How do I message Google Document collaborators?

Question: When I'm collaborating with others on a single document I'd like to be able to send them messages as I would in a chat client but without switching between windows. I can't see a way to do this from inside a document, is it possible?
Comment: You now about the _Chat_ pane, right? In the top right corner of the document window, next to the _Share_ button, there's a _Chat_ button as long as your document is shared. This allows you to chat with people _currently viewing the document_, at least.
Answer: There is a built-in chat, which as far as I can tell is only accessible when multiple people have a document open.  At the top-right corner, next to the "Comments" and "Share" buttons, there should be a chat icon.

The chat icon appears when another user opens the document.  It seems that when all users except you have then closed the document, the icon temporarily remains, but then disappears if the page is reloaded.
Answer: The only way I know to notify collaborators in a way I am certain they will receive without opening the document is to use the menu option: File > Email collaborators...


Why do we always use square kernels for filters?

Question: In image processing, why do we always use odd square kernels(3x3, 5x5, 7x7, etc.) for filters?
Why can't we use kernels of size 3x1, 5x3, etc. that are rectangular kernels? Also, why do we not prefer even kernels (2x2, 4x4, 6x6, etc.)?
Answer: If the kernel is odd then you can center it on top of a pixel, which is nice. Lots of kernels are symmetric, so that's probably why they are often square. You can certainly use non-square or even kernels though.
Answer: You can use whatever size of kernel you like. The kernel is not necessary to be a square especially when you want to pay more attention to process along a specific orientation. In fact, moving average along a specific axis in a image is a simple filter with rectangular shape.
Gaussian filters, probably one of the most used filters in image processing, are based on gaussian function in which the top value is achieved on the axis of symmetry. This is the main reason why such kinds of kernels are preferably to be odd.
Kernel size selection is often supported in the filter kernel options in the image processing packages, such as all the imfilter related functions in Matlab image processing toolbox. Yet I would also like to take an high-pass filter example if you design the filters by yourself. For a square kernel with odd dimensions, the value for all filter weights can be set to a negative value, except for the center cell, which has a positive value which increases with the size of the kernel; A square kernel that has even dimensions has the positive value in the central group of four cells; A rectangular kernel has a center group of positive value cells in proportion to the kernel's dimensions. They all work as a high-pass filter.
Answer: You don't. This must be the consequence of a special implementation. Convolution is defined in all these cases.
Answer: Okay, so what is the source pixel? It is the anchor point at which the kernel is centered and we are encoding all the neighboring pixels, including the anchor/source pixel. Since, the kernel is symmetrically shaped (not symmetric in kernel values), there is equal number (n) of the pixel on all sides (4- connectivity) of the anchor pixel. Therefore, whatever this number of pixels maybe, the length of each side of our symmetrically shaped kernel is 2*n+1 (each side of the anchor + the anchor pixel), and therefore filter/kernels are always odd sized.


Saturation region in nmos

Question: If in the saturation region the inversion layer is pinched off then how do electrons flow from source to drain?

Doesn't pinch off of inversion layer mean the loss of channel in the MOSFET for current flow?
Answer: Why MOSFET Pinchoff occurs This answer will help you!
You are right about the channel getting pinched,  so how will electrons flow!? However, also keep in mind that there is electric field setup too! And force due to this field, pushes the electrons to the drain. Read the answer posted by Vasiliy, it will clear you doubts!
Answer: Being in saturation does not mean a mosfet is not conducting current.  It means the drain current no longer increases with increases of Vd.

Don't confuse pinch off with turning the device off which you would do my making Vgs zero.
Comment: thanks for your answer but if the inversion layer is pinched off how does current flow through the pinched off region?In first case Vgs is zero due to which the there remains no channel for current to flow and in the second case the channel does not completely connect drain and source because of pinch off.Don't the two cases look same.
Answer: At saturation mode N-MOS turns to current source mode (infinite source-drain resistance). It is still possible small changes in source-drain current due to channel length modulation.
Comment: What his question means is that if the inversion layer is pinched off, it doesn't reach the drain. So how will electrons flow if the channel itself is pinched or "broken"

Saturation region in nmos


Google Sites as Wiki--Discussion Option

Question: We are using Google Sites as a wiki. I wonder if there is a way to run a discussion behind the scenes as can be done in Wikispaces. If so, how would you do this with Google Sites. We are all already in as collaborators and are creating our pages. How can we have a behind the scenes discussion about our thoughts about what to put on the pages, what is missing, etc.?
Answer: You can use Google Moderator to catch up on opinions and with Google Group Discussions your able to create topics to discuss on.
The following two references explain how to do it:

Google Moderator
Google Groups Discussion

Google Sites as Wiki--Discussion Option


How do multigrid approaches deal with Gibbs phenomenon?

Question: I know (from https://scicomp.stackexchange.com/a/31339/20545, among others) that I need a certain mesh density in FEM, else I might get non-physical oscillations in my solution.
How do multigrid approaches deal with such problems? They reduce the problem to a coarser mesh, solve it there, and use the result (by smoothening) for either solving the problem directly on the fine mesh, or for preconditioning. While solving on the coarse mesh, those methods will result in oscillations. Will those be smoothened out during the process back to the fine mesh, or are there other restrictions which avoid bringing those oscillations back to the fine mesh?
Or is my understanding of the method wrong?
Answer: The point important to understand when thinking about multigrid is that the lower levels of the hierarchy do not actually have to solve the problem accurately. Rather, the operators at the lower levels just need to provide good approximations of a part of the spectrum (eigenvalues) of the operator on the finest level -- specifically, they need to well approximate the low-frequency component of the solution. (The smoother takes care of the high frequency component.)
As a consequence, the "qualitative properties" of the solution on the lower levels don't actually matter very much.
Comment: @cpraveen: That's the wrong question. In multigrid methods, you solve the equations on a coarser level where the (restricted, smoothed) residual acts as the right hand side. You will then get a solution that represents the error on this level. It may very well be oscillatory, but what you use as correction on the next finer level is what you get after (i) you transfer this error representation to the next finer level, (ii) you smooth it. Smoothing here is meant in the common sense of the word: In the simplest case, you just average neighboring nodes. So yes, it is possible :-)
Comment: If you apply standard galerkin to a problem, which then generates oscillations on coarse meshes, is it even possible to construct a smoothing iteration scheme ?
Comment: I was considering a Galerkin method applied to a convection-diffusion problem. My doubt was about smoothing properties of the iterative scheme. Suppose $h$ is finest mesh on which mesh Peclet < 2 so $A_h$ is a good matrix (M-matrix?). Suppose on $2h$ mesh, mesh Peclet > 2 so that $A_{2h}$ is not an M-matrix. Would the iterations using $A_{2h}$ actually reduce the high frequency errors on $2h$-mesh ? @wolfgang-bangerth
Comment: Ah, I see -- you might have to stabilize on the coarser meshes as appropriate. But I really don't know.


Is double hashing collision resistant?

Question: Double hashing can surely provide more security than only one layer of hashing but does that necessarily mean it is more collision resistant? This question in a more mathematical form: If $H$ is a collision resistant hash function, is $H\circ H\colon\;x\mapsto H(H(x))$ still collision resistant?
Comment: What specific threat do you expect to mitigate by hashing twice?
Answer: Yes. Let $H$ be a collision resistant hash function and assume that one can find a collision $(x,y)$ for $H\circ H$, that is, $x$ and $y$ with $x\neq y$ and $H(H(x))=H(H(y))$.
Consider the results $H(x)$ and $H(y)$ of applying $H$ once to both inputs. Then either

$H(x)=H(y)$, hence $(x,y)$ is a collision for $H$; or
$H(x)\neq H(y)$, hence $(H(x),H(y))$ is a collision for $H$.

Therefore, obtaining a collision for $H\circ H$ allows an attacker to derive a collision for $H$, showing the claim.

What could suffer is the output distribution of $H\circ H$ as opposed to $H$, that is, even if $H$ is uniformly distributed on the set of all bit strings $\{0,1\}^\ast$, the distribution of $H\circ H$ may be arbitrarily bad. For instance, when $H$ is not bijective on its image (which is the usual case), there are always hash values that are not in $H\circ H$'s image while others may have lots of preimages. However, this doesn't break collision resistance in the cryptographic sense, as outlined above.
Comment: Hi. About the **collision probability**, $P_c[H]$, in optimal hashes (eg. SHA1), it increases with double hash?  That is, $P_c[H\circ H] > P_c[H]$ ?
Comment: If you preefer to comment as an other question, see https://crypto.stackexchange.com/q/58542/42893

Is double hashing collision resistant?


For an extension, to modify database data, is it better to use SQL or API

Question: Simple question here,
From a computing and 'civicrm correctness' point of view, is using SQL (via CRM_Core_DAO::executeQuery or similar) or using the API ( civicrm_api3('Contact', 'create', $params)) better?
Thanks,
V
Answer: Generally, it is wisest to always use the API.  Many necessary updates actually touch multiple tables and the API takes care of it nicely.  This is especially true with financial updates. The API also encapsulates the database structure so as to effectively hide any database structure changes that may happen over time.
IMHO, pretty much the only time that SQL might be called for is if you are doing a huge bulk update wherein using the API would take excessively long.
Answer: Agree, the API is decidedly the best way as it does multiple stuff and should continue to function over upgrades when there are database changes. I only use SQL when either the API does not do what I need, with custom data because it is easier most of the times or when doing bulk stuff.


Make more contrast between visited and unvisited links in linked and related questions section.

Question: If you take a look at the entries in the related questions list on any question it is REALLY hard to tell which you've visited and which you haven't (the colors are #666666 vs #888888). stackoverflow is a little better, but I'll probably bring up the issue there as well.
Answer: Fix is on the way.


Conky and conky-manager on Juno?

Question: Last year, I had successfully installed conky and conky-manager in Freya. Now I have migrated to Juno. I am very happy with this new version. But I would like to install also conky and conky-manager. I know it's not easy, but you can, and I have not found complete and effective instructions on the internet.
Answer: First of all download files from following links:

Realpath_8.26
Newer release version

And then go to your download directory use following commands in your terminal:

sudo apt install conky
sudo dpkg -i realpath_8.26-3ubuntu4_all.deb conky-manager-v2.4-amd64.deb
sudo apt -f install

Enjoy!

Conky and conky-manager on Juno?


What to do if you are dealt AA at the begining of a tournament

Question: Imagine you are in a tournament no rebuys allowed, you are on the big blind with AA and someone on early position pushes all in, should you take a chance on variance against a probably (AA, AK, KK, QQ) or should you slowly grow your stack?
Answer: Having 200 big blinds does not mean that you're twice as likely to win the tournament over someone who has 100 big blinds.
However, your chances of cashing do increase by a good amount and result in you being able to put more pressure on your opponents and at the same time you'll be less likely to becoming short stacked at the same time your opponents will, meaning you won't have to take high risk spots as often as they will.
Folding AA would be leaving a huge amount of equity. You have ~80% equity. If you say no to it you're probably playing a tournament you can't afford. Go all in and go play the next tournament if you lose.
From an ICM standpoint you're not even allowed to fold AA on the bubble (one exception: in satellites where you are near the bubble and guaranteed to make the money), let alone here. Only exception would be if you're guaranteed to cash anyway and a min-cash would be live changing money to you, which is unlikely.
To get an exact answer you can go into solvers such as ICMizer or Holdem Resources Calculator and see what hands you can call all in for and in which situations, such as this one.
I understand the argument of surviving, but I only think it's valid to this extreme if you're not trying to win the maximum in the long term.
Comment: Thanks, yes I'm comming from the feeling side as well, I lost on the second hand the other day against someone I knew had squad but he went all in, I analyized my hand against his later and I had over 80%, I should keep practicing non-tilting tecnquies and keep beleiveing on statistics
Comment: @Saikios Yes. Moving down in stakes is probably wise as-well if individual results are making you tilty.
Comment: One additional comment: the structure of the tournament plays a role in this decision as well. The quicker the structure of the tourney (a turbo tourney for example with blinds doubling up every 15 minutes), the more people will be willing to shove with less than premium hands.
Answer: You call. The previosu answer is good enough, but there is some more reasoning to it. If you fold, everyone can beat you by just shoving any-two-cards against you (if you have aces, there is no big difference between them having JJ or 76s)
Also, even if you are assuming some risk, most situations assume a much higher risk. You just have to accept that even the best player does not win every time


Best practice to prevent lack of tools?

Question: One of my biggest problem during a game of Banished is the ongoing lack of tools. Every citizen seems to need tools (of iron or steel) again and again.
What is the best practice to reduce the amount of such tools (made by the blacksmith)?
Comment: Are you asking about reducing the consumption of tools or how to make them efficiently?
Comment: Reducing the consumption of tools is my primary problem.
Answer: The only way to reduce consumption of tools is to upgrade to steel tools, which last twice as long as iron ones.  Besides that, the only thing you can do to avoid a tool shortage is to

Increase the limit for the blacksmith if he/she is consistently hitting their limit
If not, make sure your blacksmith is productive by ensuring he/she doesn't have too far to walk
Build more blacksmiths
Always make sure you have enough iron and logs (and coal, if you go for the steel option).
Answer: A tool crisis is a serious problem which can be the downfall of your village. Lack of tools greatly affects the productivity of almost all jobs, including blacksmiths, which in turn reduces the tool production even more and makes it hard to get out of. To make matters worse, a tool crisis will often be followed by a hunger-crisis and mass-starvation, because the productivity of all food-sources is also affected. Good luck increasing your tool production while your blacksmiths and builders are dying one after another.
That means a tool bottleneck needs to be prevented at all cost. Make sure that you always have at least one replacement tool stocked per adult citizen, better two. When your number of citizens exceeds the number of tools you have stocked, you need to act quickly and build more blacksmith workshops.
Also, make sure that your blacksmiths never run into a supply bottleneck. To prevent this from happening, get a forestry and a mine for a constant source of logs and iron. That way you no longer need to harvest iron and logs manually. When you have the manpower available, you should get a second mine to produce coal, so you can produce steel tools.
Answer: Nicely said, would work probably, but in my case (having the same problems) i can not build up iron (mine or groundloot) fast enough, i got about 75 adults with 50 of them having no tool. So my food gathering drops fast because they don't have a tool. (I'm playing for the achievements "no Trader", "no Fields", "no Schools" on a large easy valley map, with therefor long walk routes for my citizens to get stuff (hence Tools, if i even got any). I got 2 blacksmiths (nr. 3 is in the making, but stopped building it for now). Even my blacksmiths have no tools atm. and since food drops i can not afford to lower citizens loot food either.
So a Tip: drop ALL you got going if you got a simular problem apart from the food gathering.
That means even (yes truly)stone/coal/herbs/wood(assuming you DO have enough logs) production.
Only keep your Laborers loot iron from the ground, wood if needed, and keep iron mine(s) open.
To get enough people to do that, make all the next mentioned professional workers a Laborer until you got the tool problem solved (stone miners, coal miners, herbalists, woodcutters, tailors, brewers, clerics, etc) Do not drop a teacher, because students can help you also to solve the problem (make a new student builder f.e. because with builders you can make more Blacksmiths OR you can use the new build citizen student a replacement Blacksmith in your "old" Blacksmith building.
Comment: This is a long wall of text. Would you mind editing your answer so it is easier to read.

Best practice to prevent lack of tools?


How do I edit a .plist file?

Question: What's the best application to open and edit a plist file ?
Comment: Voting to close *without* commenting? Way to go, team!
Comment: This is a good question. Several times, I have wanted to open a .plist file, but even with downloading an app it looked (very) difficult, so I gave up.
Comment: wasn't me but someone voted to close... I think if you just changed your question to be more specific about what you're trying to do it wouldn't get any 'subjective' votes.
Answer: If the plist file is in the XML format, you can edit it in any text editor like TextEdit. If the plist file is in the binary format, you can convert it to XML first by running:
plutil -convert xml1 file.plist

If you want to go back to binary format after editing:
plutil -convert binary1 file.plist

If you have Xcode 4.3 or later, you can use it to edit property lists in a graphical editor like this:

Xcode 4.2 and earlier came with a separate application for editing property lists (/Developer/Applications/Utilities/Property List Editor.app/).
Comment: `plutil -p ` will "print property list in a human-readable fashion" instead of converting it
Comment: This is the more complete answer and should be the accepted one. For example, you can't directly edit ~/Library/Preferences/.GlobalPreferences.plist without conversion.
Comment: As pointed out by this solution, it is totally possible to use `plutil -convert json $file` (or `xml`), then edit the file with any editor (like `vi`), and finally convert it back with `plutil -convert binary1 $file`.
Answer: A PList file, like Mankoff said, is just a specially formatted XML file, so you can actually edit and create them in a program like TextEdit.
Because of the specific nature of PLists to Development, however, using a special program like Xcode or Property List Editor becomes a much more fruitful endeavor. This is because it not only automatically formats the XML code for you, but it will actually translate the key identifiers and layers into readable words, and also for some values it will provide a drop-down menu to fill in the correct responses. Especially when dealing with iPhone plists, when multiple runtime variables can be set using the Plist, easily creating new fields and knowing what to put in them makes it so much easier.
You can get both Xcode and PList Editor from the Apple Developer website for free by downloading the latest Xcode release.
Comment: IIRC some plist are compressed though, which makes them unopenable in a text editor without decoding them first. Apple tools do that automatically though, and back again.
Comment: If only… ! But no, some .plist files are binary or something like this, and TextEdit is not enough for them.
Comment: Well perfect, more reasons to use Xcode 4!
Comment: Remember that, depending on the specific use case, there may be a tool better fit for the job, intended for editing a specific type of plist file. For instance, you can use Apple Configurator for editing iOS profiles (.mobileconfig extension) or Clover Configurator for editing Clover boot profiles.
Answer: A fine program like TextWrangler can edit binary .plist files without first converting them using Terminal. Simply open the file like you would any other (i.e. drag-and-drop on the program icon, or the File open dialog, or Open With in the Finder or...)
Comment: But the values are unreadable.
Comment: @ScottJohnson BBEdit is both TextWrangler's big brother and successor (but it has an option now to use the old TextWrangler icon! Yay!)
Comment: Thanks for sharing this tip, Daniel. I have TextWrangler's big brother, BBEdit, and I had no idea that I had a nice plist editor all along. :)
Answer: Since Apple got rid of the GUI Property List Editor, Xcode is the best free option if you want to be sure of the result.
There are some gotcha's using a generic code editor to edit plist files.  Since dictionaries use entries like
<key>some key</key>
<string>some value</string>
<key>another key with boolean value</key>
<true />

You can create a valid XML file that is not a valid plist file, for example:
<key>some key</key>

<key>another key with boolean value</key>
<true>yes</true>

If you're willing to go commercial, Plistinator will edit both binary and XML plist files.
Full-disclosure: I'm the author of Plistinator and the $12.99 it costs pays for my ramen and rent.
Comment: does it better than XCode?
Comment: Xcode is better than Plistinator on Mac - the UI is better, and its canonically Apple.  It can be a pain as you have to install the whole of Xcode just to get the editor tool.  Plistinator does do the directory search/scan and it also has a large edit field for entering free form text into values.  Those features make Plistinator excellent for jobs like data driven apps and games.  But for most jobs Xcode's editor is better.
Answer: On a Terminal window, you can use PlistBuddy, available at /usr/libexec/PlistBuddy.
PlistBuddy can read and modify values inside of a plist, either interactively or directly on the command line.
However, PlistBuddy is not a GUI editor.
Usage examples:
# Show full help
/usr/libexec/PlistBuddy -h

# Print content of plist
/usr/libexec/PlistBuddy -c print /Library/Preferences/com.apple.TimeMachine.plist

# Print selected content of plist
/usr/libexec/PlistBuddy -c 'print SkipPaths' /Library/Preferences/com.apple.TimeMachine.plist

Answer: Free Visual Studio Code editor can open, edit and save plist files in binary format with the help of the Binary Plist extension:

A Visual Studio Code extension that enables editing of binary property list files as XML. It is inspired by the BinaryPlist Sublime Text package, although the experience is not as seamless (the user must agree to opening a binary file and the editing takes place in an additional tab). A virtual file system is used to achieve this using the FileSystemProvider API.
The extension is cross-platform but primarily uses the macOS plutil binary for conversion, the Python plistlib is used as an alterntative if available. The node package simple-plist is used as a fallback but due to JavaScript not having a float type real values that are whole numbers will be cast to integer types (a warning dialog is shown first).
Answer: I have used PlistEdit Pro for macOS and found it to be useful and comprehensively feature rich.
Answer: BBEdit will open plist files for editing, and do any necessary conversion of file types.
It will also handle file permission access, if needed.
You can also do things like create Text Filters to do things like encode/decode base64 encoding.
It's the essential text editor for Mac. (No connection to the company, just a user for 30 years...!)
Answer: Checkout SimPLISTic - an alternate, cross-platform format for representing property lists

How do I edit a .plist file?


Two same emails arrive in postfix

Question: I changed an MTA in postfix from sendmail,
but two same email contents arrive when the same address is included in To and Cc.
 There did not need to be such email contents,
 Please Help me!.
 with the avoidance of this movement at the time of sendmail.
Answer:
Postfix sends duplicate mail

To work around this we have moved all mbox-to-mbox aliases into
virtual and have set:
<code>    enable_original_recipient = no
</code>
So that all the 1-to-many expansions are done in virtual and aliases
is only used for single delivery to commands or files.

Two same emails arrive in postfix


"Trace route" to Next-hop as destination

Question: I know traceroute in BSD uses UDP by default and gets ICMP error message from intermediate hops when TTL is decremented and found to be 0.
My question is - what if we trace route to next-hop router:
- Should the router respond with port unreachable message?
Comment: Should be easy enough to test.
Comment: Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
Answer: As Ron said, this is a pretty simple thing to test - you should give it a try if you haven't already.
In BSD systems traceroute will use a range of high, unregistered UDP port numbers as well as TTL.  The device originating the probes will send 3 probes, they will look like this:
NOTE: The port numbers won't necessarily be exact in your tests.

Probe 1: TTL = 1 UDP Port = 33434
Probe 2: TTL = 1 UDP Port = 33435
Probe 3: TTL = 1 UDP Port = 33436

In the condition that the we're NOT tracerouting to the next-hop, you will see the following message from the next device:
Time to Live Exceeded
This is what we would expect, to see as traceroute progresses, the next device's probes would look like this:

Probe 1: TTL = 2 UDP Port = 33437
Probe 2: TTL = 2 UDP Port = 33438
Probe 3: TTL = 2 UDP Port = 33439

Now let's say that second set of probes will reach our intended destination.  The response we will get is (and this is a portion directly from tcpdump):
udp port 33437 unreachable
Now what does this mean?  It means we've reached our destination, because only our destination can say "No this port is not available" (as we would expect from the higher unregistered UDP port range).

My question is - what if we trace route to next-hop router: - Should the router respond with port unreachable message?

The cool thing about traceroute is that, it has no idea if you're trying to hit something 20 hops away, or just 1 hop away - it needs to be able to adapt to any of those situations.
So it will behave no differently than it would at the last hop in a 20 hop traceroute.
If you traceroute your next hop, your probes would look the same:

Probe 1: TTL = 1 UDP Port = 33434
Probe 2: TTL = 1 UDP Port = 33435
Probe 3: TTL = 1 UDP Port = 33436

But the different here is, a TTL of 1 is enough to get to your next hop.  So you would see the "udp port XXXXX unreachable" message right away, implying that the traceroute has completed.  Instead of seeing the "Time to Live Exceeded" messages.
I hope this helps clear things up, if you have any other questions related to this - leave a comment and I'll be happy to update my answer.
Answer: The router will do whatever it is configured to do. ICMP messages are a courtesy and traffic can be silently discarded or an ICMP response can be provided. This is an optional part of the protocol. There are two schools of thought on whether a router should send the ICMP response. The first is that it allows visibility into the network and allows you to troubleshoot problems, while the second regards it as a security risk believing that obscuring your visibility of the device provides security.
Answer: Traceroute is used to find the hops between you and the destination. In between the hop count whatever the number of hops the TTL is not affected, TTL is concerned with routing protocols. If you do a traceroute and you get unreachable that means you will have a connection problem between you ( the host) and the destination. try checking the physical layer, layer 2 and of course layer 3 ( because I doubt that you can even ping).
Comment: -1 "If you do a traceroute and you get unreachable that means you will have a connection problem"  Not if you're using UDP traceroute like the question asks about.
Comment: WRONG!!!! Routers decrement packets' TTL value by 1 when routing and discard packets whose TTL value has reached zero, returning the ICMP error message ICMP Time Exceeded.[2] Common default values for TTL are 128 (Windows OS) and 64 (Unix-based OS).Traceroute works by sending packets with gradually increasing TTL value, starting with TTL value of 1


What are the necessary circumstances that qualify a marriage for annulment in the Catholic Church?

Question: I understand that the Catholic Church issues annulments under certain circumstances for some marriages.  What are the specific circumstances necessary to qualify a marriage for an annulment?  I'm wondering if some annulments are denied, leaving the couple to resort to divorce instead, and what circumstances might lead to that.
Comment: Divorce (legal ending of marriage recognised by the state) is not an alternative to annulment (the ending of any putative sacramental bond). Divorce is generally necessary before an annulment can be considered. See the Archdiocese of Toronto's [helpful leaflet](http://www.archtoronto.org/arch_offices/pdf/Nullity_of_Marriage.pdf).
Comment: As the Catholic perspective is that 1) once you have a valid marriage, it is permanent until the death of one's spouse; and 2) if you don't have a valid marriage then you were never actually married at all; then perhaps your question is "What constitutes a valid marriage in the first place?"
Answer: Members of the Catholic Church are required to marry in front of a priest (or deacon) (CCC 1630). If one of the parties is Catholic, but there is a serious reason why the marriage should be celebrated in front of a civil servant or a non-Catholic minister, a dispensation can be granted. If no dispensation was granted and the couple did not observe this law — the marriage is considered invalid. Because the nullity of the marriage is clear from the circumstances there is no need for a canonical process to issue a Declaration of Nullity. The correction of this invalidity requires the couple to exchange their consent according to canonical form (commonly called "having the marriage blessed").
Impediments
If one of the parties were prohibited from marrying by a diriment impediment, the marriage is invalid. Because these impediments may not be known at all, the marriage is called a putative marriage if at least one of the parties married in good faith.
Diriment impediments include:
Being too young. The absolute minimum age is 16 for males, 14 for females, but episcopal conferences can set a higher limit
Antecedent and perpetual impotence (not to be confused with sterility)
Being already married
If one party is a Catholic and the other has not been baptized (unless a dispensation is granted)
The man was ordained to holy orders
Either party made a public perpetual vow of chastity in a religious institute
Abduction with the intent of marriage (known as raptus), is an impediment as long as the person remains in the kidnapper's power
Impediment of Crime, bringing about the death of one's own spouse or the spouse of another, with the intention of marriage
Close relationship by blood, called Consanguinity, even if the relationship is only by law
Close relationship by marriage, called Affinity
Some of these laws can be relaxed by a dispensation before the ceremony.
For example, Catherine of Aragon and Henry VIII of England received a dispensation from the impediment of affinity (Catherine had previously been married to Henry's brother Arthur, who died). Henry based his request for an annulment on the grounds that the dispensation had been improperly given in that his father, Henry VII, had pressured the Archbishop of Canterbury into granting the dispensation.
The correction of this invalidity after the marriage requires first that the impediment has ceased or has been dispensed, and then a "convalidation" can take place or a sanatio in radice can be granted to make the marriage valid.
Grounds for nullity
A marriage may be declared invalid because at least one of the two parties was not free to consent to the marriage or did not fully commit to the marriage.
Grounds for nullity include:
Simulation of consent; that is, the conscious and positive exclusion at consent by either or both of the contracting parties of one or all of the essential properties or "goods" of marriage: a) exclusivity of the marital relationship; b) the permanence of the marital bond; c) openness to offspring as the natural fruit of marriage (canon 1101§2)
Deliberate deceit about some personal quality that can objectively and gravely perturb conjugal life (canon 1098)
Conditional consent; the condition must concern the past or present (canon 1102)
Force or grave fear imposed on a person to obtain their consent (canon 1103)
A serious lack of the discretion of judgment at consent concerning the essential matrimonial rights and obligations to be given (canon 1095 n.2)
Psychic incapacity at consent to undertake the essential obligations of marriage (canon 1095 n.3). According to Canon 1095 a marriage can be declared null only when consent was given in the presence of some grave lack of discretionary judgment regarding the essential rights and obligations of marriage, or of some real incapacity to assume these essential obligations.
Answer: It should perhaps be emphasized that an annulment does not dissolve a marriage. It is, rather, an official declaration that what appeared to be a marriage was not, i.e., that there was never a valid marriage in the first place. Unfortunately, in recent decades, the grounds for annulments have been expanded to the point where I find it hard to take them seriously --- for example, the "carries an addictive problem with alcohol or drugs into the marriage" quoted by Jeremy in his answer.  In principle, grounds for annulments are supposed to be reasons why the purported marriage could not be valid --- for example, if one party was already married to someone else, or if one or both parties were being forced to get married, or if they had conspired to murder the previous spouse of one of the parties.  In other words, grounds for annulments are essentially the same as impediments to marriage.
Comment: My understanding is that in the case of the persons who have annulments because of mental illness receive annulments because it is questionable as to whether or not they are capable of consent and whether, in fact, they are consenting.
Comment: (I am grouping mental illness with those who suffer from addition, as that seems the be the simplest way to address that issue)
Comment: @Andreas After reading this answer a few times it kind of comes off to me as a long opinionated comment rather than unbiased fact. The first 2 sentences are solid...but the rest could be pholisophically debated and/or refuted
Answer: Some of the circumstances that allow for annulment are:

"Psychological incapacity, absence of a proper intention to have children, be faithful, or remain together until death. Lack of judgement when married (young age, pressure, so on).  One spouse carries an addictive problem with alcohol or drugs into the marriage. Perhaps a person, unfaithful during courtship, continues the infidelity after marrying. Marriage because of a pregnancy. If one of the marriage mates is violent." from Catholic Update & Friar Jacks

Some annulments can be denied if they are lacking enough reason to do so. For instance if the couple are fighting(not violently) a lot and want to be separated, that is not terms for an annulment. Marriage counseling would be recommended.
If the couple where to get divorced without the annulment, I presume, there would be spiritual consequences. Mark 10:11&12:

"He said to them: "Whoever divorces his wife and marries another commits adultery against her, 12  and if ever a woman after divorcing her husband marries another, she commits adultery."

Without first dissolving the marriage, a new marriage would be considered adultery.


Develop a provider hosted app from host machine visual studio

Question: I've windows server 2012 in my oracle virtual box VM with sharepoint 2013 and Visual Studio 2013 installed. I've setup my SharePoint server to develop apps, I created a provider hosted app from visual studio in my VM where sharepoint is installed. The app is working fine there. I created one more app from my local windows 7 host machine and tried to deploy it, the app got deployed and I was able "Trust the app". But it is returning "The remote server returned an error: (401) Unauthorized." error when II browse the app site. I'm not much experienced in Provider hosted app development. My host machine is in a domain called RECT and the the server in my VM has BSR. How can I develop and debug the app from my local machine?
Answer: Troubleshooting tips:

Make sure the SharePoint site url is accessible from your local machine.
App registration is done for the domain and App Id and app secret is correct in web.config of PHA.
Certificate is generated and installed in your local desktop. Add the certificate to personal store.
Make sure IssuerIdin web.config is same as the one used while create trusted security token service using powershell in SharePoint server.
Comment: Hi Unni, thanks for the reply.The server is accessible from my local machine. I added the certificate to personal store, the issuer id is also correct. I don't know what do you mean by "App registration is done for the domain". The app client id looks fine. I thought anonymous authentication on the web application could be the issue, So disabled it. but my visual studio keep on asking the credentials after I did that. Any guess?


24V Vs 36V Brushless DC HUB Motor For Electric Bike

Question: I am considering buying an electric bicycle using brushless DC Hub Motor. What is the difference between 24V Vs 36V motor? Is it related to the maximum torque produced by the motor? If yes, what does that mean to a bike rider?
Comment: Author cross posted [here](http://electronics.stackexchange.com/q/14352/1486).
Answer: As far as motors go, usually the higher the voltages the more efficient they run. However there is a trade-off because usually the higher the voltage, the less efficient the battery is! Different systems may balance these factors at different points depending on how they expect the system to be used and what parts they have access too. I don't think you will be able to strictly say one is better than the other, you will need to compare the specs and a whole package and figure out what package suites you best.
Comment: Why would a battery be less efficient with higher voltage? It's just a bigger number of same low-voltage cells, isn't it?
Comment: Yes, but but batteries are physical objects subject the restrictions imposed by classical physics and real world matter :) Multiple smaller cells bring increasing overhead in psychical packaging. There are of course various trade offs at various size factors depending on battery technology, but in very general terms the less meta packaging you have to do the more battery you get.
Comment: Agreed. I guess the worst problem is with charge equalizing over the cells. And this might be a problem for a demanding application like a bicycle.
Answer: Again, it's the same as with battery powered power tools. Usually the higher the voltage the more powerful the motor is and the higher battery Volt-Ampere-hour (not Volt-Ampere alone) rating is.
More powerful motor will usually (but not necessarily) mean higher torque and that will mean climbing steeper hills at higher speeds and accelerating faster. Higher battery Volt-Ampere-hour rating will mean you have more energy in the battery and can go further on your bike.
All of the above implies that both cases have the same energy efficiency which is not always true - motor controllers and other circuitry can have different efficiencies on different bike models. You should get details on the specific models you compare and pick the one you like more.
Answer: From my electrical theory days way back in my distant youth , higher voltages have less transmission losses for the same amount of power.
But higher voltages come with the issue that they need better insulators.
Lower voltages need larger conductors because for the same power level they need more current (amps, I)
This is all to do with :
Volts = V = I * R = Amps * Ohms
and
Watts = I * I * R
All electrical circuits have resistance , impedance (AC resistance) .
In theoretically ideal circuits the power is only dispipated in the load.
In realistic circuits power is disipated in the load and the power source.
This is because the power source has an internal resistance.
So higher voltages mean less amps for the same power level. So there should be less power losses internal resistance of the power source and the cables transmitting the power, and thus more of the power gets dispipated in the load.
This is a bit of a simplified explanation.
Electrical circuits are a trade of between conductor size, insulation size, and safe voltages (that don't fry people).
Comment: OK but are any of these things an issue at the voltages we're talking about? Insulation at 24 or 36V is easy -- we're not talking kilovolts. Likewise, going from 24V to 36V only increases the current by a factor of 1.5, so increases the power loss by a factor of 2.25 for any given cables. But using only slightly fatter cables would halve the resistance and get the power loss back down to what it was before. We're only talking a metre or so of cabling so the extra weight isn't going to be a big deal. None of conductor size, insulation size and safe voltage seems to be an issue here at all.


Should I use a VPN with Orbot?

Question: Should I use Orbot with a proxy or VPN? If so should I place it before or after Orbot's connection to the Tor network?
Comment: People should make more accessible how to safely root devices. I feel it is difficult like installing Linux on a computer that does not have the compatibility with it (you know how it gets complicated installing linux last versions on old computers or especially on pc that do not allow a certain structure\compatibility with it... ) the same thing is with root, seems so difficult to do. Please share.
Answer: Similar q/a linked below should also apply here.  Not necessary imo. Although it might be more secure to use orbot's built-in transparent proxying (requires a rooted device)  which will torrify additional system applications/etc that you or the browser connect with.
Secure my connection with VPN router & Tor
Answer: Updating for 2018: Orbot now allows transparent torrification without root on android and ios devices. However this is not always beneficial as it forces identifying information through Tor which can de-anonymize you at the exit. I personally now use a multi-hop vpn and Orbot simultaneously to allow the use of Orfox through Tor and everything else through vpn. This is possible on android as of v 7.0.

Should I use a VPN with Orbot?


Team members profile

Question: I want to identify team members' weak and strong points, in order to work on the team's (and individuals') signature. Are there known techniques for building team members' profiles (maybe similar to Roleplaying Game character sheets) and refining them over time?
Comment: Just my opinion but I think you'd be better served to identify the team's strengths and weaknesses.
Comment: A far better approach would be to ask team members to identify their own strengths and weaknesses and work with them to close gaps between where they are an where and what is expected for their role
Answer: I usually create something like Programmer Competency Matrix and modify as needed.
Comment: That is very interesting, together with Roberto's suggestion regarding soft skills.
Answer: You need to identify:

What skills are needed for your current team to be successful?
What skills does every individual wants to improve on?

And then find a common ground to figure out the right skills,levels and how to proceed. A good idea as Liath pointed out is to let the team build this matrix together.
I looked at Anton suggestion, a competency matrix is a great idea, but you also need to include soft skills on them because they tend to be equally valuable for a great team to succeed.
Another point, be very wary of creating diverse skills that are not easy to game, and that ideally evolve /change a bit overtime, otherwise people might just rapidly lean towards improving the skills you consider useful and then forget about improving themselves. More information on this topic can be found in the book: Drive.
Answer: Have a look at the Agile Skills Project. It touches on all skills which Agile development team members might need. You can do a self or peer assessment. After the assessment they can look for gaps and the Scrum Master can coach them to get deeper skills in those topics.
It works similar to a more typical skill matrix, but it helps you get started with a broad set of Agile skills, in the following areas: Business Value, Collaboration, Confidence, Product, Self Improvement, Supportive Culture, Technical Excellence

Team members profile


Raspbian with kernel 2.6.18 ~ 3.10.10

Question: I'm looking for old version of Raspbian with kernel 2.6.18 ~ 3.10.10.
Answer: Google points to http://downloads.raspberrypi.org/raspbian/images/ which has old Raspberry Pi Foundation images.
You will have to work out which Linux kernels they use.
https://github.com/raspberrypi/linux (Branch: tab) suggests that 3.2.27 was the earliest kernel used.
Answer: To emphasize a point made in joan's answer, a quick glance at current "longterm" kernel releases shows that 3.2 dates back to at least January 2012 (I think the first 3.2 would be some months older), a month before first generation Pis became widely available, so it is very unlikely there is any branch of the Pi kernel predating that.
You are not strictly bound to using a specific kernel with a specific version of Raspbian, however, you will probably have to compile it yourself, install the modules properly, etc. and there are no guarantees.
Answer: Here is the link to raspbian version infos: https://en.wikipedia.org/wiki/Raspbian

Raspbian with kernel 2.6.18 ~ 3.10.10


Automatic Transmission is Skipping 2nd Gear

Question: I have a 2008 Ford Escape XLT. I was recently told that it is revving up high before shifting because 2nd gear is gone, so it is going from 1st gear to 3rd. Will it ruin the other gears if I drive it too long like this? How much longer can I drive it like this? I know I need a new transmission but it will take me a bit before I can get one.
Comment: Is that what a transmission shop told you? You may want to get a second opinion from another shop before you replace the transmission. Are there any codes? How's the fluid level? Does the transmission slip?
Comment: Yes a transmission shop told me that. The fluid level is good. when I start out driving it goes slow and revs up to over 3500 rpm before it kicks into  the next gear, then after that it goes fine. there is a light that comes on in the shape of a wrench and in the manual it say for that symbol it is the throttle control / powertrain the manual also says that the light illuminates when a powertrain fault has been detected to contact the dealer as soon as possible.
Comment: Sounds like the electric throttle body controller. If it pulls a code p2111 or p2112 that's the issue.
Answer: Well, it depends what really happened to that 2nd gear. If it's just the shift solenoid that went bad, you'll be ok, and it's actually simple to fix. But if the gear is physically damaged, it is shedding or has shed metal fragments.
There are magnets in the tranny pan to catch these, but they are only designed to handle normal wear and tear (and stray nuts, as I've found out), they may get overwhelmed with the amount of metal coming from a shredded gear.
What exactly happened to your 2nd gear?
Comment: The Mechanic did not tell me exactly what happened he just said 2nd gear is gone and that I need a new transmission. He put it on his computer and then took it for a ride around the block. and when he came back that is when he told me it was shot.
Comment: Replacing an entire transmission is way more expensive than just replacing a solenoid. Ask exactly what is wrong with the transmission, and ask for a 2nd opinion at another shop. Solenoids are cheap and easy.


Can radar detect a small flying device with MEMS microengines?

Question: I have seen some MEMS micro engines and some micro turbines and I would guess they can be attached to some payload to fly. Is it possible for commercial/military radars to detect those micro flying devices?
Answer: Obviously the MEMS engine itself is not going to be detected: they're only a few millimetres across. The question entirely depends on what you attach it to.
Conventional radars have trouble detecting UAVs less than a couple of metres long, and replacing their power plants with micro turbines won't change that.
My neighbours at Aveillant already have a holographic radar system that can detect smaller targets such as UAVs more accurately. Again, changing the power plant technology won't change that.
Micro-turbines are not intended to replace propulsion systems, but to replace batteries, allowing them to use denser hydrogen, methane, or methanol fuel. As far as I've been able to find, they don't produce break-even power yet, but it's envisioned that they will become commercially relevant once they can produce more than 10 W (about .01 hp), in a few years' time. For comparison, a current, small, military UAV might generate tens of horsepower, and some experimental super-lightweight UAVs need as little as 5 hp, but with no payload or cargo.
TL;DR: (a) MEMS turbines aren't going to be relevant for UAVs for some years, and they'll have to be much bigger than they are now; (b) replacing the power plant won't make much difference to the radar signature.
Answer: Radar detection depends on the scattering of radar waves on objects. If we use the common X-band (8-12 GHz frequency) as an example, the wavelength $\lambda$ of the radar waves is in the order of 3 cm. Now the size of the target comes into play, expressed as a ratio α, defined as $$\alpha = \frac{\pi\cdot D}{\lambda}$$
with $D$ the diameter of the object to be detected.
α ≪ 1: Rayleigh scattering (small particle compared to wavelength of light). Radiation energy is diffused without a preferred direction, strongly dependent on wavelength.
α ≈ 1: Mie scattering (particle about the same size as wavelength of light, valid only for spheres)
α ≫ 1: geometric scattering (particle much larger than wavelength of light). Radiation energy is reflected with the angle of reflection equal to the angle of incidence.
Only for large α you will get a return signal which can be used for detection. Then we speak no longer of scattering, but of reflection. If your MEMS engine is just a few mm across and attached to a plastic airframe (which should be transparent to radar waves), it should be impossible to detect with conventional radars. Since the atmosphere is rather opaque for microwave radiation above 20 GHz, infrared or optical detectors will be needed to detect such an aircraft.
Also, the software driving the radar display is an important factor. Common aviation radars will filter out small, slow-moving objects, so even a metallic or carbon-composite airframe several centimeters across will not be detected.
Comment: Could you please explain the difference between scattering and reflexion, in this context?
Answer: It does not matter what type of engine is used; if the Radar is powerful enough and the flying object is near enough (making allowances for any low observable design) i.e. based on the Radar Cross Section, it will be detected by the Radar.
In case of small flying objects, the main problem is not in detection (Radars usually pick up bugs and such) but in recognizing the object in background clutter.
In this case, the military Radars have an edge as they are more powerful and are optimized for detection of small targets in ground clutter.
Comment: Some have even received anti-UAV updates (software mostly) in the past few years.


What operational aspects of Alphabet's Wing drone delivery service will be the same as that of an airline?

Question: The NPR News article and podcast FAA Certifies Google's Wing Drone Delivery Company To Operate As An Airline begins with:

The Federal Aviation Administration has certified Alphabet's Wing Aviation to operate as an airline, in a first for U.S. drone delivery companies. Wing, which began as a Google X project, has been testing its autonomous drones in southwest Virginia and elsewhere.
"Air Carrier Certification means that we can begin a commercial service delivering goods from local businesses to homes in the United States," Wing said in a statement posted to the Medium website.

The article, plus the BBC News's Google Wing drones approved for US home deliveries indicate that Wing (owned by Alphabet, which also owns Google) will be he first US drone delivery company to be run as an airline.:
See also Medium.com's Wing becomes first certified Air Carrier for drones in the US
Question: What operational aspects of Wing will be the same as that of other airlines? They won't sell seats of course, but will the file flight plans for example? Will they have licensed human pilots to oversee the drone's flight?

The Wing company, a Google spinoff, has won federal approval to operate its drone delivery system as an airline in the U.S.  Credit: Wing, Source

Customers who took part in Wing's drone delivery test program in Virginia approach their package after it was dropped on their lawn. Credit: Wing Source
Comment: Converted to answer.
Comment: @StephenS ah, I see now how "certified air-carrier" in one article became "airline" in others, thanks.
Comment: @StephenS I wonder if that's sufficient to post as an answer?
Comment: @StephenS now see, that didn't take long :-)
Answer: Under FAR Part 117, only certified "air carriers" are allowed to sell "aviation services" to the general public. Certification means that the FAA has determined the proposed operations, whatever they may be, will be reasonably safe.
FAR Part 121 covers most scheduled air carriers, which are commonly called "airlines". These are the only air carriers that the media knows about, so it's understandable that they'd conflate the two.
FAR Part 135 covers unscheduled and very small scheduled air carriers. I suspect this is where Google Wing would fall, but I haven't seen anything definitive so far.
Comment: Thanks for the concise yet seemingly complete answer! fyi I've just asked [Why does Google's Wing drone have dimples?](https://aviation.stackexchange.com/q/75137/14213)


How to build a budget-friendly manabase for a 5-color deck?

Question: I am a commander player who operates on a very tight budget. I recently started brewing for a 5-color Jodah chaos deck, but am having trouble building an affordable manabase. I can't afford shocklands, fetchlands, original duals and the like. I am looking to see if there are any land cycles that I have missed that might help me out, for example, I am running pain lands. I am trying to stay away from things like guildgates/thornwood falls cycle, tri-lands, etc, because they are too slow for my deck and my playgroup. I am aware of the issues trying to build a budget manabase for a 5-color deck that is still fast enough to be viable in a good meta, but I'm just wondering if there are any cycles of lands that I could use? Trying to stay away from nonland cards, my deck is already very filled out.
Comment: It would probably be helpful if you provided a budget of how much you are willing to spend
Answer: Here are the lands that will work in a 5 color deck, I ordered them in roughly the order I think they are helpful speed wise to an EDH deck and will include the lands you already run for completeness. Prices rounded to the nearest quarter and are from TCGPlayer based on the results returned by Scryfall. (For sake of site rules, I have no affiliation with either site)
Without knowing your budget, I can't really limit myself to that budget, but I will give a more general overview of less expensive lands and cycles for 5 color EDH.
Bond Lands
You're building EDH, a multiplayer free for all format, and bond lands care about how many opponents you have, allied colors being released in Battlebond, the 2HG set, and enemy colors in Commander Legends. Their prices range from Spectator Seating (/) at $5.75 to Morphic Pool (/) at $28.25. These are all but guaranteed to come out in EDH untapped, until the game is almost over when one land drop won't matter so much anymore.
Shock Lands
These have always been an EDH staple, having the basic land types to allow them to be found by some effects (Farseek) and being able to choose to let them come in tapped when the cost (2 life) was not worth it. These were at one time more expensive lands, however with the two further visits to Ravnica each having full reprints of the cycles, the price to get ahold of these lands has gone down quite a bit, they now run from Hallowed Fountain (/) at $7.75 to Breeding Pool (/) at $20.
Filter Lands
There are a few cycles of filter lands, The first cycle from Odyssey requires you to pay 1 mana of any color to get 2 mana of specific allied color pairs, cost wise they range from Sungrass Prairie () at $0.25 to Shadowblood Ridge () at $0.50.
The second cycle came out in Llorwyn block, it requires you to spend one mana of the colors it can produce to get two mana in any combination of those two colors. Recent reprints in masters sets have brought this cycle down in price, from Graven Cairns () at $4.25 to Sunken Ruins () at $18. Unlike the Llorwyn cycle, the Odyssey cycle cannot tap for mana without paying into it, the Llorwyn cards have tap for colorless.
Also worth mentioning here is Crystal Quarry () which filters 5 mana into one of each color for $6.75 and Cascading Cataracts for $4.75 which turns 5 mana into 5 mana of any color combination you want.
Pain Lands
These lands tap for colorless, or one of two colors if you pay one life. These lands run in cost from Llanowar Wastes (/) at $0.75 to Adarkar Wastes (/) at $8.75.
Mana Confluence ($20.75) and City of Brass ($16.25) can also be considered here, as they tap for 1 of any color at the cost of one life, with slightly different wording (cost/vs damage effect). Murmuring Bosk ($1.25) can also be included here, it is a forest so taps for , but can alternatively tap for  or  for 1 life, it will come in untapped if you reveal a treefolk card from your hand. All of these cards, other than City of Brass cannot be used for colored mana if you are prevented from paying life (effects like Angel of Jubilation or Platinum Emperion) however preventing damage from City of Brass does not prevent it from being used.
Pathway Lands
Zendikar Rising introduced a partial cycle of 6 lands in 2 allied and 4 enemy color pairs and Kaldheim finished the set with the other 4 pairs. These lands tap for one color, but when you play them you choose which side enters face up, and thus which of the two possible colors they can tap for. They run from Cragcrown Pathway/Timbercrown Pathway (/) for $2.75 to Darkbore Pathway/Slitherbore Pathway (/) for $5.75. Note if they enter the battlefield in some way other than being played (being flickered or Scapeshift perhaps) they enter with the front face up, no choice about side.
Slow Lands
This cycle came out in Midnight Hunt, and was completed in Crimson Vow. These lands come in tapped unless you already have at least two lands out when you play them. In faster formats that can be a big downside, but in EDH decks running multiple, particularly five, colors these should be coming in untapped once you get all your colors. Price wise the cycle runs from Overgrown Farmland (/) at $3.50 to Shipwreck Marsh (/) at $8.25.
Check Lands
These check that you have one land of the matching color basic land subtypes out on the field and come in untapped if you do, they don't care if they are basic so Shock, Battle and Bicycle lands will work for this also. Price wise they range from Sunpetal Grove (/) at $3 to Hinterland Harbor (/) at $7.
Reveal Lands
These lands come in untapped if you can reveal a land from your hand with a matching basic type, though it does not need to be basic, so Shock, Battle and Bicycle lands will work. Price wise these go from Fortified Village (/) at $2.25 to Choked Estuary (/) at $3.75.
Battle Lands
These come out untapped if you have at least two basic lands in play, though this makes it less and less likely you will get them untapped the more non-basics you have in your deck, these do unfortunately only exist in allied colors and the costs run from Prairie Stream (/) at $0.75 to Canopy Vista (/) at $2.25. These also have the basic land types, so they will matter for other land types listed, like Check and Reveal lands.
Fast lands
These come out untapped if you have 2 or less other lands can conditionally be faster. They run from Concealed Courtyard (/) at $2.75 to Blackcleave Cliffs (/) at $16.25. These are a little less useful in EDH due to the game format being longer, the deck size larger and the lands limited to one each, the likelihood they will come in untapped is low, they are much better in formats like modern where early advantage means more.
Tainted Lands
These lands tap for colorless, unless you have a swamp, if you do they tap for  or one other color. They go from Tainted Field (/) at $0.25 to Tainted Peak (/) at $4.25. This is a cycle of 4 lands, as the 5th land would be / if you control a swamp, and be a strictly worse than a swamp itself. These also do not care about the land being basic, so Shock, Battle and Bicycle swamps all apply, as do all lands turned into swamps by an effect like Urborg, Tomb of Yawgmoth.
Thriving Lands
Jumpstart added a new cycle of lands, 5 lands that come in tapped, one for each color of mana. The up side to these lands is they let you pick the other color they can tap for as you play them. While they do come in tapped and are slower than most of the rest here, the guarantee of giving you the color you need as your 5th land can mean a lot. They run from Thriving Bluff () at $0.50 to Thriving Isle () at $1.75.
Vivid Lands
Vivid lands always come in tapped, but tapped status really only slows you down if it is the 5th land, completing the set of colors. The major benefit of Vivid lands is they come in with two charge counters, allowing the land to be used for any color twice. They run from Vivid Grove () at $0.25 to Vivid Marsh () at $1.50.
Triomes
Triomes, or tricycle lands (tri color lands with cycling), are an evolution of Bicycle lands seen below. There are 5 lands with a pair of allied colors and their mutual enemy (Khans of Tarkir colors) released in Ikoria and 5 lands with a central color and it's two allies (Shards of Alara colors). They come in tapped, but because they have three basic land types they are easy to find and synergize with many of the other effects. They run from Spara's Headquarters (//) at $5.75 to Ketria Triome (//) at $16.75.
Bicycle Lands
These lands will come in tapped, however I am mentioning them because they synergize with Check lands if played earlier and Reveal lands if in the hand. They range in price from Irrigated Farmland (/) at $0.25 to Fetid Pools (/) at $3.75.
Nap Lands
These lands you can only tap once every other turn and come in untapped, there are two cycles, both ally colored only. The first uses a counter put on when tapping for mana that is removed instead of untapping. These run from Timberline Ridge (/) at $2.95 to River Delta (/) at $4.25.
The other cycle is actually two cycles of 5 which are functional reprints of eachother, all less than $0.25 from Rootwater Depths (/) to Cinder Marsh (/), these can tap for colorless without staying tapped, and use more familiar "does not untap" language.
Other Lands
There are lands that make colors conditionally that could be useful in your deck, like Reflecting Pool ($22) and Exotic Orchard ($0.50) making mana based on what colors you, or your opponents could make. Spire of Industry ($1) costs one life and needs you to have an artifact to make any colored mana and Glimmervoid ($2.50) makes 1 mana of any color but is sacrificed if you have no artifacts in play, Thran Quarry ($6.50) works the same but needs creatures. Aether Hub ($0.25) costs one energy to make any colored mana and Forbidden Orchard ($20) which gives opponents a 1/1 creature for every mana you make with it, but makes any color. Holdout Settlement ($0.25) and Survivors' Encampment ($0.25) both need you to tap a creature to make colored mana.
A little less useful cards that make multiple but not any color, River of Tears ($2) makes  before you play a land for turn or  after. Nimbus Maze ($4.50) can tap for  if you control an island and  if you control a plains, giving you the opposite once you have the other color's basic land type. Grove of the Burnwillows ($4.25) taps for  or  but gives one life to each enemy, something that rarely matters in EDH where overwhelming damage, poison, commander damage and mill are the usual ways of winning.
Other lands restrict how mana can be spent, but without knowing the deck type can't really be suggested. If it's eldrazi(with devoid) there's Corrupted Crossroads ($0.25), allies have Ally Encampment ($0.25), creature heavy decks can make use of Ancient Ziggurat ($4), dragons have Haven of the Spirit Dragon ($2.75), elementals use Primal Beyond ($9.75), Slivers use Sliver Hive ($27), if most of your spells have more than one color in them then use Pillar of the Paruns ($12.50) and Unclaimed Territory ($1) works for any tribal deck since you name the creature type when you play it, and the new strictly better version Secluded Courtyard ($2) which lets you spend the mana on abilities of those creatures. Changeling decks will benefit from all these tribal lands. (except Corrupted Crossroads, and Pillar which care about other characteristics)
Path of Ancestry ($0.50) and Command Tower ($0.25) can both tap for any color in your commander's identity, which means any color in your deck and should be pretty much automatic included in any non-monocolored EDH deck.

These costs can change wildly, Sliver Hive for instance was $7.50 when this post was first written, so check the costs for yourself for these cycles, the header for each section has been made into a link to the results for those cards on scryfall.
Comment: I avoided anything over $10, I mentioned reflecting pool because of the high utility and because I also mentioned orchard, though parts of some cycles are in that range.
Comment: It's probably a more useful answer for the site if it talks generally about 5 color decks rather than Jodah specifically
Comment: Note that the Jodah deck OP mentioned wants all five colors on the board asap, so filter lands are better than usual and Reflecting Pool is worse.
Comment: @JollyJoker I don't see where that was said explicitly, though with Jodah the implication is there, but there is a reason I listed filters 3rd, after bond (always untapped early EDH, no downside) and shock (untapped at the cost of two life) I will admit I missed where it said the deck was Jodah in the original post, pretty much making any of the restricted use lands useless to him.
Comment: @JollyJoker agreed. While Collin won't get any use out of those tribal lands, I've seen Horde of Notions, I've seen Ur Dragon and Scion, I've seen Tazri and I've seen all 4 sliver legends as commanders before, all need good manabases for reliable colors.
Answer: Command Tower is a must-include.
Besides that, there are pretty much five types of multi-colored lands.

Lands that start untapped and have no/minimal drawback (paying 2 life is considered minimal).  They cost a lot of money because they are good.  If you're on a budget, you probably want to avoid this category.  Examples include Tundra, Temple Garden, and Windswept Heath.

Lands that conditionally start untapped.  These are less expensive because they aren't as reliable.  Examples include Dragonskull Summit, Botanical Sanctum, Bountiful Promenade.

Lands that start tapped.  These are going to be cheapest because of the tempo hit, but can have cool other abilities to make up for it.  Examples include Thornwood Falls, Seaside Citadel, Vivid Crag, Terramorphic Expanse, and Flood Plain.

Lands that start untapped but have some other drawback (they tend to involve counters; search t:land o:counter).  These can be cheap but it depends on the drawback.  Examples include Timberline Ridge, City of Brass, Tendo Ice Bridge, Mirrodin's Core, and Gemstone Mine.

Lands that produce any color with some restriction (search t:land o:"any color").  Examples include Ancient Ziggurat, Glimmervoid, Pillar of the Paruns, Unclaimed Territory, and Crystal Quarry.
Comment: I wouldnt ever call tundra, costing over 150 usd, budget friendly.
Comment: @zags meaning you dont actually address the question that was asked, you put lands into categories but never look at the cost/benefit the question is about.
Comment: @Andrew I address the question through the lens of that categorization.  Negative examples can be a useful explanatory technique.  However, I do not include specific price data as that changes drastically with time.
Comment: command tower i always include :)
Comment: @Andrew I didn't call Tundra "budget friendly".  The sentence immediately preceding it describes that category of lands as expensive.  The category is included for completeness in the categorization of multicolor lands.
Answer: You can use the Mirage fetch lands.

Flood Plain ({W}/{U})
Bad River ({U}/{B})
Rocky Tar Pit ({B}/{R})
Mountain Valley ({R}/{G})
Grasslands ({G}/{W}).

and one of the best are the Shadowmoor/Eventide filter land.

Mystic Gate {W/U}
Sunken Ruins {U/B}
Graven Cairns {B/R}
Fire-lit Thicket {R/G}
Wooded Bastion {G/W}
Fetid Heath {W/B}
Cascade Bluffs {U/R}
Twilight Mire {B/G}
Rugged Prairie {R/W}
Flooded Grove {G/U}

good value for the cost.
Comment: the filter lands also seem to be within the 10-15 dollar each price range, which is beyond my budget
Comment: my only concern with any type of fetch land is without shocks and original duals, they seem to lose much of their power, if i put in enough basics for them to work well, it limits my consistency if i draw those basics, and doesn't offer me the ability to tap for either land color, i have to choose what to fetch for based on my current hand, and can easily run into consistency problems later on. In addition, it's slow from the enters tapped trigger, due to the inability to include lands with multiple basic land types, it's honestly even more worth it to run thornwood falls, etc.
Comment: I thing in that case you best option is to build arround green and ramp spells. because artificat can be destroyed to easy.
Comment: i have no more slots left :(
Comment: 2 cicles of lands that are good: lorwing uncomon that comes into play taped have 2 counter and produce mana of any color removing a counter . and the tempsts ones that gives 2 color but dosn't untape if you use for colored mana.
Comment: @NicolasRudisky the goal is to have lands that have a guarantee or a good chance of coming in and being immediately useful, the vivid lands you mention in that last comment always come in tapped, which hits the deck speed
Answer: Most standard sets will have dual coloured lands. With return to ravnica you get the gates, which you can have for each guild and also you get the gates in allegiance. You can use cascade bluffs as well. If you include a chromatic lantern then that should solve your problem as well.
You can also rely on the 3 coloured lands from fate reforged/khans time (can't remember specific set), or the life lands (come into play tapped but you gain 1 life). If you run things like growth spiral and gate summit then you kind of recover on the tempo of your lands coming into play tapped.
Comment: .....
i said in my questions that the tri lands, etb tapped but gain 1, and guildgates were too slow, and that i had no slots left (so no chromatic lantern or growth spiral) cascade bluffs was mentioned earlier, and i said it was out of my price range
Comment: what about painlands? like cave of koilos...
Comment: if you read my original post, you'll notice i said i was already running pain lands
Comment: @CollinB sorry I read it as "plain lands" xD. if shocks are out of question even though they are very low in price at the moment. You will have the cycle lands, checklands, tango lands, fast lands...(amonkhet, kaladesh, BFZ). Maybe even the temples, though still entering tapped the scry might recover the advantage for you...
Comment: my thoughts immediately went to checklands when i first confronted the manabase, but i'm not sure how well they will work, because i'll need basic lands to let them enter untapped, which means i MUST include enough basics for it to work, decreasing my mana consistency. I'm unsure if this will actually be as much of an issue as i think, any opinions?
Comment: chekclands+tainted lands?  you also have the darkwaters catacomb cycle....(dont know their name)...but check lands and tainted lands ensure that at least turn 2 you have for example double black untapped
Comment: @CollinB checklands don't need basics, they need lands that have that subtype, and there are a few cycles of nonbasics that include the subtypes.
Comment: I know, but the majority of them are beyond my price range


When to give up on a hard math problem?

Question: I practice olympiad problems from books like Putnam and Beyond. Often I come across a problem that I simply can't solve. After $\sim30$ minutes of deep thinking it feels like I'm ramming my head into a brick wall, since I've exhausted all avenues of thought I am aware of. What should I do in these situations? Move on to another problem? Give up and see the answer? Or spend more time on it?
Comment: *When to give up on a hard math problem?* - **NEVER !!!**
Comment: The only time you've spent too much time on a problem is if you're beginning to feel frustrated. Like if you're actually pissed off at the problem. This is your mind telling you: "Chill for a bit, do something else, come back to this silly problem later."
Comment: wow, 30 mins! I use to spend hours on a single problem!
Comment: @Lucian Beware, you could end out being one of those people who spends their lives on the Riemann Hypothesis or something...
Comment: "If you can't solve a problem, then there is an easier problem you can solve: find it." - George Pólya
Comment: Half an hour isn't that long. However, the brain is like an engine. If you overwork it too much, it will stop working properly. After certain point, the more you work on the problem, the more unlikely you won't get the answer. Before that happens, you should take a break. Go for a walk, riding bike hard, sitting in front of a lake or anything that let you brain truly relax and rest. Tranquility of mind sometimes works like magic.
Comment: The following link should be relevant for this question http://math.stackexchange.com/questions/461000/strategieswhat-to-do-when-stuck-on-some-math
Comment: @Zarrax: LOL! No, of course not, don't worry about it! $($I'm not one of those people, if that's what you're suggesting$)$. Besides, I've solved it a long time ago, and then moved on with my life.
Comment: Do something else, come back later. "Too much" is highly subjective: 30 min? A Few hours? One day? A week? More? It's up to you. Some mathematicians spend their whole life on a problem.
Comment: The important thing is that you have to quit a problem cofinally.
Answer: My opinion is that you should sleep on it.
Move onto another problem, or just take a break, and come back to it later.
Also, if you've hit a brick wall you may just need to approach from another angle to find the way through.
Comment: Ha-ha, my experience with this is bitter-sweet, sometimes I think I have a solution in my sleep, and when I wake up and recreate it I realize it was a load of baloney.
Comment: Print the problem on a piece of paper and put it under your pillow.
Comment: The mind has a way of working when you're not watching it. Sleep is an excellent way of letting things settle down. maybe to rearrange themselves in your mind.
Comment: *you should sleep on it* - Sleep is overrated.
Answer: EDIT: To be fair, I never directly answered the question when I gave the four following points. I think there is a progression, though. Both (1) and (2) describe feelings you may have that suggest you should quit. My point is that neither by themselves point to giving up on a problem. For (2), I suggest you may need to think about why you want to solve a problem in the first place (note the philosophical nature of my answer to your question). But then, problem solving requires techniques, and asking when to give up is sort of like asking for more techniques. I suggest in (3) and (4) some techniques for progressing the process along that may help if you feel very stuck. Ultimately, you decide how hard you try and when to give up.
(1) That feeling of being stuck and/or somewhat frustrated is typical and part of what you sign up for when you try to solve hard problems. If you are training to be a mathematician you need to get used to this feeling. It's like being a soldier--it's just as much as a lifestyle change as knowing how to shoot guns. You need to cope with it and use it to your advantage. That you are asking this question shows you are starting to do this. I can't say I have it all figured out, but I will say that one of the most important things I learned in grad school is how to be at peace with this addicted/stubborn/frustrated feeling when working on a problem and not getting anywhere.
(2) Do not allow negative or self-derogatory thoughts. You will often think, "I am so stupid, other people smarter than me would have solved this problem ages ago." Or you might think, "Math is worthless, there's too much work and no reward." It is true, other people are smarter than you and will solve the problem faster than you--possibly. So what? Are you doing mathematics to impress other people? Or are you doing it for a job or for your own satisfaction or for your own education?  Now what about math being not worth the effort? Maybe it's true. But there are different difficulties of problems. The Riemann hypothesis is probably too hard. For you, Putnam problems are probably just fine. So try to decide what difficulty is worth it to you. Don't avoid difficulty at all, since then there is no reward at all.
In any of these cases, they reveal a fundamental bias you have about math that should be addressed. Maybe you can't really convinced yourself that math is worth doing. Okay then, pick up something else instead. But just ask plenty of people here and they will have something convincing to say.
If you are truly becoming agitated, and can't beat these thoughts, the best thing to do is to distract yourself with something else. See (4).
(3) Find something of interest in the problem or tangentially related to the problem. When you are stuck, you often become bored of the problem. There is just nothing new you can see! If you could see something new, you wouldn't feel stuck. But have you considered changing the premises of the problem? Have you tried searching for examples or counter examples of the hypothesis? Do any mathematical techniques come to mind, even tangentially, when working on the problem? Think about these things instead. The idea is to find something easy to explore about the problem. Be creative and don't have the goal of solving the problem completely in mind. Have your enjoyment in mind.
(4) Sleep on it, eat lunch, go for a walk, or crumple up the problem statement and dig it out from the trash in a month. Often the ability to solve a certain problem is based on what you have already learned. If you haven't done the hard work of, say, learning a particular inequality derived from Holder's inequality, then it will be impossible to use it in any problem that requires it. Maybe you have learned it but not very well or a long time ago. In that case, you need to give your mind some time to bring it up to the front.
Comment: I agree with everything you said. Particulary, I am so addicted to the incredible frustration you get from a mathematical problem. When you get so wound up and the problem is all you think about and you're constantly going back and forth over everything you know. You feel like an absolute micron of a mathematician and then... poof! You solve it and you feel like einstein. And a month later you go, "that was supposed to be a hard problem?" ^_^
Comment: You made mw cry. This is a very motivational paragraph!!
Comment: @Devilathor, wow, I'm glad you found it encouraging!
Answer: I think, thinking for 30 minutes is not too much. Try hard even for much longer time,
 couple of hours if possible ( A real challenging problem should at least take a day). Write down also the intermediate important conclusions,
so that you don't have to discover them again and again. Personally I love to eat, drink and sleep with a problem, if I see some beauty in it, until there is light at the end of the tunnel.
Comment: "A real challenging problem should at least take a day." Yep. Or a lifetime. Think: Wiles - Fermat's Last Theorem.
Comment: @user18921: I fully agree with you; only thing is that one has to take care of non-negligible constraints from life, in doing that. If one is a researcher and wants to continue his life in academia, he needs to have sufficient publication on almost a regular basis in good journals. In such a situation, I think it safer to invest part of the energy to work on reasonably good and beautiful problems which can be solve in reasonable amount of time.
Comment: @abi, yeah, I basically agree. But I think its okay (even good) to have a problem on the side that is "unsolvable," that you work on when time permits, but which is not integral to paying the bills, so to speak.
Comment: It's true!! Despite you search on Internet for advices or solutions, you WILL spend an entire day!
Comment: Dear user18021, I fully agree with you. My previous reply does not contradict your suggestion. The other part of the energy should definitely be used to solve our dream problem (problems?). Without that, there will always be some feeling of emptiness in the mind (heart?).
Answer: It depends on the problem. Since you've tried a lot of problems already, I think it is not too hard to guess whether the solution is really completely out of your reach. In that case, either you can look at a solution if there is one, or you can simply put the problem aside and wait until you feel that it is within your reach. In the latter case, even years is normal. In my own experience there have been quite a number of such problems that I did not know how to tackle when I first encountered them, but after a few years I suddenly can make the necessary connections to solve them, sometimes even between fields of mathematics that previously did not seem related in that way. On the other hand, if you guess that the solution is somewhat within your reach, you may want to try for a few hours at a time, but with equally long breaks in-between. After a few sessions it will probably become clear if it wasn't indeed in your reach, but along the way you might have discovered other results, which would be nice and rewarding in themselves anyway.
Comment: @Ovi: Yes try and see if it works for you. =) The rationale is that you need to take a long enough break so that when you come back to the problem you have to 'restart' your thinking, which may bring you new insights. If you return to the problem too quickly, you may find yourself treading exactly the same paths as before.
Comment: +1 for  "you may want to try for a few hours at a time, but with equally long breaks in-between." This is something I need to try, if I study intensely for 2 hours, I feel bad if I take more than a 20 minute break
Answer: 30 minutes is nothing. Even for the imo there's supposed to be one and a half hours for each problem, although the last problem is supposed to take up more. For me it depends on how much I like the problem, with problems I don't like I give them 1 hour, however 1 hour of really thinking about it. And if I don't solve it after that I'll look at the solution. However if it's a problem I really like, I can think about it for weeks before thinking about looking for the solution. Something I do a lot of times is go into the unsolved section of mathlinks.ro and do those problems, this is really good for me because I don't have the temptation of giving up and looking the solution, and it's an even bigger challenge. In conclusion, at least 1 hour for me, with no upper bound depending on how much you like it.
Answer: Wait
In his book "Indiscrete Thoughts", the mathematician Gian-Carlo Rota describes another "Feynman method":
"Richard Feynman was fond of giving the following advice on how to be a genius. You have to keep a dozen of your favorite problems constantly present in your mind, although by and large they will lay in a dormant state. Every time you hear or read a new trick or a new result, test it against each of your twelve problems to see whether it helps. Every once in a while there will be a hit, and people will say: 'How did he do it? He must be a genius!'"
Comment: How typical of Feynman. ⁺¹.
Answer: I'd like to add a bit to the other replies (in particular @nayrb's reply):

Indeed when your wheels grind to a halt, stressing them even further would not yield much better results; it is a case of diminishing returns. Stop, rest, do something else for a while, even give yourself a rest for a couple of days before getting back to the problem.
The brain does a lot of processing "offline" - when you're not actively engaging a problem. A lot of it in your sleep. Sometimes when you get back to a problem from last week you'll see that it's "so obvious" that "why was it a problem to begin with"?
Our brains are very context-sensitive, you can see that in phenomena like priming and the "tetris effect". What this means for you is that you might become overly-focused on a single course of action or a single strategy of proof (or even a couple), and lose your "outsider" point of view - weigh too heavily on an analytic geometry strategy, for example, and at some point you start seeing everything through the "goggles" of analytic geometry. And the only way to ease that is taking some time off.
And indeed don't get into a bad mood if you don't succeed for a while. Be reasonable about it: It's a problem, it requires tackling, and tackling takes time. And even if after much tackling and many a day of pondering you did not reach a solution, there's no shame in checking the answers. Not all problems are worth solving on their own merits - from some you'll learn more than from others, and after all it's all a matter of improving your abilities and having fun while doing it. If you come to a sense of exhaustion - not mental or emotional, but of the realm of possible solutions - then you've exhausted the benefit that you can get from a certain problem. And the same holds if there's still some benefit you can get but the process is too long and too frustrating to justify it. It's a matter of cost/benefit, and if there's another problem, the process of finding a solution to is just as fulfilling but more enjoyable or more conducive to your mathematical abilities - move on, it's no shame.
Last but not least, remember that your question is just a special case of problem solving. You may find that some general reading on the subject is helpful both for your particular conundrum as well as for others that might arise in the future.
Answer: The answer for you changes with time.
This is much like the overused joke about the math professor working for $45$ minutes on a problem, looking up, and saying "it's trivial!"  As you work more and more on math problems, you start to be able to work longer without becoming discouraged.  For example, $30$ minutes may seem like forever now, but after working on a ton of (hard/stretching) problems, you'll probably think it seems small.
Always stretch/push yourself, and never lose track of why you're solving the problem.
Of course, if you mean "When to give up on a hard math problem, during competition for strategic reasons," that's a different problem entirely.
Answer: As Piet Hein said in *Grooks*1, "Problems worthy of attack prove their worth by fighting back." Step away from the problem, but come back to it later.

When to give up on a hard math problem?


What to do with overly generic tags?

Question: We have a number of tags so far that seem overly generic, and that don't seem to add a whole lot to the questions they're used on. In particular I'm thinking of engineering, experiment, and technology. Should we keep these tags or get rid of them?
Answer: Note poor tags is worse than no tags. Once we're past early beta, new users will not be able to create new tags until they reach given karma. They must make do with what we have, and considering we have some rather broad subjects, it would be hard to invent all possible detailed tags to cover them all - so let's give them generic tags for now, and retag successively.
Answer: Work to improve the tagging for those questions that can. If there's a tag that is genuinely new, then we'll leave it be, but if a tag set can be improved, it should be improved.

What to do with overly generic tags?