Technical question on stats in ff7

Question: I have the following question on stats in final fantasy 7 (=ff7).
I have Cloud on lvl 99 with 255 strength (ignoring armor and weapons and materia). Now I noticed the following:
I can still give cloud power sources (which increase strength) but this only works to a certain point and then it is not possible anymore. One can give around 100 more power sources and then it is not possible anymore. Is there a precise explanation why it is not possible anymore?
I dont know but my own explanation would be that the real max of stats in ff7 is 355 and not 255 and one can go up to 355 despite that the displays max is 255. (for example ruby has 355 defense)
Answer:
Marking this as community wiki as it's converting a comment to an answer

According to a comment from Frank, the answer is:

Basically, implementation counts how many sources used, and caps it at 255, and adds to base value, which is capped at 99. You can use 100 more sources because not everyone's stats will hit 99 by level 99.

Source
Comment: 255 is a common maximum value for programmers to use since it the max value of a 8 bit integer.

Technical question on stats in ff7


After how many days can concrete framework be removed?

Question: After how many days can concrete framework be removed? Do admixture chemicals like superplasticizer or accelerating admixtures allow early removal of concrete framework?
Comment: When the concrete is sufficiently cured. You will know if you remove too early :)
Answer: You pour test cylinders with every batch of mix used. These are then tested in a compression tester. When the test cylinders are up to strength, you can remove the form work. An engineer needs to determine what strength is necessary. Yes, admixtures, temperature, water content, mix formula, and aggregate selection effect the strength-gain curve.

There are also real-time Bluetooth systems with imbedded sensors so you can match temperatures.
Answer: The American Concrete Institute (ACI) is a source of standards in the US construction industry.
There is a guide which has been posted on the web: ACI Guide to Formwork for Concrete

Some portions of the Guide:


How do I configure NPS to allow connections from domain-joined computers only?

Question: I've created a new NPS network policy with the following settings:
Overview
 - Policy Enabled
 - Grant access
 - Type: Remote Access Server (VPN-Dial up)
Conditions
 - Machine Group: Domain Computers
Constraints
 - Authentication: EAP-MSCHAPv2, user can change password
 - NAS port type: VPN
Authentication is handled locally and not passed to RADIUS.
When I attempt to connect to the VPN my connection doesn't match the policy. I've tried using both "Machine Group" and "Windows Group" conditions. I've tried various other authentication methods. It seems to me that there is some additional step that I'm missing but cannot find any documentation on using Machine Group conditions.
This is the most helpful unhelpful article from Microsoft on the topic, and it only states "If the NAP enforcement method is 802.1X or VPN enforcement, members of the security group can be users or computers." Under "Settings" I've checked "NAP Enforcement" and there are no options to select different enforcement methods; we have no health policies created and are not using NAP at this time.
I must be missing something, but I don't know what. I've thought about setting up a CA and doing certificate authentication, but I don't think that should be necessary just to filter by computer security group membership.
:Edit:
So I gave this some more extensive troubleshooting on the 26th when I had a few more hours to devote to it, but I've been so busy I haven't been able to update this question. I enabled auditing and reviewed the detailed NPS logs which helped tremendously, in conjunction with this explanatory article from Microsoft.

Using a server type of "VPN" I was getting reason code 48, "IAS_NO_POLICY_MATCH". I discovered after copying our wireless policy (which uses machine group filter only and works) I found that the server type has to be set to "unspecified".
I then saw reason code 66 which translates to "IAS_INVALID_AUTH_TYPE", and found that I had mismatched authentication settings between the client and the server (doh). (This is most likely because I gave up testing with a copy of our regular VPN policy which uses MS-CHAPv2 and copied our wireless policy which uses PEAP and didn't update the client accordingly.)
I saw reason code 65 which translates to "IAS_DIALIN_DISABLED". This is where things get weird.
a. If I add a second, "AND", condition for user group membership (using user group conditions or windows group conditions) I get nowhere, same error code. (Using a single Windows Group condition for "Domain Computers" OR "VPN Users" allows VPN users in from any computer, but not any user from Domain Computers.)
b. If I set the policy to "Ignore user account dial-in properties", I get nowhere, same error code.
c. If I go to the user's AD object properties in ADUC and change the Dial-in properties from "Control access through NPS Network Policy" to "Allow access" everything works.

At this point I'm convinced there's some sort of bug or design flaw in NPS that is keeping this from working. I haven't had any success so far in finding any KB from MS with a hotfix or update to download, but the fact that other people seem to have this working tells me that something is broken in our environment. If anyone has any ideas what that might be, please let me know!
Answer: I would suggest changing the "Type of network access server" to "Unspecified".
Then add the condition "NAS Port Type:VPN"
I am using the condition "Windows Groups" successfully for machine accounts.
Comment: Thanks for the response. The day before you answered I was able to make a lot of progress on my troubleshooting, updating the question with my findings.


How to run shell-script at startup

Question: I want to run the sh.01 shell-script at start-up for a specific user and so far I've edited a crontab using crontab -e -u bristena in which I wrote @reboot /home/bristena/test1/sh.01
My question is when does the shell script sh.01 actually run? I've tried writing reboot in the terminal but after that, when I click the terminal again, sh.01 doesn't run. What do I have to do to see the shell-script running at start-up? Thank you so much
Comment: A `@reboot` job is run as soon as the cron daemon starts at system startup (this would likely be before you are logged in). What evidence do you have that the script is _not_ run?
Comment: @kusalananda I just assumed that if the contents of the shell-script do not appear on the terminal after I wrote `reboot` then it means that `sh.01` doesn't run. For example if the content of the shell script is `echo "Hello World"` then after I've edited the crontab as specified above and wrote `reboot` the first thing I would see when I open the terminal would be 'Hello World`. Is that not the case?
Comment: No. The output of cron jobs are mailed to the user of the job (assuming local email delivery is possible, otherwise you would never get the output). If you want to output to a file, then redirect the output of the job to a file. `@reboot` jobs are run as soon as the cron daemon starts, not just before it shuts down after a user issues the `reboot` command. Also, since this cron job is run even before you log in, and since cron jobs are run totally separate from terminals or whatever else you happen to be running, there is no way for you get that message in the terminal directly from the job.
Answer: In order for the script to run at boot, you need to register it in the /etc/rc.local file before the line exit 0. If you do not have this file, create it and paste the following contents into it:
#!/bin/sh -e
#here your script.
/usr/sbin/mescripts
exit 0

There is a directory /etc/network/ with subdirectories if-down.d, if-pre-up.d, if-post-down.d, if-up.d. If you place the script in one of these subdirectories, it will be executed accordingly when you turn it off, before turning it on, after turning it off, or when you turn on the network.
Another way is to specify one of the following directives in the /etc/network/ interfaces file: up, pre-up, post-up, down, pre-down, post-down. For example, the line:
post-up /path/to/script.sh

After turning on the network, it will execute the script.sh script. More details can be found in man interfaces.
In any case, the script must have rights that allow execution, otherwise it will not be able to start!
Comment: Scripts run via `rc.local` are running as root. The objective seems to be to run it as a specific user. You could do that with `su username -c '/path/to/script'`
Comment: @Kusalananda♦ You are right!
Comment: I'm afraid I don't see how the network hooks are relevant. The OP doesn't say anything about wanting to run a script depending on the state of a network interface. And network interface hooks also don't run under arbitrary user accounts.

How to run shell-script at startup


What is the etymology of "baca" and "baja", which seem to be antonyms with a single letter of difference?

Question: Why has my question What is the etymology of "baca" and "baja", which seem to be antonyms with a single letter of difference? been marked as off-topic? I have to discuss something about the two words "baca" and "baja". I tried searching on Google: https://www.google.com/search?q=spanish+%22baca%22+%2B+%22baja%22&oq=S&aqs=chrome.1.69i60j69i59j69i57j69i59j69i60l3j69i65.1968j0j7&sourceid=chrome&ie=UTF-8 But, I did not get any good results. When I do not find any good results on Google regarding a topic, I decide to post a discussion on StackExchange. Currently, I do not know any other sites to post discussions.
Comment: Note that StackExchange is not a site to post discussions, just concrete questions that can be answered with objective answers. If you really want to start a debate about something related to the Spanish language we suggest you to use [our official chat room](https://chat.stackexchange.com/rooms/46061/la-tertulia).
Answer: Questions about etymology are, of course, welcome on the site. As I am sure you have found out as a long time user of the site the source most people use is the dictionary of the Spanish Royal Academy https://dle.rae.es/?w=diccionario. This gives the etymology of each word, where it is known. So with a few clicks you could have discovered the etymology of both words. I cannot speak for the close voters but it seems to me that the view was that it showed lack of research effort.
Answer: Your Google search of

spanish "baca" + "baja"

is of course not going to bring any results about etymology.
The question is not a good fit for the site for several reasons. First, the etymologies of "baca" and "baja" are easy enough to find by Googling, hence the close reason "lack of research effort".
Second, the words "baca" and "baja" are completely unrelated, so your question asks two questions in one, which is also frowned upon on Stack Exchange. True, the two words differ in only one letter, but there are tens of words that differ in only one letter from "baca", such as "bata", "bala", "baba", "caca", "daca", "faca", "haca", "laca", "jaca", "maca", "paca", "saca", "vaca", "beca", "boca". So you could also ask why "baca" and "boca" have different meanings. Or why "baca" and "saca" have different meanings. But the answer would always be "because they are different words". As flooding the site with such questions would not bring any useful knowledge, it makes sense to close them as off-topic. But the good news is that the question already has an answer that is correct, so hopefully your problem has been solved.
Comment: @ArunabhBhattacharya it has already been stated that "baca" is just a noun for the top part of a car, while "baja" is an adjective. You could use it to say "la parte baja del coche", but still it is not the opposite of "baca", as we understand "baca" to be just a part of the car. You could also say "los bajos del coche" but not "la baja del coche". And still we do not consider those two word to be antonyms, just words referring to different parts of the car.
Comment: @ArunabhBhattacharya you could also say that "baba" comes from the head (**top**), which is the "opposite" of "baja" (**bottom**). Or that a "bala" has **high** speed, which is the "opposite" of "baja" (**low**). Or that a "saca" is a **closed** container used to carry things, and a "baca" is used to carry things in the **open**, which is the "opposite". If you define "opposites" so broadly, most pairs of words will be "opposites" by your definition. So then, "baca" and "baja" would not be a special case. But that is not how "opposites" are defined.
Comment: But, this is a special case of something at the top and something at the bottom that has just one letter difference. https://translate.google.com/#view=home&op=translate&sl=es&tl=en&text=Est%C3%A1%20en%20la%20baca.%0AEst%C3%A1%20en%20la%20baja.%0ADe%20la%20baca%20a%20la%20baja

What is the etymology of “baca” and “baja”, which seem to be antonyms with a single letter of difference?


Artificial Neural Network in MATLAB

Question: I am training an ANN on MATLAB. I am keeping the training set same. Everytime I train the network from scratch, I am receiving different output (or Performance). Is it something expected?
Answer: Yes, that is normal. However, the differences should be relatively small.
There are two main sources of randomness in neural network training:

Initialization of the network weight (usually drawn from some normal or uniform distribution with parameters related to the number of hidden units in preceding/followig layers)
Ordering of the training samples (they are usually randomly shuffled)

Some frameworks allow you to fix the random number generator seed before starting the training, which should ensure reproducibility of the same results. I don't know if that is the case of MATLAB though.
Answer: It's very expected.
You initialise the weights of NN randomly, so after completing (depends on the number of epochs you set) the optimisation, the weights that you end up are different for different initialisation of weights and since you use these weights to predict, the performance would be different.
To get same output every time you may use the same 'seed' everytime, see this for implementation in Matlab

Artificial Neural Network in MATLAB


Cutting out shapes inside cement board

Question: I need to cut out a shape (rectangular opening) inside a cement board. Was wondering if it can be done with a jigsaw and a special blade once I have pilot holes drilled in each corner.
Comment: Carbide blade should do it, perhaps slowly. A side-cutting router ("rotozip" et al) might also work; I know those will happily cut through tile.
Comment: Just try to keep the dust out of your powertools.  The dust from cement board and gypsum drywall is hard on powertool bearing and cause them to degrade more quickly.
Comment: I know, I already have a lot in my grinder from cutting brick and all over the expensive Makita battery
Comment: If you have a grinder, get a diamond blade. Cut outside if possible and wear at least an n95 mask.
Answer: There is no real experience needed when cutting an opening in cement board. I've seen openings for faucet handles created with nothing more than a well placed hammer strike (one hit each hole!). What ever tool you have available will suffice. I've drilled perforations with a masonry bit for a single shower valve. Oscillating tools with a carbide blade work. The primitive method is to cut the mesh with a utility knife and then force the board to break along the cut line. For a triangle cut not along an edge, mark the outline with a pencil, and drill a 3/8 inch hole at each of the 3 points. With an aggressive saw blade follow the lines to each 3/8 inch hole. If the edges are to jagged smooth with a rasp or  a whet stone.
Answer: I've cut out pieces in the middle of cement boards starting with a well placed whole saw drill bit for an opening, and following up that area with a sawzall shortblade for the actual shape.  Grab a spray bottle with water to control the dust.  It's a bit primitive but works well..
Good luck!
Answer: Yes, it can be done... Personally, I would avoid high speed cutting tools, and simply use a drywall knife.  It works very well.  Leave one of the 4 edges uncut to simply score with a utility knife (as usual) to snap it.  I've done this on several cement boards, and it works much better (imho) and without any dust.

Cutting out shapes inside cement board


Do I need a transit visa in Dublin?

Question: I'm an Indian citizen, holding a valid Canadian visitor's visa. I'm traveling from Canada through Dublin to another destination. Does Dublin require a transit visa?
Comment: What is your itinerary? Do you have a stop in the UK? What other visas do you have?
Answer: If you are not planning to leave the airport you will not need a transit visa. Citizens of India do not need transit visas in Ireland.

Do I need a transit visa in Dublin?


Windows 2012r2 domain environment and NTLM logins

Question: I would disable all NTLM in my domain environment, but before that I enabled on domain controller NTLM auditing, and I see some events 8004 with my local domain users and computers in these events description.
All my clients have Windows 10 installed, so why NTLM is still used in my environment, because it should be used Kerberos as default?
Comment: We aren't going to know why you clients with no information are using NTLM.
Answer: Have a read of Steve Syfus's blog entry here - nothing more needs to be said on the matter.  He covers all you need to know as to why somethings are happening and the path forward.
https://syfuhs.net/killing-ntlm-is-hard
Selection of interest:

And why are things using NTLM when they shouldn't? Well, for the two
properties I just described.

If a client doesn't have line of sight to a DC it can't do Kerberos, so it falls back to NTLM.

Server auth is forcing a downgrade to NTLM.

Further upon the second: NTLM doesn't do server authentication, so whatever application or process is not requesting or not handling server authentication, then kerberos can't work and then falls back to NTLM authentication.

In short, you're asking a question that only you can answer.  You need to investigate each of the entries in the log and ascertain why kerberos didn't work in each incident, then you can figure out how to fix it, or live with it.  If you can remediate them all, then you can disable NTLM.
Answer: To find the application which needs NTLM, you could add a test account to the domain group "Protected users" and logon with it and test all your applications one by one. Members off "Protected users" are disallowed to use NTLM, so for them, application authentication should fail straightaway when only NTLM is possible.


How to specify a compact topological 4-manifold with a finite amount of data

Question: Finite data for 4-manifolds: I have a somewhat hazy memory of seeing a Ph.D. thesis around 2005 which showed that any compact topological 4-manifold $M$ can be specified by a finite amount of data. The very rough idea is to exploit the fact that $M \setminus pt$ ($M$ minus a point) can be triangulated and explicitly give such a triangulation for a large initial segment $X$ of $M \setminus pt$, and an even larger initial segment $Y$ of $M \setminus pt$, together with a certificate that  $Y \setminus X$ contains a topologically flat embedded S^3 cutting off the end of $M \setminus pt$. This data allows you to build the closed topological manifold $M$ and argue that the result is unique. The important detail is how to give the required certificate. Over the years several people have asked me about this "finite data for 4-manifold" question. I would like to locate the reference, or failing that find time to write up a proof.
Comment: M-pt means $M$ minus a point?
Comment: Yes.  I've edited the question to make that clearer.
Comment: One approach is to use the alpha-approximation theorem. What's unclear however is how effective are the estimates.
Comment: Can any closed topological 4-manifold be smoothed by removing a fake 4-ball? Do homology spheres bound unique fake 4-balls up to homeomorphism?
Answer: I understand what you're getting at, but I think the statement "any compact topological 4-manifold can be specified by a finite amount of data" has a trivial answer (modulo the literature).  Cheeger and Kister proved that compact 4-manifolds are countable. So given a bijection of 4-manifolds with $\mathbb{N}$, each 4-manifold can be specified by an integer.
Of course, this is a cheeky answer, and not what your asking for. The content of your question is asking for a specific way to specify a 4-manifold, which is tied up in the certificate for a 3-sphere. I'm not aware of this work. But maybe the proof of Cheeger-Kister's theorem could be turned into a way to specify a 4-manifold?
Here's a possible example of how such a specification might go. A compact manifold can be specified by a finite collection of closed balls and embeddings between them, so that the equivalence class generated by these embeddings with the quotient topology gives the manifold. Embeddings of balls may be approximated by PL maps (which might no longer be embeddings, but should have the property that the set of double points is as small diameter as one please). Maybe there's some sort of criterion which would say that a collection of such maps between balls uniquely approximates a set of embeddings which gives a manifold? An existence criterion of this sort sounds trickier to me than a uniqueness criterion.
Comment: For me "specify" should mean one can check that the data presented in fact defines a manifold, and also, from that data there should be an algorithm that with increasing accuracy defines the points of a representative manifold in the homeomorphism type. The idea of using the Cheeger-Kister theorem, based on the Edwards-Kirby local contractibility of spaces of homeomorphisms, is quite interesting but the technical issue look daunting, at least to me.
Comment: Yes, homeomorphism classes, I should have clarified. For smooth manifolds, countability is even easier, since they are triangulable. But there are uncountably many smooth $R^4$s, and uncountably many homeomorphism classes of non-compact manifolds.
Comment: _...compact 4-manifolds are countable._  Homeomorphism classes of compact 4-manifolds? Otherwise we'd have some insight into the smooth Poincaré conjecture in dimension 4.
Answer: I happened to discuss this very same question with Fico last December. Maybe he is the one who was asking you.
What's written below makes sense in any dimension, but dimension 4 is the most interesting since one cannot use the results of Kirby and Siebenmann on existence of a handle decomposition. Note that a handle decomposition does not yet give a finitely description of a topological manifold since ones to specify the attaching maps. The same idea of a $\delta$-manifold allows one to deal with this issue by replacing homeomorphic attaching maps with $\delta$-homotopy equivalences of suitable subcomplexes.
Here is an approach using the $\alpha$-approximation theorem in dimension 4 (Theorem 4 in  "Curvature, tangentiality, and controlled topology" of Ferry and Weinberger, Inventions, 1991): if $M, N$ are compact 4-manifolds with boundary and $f: M\to N$ is $\delta$-homotopy-equivalence (with $\delta$ sufficiently small) which restricts to a homeomorphism on the boundary, then $f$ is $\epsilon$-homotopic to a homeomorphism. Here I am assuming that $M$ and $N$ are metrized; a $\delta$-homotopy-eqquivalence is a proper homotopy-equivalence such that tracks of homotopies to the identity have diameter $\le \delta$.
What's unclear to me is how effective is $\delta$ in this theorem, provided that, say, $M, N$ are triangulated and $f|\partial M$ is a PL homeomorphism.
Remark. I do not know if $B_{ij}$'s can be taken to be topological balls, this is related by my question about existence of good covers of topological manifolds.
Setting this issue aside, here is how one can use this theorem. A compact topological 4-manifold  can be defined in terms of a finite collection of 4-balls $B_i$ and partially defined gluing homeomorphisms
$$
f_{ij}: B_{ij}\subset B_i\to B_{ji}\subset B_j.
$$
I will replace these with a combinatorial data: triangulated 4-balls $C_j$ are piecewise-linear maps $g_{ij}: C_{ij}\to C_{ji}$. Here I am assuming that the subcomplexes $C_{ij}, C_{ji}$ are equipped with refinements of the original triangulations coming from $C_i, C_j$, so that each $g_{ij}$ is linear on each simplex.
The triangulations of $C_i$'s yield piecewise-Euclidean metrics on these balls in terms of which I  will define lengths of tracks of homotopies (which I assume to be piecewise-linear).
Let $X$ be the complex obtained by gluing $C_i$'s via the $g_{ij}$'s.
Definition. $X$ is a $\delta$-manifold if each $g_{ij}$ restricts to a homeomorphism
$$
\partial C_{ij}\to \partial C_{ji}
$$
and $g_{ij}$ is a $\delta$-homotopy-equivalence $C_{ij}\to C_{ji}$.
The point of this definition is that (compact) each $\delta$-manifold is a combinatorial creature and is encoded via a finite amount of data.
The alpha-approximation theorem then says that if $\delta$ is small enough (depending on what the $C_i, C_{ij}$'s are) then each $\delta$-manifold is homotopy-equivalent to a compact 4-dimensional topological manifold $M_X$ and, moreover, this manifold is unique up to a homeomorphism.
Furthermore, given a compact topological 4-manifold, represented via a system of gluing homeomorphisms $f_{ij}: B_{ij}\to B_{ji}$, one  approximates these homeomorphisms via PL maps which are $\delta$-homotopy-equivalences for arbitrarily small $\delta$. (There are some, possibly nasty, technicalities hidden here since the original maps $f_{ij}$ are defined on open subsets and those have to be replaced by slightly smaller finite subcomplexes.) Hence, every compact topological 4-manifold $M$ yields a $\delta$-manifold $X$.
Comment: Are the $B_{ij}$s and $C_{ij}$s balls?
Comment: @Ian Agol: This is unclear. It is related to my MO question about existence of good covers for topological 4-manifolds, which appears to be an open problem.
Comment: In a way what I write is similar to the proposal in the post: One can cover $M$ by two complexes instead of several. This might provide a useful simplification.
Answer: In my understanding, I guess that the following strategy could be be attempted. Let $M$ be a closed connected orientable 4-manifold (while nonorientable 4-manifolds are doubly covered by orientable ones). Surgerying $M$ along finitely many embedded tame circles produces a simply connected 4-manifold $M'$. Then, $M$ can be recovered from a certain simply connected manifold by surgerying finitely many pairwise disjoint locally flat 2-spheres with trivial normal bundle. Now, simply connected 4-manifolds are classified by Mike Freedman's celebrated theorem in terms of the intersection form and the Kirby-Siebenmann invariant (which amounts to finite data). It remains to understand how much data we need to determine the embedded spheres to be surgered in a simply connected 4-manifold. Of course, we need more than homotopy (= homology since $\pi_1 = 0$) classes.
Comment: This is quite different from the argument I sketch but I like it. Indeed the important detail is giving a finite description of the imbedded 2-spheres building on a finite description of the 1-connected manifold. This is a little tricky, and as far as I see, will still need some work. ( I also do not know how to make the delta-manifold idea precise.)  I greatly appreciate the input from Ian, Misha, and Daniele. If the reference I was looking for does not turn up in a couple weeks I will write up something. My present understanding is not succinct enough to just write it out on Mathoverflow.


Create Collection with Animation Nodes

Question: I'm sure this is possible with a custom script node but is there any out of the box way to create a collection with animation nodes? Currently I'm creating a bunch of objects in my node graph and would like to group them into a collection. I.e every 3 objects gets put into a new collection.
Answer: No, you cannot create collections with Animation Nodes. If you need to group objects then you can create a list of objects then iterate in them with loops or use vectorized nodes. Or you can just create collections manually.

Create Collection with Animation Nodes


Mass Effect on Slingshot Motion?

Question: For my physics class (I'm a high school student), we created slingshots. Our task is to predict the distance a projectile, launched from a slingshot using surgical tubing, would land. We aren't given the mass of the projectile until the day of testing, so we would have to use a graph to find out the distance. My partner and I conducted a series of tests comparing mass to distance from a given pullback length ($55$ cm). The angle the projectile is launching from is $54^\circ$. K is not linear, but for our set pullback length our K value is $100$ (N/m). Our results show a cubic, or possibly quadratic graph. Why is this? Why would the relationship between mass launched and distance follow this shape?  Here is a graph of our data:
Comment: Are all projectiles of same dimensions ?
Comment: My guess is that for low-mass projectiles the surgical tubing isn't able to impart all of its stored energy which is why you see it ramp up slowly.
Comment: All projectiles are of the same dimensions. They are rubber racquetballs.
Answer: I congratulate your teacher on posing a fascinating intellectual challenge. So here's my guess (as a former physics student turned (medical) physician) constructed by analogy with the typical analysis of simple harmonic motion. In that situation with a spring constant of K and the force dependent on instantaneous displacement from the center of the oscillation, there is a resonant frequency that is a function of the mass and the spring constant. You are essentially looking at one-half of such an oscillator, so I think there would be an optimal ratio of mass to spring tension that would achieve the maximal transfer of energy from tubing to projectile. The resonant frequency of such a system would be one half the inverse of the time from release to the midpoint of the slingshot. (This of course assumes you can measure the time from release to crossing the slingshot "Y", but I'm sure you have some high-speed cameras around for that task, right?)
Do some searching on this website or on Wikipedia for the calculation of resonant frequency in "simple harmonic motion" and measure the spring constant of your slingshot. See if you can pull all these together for an A+ scientific report describing your experimental results!
Answer: The calculations are going a bit long, but I have an approximate explanation, Just include viscous force given by stokes law in the equations of parabolic/projectile motion and then calculate the distance/range of projectile. Here goes :

At any time $t$ the viscous force on the projectile will be $6\pi\eta a v$ if the radius of "spherical" ball is $a$ and it is moving with $v$ velocity.
  Note : $\eta$ is the viscosity of fluid/air the ball moves in.
  Breaking force into components,
$F_x = {-6}\pi\eta a v \cos\theta$
  $F_y = {-6}\pi\eta a v \sin\theta$
  ${d{v_x}}/{dt} = (({-6}\pi\eta a {v_x})/m) dt$
  ${d{v_y}}/{dt} = (({-6}\pi\eta a {v_y} + mg)/m) dt$
  $v_x = u \cos\theta e^{({-6}\pi\eta a t)/m}$
  $v_y = ((mg + 6\pi\eta a u \sin\theta) e^{({-6}\pi\eta a t)/m} - mg)/(6 \pi\eta a)$
$dx = v_x dt$ on integrating:
  $R = (m u \cos\theta)/({6 \pi \eta a}) × [ 1 - e^{({-6}\pi\eta a T)/m}]$ T is time taken to cover range.
Assuming you get at $t = T$, $v_y = -u \sin\theta$, then putting value $v_y = - u sin\theta$ in equation for $v_y$ solving for $t$ and putting in equation of $R$, we get,
  $ R = (m u^2 \sin{2\theta})/(mg + 6 \pi\eta a u \sin\theta)$
Now since you are using a spring to launch the projectile, we have
  $K x^2 = m u^2$
  $R = K x^2 \sin{2\theta} [\sqrt[2]{m} / (m^{3/2} g + 6 \pi\eta a x \sqrt[2]{K} \sin\theta) ] $
This implies
  $ R \propto 1/(mg + A/{\sqrt[2]{m}}) $
If you differentiate $R$ with respect to $m$ you will find that a maxima is achieved when $ m = A/(2 m^{3/2}) $
  Here $ A = 6 \pi\eta a x \sqrt[2]{K} \sin\theta)$

Note :
1.  I have assumed that while landing $v_y = {- u \sin\theta}$ This maybe a close approximation but it is not exact, to find exact equation you have to integrate for height the same way I have done for range and then find at what times it is zero, since the equations are far too complex I have omitted them and taken approximations.
2. I have assumed projectiles to be moving in a fluid i.e. air.
3. I have also assumed air to be simply present, not moving.
Comment: You can use the `\cos` and `\sin` syntax in math in order to render as a function and not as a variable. I did the edits for you.
Answer: Assuming throwing force and launch angle were the same for all projectiles, the answer is probably much simpler than DWin's.
The effect of the air resistance on the lighter projectiles was greater than fore the heavier ones, whereas the heavier objects fell short due to lower speed in the first place, because the throwing force was not able to accelerate them as much as the lighter ones.

Mass Effect on Slingshot Motion?


Is it safe to install dotnet 3.5 on an IIS server running a dotnet 1.1 web application?

Question: If I recall correctly, this is fine, the different versions coexist peacefully, but I just want to double-check there's no possibility of problems (I'm installing the newer version of the .net framework on an older production server in preparation for upgrading a critical asp.net 1.1 app to 3.5 in the near future).
Answer: As long as the two applications are running in a different AppPool, it's like having two separate servers. No problems.
Comment: +1 - .nET version is decided per application pool. Just keep them in separate pools, you will be fine.
Answer: As Moshe mentioned, it is the AppPool that matters with IIS.  With .NET in general, 1.1 and 3.5 can co-exist without interference because they are running on different cores.  .NET 4.0 is also completely separate from the earlier versions.  Microsoft has a pretty decent article that covers the versions and dependencies:
The relationships between the .NET Framework versions 2.0, 3.0, and 3.5 differs from the relationships between versions 1.0, 1.1, and 2.0. The .NET Framework 1.0, 1.1, and 2.0 are completely separate from one another, and one version can be present on a computer regardless of whether the other versions are present. When versions 1.0, 1.1, and 2.0 are on the same computer, each version has its own common language runtime, class libraries, compiler, and so forth. Application developers can choose which version to target. For more information, see Side-by-Side Execution, Targeting a Specific .NET Framework Version or Profile, and Using MSBuild to Target Specific Versions of the .NET Framework.
http://msdn.microsoft.com/en-us/library/bb822049.aspx


Unable to eject DVD

Question: When a DVD is inserted into the drive, it will play and work as normal, however it refuses to eject. I've tried via the command line as well as the eject button. I remember a while back finding some code to add to a file (not helpful, I know!) which basically prevented the drive from locking. Can anyone point me in the right direction?
Answer: It is not a good idea to eject a disc while it is mounted into the file system. Many application don't expect that and might not work properly anymore. Also in some rare cases a forced eject can to physical damage to the drive or media.
To prevent ejecting a mounted media Linux usually prevents to eject via the the button on the drive. If the disk in unmounted, you eject normally.
The most easy way to do that is to use Nautilus (the file manager) and click the eject button next to the drive. This will unmount and eject the disc.
In XBMC there is usually an option to do that as well, where depends on the used skin.
You can control the locking behavior with the eject command:
eject -i on /dev/cdrom
eject -i off /dev/cdrom

man eject will give you a list of arguments you can supply to eject some might also be helpful in getting more control over the drive's ejection behavior.
Comment: I know what you mean, except that this PC is solely used for running XBMC Media Center so I don't really have any access to Nautilus or terminal. I want to be able to press eject on the DVD drive and get the disc out

Unable to eject DVD


How to fix Android WebView crash due to pending MotionEvent

Question: My Android app is experiencing this crash randomly during operation, and I think it is due to a pending MotionEvent that is dispatched to a null object, but not sure.
here is the crash output:
java.lang.NullPointerException
at android.webkit.BrowserFrame.getRequestInterceptor(BrowserFrame.java:1108)
at android.webkit.FrameLoader.handleRequestIntercept(FrameLoader.java:426)
at android.webkit.FrameLoader.handleHTTPLoad(FrameLoader.java:226)
at android.webkit.WebViewWorker.handleMessage(WebViewWorker.java:124)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:143)
at android.os.HandlerThread.run(HandlerThread.java:60)

My Android app manually creates a custom WebView and adds it to the ViewGroup in the Activity.onCreate() method like this:
ViewGroup groupA = (ViewGroup)findViewById(R.id.frame_layout_rowA);
webViewRowA = new MyWebView(this);
groupA.addView(webViewRowA);

The reason for doing it this way was to be able to get to the constructor for the WebView in order to pass getApplicationContext() instead of this to the constructor, which was a workaround for a memory leak in 2.1.
The issue, I think, is that this Activity is restarted frequently.  This causes the normal chain of onStop(), onDestroy(), onCreate(), etc... to happen often.
So my question is, could the crashes be due to a MotionEvent being dispatched to an instance of MyWebView that was attached to an old Activity that has been garbage collected?  Such as if the user clicked something in a webview right before this actvity was recycled?
Another thing to note is I'm seeing these messages following a call to onDestroy()
/webviewglue(  436): nativeDestroy view: 0xd738d0

Any help or insight anyone might have, would be greatly appreciated.  I've been banging away at this issue for a while now.
Oh, one other thing to note....this started happening in Android OS 2.2.  I've submitted a bug to Google, but not sure it is their issue.
Thanks in advance.
Answer: The android market gives me 360 reports a week about this issue.
The problem is that my webview is not even created on the fly.
I have found this on the web: https://code.google.com/p/android/issues/detail?id=11533
Still waiting for replies.
It looks like it's related to some phone models. Could you replicate this issue? I've never been able.
Thanks
rafa


Is DD Image disk writing permanent?

Question: I was using rufus to install Ubuntu, but I came across an odd thing. It basically said that the iso i was using was a hybrid, and that i had a choice to do ISO image mode, or DD image mode. I had no idea what DD was, so i did ISO, but i could not get the PC to boot from that, so I wanted to do DD, but then I noticed that it said it recommended ISO because of full use of the drive. This made me think that DD might be permanent. Yes, I have no idea what im doing and my research is no help. I just need a yes or no answer and maybe a simple explanation.
Comment: I don't know the exact difference because I don't know how ISO mode works (probably it just proportionally grows the image file you provide to exactly fit the device size), but `dd` is definitely not permanent. It writes the data in exactly the same way any other tool would do, and it can always be overwritten again later.
Comment: thx! that's exactly the answer i needed.
Comment: Converted that comment into an answer, so that you can accept it and mark your question as solved - if it is, of course.
Answer: dd is a cloning tool
dd always makes a 1:1 copy, writing exactly what it reads. Standard Ubuntu iso files are approximately 1.5 GiB and they are 'hybrid' iso files, which means that the same structure will boot from a DVD drive and a USB drive (or a memory card).
This structure has a special boot sector and the ISO9660 file system, which is read-only. So you can boot from the drive, but you cannot write to it (not use it for storage).
dd can clone any file to a USB drive or memory card, for example an image file of an installed system, for example for Raspberry Pi. The result depends more on the content of the file than on dd itself.
dd is a powerful but dangerous tool, because it does what you tell it to do without questions, even if you tell it to wipe the family pictures. There is no final checkpoint, where you can make sure that everything is correct, and a small typing error is enough to clone to and overwrite the wrong drive.
Therefore I would recommend other cloning tools, that are safer, because they help you identify the correct target drive and let you double-check, that you clone to and overwrite the correct drive.
Examples:

The Ubuntu Startup Disk Creator in Ubuntu version 16.04 LTS and newer versions
'Disks' aiias gnome-disks
mkusb (when cloning which is the standard mode for linux iso files)
Rufus (dd mode)
Win32 Disk Imager

Extracting tools
Other tools do not clone but extract the content from the iso file and modify it (copy to a read-write file system and fix the bootloader). This requires that the tools recognize the boot structure of the iso file, and when it changes, such tools will fail. An extracting tool will get problems with new versions of a linux distro, if the boot structure changes from the previous version, until the tool is modified to take that into account.
Examples:

The Ubuntu Startup Disk Creator in Ubuntu versions before 16.04 LTS
Unetbootin
Rufus (ISO mode)
mkusb (when creating Ubuntu persistent live drives or Windows install drives)

Restore to a standard storage drive
It is possible to restore a cloned USB boot drive with Ubuntu to a standard storage drive unless the drive hardware is damaged (for example by excessive wear). You can use several tools to do it, for example mkusb, which can

Clone from an iso file or a compressed image file to a live-only USB drive
Extract from an iso file and create a persistent live USB drive or a Windows install drive
Wipe a USB drive
Restore a USB drive to a standard storage drive (after it was used to install Ubuntu).
Answer: The short and simple answer is no.
dd can not do permanent modifications to your devices.
All it does is writing to the block device file descriptor provided by the Linux kernel, which is what every other tool would do too at some point. The technical process of writing data to the device is always the same.
What probably makes the difference is how the disk image you want to write is interpreted. dd always makes a 1:1 copy, writing exactly what it reads. This also means that if your image is 1GB big, but your device has 4GB space, only 1GB will be used and the rest remains as unpartitioned space.
I guess that the ISO mode you describe would expand the image while writing, so that it finally covers the whole device, making use of the free space and including it into the usable partition...
Answer: ISO mode just lets you access the drive in Windows still, and have it show up like a CD. DD mode writes the image to the drive in a native, raw manner, which will cause the drive to no longer be visible in Windows Explorer. ISO mode is easier for people to understand and use, which is one of the reasons they recommend it.
You can always repartition and format the drive and use it again after a DD write.

Is DD Image disk writing permanent?


Why can I hear what sounds like a child talking to me on Minecraft?

Question: I'm doing a multiplayer with a friend. I was near a cave when I heard the usual wind and creepy sounds you hear in the game. But I picked up a word. I realised that there was a voice but all I heard was 'You'. I freaked out and got off the game. I went back on it later that night and I was hiding in my hut (near the same cave, but not enough that I can see it) and I heard what sounded like a child's whine, before it deepened and turned to a creepy, glitchy, evil gurgle. I got off it straight away and my friend hasn't heard it.
EDIT: I can't find any answers anywhere. Also we are using the OZOcraft resource pack, could that be the answer?
Comment: Were you in the overworld or in the Nether? it might have been a ghast, but given that you use a resource pack, it's hard to say.
Comment: disable the resource pack and try again if it's still there
Comment: If you do what dly says but still don't know try looking in the resource pack. Find the sounds folder and play the sounds. It could also help if you recorded it and posted the sound here for us.
Answer: This is caused by your resource pack "OzoCraft"
A quick google search comes up that yes, "OzoCraft" Resource pack adds sounds that can be described "voices". I spent some time and downloaded the resource pack, and looked through it's audio files. It is indeed the ambient cave sounds, precisely 2 to 6.


Researchers describe emotions as either "positive" or "negative". But can emotions be "right" or "wrong"?

Question: Could it be regarded as either right or wrong from being tied to either positive or negative connotations?
See: On "Positive" and "Negative" Emotions by Robert C. Solomon and Lori D. Stone
Comment: "*People really struggle with the question of whether their feelings are right or wrong. Wrong question! Feelings are neither — they just are*". [Psychology Today](https://www.psychologytoday.com/us/blog/shift-mind/201005/can-your-feelings-be-wrong).
Comment: Emotion Can be described by Changing Consciousness. We have two types of emotion: Conscious Emotion and Unconscios Emotion. But if you assume , Emotion is relative!, then the meaning of positive Emotion can be much complicated . So you need to solve the problem of "positivity" of relative emotion in vertical and horizontal direction. Relative emotion can be described by the problem of Changing in Relative Concept of Consciousness.
Comment: Welcome to SE Philosophy! Thanks for your contribution. Please take a quick moment to take the [tour](https://philosophy.stackexchange.com/tour) or find [help](https://philosophy.stackexchange.com/help). You can perform [searches here](https://philosophy.stackexchange.com/search) or seek additional clarification at the [meta site](https://philosophy.meta.stackexchange.com/). Don't forget, when someone has answered your question, you can click on the checkmark to reward the contributor.
Comment: I think my sources - Hume, Brentano, and Bernard Williams - count as reputable.
Answer: Short Answer

But can emotions be "right" or "wrong"?

Yes, depending on one's metaphysics.
Long Answer
In Catholic theology, the venial and mortal sins specifically list emotions that are both wrong and forbidden. Indeed, a case can be made that 'lust' is arguably the most religiously regulated emotional impulse. While not recognized as emotions in the same way a behaviorist might define them, nonetheless they were considered "evil thoughts" by theologians and still are addressed in Catholic confessional. From WP:

Gula (gluttony)
Luxuria/Fornicatio (lust, fornication)
Avaritia (avarice/greed)
Tristitia (sorrow/despair/despondency)
Ira (wrath)
Acedia (sloth)
Vanagloria (vainglory)
Superbia (pride, hubris)

Indeed, coveting thy neighbor's wife is one of the prohibitions given under Mosaic law.
As an athiest, of course, my personal metaphysical presuppositions align nicely with emotions from a perspective of cognitive science where using a much lesser judgmental lingo, behaviors are seen in the context of functionality in society granting wide-latitude in interpretation of cultural context. A very prominent of example of this language is embodied by the necessary and sufficient criteria of having a personality disorder as addressed by the DSM-5. Conifold's quotation above:

"People really struggle with the question of whether their feelings are right or wrong. Wrong question! Feelings are neither — they just are". Psychology Today. – Conifold Oct 15 at 8:32

reflects this sort of value-neutralized stance towards emotion that are often used to build a patient-therpaist relationship, although therapists of all stripes conform to general legal, ethical, and moral norms in their society.
To close, whether or not emotions can be right or wrong is derived from your metaphysical value-theoretic orientation.
Answer: As a mere psychological occurrence, an emotion cannot be right or wrong. Hume caught this point when he observed that as 'original existences', mere psychological states or happenings, emotions (or 'passions' as he called them) are not 'representative' - reportive or descriptive - of any state of affairs and therefore cannot be true or false, right or wrong. However, there are three further angles on emotions.

Under an identifying description, such as 'envy' or 'jealousy' or 'pity', an emotion can be right or wrong in the sense of being ethically correct or incorrect, morally appropriate or inapppropriate, something which it right or wrong (morally desirable or morally undesirable) for us to have or at least to act on.

An emotion can be wrong, morally wrong, if it is misdirected. If I am angry with X and extend my anger to Y, who has no connection with the situation, then anger is a wrong emotion to direct at Y.

We are defective as moral agents if we do not experience certain emotions in particular situations. For instance, pity and anger are the right emotions to have and to act on if we see people torturing someone else. In context such emotions are ethically correct, hence right.

References
F. Brentano, The True and the Evident, London: Routledge, 1966 (1st ed., German, 1889): 21-2, 147, 151-2, 182 on the 'correctness' of emotions.
D. Hume, A Treatise of Human Nature, Oxford: 1978 (originally 1739-40): II.3.3 & III.I.1: 415, 458.
Bernard Williams, 'Morality and the Emotions', Problems of the Self, Cambridge: CUP, ch. 13: 207-229.
Comment: I like number 3.
Comment: @ Aleksandr A. Adamov : Thanks for comment, much appreciated - Geoffrey
Answer: The problem is the final goal. Good and bad (right and wrong) depend on the goal. If I want to die, poison is good. If I want to continue living, poison is bad.
In case of considering that our ultimate goal is survival (not only existence, this instant, but also persistence in the long term, that is, to exist forever) (some consider it debatable), any good is such because it tends to improve the survival probabilities. So, any emotion that leads to an increment of the probability of survival (even if infinitesimal) would be good.
As an example, let's take anger. The emotion is good on the short term because it allows catharsis, liberates tensions, etc. But it could affect destructively social relationships and perhaps self integrity, which implies isolation and possibly death. So, on the long term, it is bad.
So, under this view, bad, wrong, negative or destructive are equivalent, and conversely.
Remark that assessing the change of probability of survival due to the outcome of an emotion is an extremely complex problem. But that is out of the scope of the question. The answer focuses only on the apparent relationship between emotions and good.
Comment: For an interesting take on the nature of human emotions, see; the "Ethics" Part 3- On the Emotions" . Spinoza  depicts their relative status as either good or bad, but his line of demarcation is between 'active' emotions which enhance our capability to understand our lives and the 'passive' emotions which detract from that ability to thrive and further more or less enslave us into a negative thought and behavior pattern which renders us helpless.
Answer: A viewer, when looking from outside, may be interpreting emotions as positive or negative. But we cannot say that so. It might be for some balancing in the person's bodily functions. Sometimes it might be because the viewer's EQ is not so perfect.
The great men who sacrificed their lives for the society were not because they often had negative emotions (sympathy, empathy etc). Can't we consider that it was for balancing the emotions of the coming generation? If they had ego in them they would have said 'others have negative emotions' (... since we are pitiless in understanding the feelings of a downtrodden society). In the same way we cannot also say emotions as right or wrong.
When there are several emotions how can we differentiate and plot them on a single straight-line or on different straight-lines, plotting a zero?  How can we define the zero (... for that purpose) and confirm that it is always fixed on that particular position in all cases?  If that zero is deviating from its position in different cases, how can we confirm that an emotion is always positive or negative?
Answer: Yes, most definitely! As long as our actions can be characterized that way -- right or wrong, or in-between -- emotions must land somewhere on that spectrum, between right and wrong.
It becomes rather obvious, once we realize why we have emotions, what is their purpose? -- they are a rather crude way our subconsciousness, upon recognizing the circumstances we found ourselves in, suggests to us what our next move should be. That suggestion can be anywhere from right to wrong, and that's how the emotion gets its label (right = being appropriate in given circumstances).
One thing to remember here is that we have no immediate control over what emotion we feel (or don't) at any given moment. So, at times, every one of us ends up in an inappropriate emotional state -- and that's OK. There is nothing wrong with that, and I don't see much value in trying to fix it. What we should focus instead is on developing a better understanding of our surroundings, of what the people around us are going through -- sometimes by putting ourselves in their shoes to try and understand what would make us behave the way they do.
As we are getting better at understanding, we would develop an emotional connection as well -- we call it compassion. As an added benefit, it is through learning compassion for others (and especially to people we don't like, even our enemies) we would be developing compassion for ourselves (because we are our worst enemy ;) BTW, I'm talking the infamous self-love here (because when say self-love, they really mean self-compassion).
Comment: Laughing and crying are compensational emotions where the mediation between body and conscious self fails (see Plessner), there is no motivational aspect there. Also, you seem to contradict yourself when claiming that emotions are right or wrong corresponding to their appropriateness (appropriate to what? Social role? Self-expectation?Bible?), while you say in the following paragraph that there was nothing wrong with 'inappropriate' emotions. Now, what is it? It would help to build answers on philosophical texts instead of writing down whatever comes to one's mind reading the question.
Comment: @PhilipKlöcking -- laughing and crying is a state of being overwhelmed with emotions, they are not emotions themselves. What appears to you as a "contradiction" is, in fact, me talking about two separate phenomena. One is about being objectively right, the other is about being alright/doing well. Your emotional state might be inappropriate, but having it is not itself an issue.
Answer: Every emotion is either right or wrong.
The reason, as noted elsewhere, is that right or wrong can only be designated within a purposeful framework. And emotions only and always occur within such purposeful frameworks.
So what you really mean is, can "purposeful frameworks" be reduced to single "universal" framework, in the manner of a natural law? This is doubtful. We can look to "The Good" in ancient philosophy or "The Kingdom of Ends" in Kantian terms, and many other absolutist schemes.
But since Hobbes and the rise of the modern "individual" to define such universal ends contradicts the freedom rational individuals are presumed to have in any moral scheme, any framework of right and wrong. Taken to an extreme, some versions of "emotivism" in analytical philosophy would say that any statement of right or wrong is nothing more than the expression of an emotion, with zero truth value.
A modern contradiction looms. Since the freedom to choose is presumed in all moral situations and "emotions" are presumed to not be freely chosen, the traditional advice is to moderate the emotions, most explicitly in Stoicism, Buddhism, or any form of asceticism. Is there any framework we can apply to all moral beings? Probably Kant comes the closest and, indeed, the "golden rule" seems to be about as universal as anything, associated with the emotions of empathy leading to kindness.
But even this would not be recognized as a virtue by the Ancients, and "empathy" itself is arguably not an emotion, just a contagion of emotions. So, all emotions are always right or wrong because they only exist in purposive frameworks. Is there a universal purposive framework? That, as Hegel might put it, is a work in progress.
Answer: No. Not in the general sense.
They are only "good" or "bad" because of the situation.
"Bad" emotions can be "good" if you use them to better yourself.
Examples:

Jealousy is a bad feeling, but it is good to be jealous of someone with a better work ethic than you
Hate of a bad feeling, but it's good to hate a murderer (hitler, Stalin, etc)

"Good" emotions can be "bad" if you use them in the wrong situation.
Examples:

Loving hitler
Being nice to an evil person (hitler, etc)

Emotions are "good" or "bad" when they are used in the wrong situation. As opposed to most things being "good" or "bad" in relation to the moral scale.

Researchers describe emotions as either “positive” or “negative”. But can emotions be “right” or “wrong”?


Power of a capacitor when is connected to a battery

Question: According to definition of power ( current times voltage) since there is no change in charge, the power stored in a capacitor connected to a DC voltage is zero. Since energy is power times time, Energy stored is Zero too. But we know in a transient period the capacitor gets charged up when it is connected to a DC voltage and there is energy stored. if I discconected the charged capacitor and connect it to an inductor for example this charge get discharged. So how come there is stored energy but mathematically it is zero?
Comment: Energy is the integral of power. So energy accumulates in the capacitor during the transient period. When the capacitor is fully charged (i.e. capacitor voltage = supply voltage), there is zero current so there is no further increase in the energy already stored.
Answer: Power is not stored. Energy is stored. Power is the rate at which energy is transferred.
Think about your electricity meter. You get charged for kW hour usage. kW hours are "so many" kilo watts consumed x the number of hours you have consumed those kW for. You have a big number on your meter that tells you how many kWh you have accumulated over so many years. That number is your total energy usage over that period. 1 joule is 1 watt-second. 1000 joules is 1 kW-second and 3.6 M joules is 1 kWh.
If the number on your meter was unchanged over a short period of time then the power taken over that short period of time is zero.
In other words, energy can be stored (or metered or accumulated) over a period of time and the value it accumulates to remains steady even if the actual power drawn (at a particular moment in time) is zero.
Comment: But aren't energy and power related? If power is zero then the stored energy is zero?
Comment: Power is \$\frac{dW}{dt}\$ where W is work or energy. If energy is constant then \$\frac{dW}{dt}\$ = zero and power = 0
Answer: You are correct, in DC operation the capacitor power is zero; the cap does no work. This means that the energy being stored during any period of time of constant voltage is zero. This does not mean that the capacitor is not storing energy, merely that the amount of energy stored in the capacitor has not changed during the monitored period.


Best mathematics conference?

Question: One conference per answer. Explain why it was great (mathematically or otherwise), and preferably post a link to the conference website or to abstracts/proceedings.
Comment: **Community opinion** (expressed by downvoting) seems to suggest that your question would be more appropriate on a different forum, so I'm voting to close your question as "off topic". Note that your question is interesting and I would like to answer it as well as read the answers -- but this interaction should happen in a different place, not on Stack Exchange-based platforms.
Comment: Different conferences serve different needs for different people, and one person's "great conference" might be someone else's nightmare for a hundred different reasons. I imagine a similar but better-formed question could be appropriate for MO, but as stated this one really isn't.
Comment: If it's fine with the community, it's fine with me, sorry for the buzz :)
Comment: And you're invited to join the thread at http://tea.mathoverflow.net/discussion/44/soft-questions-on-mathoverflow
Comment: Of course the notion of a "best" math conference is not absolute, which is why I'm interested to learn about what people like about a conference, and how conferences are run in different fields. If the question is downvoted to -7, or if there aren't many answers, I'll close it.
Answer: The famous AMS Summer Research Institute on Automorphic Representations and L-functions held at Corvallis in 1977. It was organized by Borel, Casselman, Deligne, Jacquet, Langlands, and Tate to give a coherent account of the state of the Langlands program. Beyond the organizers, speakers included Springer, Tits, Cartier, Lusztig, Piatetski-Shapiro and Arthur. Generally, speakers were assigned topics to talk on.  The proceedings have been a wonderful resource during the thirty years since they were published. They are available on the AMS website (http://www.ams.org/online_bks/online_author.html#B).
Answer: Now that this is turned into a community wiki post, I'll throw an answer out there: No, a non-answer!
And my non-answer is this: There are too many conferences, and the vast majority of them too specialized for most of us, to answer this question in a way that would be useful to most mathematicians. (Yeah, I am sticking my neck out here, speaking for "most mathematicians" when it's not altogether clear that I am competent to speak for myself.)
I tend to prefer narrowly focused conferences myself, in a field that I actually know something about. That way, I can at least feel appropriately ashamed when I can't follow a talk on a subject I had thought I understood. Which provides an incentive to do something about it. So if I may add to the original question, then? Why do people go to big general conferences? What do they get out of it? Okay, this may sound too negative. Breadth is good, and I wish I had more of it, but mathematics is a vast field and only a few of us can attain deep understanding in more than a couple of subfields, at best.
Comment: One reason to go to a big conference is that there are often talks by good speakers on subjects outside my area.  Even if I don't plan to work on the subject area of the talk, it is nice to hear about interesting mathematics in general, and current developments in particular.
Answer: The 1900's Paris ICM... just because of Hilbert's talk, in which he modelled the shape of a rather big amount of the mathematics that were to come; and not just by becoming fancy, but by identifying really difficult and interesting problems and, even more importantly, by pointing to logic and rigor so that others could see the necessity for a thorough cleaning of their mathematical building.
(Sorry, I could not locate any link to the proceedings ;P)
Answer: The Talbot workshops are mostly aimed at graduate students and early professionals.  The topics and plenary speakers vary year-to-year, but the ones I have attended were all very illuminating.  The 2009 workshop, on the Fukaya category, was especially good, and there are notes from each talk on the web page linked above.
Answer: I'll start. The New Zealand Institute of Mathematics holds a conference every year, a different location and topic each time. In 2006, at Taipa, the topic was geometric topology. Jeff Cheeger gave an excellent plenary series of talks on spaces of Einstein metrics. He and Tian proved certain collapsing results for these metrics, laying the framework for compactifying moduli spaces of Einstein metrics.  There were two talks in the morning, and one in the evening after dinner, leaving the afternoon free for activities such as windsurfing. If you can make it, I recommend it. This year (January 2010) will be on quantum topology (although I have to say I won't be able to go).
Answer: The Solvay Conference (see http://en.wikipedia.org/wiki/Solvay_Conference), although formally being a physics conference, was attended by Poincare and was fundamental to establishing quantum mechanics and general relativity as important topics in mathematical physics.

Best mathematics conference?


How do you stop a hacker from changing passwords in your DB directly, if they're already in a position to steal the DB?

Question: I've been researching the methods of securely storing user passwords in a database (by only storing the hashed password, with a strong algorithm, along with a salt, and deriving the key after so many iterations, like pbkdf2).  This is great for if my server ever gets hacked and my database stolen.  But can't the hacker just change the passwords in the database directly, along with the salt used to generate them?
Comment: These are very generic questions that belong more in the realm of software architecture, and the answer would be long. As a start, you can build your app to have different DB users, schema's, hashes stored in separate tables/DBs, etc. Most websites just use one DB user for everything, so you can start there. You should also train the developers not to store passwords in their git repo, etc, etc.
Comment: Different servers may be overkill for your application, but yes, Facebook probably does that.
Comment: Another reason for protecting the passwords is that a lot of people re-use the same password on multiple sites - so a stolen list of usernames and passwords can be tried on multiple sites and result in break-ins.
Comment: That's what I was thinking - like the password db on one server, and user information in a db on a different server.
Comment: I've updated my question to be more concise.
Answer: Try this out it might interest you -
http://privacypolicies.com/blog/stop-hackers/
Comment: This is useful, Oron.  I think I'm going to close this question as being too vague :(
Comment: nvm - couldn't delete so reworded title of question.


Does only custom post type have post type archive pages?

Question: is_post_type_archive (string|array $post_types = '' )
Is the query for existing post type archive page?
Reference: https://developer.wordpress.org/reference/functions/is_post_type_archive/
I search on WordPress and Google for post type archive I only see custom post type archive article. Does only custom post type have post type archive page?
The WordPress internal post type like post, page, attachment and so on doen't have a post type archive page? If they have, how can I access the page?
Answer: There is no archive pages for the build in post types, only for custom post types when has_archive is set.
In general, the homepage is accepted to be the archive page for the post type post, but it is not an official archive page in the sense of custom post type archive pages.
You can create archive pages for the build in post types, but that will require some kind of rewrite rules and custom URL structure


Is popcorn FX plugin for Unity compatible with webGL?

Question: Is popcornFX plugin for Unity compatible with WebGL? If not, is there a way to get it compatible on a web browser?
Comment: Is this a browser plugin or something you install on the web server? If it is a browser plug-in, then this is not the right site for your question. Sorry. We deal in webmastering issues as it relates to the server, search, social media, how a web masters code is presented in a browser, etc. Cheers!!
Answer: This is not possible for the moment. We are planning on porting PopcornFX to WebGL, but this is a long-term goal and this feature will not be available any time soon.


Can a meltdown attack also violate data integrity of other processes or is it just violating data secrecy?

Question: Can a meltdown attack also violate data integrity of other processes by obtaining different passwords or is it just violating data secrecy by reading data it is unauthorized to do?
Answer: Meltdown does not directly impact integrity, but it totally violates confidentiality. Whether or not the violation of confidentiality is sufficient to also violate integrity (e.g. read root password, become root, and load malicious kernel module) depends entirely on your system.
In other words, Meltdown on its own is exclusively a read vulnerability, not a write vulnerability.
Answer: Meltdown is an attack that allows overcoming memory isolation completely by providing a simple way for any user process to read the entire kernel memory of the machine. Attacker can get password, private keys and valuable information. You can access the research paper here.


Expired Windows Account Password

Question: I need to programatically change my windows admin password without using the login screen.
Essentially we deployed 50+ laptops across our business.
We setup 1 user account and 1 admin account (same password) on each laptop, they're not added to domain etc.  They aren't connected to our network in anyway, we also installed some remote software to control them over the internet.
Essentially, the remote software stopped working yesterday, the only way I can get into the laptop is via some C# program which is running on the laptops under the "user account" credentials.
I did manage to push out a script which would have allowed me access again, but the admin account I setup months ago has expired so I no way to do anything programatically.  If I logged in via the home screen, i could reset the password but this isn't an option. So i need a way to change the password, without the windows login prompt, via the user account, in command line / powershell.
I know the existing admin password, but is there a way to trigger this change from within the user account:
For example:  CHANGEPW.exe -account admin -oldpw pass -newpw passnw
Answer: This link will help you:
change-your-own-expired-password-when-you-cant-login-to-rdp
It's not exactly what you need, the powershell script interactively asks for username, old password, new password. But it can be easily modified to your needs. Also the C++ function used under the hood is mentioned, in case you want to go that way instead of powershell script.

Expired Windows Account Password


Qt Charts and Data Visualization widgets

Question: I have installed Qt 5.7 in order to try Qt Charts and Qt Data Visualization but I cannot find new widgets neither in Qt Designer nor in Qt Creator. Any suggestions what should I do so new widgets appear in designer?
Comment: AFAIK those for commercial Qt license only. Unsure why it is not explicit.
Comment: Not anymore - since version 5.7 that's why I am interested in those libraries now
Comment: Did you include appropriate header? Take a look at docs and examples - `https://doc-snapshots.qt.io/qtcharts/`
Comment: Of course I did. Answer is below
Answer: I was having exactly the same problem today. It looks like the QT Designer plugins of QT Charts are not part of the package by default. I ended up downloading the designer plugin sources from github https://github.com/qtproject/qtcharts/tree/5.7/plugins/designer
This consists of just 5 files.
You should then be able to open the designer.pro project in Qt Creator and compile it. Place the resulting library in your designer plugin directory. This will make the QChartsView widget appear in the Qt Designer.
Comment: Note that you may have to copy QtCharts.dll into the bin folder of QtCreator or the compiled plugin will fail to load.
Answer: Just elaborating on Holger's answer for ubuntu, compile, in terminal using qmake and make (doesn't work in qt creator - you need qt chart development package installed, which I believe is not available at this point in time), the designer.pro file in /opt/Qt/5.7/Src/qtcharts/plugins/designer directory then, copy and paste the shared library into /opt/Qt/Tools/QtCreator/lib/Qt/plugins/designer directory, where /opt/Qt is the directory in which Qt is installed.
Comment: genius, after hours of searching through the internet, I finally found your answer. Holger's answer doesn't include the path to copy shared library to
Answer: I would like to add this as a comment to the accepted post:
If you are using python to build your project and process the .ui files with pyuic5 it might be the case that pyuic5 leaves you with an error message stating that QtChart.QChartview could not be found. This is the workaround:
Go to the site-packages/PyQt5/uic/widget-plugins directory, it should look something like this:
/widget-plugins/
  __pycache__/
  qaxcontainer.py
  qscintilla.py
  qtcharts.py  <- create this file by copying qtquickwidgets.py and renaming
  qtprintsupport.py
  qtquickwidgets.py
  qtwebkit.py

qtcharts.py looks like this (you have to edit the file):
# copyright information

pluginType = MODULE

def moduleInformation():
    return "PyQt5.QtChart", ("QChartView", )

Answer: I also encountered this problem today, but Holger's way didn't work on my situation. After consulting other people via internet, I finally fixed it. And my solution is quiet simple, I just open the Maintenance Tool and choose add components, select Qt Charts and Qt Data Visualization, and click next, and then it works. This problem happens because by default Qt Charts is not selected while installing Qt, so we should add this component manually.
But I also should mention that maybe this way just work on Qt which was installed by Qt Online Installer, and if you installed Qt via offline Installer, maybe you should reinstall it.


epstopdf conversion problem

Question: I'm trying to compile a LaTeX document with eps image files in TexStudio and I'm getting the  error that ... eps to pdf file not found. I tried to put the command \epstopdfsetup{outdir=./} into my LaTeX preamble, but it is not working.
Comment: [Welcome to TeX.SX!](http://meta.tex.stackexchange.com/q/1436) Please add a [minimal working example (MWE)](http://meta.tex.stackexchange.com/q/228) that illustrates your problem. It will be much easier for us to reproduce your situation and find out what the issue is when we see compilable code, starting with `\documentclass{...}` and ending with `\end{document}`.
Answer: The epstopdfconversion package needs pdflatex to be called with the option -shell-escape. You should try to edit your settings (the PdfLatex tab in the configuration window) and add the following option. It should look like
pdflatex -interaction=nonstopmode -shell-escape %.tex

Hopefully it will work properly with this. However, I think you won't get this problem if you simply use the epstopdf package instead.
Answer: I have found that there are a number of different problems which can lead to this error message in TeXstudio. Here are a list of checks you can make:

As MBR says, check you have
pdflatex -interaction=nonstopmode -shell-escape %.tex
added to your PdfLaTeX command. Go to 'Options -> Configure TeXstudio... -> Commands' to enter this.
You may also need to add -enable-write18 to the same command (works with and without this enabled for me).
Make sure your eps file name doesn't have an underscore in it!
Check that TeXstudio is looking for PdfLaTeX in the correct directory. You can check this by going 'Help -> Check LaTeX Installation'. The top lines of the generated 'System Report.txt' should read something like:

`
where pdflatex:

PDFLATEX: pdflatex -version
MiKTeX-pdfTeX 2.9.4487 (1.40.12) (MiKTeX 2.9)
Copyright (C) 1982 D. E. Knuth, (C) 1996-2006 Han The Thanh
TeX is a trademark of the American Mathematical Society.

if it doesn't give the MiKTeX information, TeXstudio isn't looking in the right directory. You can either set the path explicitly in the PdfLaTeX command, something like:
"C:\Program Files (x86)\MiKTeX 2.9\miktex\bin\pdflatex.exe" -synctex=1 -interaction=nonstopmode -shell-escape %.tex

Or, under the 'Build' tab in the configuration window, set an additional search path to tell it which folder to look in:
e.g. C:\Program Files (x86)\MiKTeX 2.9\miktex\bin

If you are using the graphicx package with a separate \graphicspath defined, e.g.
\graphicspath{{./figures}}

you may want to keep the \epstopdfsetup{outdir=./figures} command so that
    the output eps-converted-to-pdf files are saved to the same path.

Lastly, some people suggest to not use the .eps extension in the \includegraphics command,
i.e. \includegraphics{figurename} instead of \includegraphics{figurename.eps}

however I've found (with all the other checks, 1-5 made) that it can accept the filename with or without the extension.

epstopdf conversion problem


How to Get value from Infragistics combo

Question: I am using Infragistics igCombo in my web form. I am using ASP.NET MVC 3 as a server side technology. I can easily bind data but can't get the value which user selects and sends to the server. I want to know how to get values from combo using server side API or using JavaScript API of Infragistics. Any other solution which is not provided by Infragistics will be acceptable.
Answer: For the client side, you can use code similar to the following:
<code>value = igcmbo_getComboById(m_ComboId).getValue();
</code>
where m_ComboId is a javascript variable created on the server-side containing the control's ID:
<code>"m_ComboId = '" + Combo.ID + "'"
</code>
For server-side access of the value, use the DataValue property of the combo.


Asp.Net Roles without Roles Provider not working?

Question: Hallo,
i have created a web site with Asp.Net by using Sql Membership Provider, sitemap and security trimming enabled.
Based on these i have set web.config files into directories for allowing or not the users  access according to their roles.
After some time i removed the MembershipProvider and i creted by hand the "standard" login procedure which cretaed a ticket and a authentication cookie and sets the GenericPrincipal into the Application_AuthenticateRequest.
The problem after these changes is that althought the sitemap displays the right pages for each different user according to his roles, when i click on this page the system redirects me to the "default.aspx" page such as the user is not allowed to enter that page!
It is strange that the sitemap and security trimming is working BUT actually i cannot enter the pages!!!!!
Answer: You can add users and roles with IIS management tool. This way you can avoid any typing error.


People blocked from asking questions should be blocked from posting discussions

Question: People are abusing public discussions to ask for help. Not only they are abusing the site and evading restrictions, they are also wasting time of people in collectives. They post non-discussion topics which often should be questions. These "discussion topics" are plagued by the same quality issues that their questions on main had, for which they received the automatic ban. The system should not allow them to evade restrictions by posting their questions as discussions.
Comment: Feature request: get rid of discussions (until properly fixed). By properly fixed, I mean red flag automations, syncing with question bans, moderator tooling, rate limiting, and an API (for bots). Did I miss anything (probably yes)?
Comment: I am only sorry that I cannot upvote this at least a hundred times.
Comment: @PeterMortensen that would imply adding review queues for discussions
Comment: @Fastnlight: Applying the *'very low quality'* filter (used to move questions into some of the review queues) to discussion posts, perhaps?.
Answer: This change has been made. Users banned from asking questions will not be able to create new posts in Discussions.


General theory of relativity questions

Question: I do not understand how this theory (the theory of general relativity) would work because gravity is what makes things heavy and weight is what bends things. All of the proof makes it hard to question strongly though (with light bending and all) so simply put my question is how does the earth, sun and everything else "bend" space without gravity to pull it down into space? And if this is so  how does the earth's bending of space attract us to the earth?
Comment: Stop thinking of the trampoline analogy. Nothing is "pulling" the earth down. The presence of matter is what sources spacetime curvature, and any test particle moving through space follows paths determined by the curvature (namely, the path of least "distance," defined in a reasonable sense). The trampoline analogy is just there for a visually intuitive explanation, and should not be taken literally.
Comment: What kind of explanation are you looking for? Did you ask "how" Newtonian gravity worked, or did you just accept that we observe it to obey an inverse square law? Learning GR requires learning some new math in order to understand what "curved spacetime" means.
Comment: Then how does the sun "bend" space?
Comment: Gravity is caused by the "bending" of time, not space. We move forward in time, but since time is "bent" (dilated), this movement appears as falling. The reason time is "bent" by energy is the fact that time and energy are two sides of the same existence (Fourier conjugates). So more energy translates to less (slower) time and causes things to fall there.
Comment: @BobKnighton The trampoline analogy is perfectly valid, but commonly misunderstood. It is a plot of time dilation in the reduced (by 1) number of dimensions. In other words, this analogy represents the curvature of time that causes gravity. Despite a common misconception, gravity is not caused by the curvature of space: "*in space-time the curvature of space has nothing to do with gravity (the 'curvature of time', one could say)*" - https://en.wikipedia.org/wiki/Ellis_wormhole - You can use the Schwarzschild metric to plot a mathematically correct trampoline chart of gravitational potential.
Answer: Einstein's equation in GR describe quantitatively how space-time metric behaves, depending on the stress–energy tensor. This is how ("how much", if you wish). Nevertheless, I think that by "how" you meant "by which means", so it is indeed a "why". This one is easy to answer: no one knows. There is no proven physics theory going further that GR in understanding how gravity works. The most known "works in progress" are string theory (or its children) and quantum loop gravity (there exist others, less popular), but they haven't yet proved to hold any truth.
So, for the moment, the only answer is: "nobody knows".
Comment: We do know why. Time and energy are Fourier conjugates (the "opposite sides" of the same), so "more" (concentrated) energy translates to "less" (slower) time that causes gravity.
Comment: @safesphere The stress–energy tensor is the conserved Noether current associated with spacetime translations when the Hamiltonian doesn't depend on them. I don't think that you can use that to state "more energy translates to less  time that causes gravity". By the way, curvature still exists outside of massive objects, in vacuum.
Comment: Sure I can, but otherwise you are correct. Things fall down releasing energy, so energy is not conserved in gravity, unless we invent a "renormaluzation" component and call it "potential energy". However in reality there is only curved spacetime, nothing else. The Noether relation that you mentioned is exactly the same time/energy symmetry in my comment. We are talking about the same thing. Same for gravity in vacuum - you can see it as cased by the energy of the "field", if you prefer, or by the energy of matter as the original source. There is no contradiction.

General theory of relativity questions


Unsure which data to use for ANOVA test

Question: I have determined that a one-way ANOVA test of variances will work best for my data. However, the nature of my data makes me very concerned about making any claims based on significance or not.
My research project is examining survey data (25 questions) on a likert-scale taken over a 3 year period, split among 5 subdomains (however, one domain has as little as one corresponding question, another has 8, etc.). I am testing whether or not there is a difference between when respondents took the test at baseline and throughout (7 total time categories, or every 6 months) for EACH SUBDOMAIN.
I am having some trouble saying exactly what the problem is, but simply put I do not know whether I should (a) put every individual response into a bin,count the total responses, and average them at each time slot for each subdomain, or (b) average each individual response, count the number of tests taken during that time slow as an "n", and then take the means and Std.Devs of those for the ANOVA test.
Here are my two tables that I've come up with:
Table for Individual Responses

Table for Grouped Responses

The main difference is that the individual responses has much larger n values. This has direct implications on if my study is significant or not. Here is an example:
and here is why this is important... because it directly matters on whether my data is significant or not:
Results for Individual Responses:

Results for Grouped Responses:

My intuition is telling me I should use option (B) because option A just seems to be artificially increasing the sample size, but again that is the raw data from my responses and I don't want to make any mistakes with this...
If anyone has any good ideas about how to treat this, that would be wonderful news!!! I also think I messed up anyway since I'm using Likert data and I do not know what test is appropriate to use for comparing means of likert data.
Answer: In option A you are treating each response that an individual gave as though it came from an independent individual, so yes, your intuition is correct that this is wrong. However, option B may be problematic as well. If I am reading your description correctly, the same individuals responded at multiple time points. If this is current, then that needs to be accounted for as well. However, the changing sample size implies that you have missing data. You would need to use a mixed-effect GLM model to properly address this if my assumption about your data is correct.

Unsure which data to use for ANOVA test


In the US, if the Fed stops hiking the Fed Fund Rate, how does it affect inflation rate?

Question: I know if the Fed continues to increase the Fed Fund Rate, inflation eventually goes down. But what if the Fed stops hiking the current Fed Fund Rate, how does it affect current inflation rate if the current Fed Fund Rate stays constant? In other words, does prolonging the current Fed Fund Rate (no change for a longer period of time) have an increasing, constant, or decreasing effect on the current inflation rate?
Answer: Ceteris paribus, if interest rate is kept constant also inflation will be kept constant. The relationship between Fed's interest rate and inflation is typically modeled as (see Romer Advanced Macroeconomics pp 520-523):
$$\pi_t = \alpha + \beta \Delta i_{Fed} +\gamma \pi_t^C + \epsilon_t$$
If everything else stays constant, and Fed's federal funds rate (Fed's interest rate) also does  not change, then inflation stays as it was given the value of $\alpha$, people's inflation expectations $\pi_t^C$  and exogenous shocks and there is no further change in inflation unless something changes. There are more ways how to model this relationship, the model above is one of the simplest ones, but regardless of that, in generally used models no change in interest rate will produce no change in inflation rate if nothing else changes (e.g. previous exogenous shocks to inflation dying down etc).
However, note in real life things are not being constant so inflation could come down on its own even if interest rate is kept constant. For example in terms of models above $\pi^C$ could drop or there could be negative exogenous shocks $\epsilon_t$ or even parameters $\alpha$ and $\gamma$ could have changed, but the drop in inflation would not be result of interest rates being kept same it would be result of it 'naturally' dying out due to adjustment in other factors.
Comment: @HelloDarkWorld $\pi$ is the inflation rate, $i$ Fed's interest rate, $\pi^C$ is expected inflation of consumers or people $\epsilon$ are some random shocks and $\alpha$, $\beta$ and $\gamma$ are just some parameters. Exogenous shock such as for example supply chain issues or shocks to GDP in general (e.g. sudden recession or strong expansion)
Comment: Would you please define what each of the factors represent in Romer's Advanced Macroeconomics? Generally, what are some exogenous shocks that can increase or decrease inflation rates? Thanks.
Answer: Summary:

If Fed makes the mistake of sticking to an overly restrictive rate for an extended period of time, inflation will go below the target and the economy will be hurt more than necessary.
If the mistake was to stick to a rate that was insufficiently restrictive, inflation may stay above target or even rise and ultimately also hurt the economy.

If the Fed sets a policy rate, it's because it thinks that rate is appropriate to have medium-term inflation close to the target.  Specifically, if inflation is above target, the appropriate policy rate is restrictive; that is, it's set at a level high enough to bring inflation down in the medium term, according to the Fed's judgement.
Now, if, subsequently, inflation is indeed coming down as expected, a new, lower policy rate may be appropriate. But if the Fed still maintains the rate at its previous levels, its policy is overly restrictive and would hurt the economy more than needed to bring inflation back to target, and inflation would undershoot the target. Conversely, if the Fed has set the terminal rate not sufficiently restrictive, this would allow second-round effects to materialize, and inflation would stay high or increase even further, also ultimately hurting the economy. Because monetary policy affects the economy and inflation with a lag, judgments have to be made ahead of time. Monetary policy is a tricky business, and mistakes can be made.
Formally: It is often assumed that central banks set policy according to a so-called Taylor rule (of which there are now many varieties):
$$
i_t = \pi_t + r_t^* + a_\pi  ( \pi_t - \pi_t^* )  + a_y ( y_t - \bar y_t )
$$
where $i$ is the policy rate, $\pi$ the inflation rate, $\pi^*$ the inflation target rate, $y_t-\bar{y}_t$ is the output gap (measuring how far GDP is from potential GDP), and the $a$s are coefficients. Importantly, $r^*$ is the neutral real interest rate - at this rate, inflation remains at its target rate if inflation is at target and GDP is at potential, and ignoring outside factors.
If the actual policy rate is significantly different from $i$, the Fed makes a mistake (provided that it's a good rule). Mistakes may occur because the Fed misjudges or miscalculates some of the right-hand side elements that are not directly observed, such as $r^*$ or potential output $\bar{y}$.


Pi 5 vs. Pi 4 and External HDD

Question: If I lsusb I see my portable hard drives.  If I fdisk -l I do not.  More concerning, when I listen closely to the drives that are plugged in, I hear them cycling every few seconds.  I have a 5 amp power supply and both drives are USB-3.1.  I tried with just one drive and it's the same thing.  The pi is fully up to date.  What can I do here?
When I run fdisk -l it hangs after the SD card, where I'd expect to see sda and sdb
Both external hard disks behave the same when plugged in by themselves.  A thumb drive works as expected.  Is the USB3.1 ports really rated appropriately?
Tested both external HDD simultaneously on a Pi4 8GB and it works correctly.  What the heck?  Need guidance.
Comment: Still sounds like a power problem.
Answer: You shouldn't be using fdisk to "see" your portable hard drives. fdisk is a tool for manipulating disk partition tables. Use lsblk --fs.

Pi 5 vs. Pi 4 and External HDD


FOSS State Diagram Program

Question: I am looking for a program to build state diagrams/machines in, the simpler the program the better.
Any Suggestions?
Answer: If you're trying to just draw pictures,take a look at Dia, Umbrello or UMLet. If you also want to do things like code generation, look closer into this comprehensive list.
Answer: QM (http://www.state-machine.com/qm) is a simple, free, cross-platform, graphical UML modeling tool for designing and implementing real-time embedded applications based on state machines. QM supports nested states, entry/exit actions, actions on transitions, internal transitions, and choice segments. The generated C or C++ code is human readable. QM allows you to mix your own code with the synthesized code and use the tool to generate as much or as little of the overall code as you see fit.

FOSS State Diagram Program


Why can a ball tossed up object free fall upwards?

Question: I've found many websites that say that a ball tossed upward would be free falling upwards, but none of them say why. If the definition of free fall is an object that is falling while only under the force of gravity alone, then the force you are exerting on the ball when you toss it up rules it out from free fall, right?
Comment: The moment the ball leaves your hand, your hand stops exerting force on it. So the only force left is its weight.
Comment: So when you throw an object, it doesn't continue to carry with it any force from being thrown? Thanks
Answer: In common parlance, saying that an object is "falling" implies that the object's velocity is in the direction of the ground.  However, the phrase free fall is defined as applying to an object which has no forces acting on it except for gravity, a definition that has nothing to do with velocity.
If you throw a ball 3 meters above your head, your hand stops applying a force to the ball at the moment the ball leaves your hand.  At that moment, there are no forces acting on the ball any more except for gravity, so it meets the definition of being in "free fall", even though at that point the direction of the ball's velocity is away from the Earth, and hence the ball isn't "falling" as that word is used in common parlance.
To answer your follow-up question, no, the ball doesn't "carry force with it" after it leaves your hand.  After the ball leaves your hand, the ball has kinetic energy and momentum and an upward velocity due to the force that had been on the ball, but there is no force acting on the ball any more.
Answer:
then the force you are exerting on the ball when you toss it up rules it out from free fall, right?

Your hand has to be in contact with the ball to exert a force on it. As soon as you let go, you can't provide a force to the ball anymore.
Since you can no longer provide a force to the ball, the only force left on it is gravity, so it's in free-fall. The net acceleration on the ball is now towards the ground. (There are some other forces due to friction present, like drag, but we'll ignore those and pretend the ball is falling in a vacuum.)
The ball's velocity is still upwards for a while, but under the relentless acceleration of gravity, it will slow until it reaches zero at the top of its arc, and then head towards the ground.
The word "fall" in "free-fall" is something of a misnomer. An object need not be moving towards the ground to be in free fall, only accelerating towards the ground under the influence of gravity. For example, these are all in free-fall:

A bullet fired straight upwards
A satellite in stationary orbit
A cannonball shot from a cannon
Answer: Yes because when you put force when the object is falling it is no longer free falling. Free falling is when you have a object with nothing acting upon it making it free fall.
Comment: As it's currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer).