FileUri shows null after camera capture even after onsaveInstanceState and onRestoreInstanceState
What is a NullPointerException, and how do I fix it?
Are there any research careers except professorship for a person holding PhD in pure mathematics? Let $F$ be a field and $x\in F$. If $x=-x$ and $1\neq -1$, then $$0=\frac{x+x}{1+1}=\frac{1+1}{1+1}x=x.$$ This means that the statement in the title is true if and only if $1\neq -1$. But how do we know that $1\neq -1$ for an arbitary field? Transformer VA Ratings, Power factor, and Pulsed current What exactly goes into a transformer's VA rating? At a fundamental level it seems that there has to be a limit to what the VA rating can represent.  For example if I draw 2 Amps-RMS from the secondary of a 30VA rated transformer at 15 Vrms this makes sense as the maximum Complex Power I can draw. Still, at a power factor of 1 my maximum current in the transformer would be sqrt(2) * 2 Amps.   But what if my power factor is abysmally low (ie in a DC rectifier) due to harmonic distortion and while I still draw 2A-RMS I have brief current spikes of 15 Amps? Surely the transformer's magnetics couldn't handle these spikes as I'd expect the core would saturate.  My question is what is the practical limit for VA ratings of transformers? Would brief current spikes that reduce to only 2A-RMS in this case be fine? Obviously the secondary/primary copper losses play a part in the rating but how do the magnetics factor in?  I ask this because I am designing a simple bench power supply using a 125VA transformer with a 24Vrms secondary and am trying to figure out how much power I can draw before the current spikes into the inductor are too much for the transformer. I also don't want to have to resort to active PFC as I don't want to risk messing up any HVAC PCB design.  Thank you Sorry, I'm still a newbie to blender, but why are some edges visible only in edit mode, but not in wireframe view? is it a bug or am I missing something here?  edit mode: Edges visible. Object mode, wireframe view: Pooff, they're gone. what can i do to fix this? / thanks How can I make ffmpeg be quieter/less verbose? By default ffmpeg sends a whole lot of messages to stderr: when built, how it was built, codecs, etc, etc, etc.  How can I make it quieter?  I've tried -v 0 (and -v 10 since the documentation just coyly says Set the logging verbosity level. with no indication of what the range of inputs is) -- still not quiet.  I've tried -loglevel quiet -- still not quiet.  I should mention, I'm looking for "quieter," not "no output ever".  If there's an error I want to see it, but I don't need to hear about ffmpeg's configuration every. single. time. I know you can create a rounded-corner rectangle; but, how do you create a triangle with rounded corners in Photoshop?  I am actually interested in making it from scratch, not basing it on a custom shape that is available in Photoshop. Thanks. I am working on a BLDC sensorless motor. I need to detect BEMF Zero-cross event. My Motor is working on 24 Volt power.  Now I need to detect the back E.M.F. As refered in .  My MCU is working on 5V. And ADC range is 0 to 5V. I need to convert the BEMF feedback signal to ADC channed in this.  As we know voltage divider rule says:   In Figure I :-- Now signal (U) which I need to feed is applied at the middle of the two resistors R1 &amp; R7. So what is the value of voltage VU ?   In Figure II :-- Sum of U,V,W  is applied at the middle of the two resistors R11 &amp; R15. So what is the value of voltage VN ?  Also, what are the roles of capacitors C1 &amp; C4?  Please can someone explain the MATH behind this ? How do you remove duplicates from a list whilst preserving order? com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure What license to use while putting papers on the Arxiv? I am new to this and not sure what to make of all the options available. I am interested in putting a machine-learning-related preprint, which will potentially be submitted to places like NIPS/ICLR/ICML in the future.   arXiv.org perpetual, non-exclusive license to distribute this article (Minimal rights required by arXiv.org)  Creative Commons Attribution license (CC BY 4.0)  Creative Commons Attribution-ShareAlike license (CC BY-SA 4.0)  Creative Commons Attribution-Noncommercial-ShareAlike license (CC BY-NC-SA 4.0)  Creative Commons Public Domain Declaration (CC0 1.0) Using uniform coloring in MatrixPlot Why shouldn't I care what model/make/year my bicycle is? We often get questions on bicycles.stackexchange about identifying a bicycles manufacturer, model, make, and year.  Often these questions are downvoted or closed -- usually with a comment attached to them that it's not necessary to know the exact model/make/year of a bicycle if you want to fix, repair, or ride your bike. Why should owners not care about the model/make/year of their bicycle? Especially when it comes to less expensive bikes (aka BSOs) and BMX bicycles? This is intended as a canonical question that we can point closed questions to. Also see      (generally not helpful for identifying a brand/model) Best practice for Rails App to run a long task in the background? I have a Rails application that unfortunately after a request to a controller, has to do some crunching that takes awhile.  What are the best practices in Rails for providing feedback or progress on a long running task or request?  These controller methods usually last 60+ seconds.    I'm not concerned with the client side... I was planning on having an Ajax request every second or so and displaying a progress indicator.  I'm just not sure on the Rails best practice, do I create an additional controller?  Is there something clever I can do?  I want answers to focus on the server side using Rails only.  Thanks in advance for your help.  Edit:  If it matters, the http request are for PDFs.  I then have Rails in conjunction with Ruport generate these PDFs.  The problem is, these PDFs are very large and contain a lot of data.  Does it still make sense to use a background task?  Let's assume an average PDF takes about one minute to two minutes, will this make my Rails application unresponsive to any other server request during this time?  Edit 2:  Ok, after further investigation, it seems my Rails application is indeed unresponsive to any other HTTP requests after a request comes in for a large PDF.  So, I guess the question now becomes: What is the best threading/background mechanism to use?  It must be stable and maintained.  I'm very surprised Rails doesn't have something like this built in.  Edit 3:  I have read this page: .  I would love to read about various experiences with these tools.  Edit 4:  I'm using Passenger Phusion "modrails", if it matters.  Edit 5:  I'm using Windows Vista 64 bit for my development machine; however, my production machine is Ubuntu 8.04 LTS.  Should I consider switching to Linux for my development machine?  Will the solutions presented work on both? Player A taps  targeting Player B; its "deals 1 damage to target player" ability is placed on the stack.  Player B gets priority and responds with , targeting Goblin Fireslinger.  Both players pass priority. Snap resolves, and Goblin Fireslinger is returned to its owner's hand.  Does Player B still take 1 damage from Goblin Fireslinger's activated ability?  I know that if the creature had been killed/sent to the graveyard, the ability would still resolve, but I was told recently that because a player's hand is a private zone it couldn't. If anyone could confirm or deny this for me, it would be most appreciated. Fisher Information of a function of a parameter Is there any analytics information that moderators can access for individual questions? Can the Hubble constant be measured locally? The Hubble constant, which roughly gauges the extent to which space is being stretched, can be determined from astronomical measurements of galactic velocities (via redshifts) and positions (via standard candles) relative to us. Recently a value of 67.80 ± 0.77 (km/s)/Mpc was published. On the scale of 1 A.U. the value is small, but not infinitesimal by any means (I did the calculation a few months ago, and I think it came out to about 10 meters / year / A.U.). So, can you conceive of a measurement of the Hubble constant that does not rely on any extra-galactic observations?  I ask because, whatever the nature of the expansion described by the Hubble constant, it seems to be completely absent from sub-galactic scales. It is as though the energy of gravitational binding (planets), or for that matter electromagnetic binding (atoms) makes matter completely immune from the expansion of space. The basis for this claim is that if space were also pulling atoms apart, I would naively assume we should be able to measure this effect through modern spectroscopy. Given that we are told the majority of the universe is dark energy, responsible for accelerating the expansion, I wonder, how does this expansion manifest itself locally?   Any thoughts would be appreciated. crisscross, dillydally, riffraff, etc Quick way to remove solidify thickness I have made the mesh and added solidify modifier and applied. But later i thought to increase the thickness. So now i want to remove thickness so that i can added the solidify modifier again. I want to know is there any quick remove thicknes. When i select the edge then ctrl+ the selection goes downward not to single face. So i want to know a quick way to decrease thickness. Any suggestion or help. Changing TTY keyboard layout on a server? I use 12.04 Server in command line mode (no X installed), and I would like to change the keyboard layout. How can I do this?