Question about ChaCha20's security

Question: I wonder the Stream Cipher ChaCha20 only changes 96 bits each block,
         why it can produce 512 bits keystream block,
         I mean in the concept of  a random number generator,
         the entropy should be at least equal to the output.
         However,  change 96 bits to produce 512 bits keystream seems have some secure problem.
Comment: What 96 bits? Isn't the block counter for ChaCha20 64-bit? Yes, that's the only change _in input_ of the ChaCha20 "core" from one 512-bit message block to the other, and most often that's a single-bit change from an earlier block. But why would that be an issue? There's the same effect for any block cipher in CTR mode with incremental counter. I'm more concerned with the likelihood of 64-bit nonce collisions.
Comment: In RFC 7539, ChaCha requires nonce not to be repeated with the same key. Thus every block will have different nonce. Plus counter increment, there will be 128 bits input varies. (Though the counter may change one byte only.) We can use the counter with a hash function to generate the needed nonce, thus to avoid nonce collisions.\nMy question is similart to using a small entropy to get a large random number output. Is it secure?
Answer: The fact that few bits change at the input of ChaCha's "core" function does not compromise the security of the ChaCha20 stream cipher.

The design principle of the stream ciphers Salsa and Chacha is to use a "core" function $C:\,\{0,1\}^{512}\to\{0,1\}^{512}$ over the set of 512-bit bitstring (equivalently the set fo 16 words each 32-bit). Among the 512 input bits, 128 are set to arbitrary public constant values $c$, turning the remaining into some function $C_c:\,\{0,1\}^{384}\to\{0,1\}^{512}$.
$C_c$ behaves essentially like a function chosen at random in the set of functions with such input and output domains. In particular, it is conjectured that not knowing $k$ of the 384 input bits chosen at random, the function $C_c$ can't be distinguished from a random function with works less than $2^k$ operations (each requiring a sizable number of CPU cycles), for $k$ up to some comfortable limit (like 160 to 256).
Of the 384 input bits of $C_c$, $k=$256 are for the key, 64 for the nonce/IV, 64 for the counter. The full 512-bit output forms the keystream. As long as the key is random and secret, and the combination of IV and counter value does not repeat, the above conjecture demonstrably implies security of the stream cipher in all common security models, including for related keys.
That's even though, for most blocks of a large keystream, the input of the core function differs by a single bit from the input for another block, and 256 bits (including all those that vary) at the input of the core function are public.

The supporting argument for the stated security conjecture is the design of the core function per $C(x)\gets G^r(x)\boxplus x$ where $G$ is a bijection iterated for $r$ rounds, and $\boxplus$ is a group operation on $\{0,1\}^{512}$. Bijection $G$ is optimized for fast diffusion when iterated.
Note: diffusion is the main area where ChaCha improves (slightly) on Salsa. Another it is that it removes a harmless class of collisions in $C$, see this.
Comment: I can realize the concept you express. However,  could you give  a more formal mathematic proof?
Comment: @MrQ: The proof that if the stated security conjecture on $C_c$ holds, then the Chacha20 stream cipher is secure, is basic to the point of being boring; would that really help? I can't make a proof that the conjecture holds, and AFAIK nobody can, for any symmetric cipher.
Comment: We need more useful and theoretical proof, we discuss the topic in a crypt conference. We had studied many differential cryptanalysis about Chacha, so we don't think it's boring. In contrast, we need more supportive proofs.

Question about ChaCha20's security


Which research groups use stochastic processes and/or stochastic differential equations in computer graphics/vision?

Question: Some research groups use stochastic differential equations for mathematical image processing. Which research groups do use stochastic processes in general and/or stochastic differential equations in the field of computer graphics/vision?
Answer: Here are some examples I like, not of groups but of a few specific works in some areas. For most cases, it's a lot more common to see non-SDE stochastics (e.g. machine learning using stochastics) than, say, explicit simulation of continuous spacetime processes.
Image Super-resolution
In Random Walk Models from Geometry-driven Image Super-Resolution, Fablet et al model the image's level lines using 2D Orstein-Uhlenbeck processes and simulate them to get the high-res image. Also see works like Stochastic super-resolution image reconstruction, Tiana and Mab.
Non-Linear Filtering
Check out the works on shape analysis and geometric flows by Unal et al (Feature-Preserving Flows: a Stochastic Differential Equation's View and Stochastic Differential Equations and Geometric flows). Pretty interesting from a theory point of view.
Graphics
Using stochastics for noise in graphics is pretty common (e.g. flow noise), but for SDEs specifically there are papers like Langevin Particle: A Self-Adaptive Lagrangian Primitive for Flow Simulation Enhancement by Chen et al and Stochastic Modeling of Immersed Rigid-body Dynamics by Xie and Miyata.
Stochastic Motion Textures
See Animating Pictures with Stochastic Motion Textures by Chuang et al. (Check out their videos of animated still images.)
Image Segmentation
In Stochastic Mean Curvature Motion in Computer Vision: Stochastic Active Contours, Juan et al stochastically evolve contours to segment images.
Tracking
On the more vision side, see Learning to track the visual motion of contours by Blake et al, which uses SDEs, and its kin.


How are akka actors implemented on underlying threads?

Question: Given an execution context and a thread pool, how are akka/scala actors scheduled/implemented on that?
Comment: The akka documentation already contains a clear explanation.
Answer: I was confused about this topic for a long time. I assumed that there is some relation between threads and actors. For each actor, there is a thread that hosts it, so I was thinking. Probably there are several actors for each thread that work in cooperative multitasking mode.
Documentation is focused on usage and covers internal architecture lightly. You just should extend the Actor class and you would get a working actor. So I tried to guess how can this be done and imagined that each Actor has life-cycle, something like wait asynchronously for a message queue, then process message and then go to start.
That was a totally false assumption. Although the documentation says "actor life-cycle" it does not mean Actor life-cycle. Actor mentioned is a conception rather than an actual object implementing the Actor class. The object resides passively in the java heap.
To breathe life into the conception, coordinated work involving a bunch of real workers is needed. And the heart of it is a dispatcher. It holds all actors, threads, and messages. And when the resources become available and there are messages available for processing the dispatcher activates. It takes an appropriate Actor object, wraps its receive method in runnable, and passes it to a spare thread. So there is no life-cycle for the object only occasional method calls from the actor system.
When you think of it, it makes much more sense than the scheme I assumed earlier. But it was hard for me to deduce it from available documentation. It was written by seasoned concurrency programmers. The distinguish holding the actor class from actor conception behind it. They know that dispatcher for an actor system is like a task scheduler for an OS. So they quickly get to the point and describe various flavors and realization of the conception assumed to be familiar to everyone.
But that is not so easy for a newbie. He has no acquaintance of the dispatcher pattern in the actor systems context. I tried to google "dispatcher pattern" and it showed definitions non-relevant to the actor system.
I've found easily double dispatch, multi-dispatch, and other OOP topics. I've found something similar to Akka's routers message dispatcher. There is probably a decent description for actor message dispatchers but it not so easy to find.
I hope I've cleared the misunderstanding.
Comment: Thanks for explaning, I had the same experience
Answer: On 'I was looking into something more like say you are given a thread pool of 10 threads and 50 actors spun off of it, how are so many actors handled by a batch of 10 threads?'
The exact behavior depends on the dispatcher and configuration. However, most dispatchers do basically something like this:

Select an actor which has a non-empty mailbox
That 'actor' is then dispatched to run on the executor
Where messages are dequed and processed.

When possible, a few messages are dequed and processed one after another
After processing some messages (or none left), another actor is picked, to prevent starvation. (throughput parameter)

Rise and repeat
Answer: You can find relevant information in the akka documentation which is pretty complete as far as thing goes.
Essentially you can select/define dispatchers and assign actors to them through configuration (via files or code).
Each dispatcher implementation is then based on some sort of executor.
Comment: Thanks for the reference. I was looking into something more like say you are given a thread pool of 10 threads and 50 actors spun off of it, how are so many actors handled by a batch of 10 threads? Will looking more at ExecutorService help?
Comment: probably you could have detailed answers on the [akka user list](https://groups.google.com/forum/?pli=1#!forum/akka-user)


Intel NUC running Xubuntu spontaneously suspends and won't wake up

Question: I recently ordered an Intel NUC 5i5RYH with a Samsung Evo SSD and 2 x 8GB GB Crucial RAM.
I attempted to install Ubuntu 14.04 on it but I had problems with it suspending before I could even finish the installation process. It would just suspend for no apparent reason. I even sat there moving the mouse through the whole process to try to prevent it, but it still suspended.
I read somewhere that 15.04 works better with the NUCs and several reports of Xubuntu working, so I gave that a shot (64 bit version). I did at least manage to get it installed and working, but it still randomly suspends. Sometimes it suspends immediately upon booting, other times I can use it for five or ten minutes before it suspends. It does this even though I have set it to never suspend in the power settings.
One thing I've noticed is that when I was trying to install Chrome, it always suspended when going to google.com/chrome, even though I was able to navigate to several other sites (this one included) without apparent issue. It does this on Chromium and Firefox.
But I don't have to go to that site for it to suspend. It does it eventually no matter what. Even if I'm not logged into the GUI. It will suspend if it sits on the login screen for a while, or if I hit F6 and use the terminal there.
Once it suspends it won't wake back up no matter what I do.
I can confirm that the computer is suspending, as opposed to running along but not sending output to the display, because I also lose SSH access when this happens.
I've tried enabling and disabling secure boot. No change. Before I realized I couldn't shell into it, I thought it might be an issue with the display and installed mesa-vdpau-drivers as described in this question. No change. I read that it can suspend due to overheating, so I tried changing the fan settings to more aggressively cool the CPU. No change.
I'm about ready to call the dang thing defective and send it back. However, I'm really hoping that there's a software fix somewhere. Or short of that, I'd like to know if there's a way I can diagnose the hardware problem. Any help is, of course, much appreciated.
Answer: How do you know it suspends? Can you wake it up somehow ? You write you can't right ? Seems more like freezing. How about memory problem ? Try to run mem test. Most of distros have it on live cd. Check the volage of you memory chips. Maybe try to install xubuntu with just one memory plate.
I have xubuntu runnig in production NUC for about year and I didn't see any freeze up yet.


Can't find the admin tab v.1.6.9

Question: I am currently trying to update my website that I have not touched in years. It is still using EE 1.6.9, and while I was following the update instructions, I came across a hiccup. The instructions tell me that I need to clear the cache, which is found under the admin tab, but there is no admin tab. It goes Edit, File Manager, Pages, Modules and then My Account. I originally hired someone who built the website, and then transferred everything to me so I am confused as to why this is happening.
Comment: Probably the effort of upgrading from EE1.6 to EE5 is very high. You should consider dumping the relevant data, creating a fresh EE5-install and importing the data. If you are not able to do this by yourself the costs of a commercial EE-supporter most probably would be much lower than realizing the whole upgrade-process. All of this mostly depends on how many addons und how many custom-code your recent installation is using.
Comment: I won't edit my answer, but I think I agree with @BNetz. You very likely have a smoother path by essentially rebuilding in a new installation and importing your old data/templates/assets rather than actually upgrading from EE1.6 to EE5.
Answer: First of all, kudos to you for taking on an EE upgrade project yourself. I am going to warn you that it is non-trivial, and I generally recommend you hire a professional EE developer to do the job. You may have a hard time finding advice for upgrading a 9 year old version, but there may be an old-timer around here somewhere with a better answer.
Most likely the reason you can't see the Admin tab is because your user is in a member group that doesn't have access to the Admin tab. I'm not sure if it works that way with EE1.6.9, as I've only worked with EE2 sites and up, and in EE2+ sites, that is an access permission that can be turned off for any non-SuperAdmin member group.
I also see that your Control Panel is not properly loading themes (I removed the image you posted because it was easy to identify your website, and an 8.5+ year old CMS is going to have security vulnerabilities, so you don't want to advertise who you are), meaning there is likely a path configuration issue, or possibly an expired SSL certificate for your site.

Can't find the admin tab v.1.6.9


Does sending email with TLS help to not being flaged as spam?

Question: Does sending email with TLS help to not being blocked or not being flagged as spam by recipient?
Comment: Are you referring to SMTP TLS? (the `STARTTLS` extension)
Comment: I think it would be difficult to provide a universal answer to this as it depends on the configuration of the spam filter on the recipient's email server. Different filtering engines work differently and they are usually customizable, not to mention that most commercial mail services don't publicize the inner workings of their spam filters. So while use of TLS can certainly be a factor considered by spam filters, it is difficult to know for certain how any particular server will respond to it.
Answer: There are two sides of sending email encrypted via TLS:

Between the sender and the email provider
Between the email provider of the sender and the receiver's email provider (spam filters typically sit here)

The security of the first connection has no impact on the spam rating on the receiver's side.
However, the spam filter on the receiver side might consider the encryption of the inbound connection in his spam rating or even completely deny unencrypted emails.
As tlng05 mentions in his comment, commercial email providers typically don't talk about how their spam filters work in detail. However, as Gmail (just as an example) marks every email that came in through an unencrypted connection with a red lock, it is quite save to assume that encryption has at least a little impact on the spam score - if not technically, then psychologically (at least for Gmail users).
Answer: No. It only protects the email in transit.
Typically, you need to use TLS in two places. Firstly between the two email servers and secondly between the client and their email server.
Trust in the contents of an email is a different matter though clearly if someone has gone to the trouble of ensuring an end-to-end encrypted channel, they are likely to whitelist the sending domain. That would of course most likely make it trusted.


How to duplicate heads on a MacBook Pro

Question: I've been trying to copy unique player heads to look at and decorate my maps and homes with, but instead of getting the head of a player when I control+middle click, I get Steve's head. Is there any way to do this another way? Any advice would be appreciated.
Comment: Cmd + Middle click
Answer: According to a user named quartz in the comment section of a related bug, the way to copy a block including its NBT data is slightly different on a Mac. It is done via CmdPick Block (default is Mousebutton 3), rather than CtrlPick Block.
You can verify that this worked by mousing over the item in your hotbar. It should say "+NBT data" in purple.
Comment: @ModDL using html tags: `Ctrl`. I think it's explained under "Advanced Formatting help". Pro-Tip: [edit] the answer to see the unformatted version.
Comment: Just curious how did you type the buttons?
Answer: Hey I actually just figured this out by accident!
-Tap CMD and PickBlock together quickly
If that doesn't work try this:
How to pick block + NBT (MAC)

Hold CMD + [PickBlockBind]
Release CMD & immediately hold it back down again
Block should copy the block and its NBT!
Answer: The player head is unavailable in Survival minecraft. The only means to obtaining a specific player head is through commands. Player skulls have the nbt tag of SkullOwner which can be specified to get a particular player's skull.
Due to the fact that the SkullOwner is an NBT tag, it is possible to duplicate the head in creative by using the NBT pickblock function, which involves using pickblock whilst the Ctrl key (if on a Windows operating system) or The Cmd Key (if on an OSX operating system).
Using the website Minecraft Custom Heads it is possible to generate heads that are not someone's head.
Answer: In creative if you already have 1 of the player head and you just want to duplicate it you should be able to simply use <PickBlock>. You can check your keybindings under Menu->Controls to find out what you have it bound to.
In creative you can use <Left-Shift> + <PickBlock> to copy NBT data as well but shouldn't been necessary with player heads.
Using the command /give <YourName> minecraft:skull <qty> 3 {SkullOwner:"HeadYouWant"} Where the 'qty' is the number of heads you want.
Comment: Killing a player will never drop their head. Ctrl + Shift + MiddleClick Does not copy NBT, and He is looking for the Mac Equiv.
Comment: @ModDL I updated the answer. Taken straight from minecraft wiki.

How to duplicate heads on a MacBook Pro


What am I doing wrong when proving the add_right_cancel theorem?

Question: So, as mentioned in my previous two questions, I have been using The Natural Number Game to help me teach myself how to use the mathematical proof assistant Lean4.
I am currently trying to complete the Advanced Addition world so I can get access to the "≤ World"1 so I can more easily prove the clunky version of Fermat's Last Theorem2, and for some reason I am currently stuck on proving the add_right_theorem (Level 1 of Advanced Addition World), which states that$$a+n=b+n\implies a=b$$which I don't exactly know how I would state the proof or write it out in Lean4
Here's what I have done so far:

The first part (the proof by induction) is pretty easy. All I need to do is this:

induction n with d hd
repeat rw [add_zero]
intro h
exact h

however the second part$$a+\operatorname{succ}(d)=b+\operatorname{succ}(d)\implies a=b$$is where I am struggling. All I can do is add the successions together to rewrite it as$$\operatorname{succ}(a+d)=\operatorname{succ}(b+d)\implies a=b$$before being forced to introduce the hypothesis h to rewrite it as this:
hd: a + d = b + d → a = b
h: succ (a + d) = succ (b + d)
Goal: a = b

Now, when I apply succ_inj at h, it leaves me with
hd: a + d = b + d → a = b
h: a + d = b + d
Goal: a = b

and now I'm stuck, because I can't use decide since that returns the exact same thing, and triv doesn't work since the case "True" doesn't exist. (I got a bit desperate, sorry.)
Here is my proof so far:
induction n with d hd
repeat rw [add_zero]
intro h
exact h
repeat rw [add_succ]
intro h
apply succ_inj at h

So my question is: Where am I messing up the proof of the add_right_cancel theorem, and how should I actually go about proving it?

1I'll replace this with \le if it would look neater, the unicode for the "less than or equal to" symbol is u+00264 for anyone who wants to know.
2The more clunky version of Fermat's Last Theorem (that is, the first case of it) comes up in Power World level 10/10, and states that for no $a,b,c,n\in\mathbb N$,$$(a+1)^{n+3}+(b+1)^{n+3}=(c+1)^{n+3}$$which is where the Inequality World would come in handy, because it would greatly shorten the proof. The first case has been proven in Lean.
Answer: From
hd: a + d = b + d → a = b
h: a + d = b + d
Goal: a = b

you can use the apply tactic.


On NUC6i5SYK Ubuntu Linux 15.10 display goes to sleep immediately after splash screen appears

Question: I installed Ubuntu Linux 15.10 from a USB thumb drive on my NUC6i5SYK.  I had to add nomodeset to get the LiveCD environment to boot, as the display would sleep if I didn't (as described here: Intel NUC NUC5i5RYH - Boot - only mouse pointer appears (Xubuntu 14.04, 14.10) - Ask Ubuntu and other places).  I was able to successfully install Ubuntu from the LiveCD environment.  Now I see the same issue with the installed version, i.e. it gets to the purple background and the display immediately sleeps.  I'm connecting to a Dell U3415W via mini-DisplayPort.
I can boot the recovery mode GRUB menu item and then select resume the normal boot and it appears to work fine.  Yet it consistently puts the display to sleep with a normal boot.
Things I've tried that haven't resolved the issue:

Adding i915.preliminary_hw_support=1 to GRUB boot configuration, per Early Intel Skylake Linux Users May Run Into A Silly Issue - Phoronix and other sources
Updating Intel Linux Graphics drivers to latest Ubuntu release Intel Graphics Installer for Linux* 1.2.1 | 01.org
Installing Kernel 4.3 drivers - No version of Ubuntu can be installed with any Skylake 6th generation Intel processor - Ask Ubuntu
Installing Kernel 4.4 drivers with the missing Skylake firmware file Installing 4.4 rc7 kernel yields i915 module not available

Any ideas?
Comment: I was able to get it booted into Ubuntu using `nomodeset`.  Would still like to get the graphics drivers working properly.
Comment: When I connected via HDMI instead of mini-DisplayPort, Ubuntu booted normally.  Sound was working as well, which wasn't working with the DisplayPort interface, in addition to the issue described above.
Answer: I had the same issues as you. I have a Dell U3415w monitor, and when I disabled DP1.2 in the OSD, it worked fine. Both picture and sound.


Are generalised coordinates truly independent?

Question: Say we have a system with two generalised coordinates $x$ and $y$. When we solve the equations of motion we find $x=x(t)$ and $y=y(t)$. I can invert one of these solutions to find $t=t(y)$ and therefore get $x=x(t(y))$ which therefore gives me $x(y)$. Does the equation of motion impose a constraint? Are generalised coordinates independent?
Comment: [This answer of mine](https://physics.stackexchange.com/a/307805/50583) addresses a related confusion. Upshot: You need to distinguish between the *coordinates* $(x,y)$ of the state space and the specific choice of a *path* $(x(t),y(t))$.
Answer: You are losing information by doing that transformation.  In particular, you will only know about the orbit of the particle, and will lose all information about the velocity.
In general, a generalized coordinate transform from a set of $x^{a}$ to a set of $y^{a}$ will only be valid if, for the matrix $M_{ab} = \frac{\partial y^{a}}{\partial x^{b}}$, you have ${\rm det}\left( M_{ab}\right) \neq 0$
Answer:
When we ask if generalized coordinates $q^j$ are independent, we by definition mean before using any differential$^1$ equations of motion. A differential equation of motion is by definition not considered a constraint.
Generalized coordinates could be dependent if we have further constraints implemented via Lagrange multipliers.

--
$^1$ By equations of motion, we mean Lagrange equations (as opposed to purely kinematic identities). By differential equations of motion, we mean equations of motion with time derivatives.
Answer: You shouldn't try to make $t$ a coordinate; it's a label for the coordinates, over which the coordinate-dependent Lagrangian is integrated to form the action. (The most obvious problem this causes is that the momentum of time is undefined, viz. $\frac{\partial L}{\partial \dot{t}}=\frac{\partial L}{\partial 1}$.) It would be like trying to change the fields in a theory so one is replaced with the spacetime coordinates that label the fields (note these are integrated over to obtain a field theory's action, which is any fields are analogous to generalised coordinates).


Deciding test statistic and distribution for a random number test

Question: How do u decide on a test statistic while developing a test for random number testing and its likely distribution. How do u calculate and decide on the formula for calculating a p value for the test statistics distribution.
TIA
Answer: What is the likely distribution in the first place? Is it a normal one, a uniform one, ... I guess that random numbers should be uniformily distributed, and this is something you can test by using the appropriate Kolmogorov-Smirnov test. Basically you decide on that by applying the correct statistical methods. If you don't know the KS test, please ask advice to a statistician. This is not something you can easily implement and interprete yourself without some decent guidance a website like this cannot give you.
By the way, if you take enough random numbers, any test will show a deviation from the proposed distribution. The best way of judging a distribution is an expert look at a QQ-plot. This is all done very easily in R.
If you need more information, ask a more detailed question at stats.stackexchange.com
Cheers


Why does this sheet music say A7sus42?

Question: In the sheet music below, there is an A7sus42 notation above the 2nd half of the measure. However, the left and right hands only play A, D, G which I thought should just be an A7sus4 chord. Is my understanding correct? If so, why did the arranger bother including the the 2?
Comment: Is the score an arrangement from a different instrument or ensamble? Perhaps there was A7sus4/2 → A7 in the original. It's a very typical progression on a dominant chord in classical music.
Comment: The piece is Canon I'm D, which I think was originally composed for a 4 voice ensemble (violin 1,2,3 and a Bass voice). Maybe in this part of the piece, the B is covered by one of the voices.
Answer: First consider the larger question of why the arranger included chord symbols at all. They're there, of course, for a performer who prefers to play from them rather than from the "dots". So the "real" chord is as given in the chord symbols, but for the purposes of the piano arrangement, the B (and, less significantly, the E -- the chordal fifth, which is often omitted) was dropped. At a guess, there just wasn't a good place to include it. The voicing is so close that the B would just muddy the sound. An alternative would have been to drop the left-hand A an octave, and have the right-hand play B-D-G-A, with the B-D moving to the C#.
Comment: Time and again, I'm finding the chord symbols and the associated dots differ. Mostly it seems to be sloppy writing. I have to refer to full scores sometimes, to determine which is most appropriate, or listen to everyone play and decide by ear (and instinct!). I'd have thought here that the dots were more accurate, partially as A7sus2,4 isn't a common chord - it's either or.

Why does this sheet music say A7sus42?


Difference between Mage::getModel('core/email_template_mailer') and Mage::getModel('core/email_template');

Question: What is difference between Mage::getModel('core/email_template_mailer') and Mage::getModel('core/email_template');?
Comment: Please explain what you want to know. Was the answer given by Anshu what you expected? Or do you know how magento resolved class names and you want to know what the difference between the classes is?
Answer: Looking at the docs for core/email_template_mailer and core/email_template it seems that the first one has methods to send the template that you generate using the second one. I'd guess someone else can explain it a bit more but that seems to be what is happening to me.
Answer: Mage::getModel() is used for creating objects of model classes.

Mage::getModel('core/email_template_mailer') will create object for
  class app/code/core/Mage/Core/Model/Email/Template/Mailer.php

Mage::getModel('core/email_template') will create object for class
  app/code/core/Mage/Core/Model/Email/Template.php

For more details and methods they contain, you can see these classes at their respective locations as mentioned.
You can always read Mage::getModel() like below

Mage::getModel('classGroupName/path_to_model_file');


Difficulty in making out adjective endings when listening

Question: I am trying to learn German by watching movies and pocasts,  but one problem I have is that I always have difficulties making out the adjective endings when people speak. Any tips on how I could train my ears for it?
Comment: When I was a kid, pretty much the only mistake I made in writing tests was confusing `dem` and `den`. You can't hear the difference well in my parents' spoken German, they usually don't even say the whole article (and I guess the same is true for me). I still sometimes need to substitute the noun with a female noun to be sure about the correct case (and during those tests you didn't have the time). So, I guess, the answer is "You can't."
Comment: Know the grammar and hence know what ending to expect :) Btw, not an adjective, but I wonder whether the difference between "ein" and "einen" when I say them is sometimes only in my head.
Answer: Spoken German has three kinds of syllables:

betonte Silben (stressed syllables)
unbetonte Silben (unstressed syllables)
Reduktionssilben (reduction syllables)

The last kind (reduction syllables) appears only as last syllable of many German words (mainly inherited words, i.e. words that have been part of the German language for many centuries). This kind is even less stressed than unstressed syllables. With the usual pronunciation of reduction syllables, the syllable is rather murmured than spoken.
In spoken German language we have two vowels, that only can appear in these reductions syllables, and they sound very similar:

Examples where the last sound of the word is the schwa sound a.k.a. mid central vowel. This is one of the sounds that come out of your mouth when you simply open your mouth a little bit, let your lips relax, and let your tongue rest loosely in your mouth.
IPA-symbol for this sound: [ə]

jede [ˈjeːdə]
schöne [ˈʃøːnə]
große [ˈɡʁoːsə]
diese  [ˈdiːzə]

You find this sound also in unstressed syllables of many English words:

sound for the letter "a" in "about": [əˈbaʊ̯t]
sound for the letter "e" in "taken" [ˈtʰeɪ̯kən]
sound for the letter "i" in "pensil" [ˈpʰɛnsəl]
sound for the letter "u" in "supply" [səˈpʰlaɪ̯]

Examples where the last sound of the word is the near-open central vowel. This is another sound that can come out of a fully relaxed mouth. The only difference to the sound described before is what the base of your tongue does in the throat.
IPA-symbol for this sound: [ɐ]

jeder [ˈjeːdɐ]
schöner [ˈʃøːnɐ]
großer [ˈɡʁoːsɐ]
dieser  [ˈdiːzɐ]

This sound is a sound that is used in no English word as its standard pronunciation. Therefore the sound [ɐ] is not listed as one of the vowels to pronounce English words in the wikipedia article about English phonology. But many English words that should be pronounced with [ʌ], but also [ə] are spoken with a sound very similar to [ɐ] by many English native speakers.
The wikipedia article about the near-open central vowel claims, that  in Australia the letter "a" in "calm" is pronounced as [ɐ] ([kɐːm]; but elsewhere [kɑːm]) and that in California English native speakers use [ɐ] to pronounce the letter "u" in "nut" ([nɐt]; elsewhere [nʌt]). But I can't verify that.

The fact that [ɐ] is not a standard vowel of English, and that [ɐ] and [ə] are sometimes used as allophones in spoken English, means that native speakers of English never have a reason to learn to hear the difference between [ɐ] and [ə]. (Allophones are different sounds that can be freely interchanged without changing the meaning of even a single word.)
But in German the difference between [ɐ] and [ə] indicated the difference between masculine and feminine attributes of nouns.

German reductions syllables can also also have other kinds of pronunciation. Sometimes they are pronounced without any vowel, but with a vocalized consonant. But thats another story, beyond the scope of your question.
Comment: What is with [ʌ]?
Comment: @ReineAbstraktion: Spoken German has between 20 and 30 different vowels, [depending on how count them](https://german.stackexchange.com/q/34755/1487)), but [ʌ] is none of them.
Comment: +1.I concur. Though some dialects might have the sound as by the example given here: https://en.m.wikipedia.org/wiki/Open-mid_back_unrounded_vowel
Comment: @planetmaker: Please do not post links to en.m.wikipedia.org or de.m.wikipedia.org. Please remove the part "m." and post only links to en.wikipedia.org or de.wikipedia.org. The "m." in the URL indicates the version that is optimized for mobile devices (phones and tablets). But on large desktop screens like on my 32" monitors this mobile layout looks ridiculous. When you remove the part "m.", users of large devices will see a version that is optimized for them and users with small devices will automatically be redirected to their mobile version within milliseconds.


How to get mongrel working with bundler?

Question: Transitioning to bundler with an existing production setup. Naively with a gemfile and setup like:
gem "rails", "2.3.8"
gem "mongrel", git: "http://github.com/dynamix/mongrel.git"

bundle install --path /mnt/app/shared/bundle

Starting with
bundle exec mongrel_rails start --environment=production ...

results in
/mnt/app/shared/bundle/ruby/1.9.1/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:166:in `require':
no such file to load -- /mnt/services/shared/bundle/ruby/1.9.1/gems/mongrel-1.2.0.beta.1/lib/mongrel/init.rb (MissingSourceFile)

What to do?
Answer: To answer my own, since I couldn't find a correct solution elsewhere on the web for this scenario:
The problem seems to be an interaction of bundler and mongrel's use of the gem_plugin.  Yes, these may be on life support but unfortunately lots of people's production configs still depend on them.
Seems that with mongrel --pre installed from the git source, it's looking in bundle/ruby/1.9.1/gems/mongrel_ instead of bundle/ruby/1.9.1/bundler/gems/mongrel_ which is where bundler is stashing the gem cloned from git.
So the solution that worked for our config is to just symlink them:
ln -s /mnt/app/shared/bundle/ruby/1.9.1/bundle/gems/mongrel* \
 /mnt/app/shared/bundle/ruby/1.9.1/gems/mongrel-1.2.0.beta.1

This is clearly something simple that bundler could do automatically.  Full trace of the exception was:
/mnt/app/shared/bundle/ruby/1.9.1/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:166:in `require':
 no such file to load -- /mnt/app/shared/bundle/ruby/1.9.1/gems/mongrel-1.2.0.beta.1/lib/mongrel/init.rb (MissingSourceFile)
    from /mnt/app/shared/bundle/ruby/1.9.1/gems/activesupport-2.3.8/lib/active_support/dependencies.rb:166:in `require'
    from /mnt/app/shared/bundle/ruby/1.9.1/gems/gem_plugin-0.2.3/lib/gem_plugin.rb:134:in `block in load'
    from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems/source_index.rb:241:in `each'
    from /usr/local/lib/ruby/site_ruby/1.9.1/rubygems/source_index.rb:241:in `each'
    from /mnt/services/shared/bundle/ruby/1.9.1/gems/gem_plugin-0.2.3/lib/gem_plugin.rb:112:in `load'
    from /mnt/app/shared/bundle/ruby/1.9.1/bundler/gems/mongrel-f3e69eb8e6fb/lib/mongrel/configurator.rb:231:in `load_plugins'


Creep behavior in metals

Question: If creep behavior can begin at 0.6T(melting) but, hot working for a pure metal starts at 0.4Tm, what is the explanation for this?
Comment: Are you implying there is some issue with the creep temperature being hotter than the hot working temperature? Is so, I think you need to clarify why you think that is an issue. After all, you can cold work a metal at 0Tm. Is that an issue because the temperature is lower than the creep temperature?
Comment: Your assumptions are wrong for the real world. Carbon steel ( MP 2700 F) creeps at 800 F and probably at 700 F ( if you wait long enough.).
Answer: Hot work involves macroscopic deformation of the metal; no time is allowed for creep to take place so the concept of "creep" as such doesn't exist during hot work.
The objective of hot work is to deform the workpiece to its desired shape at a temperature at which it happens to be easily malleable and will not strain-harden in the process. This means that the temperature you choose depends on exactly how soft you want it to get and how hot you need to get it so that solid-state diffusion through the lattice is more or less fully activated.

Creep behavior in metals


Friction versus ratcheting pawl

Question: We are working to design a lock mechanism and need to hold a square plunger out of a hole for extended periods of time (potentially years). The square plunger is under pressure from springs to return to the hole. Initial testing with a friction pawl has been positive, but we wonder about maintaining grip over a longer period of time. The pawl is lightly spring actuated to maintain forced contact with the plunger surface at all times. Does anyone have experience with friction pawls and in particular why these are not as commonly used as ratcheting pawls? They seem to grip quickly and if angled correctly seem to hold on. Are there pitfalls we are not aware of over the longer term? Thank you for any thoughts.
Answer: Doesn't a boating cam cleat work in that fashion?

Image source: Schaefer Marine.
The harder the rope is pulled (to the left) the tighter the cleat bites it. If you can do the same with your friction pawl it too will lock onto the plunger even with wear over time.
The other device that comes to mind is the Sprague or one-way clutch.

Image source: SUMA Clutch and Bearing.
On this one the roller bearings will bite if the inner ring turns clockwise and will freewheel if the inner ring turns anti-clockwise. (Note the increased clearance on the anti-clockwise side of each roller bearing.)
Comment: Thank you for the response. That is essentially how it works, though we are trying to keep a hard, flat metal plunger in place with a metal friction pawl. Those examples all work, but they also have teeth, whereas a friction pawl would not. I am mainly seeing these sort of solutions with teeth on them, and wonder if there is some sort of pitfall in a friction only (non-toothed) pawl that I need to worry about. Teeth would be hard for us.
Comment: The Sprague clutch doesn't have teeth. The rollers never get as far as the hard stop before they bite. You, effectively, have one section of that clutch.

Friction versus ratcheting pawl


Estimating angular velocity from position

Question: If you have two position estimates $P_{t_1}$ and $P_{t_2}$ and times $t_1$ and $t_2$ how do you extract the average angular velocity from them? The linear velocity is a simple difference but how do you compute angular velocity?
Comment: As the answer from @robotsfoundme indicates, it would be helpful to expand on what the Ps are. As it is now, the term 'position' can be interpreted as 2 or 3D vectors without orientation information. '_pose_ estimates' may be clearer, but even better to specify exactly the quantities you are working with: roll, pitch, yaw, or rotation matrix or quaternions? One can be converted into the other, but there may be specific methods for each.
Comment: Lets assume Euler angles or a rotation matrix but I am reading up on Quaternions.
Answer: You don't
In order to have an angular velocity, you have to be able to show that there is an arc in the trajectory. Representing arcs requires 3 points on the trajectory, and you only have 2. You need 1 more point or one more piece of information to get the angular velocity.
Comment: What? You have a 6 dof position vector for each position, there should be a way using linear interpolation to estimate the transformation between the two poses right>
Comment: As the accepted answer identified, there aren't enough details in the question to answer properly. I answered with the minimal information available at the time. In the general sense, you are correct @FourierFlux.
Answer: Clarifying the question
The question needs more clarity. For example, you need to explain the positions are of what, with respect to what, resolve in which frame.
Let's assume the positions $P_{t_{1}}$ and $P_{t_{2}}$ are positions of some arbitrary point $b$ on the robot/body, with respect to an arbitrary point $a$ in the world (e.g., origin of the map). Furthermore, let's assume the positions are resolved in the world frame $\mathcal{F}_{w}$.
The position of the robot/body $b$ with respect to the point $a$ at time $t$, resolved in the world frame $\mathcal{F}_{w}$ can then be described as $\mathbf{r}^{b_{t_1}a}_{w}$ and $\mathbf{r}^{b_{t_2}a}_{w}$.
Angular velocity from a motion model
The angular velocity describes the rate of change of frames, and not of points.
Thus, asking for the angular velocity from two points is an ill-posed question.
Perhaps what you meant to be asking is the angular velocity of a rigid body, which has a reference frame, given the rigid body's position.
To compute the angular velocity of a rigid body given it's position requires using its motion model.
The motion model is usually in the form
$$
\begin{align}
\mathbf{x}_{k} &= \mathbf{f}(\mathbf{x}_{k-1}, \mathbf{u}_{k-1}),
\end{align}
$$
where $\mathbf{x}_{k}$ is the state and $\mathbf{u}_{k}$ is the control input  at time $t_{k}$, which may include the angular velocity.
Thus, computing the angular velocity would require computing $\mathbf{u}_{k-1}$ from $\mathbf{x}_{k-1}$ and $\mathbf{x}_{k}$.
If $\mathbf{f}$ is invertible, then the control-input is computed using
$$
\mathbf{u}_{k-1}
= \mathbf{f}^{-1}(\mathbf{x}_{k}, \mathbf{k-1}).
$$
Let's consider a 2D rigid body example, where the state is the robot's displacements $\mathbf{r}^{b_{k}a}_{w}$ and its heading $\theta_{k}$ at time $t_{k}$.
This state can be "nicely" described using the special Euclidean group $SE(2)$ (check Sola - A Micro Lie Theory for more info on Lie groups for robotics):
$$
\begin{align}
\mathbf{T} &=
\begin{bmatrix}
\cos(\theta) & -\sin(\theta) & x \\
\sin(\theta) &  \cos(\theta) & y \\
0 & 0 & 1
\end{bmatrix}
=
\begin{bmatrix}
\mathbf{C}(\theta) & \mathbf{r}^{ba}_{w} \\
\mathbf{0} & 1
\end{bmatrix}
\in SE(2).
\end{align}
$$
Let the control inputs be the linear velocity of the robot resolved in the body frame $\mathbf{v}^{b_{k}a}_{b_{k}}$ and the angular velocity $\omega^{b_{k}w}$.
The motion model is then
$$
\mathbf{T}_{k}
=
\mathbf{T}_{k-1}
\begin{bmatrix}
\mathbf{C}(\Delta t_{k-1} \omega^{b_{k-1}w}) & \Delta t_{k-1} \mathbf{v}^{b_{k-1}a}_{b_{k-1}} \\
\mathbf{0} & 1
\end{bmatrix},
$$
where $\Delta t_{k-1} = t_{k} - t_{k-1}$ is the sampling period and $\mathbf{C}(\cdot)\in SO(2)$ is the rotation matrix constructed from $\Delta t \omega^{b_{k-1}w}$.
Going back to the original question, if you have the full states at times $t_{k}$ and $t_{k-1}$, which include the displacements and headings, then the angular velocity can be computed using
$$
\begin{bmatrix}
\mathbf{C}(\Delta t_{k-1} \omega^{b_{k-1}w}) & \Delta t_{k-1} \mathbf{v}^{b_{k-1}a}_{b_{k-1}} \\
\mathbf{0} & 1
\end{bmatrix}
=
\mathbf{T}_{k-1}^{-1}\mathbf{T}_{k}.
$$
Note on computing arbitrary points
The kinematic motion model presented above may not be applicable for your application.
For example, if the point $b$ is not exactly on top of the robot wheel (for the $SE(2)$ example above), then the kinematic equation would probably be slightly different, so you'll need to derive the kinematic equation for that model.
Note on non-invertible motion models
If the motion model is not invertible, then perhaps using (nonlinear) least squares is your best bet.
Nonlinear least squares is the basis of some estimation algorithms such as the (extended) Kalman filter.
For example, this approach would be applicable if you're trying to estimate the angular velocity using position estimates from a GPS.
In such case, you need at least an initial guess of the heading. Otherwise, the problem would be non-observable.
Comment: This makes sense, I didn't think about the motion model aspect of it which would imply the linear interpolation. In my case it's 3 position 3 orientation dimensions but the same idea applies.  This is WRT the center of mass of the body.


Skype Installation on Elementary OS

Question: I am a new Linux user, I am using Elementary OS and not much familiar with its features. I want help with skype installation. I have downloaded the skype from official website, however, I dont know how to install it on my laptop.
Thanks
Answer: have not tried this but it should work ...

download the "DEB" package for linux (remember where it is downloaded)
You can install it by using sudo apt install ./name.deb

this assumes you are in terminal app in the directory where the file exists
or you could specify the full path name of the file
Answer: George Barbaz is right, his answer should work just fine.
How ever, here is a maybe more detailed explanation, because you stated you are new to the linux world:
Open the files application and navigate to the folder, where the file you've downloaded is stored.
Right-click and click on 'Open in' ➝ 'Terminal'
Type in the following command.
sudo apt install -y ./nameofthefile.deb
apt is the package manager used by ubuntu-based linux distributions like elementary, the install keyword explains itself, I guess, and the -y flag skips the confirmation dialog, you are normally prompted with and approves the actions taken directly. . is a substitution of the current directory that you are in. apt needs this to understand, that you want to install a local file and not one from a repository.
That's pretty much everything sumed up, I guess. Makes it maybe a bit more understandable for you.
Answer: What other people have said is correct but I don't recommend you to install Skype on Linux.
Microsoft decided to stop updating their Skype app for Linux so it may stop working in the future and it may have security issues that aren't being patched. However, you can use Skype on the web from any computer and browser.
Answer: You can find an application called Eddy on the elementary OS AppCentre. When it's installed, you can either open the application and proceed as it instructs, or you can simply open Files, navigate to where the Skype installation file is located, click it and proceed with the installation.
You can also find Skype as a Snap and Flatpak application.
Answer: Skype is available for Linux from the Skype website. as a .deb package.
Grab the latest version of Skype and then open up a terminal window. Using the cd command, move the terminal window into the ~/Downloads directory:
cd ~/Downloads

Then, to install it:
sudo dpkg -i skypeforlinux-64.deb

Usually the process, in this case, will terminate with an error. To fix it:
sudo apt install -f

There is also, as mentioned above, a dedicated app for elementary that manages and installs .deb files.You can follow the direct link to the app Eddy - direct link
Hope that helped you.
Comment: You can use also `gdebi` to install a downloaded deb file and don't care about dependencies because it will try to install them or abort the installation if doesn't find them. Also you could use `flatpak` or `snap` to install the latest Skype

Skype Installation on Elementary OS


What exactly is the meaning of taking ownership in a project?

Question: What exactly is the meaning of taking ownership in a project? I have heard lot of managers say this. Since this is very commonly used and at the same time, not part of formal education, I want to know what exactly is this concept of Ownership(, its origin if possible) and why is it so much important from the manager's context, and how is it useful for the project/company
Comment: when I have heard it used it meant to take responsibility for the project if anything goes wrong. I've never heard it used in the context of 'You can take responsibility and the glory if everything works smoothly'
Comment: also to expect being able to make decisions instead of asking the previous owner.
Comment: Ownership means you take pride in what you deliver. Ownership means you care about the success of the project. You're not just clocking in and collecting a paycheck... you're taking responsibility and placing value in the quality of your work. Ownership means you give a damn.
Comment: If you are a project manager, aren't you supposed to take control of a project? Taking control can be seen as the same as ownership in a sense but this may be too simplistic.
Comment: In most of the time it means, "now if anything will go wrong with this project - you are to blame".
Comment: Usually when I hear it used it refers to the person who is the repository for knowledge regarding the project, as well as the go-to person for anyone who wants to know about the project.  He's the guy who decides what kind of meetings to have about the project and who should be invited.  he's the guy who is responsible to make sure everybody who contributes is doing their part.  He's also the guy who gets called out on the carpet if it is behind or over budget.
Comment: nobody has any references to share?
Answer: Taking ownership is not just doing a job, or working on a project; it means making it your mission to see it through.
Don't look to others to address issues; instead look for problems before they become obvious, and find and implement solutions.
If you can't fix it, then don't just toss the responsibility to somebody else; track down the person who can fix it, and make sure they address the issue.
It isn't a stated role on a team; in fact the project doesn't even have to be a team project.
Why does management like to see employees own the project/process/job; because that means that they care. They have moved beyond just showing up for work. They now want to see the project succeed.
In situations where nobody took ownership for a task; that task many times failed, or was completed late, or completed sloppily. Because nobody cared.
Comment: Honest question here: Shouldn't management be the ones to take ownership of projects? Isn't that their job? I'm not saying that others shouldn't care about the project succeeding, but it seems to me like the role of a manager is to be the one who takes ownership.
Comment: @DrydenLong I think that's the point; an individual contributor who takes ownership of some task or component is showing initiative and responsibility. These are indicators that you might be ready for a promotion, perhaps to management.
Comment: @DrydenLong on a high level yes, managers should be overseeing and coordinating a project, but it's important to realize that a manager is only going to have a high level view of what's going on, and that it's important for the people actually working on the project to be conscious of the end goals, and to raise issues to the manager, otherwise the manager won't be able to get in front of or fix the lower level issues.
Comment: @DrydenLong - Management's job is to take ownership of entire projects.  In doing so, they often (and should) delegate ownership of components of the projects to key individuals.  That level of ownership is probably what they're talking about.  You are to take individual responsibility to ensure that the component is complete, functional, delivered, and integrated, or to alert management of any impediments in accomplishing that.
Comment: @DrydenLong The project, in some cases, might be like the manager's baby. They want their employees to treat it like it's *their* baby too - to see it grow up and succeed and accomplish all its dreams and ambitions it can. Instead of sitting the baby in front of the TV and planning on what to do with the baby-sitting money.
Answer: People relate to projects in many roles. Ownership is one of them (A ROLE).
Other important roles include champion, sponsor, vendor, client and manager.
The owner is the person who's overall role is to see that the project is completed. Their role is to ensure that all the above roles are filled and working together in concert to complete the project. This is more a social or political role than an operational one.
Dual roles are often present and muddy the waters a bit. Inappropriately exercising roles can lead to poor performance of the project. A good PM will spot this and try to correct it - usually through the owner. This can lead to a head on clash e.g. the owner and sponsor refuses to pay a supplier for work completed and accepted according to contract, the PM objects.
If any of the roles are not being fulfilled, the owner needs to 'take ownership', be responsible and correct the problem. You are to act as a proxy for the true owner.
Likewise for tasks that go to make up a project, the project management team might assign a person or group to 'take ownership', i.e. to own the responsibility to see it through, as several of the responses suggest. Ownership entails taking care, responsibility and the attitude that the thing is your very own. The project manager's triangle (quality, cost and time) needs to be balanced in the best interest of the owner. You are to serve as their proxy.
See pmi.org for further details, Kerzner has a weighty book simply called "Project Management".
It is important to distinguish between ownership of the project and ownership of the artifact. These are entirely separate in the roles/responsibilities matrix.
On big projects roles are distinct and bounded.
On small projects, one person may be 'Big chief, cook and bottlewash'
Comment: I don't think when people tell you to take ownership, they're giving you the authority to take up a formal owner role. Instead, they mean "take initiative and don't wait for someone to tell you every little thing."
Comment: Is ownership not related to any role? Ex: if there is Manager and Project lead, who is the one who becomes the owner here? or is it not related to the designations of stakeholders in the project
Comment: @grk: a manager *should* be the owner, but often they are handling many different projects and are just trying to keep resources available.  A project lead *should* be an owner, but, again, they sometimes have multiple demands on their time.  Stakeholders are often just those whom the project impacts and they will want to make sure it's a positive impact to them.  The owner, as ChrisR explained, is going to be watching the project from start to finish to make sure that it is actually completed.
Answer: Disclaimer: This is my experience of only one office in 3 distinct countries and can't be generalized but this is exactly as it went.
I had to upgrade a database from a version X to another version Y in Thailand, China and Japan.
When a database is migrated, the application needs to be patched, new client version is installed and a lot of third party application relying on it, needs to be tested too.
In Thailand, no one took ownership of anything, they all looked to me for anything that wasn't working because it was my "fault". Needless to say, the migration to the new database version was long and tedious.
In china, the manager of the branch took ownership but not so much the employees. The migration went a little better because he was giving tasks to his team as problems were encountered and it really helped speed up the migration.
In Japan, each individual took ownership of their piece. They tested everything from end to end and I never had to ask if it was done. We encountered some problems, they would go work some more on it. No questions asked.
The migration went flawlessly. Everything worked on the first day after the migration.
This is the difference taking ownership makes.
Answer: I gave an invited keynote lecture at Software Methods and Tools 2000 in Wollongong with the state of project management being the topic, and you asked:

its origin if possible

I first started hearing it in the mid-1990s in Silicon Valley, which is also the time when "Project Manager" started to be a career of sorts, and distinct from "management." I then moved to the East Coast (of USA), and a few years later the phrase arrived at the bank where I worked (c. 2000), although I am not implying that I brought it with me. At that time I managed a group of project managers, thus clearly separating the two types of managerial activities, projects and people.

why is it so much important from the manager's context

The management vocabulary is as limited as it is trendy. For example, about this same time the euphemism resources became a soft, squishy substitute for people, as well as machines, buildings, and money. "How many resources are assigned to this project?" is probably a phrase you have heard.
The phrase "George owns this project" is currently (2016 / IT and Academic environment) equivalent to saying "George is the general contractor for the extension on my house." The owner of the project is sometimes identified as the Project Manager, which I think is inappropriate, and strips all of the meaning from the word owner.
The true owner of any project is the person who can negotiate the deal for the people and money to get the job done. Seldom can traditional PMs do this; they report the status, organize the work, search for the people or money, answer the complaints, and sometimes take the heat. These facts push the real ownership onto the customer -- only the customer can say "OK" to the allocation of more funds or schedule slips. In this context it appears that I own the project to put an extension on my house. I can sue the general contractor if things do not go well, but that is the extent of my recovery for bad execution ... as opposed to bad decisions on my part.

how is it useful for the project/company

I have my doubts that it is. Note that none of the things discussed here ...

owner
project manager
manager
resource

... are real. They are unlike customer and vendor which tell you who is paying, and who is being paid. Customers and vendors are real, and they will be around forever.
Answer: It's not the literal definition of owning something, but you behave as if you do. This is the difference between a waiter who brings you food that is obviously undesirable compared to one who gives it back to the kitchen, alleviates your concern that your food is taking too long and ultimately brings you a properly made dish.
The restaurant owner who truly promotes waiters taking ownership of their client's dining experience, isn't going to tell the waiter to only return food to the kitchen if the customer complains.
It helps if you know at least the general guidelines for what is the acceptable level of quality of the projects. There were times I've been a manager and there were some projects where I had no desire to get involved nor any knowledge on how to make it work, so I gave ownership to someone I thought would do a much better because the person was qualified and took pride in what they do.
For some people, they don't take as much pride in what they are doing if they are constantly told exactly what to do. Something as simple as tightening a nut on a bolt in an assembly line can lead to poor quality if they just "do what they're told" and fail to alter the task when they know the quality is suffering. Wouldn't you want every working who put your family's car together to act like their family would be riding in it? That's taking ownership.
Answer: I find that it is usually a positive way of stating a negative:  Your boss does not like NMP/NMF attitudes ("Not My Problem" / "Not My Fault") on the team.
NMP/NMF workers are poison to a team and are usually targeted for removal from the team if the manager can find a way to do so.
EDIT: Per @Chad's suggestion to explain WHY this is important.
The attitude of NPM/NMF individuals is focused on themselves.
"I didn't do that part of the system, so that's not my problem."
"That bug was introduced by "Jim" so he should fix it, not me - not my fault."
This attitude does not put the success of the objective first.
But, the goal of "owning" an objective is to put the objective first and that is important because management knows that requests and issues will be handled by the team and not forgotten or discarded:
"I didn't do that part of the system, but I do have some time, so I'll take a look at it and see if I can put your enhancement in, but, if I find that I cannot take care of it, I'll talk to someone who can."
"Yep, it looks like Jim created a bug, I'll take care of it right now."
OR as per an example in the comments:
"I'm sorry, I'm the database guy, if you want to enhance the gui, you'll have to talk to "Bob" - he's not here right now - so I'll let him know to contact you asap."
"I'm sorry, I'm the database guy, so I cannot fix the problem for you, but I can point you to someone that can."
In all of the "good" cases above, the focus of the team member is not explaining to management why they don't have to do the work.  Instead, the focus of the team member is on finding a way to make sure that the work gets done.
Comment: This appears to be more of a comment than an answer, or at best a partial answer.  Perhaps expanding on your explanation of why it is used would improve this.
Comment: @Chad, Good point.  I just put in an edit to your comment, but, it made the post much larger.
Comment: why are they poison for the team?
Comment: Because a team, by definition, are people that work *together* toward a common objective.  If an issue arises that needs addressed, and the team member replies with "not my problem" then they are not working toward the common objective.  In fact, on a *good* team, a manager should not need to even ASK to get something resolved - the manager should have confidence that the team will take care of it themselves.
Comment: Ok, "not my problem" may not be best attitude, but if those people do their job good, I see no reason for removal. And why is "not my fault" type of people a problem?
Comment: When a manager says that you "own" a project, he is saying that you are part of a team and, therefore, it *is* your job to *work as a team*.  If you do not do that, you are not valuable to that team.  The NMF is just a variant - if you "own" the project, then it *is* your fault because it is *shared* responsibility and the expectation is not finger pointing, but rather working toward the objective.
Comment: Sacking people just because they point fingers, or say that something is not their problem is very stupid. Dealing with people can be very difficult, and NMF can sometimes be the only solution. If a manager can not deal with it, then it is a bad manager, since the NMF people can actually point to a valid problem out of their scope.
Comment: Not sure I agree with this. Especially in my world (Programming), calling something as "Not my problem" generally infers you have gone to the wrong person to fix the problem. E.g. no point going to the database engineer if you have a problem with the GUI. Albeit I understand NMP/NMF need more of a followup (e.g. Its not my problem, but let me find you the person to handle this).
Comment: I think you are confusing the *general* idea behind teamwork with addressing specific under-performers on a team.  Addressing under-performers is done by going to the team lead, who can take the issue to management if the problem is consistent.  However, refusing to help the team because it is not your fault/problem *is* a reason for moving someone off of a team.  I hope that clarifies the difference.
Comment: @Sh4d0wsPlyr, your example *is* an example of teamwork - the database person says I cannot help you, because I have no skills in that area, but go to "Bob" who can help you.   That being said, on newer Agile teams, where everyone is cross-trained, this scenarios is less prevalent.
Answer: I regard this terminology as a red flag, much of the time, particularly when coming from management.
The basic idea is that they want you emotionally invested in making whatever it is happen, working whatever hours and schedules are needed, sacrificing other activities, etc.
If the project was your idea in the first place, and seems important to you, then you are quite likely already doing this, though perhaps not to the extent of totally destroying work-life balance. So if management is asking you to do this, then it's not a project you actually care about, and they know it. Perhaps you figure it's doomed to fail. Perhaps you figure the results would be useless or counterproductive. Perhaps you can easily think of ten more important things, and wish to put your effort there.
Now that's not always true. It's possible they are trying to communicate e.g. that they want you encouraging other people and orchestrating their efforts, not just doing your part of the task. (This might not work so well if you aren't a people person, and don't have authority, but for some people it works well.)
It's also possible they are trying to give you gentle guidance away from a "not my problem" attitude, as described in one of the other answers. It's usually true that the more senior the person, the more scope they take on - and one way to become senior is often to take on increasing scope. In technical fields, you probably don't have to wait to be assigned that scope - just follow any problems wherever they lead, rather than hastily passing them on to some other team, who might have better knowledge.


At what point does a convert become a Roman Catholic?

Question: If someone who is baptized outside of Roman Catholicism converts to Roman Catholicism, what specific act makes them a Roman Catholic? At what point does the convert say, "I am no longer Anglican (say), I am now Roman Catholic?" Since baptism is an irrevocable sign of joining the Church, what is the sign that someone has irrevocably become Roman Catholic? Is that sign a sacrament?
Comment: This is a good question, considering that Catholicism typically recognizes non-Catholic baptisms as *valid*, though not granting full communion with the Roman Catholic Church. Certainly, Anglican, Lutheran, and Greek Orthodox baptisms are considered real baptisms that should not be repeated upon conversion to Catholicism. The wannabe Catholic is a validly-baptised Christian seeking communion with the Pope's church, not a pagan seeking to become a Christian.
Answer: At what point does a convert become a Roman Catholic?
A non-Catholic Christian convert who has been validly baptized becomes a Catholic at the moment he makes a public profession of faith in the Catholic Church. This act of faith then allows you to receive the other Catholic sacraments including confirmation and the Eucharist.

The rite of reception of baptized Christians into the Communion of the Catholic Church states that "one who was born and baptized outside the visible communion of the Catholic Church is not required to make an abjuration of heresy [publicly] but simply a profession of faith.(1) Today, normally, an abjuration of heresy is made in the privacy of the confessional, though in the past it was often a public matter. After joining with the congregation in reciting the Nicene Creed, the person being received into the Catholic Church makes the following profession of faith:

I believe and profess all that the holy Catholic Church believes, teaches, and proclaims to be revealed by God.

As indicated in the Rite of Christian Initiation of Adults, adults joining the Catholic Church were formerly asked to abjure the previous faith to which they belonged ("Hebrew superstition", the Islamic "sect of the infidel", or "the heretical errors of the evil sect" from which they came). The profession of faith used was the Tridentine Profession of Faith. - Profession of faith

A Profession of Faith publicly made, usually before a Catholic priest, is sufficient to make you a Catholic, regardless if you receive the sacrament of confirmation and/or the Eucharist.
Prisoners on death row have made Professions of Faith into the Catholic Church, yet they were unable to receive the sacraments of confirmation or the Eucharist. They are definitely considered Catholic converts. I have stood beside a priest, who has received such a Profession of Faith. Immediately afterwards they make their first confession!
A first confession should be coordinated  in normal circumstances between the priest and the catechumen.
There are also special considerations for receiving Orthodox Christians into full communion with the Roman Catholic Church.
Normally, a baptized Orthodox Christian is to be received into the corresponding Eastern Rite of the Roman Catholic Church (Decree on the Catholic Eastern Churches 4). However, if the newly received person is married to a Catholic in a different Rite (e.g. Roman), he or she may either remain in the Eastern Rite or transfer to the Rite of the spouse. (canon 112.2)
Comment: In fact, the thief on the cross, sometimes called St. Dismas, is an example. He received no baptism or confirmation, but made both a confession of faith and of sin. Jesus granted him entry into the church and absolution.
Comment: The profession of faith, as worded, is something that an Anglican or Orthodox might very well say, the difference being in what was meant by the phrase "Catholic Church". Is there perhaps some  requirement, or intention, to mean Roman Catholic?
Answer: This answer is to complement @PeterTurner's answer (which highlights how the process started in the heart) and @KenGraham's answer (which highlights the beginnings of a public profession).  My answer emphasizes the culmination of the pulic profession: "a Catholic in good standing" / "practicing Catholic" that has to be maintained by remaining in communion with the Bishop of Rome.
As a Protestant who is doing research on pros and cons of converting, from the point of view of the Catholic church, you become a practicing Catholic once you celebrate your first communion which in a real way makes you "in communion" with the bishop of where you are residing, with the Pope, and by extension, with all Catholics who similarly declare such communion, whether living, in purgatory, or in heaven (communion of the saints).
Usually the first communion is preceded with:

having gone through RCIA which includes:

assessment of whether you need a conditional or a regular baptism (which in your case, coming from the Anglican church, you most likely do not need, if you can procure your certificate of baptism)

sacrament of reconciliation

on Easter, along with your RCIA cohort at your local parish, going through the profession of faith and the sacrament of confirmation, which preceded your first communion

From Wikipedia article on Conversion to Christianity — Catholicism  (emphasis mine):

The Catholic Church considers all forms of baptism with water, including full immersion, affusion, and aspersion, that are done in the name of the Trinity as valid.[29]
Protestants (Lutherans, Moravians, Anglicans, Presbyterians, Baptists, Assemblies of God, Methodists, etc.) who convert to Catholicism are usually not baptized, but instead are asked to make a simple profession of faith at Mass on an ordinary Sunday. Confirmation usually follows (though not always), and the convert proceeds to receive first communion.
Eastern Christians (Eastern Orthodox, Oriental Orthodox, and Assyrians), are only asked to make a simple profession of faith and then begin participation in the Eucharist without having to be confirmed due to the Catholic Church recognizing eastern Christian sacraments.[31] Eastern Christians who convert to the Catholic Church are automatically enrolled into the eastern rite corresponding to the Church they originated from regardless of what sui juris Church they entered the Catholic Church through.[32]
The amount of instruction before reception varies depending on how active the person has been in their Christian life, and how informed they are about the faith. Validly baptized persons coming from previous denominations do not have to be enrolled in RCIA because the Church does not consider them catechumens since their baptism has already made them Christians. Private instructions may be given by a priest, which can last from a few weeks to a few months at most. After instructions have ensued, the person may be asked to pick a sponsor for confirmation if the pastor decides to perform the sacrament.
Comment: @ash that's a very separate question.  It may be prohibited by the Episcopal Church, but it's definitely prohibited by the Catholic Church.  One can't believe what the Catholic Church believes about the Real Presence of Christ, Transubstantiation and the Priesthood. There's also a matter of missing Mass that you probably could go to - which is a mortal sin for Catholics; a Catholic who misses Mass for no good reason should not present themselves for communion without confessing at least that first.
Comment: @Ashpenaz Sounds like you are making your own rules.  Anyway, you might want to interact with KenGraham about this since he knows a lot more than I do.
Comment: "I believe and profess all that the holy Catholic Church believes, teaches, and proclaims to be revealed by God." Wouldn't every Christian say that? Each baptized Christian is part of the Catholic Church--at what specific point do you become Roman Catholic? Is the convert ever asked to profess any specifically Roman Catholic doctrines?
Comment: @Ashpenaz I think by making the profession in your quote **within the context of Confirmation in a Sunday mass** is sufficient.  Profession needs to be public.  As KenGraham wrote in his answer, there maybe extenuating circumstances where the only requirement is to make the profession before a Catholic priest.  My answer represents a typical path of an adult conversion.  But since I'm not a Catholic, you may want to consult a Catholic priest.
Comment: If I have been baptized as an Episcopalian, confirmed by a Roman Catholic bishop, and am currently taking communion at an Episcopal Church--and I repeat "I believe and profess all that the holy Catholic Church believes, teaches, and proclaims to be revealed by God" in front of the Roman Catholic congregation, why can't I take communion in the RC Church some weeks and in the Episcopal Church in other weeks? The RC Church claims that the Catholic Church is made up of all baptized believers. I believe in the faith shared by all baptized believers.
Comment: What I learn is consistent with what @PeterTurner said.  [Here's the Canon law basis](https://canonlawmadeeasy.com/2015/12/17/when-can-catholics-receive-communion-noncath-service/) why a Catholic cannot take communion in an Episcopal church.
Comment: What makes it confusing is that the Roman Catholic Church teaches that all that is required to take the Eucharist is a valid baptism. Full stop. There is no other official doctrinal requirement. Having to share Catholic beliefs about the Eucharist is a discipline and can be changed--and sometimes exceptions are made. "Some German bishops have said they will continue to advocate for — or just permit — intercommunion. An ecumenical "Eucharistic congress" scheduled to take place in Germany this month has said participants should act according to their own consciences." (The PIllar)
Comment: @Ashpenaz Oh I see.  Yes, the Germany Synodal Path is very controversial now.  But speaking in North American context, if you have unabsolved mortal sins (like missing mass for a long time, etc.) you're not supposed to take communion.
Comment: Taking communion in the Episcopal Church is going to mass. So I haven't missed mass. (Well, every now and then. . . but Mother Cathy absolves me after the confession of sin in the liturgy. Episcopal practice doesn't require private confession.)
Answer: There may be a point later on when one becomes a Catholic in Good Standing, but the point of conversion comes much earlier in on the process.  It's a discernment process which, for adults, I believe is similar to what priests go through:

It is impossible to be just to the Catholic Church. The moment men
cease to pull against it they feel a tug towards it. The moment they cease
to shout it down they begin to listen to it with pleasure. The moment
they try to be fair to it they begin to be fond of it. But when that affection
has passed a certain point it begins to take on the tragic and menacing
grandeur of a great love affair.

-G.K. Chesterton ("The Real Obstacles," The Catholic Church and Conversion)

That's the moment which a person "becomes" a convert. The Catholic Church has always taught that everyone is saved through her and everyone can be saved through her,

What is the meaning of the affirmation "Outside the Church there is no salvation"?

This means that all salvation comes from Christ, the Head, through the Church which is his body. Hence they cannot be saved who, knowing the Church as founded by Christ and necessary for salvation, would refuse to enter her or remain in her. At the same time, thanks to Christ and to his Church, those who through no fault of their own do not know the Gospel of Christ and his Church but sincerely seek God and, moved by grace, try to do his will as it is known through the dictates of conscience can attain eternal salvation.
CCCC 171

therefore everyone is more or less a member of the Church to begin with.  So membership isn't as important as the process that begins in the heart, which is conversion and makes its way into a formal process through Baptism (for the unbaptized convert), and the other sacraments of initiation (Eucharist and Confirmation).
Comment: @Ken, pre-supposing you're wondering why I bothered posting this. It's because someone like G.K. Chesterton was clearly a "Catholic Convert" long before his profession of faith. I re-read the question and there's only about 2% of the answer that this covers that yours doesn't.  the "Point" is certainly the profession of Faith at church, but the "point" isn't possible without the preceding process.


Having trouble with php and ajax search function

Question: I am still quite new to php/ajax/mysql. In anycase, I'm creating a search function which is returning properly the data I'm looking for.
In brief, I have a mysql database set up. A php website that has a search function. I'm now trying to add a link to a mysql database search rather than just showing the results.
In my search.php, the echo line is working fine but the $string .= is not returning anything. I'm just trying to get the same as the echo but with the link to the mysql php record. Am I missing something simple?
//echo $query;
$result = mysqli_query($link, $query);
$string = '';

if($result) {
    if(mysqli_affected_rows($link)!=0) {
        while($row = mysqli_fetch_array($result,MYSQLI_ASSOC)) {
            echo '
 '.$row['title'].' '.$row['post_ID'].'
';
            $string .= "
post_ID."'>".$row->title."
";
        }
    } else {
        echo 'No Results for :"'.$_GET['keyword'].'"';
    }

Answer: $row is an array, not an object, you have to use $row['title'] or mysqli_fetch_object() instead of mysqli_fetch_array().
In fact you're already using the correct syntax in your echo but not in $string.
Of course, $string needs to be outputed somewhere...


Standard Normal Distribution Problem

Question:
I am setting this problem up as P(-2 < (Mn) < 2) and then plugged in the formula for mean and standard deviation. I don't feel like I am headed in the correct direction. Could someone set me straight?
Answer: You want to solve for
$$P(|M_n| \ge 2) \le \frac1{100}$$
Note that mean of $M_n=0$,
Hence this reduces to
$$P(M_n \le -2) \le \frac1{200}$$
You might like to find the standard deviation of $M_n$ to proceed with the question.
Comment: Okay, I understand that. But how do you go from there to solve for n without know what the sum of the X's are?
Comment: Can you express the problem in the form of $P(Z \le \alpha_n) \le \frac1{200}$ where $\alpha_n$ depends on $n$ and $Z$ is the standard normal distribution?  from the inverse CDF value, try to figure out a bound for $\alpha_n$?

Standard Normal Distribution Problem


How does Kerberos know it's me?

Question: I log into my remote server as root (I know it's bad practice). I kinit as my principal. I do whatever I have to do, then exit from the remote server. Next time I ssh in, I klist, and I'm already authenticated! How is this possible? Is my principal tied to my ssh key? If I don't kdestroy, can other people logging onto the server as root act as my user?
Comment: kerberos tickets, yes and yes+-.
Answer: You probably want to read the documentation. https://web.mit.edu/kerberos/krb5-1.12/doc/user/user_commands/kinit.html
The short answer is that your authentication is cached in the form of a ticket and this cache is kept for the lifetime of the ticket or until kdestroy.
Kerberos can be tied to remote credentials but in this case it doesn't sound like it is. Its the fact that the user, root on the remote host in this case has cached tickets.

How does Kerberos know it's me?


Launcher Activity theme visible on closing another activity

Question: I have a Splash Screen Activity (as a launcher) with a theme. The theme has a red background and an image.
On opening the app, SplashScreenActivity shows its theme followed by rendering the XML UI (and performs some API calls) and then opens Home Page. Also while opening Home Page it finishes the SplashScreenActivity.
Now if I close an ActivityX and redirect to ActivityY then the theme that was set on SplashScreenActivity shows up. Why is this so? This theme was set on SplashScreenActivity & not on ActivityX or ActivityY.
Any solution for this?
Answer: Do apply theme in every activity, just reuse the theme if you want as:
<code>android:theme="@style/MyTheme"
</code>


New to ubuntu can not find vlc on ubuntu search or install need some help here please

Question: I'm new to Ubuntu and it's an awesome system but i can't find vlc on the ubunut search or figure out how to install any software like flash player etc can anyone help out please will be greatly appreciated
Comment: See this question which teaches you how to install software: http://askubuntu.com/q/66447/176889
Comment: sudo apt-get install vlc
Answer: Install the latest version of vlc in Ubuntu via PPA
<code>sudo add-apt-repository ppa:videolan/stable-daily
sudo apt-get update
sudo apt-get install vlc
</code>
Through the Ubuntu Software Center, you can download and install any software in Ubuntu.
Download Ubuntu software center from here.
Comment: Why in the world would you need to download the Ubuntu Software Center **on Ubuntu**?!?
Comment: If you use a derivative that hasn't Software Center installed by default, you may want to install it. But that was not stated in the question. Installing a PPA was also not part of the question and isn't necessary.
Comment: While some Ubuntu derivatives (including some official derivatives) don't include the Software Center by default, there's nothing on `software-center`'s [Launchpad source package page](https://launchpad.net/software-center) that provides a reasonable way for most people to install it. A properly functioning, Internet-connected Ubuntu system without the Software Center can be outfitted with the Software Center simply by running `sudo apt-get update` followed by `sudo apt-get install software-center`. (For Lubuntu, users may prefer `lubuntu-software-center`, which may already be installed.)
Answer: press window or super button.type ubuntu software centre and open it..its like a play store you have in android.search for software(like vlc or xbmc) u want and install it...
Answer: Usage of Software Center should be self-explanatory, but you can also use the web interface:

VLC in Software Center
Adobe Flash plugin in Software Center
Ubuntu restricted extras in Software Center


How do I get unique users signed up? [Canada or US]

Question: Clients can win prizes on service and our team has to check their identity before giving prizes to them. Is there any way to collect photo ID while people signing up? Is it legal? Or there is some other way to check that it is not the same person signed up twice?
Comment: You can ask for whatever you want, including DNA test. How many people would agree to this is another question. Fake IDs are not uncommon among underage drinkers either.
Comment: Hi welcome. Sorry but this is likely to get closed for being off topic and too broad. If you want legal advice then the legal stack exchange forum may be better
Answer: "Welcome to the Internet, where no one knows that you're a dog."
You cannot rely on any info supplied by a user to be globally unique in identifying themselves.
Any process you can devise can be manipulated. Even if you collected passport page photos, you would still not be able to confirm that every winner was unique. For example, my wife has a passport from one country with her maiden name, and a passport from another country with her married name. There are also online fake ID generators for just about any country you would like.
Instead, you have to design the process:

to be more expensive to manipulate the process than the prize is worth (e.g. have a proof of purchase tied to a specific account)
to be tied to a long-term proof of relationship or activity (certain amount of reputation points in your system, depth or complexity of history on a social network)

If you cannot do these things, or if they are contrary to your goals for having a prize, then you need to not care if someone was able to win multiple times, or gain enough benefit from someone winning, even if someone wins multiple times.
For example, in order to win (or claim their prize), they have to advertise you on their social network. Even if someone won 100 times, that would mean that they would have to have 100 accounts and have all of them advertising for you. That's not such a bad thing.


What does "Works" of Ontario Works mean?

Question: I live in the province of Ontario in Canada. The ministry of community and social services here have a type of welfare called Ontario Works, and this provides financial and employment assistance to individuals in need. And I'm wondering, what does Works of Ontario Works mean? I've looked up the term in the dictionaries, but couldn't find anything relevant to the context.
Comment: It's a pun on *Works*, as *Public Works*, and on *works* as *earning a living*.
Answer: It's the third person singular present of the verb "to work." There's nothing deeper than that; this is a baroque rat's idea of a fun, modern name for the programme.
Comment: btw @James, is baroque rat a deliberate pun?
Comment: To be eligible for the program you must be able to work, agree to "take part in activities that will help you find a job" and so on. This is in contrast to someone who cannot work (because they are disabled perhaps). The name of the program describes their hope for what it will achieve - to transition people from needing financial aid to working. (As for whether it meets that goal, or whether being on it is as fun and upbeat as the name, that's a different story.)
Comment: LOL yes, although I expect someone to correct it. (I can't claim credit for it - I read it in a sci-fi story during the eighties - whose name I forgot long ago.) Or maybe I should say - you live here, you tell me?
Answer: Public works is a common phrase for such things as building new hospitals, and I imagine some bureaucrat could not resist the play on words between this (which historically involved work for local unemployed labourers, though less so nowadays), and a slogan about 'getting Ontario back to work'. As a bonus, it implies that the Ontario administration is working well. Clever, eh? (at least by political standards.)


Golden image updates in qemu

Question: Consider that there are 100 windows virtual machines coming from a single base image and each vm is added to domain along with minor other machine specific settings which can be done by a script.
After a week say I want to update all vms with a security patch. There are two methods to do this:

Destroy all vms, update base image, create all vms again.
Issue: This requires all the vms to be destroyed, create disk again, define vm, then run required scripts which take care of vm specific configuration with multiple reboot cycles as required.
Manually update all vms and apply the security patch.
Issue: Just cannot scale. May be okay for a set of 5-10 vms not 100s.

I am curious how do other people/softwares do it? Is there a better approach or can I improve my 1st method?
Comment: Why would that "cannot scale"?
Answer: You can improve on option 1 by AD integrating the windows machines and having changes pushed out through the tools it provides e.g. SCCM

Golden image updates in qemu


Distributed database implementation in sql server

Question: Currently, We have central Database at Head Office and users from sub offices ,scattered around the country, connect to central database. Now we want to distribute the database in disconnected mode at each Sub office level and we want data to be synchronized at the day end at the central Database from all others Databases. We also want transfer of data to all Databases from central Database. Please refer me the tutorial or way to implement this scenario in SQL Server. Thanks in Advance.
Answer: This is pretty much a textbook example for Merge Replication.  Here is the Product documentation describing the scenario, and how to implement it.
Answer: if you need use sql server for distributed plan, I know about 2 scenario:

you can use Big Data Clusters for store big data in HDFS managed by SQL Server, read about in reference this scenario :

Use Service Broker for Asynchronies 2 or more SQL Server in distribute plans. you can read about in below link:

Developers can easily create sophisticated applications that use the Database Engine components to communicate between disparate databases, and build distributed and reliable applications.

In other scenario you can use Always ON, Replication , Mirror . but i guess you need use Service Broker.


What does Marlin's G30 code do?

Question: I'm using Marlin 1.1.0RC8 to control an MPCNC, using a RAMPS1.4. We've just added a touch-plate to do Z-probing, which works nicely for a single probe (I just want calibrated height for variant bit-lengths, not bed-leveling, but I think it amounts to the same thing). I've set it up in Marlin as FIX_MOUNTED_PROBE, which seems closest.
I can make it do a G38.2 Z-50, G92 Z12.6 (which sets Z to the height of the touch-plate, 12.6mm), which is ok to be going on with, but it seems I'm having to hard-code the Z offset, which I'm sure should really be set by eg Z_PROBE_OFFSET_FROM_EXTRUDER or M851.
My feeling was that I should be able to invoke a G-code G30, and it would do a nice fast-slow double tap, do the equivalent of a G92 Z+zzz to set that height and then withdraw to a safe height. And after a bit of config, it does exactly that...
... except it doesn't do anything with the height that it measured! Seems odd. The G30 code seems to be an elaborate way to move the head up by the clearance amount, via a touch-plate (with the added excitement of being able to crash the bed if anything goes wrong)! What's the point?
Have I misunderstood what G30 is meant to do? I've read the docs here, and traced through Marlin_main.cpp and there really is no "outcome". Unless I've missed something?
Comment: I note that I don't have end-stops on Z, so I can't home/`G28` that axis. I can't see that it makes any difference, but I'll go through the code later and see if that's what's wrong.
Answer: I believe G30 is a carry-over from CNC (G-code originated for CNC not printers)
I believe it is for going to a secondary reference (home) position and includes an optional by-way-of address that can be included in the command.
Looking at Marlin 1.1.0-1 (latest release), it seems to do what you said:

Move to the requested position (if selected in command, else N/C)
Deploy probe
Go home
Stowe probe
Report the requested position and probed Z position
Report the current position (home?)

It appears that for Marlin, there is only one reference address (home); so, it would seem a G30 would be the same as a G28 (go to primary reference); but, not so.
It looks like G28 is a home of a different color.  It looks like it homes the axis one-at-a-time and does not support a by-way-of location.  Note that you can select which axis to home by adding the letters 'X' 'Y' and/or 'Z' to the command.
I am not sure what benefit this command has for a 3D Printer other than allowing you to alter the printer's path to home.
Note: Unfortunately I do not have Marlin code up and running on my printer now so I cannot confirm what I am seeing in the code.
Comment: Mark, I haven't forgotten you've written this! Your contrasting of G30 with G28 surprised me so much - I hadn't thought of G30 as a HOME variant - that it made me re-evaluate all my assumptions, and I'm waiting for a rainy weekend to sit down and properly update all my preconceptions! In particular, G30 does "report" the probe position (back to the monitoring app); I was expecting it to store it internally as a reference... will investigate further.
Answer: I've recently had a need to use Z-probe touch
plate on my MPCNC + Ramps 1.4 + Marlin 1.1.5 setup.
Thought I'd share what ended up working for me.
In Marlin Configuration.h, I made the changes to enable Z-probe:
#define USE_ZMIN_PLUG
#define Z_MIN_ENDSTOP_INVERTING     true
#define Z_MIN_PROBE_ENDSTOP_INVERTING   true
#define FIX_MOUNTED_PROBE
#define PROBE_DOUBLE_TOUCH
#define Z_MIN_POS -100

However, the following might be the key to your issue.
G30 did not do anything for me as well, until I changed
these values to 0.  The G30 now lowers Z until the Z probe
is triggered. I needed to send a G92 to set the new Z value.
Works like a champ!
#define X_PROBE_OFFSET_FROM_EXTRUDER 0
#define Y_PROBE_OFFSET_FROM_EXTRUDER 0

In case you're interested, in ultralcd.cpp under
lcd_prepare_menu(), I added the a menu item to perform
the probe.  This way I don't need a computer to setup
the machine and launch a gcode file from the sd card.
  #if HAS_BED_PROBE
        MENU_ITEM(gcode, MSG_PROBE_Z, PSTR("G30\nG92 Z19.05"));
  #endif

Hope this is helpful for you, even after a couple years late.
Comment: It is unclear which parameters are set to zero. If you mean the **probe offset values**, that is **not a good idea**. Note that this question deals with Marlin 1.1.0, in between 1.1.3 and 1.1.4, the `G30` command has undergone a change.

What does Marlin's G30 code do?


Can you change time zones on calendars?

Question: I have a site that contains nine calendars for events happening in various time zones. Is it possible to set the time zone for each calendar? How can I tackle this problem?
Comment: This setting is available at site level and not with Calendar.
Comment: Seems like the only out-of-the-box solution is to make a sub site for each calendar then.
Answer: You can change regional settings on a site-by-site basis and this is not available at list(Calendar) level. A site collection can consist of a top-level site and one or more subsites. The regional settings for the top-level site of a site collection are automatically set based on the default language of the site collection. When you create a subsite, the subsite inherits the regional settings of the parent site. If you are a site owner, then you can specify different regional settings.
To change the regional settings for a SharePoint site

Open the site on which you want to change the regional settings.
On the Site Actions menu, choose Site Settings.
On the Site Settings page, under Site Administration, choose Regional settings.
On the Regional Settings page, select the settings that you want for this site, and then choose the OK button.

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What are these notations in class diagrams?

Question: I know basics of UML and java's OO interpretations using class diagrams. But after looking at this class, I felt weird. What are the member variables and what do they represent in the actual language? I guessed the first one which is a boolean type (If I'm right), but what are the other member variables especially those which take some arguments? Any help would be appreciated. Thanks
Comment: It looks like those are just "values we would expect" each variable to hold used as an example. So power is a boolean, speed is an unsigned integer, maxspeed could be anything probably a float, type and mode are probably enums.
Comment: Thanks, but speed seems to take any postive integer >=0, therefore there is no upper limit for it..
Answer: This diagram you include is not strict uml. From what i can understand it means the following:

You have a class called ElectricFan
Your class has the following member variables (power, speed, maxSpeed, type, etc). In parenthesis i guess that the author has included the values applicable to each member variable.
Also, the author includes the methods that are applicable in this class (i.e. switchOnOff(), changeSpeed(), etc).

An important piece of information that the author doesn't include is the visibility and type of the member variables as well method arguments and return types.
If you are interested in learning more about UML you could start by reading Marting Fowler's UML distilled (http://www.amazon.com/UML-Distilled-Standard-Modeling-Language/dp/0321193687).
Answer: The values given in brackets are not arguments, instead they seem like enumerator types.
As far as the speed parameter is concerned it looks like an unsigned int.