How to make items unbreakable?
Make tools indestructible in Minecraft
Checking for null before event dispatching... thread safe? Is there any way to fix the wavy lines that appear when photographing a striped dress?   It's not just in viewing online: when it was printed at wallet size, the wavy lines showed up. I'm using Dataloader to Upsert a Child Account to Parent Account using an external ID.  When the Upsert is complete, the Child overwrites the parent, it's not not connecting the Child Account to the Parent Account.  ((See Answer Below)) Proving a combinatorial identity without double counting Consider the following problem:  We have a collection of m white and n black balls. We pick k balls (k ≤ m+n) without replacement. What is the expected number of white balls in the sample?  Counting method 1: The ratio of white balls in the collection is m/(m+n). If we repeatedly sample the collection, we expect that on average, our sample has the same ratio. Therefore, the expected number of white balls in a sample of size k is km/(m+n). As a side note, I think the above argument somehow depends on the unbiasedness of  the mean estimator. Am I right?  Counting method 2: We directly compute the expected number of white balls in the sample: $$ \frac{\sum_{i=0}^{k} i\binom{m}{i}\binom{n}{k-i}}{\binom{m+n}{k}} \enspace.$$  So, we reach at the identity: $$ \sum_{i=0}^{k} i\binom{m}{i}\binom{n}{k-i} = \frac{km}{m+n}\binom{m+n}{k} \enspace.$$  How to prove the above result without double counting? It seems to be provable using  as well as $i\binom{m}{i} = m\binom{m-1}{i-1}$. But is there a simpler approach (which does not depend on extra identities such as Vandermonde's)? GSC: How to move a site from a domain to sub domain, sub folder or new domain with a sub folder? Where can I buy an Ubuntu Phone? I need to buy an Ubuntu phone, where can I buy it? It is unavailable everywhere. "'Hello', says he. 'Hello', says I" — is this correct? I'm reading a novel in which once in a while a character says something like "I are", "He do", and similar stuff. I understand the author is just reproducing the way people talk on the streets.  However I've found a piece of text of which I'm not sure if it's proper English. One of the characters, who almost always speaks proper English, is reproducing a conversation that happened many years ago using the present tense in the following manner:     I was with this guy and "Hi", says he, "how are you", says I...   and so on.  My question is if the "says I" is proper English (a special case in which "I" is treated as a third person because we are relating in present tense something that happened in the past) or it's just kind of slang.  I was also a bit surprised by how the usual order is switched ("says he" instead of "he says") but to me it's secondary to the "says I" issue. How can we change root password? This is trigonometry from double angles and compound angles. Thus far I've simplified it up to this point. $$2 \sin^2θ – 3\sinθ +1 = 0$$  I'm trying to factorize this to solve for General Solution. I tried taking out a common but that +1 is giving me a problem. I used the quadratic equation to get 1 and 0.5 as an answer, but i don't know how to write it in terms of 2sin(squared)θ and -3sinθ.  Any help will be appreciated. According to , the only restriction on self-deleting an answer is that you can't delete an answer that's been accepted.  But I've also heard of users getting in trouble for deleting (non-accepted) answers, and there's the CC-SA license to consider, so -- quite aside from what is technically possible -- my question is when it's permitted to delete your own answer.  Some cases to consider:   You now believe the answer is incorrect. Your answer is correct, but another answer covers the same territory better. You aren't satisfied with the quality/rigor of your answer, e.g. it's speculative and you didn't back it up (on a site that expects that). Something in the answer embarrasses you and you'd rather just make it go away. Your answer wasn't well-received by the community (whether that's "meh" or "make the rep bleeding stop please"). (I'm sure there are others; this isn't meant to be an exhaustive list.)   Does voting matter, either in absolute terms or in comparison to other answers?  For example, maybe it's ok to delete a lower-voted one but not the top-voted answer, or one with score > N??  There is a badge, Disciplined, for deleting your own post of score 3 or higher.  This tells me that it's sometimes ok to delete upvoted answers.  But I'm not sure how much policy we can infer from badges.  Could we have some clarification please? Bibliographies from multiple .bib files I would like to use multiple .bib files for my article, such as file1.bib, file2.bib. However, I would like my references not to be separated (such as &quot;Primary sources&quot;, &quot;Secondary sources&quot;, etc.). These bibliographies just need to be merged into one. One way to do this is to copy-paste these .bib files into one .bib file, and this would solve the problem. However, I would like to keep it split into several .bib files, by topic (file1.bib contains articles on topic1, file2.bib contains articles on topic2, and so on). I tried to do \bibliographystyle{alpha}  \bibliography{file1} \bibliography{file2}  but this just gives me the same bibliography twice! In Unity, are there any pre-defined shortcuts, e.g. to open the dash or unhide the launcher? How many Shutter Clicks on a New Camera considered normal? How many Shutter Clicks on a New Camera considered normal?    I purchased a quotes new Nikon D750 and checked the shutter count and it has 264 Shutter Clik count on it.    Is that suspect of a returned purchase or used camera? Imported 3D scan displays texture in editor, but renders without texture I am new to blender and I have a 3D scan of a stone tablet (which I am unfortunately not able to share, so I will try to be as detailed as possible) which was imported as OBJ and MTL files.  The editor displays the texture and mesh perfectly, but when I render the scene (pressing F12) the texture is not there.  I am trying to use blender to reduce the file size of the tablet for use in a three.js visualizer for a website.  I have tried exporting the file as a JSON file (as well as several other file formats to the same effect) for use in my three.js webapp and thought it was an issue with three.js, but after seeing that blender did not render the tablet with the texture I now believe it is an issue with my blender configuration. I am unable to find within blender or online any way to check what current resources I have displayed and what options I have with them.  I have not applied a mesh or texture to the object, but when I do so it renders with the generated texture applied in the default pink.  I am confused as to where the disconnect is between the editor and the renderer. I am still figuring out what is important and where to find all the relevant information, so any help on that regard would be very much appreciated.  Here is what blender looks like for me with the sensitive parts censored (can't be too careful these days):   I have looked at this question:  And there is no material overwriting the texture - I have not assigned a material to the tablet at all. EDIT: In regards to the duplicate answer, I looked at that one as well and the issue I have is that it doesn't have an actual texture file that I can just put on it.  The OBJ MTL files come with their own file that can't be applied directly to the model.  Blender read the OBJ MTL files and recreated the object inside blender algorithmically - and now I need to know how to get blender to tell me where that texture is and how I can get it to show up in the render.  The texture is not on my hard drive, but entirely within blender which is the issue I am having. What longest time ever was achieved at holding light in a closed volume? For what longest possible time it was possible to hold light in a closed volume with mirrored walls?   I would be most interested for results with empty volume but results with solid-state volume may be also interesting. Show that $e^{-\beta} = \frac{1}{\sqrt{\pi}} \int_{0}^{\infty} \frac{e^{-u}}{\sqrt{u}} e^{-\beta^2 / 4u} du$. Show that $e^{-\beta} = \frac{1}{\sqrt{\pi}} \int_{0}^{\infty} \frac{e^{-u}}{\sqrt{u}} e^{-\beta^2 / 4u} du$.  I'm not really sure of how I should proceed to show this, and it's pretty un-intuitive as well.  I've managed to manipulate the RHS into  $$\frac{e^{4\beta}}{\sqrt{\pi}} \int_0^\infty \frac{1}{\sqrt{u}} e^{-(\beta+2u)^2/4u} du$$ which now vaguely resembles a Gaussian. However, substituting $v = \beta + 2u$ in in order to to get something like $e^{-x^2}$ doesn't particularly help. I got $$ \frac{e^{4\beta}}{\sqrt{2\pi}} \int_0^\infty \frac{1}{\sqrt{v - \beta}} e^{-v^2/2(v-\beta)} dv. $$  I'm really unsure of how I should proceed; any help would be appreciated. Non-finite clause complementation of complex transitive verbs This question has been bothering me for a while. It came up when I was reading Chapter 16 of "A Comprehensive Grammar of the English Language."   How to explain the grammatical structure of the following four sentences?    "We knew him to be a spy." "I saw her leave the room." "I heard someone shouting." "I got the watch repaired."    What category do the four non-finite clauses in boldface fall into? They do not seem to fall into any of relative, nominal, comparative and adverbial clauses. Compactness of $(M, d)$ in terms of continuous functions $f:M\to \mathbb R$ Suppose $(M,d)$ a metric space. I want to show that      If every continuous real-valued function on $M$ attains a maximum, then $(M, d)$ is compact.   I was trying to do this by assuming $M$ non-compact and showing explicitly a function which does not attain a maximum. If $M$ is not bounded it's enough to take the distance from a fixed point as we can always find a sequence which "exits" every compact and pushes the distance at infinity. But what if $M$ is bounded? sudo on Windows 10 Linux subsystem cannot resolve local machine name I installed Windows 10 Anniversary update and the Linux subsystem. When running anything with sudo it takes ages and then I get this error message:     sudo: unable to resolve host MYMACHINE   How to get rid of this and make sudo fast? If I take a sponge and place it in a shallow dish of water (i.e. water level is lower than height of sponge), it absorbs water until the sponge is wet, including a portion of the sponge above the water level. In other words, it seems the sponge pulls some water from the bath up into itself, doing work, and the water gains some gravitational potential energy.  Where does the energy required to do this work come from? My suspicion is that the answer involves physical and/or chemical bonds between the water and the sponge, or possibly the change in the surface area to volume ratio of the water.