What kind of siege weapons were used during Punic wars?

Question: I would like to know which kind of siege weapons were used during Punic wars on both sides, there is not very much information around.
Answer:
There's actually quite a bit available, even just from wikipedia:
Catapults:
http://en.wikipedia.org/wiki/Battle_of_Carthage_%28c._149_BC%29
Trireme Rams, Corvus (naval):
http://www.historyofwar.org/articles/weapons_corvus.html
Sambuca, Claw of Archimedes, Heat Ray, onagers (naval):
http://en.wikipedia.org/wiki/Siege_of_Syracuse_%28214%E2%80%93212_BC%29#Siege
Battering rams, ramps, roman tortoise, and towers were also very commonly used siege weapons in this time period.  If you're writing a paper or article you might research those more thoroughly; I don't know offhand to what degree these were used in the various battles of the three Punic wars.
You should definitely read up on Archimedes, he's credited as being one of the most famous engineers in history, and was active in crafting defenses for his city during the Roman invasion.
You should also review the use of elephants in this war; while not traditionally "siege engines", they were sometimes used to help break through defenses and were a staple unit for Carthage.
Comment: Elephants weren't used in any significan numbers until Zama (in north Africa, which Carthage lost). The problem was that the Romans had naval superiority, so Hanibal had to march his army into Italy from Spain (over both the Pyranese and the Alps). Not many elephants were left by the time he debouched from the Alps.
Comment: @T.E.D. To add to your comment, I can't seem to find the source now but I remember reading somewhere that those surviving elephants were not even used in battle. It seems to me that elephants were usually mostly for show as they were unreliable and frequently trampled the troops of the army that deployed them.
Answer: As for siege equipment used during the Punic Wars it's quite a long period and should be looked at in a progressive manner.

When the Roman republic entered the war in 264 BC there was little
siege strategy within the Roman army. Their main tactic was the
circumvention of an enemy town with a series of palisades and
connected fortifications. They would then wait it out, some sieges
lasted several months and may or may not have been successful.
Gradually the Roman army was exposed to Greek culture and technology
through their ally Syracuse. They then adopted new machines to their
siege train such as the covered ram etc and heavy ballista.
The Carthaginian army had altogether more advanced Hellenised
siege technology at their disposal. Through years of fighting with the
Sicilian Greeks they had developed and taken ideas from over two
centuries of warfare.

If you need more information try reading JF Lazenby's book on the First Punic War, and Osprey publication Ancient Siege Warfare. (Both sources informed this answer).
Comment: Thanks for your answer, I edited it for format and to provide links to your sources.  Please edit this again if that edit muddied up your answer. Thanks for joining in with us @ History.SE.
Comment: No worries mate, glad to contribute. The formatting was a good idea, it was a rather large chunk of text.


How do you make a picture look like it's coming out of a circle?

Question: How do you make a picture look like it's coming out of a circle?
Like this:
Answer: Tons of different ways to achieve this.  Given the nature of the question, I will share a simple approach.
Photography:
The picture will require the graphic artist to cut the subject out. (in this case a cat/dog)
How To:

Using the "Polygonal Lasso Tool", cut the cat/dog out of the
picture.
With the subject cutout, on a new layer, create a circle using the Ellipse tool.  This tool will allow you to add color, borders,
shadows to both the inside and stoke of the shape. You will want to
make the circle smaller than the subject cutout so it gives the
illusion of coming out of the circle.
With the shape created on one layer and the subject cut out, make sure the subject layer is above the circle layer and drag it on
top of the circle you created.
Answer: This is the approach I would try:

Select the cat/dog.
Create a mask to isolate the cat/dog.
Make a copy of the masked cat/dog and hide it. Make sure the new copied layer is on top of the original layer.
Create a circle and keep its layer below both of the cat/dog layers.
Right click on the name of the cat/dog layer that is directly above the circle layer and select "create clipping mask". The cat/dog should now be cropped along the boundaries of the circle.
Unhide the top cat/dog layer and select its mask in the layer panel.
Use the brush tool to remove any part of the animal that you do not want to have coming out of circle and leave the rest (make sure the brush's foreground color is black and opacity is 100%).


Undersized fruit

Question: My plum tree is about 10 years old and has fruited for a few years.  It produces loads of fruit, loses a lot before ripening, but they remain the size of a very large olive and I don't know how to encourage them to get bigger. I don't feed very often, so that might be the problem. Whilst the fruit are growing, the tree also gets quite a few new branches, which I try and trim back in order to encourage the good stuff to the plums. Do plums take a while to grow to size? It's a self fertilizing victoria plum. The wasps got them all last year, but once ripe they are quite tasty.
Answer: It doesn't sound as if you practice thinning out the fruit - plums particularly have a tendency to form a lot of fruitlets, and even after June drop has occurred, there are often too many fruits left behind which then don't mature properly, remaining small. Guidance on thinning in this link https://www.rhs.org.uk/advice/profile?pid=340.
Also ensure the tree is kept well supplied with water if the weather is particularly dry once the fruitlets have formed.
Comment: thanks so much i didnt know you had to thin the fruit.  will do that now.  cheers

Undersized fruit


How transaction fees differ between different wallets?

Question: In particular, I'm wondering what is the difference (if any) of transaction fees between Bitcoine-core, MultiBit and blockchain.info?
Answer: Bitcoin-Core is a full node and can therefore build up a mempool and estimate fees. This is probably the most secure way how one can estimate fees. You can verify the source code and make your own improvements. The fee estimator allows you to estimate the fees for different confirmations targets (2-25 blocks).
MultiBit does either use a web-api and/or static fallback fees. You depend on third-parties, estimating fees for you. All SPV wallets cannot reasonable estimate fees.
Blockchain.info run its own full-nodes and use it's own fee estimation logic. You need to trust the estimations produced by blockchain.infos logic.
Comment: Right but how does it translate to numbers in a real world scenario, say I transfer 100 mBTC with each of the above?


What is the word to describe the "degrees of freedom" of an instrument?

Question: E.g. a violin can be bowed, allowing a single note to have more changing character than a guitar. On the other hand, a guitar is more polyphonically capable than a violin. Contrast them both with a midi trigger that only plays a single sound, for a set duration. You could say that the guitar and violin have a greater degree of freedom than the midi trigger (more possible sounds can be created), and a debatable comparison between them on how many dimensions are allowed by the instruments. Is there a word for this "degree of freedom"?
Comment: _Expressivity_? https://en.wikipedia.org/wiki/Expressive_potential_(electronic_music)   "One possible metric for expressive potential is the number of degrees of freedom provided by the interface."
Comment: Interesting question! @piiperiReinstateMonica That seems like the core of a really good answer.
Comment: Wonder if this could benefit from 'English Language' SE?
Answer: The word "mudraic" (from "mudra" = gesture) has been used by Indian philosopher P.R. Sarkar to describe how closely the gestures of the musician are connected to the sounds that are ultimately produced.
For example, the violin and similar instruments are highly mudraic, because even slight changes in the movement of arms and hands lead to significant changes in sound. Additionally, this is true for both hands, because any slight change in the left hand changes the pitch and the clarity of sound, while the right arm's movement, speed, angle, etc. all lead to different sounds.
At the opposite extreme, the organ is not a very mudraic instrument, because it is mostly a matter of turning various fixed pitches off and on at given times, with little correlation between your gesture and the sound that is produced.
The Theremin is highly mudraic for sure. The guitar, I'd say, not very much, especially when played with a pick, but a bit more so when strumming, string bending, rasgueado, etc. are employed.
Similarly, the trombone is more mudraic than the saxophone, the accordion is more mudraic than the synth, percussions played with bare hands are more mudraic than percussions played with sticks, and so on.
It should go without saying that the above doesn't imply that mudraic instruments are better or worse, easier or harder, or anything like that. This is just one dimension, out of the many different dimensions where music is created and lives.
There is also some scope for debate, I suppose: for example, how mudraic is drumming? Although any drummer could be cloned by a robot that hits the various elements at the right time in the same spot with the same force, there is no question that drummers must move a lot in very specific ways to obtain their results. My personal analysis is that drumming is highly mudraic with regard to timing, but not mudraic in the context of sound production.
One last observation: in almost every case, to play louder one must move wider, stronger, faster, but because this is true across the board, for virtually every instrument, I would not consider it a differentiating factor. In other words, even if with a given instrument you must e.g. swing your arm wider to produce a louder sound, that alone doesn't make the instrument more mudraic, simply because something analogous is the case with virtually every other instrument as well.
Comment: Disagree with the drumming synopsis - various different sounds are produced from one drum or one cymbal due to where and how it's hit.
Comment: Well, violin isn't that mudraic either if you limit yourself to bow in the same position with same speed and force.
Comment: @Tim to account for the importance of where a cymbal is hit, I wrote "in the same spot", and to account for how it's hit, I wrote "with the same force". Beyond that, while I'm sure that there be some theoretical differences between e.g. a glancing hit on a cymbal with a stick, vs a perpendicular hit, if the force is the same, I'm pretty sure the sound will also be very much the same. Or am I missing something else here?
Comment: Mudraic is a good word, but to me it describes something orthogonal to what OP is asking about. For instance, software like csound or max/msp is not (necessarily) controlled by gesture, but still offers a lot of tonal freedom. Drawbars are physically awkward, but organs still allow control over individual harmonics in an amount that other acoustic instruments don't generally offer. I feel like mudraic refers to the former but this question to the latter.
Comment: There's also which part of the stick, what happens to the stick after the hit, and maybe what stick. I'd say pretty mudraic in all aspects - only my opinion.
Answer: I might use either expressiveness or versatility, depending on the context. For instance, electric guitar volume pedals are called "expression pedals" even though they only modify volume.
I don't think you're going to find a term that's more specific to music than those, because things like timbre and polyphony tend to be talked about independently. On a synthesizer, the attributes are called parameters in the abstract, but I think it's fair to say that a synth with more parameters is more expressive.
That said, to my ear, even "expressive" probably doesn't include polyphony. So if someone says that an acoustic piano is expressive, they're probably talking about the dynamic range, rather than the harmonic possibilities. Likewise, a singer with a very wide pitch range isn't necessarily expressive.
"Expressive," then, seems to imply a precise ability to modulate pitch & volume across time. This paper calls it a "deviation from music notation," which I assume excludes expression markings. But note that such deviations, from the POV of an individual note, are called articulations. But no one says that their instruments are "articulate" :p
With that in mind, perhaps degrees of freedom is already the best term. Though I don't think it's at all wrong to use expressiveness here, especially if you signal that you mean expressions beyond what falls under articulation.
Colorfulness is also decently generic, though nonstandard.
Comment: @JohnnyApplesauce it'd be nice if everyone stuck to that distinction but the makers of those pedals don't. notice how many of these say "volume/expression" https://www.sweetwater.com/c1111--Guitar_Volume_Pedals
Comment: *articulate* (transitive verb and adjective). d : "to give shape or expression to (something, such as a theme or concept)." – [MW](https://www.merriam-webster.com/dictionary/articulate). *technique* : "a way of carrying out a particular task, especially the execution or performance of an artistic work or a scientific procedure." – G. ... Violins can be played with more technique than a midi trigger and are thus the more articulate instrument.
Comment: Volume pedals are called volume pedals. Expression pedals are used to manipulate a continuous parameter, typically on another pedal, and volume can be such a parameter. For example, the Korg XVP-20 is a volume*/*expression pedal. As a matter of fact, Hotone's Soul Press is a \*3\*-in-1 volume*/*expression/wah.
Comment: @johncip Ah, but of those 9 volume pedals on the first page, each of them, I checked, are said in their descriptions to double as parameter-controlling expression pedals.
Answer: I would say that an instrument has its own set of characteristics.
These include
Range: lowest note to highest note
Methods of playing: e.g. plucking and bowing
Tone palette: Which harmonics are present in a given note and how these can be varied by the player
etc.
With regard to Midi I would say that you can vary the parameters; volume, pitch, duration, attack, decay, etc.
https://en.wikipedia.org/wiki/General_MIDI


Which field to use for the search

Question: I am creating a business directory website when everyone comme and add his business to the website to allow people to find him later. A business has many fields (categories, products, services, name, adresse, pictures, comments...) I am wondering which field i must use for the search ? I tried to understund how yelp has deal with this problem but i couldn't understund which field is used in Yelp website !
Comment: Search in sites such as Yelp are far more advanced than just searching against one individual field. They'll use meta data, descriptions, fields, weightings... If you're looking to build a search for such a big site then you'll need to do *a lot* of research into searching and filtering, more so than just one question in one Q&A site.
Comment: @JonW: maybe you should make that an answer
Answer: I am assuming you are talking about the main "headline" search rather than a detailed or advanced search and, if so, I would not restrict myself to one field - look at the type of thing done by sites like Yell.com for example
They allow you to enter a business type or company name in one field and then a location in the second field - so for example, show me a carpenter in London or a company called ABC Construction in Manchester
Both scenarios are dealt with by the same form meaning the customer does not need to decide or click any additional buttons - they just enter what they want and the logic looks after it in the background.

Which field to use for the search


RAM mismatch in macbook pro early 2011

Question: I tried to put two 4GB sticks (OWC) into a MacBook Pro early 2011 17 inch. Either of the 4GB sticks works with either of the stock 2GB sticks but both the 4GB sticks do not work. It causes kernel panics. Firmware is already at the latest version (MBP81.0047.B27). I am well aware of fitment process. Officially it can support 8 gb max.
Comment: please explain what happens in more details, also what is the maximum RAM your Mac can tolerate ?
Comment: Are you running the latest [EFI firmware (version 2.7)](http://support.apple.com/kb/DL1499)?
Comment: http://support.apple.com/kb/HT1270
Answer: Macs are quite a bit more tolerant of what RAM they can take and handle well. If RAM can be upgraded at all. A 2011 MBP has a wide range of options. Using Apple approved RAM modules (at a small premium)  with the same specs as a non-approved module of the same brand usually only gets you small advantages: they pass the hardware test at the Genius bar without issues and are practically guaranteed to work in a Mac. But that doesn't mean the non-approved modules do not work.
It is true that the module has to meet certain specs. But as long as it is DDR3 SO-DIMM with the correct voltage and not too slow the MBP 8,2 from 2011 should be able to handle it.
That means two  DDR3-1600 sticks each at 8GB is way out of Apple's official spec. Yet the machine works fine with them. The 1333 option is playing it safe and slower. Apple's advice: is doing just that. It doesn't even matter whther they are DDR3 or DDR-3L since the L variant is rated at 1,35V but required by spec to also run at 1,5V like the MBP 2011 wants it to. But choosing the L variant doesn't give you any energy savings in this case. To summarise: the machine in question can run at least up to 16GB RAM with 1,5V at at least up to 16000MHz just fine.
And the OP already confirmed that the sticks are working in some configurations but not in others.
Concerning the OP question there seems to be a hardware fault: It might be the logic board (more specific the ram slots being even pickier). Or it might be that the two 4GB sticks have issues. "Mismatched" modules it says in the title. Absent the knowledge of how this old problem went forth the advice had to be:
Most likely at least one of the 4GB modules is somehow flawed. To hunt it down and exclude other possibilities:

reseat the modules: test one module at a time; then both, swapping modules from slot to slot (this not only should pin down any problems with the individual modules but also might clean the slots a bit. Cleaning the slots per se might be an option as well.)
stress test the modules separately at first, then together in the combinations noted above
get the logic board tested, RAM slot failure is not that uncommon
buy modules of the the capacity, same specs both at the same time together (this is belt+suspenders advice; mixing modules should work – and did as the OP demonstrated)
Answer: Macs are notoriously picky about memory. The specs of your memory must match exactly what the Mac is expecting.
Your Mac is expecting:
DDR3 PC3-10600 • CL=9 • Unbuffered • NON-ECC • DDR3-1333 • 1.35V
If yours is not exactly this, you will have problems.
I believe your Macbook can take up to 16GB, so 8GB should be fine.

RAM mismatch in macbook pro early 2011


What is the reason why its so hard to implement Monero into current wallets?

Question: Is monero completely different from bitcoin in the sense that wallet creators haven't added monero as into their list of supported coins? Monero has a pretty decent big following, but its not support in many of the multi-coin wallets. What is the reason for this?
Answer: Monero has a completely different code-base than Bitcoin. It was not inherited from Bitcoin, and it was written from scratch (Bytecoin was the first CryptoNote cryptocurrency, and Monero inherited that codebase, not Bitcoin's - it's a fork of Bytecoin)
Thing is, all Bitcoin clones can simply copy what's already been done and maybe do some small tweaks. On the other hand, people working to implement Monero are pioneers. It doesn't mean that it's harder, but just that it requires work whereas for Bitcoin most of the work has already been done and can be re-used.
Also, due to mechanics of CryptoNote coins, any light-wallet implementation requires more resources on the back-end. Where Bitcoin can simply look-up the balance, Monero has to scan the entire blockchain.
Comment: so getting the balance from one of my addresses requires a complete scan of the blockchain and tally up all the coins that were sent to it?
Comment: In practice - yes, tally up received, subtract what was spent and you get the balance. In some cases it should be possible to cherry-pick only the blocks which you somehow know in advance (like exchange giving you the TXID, or your sender simply telling you where to look) they contain your funds and only scan those. There's no software which lets you do this currently but it could be useful one day. I've only entertained with the [idea](https://monero.stackexchange.com/questions/2390/is-it-possible-to-create-a-lighter-wallet-than-simplewallet-without-giving-up-a/2393#2393).


Practicing image processing and analysis

Question: I'm just getting into image processing and analysis using Python, and I'm looking for astronomical images (preferably raw, unprocessed images) to practice on. Can anyone suggest some places I can download public-access telescope images from?
Answer: I know you've already accepted an answer, but I feel that it doesn't provide a true representation of the type of image processing astronomers actually do. Actual image processing in astronomy is rarely done with JPG, PNG, or TIFF files. Instead, astronomers mostly work with FITS files and cameras/astronomical instruments actually produce FITS files when taking images. The advantage here is that FITS files can record much more information than just image information such as where/when the image was taken, multiple layers of the image, encoded WSC information, etc.
As part the mission objective of various organizations such as the National Science Foundation and NASA, all raw astronomical data taken in the United States by observatories funded by the United States are free and open to the public (after a limited time period in which the observing scientist gets exclusive rights to the data for their science objectives - usually several months to a year). This includes both ground (e.g. Keck, SDSS, Arecibo) and space observatories (e.g., Hubble or Spitzer). This is also true of many observatories funded by other countries as well.
A great place to start would be to head over to the Hubble Legacy Archive. Enter the site and try searching for an object or coordinates. For example, you can search for M101 (otherwise known as the Pinwheel Galaxy). You'll see a list of images come up and next to them, you can download the FITS file generated by Hubble when it took the image.
Another great resource would be the Sloan Digital Sky Survey. This is a systematic astronomical observation of as much of the sky as possible using a variety of instruments. You can practice looking at images and spectra. I should warn you that it will take a bit more effort to figure out where the data is and how to interpret it, but feel free to ask questions here when you run into trouble.
In general though, if you're looking for a particular type of image or data, find an observatory that records it and look for their publicly available data sets.
Comment: To be really nitpicky, the availability of data from HST and other space observatories -- which are funded by NASA -- has nothing to do with the NSF.
Comment: Public availability of telescope data (after a proprietary period) isn't just a US thing: most major observatories worldwide do this, and have done so longer than the major US observatories have (except for Hubble). E.g., the European Southern Observatory, the Isaac Newton Observatory, the Anglo-Australian Telescope, etc.
Comment: A short, simple list of links to HST FITS files:
https://www.spacetelescope.org/projects/fits_liberator/datasets_archives/
Comment: @PeterErwin I know it's the case in the US for sure and knew it was true for other countries/observatories, but I didn't want to make a blanket statement without the proper research.
Comment: More directly for SDSS, you can search for object names or sky coordinates here, and get links to the (bzip2-compressed) FITS files:
https://dr12.sdss.org/fields
Answer: http://hubblesource.stsci.edu/sources/illustrations/
https://www.nasa.gov/multimedia/imagegallery/index.html
Are two sites I have downloaded images from. I had to right click the image to download but it worked.  Maybe more of a challenge for you are images of rain waves. I don't know where to find them though. I think all of images from above sites have been processed so they may not fit your needs.
These sites may help you.
https://ned.ipac.caltech.edu/level5/March01/Andernach/Ander6.html
http://hubblesite.org/get_involved/hubble_image_processors/
The last site is for amateur image processors and has access to raw image data.
Good Luck.
Comment: Neither of the first two sites in that list provide links to "raw, unprocessed images", which would be in FITS format.


How can I experiment with Cloud (Azure, AWS, Google, etc) without going broke?

Question: Cloud technologies are very hot right now, but they can be expensive.  What are the best strategies for learning/trying cloud services without racking up a huge bill?
Comment: Scan github for checked in access keys! Jokes, please dont do this.
Comment: https://www.usenix.org/conference/hotcloud17 Yes, "very hot."
Answer: The three major cloud platforms you mentioned have either free trials or a free tier; these all include spending and resource caps which prevent you from spending more than your free trial allows:
Azure

Azure offer £150/$200/€170 for the first one month of usage, in addition many of Azure's services have a free or low cost tier:

App Service Free Tier
SQL Azure Basic Instance @ £0.005/hour
Azure Machine Learning Free Tier
Azure Service Bus @ £0.04/million operations
Azure Functions @ £0.15 per million executions

If you have a MSDN or Visual Stuido Online account you can also get £100/$150/€130 per month of credit just because you are a subscriber to one of these services.
If you are a startup you may qualify for $120,000 of Azure Credits to host your application through Microsoft's BizSpark programme.
Amazon Web Services

Amazon have a Free Tier which includes:

750 Hours of EC2 which equates to about a month of a t2.micro instance
750 Amazon RDS
5GB S3
250,000 AWS IoT Messages
... and more

In addition there perpetually free usage allowances on most services:

AWS Lambda: 1 million free requests a month
DynamoDB: 25GB Storage
Amazon SNS: 1 million publishes
... and more

Google Compute Platform

Google offer a $300 free trial for 12 months in a similar deal to Amazon. In addition they have free usage tiers for many of their core offerings:

Google App Engine: 28 instance hours / day
Google Cloud Database: 1GB Storage
Google Compute Engine: 1 f1-micro instance / month
Google Pub/Sub: 10GB messages / month
Google Cloud Functions: 10 million executions / month
... and more

If all of that wasn't enough for you most of the cloud providers will compensate you in credits if you blog about their services in detail, you do have to put in a substantial effort up front and "appear" on their radar by writing blog posts, presenting at meetup and conferences but once they see you they will gladly put $100 a month towards your further learning.
Answer: Emulate the cloud on your own hardware
Doing anything substantial with the free tier is challenging.  But you probably have some hardware lying around that you can build your own minicloud on.  If you need more memory you can dig through your junk drawer.  If you build something serious there's some chance you'll decide to buy more hardware, but that is less risky than needing to pay $$$ monthly to AWS to keep your doors open.
LocalStack

LocalStack spins up local emulators of a slew of AWS-style services:

API Gateway at http://localhost:4567
Kinesis at http://localhost:4568
DynamoDB at http://localhost:4569
DynamoDB Streams at http://localhost:4570
Elasticsearch at http://localhost:4571
S3 at http://localhost:4572
Firehose at http://localhost:4573
Lambda at http://localhost:4574
SNS at http://localhost:4575
SQS at http://localhost:4576
Redshift at http://localhost:4577
ES (Elasticsearch Service) at http://localhost:4578
SES at http://localhost:4579
Route53 at http://localhost:4580
CloudFormation at http://localhost:4581

It is completely open-source and it seems like Atlassian is putting a lot of engineering effort into keeping it current.
AppScale

(source: jujucharms.com)
AppScale can help you emulate the Google cloud:

AppScale is an open-source cloud computing platform that automatically deploys and scales unmodified Google App Engine applications over public and private cloud systems and on-premise clusters. AppScale is modeled on the App Engine APIs and has support for Python, Go, PHP and Java applications.

AppScale is supported and maintained by AppScale Systems, in conjunction with Google.

Eucalyptus
Eucalyptus has been around for a bit longer and it has free and paid features.  It supports emulating EC2, S3, and IAM.
Comment: You should also add a note specifically underlying that such emulation should NOT be used to collect performance or scalability data points (in the vast majority of cases).
Comment: By experience,  the raw (hardware) on premise cost is higher than same end usage vm on aws to get equivalent performances. I'm talking about cost only and not taking in account financial optimization for hardware on premise.
Comment: While interesting,  even in a company with roughly 600 vms on premise, I can't spin up things for playing out of a project and there's no available hardware (reselled to a broker). I don't think a student can run most of those things for learning on them.
Comment: Maybe so, but avoiding a huge bill can motivate people to do amazing things.
Comment: You may want to add to the list [AppScale](https://www.appscale.com/community/what-is-appscale/), specifically for running Google App Engine apps.
Comment: Thanks Dan.  I got AppScale added.  Feel free to edit that section to explain them better.
Answer: There are quite a few services that offer 'free tiers' of some description to help new developers get started with a cloud platform without the cost you've mentioned.
AWS have quite a generous free tier:

Always Free

1 million free Lambda requests/month
25 GB of DynamoDB storage
20,000 free requests to the AWS Key Management Service
1 million requests to Amazon SQS
various other services

12 Months Free

750 hours of EC2 computing time (t2.micro)
5 GB of Amazon S3 storage
250,000 messages on AWS IoT
various others

Azure offer US$200 (or £150) of free credit to use in any way you like within one month (but they expire after a month):

You receive £150 of Azure credits with the Free Trial. The choice is now yours as to how you use your Azure credits. Use them on any Azure service based on your needs, including, Virtual Machines, Websites, Cloud Services, Mobile Services, Storage, SQL Database, Content Delivery Network, HDInsight, Media Services and many more.
Use the pricing calculator to estimate how much you could use with £150 of Azure credits. Here are a few usage scenarios that consume no more than £150 per month:

Running 2 small Virtual Machine instances for the entire month, or
Storing 800 GB of data in Storage, or
Developing and testing a web application using Cloud Services, with 3 web roles and 2 worker roles on medium instances, for 10 hours a day, 5 days a week, or
Running two S2 SQL databases for the entire month

Google Cloud give 12 months with $300 of credit, and have some services which are 'always free', broadly similar to Amazon's offering.
If you're careful about your timing, you could also use a spot instance (but be careful that you're not paying more than the on-demand price!). Since spot instances can be terminated at any time if you're outbid, they may not be ideal for learning, as you might not be able to use the service exactly when you want it, but they are often far cheaper.
Students can also claim "up to $110 in bonus AWS credits for a total of $75-$150" with the GitHub Student Developer Pack. Perhaps worth checking if your favourite cloud service has similar offers if you're eligible!
Answer: Turn things off when you are not using them. Tools like www.parkmycloud.com are very helpful.
Comment: That's maybe an interesting service,  how does it work?  What's the cost?
Answer: They are intentionally confusing. Scott Adams coined the term "confusopoly" to describe payment structures so complex that it's impossible to compare two things like for like. Phone tariffs are a great example.
Having recently rolled out some cloud-based infra at my org, the advice I'd give is:

Start tiny and scale up.
Monitor your costs at each step of the way.


Is there a cipher related to colors and letters?

Question: I was just wondering if a cipher existed where a number of symbols were colored with different colors forming a cipher?
Comment: That's merely a question of representation, so you can basically do this with all ciphers that operate on _raw data_.
Comment: **What research have you done?** I'm asking because sharing research efforts helps everyone! Tell us what research you did, what you found, and why it didn't meet your needs. That shows users you took time trying to help yourself, it saves us from reiterating obvious answers, and (most important) it helps you to get more relevant on-point answers. In case of doubt, you can start by searching this site for related Q&As that might shed light on your question. At worst it will help you frame [*"a better question"*](http://crypto.stackexchange.com/help/how-to-ask); at best it might even answer it.
Comment: @Koe - I just thought of the same thing, searched the web and stumbled upon this. It such an interesting idea and I think you deserve many up-v0t3s for putting it out there; thank you. I think there is a way to do this, and I shall make an attempt to make a decryption algorithm for you.
Answer: Something that may interest you would be a secret sharing scheme by Shamir titled Visual Cryptography.
http://www.cs.nccu.edu.tw/~raylin/UndergraduateCourse/ComtenporaryCryptography/Spring2009/VisualCrypto.pdf
Answer: I haven't seen any such implementation of a cipher. That being said, you could implement it yourself. If you take each byte in a cyphertext and put them into a bitmap, you can display each "letter" as a pixel.
Remember, a byte consists of 8 bits, which can represent a number between 0 and 255. Which is one of the most common amount of colors a pixel can hold.
Comment: From my experience, *"the most common amount of colors"* would be represented as RGB which holds **3 bytes per pixel** (red value, green value, and blue value) and not 1 byte as you stated. What you describe would result in a grey-scaled or a custom 256-color-table image format as it was commonly used around and about two and a half decades ago.
Answer:
I was just wondering if a cipher existed where a number of symbols were colored with different colors forming a cipher?

What you describe is not related to cryptography, but practically boils down to a form of encoding a ciphertext.
Cryptographically secure ciphers tend to programmatically output a series of bytes. How you handle and represent those bytes is up to you. Most of the time you'll see binary blobs (read: data packages like files) or - for example when using GnuPG/PGP in emails - somewhat long HEX strings.
So, to answer your question directly: since "encoding" is something completely different than "encryption" and since "encoding" does not add any security, you will not find any cryptographically secure cipher which natively produces an output "where a number of symbols were colored with different colors forming a cipher".
At its best, yet totally insecure for cryptographic use, your idea would result in a kind of (monoalphabetic) substitution cipher; also known as pigpen cipher.
By the way…
Related to your question, you might also want to check on the Q&A "Are specially designed fonts sometimes used in cryptography?" as it comes pretty close to what you are thinking about. To keep this answer short, I'll simply refrain from repeating the same infos which I already provided in my answer there.


Fair use of software in school

Question: Maybe it is a strange question but as a curiosity, if there are pirated softwares installed on our school's computer, is it considered as fair use to take exam using them?
Answer: It's not fair use, but it is most likely not your responsibility. If the copyright holder found out, they might take the school to court, but not you.
Answer: We tend to think of schools, especially below university level, as places run by boards of education, principals, teachers, etc., and the students merely attend. But if anyone ever accused the student of violating copyright by taking the exam, a plausible defense was the student was acting as an agent of the school, and therefore it was the school which violated the copyright through the authorized actions of its agent, the student.
Comment: I think this analysis would not hold up in court for 10 seconds. I am not an agent of a grocery store when I buy things at the store: students are closer to customers. I don't see they are authorized by the school board to do *anything*. They may be compelled, or allowed, depending.

Fair use of software in school


Is it possible to solve VRP using OR-Tools CpModel, instead of RoutingModel?

Question: Is it possible to solve VRP using OR-Tools CpModel, instead of RoutingModel? I want to do synchronized VRP, which is combining vehicle routing and scheduling constraints
Comment: Yes it's possible to use CpModel to model VRPs with specific additional constraints. This discussion in OR-Tools repo could serve as a guide if you're gathering ideas about modeling synchronized VRP: https://github.com/google/or-tools/issues/1047
Answer: The answer is yes. Is it worthwhile ? it depends.
If you just want to have two persons visit the same virtual place (2 duplicated nodes) at the same time, you can force the time cumul var to be equal when using the routing library.
This will probably more efficient than the CP-SAT VRP code as the routing library is highly tuned.
If you want more complex constraints, you can try CP-SAT.
You can look at ortools/constraint_solver/routing_sat.cc to get some ideas.


What is the real meaning of the third precept?

Question: Can someone explain the third precept? Because most are translating this as "sexual misconduct"; but that it so narrow, and distorts Buddhism.
Comment: Please see the answers to these two questions: [Trouble understanding "sensual misconduct"](https://buddhism.stackexchange.com/q/10284/254) ... and [How is sexual misconduct explained in regards to the five precepts?](https://buddhism.stackexchange.com/q/1367/254)
Comment: kamesu miccacara means not just sexual misconduct, but also excessive of sense pleasures. One can arrive at this higher meanings by studying 'Nirukthi'. What it means is finding the origins of key words - as to how complex words are put together using key words.
Comment: i agree with Saptha Visuddhi.most of are misunderstand as sexual misconduct.that is wrong. The "kama sumichchachara" the word kama mean sensual not sexual.
Comment: And these 'nirukthis' are defined by whom? What are the references of these origins? I hope this is not an opinion of a monk who discovered something out of the blue.
Answer: This is to have intimacy with someone under the protection of another. A wife or husband would be protective of each other in appropriate advances by another. A mother, father or family member would also do so.

There are four conditions for wrong conduct in sexual pleasures.
i) There must be a man or woman with whom it is improper to
  have sexual intercourse.
ii) There must be intention to have sexual intercourse with such a
  person.
iii) Action must be taken to have such an intercourse.
iv) There must be enjoyment from contact of the sexual organs.
With reference to the first condition, there are twenty kinds of
  women with whom men should have no sexual relations. They can
  be divided into three groups, namely: women under the
  guardianship of parents, family members, relatives and authorities
  charged with their care; married or betrothed women; bhikkhunis
  and religious women observing the Holy Life. For all women, a
  man forbidden by tradition or under religious rules is prohibited
  as a partner. For any unwilling partner who is drugged or forced to
  have sexual intercourse under threat of violence or coercion,
  conditions (ii) & (iv) exclude them from violation of the precept.

Source: FIVE PRECEPTS (PACASILA) on urbandharma.org
Comment: Do you know (or can you guess) where the list of "four conditions" in that definition comes from?
Comment: Kamesu micchacara veramani sikkhapadam samadiyami-here is the problem.the word "kama"means not only sexual pleasure.its about all the sensual pleasures.eg: adict to watch tv is violating this perspective. Word kama loka does not mean sexual world.so sexual misconduct not the correct answer.
Comment: The 4 conditions perhaps might be from the commentaries.
Comment: @SumindaSirinathS.Dharmasena Just a little question responding your reply. Why the object of breach is woman, if we look at the Sutta, Buddha only mentions women as the object of breach, Buddha never prohibits a married man to have sexual relationship with woman. Why is that?


Sym-linking windows with linux

Question: Is it possible to make a sym-link in linux that can be used by windows? I have a dual boot system of Ubuntu 10.10 and Windows 7 and I want to move my AppData folder to another drive. I was planning on copying the folder to a different drive and then sym-linking to that location, but I cant because a driver is using the AppData folder. Is there a way for my to sym-link the AppData folder?
Answer: Both Windows 7 and Linux's NTFS-3G driver respect symbolic links created with the mklink command on Windows.  For more information on Linux's support of NTFS links and junction points, see this article.
Answer: If I'm understanding the question correctly, you can boot to a Win7 installation disc (or Startup Repair disc), pull up a shell, and move the folder/create your junction from there.
I know ntfs-3g-advanced supports junctions under Linux, but I don't know if it is limited to parsing junctions, or if it can create them.
Bear in mind that this may break the servicing stack (preventing Windows Updates or causing them to fail catastrophically), so keep good backups.

Sym-linking windows with linux


Are linguistic units organized in conceptual categories?

Question: When we perceive something, we tend to categorize it. For example, when we hear the word puppy, we think of the concept of dogs and then the conceptual category of animals. Is it acceptable to claim that linguistic units are organized in conceptual categories?
Answer: Yes, there are many patterns of conceptual organization evident in language.It shows up in all sorts of psycholinguistic effects such as priming as well as in the way language structures are related to one another. One such pattern is represented in the WordNet dictionary relating synonyms, hyponyms and hypernyms in what they call synsets. There is also a pattern of conceptual organization evident in grammar - for instance verbs and nouns differentiate between thing-like and action/state-like concepts. Cases often are used in related areas - e.g. in Czech accusative denotes directionality when not used as direct object. Passive constructions are related to active constructions through the concept of agent-patient, etc.
But the key thing here is that we're not dealing with a single hierarchical structure (something like a Linnean taxonomy). Parts of language are related in all sorts of different ways. That's why grammars are so hard to write - you have to choose one pattern of organization. And it's also why it's more efficient to organize a dictionary alphabetically rather than following some sort of conceptual pattern.
Another problem I've hinted at is with what you consider a unit. Construction grammar will think of both 'rules' and 'words' as constructions and consider them as conceptual units whereas more traditional approaches may only think of 'words' as 'units' to which conceptual relationship can be applied.
But there are also many patterns of regularity in language that are clearly not conceptual (or not primarily conceptual). For instance, apart from some subtle symbolism, most phonological relationships are not conceptual. Nor are some things like patterns you only find by analyzing corpora (such as most collocations). Of course, many seeming regularities in language may just be epiphenomenal or their conceptual underpinnings may not present the same way in all speakers.
Finally, you also have to be a bit careful about what you mean by conceptual. In the above, I was drawing on ideas I think were best articulated in Lakoff's 'Women, Fire and Dangerous Things', Langacker's 'Cognitive Grammar' and Talmy's 'Cognitive Semantics'. Conceptual in this context means related to or embedded in our broader cognitive system described outside traditional approaches (Lakoff made that argument most cogently in the first 5-6 chapters of his book - the rest is just filling in the gaps).
Answer: I think that memory is more 'semantic' than 'linguistic', but, yes, we store these categories.  The larger sets are 'hypernyms' of the subsets (which are 'hyponyms' of the larger sets).  ex: Fido is a puppy.  Every puppy is a dog.  Every dog is a mammal.  Every mammal is an animal.  Every mammal is a living thing. (Therefore, Fido is a living thing.)
Answer: I would say that it is wrong to say that when we hear the word puppy, we think of the concept of dogs and then we think of the concept animal. That suggests a simple stimulus-response model of word recognition which I would say is wrong. Let's suppose that we have successfully heard "puppy" (not "guppy", "puffy", "putty"), then we can access whatever / wherever the mental concept "puppy" is, that is, we will have identified an intended concept. We may or not may not "think of" a specific puppy. Perhaps when you say "think of", you mean "access". We may or may not then access hierarchically related concepts like "dog", "mammal", "animal", "happiness", "paper towel" and so on. With this concept accessed, we have access to whatever other facts we know are also true of the referent.
Saying that linguistic units are organized in conceptual categories implies that the categories exist independent of their symbolic labels, thus the categories "green", "blue" and "grue" (which is the unification of "green" and "blue") exist, even if your language does not have any of these categories. Presumably you see the problem with that. It would, however, be correct to say that when a concept is formed, it needs some (linguistic) label so that you can use the concept. From the standpoint of acquisition, it is most likely that a person will first learn a word and then learn what it refers to, but adults especially can know of real-world things without knowing what they are called (for example "soffit"). In that intermediate period, you can have an awareness that there are these things on / in houses, but you don't know the word "soffit". In that case, I would conclude that you have an incomplete concept, lacking the label that allows you to exploit the concept.
One of the other sides of the coin is the question whether each linguistic unit does represent a conceptual category. It is easy to see that that is not always so, for example with "dog". That refers to at least three distinct concepts. One is a concept of action, of "pestering". One refers to a species of canid; and one refers to a thing that blocks movement (e.g. "feed dogs" on a sewing machine).
Answer: No. But this sort of mentalism is more empty and useless than it is wrong.
Suppose I try to explain the meaning of your question by saying it consists of the concept of "when", combined with the concept of "we", combined with the concept of "perceive", and so on, no one will be the wiser about what you've said.  Such an account is useless.  As to whether it's correct, well, who knows?  Who cares?
If you give such an account supplemented with an explicit version of "combine with", so that you can tell exactly when concepts can combine to give a sensible result, you get the sort of "semantic" theory called Montague Grammar, or Montague Semantics (after Richard Montague who pioneered such theories), and then opinions will differ about whether you're accomplishing anything beyond giving a syntax.  I doubt it.


In DNA replication, are there phosphodiester bonds in the primer ? between the RNA nucleotides before being replaced

Question: When hydrogen bonds happen between the RNA nucleotide bases and the DNA bases , do phosphodiester bonds form between the RNA nucleotides in the primer ?
No source I read is clear about this, are their bonds between the RNA nucleotides ?
Comment: @Dirigible — I suspect that the poster is talking about Okazaki fragments, and wishes to know whether they are covalently linked to the growing DNA. If so, I seem to recall a similar question previously. However the question is unclear. Poster, please clarify your question and preferably present a diagram, or link to one, so we can see what aspect seems unclear to you. The accompanying text would help — it could be that rather than the texts being unclear, there is something in the explanation you are misunderstanding.
Comment: I have posted an answer. However, this seems like a basic question and is easily answered by consulting sources such as Wikipedia. As such I'm flagging this question as ["homework"](https://biology.stackexchange.com/help/homework) since it "addresses a basic biology concept that may seem trivial to biology professionals". ——— Please take the [tour] and then go through the help pages starting with [Ask] questions effectively on this site. Thanks!
Answer: A primer is by definition a short single strand of nucleic acid (i.e. a series of nucleotides linked together by phosphodiester bonds). See also this wikipedia article.


How to resolve a inputfile rerender problem?

Question: I have a VF page to create the cases and to insert the attachments to case.On Changing the picklist values i have to rerender the entire page to enter new values. But I have a inputfile tag in the VF page which doesn't support rerender. How to resolve it?
Comment: Show some VF code please. Why do you need to rerender the entire page ? Try rerendering outputpanels with only the elements that need to be rerendered.
Answer: Rerendering is not supported when you have an apex:inputFile component.  There's no workaround, as the platform simply will not allow it.  The best you can do is to move the apex:inputFile into an apex:iframe which will leave the rest of the "page" alone.
BTW If you are looking to rerender the entire page, that sounds the same as a refresh.
Answer: I have had some success with using multiple <apex:form> tags, one for the <apex:inputFile> and one for the other elements.  I know the docs say it all gets resolved to one <apex:form> but it allowed me to rerender a page with a file input.
Answer: You can also go for apex:actionRegion from here


How can I make a shortcut to search using Google Scholar from the address bar in Chrome?

Question: I don't like having to navigate to http://scholar.google.com/ before I type my search.
Comment: How to add search engines to Chrome: https://support.google.com/chrome/answer/95653?hl=en
Put a `%s` in the URL where your search term is supposed to go.
Answer: It's very easy. Just follow these steps.

Click the Chrome menu on the browser toolbar.
Select Settings and find the "Search" section.
Click "Manage Search engines".
Now add the following URL: http://scholar.google.ch/scholar?hl=en&q=%s
Click the Make default button that appears at the end of the row.

Now you can search directly from the omnibar in the google scholar-section.
Comment: If you can also leave your default search as a regular Google search if you want. After you've done the above steps, you can follow what Xorbyte describes, i.e. start typing "scholar" until the URL appears, then hit tab and input your search.
Answer: An interesting but somewhat hidden feature in Chrome is that it actually siphons visited search engines continuously and provides easy access to their search URLs via the browser preferences.
As an example, right now I went to Google Scholar and did a dummy search ("test"), and directly afterwards I can go to "Settings" → "Manage search engines…",  and now "scholar.google.com" is in the "Other search engines" list with the correct search URL already filled in. The second column represents the keyword, so just click it and enter "gs" or whatever you feel comfortable with, click "Done" and it is indeed done.
It's not difficult to manually add engines for that matter, but this is a nice but not really advertised feature. I follow the "unstable" branch of Google Chrome, but this is not a new function, so it might very well already be in the stable branch.
Answer: If you type the first few letters of the site in the omnibar (say, sch) and tab, the omnibar will change to say Search scholar.google.com and you can type in your text and hit Enter to have it executed.
This works with many other search engines that you may not have added, like Wikis etc; once you visit the site, Chrome remembers it for future use.
Comment: I just get a link to go to `scholar.google.com`, not an ability to search within it.
Answer: I just found out that using duckduckgo you can navigate directly from your search bar using bangs. https://duckduckgo.com/bang
for example to access google.scholar just type
!gsch search engine


How do you choose a CSS framework?

Question: I'm working on a company website and I figure that I should start using a CSS framework. There's quite a number of CSS frameworks around, what's the most commonly used one and why would people choose to use it instead of the other frameworks?
Comment: See http://stackoverflow.com/questions/203069/what-is-the-best-css-framework-and-are-they-worth-the-effort
Answer: First, don't just automatically assume a CSS framework is necessary, or even desirable. Depending on what you're doing and how good you are at markup + CSS, it may not be worth it. The Wikipedia article barely scratches the surface of the debate I've seen online, e.g., this criticism of the YUI Grids framework.
If you've decided that a CSS framework is for you, then you need to decide what problems it will be solving for you. Once you have that list, you can start comparing different ones to see how well they address your problems.
Finally, there are any number of minor factors that may shift the balance for your particular application. Already using YUI on the site? Then the Reset, Base, Fonts, and Grids combo may get a bump, etc.
The two I've seen reference most often are YUI's and BluePrintCSS (here's a comparison).
UPDATE: One thing I haven't seen explicitly addressed by a CSS framework is Setting Type on the Web to a Baseline Grid (see this article on composing to a vertical rhythm for more details).
Answer: You ideally don't.
It's much handier to build up your own ready to go CSS rather than learn the intricacies of a framework. YMMV, but i've found them a waste of time.
Comment: True, but if you find yourself constantly using a similar design structure it can be helpful (and quicker) to either learn a framework, or better yet construct your own.
Comment: I have some basic layout files, basic typography, basic utility, etc. and just @include what I need.......but it's all done myself. MUCH less bloat.
Answer: Afaik, two of the most populars are blueprint and 960 grid system.
Both have their strengths. I like 960gs.
There's another SO question debating the two here
Answer: If you need to build complex grid with no default width limitation, fluid and fixed columns, lightweight, baseline grid, optional semanic, % and positioned based grid my advice is use my CSS Framework Emastic.
If you need something extra simple you can use Malo or something similar to Blueprint or 960.gs but only 1kb weight The Golden Grid. Be careful not always CSS Framework is good idea. I also wrote one post about When to use CSS framework?
Answer: Compass is an interesting looking CSS framework.  It can run using blueprint, 960.gs, YUI and probably others as a basis, but just pulls in what is needed for your project.
Answer: Forget about frameworks, use XCSS. You will love to write stylesheets again.
Answer: I've used YUI, BlueprintCSS.
In the future I would consider using 960gs, but most likely would use twitter bootstrap https://github.com/twitter/bootstrap/
Comment: Bootstrap is nice for quickly building a website from scratch. Once you get to the point of customizing the style you should probably pick something less 'bloated'.
Answer: I still need to diversify my experience with CSS frameworks but the one I've worked with the most is the YUI CSS library.
It's a four part setup - consisting of a reset, grids package, fonts setup (not entirely sure what the pros of using that are) and a base stylesheet which applies some basic formatting. You can choose which parts you want to use and they're available to use from a CDN on Yahoo! and Google.
I like the YUI library because it provides an easily switchable layout (just by changing one class or id of the container wrapper) - for example yui-t4 provides a 180px column on the right, yui-t3 provides a 300px column on the left - these templates also take ad-block sizes as well which is useful.
The base markup isn't too bad either:

<!—-overall document wrapper-->

How do you choose a CSS framework?


How to calculate potential enegy of manipulator?

Question: I'm trying to obtain dynamics of a 4 DOF robot. Firstly, I calculated all Transformation matrices and Jacobians. While solving Lagrangian there is two main things one is kinetic energy and the other is potential energy . The kinetic energy is simplified into D matrix and Coriolis's factor, which to find the gravitational factor in lagrangian method , we need to find the potential energy. My problem is in that potential energy which is equal to P=mgh . I don't know what does that h correspond to and how to find the value of h .
Could some one help me solving this issue ?
Answer: The height h is a height relative to some arbitrary baseline. You can set it anywhere you want, but I think typically the easiest way to choose your baseline height is to set zero as the lowest reachable point for your robot. Then all heights are positive and you can have zero kinetic energy when speed is zero and zero potential energy when your arm is at its lowest point.
:EDIT:
Based on your graphic, it looks like $F_1$, your first joint, is at the top, so you've drawn the arm with as low of a reach as it could have. That means the $h=0$ datum should be through the center of the bottom joint (or center of mass of the end effector, but you don't have a Frame 5 $F_5$ depicted):
Comment: Ok but How to find that h value because I saw the value of h in a form of expression with cos and sin thetas .  Because we need to differentiate that whole potential energy with respect to (q) for lagrangian formulation where the (q) is available only with that h expression (as cos(q) ,sin(q)) .  So can you help me , how to find the value of h ?
Comment: @RAKESHKUMARK - Put the arm at its lowest possible position. This becomes the `h=0` datum. Then you measure `h` as the **vertical** distance from that datum. You'll wind up with whatever expressions are necessary to convert your robot arm's positions to **vertical** distances.
Comment: Sorry , Can you explain me in a more elaborate way?  This is my first attempt towards Robotics , so kindly help me . The motive is doing dynamics using Lagrangian formulation. In that how to calculate the potential energy ?
Comment: @RAKESHKUMARK - If you don't provide any drawings, then no, there's nothing more I can say. Please *edit your question* to provide a drawing of your arm in its normal state, and in its lowest-reachable condition, and include any joint and linkage labels, datums, polarities, etc.
Comment: yes , I added my picture . Can u please explain me now how to find potential energy clearly?
Comment: I have edited again my question with my clear motive of doubt sir, so now what will be the value of the four h ? Since they are getting derivated with respect to theta how could i able to calculate it ? Help me please


Effects of horizontal vs. vertical motion on human body

Question: I want to know if moving along a vertical plane in a circle differs in its effects on the human body from moving horizontally in a circle. Imagine a ferris wheel with a diameter of 50 metres. If a person on it was travelling at 10miles an hours, would they get less dizzy than a person travelling on a roundabout or carousel with a diameter of 50 metres travelling at 10mph?
Answer: Accelerations are sensed by your vestibular system located in your inner ear, more specifically the otoliths for linear accelerations. Your question is not very clear because you do not specify how exactly people would be moving, but let me try to answer anyway. First, in theory the otoliths detect accelerations only, so as long as you move at a constant speed in a constant direction you do not perceive your own movement (thanks, otherwise you wouldn't be able to stand being in a car, train or plane). Second, if you move in a circle horizontally it's different, and how different depends on your orientation. If you always look in the same direction, your acceleration will be a cosine function in the orientation of you head, and a sine orthogonal to your orientation (so you perceive the same as if you were on a sledge that moves back and forth and right and left, obviously as such a sledge would therefore be moving in a circle). But if you look in a direction tangent to the circle, then you are back to the case of constant acceleration and don't even perceive your own motion. Third, vertically it's even more different because of gravity. Gravity  is a constant acceleration toward the earth. So you always perceive it (that's why you know the orientation of you head even with your eyes closed and even if you are not moving). So this is similar to a horizontal circle, except that it would add up to the constant pull from earth gravity. Finally in space there would be no difference between the 2 cases.
That might sound complicated, but take the example of rotations (rotational accelerations are processed by the semi-circular canal but lets neglect that). If you spin at a constant speed horizontally (alongside the vertical axis), you wouldn't be able to tell you are spinning because your acceleration would be constant. But if you spin vertically (alongside a horizontal axis), then you would always perceive you are spinning because you would always be able to perceive earth gravity (as it is an acceleration) and you would presumably get very nauseous. And again, in space there would be no difference.
Answer: The inner part of your ear contains fluids that controls how dizzy you feel, with no consideration for direction. I believe astronauts feel dizzy for the initial day or so, before their body adjusts to liquids, if that helps you visualize it. However, on earth, I'd be inclined to say that horizontal would be better due to gravity and the direction the normal force of the fluids is pointing, but I could totally be wrong. Hope that helps.


Recovering your Microsoft Flight Simulator X CD Key

Question: I had purchased and installed Microsoft Flight Simulator X Deluxe on my machine, but uninstalled it since I never used to play it all that much. Now I want to reinstall it, but I have the Disks but not the Key stickers. I've lost those. Is there any way to recover my CD Key? Does Windows 7 store the CD Key anywhere like in the registery or elsewhere from where I can get it back. Anything else I can do?
Answer: You may contact Microsoft store with a purchase proof and maybe they provide you the keys. Is not a sure method (most stores doesn't allow you to re-download/re-licence content for robbery or lost) but it worth a shot.
Remember to always backup your keys in a secure place, twice.
Answer: One resource that you can use to find your lost key is Belarc Advisor. It will basically scan your computer for all the programs that you have installed and shows them in a detailed profile. This includes any CD keys that you have entered in to your computer. The website can be found here, however it is somewhat complicated to read at first glance, so don't expect it to be a cake walk.
Comment: Unfortunately, it does not show the CD Key I used for FSX :-(


What is the name of this tree found in Switzerland?

Question: What is the name of this tree?
They are quite common in Switzerland.

The second picture refers to Lugano. Here a couple of pictures in summer (with leaves):
Answer: I'm not sure what species the trees are (or if the two photos even show the same species), but what gives them the distinctive look is a pruning system called pollarding. It is generally done in urban settings to keep trees from getting too tall or broad, and the visual impact can be quite stunning. According to Wikipedia, only species with vigorous epicormic growth may be made into pollards. I've seen it done to London plane trees several times.
Here's a question in G&L that covers this pruning technique in more detail.
Answer: I grew up around Lake Geneva and we called the ubiquitous urban trees, especially for these alleysways, the "platane".
This article (in french) names the species as Platanus hispanicus, a hybridised form of oriental and occidental species (they probably meant Platanus x hispanica, which confirms That Idiot's identification as London plane).

This tree is widespread (5600 in Geneva alone), even though it is an exotic, due to its tolerance of urban environments - heat, pollution or damage to the bark.
The above cited article explains the origin of pollarding in Geneva as to preserve the servitudes of views to the lake from lake side residences. (I just discovered, researching this question, that pollarding is called "en tête de chat" in french, i.e. "pruning in a cat's head", which i find amusing).
It is also encountered unpollarded, quite a handsome tree. Here at University of Lausanne (Dorigny)

or the Geneva botanical garden

Your question made me nostalgic of Switzerland - i had never realised how ubiquitous and emblematic of Swiss cities it was. Thanks for that wooghie!
Comment: The bark looks wrong.


how to snap 2 specific points

Question: I'm trying to make a low poly lantern of some sort and I want to get a frame. To do this i'm trying to get cylinders to line up with the edges of the bottom of the lantern however when i try to snap the cylinder it is facing the wrong direction how can I A) get the cylinder to face into the lantern instead of hanging off the edge and B) how can i make sure that it is centered so that it isn't skewed off to one side or another (basically how can I make it so that all the vertices are lined up straight)
Comment: Hmm... Could you zoom out and get some more pictures? I think I have a few ideas... It looks like your 3D cursor is not centered, maybe snap it to the world origin first? Perhaps I don't quite understand.
Answer: Basically you want to use the 'Snap with Active' part of the snap feature. The active element is highlighted white by default instead of orange, and it is the individual vertex/edge/face you most recently interacted with. If you need to set your active vertex to something new, deselect and reselect that vertex.

Then it's just a simple matter of selecting the correct active vertex and snapping your mesh into place.

how to snap 2 specific points


What is tofu that's crispy outside and fluffy inside called?

Question: I sometime eat asian dishes having tofu cubes. The tofu looks a bit fried, it is a bit crispy on the outside but quite soft and fluffy inside. I love this texture combo, I would eat a whole wok of it! Unfortunately I know neither how this kind of tofu preparation is called nor how it is made. What is the name of this preparation style so I can learn how to make it myself?
Comment: Welcome, Stphane -- recipe requests are not on topic for this site, so I have tweaked your question a bit to ensure it isn't closed. Hope you find what you're looking for :)
Comment: Sharing a link to a [video](https://www.youtube.com/watch?v=9WN3knltIos) might be relevant.
Answer: Traditionally, it's first dropped into boiling water & allowed to sit as the water cools for 15 minutes before drying off & deep frying.
There's a 'cheat' method, though.
Press to dry, sprinkle with a little cornflour & shallow fry, on its own. Add to the dish when cooked. Dress with anything you fancy - chilli, soy sauce, sesame oil, rice wine vinegar...
It's not quite the same as deep fried, but it's a whole lot quicker & easier.
Start with firm tofu; otherwise you'll have to give it the 15 mins in boiled water to firm it up.
Edit: The question changed direction slightly after I'd posted this - as to what it's called; other than 'deep fried' or 'crispy' tofu, I really don't know.
Answer: This sounds like fried tofu puffs.
Comment: While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference.  Link-only answers can become invalid if the linked page changes. - [From Review](/review/low-quality-posts/66424)
Comment: The question is "What is the name of this preparation style". I thought I'd answered that, whether or not the link works.
Answer: My understanding from watching it being cooked is that it's fried hot and fast in a lot of oil. The tofu itself seems to be a firm variety  and the outside dries and crisps from the hot oil. As the inside heats up some steam will be formed, and I think this is what makes it fluffy.
I've never managed to replicate it myself except for a few test pieces - I suspect I'm being mean with the oil and my wok isn't really hot enough to start with (domestic wok rings aren't as powerful as commercial ones), so adding a lot of tofu drops the temperature too much. Deep frying might work but the rest of a typical dish would need stir frying and I'm not set up for deep frying so I've never tried it.


how to get a smoke domain and flow object to follow a parent that is driven by a rig following follow path bone constraint?

Question: Figured it out before I finished asking, see below for answer, but i'm going to have to continue typing so that my question meets the minimum amount of characters...hmm will this be enough.
Answer: For anyone else who might stumble on this problem, there's nothing different you need to do, but like me you might be thrown off by the viewport showing the smoke sim stuck at frame 1 with the domain not following along with the object, and the smoke sim not updating.
All you need to do is parent all of your smoke objects to any child of the rig that has a path follow constraint (which you've probably already done), and then select the domain and click bake. It will then bake properly. The problem is only that blender tricks you into thinking you've done it wrong for a few hours by giving you the completely wrong result in the viewport unless you bake.
Hope that helps someone.


When football players played offense and defense, what were the substitution rules?

Question: My Dad played high school and college football in the 1930s.  He and the other starters played both offense and defense.  What prevented a team from putting out 11 fresh players at once when the ball changed sides?
Answer: Wikipedia covers this reasonably well.
In the first era (what you're talking about, basically) of the one platoon system, there weren't really rules about substitutions, but there was a major limitation: the size of the team.  You didn't have 80 player teams back then.  In the 1940s, a few teams (notably, Army) started the two platoon system (what we have now); but even before that, some used substitutions (for example, Knute Rockne).  So during your dad's day, it was a combination of financial reasons, athletic talent, and simply the fact that it wasn't done.  (Remember, this was still somewhat of a "gentleman's game" at the time, primarily a college game, and so things like "honor" were very relevant to the coaches and players.)
Then in 1953 this was outlawed, allowing only one sub per play, partly in order to reduce the cost of fielding a team.  This was changed in 1964 to return to allowing two-platoon football, which is what we basically know today.

According to this page of NCAA rule changes, the following rules changes occurred over the years.  I cannot substantiate all of the individual details, but the ones I can (1941, 1953, 1965) are consistent with what I've mentioned above.

SUBSTITUTIONS:
1876--Fifteen players to a team and few if any substitutions.
1882--Replacements for disqualified or injured players.
1897--Substitutes may enter game at any time at discretion of captains.
1922--Players withdrawn during the first half may not return until the second
             half.  Players withdrawn during the second half may not return to
             the game.
1941--Players may substitute at any time but may not be withdrawn or the
             outgoing player returned until at least one play has intervened.
             "Platoon" football made possible.
1948--Unlimited substitution on change of team posession.
1953--Two-platoon abolished and players allowed to enter game only once in
             each quarter
1954-64--Changes each year toward more liberalized substitution and platoon
             football.
1965--Platoon football returns.  Unlimited substitutions between periods and
             after a score.
1974--Substitutes must be in for one play and replaced players out for one
             play.
1993--Players who are bleeding or whose uniforms are saturated with blood
             must come out of the game until their return has been approved by
             medical personnel.
Comment: There were substitution limitations similar to soccer and weren't waived until the 1940's.
Comment: @JeffO If you can find a link substantiating that, please edit it into the answer and/or post separately.  I never could find a link substantiating that as a rule itself; Knute Rockne, for example, supposedly made mass substitutions with his starters replacing backups, though it doesn't say how many (but "mass" seems to be more than the number you'd allow in soccer).  All I read seemed to suggest it was more the custom than the rule (to limit substitutions pre-1940).
Comment: @JeffO I did find something slightly better.  It doesn't quite agree with you about the limitations pre-1940, though; the 1922 rules seem very different from soccer, but are 'somewhat' limited at least.


Share iPhone Personal Hotspot with Mac, then share Internet via ethernet

Question: When I'm travelling I only have Internet via my iPhone, which I can share to my Mac via Personal Hotspot just fine. However, I have a VoIP desk phone which only gets internet via ethernet cabling.  I have tried plugging the phone directly in to my Mac, and then turning on Internet Sharing to share the connection from Wi-Fi to the ethernet ports.  But the phone does not pick up any connection.  Is this possible and how can it be done?
Answer: Not a networking expert, but I tried using a switch in between the Mac and the VoIP phone, and it worked! No idea why the VoIP phone wouldn't work when plugging directly in to the Mac, but oh well - very happy!
Answer: I've had a lot of experience using internet sharing under OS X. For inexplicable reasons, it's quite unreliable. Internet sharing also jumps around between OS X versions. What works in 10.5 might not work in 10.6 which might not work in 10.7, all the way though 10.10. Your trick of putting a switch in between is a good hack.

You could also try using mobile router as an access point. It would be a client to your phone's hotspot and then offer ethernet to both your VOIP and your Mac. This offers the benefit of being able to make calls with your Mac either absent or turned off.
Comment: True, and thanks. However, all I had was the equipment I had there, and luckily the switch did the trick!
Comment: Great. I've done a lot of networking. I used to be stubborn and try to just make do with what I had but I've learnt that it's much more efficient to buy an extra switch or router (even buy a drop-in backup) than to try to make edge software situations work. It's partly the drop in quality in [Apple's core code](http://macperformanceguide.com/AppleCoreRot-intro.html), partly how much the price of reasonable quality networking equipment has fallen since Chinese manufacturers like TP-Link have entered the market.


What was the topological constant which Gauss derived in the context of his investigations in electromagnetism and knot theory?

Question: My question refers to the following problem in electromagnetic theory which Gauss was concerned with (see Zur theorie der electrodynamik, volume 5 of Gauss's werke): Determine the work done on a magnetic monopole of strengh m when it is moved along a closed loop L_1 in the magnetic field produced by a closed current loop L_2 with current I. This problem led Gauss to the introduction of the Gauss's linking integral for computing the linking number of two interwinged loops. According to several books, this integral is constant under derformations of the loops as long as their number of interwingings is constant (so it's a measure of the degree of entaglement of the two loops). I'm trying to understand what was his result (what was his topological constant) and also what is his meaning, because according to several books is has an advanced physical meaning (the Gauss's linking integral is an advanced analytic tool).
Comment: So what is your question? You tell us that you are trying to understand the Gauss linking integral. But what is your specific question? Are you asking about references or what? From your message I infer that you know some references.
Comment: My first question is: what is the topological constant that he found? I guess it's in the form: 4n\pi*C, where n is the number of interwingings, and C is a constant that is a function of physical constants (like \epsilon_0) and m and I (strength of the magnetic monopole and the current in the loop). My second question is: what is the meaning of this complicated analytic formulation? and how it's connected to later developements in physics?.
Comment: Perhaps i should clarify why i'm asking that question. With my current level of mathematical knowledge, i'm unable to read and understand all the articles i found (i have references), but i'm very curius about this subject and wants to hear an explanation from an expert  or at least from someone with better knowledge than me. I wasn't even able to infer what was the result for the topological constant.
Answer: I would suggest the following paper:
http://www.maths.ed.ac.uk/~aar/papers/ricca.pdf
it contains a quite detailed analysis of Gauss original works in modern terms.
The linking number appears in computation of so-called helicity of vector fields, and in this form it is often applied to magnetic vector field.


1/4 cup of rice not measuring to be 45g, turns out to be 30g

Question: I have used two different rice cooker measuring cups, and I know the kitchen scale is correct, but the rice packaging for various rices say 45g = 1/4 cup, but if I fill it up to 1/4 cup, the weight of the rice turns out to be 30g. What am I doing wrong? I even put a little more than 1/4 cup but still it's like 32-33g. I know different grains weight different, but I think 15g off is too much right?
Comment: If the rice package don't come with a cup use weight not "cups". How the hell they would now what cup you're using? How you would know what they used?
Answer: The measuring cups that come with rice cookers are not the same size as a US cup (or indeed many other countries' cup measurements).
A rice cooker cup is 180 ml, a US cup 240ml, and in a lot of places it's 250ml. This is because rice cooker designs originate from Japan.
You're getting 30g, which is 2/3 of what you expect. For a US cup, 3/4 would be right, and for a 250 ml cup, 72%. That's probably close enough given how much variability there is in packing rice into a cup, especially as grain shapes vary.
Comment: I just did a bit of empirical testing. My rice cooker cup measures 35g for 1/4 cup. My American cup measures 45g for 1/4 cup.


How to implement the travelling salesman algorithm with dependecies between locations

Question: Is there a way to implement the traveling salesman or purchaser algorithm with constraints between locations? For example, I have to grab item X before item B, c before D and F,G,H in any order.
Comment: Well, Traveling salesman is NP, so you have to try every route anyway. Adding a check "grab X before B" won't affect the complexity.
Comment: @Sjoerd: the OP did not state he wants a perfect solution. And finding "good" instead of "perfect" solutions is not NP hard.
Answer: Wikipedia lists several approaches for exact and heuristical solutions for the standard TSP. Any of those approaches explores the space of solutions and partial solutions in a special order. So I guess most of them (maybe all of them) can be extended by restricting the search space to those (partial and full) solutions which fulfill your additional dependencies.
As a simple example, the nearest-neighbor heuristics normally picks one location after the other, and it picks always the nearest unvisited location. Now extend this by the additional constraint of picking the nearest location except B, as long as X has not been visited before.
Of course, for finding really good solutions which are near the optimum, you need to implement something more sophisticated like simulated annealing, restricted to the search space of (partial) solutions fulfilling the list of constraints.
Answer: If you have only one dependency, "grab item X before item B", then the solution is trivial.
Find the shortest possible route. Either you encounter X before B on that route, or you travel the route in the opposite direction.
Comment: @SaadK: ask a better question, get a better answer.
Comment: No its not just X before B, I have multiple points
Comment: @DocBrown True :)
Answer: As far as I understand your question, the problem that you are trying to solve has been studied under the name of traveling salesman problem with precedence constraint, this could constitute a good starting point for your search.
If you solve the problem with Mixed Integer Programming, you can add an Integer variable to each node representing its sequence. The sequence of the depot is fixed to be 0. For all other nodes if s_i represents the sequence of node i in the solution and if x_ij is a binary variable representing whether or not the arc between nodes i and j are used, then we can add the following constraints:
s_j >= s_j + 1 - M * ( 1 - x_ij), for all pair of nodes i,j
Where M represents a large enough value.
Then if A should be visited before B you should add a constraint stating s_A < s_B


Maintenance mode without maintenance.flag

Question: I have a problem. My magento puts itself to maintenance mode without maintenance.flag. At this time i did not do any installations or backups. Last time this happened i restore the database to last day and all was ok, but now i cannot restore database to the day when magento is working.
Comment: Are you using Redis sessions?
Comment: I am not using Redis sessions. Last extension i was installed was Lesti Fpc, i unninstaled it, but nothing happened.
Comment: Could it maybe that your `index.php` file is modified? It might contain a manual PHP switch to skip the check for existence of the `$maintenanceFile`?
Answer: The Maintenance mode is just an include of the "503.php" which is located in the errors directory of your Magento installation. There exist only two possibilities when this file is going to be included:

the maintenance.flag file exists in the root directory of your magento installation (see index.php)
you are using Redis and expired the maximum of concurrency connections

As you already mentioned, none of these cases match your problem.
Maybe an extension will raise the maintenance mode by including the errors/503.php of the errors directory. Please search all your (custom) code for "503.php". It is possible that some of your extensions need another resource which is not present.


A three-day carriage ride, how long would other methods take?

Question: If my carriage can cover about 28 miles in an 8 hour day of travel because the roads are in very good conditions, how fast could someone on horseback take? How about someone walking? Would the speed of this person be different if they're not used to riding or walking on a regular basis?
Comment: I have on very good authority that the speed of this person is considerably slower if he is not used to walking on a regular basis.  Slower yet if there are intriguing distractions en route.
Comment: For clarification, what is your exact tech level?  Carriage could imply a setting anywhere from the late bronze age all the way up to the middle of the industrial revolution.  Also, is your goal to travel ~84 miles or to send a message to someone that far away, since the latter has some additional options.
Comment: Roman legionaries on good roads would march 30km over around 6 hours with a load of around 20kg. This was considered the standard pace. Then there were also faster paces. Of course a 18th century gentleman on a stroll would pace differently.
Comment: Those these answer your question? https://worldbuilding.stackexchange.com/questions/124606/how-far-can-you-travel-on-horseback-while-pushing-the-horse-to-the-brink
Comment: Surely you can Google walking and horseback speeds?
Answer: It's really not possible to give a definitive answer, since it depends on the fitness of  the horse, or the person walking/running.
At an extreme, both elite & well-trained horses and humans can do 100 mile endurance races on mountain trails in 12-17 hours (Tevis Cup winning times: http://www.teviscup.org/results/tevis-cup-winners Western States 100 times: https://en.wikipedia.org/wiki/Western_States_Endurance_Run#Results Both races are run over the same trail.)
So from simple math, a very well-trained runner or horse & rider could do that distance in 9-12 hours. Someone who is basically fit but unused to walking any distance might take a week or so.  An untrained rider on an out-of-condition horse might take even longer, as the horse will need rest and recuperation too. (Even doing much shorter rides - 20-25 miles at most - I give my horse at least a day off between rides.)  An untrained rider is also going to be in considerable pain after the first couple of hours.
Of course, this is for an individual.  If switching horses frequently, a person could cover distance much faster.  E.g. the American Pony Express did around 10-12.5 mph, changing horses every 10 miles: https://en.wikipedia.org/wiki/Pony_Express
Comment: Hmph guess I should have put my Pony Express comment here :-)
Comment: No thanks :-) I didn't  know about it. :-)
Answer: Express Horse
Fastest way to move is to ride horses like hell and exchange them every few kilometres on a horse change station. Assume you can make 30km per hour like that.
It then just depends on your personal fitness how far you can get.
Oh and yes. You have to be rich enough to set up those horse change stations on the route. Wow that's huge cost! Imagine in modern world words, buying a car for every 15 km you want to travel and let them park and get maintained by someone.
I think it's a thing you could do to send messengers to your army from the capital and back while you're at war, but for anything else it might be too expensive.
Counts Thurn and Taxis did set up a subcontracted carriage relais system around 1490 or 1500 on most of the important routes through europe for fast messaging and travel. It was, in the end, the invention of the postal service.
Walking
People on a good road made between 10 and 15 kilometres a day. That's not because they were lazy. You could think "eh after all, I can make 15 kilometres in 3 hours easily". It is because you have to transport all your stuff on your back, and you have to sustain the speed for 10 days. (38km x 3 divided by 15, roughly 10)
If you exhaust yourself the first day, you won't make any advance on the next two days, losing more than you win. Add a suboptimal spacing of sleeping taverns and you rather decide to stay here early in the afternoon than to risk the next house. No streetlights also means there is real darkness, you don't want to risk that.
That said, after having read Duncan Drake's comment, I checked Wikipedia for the roman legions. They indeed made 30km in 6 hours according to Wikipedia, and that was their day's march. Of course, they were trained and well-fed. I can't imagine that everybody can do that.
Fitness
I am currently building my fitness up back from a chemotherapy-induced nothingness. I do it by walking. Normally I am a lazy bureau-sitter.
During the chemotherapy, on the lowest level of fitness I ever had in my life,  there was 2 km maximum per day. It just wasn't possible to do more.
Bureau without sport, 1 year later: 8-9 km at a speed of 4km per hour. I was so darn exhausted in the evening that I would fall asleep sitting.
Today, not really sporty but building up towards something healthy: I do 12-14 km each day, speed around 5 -7 km per hour. Not specially exhausted in the evening. (But I am not wearing my household on my back)
Comment: True fact: the highly romanticized Pony Express set this up, and went out of business in 18 months due both to high operating cost and the completion of telegraph networks.
Comment: I think 10-15km as a walking estimate for a determined person is on the low side, I know a number of people who walk 5km each way to/from a full-time job and it doesn't exhaust them. 10-15 miles might be closer to the mark.


Is iPad Pro with Pencil the best route to take for drawing custom icons?

Question: I'm looking to make the investment in a drawing tablet. I've looked into Intuos, but have never played with it. I played with the ipad pro and pencil and really loved it. What are some of your experiences with either product?
Comment: Not all people have a workflow that benefits form tablet input. For me this is especially true when creating icons. So if you are alleeady doing icons by drawing on paper then digitizing them then yes this may benefit you.
Comment: Good points @joojaa
Comment: I've done a handful of paper drawn items, but in the recent months, I've been doing more of it, so that's why I want to explore tablet options, to take one less step out of the process
Answer: Only you can really say what is best for you.  Best is highly subjective.
You can't run Adobe Illustrator on iOS devices.  It only works on Macs and Windows.  There's the Illustrator Draw app for iOS and Android tablets, but it's not the same thing as Adobe Illustrator. However it might be fine for your purposes.
There are Wacom Cintiques which run a full Windows operating system which could run Adobe's Creative Cloud products, including Illustrator, Photoshop, etc.
Wacom Intuous tablets have no integrated display, they are only input devices.


What kind of operations can we do with bits?

Question: I wonder if there are more things we can do with bits aside from NOT, AND, OR, XOR operations? I got this question from my teacher and I'm not really sure. How about bit shifting ">>"? Could we count this?
Thanks for replying.
Answer: If you think about it, there are $2^4 = 16$ possible ways of combining two bits to give a single-bit ouput (AND, OR, NOR, NAND, XOR, ...).  Can you work out what they all are? This is because there are four possible input combinations ($00$, $01$, $10$, $11$) and any subset of those can be mapped to~$1$.  But we could combine more than two bits to give a single bit output – can you work out how many operators there are that take $k$ bits as input and output one bit?
And we're not even restricted to one bit of output: in general, we can have any number of bits of input and any number of bits of output. You mentioned shifts, which map $k$ bits to $k$ bits, as an example of this.
Overall, there are infinitely many ways of combining bits.
Comment: Thank you, now I see I got a little bit narrow-minded with this topic ;)
Comment: Ages ago, Windows had one graphic operation that combined four single bit inputs - 16 possible inputs, 65536 different functions.
Answer: Classifying the bit operations comes up when investigating special kinds of operations, like reversible bit operations or falsehood free (classical) logical operations.

Formally, a reversible gate is just a permutation $G : \{0, 1\}^k \to \{0, 1\}^k$
  of the set of $k$-bit strings, for some positive integer $k$. The most famous examples are:

the 2-bit CNOT (Controlled-NOT) gate, which flips the second bit if and only if the first bit
  is 1;
the 3-bit Toffoli gate, which flips the third bit if and only if the first two bits are both 1;
the 3-bit Fredkin gate, which swaps the second and third bits if and only if the first bit is 1

In similar terms, a falsehood free logical operation is just a Boolean function $f : \{0, 1\}^k \to \{0, 1\}$ with $f(1, \ldots, 1) = 1$. Before starting to omit logical operations, one can try to list as many logical operations as barely reasonable:

If we limit ourself to constants, unary operations, and binary operations, then we get:

Constants for truth ($\top$) and falsehood ($\bot$)
An unary operation for negation ($\lnot$)
Binary operations for: or ($\lor$), and ($\land$), implication ($\to$), minus ($-$), nand ($|$), nor ($\overline{\lor}$), equivalence ($\equiv$), and xor ($\oplus$). The remaining binary operations add nothing new: reverse implication, reverse minus, first, second, not first, not second, true, and false


Adding fmath editor plugin to ckeditor through wysiwyg module

Question: How to add fmath editor plugin to ckeditor through wysiwyg module.
The link (http://www.fmath.info/plugins/drupal/doc.jsp) provides documentation for ckeditor module but it does not explains the steps for wysiwyg module.
Answer: This started out as hacking it in, but things are always nicer in a module. The code is on my Github but if you just want the module it is hosted here for the moment. Full install instructions are similar to your link above and are including in the README for the module.
Basically, if you have the Wysiwyg CKEditor module installed already, you'll need to:

Install fMath plugin:
Download the plugin for CKEditor from the fMath site
and unzip the package.
Copy the folder fmath_formula to sites/all/libraries/ckeditor/plugins folder
Install the fMath WYSIWIG module (linked above):
Download and add the module to Drupal and activate it.
Enable the fMath button in the WYSIWYG profiles page for the wanted formats (e.g. Full HTML).
Now, the button on toolbar should be displayed. When you click the editor, it should show up.
You will not be able to save the image to the page until you complete the next steps.
Install the server side script to generate the images:
Go to www.fmath.info/editor/ and download editorPhpServerSide-vx.x-x.zip
Unzip the file.
Create on your server a folder "capture", it must be available from www.yourserver/capture
Copy the file imageCapture.php to this folder, it must have the permission to execute.
Create a folder img in capture folder (capture/img).
Edit the file imageCapture.php and change www.yourserver.com with your server url
Edit the file sites/all/libraries/ckeditor/plugins/fmath_formula/dialogs/configMathMLEditor.xml
to add or edit the property "urlGenerateImage" to
http://yourserver/capture/imageCapture.php
Test
Clear the cache of your browser (temporary files).
Create an equation and save.
Comment: Over a year later: now a Drupal sandbox project http://drupal.org/sandbox/incarnated/1956172