness Predict the Cross-Section of Equity Option Portfolio
Cao and Han (2011): Cross-Section of Option Returns and Stock Volatility
Constantinides, Jackwerth, and Savov (2011): The Puzzle of Index Option Returns
Deng (2008): Volatility Dispersion Trading
Driessen, Lin, and Hemert (2011): How the 52-Week High and Low Affect Option-Implied Volatilities and Stock Return Moments

Jones and Shemesh (2010): The Weekend Effect in Equity Option Returns
Answer: Option Traders Use (very) Sophisticated Heuristics, Never the Black–Scholes–Merton Formula
Stock Price Clustering on Option Expiration Dates
Option Returns and Volatility Mispricing
Comment: And the first one by the Black Swan himself is like reading hieroglyphics. Wow.
Comment: I think only the third one is relevant to the question
Comment: @vonjd: The third one (Goyal and Saretto (2007)) is probably one of the best references in this area, IMO.


What is the most important for league play? Also what is CS?

Question:
Possible Duplicate:
First thing to learn when beginning League of Legends

What is the most important thing you should do or practice if you want to become a league of legends, League player? As well what is CS exactly?
Comment: FYI, one question per post is preferred. Also, the subjective nature of the league question well likely illicit discussion answers and may also result in this question bring closed.
Answer: The most important things in League of legends to learn are

CS and last hitting - you minion score is generally what wins games, not going for risky champion kills also last hittign will prevent you from pushing you lane and getting ganked.
Positioning - which way you should enter the river or come into a team fight, you dont' want to pin yourself or separate yourself from your team when possible
Map awareness and control - It is VERY important to watch your mini map and have good ward coverage. People will not always all a MIA when their lane comes to gank you. While they should have, your over extention or needless death is still on your own head for not being aware wheere the other team is. Make sure you always keep an eye on your mini map and ward in all key positions to prevent ganks.
Answer: Just a small addition about CS to the other answers (which pretty much covered everything else) because I did not see this explicitly mentioned in any of them:
CS = Creep Score = the amount of minions you landed the killing blow on and thus got gold from = A very significant part of your income (unless you are a support).
This is also why mastering last hitting (letting ally creeps bring enemy creeps down to within 1 of your normal attacks from death and ONLY THEN attacking it for the kill credit) with a given champion will give you a significant advantage in lane: This way you maximize your income without pushing the fight deeper into enemy territory (as you would if you just keep auto attacking), thus leaving yourself vulnerable to a gank. Do not be afraid to use a spell to get a last hit when 2 minions drop low at the same time, it is usually well worth the extra CS.
I should probably mention that there are also times you want to keep autoattacking or even using your spells to push the wave.
For example: if you KNOW your lane opponent went back to buy and the wave is near the enemy tower, AND you have sufficient map vision to be relatively safe from ganks, you should clear the minion wave so that your minions hit the enemy tower. This way you deny your opponent the exp and gold from those minions and do some damage to his tower AND have the wave then push back to your side once the tower clears the creeps.
This can also be done if, (once again, ONLY if you have sufficient vision/position information on your enemies to be safe), your opponent's champion is miserable at last hitting at his tower (usually someone with bad autoattacks) and will lose a lot of CS to it and you have a champion that is good at clearing minion waves.
Just don't EVER overstay your welcome: feeding a minion wave to the enemy tower is NEVER worth a death.
Answer: I would learn how to be map aware, jungle routes, and ward placement. Note that warding and map awareness are two different things. Map awareness means you know an opponent goes mia (missing in action). This is important due to they might be heading to gank another lane or be heading to a map objective such as a jungle buff, baron, or dragon. Jungle routes in my opinion are the second most important. Knowing them as a jungler can give you an exp, gold, and gank advantages over a novice jungler. On the other hand even if you aren't jungling for your team knowing where the enemy jungler is and what they are most likely to do. This knowledge can give you an advantage as you can prevent yourself from getting ganked or set up a counter gank for your team. The third most important is ward placement even if your not your teams support or jungler, you should usualy buy atleast one on your first back. Knowing where to put wards can give your team strong map control and prevent counter warding by putting them in obious place if the enemy team picks up an oracle elixer.
Answer: Practice and Champion Knowlege: Before going into a game, know your champion and practice with bots, this way you will not feel yourself frustrated.
Map awarness: I have discovered that this is very hard to get, but when you manage to, you will enjoy more the game and wont get ganked that easy.
And Patience: A lot of this will help you to dont lose the cool and enjoy the game.


Collapse a section of a huge function

Question: Is there an elegant way of hiding/collapsing/folding only a portion of a function?  If functions could span multiple cells, this would have been straight-forward!
Comment: One thing I like about Mathematica is that stuff that "doesn't exist" can often be made exist quite easily. I think this is doable and useful to have (+1). Some kind of shortcut that wraps the selected boxes with an InterpretationBox with a button "+" that restores the original boxes for example. If I have time I'll try it and post if it works. Let's hope someone does it first and better than I can
Answer: The Mathematica Front End does not have this feature.  Wolfram Workbench does though.
However, it is possible to collapse cell groups in notebooks by double clicking their brackets.  This is useful.
For navigating functions, the Ctrl+. key combination (extend selection) is extremely useful.
Comment: +1. One of the reasons that FE does not have this seems to be that it is centered around Mathematica expressions, not lines of code (unlike WB). There is a certain impedance mismatch between the two. I think, IDEs are more oriented towards statement-based rather than expression-based languages.
Comment: @my account_ram for completeness: You can also double/triple/n-click anywhere in a cell and get the same effect as with Ctrl-., i.e. selection of successive expression levels.
Comment: CTRL-. was a nice find!
Answer: Also, for ease of use when working with sections etc., activate the "Show open/close icon for cell groups" checkbox under Edit->Preferences. This adds a toggle chevron on the left side.

The frontend encourages/enforces you to break long code passages into smaller parts, which is not always a bad idea, especially for testing and debugging (although debugging in Mathematica is something of a sore point when you are used to other systems). Still, a solution for in-cell partitioning would be nice-to-have.
There is also some option to format sections so that a click on their content toggles open/close instead of just the tiny triangle, but I can´t remember at the moment how that worked. Perhaps someone will chip in here.
Comment: Just noticed for the first time that the "Language" option, while set to German by default here does change exactly nothing and leaves everything at English. I think the last german language pack was for version 5?
Comment: Mathematica 8 does not have a German language pack, so that drop down menu doesn't really do anything for German.
Comment: do you know whether it is possible to toggle this option with a command like `SetOption`?
Answer: Preamble
I have been toying with this feature as a part of some set of tools I have been working on (the code formatter in particular). The recent question prompted me to post a small illustration here. This is more to show how things might work than a complete solution, though.
I prefer to work with the code formatter, but you don't have to, if you don't feel like it:
Import["https://raw.github.com/lshifr/CodeFormatter/master/CodeFormatter.m"]

Code
Here are some functions we will need:
prn = CellPrint[Cell[BoxData[#1], "Input"]] &;

ClearAll[codeFoldSetDelayed];
codeFoldSetDelayed[boxes_] :=
   boxes /. {
     r : RowBox[{lhs_, ":=", rhs_}] :>
       Module[{lhsVar, rhsVar},
         With[{var1 = ToString[lhsVar], var2 = ToString[rhsVar]},
            MakeBoxes[#] &@OpenerView[{lhsVar, rhsVar}] //. {var1 :> lhs,
            var2 :> r}
         ]]
   };

ClearAll[codeFolded, codeFoldedSimple];
SetAttributes[{codeFolded, codeFoldedSimple}, HoldAll];
codeFoldedSimple[code_] := prn @ codeFoldSetDelayed @ MakeBoxes@code;
codeFolded[code_] :=
  prn @ codeFoldSetDelayed @
       CodeFormatter`FullCodeFormat @
           CodeFormatter`CodeFormatterMakeBoxes @ code

In what follows, I will use codeFolded, which will also format - but if you don't want to use the formatter, you can use codeFoldedSimple instead. Both functions implement, in a very crude and primitive way, code-folding based on the OpenerView.
Example
So, now, I take some random piece of code from one of my recent posts:
codeFolded[
  ff[a_, b_, n_] :=
  With[{fibF =
    Function[code,
      Block[{fib}, fib[m_] := fib[m] = fib[m - 1] + fib[m - 2];
      code], HoldAll]},
   fibF[fib[1] = a; fib[2] = b; fib[n]] +
   fibF[fib[1] = 2 a; fib[2] = 2 b; fib[n]]]
]

I deliberately did not format the function. Now, the result looks like

When you click on the opener, the result looks like

Comments
First, it should be clear that the resulting cell is not supposed to be evaluatable. One can probably make it evaluatable in at least two ways: either by using InterpretationBox, or by supplying some custom CellEvaluationFunction, which would assemble the original code correctly.
Next, the implementation above is just the proof of concept, nothing more. I am working on a more systematic and powerful version of this as a part of some larger set of tools on which I work (as a side project). So, hopefully, some time soon I will be able to say more.
One deeper reason why I connect this with the code formatter is that the pattern-matching based on boxes is fragile, so the proper way of doing this is via matching to the symbolic intermediate representation created by the formatter. Such functionality I call formatting annotations, and I do plan to include a general support for such annotations in the next versions of the formatter.
Finally, it may well be that this way of doing things is fundamentally flawed for reasons known to more knowledgable people than myself, since I am by far not an expert in FrontEnd.

Collapse a section of a huge function


Why are apps purchased on iPhone and iPad being deleted from device when synced?

Question: Apps that are purchased on my devices are deleted from the devices when I sync them with my desktop. iTunes states that the purchases are being transfered, but they are still deleted and do not show up under the iTunes app list. What is causing this?
Answer: For some reason when it syncs, it sometimes only remembers the iTunes information and doesn't read the device information. So you may find that after syncing it will deleted apps you'd installed and install apps you'd deleted. It's very annoying. To get around that, I have set my devices to not automatically sync when plugged in. When I do plug them in, I right click the device name, click Transfer Purchases, and after that has been completed then I sync.
Comment: No problem. Glad to help.
Answer: There's not enough information to diagnose what's wrong with your iTunes and/or iPhone/iPad.
That's definitely a bug, since transfer of apps into iTunes should happen, did you seek customer support?
PS: Make sure your computer is authorized to have those apps. It's under "Store" menu -> "Authorize This Computer". Enter same Apple ID and password as you do when buying apps on your iPhone/iPad.


Has the US clarified where they (rather than Turkey) expect the SDF to withdraw from?

Question: VOA reported yesterday:

With the withdrawal set to end Tuesday evening local time, Erdogan is warning Washington of its responsibilities to enforce it.
"We expect our American allies to keep their promises this time," he said Sunday.
Turkish Foreign Minister Mevlut Cavusoglu further ratcheted up the pressure on Washington.
"We have 35 hours left. If they don't withdraw, our operation will resume. This is also what we agreed with the Americans."
SDF forces are reported to have withdrawn from Ras Al-Ayn in northeastern Syria. The town was the center of the heaviest fighting in the Turkish operation.
Ankara is demanding the withdrawal of all Kurdish militia from a 450-kilometer-long strip to a 30-kilometer-deep strip from the Turkish frontier. The SDF maintains it only agreed with Washington to a partial withdrawal.
Adding to the confusion, analysts point out that the U.S.-Turkey deal does not specify the parameters of the withdrawal and size of a "safe zone" that Ankara seeks to create.
The ambiguity is heightening suspicions that Washington struck different deals with the SDF and Ankara in a bid to score a diplomatic victory, albeit a temporary one.
"V.P. Pence's Ankara visit looks as if the point was to merely announce a 'deal' rather than to implement one," said former senior Turkish diplomatic Aydin Selcen. "Whether Pence and (Secretary of State Mike) Pompeo's duo actions are directed to cater to White House's internal political narrative or towards achieving tangible change is beyond me."

They also interviewed SDF's commander Mazloum Abdi:

Question: You have accepted the U.S.-Turkish deal that was announced last week. What do you say about it?
Abdi: "We haven't accepted the U.S.-Turkey deal in its entirety. We have only agreed to the cease-fire. Our forces have already withdrawn from Ras al-Ayn and Tel Abyad. In return, Turkey would commit to a permanent cease-fire in those areas with the U.S. being a guarantor. As for other details of their agreement, nobody has discussed them with us. Therefore, we do not accept them. We have relied on the U.S. narrative of the agreement, which says that the [Turkish] operation will be limited to those two towns. We will never accept the Turkish narrative, which says that Turkish forces will enter all areas in northern Syria along the border with Turkey."

Has the US clarified in the meantime where from does the US (rather than Turkey) expect the SDF to withdraw?
Answer: Apparently the answer is that the US is happy with however the SDF interpreted that:

"Today the Vice President received a letter from General Mazloum (Kobani) notifying him that all SDF forces have withdrawn from the relevant area of operations," said Pence spokeswoman Katie Waldman. "The Vice President welcomes this development and sees it as having satisfied the terms of the 17 October agreement, as pertains to the withdrawal of the YPG."

Turkey however is another matter, as they've struck a deal with Putin which sets a new deadline (during which there's still ceasefire) for the SDF to comply with the joint Russian-Turkish demands. And Erdogan was apparently not happy with US-SDF interpretation:

After the Sochi talks, Turkish broadcaster NTV quoted Erdogan as saying the United States "has not fully kept its promises" under last week's temporary truce.


Is EHIC card enough for Erasmus students in Germany?

Question: A friend of mine is going on exchange under the Erasmus programme in Germany. She is a EU-citizen and has EHIC card. Does she need another health insurance or is the EHIC card enough for her stay?
Comment: I took the liberty to retag the question, but I don't feel 100% sure about it. Still I think that we don't need a seperate tag [tag:ehic] since it's reasonably covered by [tag:health-insurance] and [tag:eu-citizens]. I'm certainly open to discussion.
Comment: @tohecz I rejected it. I agree that we probably don't need the ehic tag, but note that eu residents and (non eu citizens) can also have ehic card
Comment: I'm not sure that the fact they can have it means it is not primarily about EU citizens, as long as the situation is typical for EU citizens.
Answer: For Erasmus, the EHIC card from the home country is enough. During her stay, your friend is still officially registered as a student in your home country so that is where she is registered for health insurance. In addition, EHIC card entitles one to necessary health care in all EU countries so she is covered in case of an emergency. Still, it can be a good idea to get a complete medical checkup before leaving as that is something that is not, to my knowledge, covered in other EU countries.
Comment: I think you lose your insurance if you get employed (even small part time job) on the EHIC card. Can somebody confirm it? It may be iportant to know.
Comment: @Smiling_Man That might depend on particular detail. For example, under certain circumstances, you are not required to pay health insurance from your part time job (typically if you earn below certain threshold) and then you would keep your student EHIC card. If you are however required to pay health insurance then you will have to unregister from health insurance in your home country and register in the country where you work.


What has happened to the climate?

Question: In Blade Runner 2049 (2017) it is set in California, but is seeming always raining or overcast, almost more like Seattle climate. It clearly does not match the climate of California as we know it. I assume there is some kind of in-universe explanation for this but I don't recall it being explicitly mentioned in the movie. What happened to the Earth's climate in the Blade Runner universe?
Answer: We don't precisely know .
Only that...it seems to be environmental related...and probably our own fault.

In one of his earliest interviews about the movie, Villeneuve teased that the world will be on the brink of environmental disaster in the film. "The climate has gone berserk — the ocean, the rain, the snow is all toxic," he said.
Source

In the original "Blade Runner," Ford's Deckard was constantly soaked by rain, but in the new film, the weather is much less predictable. In the intervening years, the climate has gone berserk due to rampant pollution, turning Los Angeles into a chilly, desolate place. "As much as the first movie had an atmosphere of constant rain, in this one it would be colder," the director says. "Basically, you could say that the first movie was made by a man from London, England, and the second one was made by someone from Montreal, Canada."
Source
Answer: In the very beginning where they give a brief textual exposition of the world it's stated that:

After the collapse of eco-systems in 2020's humanity was on a brink of
  a great famine, but Wallace's genetically engineered products saved
  humanity.

Apparently the eco-systems collapsed not only locally on the West Coast but throughout the whole world which could lead to big changes in the climate since a lot of climate affecting parameters are dependant on the products of living organisms. Also consider that in the original movie Los Angeles already looked more like New York than California which means that the climate has been changing in this universe for quite some time.
Also in 2022 a nuclear warhead was detonated producing immense EMP which effects are still resonating in 2049. Maybe the warhead dealt more than EMP damage?
Comment: Note that the original movie is set in 2019, so in-universe the climate had definitely started changing already before the 2020 collapse.
Answer: The climate is already bleak in 2019 and gets worse as time progresses, which is even more aggravated by the nuclear explosion above LA's airspace in 2022. But the erratic weather, violent sea and walls we see in 2049 are mainly due to the effects of man-caused climate change.
From the oficial movie website:

2049: When we return to Los Angeles, 30 years after the original movie, climate change has caused the sea level to rise dramatically. A massive Sea Wall has been built along the Sepulveda Pass to protect the Los Angeles basin
Comment: The official website seems to have removed the part about climate change (there has been some political backlash, perhaps?). But if you check [this promotional video](https://www.facebook.com/BladeRunner2049/videos/1368560286592428/) launched before the movie, you can still see the full text in the last entry.

What has happened to the climate?


How to play e#?

Question: Recently I have seen E# in my sheet music. I play a flute but I also have a piano. And on the piano there is no black key above E. Can somebody tell me how to play E# on a flute or at least on a piano.
Comment: You mean probably: how to play e# (not c#) - I assume.  As you may know ef and bc are a half step or a minor second. You can see it as there is no black key between this white keys. You also know that the function of a sharp is to augment the referring note a semi tone. So a sharpened e is equivalent with f (e# => f as well b => c: well tempered tuning!) Mind: This works on keyboards. On a flute and on many other instruments we can adjust this tones to their lead tone function by lifting them a little bit higher.
Answer: The # sign means to raise the note one half-step. On the piano, that means to play the next note immediately to the right, regardless of whether or not it is a black note!
If you look at E on the piano, you'll notice that the key one half-step above E (immediately to the right of E) is F. Therefore, E# = F.
It may seem rather silly to spell it as E# when they could've just put F natural instead, but there are times when, depending on what key you're in and the context of the music, it is actually correct to spell it as E# rather than F.
Comment: No need to feel silly, I appreciate that you asked the question. Asking questions is how we learn, and being willing to ask what seems like a silly question is what sets apart a true learner from a half-hearted dabbler.
Comment: Thanks. I feel like an idiot for not figuring this out.

How to play e#?


Past perfect with before-clause

Question: I don't get the difference , why in first example we use past simple, and in the second past perfect. " He decided to get a present for his children before he left Rome" " He began apologizing before I had paid the driver "
Answer: As you have been learning from your similar questions, the perfect tenses present an action as one that has been completed.
One action's completed state can serve as a relative point of reference against which other actions are situated in time. Other time-phrases (e.g. "before", "after" and so forth) can serve much the same purpose.
Time-phrases can work in tandem with the perfect tenses, in which case they corroborate each other. But if the time phrases alone are clear enough in context, speakers will often use the simple past: the idea is readily understood without the temporal information supplied by the perfect.

He decided to get a present for his children before he left simple past Rome.
He began apologizing before I had paid past perfect the driver.

In the first sentence above, the time-word before clearly is sufficient to present the simple idea that his decision to buy a present occurred earlier than his departure from Rome.
In the second sentence above, the idea is not as simple. Notice that the sentence is trying to situate one action-in-progress relative to another not-yet-complete action.  Let's look at the time-information supplied by the sentence:
He {began apologizing} {before} I {had paid} the driver.
The act of apology began and progressed BEFORE the driver had been paid.
Expressing this idea, which involves an action in progress in relation to a yet to be finished action, is a far more complex undertaking than expressing the simple fact that "one action happened earlier than another action", which we have in the first sentence about Rome. Situational nuances are being presented there: the person apologizing did not wait for the payment of the driver to be completed. We don't have the full context, but he is apparently so eager to apologize that his apology interrupts, or at the very least occurs during, the action of paying the driver.
Answer: When we talk about two activities we use the past perfect for the first activity and simple past for the second activity.
 Forexample:
I had completed my home work before I went school.
 but some grammarians lik"Michael Swan say that past perfect is not necessary when the conjuctions before and after are used.
So the first sentence " He decided to get a present for hischildren before he left Rome" is correct
Similarly' He had decided to get a present for his children before he left Rome' is also correct
The second sentence is rather confusingi
so if it is rephrased the meaning becomes clear
I think it should be rephrased as
"I had paid the driver before he began apologizing
or
I paid the driver before  he began apologizing
I  paid the driver is the first activity
He began apologizing is the second activity
Then the sentence means you (had)paid before he began apologizing
He began apologizing  before you
paid is possible if apology happened before the payment
 or
He had begun apologizing before I  paid  the  driver means the same thing
your second  sentence seems vague
Answer: the before term indicates an action that was done prior to a previously stated action. so he paid before the other person apologised, in such a time sequence we use past perfect for the action that occurred before in the past(both actions were done in the past butt quote not at the same moment back then)
Comment: Mariam, thank you , but as I understand this sentence it's contrary of what your said first action was he started apologizing and the second presumable action should have been payment to the driver ( we don't know from this this sentence  did this even happen)
Comment: Mariam, where are you ?

Past perfect with before-clause


Which electrolyte is most important for century rides?

Question: Besides keeping up with hydration and carbs, which electrolyte is most important in maintaining muscle endurance for longer rides like centuries?
I'm guessing it would be potassium or calcium.
Trying to plan ahead on which snacks or drinks to use for my next ride, RSVP, Seattle to Vancouver.
Comment: As altomnr suggests, you lose a lot of sodium in sweat, and it is certainly the electrolyte you need the most of in grams/hour or whatever.  Potassium is #2.  Most people don't lose enough magnesium to worry about, if they maintain normal nutrition.
Comment: Could you please add some more information to your question.  168 miles?  That's quite a ride.  Is there support for the trip?  Are you doing it in one hit or planning rest stops?  What time of year and what temperatures is it likely to be?   What's your cycling experience - how far do you ride each week ?
Comment: It's the one you're about to run out of.  (Hint:  Calcium is never a problem so long as you still have bones.)
Comment: Again, unless this is a race, just eat when you're hungry.
Comment: @DanielRHicks You're right that magnesium losses during exercise are insignificant, but magnesium deficiencies are very common and under-diagnosed because blood serum levels, which doctors use to diagnose it, are a very poor indicator.
Comment: > *which electrolyte is most important in maintaining muscle endurance* Oh, Lithium ion, and a hidden motor. :)
Answer: Most likely sodium.
However, a lot of it depends on the person. One person might need more of one electrolyte than another, so it's difficult to make a judgment on the order of your "most critical" electrolytes. A sweat test would be a great way of testing which it might be.
Comment: While Na is certainly a very important electrolyte, with a little care most will have sufficient intake to offset losses. One very important electrolyte that is often overlooked is Mg, which is critical in many metabolic pathways and is often deficient in our diet.  It is often through to be a factor behind poor performance.
Comment: Agreed - magnesium is the one I have to focus on the most, personally, but sodium still has it beat in terms of quantity lost (typically). That's where a sweat test could be beneficial.
Comment: It has been estimated that 60% of all westerners are Mg deficient. This is because modern farming practices have depleted soils of Mg such that many foods that used to be high in Mg no longer are. To compound the problem, doctors typically rely on blood serum levels, which don't reflect deficiencies until they become severe. That's because the vast majority of Mg in the body is intracellular, so blood samples can't accurately measure it. And worse yet, it can take months of supplementation to restore normal intracellular levels.
Comment: Anyone with atrial fibrillation (which includes a LOT of endurance athletes such as cyclists) should probably take daily Mg supplements. Most cardiologists prescribe Mg supplements now for their afib patients for this reason. And for you guys and gals who have trained and ridden hard for many years, you should pay attention to afib news since it's quite possibly in your future.
Answer: The five major electrolytes for endurance athletes are Sodium (Na+), Potassium (K+), Chloride (Cl-), Calcium (Ca++), and Magnesium (Mg++). Of these, I would say sodium is the most important one, followed by potassium.

Sodium is the most abundant and perhaps the most important of the electrolytes.  Na+ is found in higher concentrations outside of cells in our bodies.  All cells depend on sodium and potassium to bring nutrients inside the cell and to remove waste.  Nerve conduction–a process important for thinking and for activation of muscles—is also heavily dependent on sodium and potassium.    Sodium Chloride (NaCl) is table salt and often referred to simply as "salt."  Many foods contain sodium. Deficiency of sodium is called hyponatremia.  Hyponatremia is the most common electrolyte disorder in the U.S.  Hyponatremia in athletes is usually due to sodium lost in sweat.  Other disease processes may cause hyponatremia, but the symptoms of hyponatremia are the same for athletes and non-athletes.  These include fatigue, muscle weakness, muscle spasms or cramps, convulsions, nausea, vomiting, confusion, or decreased consciousness.  Vomiting due hyponatremia can cause Na+ levels to drop even further. - A Tale of Five Electrolytes.
Comment: I wanted to give a shout out to Mg as "low Mg+ is often the reason for sub-optimal performance" - from your article.  Mg is an important cofactor for many metabolic processes and most diets have Mg deficiencies, especially for endurance athletes who lose a lot of electrolytes through sweat.  The other electrolytes are readily available through a variety of foods so deficiencies here are more easily prevented.


How to identify a specific operating system with port scans?

Question: According to the implementation of the TCP/IP stack an attacker is able to identify which operating system is running on a network device. Is there any paper or the like according on this topic?
Answer: There's also a Nessus Plugin for that. You can find more details here.
By the way, this technique is called OS Fingerprinting. You can find more details about it on this Wikipedia Page of course and in this SANS paper.
Answer: Perhaps Remote OS Detection would be of interest to you.  And, of course, you can test what you see there with nmap.


Malformed input-Unknown command: 'mon-put-metric-alarm'

Question: I am configuring my aws ec2 ubuntu instance for autoscaling. I have set the launch config file and also auto scaling group. I was quite successful in setting up the auto scaling policy too. I have a return POLICY-ARN which has to be used to set the cloud watch policy.
When I run the command thats as-put-metric-alarm I am getting this
"Malformed input-Unknown command: 'mon-put-metric-alarm'"
I tried to solve it I am able to understand whats wrong actually.
Kindly help me out
Answer: I finally figured it out. The problem was the PATH variables were not set properly.


Obtaining a licence for a patented product

Question: I would like to obtain and become the sole distributor of a product/service that is patented in the US.
What is the best way to go about this?
Answer: After you do some homework call up the inventor/owner. You can look up the owner (assignee) from the google/patents page for the patent. If there is nothing in the assignment database, then the inventors are probably the owners. By looking in Public PAIR at the USPTO you can see the inventor's address and the current official correspondence address. I would check to be sure the patent is unexpired has not been declared invalid or unenforceable by a court and the maintance fees are paid.
Depending on how exclusive you want to be (geographical or field of use or time-limited or completely exclusive with the right to go after infringers) you and the owner might consider you buying the patent outright.


How do I optimize the window lengths in STFT?

Question: I have many EEG signals and I want to analyze them using linear methods such as STFT (Short Time Fourier Transform). In STFT , How can I optimize the analysis window length, to reflect the frequency spectrum of each analysis window in a proper way?
Comment: If you're going to optimize something, you need an objective measure. Your question doesn't really say how you measure the "optimal" window length. What do you mean by reflecting the frequency spectrum in a "proper way?"
Comment: @Maen: you want to analyze EEG signals to do what with them?
Comment: Votes and best answer validation are required
Comment: "*Votes and best answer validation are required*", they are welcome, ethical, polite, good practices, a factor in the success of the stack, what you want, but not mandatory. SE isn't a dictatorship. You cannot have respect for all good practices and stack attraction at the same time, that's the stack Gabor principle.
Answer: This is the classic "uncertainty principle" of the Fourier Transform. You can either have high resolution in time or high resolution in frequency but not both at the same time. The window lengths allow you to trade off between the two.
If you want to detect "events" in your EEG signal with a resolution of say 10ms, then this should be your window length. This will give you a frequency resolution of about 100 Hz.
Answer: The optimum window length will depend on your application. If your application is such that you need time domain information to be more accurate, reduce the size of your windows. If the application demands frequency domain information to be more specific, then increase the size of the windows. As Hilmar mentioned, the Uncertainty Principle really leaves you with no other choice. You cannot get perfect resolution in both domains at once. You can get perfect resolution in only one domain at the cost of zero resolution in the other (time and frequency domains) or in-between resolution, but in both domains.
I do not know if this answers your question since you asked specifically about STFT. You could try to use wavelet transforms to get at the information in the signal. Wavelet transforms will give you resolution over a much larger range by analyzing the signal at multiple window resolutions.
Answer: I don't know EEG but the basic (maybe I should say fundamental) issue when using the STFT is choosing a proper window length. If your EEG is periodic and you want to resolve the fundamental and harmonics you should use a 'long' window. If you instead want to detect the onset or presence of some event or you're more interested in the envelope of the spectrum you can use a 'short' window.
Answer: I have spent a lot of time optimizing windows in time-frequency analysis or filter-banks. One can optimize them for detection, denoising, signal separation... It is very dependant on the application. As time-frequency analysis is generally redundant, optimizing analysis or synthesis  windows are different tasks. And length only one parameter in window design.
The problem is even more complex as the discretized formulation of optimality is
much more complicated than the continuous time-domain case (see e.g. An optimally concentrated Gabor transform for localized time-frequency components).
So my present practical rule of thumb is: start with a window shape and length that seems ok. Then repeat the analysis with two windows with twice and half the length, and combine the results.
Answer: Usually wide window size gives better frequency resolution but poor time resolution and vice-versa. Look at this example where I generated a spectrogram of a sine wave with 5kHz and sample rate of 22050Hz, from my C++ code.

The above spectrogram has window size of 2048 samples and overlap of 1024 samples.
Look at this spectrogram:

This one has window size of 512 samples and overlap of 256 samples.
Can you see the difference? The first one has better frequency resolution than the second one. But the second one has better time resolution when compared to the first one. So, choosing window size depends upon your application. If you are dealing with speech samples to track pitch, choosing larger window size should be the appropriate one.
Comment: Simple sine wave is no good for explaining the frequency resolution. Even sweep sine is better for that.
Comment: So what kind of input would be good, according to you?
Comment: I already did mention that above.
Comment: You mean sweep sine?. Is there any other kind of signal that I can use? I have a presentation on spectrogram and would like to display some good stuffs in my slide about windows. Would appreciate any tips :)


How can I negotiate a medical bill that seems excessive?

Question: My son's pediatrician referred us to an occupational therapist for an assessment.  The pediatrician was concerned about the way my son was holding a pencil with both hands.  The details aren't that important.  We spent 30 minutes with the therapist.  The therapist advised that he did not need ongoing therapy and gave us a suggestion to correct at home.  Three weeks later, I get a bill for $475 (after the group insurance adjustment).  After doing some research, I've come to the conclusion that the typical cost is $90-170 for an evaluation.  That seems reasonable.  I appreciate any advice on how to negotiate with them.
Comment: Have you called the office yet to get more information or is this a "pre-call" question?
Comment: Calling the office tomorrow because they were already closed for the day.  I did already speak to the insurance company though.  I was mainly looking for advice on what strategy to take to get a reasonable fee adjustment.
Comment: I spoke to the billing office.  I offered to settle with them for $175.  The lady said they could offer me a 20% discount, bringing the total to ~$380.  I told her that wasn't good enough.  She said they would take any payment I took, but they need $50 a month to stay "in good standing".  She also said they would turn me over to collections after 120 days.  I'm shaking in my boots.  Honestly not sure where to go from here.  Considering letting the hospital know about it and that I am notifying everyone I know via social networking to use one of the other providers in town.
Comment: What is the source of your conclusion that $90-170 is the going rate? Was the provider an out of network provider? If that's really the rate, you're being defrauded -- let the billing person know that you believe that they are attempting to defraud you and your insurance company and intend to report them.
Comment: Medicare rates as well as other provider rates.  Example: http://www.akrongeneral.org/portal/page/portal/AGMC_PAGEGROUP/Price_guide/PRICE_GUIDE3a
Comment: Update: Someone identifying herself as a collector called and offered the same exact deal (20% discount) about 6 months ago.  I have not heard anything since.
Comment: What Medicare is willing to pay was often less than our costs when I worked for a non-profit health care provider.  Commercial payers and donations made up the difference.
Answer: I think your first step is to be asking for an itemized billing as to exactly what services they claim to have rendered in the half hour that would result in that sort of charges.
These days a lot of medical providers have outrageously high rates if you are not a member of a medical plan that has negotiated rates with the provider.  I've heard of instances where someone without insurance was being charged anywhere from 5-8 TIMES more than someone covered by a health plan would be billed.   (this seems to be the new tactic to make up for the expenses of covering those without coverage or a means to pay.
Once you have some kind of accounting for the charges, if you can't get them to reduce it to a reasonable level, it might be time to contact a consumer advocate at a local paper or news station.
If you were recommended specifically to this OT by your primary provider, I'd also let them know about these insane charges, and you might want to suggest it would be in the best interests of their patients for them to find someone else (with less egregious fee schedule) to refer patients to for such services in the future.
An important lesson here is to ask about charges and insurance coverage IN ADVANCE and don't be afraid to shop around and check multiple providers.  There is very little transparency of pricing in the healthcare industry at the moment, and prices for the very same procedure (such as a consult, or medical imaging) can vary widely (e.g. three maybe even four digit percentage differences)  from one provider to another.  You really need to be an informed consumer when it comes to health care these days to avoid being taken to the cleaners.
Comment: +1 for ask in advance. When it comes to our children, we tend to avoid this question. But for non-emergency referrals, ask (about fees).
Comment: thanks for the advice.  That is definitely a lesson learned.  I guess I usually thought that my medical bills in the past were fairly reasonable (yes, I know that's an unpopular position).  I think I will do better to ask in the future.  I know our pediatrician is well intentioned and she is focused on prevention.  In this case, I probably should have done some more research before even considering the OT.  The itemized bill is a just a single line item: Occupation Therapy Evaluation.  I am calling the hospital today and asking what they would take for an immediate cash payment.
Comment: Hospitals tend to fleece people who don't question them: http://nrecursions.blogspot.in/2012/11/pore-in-retina.html
Comment: @kakridge The itemized bill is key.  If there's something there that wasn't actual performed you can definitely get that dropped. *Sometimes* if a price for a commonly available product (i.e. asprin) was unreasonable you can negotiate that down.  Sadly the medical profession seems to be very hard to get itemized bills from, and sometimes the itemized bills are inscrutable as well...
Answer: Personally, I have not had much luck fighting bills that felt excessive but were not incorrect.  In my case it was "external surgery" for a sore shoulder, where the doctor did nothing except gave me a sling, and charged $1000 or so.  It seems like the doctors separate out the billing operation from the treatment operation in order to make it hard to fight.
Billing side:
Me: This is excessive.
Them: We just bill the set amount for the treatment the doctor code, and have no discretion.  Let me transfer you to the doctor.
Doctor side:
Me: This is excessive.
Them: We coded what we did, and it would be fraud to change that. We also have no idea how much things cost on the billing side, so we have no way to warn you before having something done that is so expensive.  Tough luck.
I recognize this is an example of being unsuccessful, but it's useful to know the script they follow.
Comment: I would suggest that this separation is deliberate on the part of the insurance companies.  They get more, the doctors don't have a clue, and you get scrooged.
Comment: Me: Would you like to find out if a jury considers it excessive?
Answer: For typical insurance, there's a co-pay, e.g. $15 for primary care doctor, $25 for specialist. So long as the doctors you use "accept" the insurance, they agree to accept the insurance company's payment.
When you were referred, did you ask if they were on your plan? In my case, the doctor or hospital can charge whatever, but I'm paying $15/$25 (10% for hospital visits) and that's it. If the therapist was "off plan" you can appeal it, but be careful, if you don't get some agreement, they can turn you over to a collection agency.
Comment: To be clear, I am not debating the insurance coverage.  The bill that I received claimed that the total bill is $1180.  $2400 per hour for handwriting evaluation?  The hospital probably writes off most of that $1180.  My insurance company told me that the provider is allowed to collect up to $475 from me.  I looked at the Medicare fee schedule and Medicare allows collection up ~$90.  I'm just using that as a comparison. $475 seems completely unreasonable.
Comment: That's an outrageously high copay. I'd call and try to talk them down.
Comment: @kakridge: Taking Medicare loses money unless your on-staff physicians would otherwise be idle. That is no way to get a fair amount anymore.
Comment: @Joshua : I don't disagree. This is why I offered them roughly double the Medicare fee schedule.  I gave a range in an earlier comment with medicare being at the low end of that range.
Answer: Scenario 2 is exactly what happened to me. Company took on new insurance provider, I took my daughter to our 19 year long pediatrics office with potential strep and a sore belly button (pierced). PA cultured her for strep and looked at bellybutton, said it looked infected and suggested she take the ring out. Asked my daughter if she wanted to take it out herself or would she like the PA to take it out. My daughter told her she could do it since she had a better angle. The PA unscrewed the belly-button ring and removed it (surgical procedure #1 $196.00). After she removed the belly-button ring, she pressed the area and said yes it is infected and swiped away some pus (surgical procedure #2 $350.00). With that she cultured the belly-button area for strep too (positive for strep in both areas-keep hands away from piercings if your sick!). Strep culture costs and office visit added another $173.00 (no problem with that) to total $719.00.
I am contesting but the response is exactly as smackfu has outlined. Our new provider requires us to absorb the first 7k in deductibles before they kick in, Great! But I had no idea our long standing and trusted physician would be ripping us off on basic health care.
Comment: If your deductible is $7K - you should consider HSA, and look for a plan that is not a high-deductible. Take it to your company HR, why did they switch to such a horrible plan? For $7K a year you might get a private insurance with better terms. I would look for another job.


Cant see the Recent updates after Replacing Existing files in setup project

Question: I have created a setup project for Windows Application . I have set following property to replace the existing version with the new version.
RemovePreviousversion=True;
Productcode=change;

But when I run exe from new installed version. I cannot see my new updates. It gives me the output of previous version!
The whole Explanation is Here
I have RemovePreviousVersions set to TRUE and InstallAllUsers set to TRUE.
When I need to do a new release, I update the Version field with a new version number in the installer and VS prompts me to update the product code, to which I answer YES.  I have verified that it does indeed change the product code, but the package code also gets changed with it (verified by diffing project files using sourcesafe).
The UpgradeCode never changes between versions.
My version number changes are of the form:  "1.1.2"  -> "1.1.3" for example (just in case that has anything to do with it).
So only 3 fields are different between builds:  ProductCode, PackageCode, and ProductVersion.
When I've done all that, I build the installer.
When I install the new version (I always install for all users and always into the same directory), I have seen three different results at various times:

It will appear to in install the new version, but I really end up with the old files still there (and one instance in the add/remove programs).
I end up with 2 instances of the app in the add/remove programs, both with the same name, and both pointing to the same directory.
It will uninstall the old one first and then install the new one (what it is supposed to do).

It is very frustrating to explain to users that to be safe, they have to uninstall the old manually before installing a new release because I have to tell them "it doesn't always uninstall the old one like it is supposed to".
Any suggestions?  Why isn't this working?  What am I missing here?
Answer: I Found answer.
Also need to change AssemblyVersion and AssemblyFileVersion in AssemblyInfo.cs


How to get cheap cookie cutters?

Question: With the cookie baking season upon us I broke out the cookie cutters for sugar cookies, however almost all of them are pretty deformed or broken (from moving houses). I haven't bought any cutters in a long time and didn't realize how expensive they've gotten.  Are there any cheap ones out there that are worth buying or should I just wait until after Christmas, when they all go on sale? Or should i just use an empty tuna can and make a bunch of circles?
Comment: If you're going to make circles, you could just roll the dough into a tube shape and slice off some circles.
Comment: Well, you see what happens with cheap ones. I look at cookie cutters as a very rare purchase, so don't mind if they're more expensive than seems reasonable, and I don't skimp on quality. Amortized over the life of the cutter, the prices aren't so bad.
Comment: You could make your own to get you through this holiday baking season - google will give you plenty of tutorials. Something cheap and easy to bend would probably be good enough for the short-term, or you could get some decent sheet metal from a hobby store (or hardware store) for more durability.
Answer: I think using an empty can is a brilliant, frugal idea...but if you want something a bit more exciting, chain stores like Bed Bath & Beyond sell decent tubs of cookie cutters. If you have one of those mailer coupons, you can get a ridiculous amount (like a pack of 100) for less than $20.
Comment: Empty tuna cans (cleaned and de-burred of course) also make pretty good round-fried-egg-makers for egg-on-a-bun type things!
Answer: From a price for utility perspective, I prefer plastic cookie cutters.  Metal ones rust and get bent out of shape so very easily.  (If you can wait just over a week, Christmas themed cookie cutters should be should be pretty cheap.)
Answer: I got a set of Ateco cutters this year, and since my daughter, now 5, loves to bake with me they get a lot of use. The set I got nestles, it is a set of concentric circles, and stores back in the can. It was about $15 and my daughter loves the smaller ones, she uses them to make cookies for her animal friends and dolls.
Answer: You can get bags of cheap plastic cutters from toy shops, they are normally used for PlayDoh, but work fine for cookies too!
Answer: FWIW - I find using tuna cans easy - or just roll your (refrigerated) cookie dough into a log, and cut it in slices for consistent sizes.
Here is something I recently picked up from Amazon - custom cookie cutters - so for under $20 you can make custom shapes without having to buy several different sets to get the shapes you need!
http://www.amazon.com/International-Design-Your-Cookie-Cutter/dp/B002WC8Y3O/ref=sr_1_1?ie=UTF8&qid=1292618629&sr=8-1
Answer: I know it's been a while since this was posted but I thought I would add an answer relevant to 2015:
These days you can custom print your own cookie cutters using a 3D printer. While initially the cost is steep (like $1000 or so for a decent one) - You can make so many cool things with these things for pennies once you're up and running. But of course, we don't all bathe in riches. It's like a yacht, it's better to know someone with one than to own it yourself.
I recently bought a 3D printed birthday cookie cutter set from things4thinkers.com for $14.99 and made some awesome cookies for my daughters. Considering it was a custom order I feel $14.99 was cheap. Plus they have a bunch of other pre-made but uncommon cutters which range from like $5 to $15. I asked how much a custom cutter would be looking like a cartoon of my daughter and they said about $25. I think I'm going to do it.
So anyhow, a bag of basic shapes from Toys R Us is about $10 or so. For the common shapes, you'll always find deals in the big box stores and no custom solution will be able to beat their prices. But if you really want to surprise people, see if someone like things4thinkers can make something special for you. It's cheaper than I thought it would be.

How to get cheap cookie cutters?


How to find a minimum set of axioms within a set of propositions?

Question: I have a set of propositions, for example $\{a_1,a_2,\dots,a_n\}$. Some propositions depend on others (for example, $a_1,a_2\Rightarrow a_3$, means if $a_1,a_2$ are true, then $a_3$ is true). I want to find a subset of the propositions to be defined as axioms, in the sense that, these propositions being true imply that all the others are true. The number of axioms should be as small as possible. I want to know whether there are some methods?
Comment: These are called [functional dependencies in database theory](https://en.wikipedia.org/wiki/Functional_dependency) and a set of minimal axioms is called a candidate key
Comment: maybe a more useful reference is the [wiki article about candidate keys](https://en.wikipedia.org/wiki/Candidate_key).
Comment: Do you know anything about the set of propositions? If they come from arbitrary propositional logic, then I suspect there's no better algorithm than trying all possible subsets.  On the other hand if they come from some restricted set of propositions (e.g., Horn clauses or something like that), then maybe there's some room for more sophisticated algorithms.
Comment: (at least the plural of basis is correct now) An algorithm to find a basis (a minimal set but not necessarily the smallest that generates all propositions) is rather simple (see wiki candidate keys). The problem to decide if there is a basis with the number of elements smaller then a given number seems to be NP hard. An algorithm that calculates all bases that is polynomial in the number of different bases and the number of propositions can be found in the wiki entry for the candidate key. But the number of bases may be large so this algorithm is not polynomial in the number of propositions.
Answer: Determining whether a proposition follows from a set of axioms is an NP-Complete problem. Finding a minimal set of axioms from a set of propositions naturally invokes this problem many times as a subroutine.
For example, consider the following set of propositions:
$$P = \{v_1, v_3 \vee v_2, v_1 \wedge v_3\} $$
A minimum set of axioms from this set is $\{v_1 \wedge v_3\}$. But to find it, you have to prove $v_1$ and $v_3\vee v_2$, and those proofs are in general hard to find. The problem is there a set of axioms $A$ for a set of propositions $P$ with at most $k$ axioms? is in $\Sigma_{3}^{p}$, which means it's in the third level of the polynomial hierarchy, which means that it's two levels higher than NP in the way that NP is one level higher than P, to give you an idea of its complexity. I do not know if it is also in a lower level. Browsing through this survey (link) [1] of problems that are complete for various levels of the polynomial hierarchy, I do not see this problem among them, so it's possible that it's not $\Sigma_{3}^{p}$-Complete, but it wouldn't surprise me.
Before you go out to look for a set of axioms, you may want to know whether the set of propositions is sound and any subset is complete (untrue propositions cannot be proved, all true propositions can be proved). These problems have similar NP-scary complexity. First, Is this set of propositions complete? is a problem in $\Pi_{2}^{p}$ of the polynomial hierarchy, because it asks, for all $p\in P$, can $p$ be proved from propositions $P\setminus \{p\}$? Completeness of your system is in co-NP as it asks, Forall all $p\in P$, can $p$ not be proved from $P \setminus \{p\}$? So it seems that checking for soundness and completeness is easier than finding a minimal axiom set, but not by much. (I'm less sure about this paragraph. Is it true that a logical system of propositions $P$ is sound iff for all $p\in P\colon \neg p$ cannot be proved from $P\setminus \{p\}$?)
The comments to your question pertain to the context of database entries, but they are purely syntactic and only establish redundancy in the database, whereas if your question is about propositions, as I understand it, then the contents of the database must be inspected semantically, and this leads you to this complexity nightmare.
[1] M. Schaefer, C. Umans, Completenss in the Polynomial Hierarchy, A Compendium, 2008.