Existence of independent and identically distributed random variables.

Question: I often see the sentence "let $X_1, X_2, \ldots$ be a sequence of i.i.d. random variables with a certain distribution". But given a random variable $X$ on a probability space $\Omega$, how do I know that there is a sequence of INDEPENDENT random variables of the same distribution on $\Omega$?
Comment: I have also to mention than the sequence is defined on a new probability space, and not on the original space $\Omega$ where $X$ is defined. This is not a real issue, because of the philosophy of probability theory : this is the laws of random variables which are of interest, rather than the probability space on which they are defined.
Comment: This is Kolmogorov's consistency theorem. See for example Varadhan's _Probability Theory_ page 41 for a nice explanation. It's available on Google books.
Comment: @Stefan Hansen : To apply Kolmogorov's consistency theorem, you need the law to be a probability measure on a Polish space. Nevertheless, this result holds in full generality, and can be seen as a particular case of Ionescu-Tulcea's theorem.
Answer: The easiest way to show the existence in our case is to construct such a probability space. The intuition is that it is easy to define the joint probability measure on some "simple" sets using the iid property and then one leverages the celebrated Caratheodory extension theorem.
More precisely, let $(E,\mathcal E)$ be the measurable space where our random variables are supposed to take values and let $\mu$ be a probability measure on $(E,\mathcal E)$ representing the distribution of such random variables. Define $\Omega = E^{\mathbb N_0}$ to be the space of countable trajctories over $E$ and let $\mathcal F$ be its product $\sigma$-algebra. Define the probability measure $\mathsf P$ on $(\Omega,\mathcal F)$ just based on the independence, i.e. for any $A_0,\dots,A_N\in \mathcal E$ we put
$$
  \mathsf P(X_0\in A_0,\dots,X_n\in A_n):=\mu(A_0)\times \dots\times \mu(A_n).
$$
So far the measure $\mathsf P$ is only defined on the collection $\mathcal A$ of measurable rectangles, i.e. subset of $\Omega$ of the form $A_0\times\dots\times A_n\times \Omega\times\Omega\times\dots$ where $A_i\in \mathcal E$. Finite unions of elements of $\mathcal A$ form the algebra, say $\mathcal B$. Clearly, $\mathsf P$ is a finite pre-measure on $\mathcal B$ and hence by the Caratheodory extension theorem we obtain the unique measure $\mathsf P$ on $\mathcal F = \sigma(\mathcal B)$.
As Ahriman has pointed out, if you are given a random variable $X:\Omega\to E$ it may not be possible to construct the whole sequence on $\Omega$ as the latter may be quite a poor space, so you would have to go for a richer space. For example, $E$ always can be considered as a sample space for the distribution over it, by taking $\mathrm id_E$ being a random variable. But in case $E = \{a,b\}$ and you have $\mu(a) = 0.4$ and $\mu(b) = 0.6$ it is only possible to construct one and only one random variable defined on $E$ which has $\mu$ as a distribution.
Comment: +1. Nice answer.
Comment: How does one show that the disjoint union property of the pre-measure is fulfilled?
Comment: I think $A_0\times\dots\times A_n\times \Omega\times\Omega\times\dots$ should instead be $A_0\times\dots\times A_n\times E\times E\times\dots$.
Answer: A very concrete approach to construct a sequence of iid random variables with distribution $F$ (say, $F$ is the desired cumulative distribution function) is to proceed as follows.
It is enough to construct a sequence of iid uniform $[0,1]$ random variables $(X_i)_{i\ge 1}$, because then $(F^{\leftarrow}(X_i) )_{i\ge 1}$ is a sequence of iid random variables with common distribution $F$. Here, $F^\leftarrow$ is the generalized inverse of $F$.
So let's concretely construct a sequence of iid uniform $[0,1]$ random variable.
Take $\Omega = [0,1]$ and $\mathbf P$ be the Lebesgue measure on $\Omega$; there we naturally have a single measurable function (or random variable) $U:\Omega\to\mathbb R$ defined by $U(x)=x$ for any $x\in \Omega$.
Now view $U$ as a random variable, and write its decomposition in base $2$ as
$$U = \sum_{k=1}^{+\infty} B_k/2^k.$$
Exercise: show that each $(B_k)_{k\ge 1}$ is a sequence of iid Bernoulli$(1/2)$ random variables on $\Omega$.
Then we may split the set of positive integers into countably many infinite subsets; for instance, let $(p_n)_{n\ge 1}$ be the sequence of prime numbers and fr any $n\ge 1$, let $I_n = \{ p_n^j, j=1,2,3,4,... \}$. Each $I_n$ is infinite and $I_n\cap I_m = \emptyset$ for any $n\ne m$. From these sets $I_n$, for any $n$ define
$$X_n = \sum_{k=1}^\infty B_{\varphi_n(k)}/2^k$$
where $\varphi_n$ is a bijection $\mathbb N_{\ge 1}\to I_n$ (that is, the countable set $I_n$ can be written as $I_n = \{\varphi(1), \varphi(2),\varphi(3), ...\}$. Because the sets $I_n$ are disjoint, a Bernoulli random variable $B_k$ is used only in one of the $X_n$'s, so we can prove the following to conclude:
Exercise 2: show that each $X_n$ has the uniform distribution on $[0,1]$, and that the sequence $(X_1,...,x_n,...,)$ is iid.
Hence $\Omega=[0,1]$ equipped with the Lebesgue measure is rich enough to construct a sequence of iid random variables with distribution $F$.
Answer: Since they're i.i.d., you can just use a product measure on a product space $\Omega\times\Omega\times\Omega\times\cdots$.
And for many purposes, you can take $\Omega=\mathbb R$ and let the measurable subsets of $\Omega$ be the Borel sets.
Comment: @cantorhead : I wasn't suggesting you wouldn't need a product of measure spaces; rather I was saying you could take $\Omega = \mathbb R$ and use the product of copies of $\Omega.$ But here was the question: "But given a random variable $X$ on a probability space $\Omega$, how do I know that there is a sequence of INDEPENDENT random variables of the same distribution on $\Omega.$?" If $X_1$ has $\Omega$ as its domain, then in some cases there is no infinite i.i.d. sequence, and in some cases no finite i.i.d. sequence of length more than $1$, on the same domain $\Omega$ and$\,\ldots\qquad$
Comment: $\ldots\,$ with each member of the sequence having that same probability distribution. It's easy to find counterexamples with some discrete distributions. But the product of countably many copies of $\Omega$ does it. $\qquad$
Comment: @cantorhead : You said "I often see the sentence 'let $X_1, X_2, \ldots$ be a sequence of i.i.d. random variables with a certain distribution' ". Nothing in that presupposes that if $X_1$ has a certain probability space as its domain, then there is such an i.i.d. sequence on the SAME domain. It only presupposes that there is SOME domain on which such an i.i.d. sequence exists.
Comment: Let us [continue this discussion in chat](http://chat.stackexchange.com/rooms/50241/discussion-between-cantorhead-and-michael-hardy).
Comment: I've moved my comments to a new question: http://math.stackexchange.com/q/2063785/118481. Thank you for the input, it helped in making the new question more precise.


How are the soul and the body related to each other according to the RCC?

Question: Humans have a mind (or soul) and body, but they are not separately divided substances (as Descartes would suggest). So one could say we have a soul and body. But according to the Roman Catholic Church, how are they constructed/connected philosophically together to get one person. Is it allowed to say that the soul is in the body?
Answer: The Council of Vienne (1311-1312), under the authority of Clement V, defined the dogma that the soul is the form of the human body (Denzinger 481):

Moreover, with the approval of the said council, we reject as erroneous and contrary to the truth of the catholic faith every doctrine or proposition rashly asserting that the substance of the rational or intellectual soul is not of itself and essentially the form of the human body, or casting doubt on this matter. In order that all may know the truth of the faith in its purity and all error may be excluded, we define that anyone who presumes henceforth to assert defend or hold stubbornly that the rational or intellectual soul is not the form of the human body of itself and essentially, is to be considered a heretic.

"Form" is "the actualizing principle that makes a thing to be what it is." Thus, a body without the substantial form of a human being (a soul) is a corpse.
The Oxford English Dictionary defines form as:

In the Scholastic philosophy: The essential determinant principle of a thing; that which makes anything (matter) a determinate species or kind of being; the essential creative quality.
This use of form (Aristotle's μορϕή or εἶδος) and matter (ὕλη) is a metaphorical extension of their popular use. In ordinary speech, a portion of matter, stuff, or material, becomes a 'thing' by virtue of having a particular 'form' or shape; by altering the form, the matter remaining unchanged, we make a new 'thing'. This language, primarily applied only to objects of sense, was in philosophical use extended to objects of thought: every 'thing' or entity was viewed as consisting of two elements, its form by virtue of which it was different from, and its matter which it had in common with, others.

Read St. Thomas Aquina's short work On the Principles of Nature (De principiis naturæ) for more information on matter and form (hylemorphism).
St. Thomas Aquinas also addresses the question of the union of a human's intellectual soul with the human's body in Summa Theologica I q. 76.


Is it possible to reset a Normal Mode playthrough?

Question: So, I accidentally left my game running in friends only overnight. Then, a rather irritating friend of mine came in with his level 35 Commando and finished from A Dam Fine Rescue to Rising Action,leaving me underleveled, gear-wise. Is this fixable or am I up some sort of creek without a bladed Jakobs sniper rifle?
Comment: You may be able to join another friend's game who hasn't progressed as far as you.  You won't get the XP from the missions you've already "completed", but that might be a good thing, since your friend will catch up a bit in level while playing with you.
Comment: not without using an editor, and if you are going to do that, may as well just set your level and your gear level to something higher...
Comment: "up some sort of creek without a bladed Jakobs sniper rifle" lol. You could always restart the game entirely. A Dam Fine Rescue isn't that far into the game IIRC.
Comment: If you are playing on PC, BL2 keeps a backup of your current save that tends to be a bit older.  It may be before your friend joined.  I'm not sure how often the current save gets written to the backup though.
Answer: I suggest grinding nonstop to get on his league. No, you cannot restart without an editor, as far as I know.


Impulse as the time derivative of force

Question: Momentum is the time derivative of force. $F = \frac{dp}{dt}$.
But isn't impulse $J=Ft$, $F=\frac{J}{t}$?
Can impulse be the  time derivative of force too, or is it just defined as an integral?
Answer: Usually, the term impulse means the difference in momentum:
$$\vec J=\Delta \vec p$$
Force is the time derivative of momentum:
$$\vec F=\frac{d\vec p}{dt} \Leftrightarrow d\vec p=\vec F \;dt$$
In a scenario where you consider a finite amount of transfered momentum, or when $d\vec p\approx \Delta \vec p$, then you can rewrite as:
$$\vec J=\vec F \;\Delta t$$
$\Delta t$ is often just denoted $t$ to mean the time duration. So there you have it. In the case of non-constant force, you would how to add up all the (maybe infinitely many) small impulses, which gives the usual integral version of the formula:
$$\vec J=\vec {J_1}+\vec {J_2}+\vec {J_3}+\cdots=\vec {F_1} \;\Delta t_1+\vec {F_2}\;\Delta t_2+\vec {F_3} \;\Delta t_3+\cdots\quad\Leftrightarrow\\
\vec J=\int \vec F \;d t$$
Impulse and momentum are closely related, but not exactly the same. Rather, one is the difference in the other.
Answer: You have written wrong formula for impulse.it is not just time there instead it is change in time(delta t).
So, now if you look over the final formula that is F=J/delta t(not just t) it is same as F=dp/dt as, J =dp.
So you got nothing new like you observed in your question .
You got same equation.impulse is just a fancy word for change in momentum(generally big changes not delta p) as it is used often.
Comment: Your formula should not be written that way. The correct formula is $J=\int_{t_1}^{t_2} F.dt$

Impulse as the time derivative of force


How to view URL of GetFeatureInfo request in QGIS?

Question: I have a WMS layer in QGIS. I am using the Identify Features tool to perform a GetFeatureInfo request. It retrieves the expected attribute data in the Identify Results panel. However I would like to see the URL of the request too. How can I achieve that?
Comment: What is your WMS actually? I guess you can figure it out by reading the API documentation?
Comment: possible duplicate of https://gis.stackexchange.com/questions/282662/easy-way-to-see-the-requests-qgis-makes-to-a-remote-server
Answer: Simple
Right click your feature in your "Identify Results" right pane and select "Copy GetFeatureInfo requests URL":

Advanced
You can also go with PyQGIS.
For example, with a single layer loaded from a WMS, in the Python console:
layer = iface.activeLayer()
provider = layer.dataProvider()
provider.dataSourceUri()

This will normally show the URI of the data source provider for your layer.
If you want to have access to more information, I can suggest your to have a look both here at the documentation for the qgis.core.QgsRasterDataProvider instance and here.
You can especially try to use the identify method which is probably the one used by the GUI:
https://qgis.org/pyqgis/3.2/core/Raster/QgsRasterDataProvider.html#qgis.core.QgsRasterDataProvider.identify
And which help says:
identify(...) method of qgis._core.QgsRasterDataProvider instance
    identify(self, point: QgsPointXY, format: QgsRaster.IdentifyFormat,
             boundingBox: QgsRectangle = QgsRectangle(), width: int = 0,
             height: int = 0, dpi: int = 96) -> QgsRasterIdentifyResult
    Identify raster value(s) found on the point position. The context
    parameters extent, width and height are important to identify
    on the same zoom level as a displayed map and to do effective
    caching (WCS). If context params are not specified the highest
    resolution is used. capabilities() may be used to test if format
    is supported by provider. Values are set to 'no data' or empty string
    if point is outside data source extent.

Beware of the CRS of your WMS layer if you use that.
But in my case, as the link to the other question also explain, I end up with an empty list:
>>> P = QgsPointXY(783093, 5995473)
>>> rect = QgsRectangle(2696385,4098767,2696402,4098786)
>>> feat = ident.identify(P, QgsRaster.IdentifyFormatValue,
                          boundingBox=rect, height=2, width=2)
>>> feat.results()
{}

Note
I'm using QGIS 3.12.2-București
with Python '3.6.9 (default, Apr 18 2020, 01:56:04) \n[GCC 8.4.0]'
Answer: A nice way to see all remote requests such as GetFeatureInfo is to use the "QGIS Network Logger", which is available in all QGIS installations by default since since QGIS Pi / 3.14, by just pressing F12 . It was first available as a plugin since QGIS 3.6 https://plugins.qgis.org/plugins/qgisnetworklogger/ as shown below:

You can then leave the logger window open and add your WMS layer, query it etc, and see the exact urls generated.  You can also right-click on the url and have it open in a new browser tab.

There is also an alternative method to see all requests, through software named 'Fiddler', but I recommend the above logger method instead.  (more about the alternative Fiddler way at https://github.com/mapserver/mapserver/wiki/Get-the-Raw-WMS-Request-Generated-by-QGIS )


how to setup a router to route everything through a content filter that does whitelisting

Question: Consider a router with adsl connection to internet, 3 ethernet ports (eth1 to eth3) and wifi.
Consider there is a linux machine (that is to do content filtering (whitelisting - allow only specific ips or ip/tcp combinations or urls (the whitelist) and block everything else)) connected to eth1 on router, but never connects to the internet. Can this machine be prevented access to adsl internet connection permanently. How?
Consider there may be two other machines on eth2 and eth3 and probably many more thru wifi.
Can the router be setup to relay all the traffic (raw physical layer packets) from eth2, eth3, and all wifi connected nodes to eth1 and eth1 would forward allowed packets back to the router and drop rest of them. The router would use the adsl (or eth2 eth3 wifi) for all packets coming from eth1. Similar setup must exist for all packets coming from adsl to eth2, eth3 and wifi (adsl to eth2, eth3 and wifi must first be sent to eth1 and then to the respective devices). How?
Comment: Consider giving details about what you are working with. Vague hypothetical questions lead to vague hypothetical answers. There is no way anyone can know what your router/network is capable of without knowing anything about it. Please [edit] your question with the details of what you are working with.
Answer: Normally, a content filter is set up as a proxy server, which means it makes connections to the internet on behalf of the clients.  In this configuration, it wouldn't be sensible to block its access to the internet or it couldn't function.  Unless you are filtering on the fly more like a firewall, then you can add rules that say that packets originating from the content filter should be dropped.  Also, most domestic and all commercial routers will let you drop packets with a specific IP as source.
If the router in question is a domestic router, then eth1 - eth3 and wifi are all bridged together.  That is, they form the same layer 2 network and there isn't a way normally to treat them as individual ports and apply routing decisions individually.
In this case, you would need to make the default gateway of the network be the content filter.  This will push all traffic from any device connected to the router to the content filter.  You cannot normally do this with a domestic router, but you can disable the DHCP service on the router, and set one up on your content filter.
Then the content filter default gateway would be the router.  Note that packets would be coming in and out of the same interface of the content filter, but this should not be an issue.  If this is a linux box, make sure that /etc/sysctl.conf contains:
net.ipv4.conf.all.send_redirects = 0

This will stop the content filter telling the router to connect directly to local IP addresses if packets arriving on its interface, but destined for other IP address on the same network.  As they will be in your case.
The last part is to make sure that all incoming traffic will go to the content filter.  Most domestic routers will let you add static routes.  If you add a static route for your entire internal network range - for example 192.168.0.0/24 to go to the IP address of your content filter, this will override the routers natural tendency to send packets for devices on a network it is attached to directly to those devices.  Instead, anything incoming will go to the content filter.


Can Bitcoins be duplicated if two private keys share the same public key?

Question: Although statistically impossible, imagine that two different private keys share the same public key. Would that addresses be able to create new Bitcoins?
Let's say that private keys A1 and A2 have the same public key A. I use wallet B to send 1 Bitcoin to A. Both A1's and A2's wallets would show a 1 Bitcoin balance.
Now both A1 and A2 send 1 Bitcoin to B at approximately the same time. Will B now have 2 Bitcoins, or would one of the transactions fail?
Comment: To be exact, in ECC it is completely impossible for two distinct privatekeys to produce the same publickey. However nearly all Bitcoins (i.e. TXOs) are locked either to a script or to an **address** which is a 160-bit hash of a publickey (represented either in compressed or uncompressed form), not the actual publickey, so collision on an address _is_ theoretically possible, albeit much less likely than your brain spontaneously exploding.
Answer: There can only be a single spend of a transaction output, it doesn't matter if there's multiple private keys which correspond to a script. It is functionally the same as one private key signing two transactions, they can't co-exist due to the consensus rules of Bitcoin.
Answer: Since A1 and A2 have the same public key, it means that the network will treat them as one person.


External Hard Drive won't mount. How can I transfer the files?

Question:
I have a Buffalo mini station that I believe has died. It will not mount and will not repair in disk utility. It will not mount in terminal. How can I transfer the files from the dead external hard drive to another external hard drive? Please help before I throw it trough the window. Many thanks
Answer: There are two possibilities.

The disk itself has failed. You now need a high-powered recovery program like Data Rescue, or a service like DriveSavers. Cost is about $100 for the first and $1000 for the second.
The case has a problem. Given that it's a Buffalo case I think this is more likely (their products are rather low quality). Get a new case or a drive dock, open the old case, remove the drive and put it in the new case / dock.


If I am not logged into my company's WIFI, can they view my information? Or am I transmitting?

Question: I was at work using my phone. We have an open WIFI, but I did not use it to go online. I was wondering, can my information be viewed or was I transmitting data even though my phone said I was not connected to their WIFI?
Comment: If I have locks on the apps can work still see my data through wifi? Do locks on apps work?
Comment: Is this an answer?
Comment: This does not really answer the question. If you have a different question, you can ask it by clicking [Ask Question](https://security.stackexchange.com/questions/ask). You can also [add a bounty](https://security.stackexchange.com/help/privileges/set-bounties) to draw more attention to this question once you have enough [reputation](https://security.stackexchange.com/help/whats-reputation). - [From Review](/review/low-quality-posts/104216)
Comment: If you have a new question, please ask it by clicking the [Ask Question](https://security.stackexchange.com/questions/ask) button. Include a link to this question if it helps provide context. - [From Review](/review/low-quality-posts/104216)
Answer: If you are connected to a mobile network instead of your companies wifi they shouldn't be able to view traffic coming from your phone. However, if the phone is a work phone (provided by them) then the statement above may not apply; they could have installed applications designed to monitor employees.
Comment: How would the application be able to monitor traffic? It suggests that the applications are performing MiTM.
Answer: As long as your device is not connected to a WIFI, it should not transmit or receive any data through the WIFI interface.
Answer: There is also another complication regarding Wifi too for example if your phone automatically connects to x SSID. Your phone must broadcast a probe signal for known SSIDs that you have connected which can be logged using airmon (part of Aircrack suite). If I create a fake BBSID using tool such as airbase-ng (Part of the Aircrack suite) which your phone has been probing for you will automatically connect to me thus allowing me to to deal with your way your phone deals with network. Hell, you could even do some pentesting against phone now that your networked to the attacker.
So, you need to ensure Wifi is not probing for known SSIDs or completely disable your Wifi.
As for 3G too link below:
sniffing/recording GSM 3G signals
Theoretically it's possible to monitor 2/3G signals with the correct equipment. I've never seen it happen in person.
If they was doing some of methods above this would have to be in your work contract that you signed otherwise it would be beaching your privacy. Anyways, who's going to spend that amount of time and effort monitoring all that? Unless your working as GCHQ. :p
Answer: If your device is not connected via Wifi, you don't transfer information via Wifi. If it's a company phone, they could monitor what you do, even for apps that never connect to the internet.
If you connect to your mobile provider (3G etc), then it depends. At our office we have bad reception. We bought a device that provides a 3G connection for one specific mobile provider. This device is connected to our network. I have no idea if this traffic is encrypted and safe.
I just asked another question about this:
3G Femtocell at home: can anybody connect, and is all traffic encrypted?
Answer: If you are using your personal cell phone with no Enterprise MDM app installed and no connection to your work WIFI-then short answer: "No"
If it is a work phone and it has an Enterprise MDM app installed, then it is possible they log that data whether you are on company WIFI or using cell. It just depends on how they set things up.
Answer: It depends on what service they use. If they use company router to monitor and restrict the mobile phone activity, they have few chance to know what you are doing.
However, some companies use apps to monitor the phone activities of phones, google and you will find out a lot. See what I got http://ikeymonitor.com or http://www.spy-mobile-phone.com
With these apps installed, the data transmit doesn't require Wifi. They may use cellular or 3G network.


Is there any other way to implement the blockchain synchronization less time consuming?

Question: If we implement another way of synchronizing the blockchain, for example distribute it on several nodes and make groups of nodes handle the whole copy of blockchain instead of single nodes, (in order to reduce the time needed to synchronize the chain), does it make any harm to the integrity of the blockchain?
Comment: It could be, yes, but also would solve the time issue. A divided blockchain (obviously) would have less blocks; resulting in faster synchronization. Am I missing something here?
Comment: The idea you have, seems to me related more to the scalability of the ethereum network than the syncronization process, which is done only if you install a new client. Could that be?
Answer: Most time of the syncronization is spend by verifying the integrity of the blocks. It is a security measure that you can circumvent partially if you start the syncronization with geth --fast
Comment: You are right, yet dividing the blockchain into smaller pieces could also be a solution to the time issue. Obviously less blocks result in less time needed to check them. Am I wrong?
Comment: If you have a free lunch at a chinese restaurant and they bring you small plates you will get as full as if you order an entire peking duck. So the division of blocks does not help, because its the amount of transactions that happened over time that makes the blockchain huge


Augmentation for EEG signal classification using Deep Learning

Question: Augmentation is a technique that we use in deep learning for expanding the training dataset. It includes different ways of modifying an image and adding it to the training dataset. My question is if we are using augmentation for EEG classification and say we generate spectrograms and feed them as images to a CNN can we use Augmentation to increase the training dataset?
Answer:
...if we are using augmentation for EEG classification and say we generate spectrograms and feed them as images to a CNN

If you are approaching this as an image based problem, it could possibly work. There are not enough details about the problem to provide a more accurate answer on this.
In any case, EEG records brain activity typically as a set of signals. Later, each one of those signals would lead to a time-frequency spectrogram representation. This means, one "image" per EEG channel which does not seem very practical from an augmentation point of view.

...can we use Augmentation to increase the training dataset?

A better approach to "augmentation" would be to generate surrogate data via suitable models.
This is closer to "augmentation" but still does not solve all of the problems you might be facing.
Jansen's model (for example) will generate realistic EEG waveforms with similar dynamics but only on a per channel basis (out of the box). If you are interested in replicating an EEG recording as a whole (that is, not only the dynamics of each channel but also their correlations), you would need to couple instances of Jansen's model and at that point you are still left with the question of "which coefficients are supposed to be associated with this task"?
So, if you are interested in creating a classifier that discriminates between "This is most likely an EEG signal rather than an electrode just dangling in the air", augmenting your dataset will work as expected. But if you are interested in creating a classifier that discriminates between "The subject is now more likely day dreaming rather than sleeping", then you need either very complex models or a large amount of data (under a similar condition) to infer some kind of a rule to exploit it later.
Hope this helps.


How to use Firefox in Private mode with only *some* add-ons?

Question: On Chrome browser, you can select which extensions are active in private mode (incognito). How to do the same in Firefox please?  (By default Firefox allows all add-ons in Private mode).
Comment: I don't think you can. I can't see [an open bug for it either](https://bugzilla.mozilla.org/buglist.cgi?quicksearch=private+browsing+add-ons).
Answer: Add-ons
At least through version 63, Firefox lacks a native feature to selectively control which add-ons are allowed in private mode; the enabled/disabled status of each is the same in private mode (although all add-ons are required to comply with the private mode rules regarding data retention).  But there's a workaround to accomplish what you want.
You can have more than one profile, and each profile is independent as far as what add-ons are installed or enabled.

Create a new profile, including just the add-ons you want in private mode.  If you're in Firefox, enter about:profiles in the URL window, and that has an option to create a new one.
Create a shortcut to launch Firefox in private mode using that profile.  The command line would look like:
firefox -private -P "new_profile_name"

Bookmarks and Other Profile Content
As you note in a comment, this still isn't exactly the same as the Chrome feature because Chrome retains other settings and information, like bookmarks, in incognito mode.  So you need a second workaround if you want that similarity.
You can do that with controlled syncing.  Firefox has a feature that allows you to selectively synchronize most of what reflects "you": preferences, add-ons, log-ins, history, bookmarks, etc.  It can be accessed through Preferences | Firefox Account.
You obviously don't want to synchronize some of those options with a private mode profile. For example, add-ons (since you want them to be different).  You also probably don't want to sync history (Firefox won't retain the history when you finish the session, but I'm not sure whether it would sync the visited sites during the session, and that would defeat the purpose of private mode).  Login information is another thing private mode erases at the end of the session, so you probably don't want to sync that.
In any profile, the sync selections control what that profile shares with, and updates from, your other profiles.  So you can have several computers that share everything, and a private mode profile that only shares and updates certain options.
Syncing uses an email address as a unique identifier.  You create an account tied to an email address.  Firefox will remember the account ID for you and automatically sync when you start or there is something to update (or you can activate and deactivate syncing manually).
If you will want a lot of add-ons in private mode, you might want to initially sync them just to install all of your current add-ons in the private mode profile.  Then deselect add-ons for syncing, and remove or disable the ones you don't want active in private mode.
Profiles vs. Portable Firefox
Firefox, itself, is like a browsing "engine".  Everything you do that makes it different for you is stored in your profile, which is located separate from the Firefox application software.  That includes preferences you set, add-ons, the history of sites you visit, your bookmarks, etc.  When you update Firefox, it updates the software, but doesn't touch your profile (well, except to verify that all of your add-ons are still compatible).
This also allows things like having multiple users on one computer, or a user with multiple profiles, while requiring only one copy of the Firefox software to be taking up space on your drive.  Your "user experience" comes from the Firefox application using your profile.
Downloading a separate portable Firefox, as you suggest in a comment,  would produce sort of a similar result, but it's not the same.  That would add another copy of the Firefox application just to get another profile.  There are also some subtle differences in the portable version, like it can have only a single profile.
Comment: All browser developers have controls in place to try to pre-screen for that and to remove offending add-ons if discovered, and your antivirus software screens for that.  I don't know if 100% of Firefox add-ons are open-source, but I think most of it is.  It's tougher to hide malware in code that anyone can look at.  So, like any software you load on your computer, there is some chance that malware will slip through, but add-ons from the browser's repository are generally as safe as you'll find from any trusted source.
Comment: Thank you. Some follow-ups: 1. I looked into this profile option but it seems like it will have it's own bookmarks too. Any way to access the same bookmarks 2. This profile option seems the same as downloading a separate portable Firefox and configuirng that with no add-on. Is that correct?
Comment: @get_going, good points.  Too much to address in a comment, so I'll expand the answer.
Comment: Hi fixer1234, thanks for the detailed explanation. I will try out your suggestions and report back. Meanwhile, can you tell me something. I'm sure that developers of Firfox would have give this some thought. And you state that, "add-ons are required to comply with the private mode rules". Is that really the case in reality? Can I assume that no add-on would surreptitiously record my sites in private made, or maliciously store login info?
Comment: @get_going, I'm not familiar with what screening developers need to go through to get their add-ons in the Mozilla add-on repository (grabbing add-ons off the Internet outside of that is at your own risk).  Private mode is pretty straight-forward.  Certain things, like history, cookies, etc. are defined as stuff that is supposed to be deleted upon exit; it's just prescribed behavior.  There is no reason for a developer to make their add-on work differently.  Doing things surreptitiously or maliciously defines an add-on as malware, which is completely different.  (cont'd)


Downloading salinity data from Government of Canada

Question: Since I would like to use the salinity data with lat/lon in the Gulf of St. Lawrence, Canada to compare with the fishing data.
I'm trying to download the 2010-2019 average salinity data.
As the table in this database showed. (https://www.arcgis.com/home/webmap/viewer.html?url=https%3A%2F%2Fgisp.dfo-mpo.gc.ca%2Farcgis%2Frest%2Fservices%2FFGP%2FTeleost_BottomTemperatureSalinityFond%2FMapServer&source=sd)
Comment: Welcome to GIS SE!  As a new user be sure to take the [Tour] to learn about our focussed Q&A format.  You appear to have created two accounts which inevitably leads to a frustrating experience for you, potential answerers and reviewers so please follow [these instructions](http://gis.stackexchange.com/help/merging-accounts) ASAP to merge your accounts.
Answer: In QGIS you can load the data directly. Using connect to ArcGIS MapServer in the browser window.
<code>https://gisp.dfo-mpo.gc.ca/arcgis/rest/services/FGP/Teleost_BottomTemperatureSalinityFond/MapServer
</code>
Answer: They have not enabled download through the ArcGIS Online, which would have been simplest. You need to add a link to their server in ArcGIS Pro.
If you click on the link in their open portal site:

It takes you to the metadata page, in the address bar is the server location:

Add that to ArcGIS Pro or ArcMap, ArcGIS Pro is much easier to use...

Drill down to your layer of interest and add to map so here is 2019 salinity

If you try to export the data it won't allow you, they have in their wisdom disabled that, not sure why one would share data and then not allow you to export it... They are also symbolizing this continuous surface as a polygon layer, a bit weird, would normally be raster. But the information you seek seems to be in the attribute table so you can export that using the table to table tool or table to Excel for example.
Here are the first 65 rows exported to an in-memory table to prove it works:


Magnetic Particles

Question: My chemistry book mentioned magnetic particles today when introducing electromagnetic radiation. It stated that a magnetic field is a region of space where magnetic particles "experience a force." In the same way that an electric field influences the movement of electrically charged particles.
I've always had trouble understanding magnetic fields because of the ambiguity. Electrically charged particles have names (Protons and Neutrons among others) but what are the names for magnetic particles,  and what are they?
Are magnetic particles smaller than atoms?
Comment: Pretty much _all_ particles are magnetic, including protons and neutrons. (The latter, BTW, are **not** electrically charged.)
Answer: I think that statement is misleading. Magnetic charge does not exist, so there is no equivalent to a magnetic electron or proton. Instead it acts on two major types of quantities:

Moving charges or current. Magnetic fields cause charges to rotate around the direction of the field.
Spin. Spin is a quantum phenomena where elementary particles like electrons and protons interact with magnetic fields as if they had tiny bar magnets inside of them. The spin aligns itself to try to be parallel to the magnetic field.

In the majority of cases, you can essentially think of the magnetic field as a force that acts on moving charges and permanent magnets (like spin). But there is no such thing as a fundamental magnetic particle with magnetic "charge".
Comment: Can you tell me why the spin of charged particles are influenced by magnetic fields? Is it the charicteristic charge itself that the field interracts with, or is there something else about the proton or electron that is inherent within it that interracts with the field. In other words,  what is the real science behind what you called the little bar magnets inside them?
Comment: Spin is an intrinsic property of elementary particles. Electrons, protons, and neutrons all have spin. There honestly isn't a very good reason for spin that isn't circular reasoning. But, it eventually comes down to being an essential ingredient in making Quantum mechanics compatible with special relativity.
Answer: I've never hear of "magnetic particles" in conjunction with basic science. The term is, however, used to describe very small pieces of iron or iron oxide used in industry for finding defects in metal parts .https://www.nde-ed.org/EducationResources/CommunityCollege/MagParticle/Equipment/Particles.htm
More importantly, from a basic science perspective, is that electrons, protons, ions and other charged objects will experience a magnetic force when moving through a magnetic field, exception being if they are moving directly along the field lines.  This is interesting because it shows a link between electricity, as in charge, and magnetism.
This is also important to a beginning Chemistry student because this relationship was instrumental in the discovery of the electron and developing early models of the atom.
Comment: Can you tell me why charged particles are influenced by magnetic fields? Is thethe charicteristic charge itself that the field interracts with,  or is there something else about the proton or electron that is inherent within it that interracts with the field.
Comment: @Ashton. Some folks can tell you more about this but I don't think anyone can say why at the most fundamental level. There are four force known in nature, a fifth if you include dark energy. Physisists have succeeded in showing that electricity and magnetism can be "unified" into one force, the electromagnetic force. Current moving in a wire creates a magnetic field. Magnetic fields exert forces on moving charges. Electricity and magnetism are "two sides of the sme coin". You might try your "why" question separately, see what you get.

Magnetic Particles


ceiling fan installation with two white wires

Question: the current light is connected to the white wires coming out of the box now.The two black wires are hooked together. can I hook the fan to the white wires like the light is now?  Is it safe to do this?  There is not ground in the box.  When I looked in the breaker box, the white wires were hooked to the ground bar.
Answer: You're likely seeing what's called a "switch loop". So the white wire of the cable running between the switch and the light, is used as the switched hot.  The wire should be reidentified as such, but it's often not.
If you're connecting the new light exactly as the old light was, you're probably okay. Use a voltmeter or multimeter to confirm, or have a look in the switch box.
Answer: I would guess that one is actually hot one neutral and not marked properly...  The black to black connection is most likely going to a switch, and out of the switch for what ever reason they ran a white and did not label it... BUT it is always concerning when you do not see proper colors :)  I would check the switch...


Public transport in Stockholm

Question: I am going to Stockholm for 10 days. I do not drive, so I would like to know what is the most cost-effective way to use public transportation? Is there e.g. a weekly/monthly pass that I can buy once and use anywhere? (I tried to look at websites but everything I found was in Swedish...)
Comment: SL, the public transport company have their web site, almost of course, also in English: https://sl.se/en/
Comment: @MarkMayo I thought my last comment was explanation enough for the down vote. OP allegedly can't find information in English, but googling for "stockholm public transport" will give the page I linked to as first search hit. Call it lack of most trivial efforts to solve the problem with some own research. The question also can't be answered as it is asked. Wether single tickets or a weekly/monthly pass is most cost effective will obviously depend on how much public transport OP is planning to use, but he keeps that a secret.
Comment: Can downvoters please leave comments explaining their vote.
Answer: Stockholm has an excellent web site in English that explains all the details and even has a well made and reasonably funny video to explain it. See https://sl.se/en/in-english/getting-around/
https://www.youtube.com/watch?v=HbKTjOjcWos
Tickets and fares are explained here https://sl.se/en/in-english/fares--tickets/
Which one is the most efficient for you depends on how often and how far you want to travel. We can't know this, so you need to assess this yourself.
Answer: You can find an SL center at the T-Centralen of Stockholm, where you can buy tickets (cards with chip) and also discuss what options there are. Tickets are also sold at certain convenience stores, (Pressbyran). The public transportation is good, but sometimes there might be issues (yesterday, two major stations closed down due to rust in the new escalators - yes, really!).

Public transport in Stockholm


Why is the unit circle the preferred circle to derive values of trig functions?

Question: I am reviewing basic trigonometry and came across a nice example that uses an equilateral triangle (sides of length r), cut in half vertically, to demonstrate that cos(60) = r/x = r/(r/2) = 1/2.  From high school, I had always thought that the unit circle was somehow more significant for deriving trigonometric values, but now I find myself unsure, realizing that the trig functions are simply representations of ratios of sides of triangles of any size.  Why is the unit circle the preferred choice to derive values over another circle of radius (hypotenuse) r?
Comment: Because when you make the ratio, the denominator is $1$. That's a friendly ratio.
Answer: Fundamentally, it is so much easier using the unit circle.
But there is something deep going on. The complex number formula $e^{ix}=\cos x + i\sin x$ traces the unit circle, and the fact that the path traced by $e^{ix}$ for $a\leq x\leq b$ is of length $b-a$ are deep reasons.
But you can define them with any circle. You just always end up dividing by the radius in those cases.
Comment: Meaning, it is easier to visualize the values, and not actually when calculating them?  Specifically, I find using an arbitrary value r in the case of cos(60) more meaningful, though this is a trivial example.
Comment: Meaningful is a tricky thing. The reason it doesn't matter what radius we use is due to the similarities of triangles. As I pointed out, there are advanced ways in which $\sin x$ and $\cos x$ are "about" the unit circle. More basically, the equation $\cos^2 x+\sin^2 x = 1$ is a statement that $(\cos x,\sin x)$ is on the unit circle. That seems pretty "meaningful" to me, but it is a subjective standard.
Answer: Because the "unit" (whatever) is the preferred (whatever) to work with.
In linear algebra, you can work with orthogonal vectors, but it is easier to work with "orthonormal" vectors, that is unit orthogonal vectors that have been divided by their norms.
And as Thomas Andrews pointed out, you can work with circles, but it's easier to work with (unit) circles whose size have been divided by their radius, and therefore have a "radius" of one.
Comment: I think this makes sense.  Because a trig function is a ratio, and a ratio has a max value of 1, suggests that when visualizing the points of the functions one can and should represent them with r=1, even if it does not provide any advantage in terms of calculating actual values of the functions.


Minimum postfix config to send mails to a smtps server

Question: I'm trying to send mails with python so I configured a postfix server locally. The python part seems to work as my mails reach the smtpd server. After that, postfix seems to correctly query the MX record and tries to connect the right dns name.
The problem here seems to be that my postfix server never tries port 465, only 25, fails as the port is closed, then give up until the retry timer resets.
Here is my <code>/etc/postfix/main.cf</code> file. I totally know that I'm not fully aware of what I'm doing
<code># Debian specific:  Specifying a file name will cause the first
# line of that file to be used as the name.  The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.
# Optional, if you want this postfix to use TLS when acting as a client
smtp_use_tls=yes
smtp_tls_security_level = may
smtp_tls_note_starttls_offer = yes

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = yamatetsu
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = yamatetsu, localhost.localdomain, , localhost
relayhost =
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = localhost
</code>
Again, all I want is to get my python client to send mail to arbitrary destinations, some of which have port 25 closed. The python client seems to connect through port 25, but I would like postfix to figure out how to reach remote servers itself. I do not want to receive mail and I care little about security since everything will be on a single machine behind a NAT.
I'm running ubuntu 14.04 and I installed with apt-get. I also tried to use self generated tls certificates with openssl, but since the line is prefixed with smtpd I'm not sure it is mandatory or not. I'm not even sure how to see if it is correctly parsed or not.
Comment: If you have limited destination domains - you can use transport maps and specify port for each domain. Of course MTA on destination domain should accept incoming mail on non standard ports - 465, 587, 2525 and so on.
Answer: Looks like the configuration works, but my ISP is blocking port 25. Best part of it is that they can't seem to do anything about it since they are reselling a cable trunk.


Is it possible that Office word content convert to Rich Text Field and keep format?

Question: My customer usually copy n paste to rich text field from office word document, but the format always lost, is it possible that Office word content convert to Rich Text Field and keep format ?
Answer: It should preserve all formatting if you use any browser apart from IE9. See here for more details. This was fixed in Summer 13.
Comment: I am not sure that it's about brwowser, but I found another way to keep format.
Answer: I found another to keep date format into rich text from MS word document, if I save as html file type(.htm), reopen this in chrome and copy n paste, it can keep table and indent safe in rich text field, awesome.
1. Original Word document.

2. copy n paste to rich text field directly.

3. Save as Html File Type, reopen via Chrome and copy n paste.


Convert seconds [s] to milliseconds [ms] in Paraview "Plot Selection over Time"

Question: After composing my Paraview scene, I realised that I need to represent the units in a "Plot Selection Over Time" filter instead of seconds in milliseconds. How can one accomplish this?
Answer: The long way, modifying only the display:

manually set the ticks with the advanced option Bottom Axis Use Custom Label

The quickest way, modifying the actual scene time:

use the Temporal Shift Scale filter before plotting
Answer: The best way (and one of the most important feature of paraview) is that you can setup your selection and you can save the state in a PvPython script. Later you can modify the script by changing the units there. Finally you can save the plot (or even better save the data in a file and later plot them with pgfplot or with another plotter). You can find an example of script here (here the plot line feature is used, but in your case when you will setup the state it will be a selection).
For sure this is longer than doing it with the UI, but it allows you to:

auomatize everything;
Use the script on a cluster, or when you do not have access to the graphical interface.


Is jQuery's $.post binary safe?

Question: Is jQuery's <code>$.post</code> method binary safe? Just out of pure interest anyway, so please don't assume anything.
And if so, are all ajax functions binary safe?
Answer: Usually, binary safe means that it isn't null terminated and any kind of characters can be contained within the strings that are about to be used, mostly just meaning the function can handle any kind of binary data (images, music, etc).
Thing is: you can't use binary files for AJAX requests. You cannot upload files and you can't handle a binary file as response (only text output). This isn't about jQuery, but about the way it works in the lower level. XmlHttpRequest can't handle such things.
Since the underlying technology doesn't support binary data for requests or responses, $.post does not either.
Now, on HTML5 we have ways of managing binary data and files for AJAX:
https://developer.mozilla.org/en-US/docs/Using_files_from_web_applications
However, this is "new stuff". So, just wait for it to be supported in multiple browsers and then it might get picked up by frameworks :) For now, only FF supports it (the XMLHttpRequest.prototype.sendAsBinary method). You can get similar functionality on Chrome by using Blobs, but it ain't the same.
Answer: In short, no because you have to right your own handlers. Plus, not all browsers support binary files ajax transfer...
refer to this forum post:
http://forum.jquery.com/topic/jquery-get-support-binary-type
Answer: You just have to check defination of Binary safe function over here
http://whatis.techtarget.com/definition/binary-safe-function

Is jQuery's $.post binary safe?


Is it possible to write cross database join queries?

Question: Multiple Databases on Multiple Servers from Different Vendors the databases are on different servers and some of the servers run different database software. For example, the customers database may be hosted on machine X on Oracle, and the orders database may be hosted on machine Y with Microsoft SQL. Is it possible to write join queries and which framework best suits for the case (Spring, ASP.NET
 or any other)?
Answer: In PostgreSQL you can map and join tables:
From MySQL, HDFS and MongoDB using EnterpriseDB's foreign data wrappers - https://github.com/EnterpriseDB/
From SQL server - https://github.com/tds-fdw/tds_fdw
From Oracle - https://github.com/laurenz/oracle_fdw
Comment: What about other database systems such as Oracle, MSSQL?
Answer: Yes,it is possible to write cross database join queries.In oracle you can create DB link for another database and access the schemas in that DB using DBlinkk@schema_name.
Full documentation is present here:
<code>[https://docs.oracle.com/cd/B19306_01/server.102/b14200/statements_5005.htm][1]
</code>


How can I check open ports on android?

Question: I know that every ISO based network system uses TCP port, and Android is of course not an exception.
My question is, can I check the open ports in my device? Can I close them? Is there an app to handle this issue?
Comment: The _average_ smartphone use does not understand the concept of TCP and ports :) And, product recommendations are off-topic here anyway. But, did you even try to search for nmap on android or similar? Because you'll actually find apps that way.
Comment: The title and the body of the question do not match. Title asks if the concepts exists (of course as you realize yourself in the body) and body asks if it is possible to check what is open and close open ports. Also, the intention to close ports is not clear: ports are open if there is some service or app listening for data which means you should close the service/app.
Comment: How do you check open ports on other systems? You can also use nmap against Android or you can use netstat if you've got a shell on the Android system (for example with adb). There is nothing special. And, if you are root you can also install your own firewall rules.
Comment: @SteffenUllrich correct, changed it.
Comment: I thought a more friendly app could exist for average smartphone users. Should I delete the question?
Answer: You can use a terminal emulator and execute the following:
shell@android:/ $ cat /proc/net/tcp

That will list open ports.
Alternately, install an app like OS Monitor.
If you want to close any, use a Firewall app.

How can I check open ports on android?


Can a new player accomplish a 160k assassination mission without any upgrades to its Sidewinder?

Question: There's a mission to assassinate an NPC for 160k. That's a lot of money. I wonder if that much money means I need a better ship and weapons than the initial ones to be able to accomplish this task.
Answer: No.
You'd struggle in a fully upgraded Cobra. You're generally fighting well equipped, experienced Anaconda pilots. You'd also waste a fair bit of time tracking them down. I've been there!
Comment: I agree.  It isn't impossible to take out an Anaconda in an underpowered ship though, but you need to be able to make use of your environment to hide and recover shields (I'm thinking asteroid belts), but if the Annie has shields, you'll have a very hard time getting and keeping them down long enough to damage it whilst trying not to die.
Answer: Absolutely not. Think of the reward as the level of difficulty. If 160k is a lot to you, it's probably too difficult. The AI on those kinds of criminals is far better than the ones you find in warzones or RES nodes. And as a wise man once pointed out, your basic weapons are essentially laser pointers. You'll need strong beams (to knock out shields) and cannons (for hull damage) to do reliable damage.
Try some training in RES nodes, buy yourself a better ship (a Viper is a good choice for a combat-focused build), trick it out with full upgrades (don't forget shield cells), and then give it a shot. It'll cost you a couple million credits, but you'll stand a chance. Not a great chance, but by the time you're ready to hunt down one of those bad boys, you should be skilled enough to take him out. Just target the Power Plant, and it'll go nuclear once you knock it out.
Alternatively, just play it safe and wait until you can grab a Vulture or other higher-end combat-focused ship.


In Revelation12:14, the word "times", could it mean more than two?

Question: Could time's be more than two time's, in a time time's and half a time.
You could say Jesus lived for a time times and half a time, the time's is 8 time's
1260 days to 0 BC and 8 time's 1260 is 28 years plus 1 year and 3/4 thats about 33 1/3 years?? its a thought?
Comment: Welcome to BHSX.  Thanks for the question.  Please remember to take the tour below to best understand how this site works.
Comment: its 8 times, we already know Daniel was speaking on the future not the present
Comment: https://en.wikipedia.org/wiki/Day-year_principle
Comment: I will Quote the Naqshbandi Prophet Abu Yaqub Yusaf al hamadani ( Just because you are not privy to the secrets, Do you think know one else is either) Your all stuck in the past thats why you can't see whats right in front of you, I will not post herte again
Answer: No. It is a Greek translation of the Hebrew dual, meaning two. It is a reference to the same phrase in Daniel 7.25 and 12.7, which is described as a half-week of years in Dan 9.27.
If you have a perfect religious calendar, then it also equals 42 months and 1,260 days. These times period occur several times in Rev 11 and 12 (referring to the same time, but exploring different aspects of it) but only in these chapters.
It signifies the 'in-between' time in which we live. It is the time between Jesus' first coming and his return, when the kingdom of God (the 'age to come') has broken in, but this age is still all around us. It is the time when Christians experience our Exodus 'desert wandering' since we have left the slavery of sin in spiritual 'Egypt' but have not yet entered the promised land of the New Jerusalem.
(The numbers 42 and 1,260 are also 'rectangular' numbers which share some qualities of square numbers, which signify God, and triangular numbers, which signify evil. We are to be God's holy people in a fallen world.)
Comment: Considering that Ian gave the acceptable answer I'll add that Revelation speaks of the 3.5 years following the crucifixion event. Referencing the same event twice, during which St John took care of Mary. Rev 12:2 defines the timing as the first coming, seeing as how the second coming he returns from the sky as referenced in Acts.
Comment: But in Revelation all these time periods are symbolic, not literal. I don't believe that Revelation and the Fourth gospel were written by the same person (there are too many differences in language).
Answer: No.  A time was 1 year; times was 2 years; and half a time was 1/2 year.  Three and 1/2 years.  This is the same as 42 months, or 1260 days (30 days/mo).  The problem comes in trying to use the book of Revelation as a still future prophesy.  It must be read in perspective of the first audience, which was of the saints to whom it was sent in the 1st century AD!
Revelation was written before the destruction of Jerusalem approximately 66 - 68 AD.  We have confirmation brought forth by Robert Young in his concordance (Young's Analytical Concordance, 1885) concerning the date of the writing of Revelation:

"It was written in Patmos about A.D. 68, whither John had been banished by Domitius Nero, as stated in the title of the Syria version of the book; and with this concurs the express statement of Irenaeus in A.D. 175, who says it happened in the reign of Domitianou – i.e., Domitius (Nero).  Sulpicius, Orosius, etc., stupidly mistaking Domitianou for Domitianikos, supposed Irenaeus to refer to Domitian, A.D. 95, and most succeeding writers have fallen into the same blunder.  The internal testimony is wholly in favor of the early date. The temple at Jerusalem was still standing (ch. 11.1-10); the exact duration of the siege is foretold, viz., 42 months, 3(-)1/2 years, or 1260 days; the two witnesses are to be slain in the city where our Lord was crucified; Nero was reigning at the time, for it is said of the seven kings of Rome; 'five are fallen, and one is, and the other is not yet come, and when he cometh, he must continue a short space.' The five kings are Julius Caesar, Augustus, Tiberius, Caligula, Claudius. The 'one who is ' is Nero; the one who 'must continue for a short space' is Galba, who reigned only seven months. Everywhere the events are 'to come quickly,' lit. 'with haste,' or speed (ch. 1.1; 2.16; 3.11; 11.14; 22.7, 12, 20). The escape of the Christian Jews from Jerusalem to Pella is undoubtedly referred to in ch. 7.1-8, compared with Mat. 24.30.'"  (1)

The prophesy of Revelation was the fulfillment of the original prophesy Gabriel gave to Daniel in Dan. ch. 9 - 12, which detailed the people and the city of this prophesy.

"Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins, and to make reconciliation for iniquity, and to bring in everlasting righteousness, and to seal up the vision and prophecy, and to anoint the most Holy."  (Dan. 9:24, KJV)

When left in the context of the words Gabriel spoke to Daniel, "thy people" was Daniel's people, and "thy holy city" was Daniel's holy city - the Jews and Jerusalem.  Daniel's people were not the Russians, nor the Germans, nor the French, nor the Iranians, nor the Americans, nor the Chinese.  The entire prophesy was of the full and complete destruction of Jerusalem and that second temple they built after the return from the Babylonian captivity.
The Messiah would be cut off in the middle of the 70th week (of 7 years).  Bypassing for the moment the argument over when the command was given to rebuild the temple, we can positively identify the time period when the Messiah was cut off - 31 (33) AD - the first century AD.  Just focusing on the time of the 70th week we can know several things.
The middle of that 70th week meant that 3-1/2 years of that week had already passed, and they were the 3-1/2 years of Jesus' ministry on earth.  Cutting Him off in the middle of that week was His crucifixion.  First century AD.
The last 3-1/2 years happened after the preaching of the gospel throughout the known world, the inhabited world of that century... the same world of the Roman empire which was defined in Luke 2:1. (2)  Paul testified in Col. 1:23:

"...the hope of the gospel, which ye have heard, and which was preached to every creature which is under heaven; ..."  (KJV)

Every creature under heaven was the reference to every soul under the authority and dominion of that Roman empire of the 1st century AD.  The word "heaven" was used in OT prophesies as a metaphor for earthly kingdoms - dominions and authority of men as a type, a small piece of God's entire heaven over all the earth.  Their palaces and their kingdoms were referred to as heavenly places.  This is the same reference meant in Eph. 3:10 because it was God who raised them up,  and allowed them their power and rule. Their earthly dominion was their heaven.  See Ex. 9:16; Judges 2:16, 18; 2 Sam. 23:1; Is. 41:2, 25; Is. 45:13; Jer. 51:11, etc.  (3) (4)
The book of Colossians was written approx. 62 AD.  Therefore, as Paul stated that the gospel had been preached throughout the world of the Roman empire by 62 AD, then the end of the desolations of Jerusalem and the last days was shortly to come to pass(Rev. 1:1). This was the reference back to Dan. 12:6.

"...How long shall it be to the end of these wonders?"  (KJV)

The answer was in the very next verse.

"... that it shall be for a time, times, and an half; and when he shall have accomplished to scatter the power of the holy people, all these things shall be finished."  (Dan. 12:7, KJV)

This the end of the 490 days which Gabriel told Daniel in 9:24 would be the end of the desolations of Jerusalem.  The word desolations means complete destruction.  The end was never speaking of the end of all life on earth, nor the end of all time.  It was the end of that old animal sacrificial temple of the Mosaic covenant in Jerusalem.  When the power of the holy people... the power of the Jews in Jerusalem... the power of the Sanhedrin's tyranny over the saints was scattered - that was the end.
That end occurred when that temple in Jerusalem was destroyed in the Roman-Jewish wars of AD 70.  The wars began approx. Feb 67 AD, and ended with the seige of Jerusalem that lasted 5 months (Rev. 9:5, 10) until Sept AD 70.  The last half of the last 70th week was 3-1/2 years of the destruction of Jerusalem.
The interval of the 40 years on an inclusive count between the cutting off of the Messiah in AD 31, and which 40 years was the anti-type of the Exodus 40 years in the wilderness before they entered the earthly promised land.  The anti-type of the end of the Mosaic covenant release from sin and death of the law was the entrance into the spiritual promised land of the new covenant under the gospel of Christ at the full establishment of His kingdom once that old temple was destroyed in AD 70.  (5)
So, we are not living in the last days.  They were.  The last days occurred when Christ walked on this earth.  The last days were "this generation" in which He spoke to His disciples and told them that "all things" would occur in that generation (Matt. 24:34)  It is not "this generation" when we are reading those words 2,000 years later.

"For all the prophets and the law prophesied until John." (Matt. 11:13, KJV)
"Who verily was foreordained before the foundation of the world, but was manifest in these last times for you,"  (1 Pet. 1:20, KJV)

Christ was manifested in the last times, and we know He was manifested in the 1st century AD, therefore the last days were in the first century AD.  We must read these scriptures from the perspective of those people of that century as those were the last times. (6)
Those 3-1/2 years happened a long time ago.  Those days of the Mosaic covenant were the "passing away" of which all of the book of Hebrews spoke.  When they said "the age to come" they were still looking forward into their future to the destruction of that temple (Matt. 24) which had not yet happened for them.
The age to come for them, is now our age... the Messianic age of His everlasting kingdom which we are living in, and which has no end (Isa. 45:17; Eph. 3:21). (7)
Notes:
1) The Signs of Revelation- Part I: The Time of His Coming - ShreddingTheVeil
2) Frequent Mistakes - Part IV: Where Was All the World? - here
3) Heaven & Earth Have Passed Away - here
4) Revelation: The Four Corners of The Earth - here
5) The Promised Land: Between the Cross and the Kingdom - here
6) It's Not The End of The World - Part I - here
7) Frequent Mistakes - Part VI: THe End of The World, or? - here
Answer: This phrase ('time, times and half a time') comes from the book of Daniel (Daniel 7:25, 12:7) and the book of Revelation (12:14) where it is linked to 1260 days (Revelation 12:6).
Through Daniel 12:11 'time, times and half a time' is associated with a period of 1290 days, where sacrifices are stopped and the time 'abomination of desolation' is set up. This seems to be a clear reference to Antiochus Epiphanes IV and yet Jesus points to the end times when this would happen in Matt 24. It seems therefore that the 'abomination of desolation' refers to tyrants, agents of Satan's evil cause and thus ties into different periods of 'time, times and half a time' of evil rampage.
However the year is calculated (365.25 days or the more prophetic 360 days) it is usually linked with the short period of 3 ½ years.
'time, times and half a time' is linked to many periods throughout history that are comparable, these are times of tribulation where there is judgment and justice is served. The bible informs or directs us to these times:

525-521 BC - Cambyses (son of Cyrus, before the Second Temple is
built)
476-472 BC – Haman (adversary to Esther)
168-164 BC –Antiochus Epiphanes IV
29-33 AD – Jesus (the Light of the world)
against the dark enemy
67-71 AD – Titus (destroyed to the temple and took away the Menora, the light/authority by which the Jews administered justice)

So I concur that 'times' is double of 'time'.
1260 years
The 'time, times and half a time' in Revelation 12:6 uses the prophetic 1260 days, where it is 1260 years (3 ½ x 360). This type of prophetic conversion from days to years is justified by:

I have assigned you the same number of days as the years of their sin.
So, for 390 days you will bear the sin of the people of Israel. After
you have finished this, lie down again, this time on your right side,
and bear the sin of the people of Judah. I have assigned you 40 days,
a day for each year. Ezekiel 4:5-6

It is a literal 1260 years where the devil deceived the nations:

The great dragon was hurled down—that ancient serpent called the
devil, or Satan, who leads the whole world astray. Revelation 12:9

1000 years
The number one thousand (1000) symbolizes "immensity," "fullness of quantity" or "multitude."
This I believe is where have made the biggest mistake has been made: it is not a literal 1000 years (e.g. a Millennium). We are to wait until the full number of the Gentiles have come in (Romans 11:25).

And I saw an angel coming down out of heaven, having the key to the
Abyss and holding in his hand a great chain. He seized the dragon,
that ancient serpent, who is the devil, or Satan, and bound him for a
thousand years. He threw him into the Abyss, and locked and sealed it
over him, to keep him from deceiving the nations anymore until the
thousand years were ended. After that, he must be set free for a short
time. Revelation 20:1-3

In this scenario, when the 1260 years is over when Satan had deceived the nations, something momentous happened that put Satan in the Abyss for '1000 years' – with life in heaven and Christians reigning in the life of Christ down on earth. Note, even though Satan was put in the Abyss his angels are still on earth (Rev 12:9), and the deceived nations are quite capable to continuing being misled without other input.
Satan will be released from the Abyss when the contention between good and evil culminates. And Jesus will return at an undisclosed time.
So how have I split the time up:
257 AD – 1517 AD = 1260 years, the dark ages until the doctrine of grace established by Martin Luther. This is followed by the '1000 years' that we are in now. 1517 AD marked a time of 'awakening' and more and more revivals have sprung up.
Light and justice are key themes. Consider Jesus is the Light of the World, that the Menora taken from the Jewish Temple, the threat to remove lampstands from churches of the book of Revelation and the light of revelation of the doctrine of grace to Martin Luther.
There is more to this can be written here so please have a look here.


How can I create a waveform image of an MP3 in Linux?

Question: Given an MP3 I would like to extract the waveform from the file into an image (.png)
Is there a package that can do what I need ?
Comment: Yes, there is a tool that does exactly that: http://www.tuned-project.org/audio-tools
Comment: @user1217953 - tuned audio tools link is dead, it seems to be in https://launchpad.net/tuned-audio-tools/+download (note, you'd need `libgee` and `gstreamer-1.0` to build); see also https://github.com/limikael/rendersound (note, you need a relatively new `libavcodec` to build it); see also [wav2png](http://stackoverflow.com/a/11067909/277826)
Answer: Using sox and gnuplot you can create basic waveform images:
sox audio.mp3 audio.dat #create plaintext file of amplitude values
tail -n+3 audio.dat > audio_only.dat #remove comments

# write script file for gnuplot
echo set term png size 320,180 > audio.gpi #set output format
echo set output \"audio.png\" >> audio.gpi #set output file
echo plot \"audio_only.dat\" with lines >> audio.gpi #plot data

gnuplot audio.gpi #run script

To create something simpler/prettier, use the following GNU Plot file as a template (save it as audio.gpi):
#set output format and size
set term png size 320,180

#set output file
set output "audio.png"

# set y range
set yr [-1:1]

# we want just the data
unset key
unset tics
unset border
set lmargin 0
set rmargin 0
set tmargin 0
set bmargin 0

# draw rectangle to change background color
set obj 1 rectangle behind from screen 0,0 to screen 1,1
set obj 1 fillstyle solid 1.0 fillcolor rgbcolor "#222222"

# draw data with foreground color
plot "audio_only.dat" with lines lt rgb 'white'

and just run:
sox audio.mp3 audio.dat #create plaintext file of amplitude values
tail -n+3 audio.dat > audio_only.dat #remove comments

gnuplot audio.gpi #run script

Based on this answer to a similar question that is more general regarding file format but less general in regards to software used.
Answer: FFmpeg showwavespic
FFmpeg can do it in a single command as usual:

tutorial on wiki at: https://trac.ffmpeg.org/wiki/Waveform
documentation for the filter: https://ffmpeg.org/ffmpeg-filters.html#showwavespic

Sample command:
sudo apt install ffmpeg
ffmpeg -i in.flac -filter_complex "showwavespic=s=640x320:colors=black" \
  -frames:v 1 out.png

You can also set colors in RGB colors=0x0088FF: Using hex colors with ffmpeg's showwaves
Sample test data of me saying "Hello my name is Ciro Santilli" with two identical stereo channels:
wget -O in.flac https://raw.githubusercontent.com/cirosantilli/media/d6e9e8d0b01bccef4958eb8b976c3b0a34870cd3/Hello_my_name_is_Ciro_Santilli.flac

Output:

Background color
The background is transparent by default, but:

the Wiki teaches us how to add a image background: https://trac.ffmpeg.org/wiki/Waveform#Addingabackground
Overlay timelapse video on solid background colour using ffmpeg teaches us how to generate a solid color for an image

and so we reach:
ffmpeg -i in.flac -f lavfi -i color=c=black:s=640x320 -filter_complex \
  "[0:a]showwavespic=s=640x320:colors=white[fg];[1:v][fg]overlay=format=auto" \
  -frames:v 1 out.png

Added to the Wiki now ;-)
For the uninitiated, that CLI creates a processing graph:
black background (1:v) ------------------------> overlay ----> out.png
                                                   ^
                                                   |
in.flac (0:a) ----> showwavespic ----> (fg) -------+

where e.g. the overlay filter takes two image inputs and produces the desired output, and fg is just a name assigned to an intermediate node.

Split channels
The tutorial also covers other options such as split channels with -filter_complex "showwavespic=s=640x480:colors=black:split_channels=1":

gnuplot plot with axes
OK, I'll admit it, FFmpeg can't do this alone (yet!). But the Wiki already provides a data export method to gnuplot that works:
ffmpeg -i in.flac -ac 1 -filter:a aresample=8000 -map 0:a -c:a pcm_s16le -f data - | \
  gnuplot -p -e "set terminal png size 640,360; set output 'out.png'; plot '<cat' binary filetype=bin format='%int16' endian=little array=1:0 with lines;"

Video representations
See: https://superuser.com/questions/843774/create-a-video-file-from-an-audio-file-and-add-visualizations-from-audio
Tested on Ubuntu 20.04, FFmpeg 4.2.4.
Answer: If you have a GUI environment you can use the audacity audio editor to load the mp3 and then use the print command to generate a pdf of the waveform.  Then convert the pdf to png.
Comment: I was sincerely trying to be helpful (and amazed audacity could print).  Also, this: http://forum.audacityteam.org/viewtopic.php?f=15&t=38341
Comment: The question is posted on Stack Overflow. Therefore I think it's a programming question. What you are offering is a workaround, that can only be done if you have a _user_ that will do it for every file manually. Not doing -1 because I lold ))
Comment: Thanks for the help :) Although was looking to automate the process of creating a spectrogram (image) from and audio file (mp3). The link you sent looks real useful. Thanks
Answer: I would do something like this :

find a tool to convert mp3 to PCM, ie binary data with one 8 or 16 bit value
per sample. I guess mplayer can do that
pipe the result to a utility converting binary data to an ascii
representation of the numbers in decimal format
use gnuplot to transform this list of value into a png graph.

And voilà, the power of piping between unix tools. Now Step 2 in this list might be optionnal if gnuplot is able to read it's data from a binary format.
Comment: Sounds like a real good idea. Will give this a shot and let you know how it goes.
And yes gnuplot does accept a binary data file as its data source.
Thanks
Answer: You might want to consider audiowaveform from the BBC.

audiowaveform is a C++ command-line application that generates waveform data from either MP3, WAV, or FLAC format audio files. Waveform data can be used to produce a visual rendering of the audio, similar in appearance to audio editing applications.
Waveform data files are saved in either binary format (.dat) or JSON (.json). Given an input waveform data file, audiowaveform can also render the audio waveform as a PNG image at a given time offset and zoom level.
The waveform data is produced from an input stereo audio signal by first combining the left and right channels to produce a mono signal. The next stage is to compute the minimum and maximum sample values over groups of N input samples (where N is controlled by the --zoom command-line option), such that each N input samples produces one pair of minimum and maxmimum points in the output.

https://github.com/bbcrd/audiowaveform
Answer: This is a standard function in SoX (command line tool for sound, Windows & Linux)
Check the 'spectrogram' function on http://sox.sourceforge.net/sox.html
"The spectrogram is rendered in a Portable Network Graphic (PNG) file, and shows time in the X-axis, frequency in the Y-axis, and audio signal magnitude in the Z-axis. Z-axis values are represented by the colour (or optionally the intensity) of the pixels in the X-Y plane. If the audio signal contains multiple channels then these are shown from top to bottom starting from channel 1 (which is the left channel for stereo audio)."
Comment: A spectrogram displays frequency domain information of the audio stream, a waveform displays time-domain information. They are vastly different ways to represent sound.
Answer: Building on the answer of qubodup
# install stuff
apt install gnuplot
apt install sox
apt install libsox-fmt-mp3

#create plaintext file of amplitude values
sox sound.mp3 sound.dat

# run script saved on audio.gpi file
gnuplot audio.gpi

You can also comment the "set output ..." line in the configuration file and do
gnuplot audio.gpi > my_sound.png

The configuration file is audio.gpi in this case and inside it has
#!/usr/bin/env gnuplot

set datafile commentschars ";"

set terminal png #size 800,400
set output "sound.png"

unset border
unset xtics
unset ytics

set key off

plot "sound.dat" with lines

Which produces images like the following

I wanted no axis, no legend, png (much smaller than svg).


"Going Back to Houston" from where?

Question: Dean Martin sang of being in some city where he was broke, wet, hungry, and unknown. He sang of going back to Houston, but what city was he in? Was it a real city where he had been? I can't find anything on the historical background of this song.
I know he didn't write the song, but sometimes songs can still be personal, as with Papa was a Rolling Stone by the Temptations...Dennis Edward's real father apparently did pass away on the 3rd of September.
Comment: I don't have enough sources to write an answer, but it reminds me the vagrancy laws back then, when the homeless poors were banned from a place to another. In the song, the guy may have the opportunity to go back home after exile, maybe in close cities.
Answer: As Dean Martin wasn't a songwriter, it would be unlikely it had any personal meaning for him, except in the self-contained world of the song itself.
Houston was written by Lee Hazlewood

The lyrics are from the perspective on a down on his luck drifter who
  describes himself as "A walkin' case of the blues." The verses
  describe his many misfortunes ("I found a dollar yesterday, but the
  wind blew it away"), each ending with the repeated refrain "Going back
  to Houston, Houston, Houston...". The mood lightens on the final verse
  when the narrator reveals that despite his woes, he has a girlfriend
  waiting for him in the titular city.

"Going Back to Houston" from where?


Ubuntu 17.10 with Gitlab and Nginx (ha!)

Question: Gitlab installation worked straight away but "they" want this server to also serve other webpages (wiki and other stuff) so I had to unbundle nginx from Gitlab and do a full installation.
From what I've seen here (https://www.linode.com/docs/development/version-control/how-to-unbundle-nginx-from-omnibus-gitlab-for-serving-multiple-websites) I need passenger installed but, oh surprise, look what happens if you try to:
apt-get install nginx-common
{..}
The following packages have unmet dependencies:
libnginx-mod-http-passenger : Depends: nginx-common (= 1.10.3-1ubuntu3.1) but 1.12.1-0ubuntu2 is to be installed
E: Unable to correct problems, you have held broken packages.

So basically it doesn't finish passenger installation and I cannot continue :S
Any brilliant ideas?
Answer: So, if anyone gets there:
sudo apt-get install nginx-extras
sudo apt-get install nginx-common
sudo apt-get install passenger

And there you go. Hope it helps.


What causes emacs to not display the mini-buffer or window while starting up?

Question: I am starting up emacs and I cannot see aynthing in the minibuffer or display window until it starts up.  Is there a reason for this?
Comment: This is most likely a problem specific to your init file, so it's going to for others to debug. You can check your \*Messages\* buffer to see if there are any useful clues there. If not, you'll have to do a binary search through your .emacs to figure out where the problem is.
Comment: I don't understand your question: how can it display something before it has started up?
Comment: What do you want it to display?
Comment: It should desplay the packages that are loading... But it shows nothing.
Comment: I'm curious about this also - I've tried various things to be able to see the messages as packages are loading with use-package, but something must be interfering with it. I'm on Windows also.
Comment: Fwiw I think I have had this too but I just assumed the system is busy and I didn't care more than that.
Comment: I also have this behaviour. Sometimes I will get minibuffer messages, sometimes it will be blank. Windows also. I never considered it to be an issue.
Answer:
Is there a reason for this?

Yes, because it is busy starting emacs. However, it logs the most important messages in a buffer called *Messages* and in the operating systems log or event viewer -- depending on your operating system.
As others have commented above, after emacs has finishing starting up, look into the *Messages* buffer or the system's log for any clues to what could be ailing. Post those messages here to help you narrow down the cause.
Lastly, look into starting emacs with --debug command line option to get more verbose error messages logged to both the screen (during startup) and to the *Messages* buffer.
Comment: I am not sure what issue you are referring to.
Comment: Is this a common issue.  It seems to intermittently affect emacs.
Comment: Sorry, from the menu bar down to the edges of the windows the emacs screen is blank while starting up.  That is what I'm referring to as my "common issue".  It doesn't always occur and is difficult for me to track down.
Comment: Do you see any difference in messages logged in the messages buffer or the system or event logs?
Comment: No.  The message log is the same regardless of if the Emacs screen is blank.
Comment: Something else running on your system is interfering in the screen refresh process. Can't think of what emacs could do differently. What OS are you running on?
Comment: I'm using Windows 7.
Comment: what's the value of inhibit-startup-message, or inhibit-splash-screen ? If these are 't' (true) then they are set to not show.  I'm not sure actually what else you're wanting Emacs to display while it loads?

You said it doesn't always occur, what occurs when it's not blank?
Answer: I believe the answer given by @EmacsUser is right.
To better understand what's happening: Emacs has been around for
a long time.  Back in the day, I/O (input/output) with
terminals was very slow.  Because Emacs is incredibly powerful,
it was enhanced so that output to the screen would wait for
internal processing to complete.  That's why your screen
"freezes" when you execute that macro you just defined with an
argument of 12345 -- Emacs is busy working on your buffer(s).
When it's done, Emacs will refresh the portions of your sreen
that need refreshing.
When Emacs starts up, it typically has a lot of things to do.
Unless one of those things blocks, screen updates are essentially
ignored (i.e. they're very low priority), so you won't see what's
happening behind the scenes until Emacs is done processing.


Create Tickets From TODO (or otherwise annotated) comments

Question: Is there any software that will allow me to generate trouble tickets (for Trac, Team Foundation Server, etc.) from TODO or otherwise annotated comments in the source code?
Comment: Note that Visual Studio can display TODO comments in a list of tasks. It's just a list, so of course, everything related to a real bug tracking system is missing.
Comment: IDEA does something similar.
Answer: For Trac, there is a plugin called 'codetags' which provides a summary of encoded/tagged source comments without creating an actual ticket for each item.
http://trac-hacks.org/wiki/CodeTagsPlugin
Perhaps with some adaption or further extension, this plugin could help you create a ticket, or a batch of tickets based on tagged comments.
Answer: I've created a package for Atom Editor called imdone-atom that can create, update and close GitHub issues from TODO comments in your code.  I'll be adding more integrations like Waffle.io, Jira and Phabricator and also a stand alone (non-atom) version soon.
Trac could be easily added if there is an open API.


Can a region of Ukraine secede or become part of another country lawfully?

Question: If the population within a region of Ukraine wanted to become a
part of Russia (suppose a fair vote was 75% in favor), is there a
peaceful legal/government procedure in Ukraine to make this happen?
Assume Russia is welcoming.
Comment: Maybe a more descriptive and prescriptive term, like *Legal procedures for regional secession in Ukraine* would improve clarity.  The body itself is clear enough on what you're asking however.  Timely question.   One remark about the elusive notion of "fairness" (but not necessarily assuming this happened):  75% within a region may still not make things fully fair if significant population movements were triggered by unrests resulting from preceding secession attempts.
Answer: This would require a constitutional amendment:

Article 2

The sovereignty of Ukraine extends throughout its entire territory.
Ukraine is a unitary state.
The territory of Ukraine within its present [ie 1996] border is indivisible and inviolable. (source)

Now, as this is part of Chapter 1, it could only be amended by a 2/3 majority in the Verkhovna Rada, followed by a referendum in the whole of Ukraine, not just the secessionist region.
Moreover, Article 157 states:

The Constitution of Ukraine shall not be amended, if the amendments are [...]
oriented toward the liquidation of the independence or violation of the territorial
indivisibility of Ukraine.

So an amendment to cede part of the territory to Russia would itself be unconstitutional, and the Supreme court has the explicit power to rule that any discussion in the Ukrainian Parliament is unconstitutional. It seems likely that even discussion to remove the restriction in 157 would be "oriented towards violation of the territorial indivisibility".  The writers of the constitution tried very hard to make Article 2 unamendable by any constitutional process.
Of course, the constitution is only a piece of paper; it isn't self-enforcing.  The government and people of Ukraine could simply ignore the constitution, or make no attempt to enforce it - laying claim de jure but allowing secession de facto. However, I would not call this a "procedure", rather the inherent fact that state boundaries are not natural but defined by humans.
Comment: What about article 73? "Altering the territory of Ukraine IS[sic] resolved exclusively by an All-Ukrainian referendum". This seems to imply that it would be possible to have a nation-wide referendum to secede parts of Ukraine. In combination with article 2 it would perhaps only allow to make Ukraine larger, not smaller. But I think the answer should mention it for completeness sake.
Comment: ... actually I'm beginning to think that I'm using "self-enforcing" wrong... A self-enforcing agreement is one that remains in force only while all parties believe it is mutually beneficial.  Perhaps I should rephrase that. ...
Comment: Thanks for the details, I see that the procedure is nearly impossible! Financially, let me add that there should also be some payment by Russia, at least for the region's portion of national debt (and maybe natural resources though that gets more complicated and arbitrary).


Is css broken for SFSE?

Question: I opened SFSE, and to my surprise, the look and feel seems a bit odd, is CSS broken after recent update? To whom should I report this?
Comment: Please tag this as a bug so that the developers can check on that.
Answer: The Code of Conduct bar just pushes down all the content. Once you close it out the banner returns to normal.

Is css broken for SFSE?


"sparse on details" idiom

Question: Is this an idiom? When you say a study is "sparse on details" could you not just as well say "sparse with details" or "sparse for details"—they all make just as much sense to me. I'm trying to understand the role of the proposition on, if any. I understand that sometimes combination of words will become one, common grammatical unit and then be called idiomatic. This may be one of them.
Answer: Many constructions that end with the words "X on details"—where X indicates some type of deficiency—pair X with a corresponding positive word that characterizes a contrasting strength.
For example, a sentence might say this:

The speech was heavy on rhetoric [or hyperbole or enthusiasm] but light on details.

Or this:

The political party was strong on generalities [or claims or atmosphere] but weak on details.

Or this:

The program was long on indignation [or promises or vision] but short on details.

Or even this:

The coverage is rich in [or dense with or crowded with] general concepts but sparse on details.

I consider all of these wordings to be variations on a single rhetorical form in English—one that uses the trick of laying out a strength and then challenging its usefulness by noting a paired weakness. It may be that some specific wordings using the form rise to the level of idioms, due to being used so frequently. The most likely candidates in this regard, I think, are "heavy on Y but light on Z" and "strong on Y but weak on Z."
But the phrase "sparse on details" doesn't require the counterweight of (for example) "crowded with rhetorical flourishes" to function quite well in an English sentence; it just needs a setting where the thing being examined and described can reasonably be characterized as lacking in detail. In such a situation the phrase "sparse on details" doesn't seem to me to rise to the level of an idiom. It simply observes that details are few and far between, as one would expect from a literal reading of the word sparse.
On a more granular level, though, English does seem to strongly prefer the choice of on as the preposition in phrases of the form "X [preposition] details"—as my preceding examples have illustrated. And if patterns of preposition preference count as "idiomatic," then the preference for "X on details" qualifies.
Answer: As shown by Google Books, these two expressions are both idiomatic:
"sparse on details"
About 774 results
"sparse with details"
About 108 results
in that they are found in large enough numbers in published books to be accepted as regular expressions by the native speakers, but they are not idioms, IMO, for a search on:
"sparse on details" idioms
fails to show in its results any idiom dictionary (my own test for an idiom :-))
Surely, I consider this definition of "idiom" as acceptable:

id·i·om n.
  1. A speech form or an expression of a given language that is peculiar to itself grammatically or cannot be understood from the individual
  meanings of its elements, as in keep tabs on.

Of the two, as one can see, the first is 8x more frequently, a big reason to prefer it.
I can easily read:
sparse on details = sparse in terms of details
However I find
sparse with details
somehow ambiguous. Surely, it doesn't mean:
sparse, with details
because that might be even contradictory:-)

"sparse on details" idiom


What is the moment of inertia really?

Question: Is moment of inertia or second moment of inertia, simply the resistance of a body to rotate it over an axis? What is radius of gyration? What if the axis is via the center of mass or somewhere different? can you give me please an overview of these issues with SIMPLE words, and without nonsense, like maths who nobody will ever remember. I need the SENSE how the brain comprehends these stuff in simple terms.
Comment: You can't say that *an object* has *one* moment of inertia.  Rather an object's moment of inertia also depends on the axis about which you are trying to rotate it.  If for example you rotate a metre stick about one end it will have a higher moment of inertial than if you rotate it about its centre.
Comment: " Is moment of inertia or second moment of inertia, simply the resistance of a body to rotate it over an axis?" Yes, this is exactly it. Just like mass is the "resistance" against acceleration, the moment if inertia is as you say the "resistance" against *angular* acceleration. And it happens to depend on distance to the axis, which is why it is an integral summing up each particle of the object.
Comment: Rotation about a fixed axis yields a single MMOI. But rotation in general (once you move the axis around) involves 6 quantities that are related to 3 principal quantities and 3 orientation angles.
Answer:
simply the resistance of a body to rotate it over an axis?

Gosh, I dislike the word resistance in this context since resistance is, in general, dissipative and, in particular, resistance to rotation would imply that an isolated object that is rotating would eventually stop.
Think of moment of inertia (rotational inertia) about an axis as a measure of an object's opposition to change in rotation (about that axis) not as a resistance to rotation itself.
Answer: Basically, it is how hard it is to spin an object.  If you know what regular inertia is, moment of inertia is the rotation equivalent of it.
Regular inertia is how hard it is to push an object, and only depends on its mass.  For instance, picture an ice rink with a hockey puck.  If it is very light, then it is very easy to push it across.  However, for a very heavy puck, it will be hard to push it across.
Similarly, rotational inertia depends on its mass, but it also depends on its shape and where the it rotates.  Imagine spinning a top. It should spin in nice circles.  If you glue some stuff onto it unevenly, it will be harder to spin because you have changed the shape of it, increasing the moment of inertia.
Imagine a well shaped wheel.  It will rotate nicely.  If you put axle of the wheel somewhere other than the center, it will be harder to turn, because you increased its moment of inertia.
Comment: You are missing the point mentioned by Alfred Centauri that inertia is not resistance to motion but resistance to *change of motion*.
Answer: The radius of gyration is roughly the proportion of the moment of inertia of a body to its mass.  A higher gyradius means that one body will have a larger moment of inertia than a body with a lower gyradius, if both bodies have equal mass.
Answer: The radius of gyration is the distance from the rotation axis you would have to squeeze the entire extended body onto and still maintain the same MMOI.
So take any shape and change it into a thin cylinder around the axis of rotation. If the radius of the cylinder is the radius of gyration then both the shape and the cylinder have the same mass moment of inertia (provided they have the same mass).

What is the moment of inertia really?