Google Cloud instance suspend

Question: Do you try to use free 90 days google cloud platform ?
I try to practice it.
But After I built my instance unbuntu and run it in a few hours. My instance will be suspended by google because violation of Free-trial terms.
So How I can avoid it ?
I want to use my instance for my test lab.
Thanks
Answer: According to Google Cloud Platform Terms of Service in the Suspension section, if Google detects a violation on the Acceptable Use Policy they can suspend the services.

4.1 AUP Violations. If Google becomes aware that Customer's or any Customer End User's use of the Services violates the AUP, Google will give Customer notice of the violation by requesting that Customer correct the violation. If Customer fails to correct the violation within 24 hours of Google's request, then Google may Suspend all or part of Customer's use of the Services until the violation is corrected.

In this link you will find the Google Cloud Platform Acceptable Use Policy:

Customer agrees not to, and not to allow third parties to use the Services:

to violate, or encourage the violation of, the legal rights of others (for example, this may include allowing Customer End Users to infringe or misappropriate the intellectual property rights of others in violation of the Digital Millennium Copyright Act);
to engage in, promote or encourage illegal activity;
for any unlawful, invasive, infringing, defamatory or fraudulent purpose (for example, this may include phishing, creating a pyramid scheme or mirroring a website);
to intentionally distribute viruses, worms, Trojan horses, corrupted files, hoaxes, or other items of a destructive or deceptive nature;
to interfere with the use of the Services, or the equipment used to provide the Services, by customers, authorized resellers, or other authorized users;
to disable, interfere with or circumvent any aspect of the Services;
to generate, distribute, publish or facilitate unsolicited mass email, promotions, advertisings or other solicitations ("spam"); or
to use the Services, or any interfaces provided with the Services, to access any other Google product or service in a manner that violates the terms of service of such other Google product or service.

If you don't know what you are doing wrong, I recommend you contact support.
As you already have a Free trial account you can have chat support through  Console Support Center, also, you can visit the following link for more information.

Google Cloud instance suspend


2014 Jeep SRT 6.4L oil filter was too small - what kind of damage?

Question: What possible damage could my engine incur from having an oil filter installed that is smaller than the suggested size?  I have damage but I'm interested to hear what this forum has to say about it before I confirm my issue.  Please help.
Comment: When you say too small what do you mean? Are you saying that the filter body wasn't big enough for the oil or the connections didn't match?
Comment: An the threads matched but the physical size of the oil filter is much smaller.  Company website shows an appropriate size for a Jeep Patriot or compass.
Comment: What makes you think you have damage from that? How long did you run with the wrong oil filter?
Comment: A smaller oil filter will not damage the engine, if it replaced on the normal schedule, My 2017 car has a filter as small as a lawn tractor, size does not matter if oil changes are done on a regular basis.
Answer: I had buddies back in Highschool that worked at a lube shop.  One story was that someone put the wrong size oil filter on a car and the oil filter blew off of the block.  Luckily, the car was shut down before catastrophic failure.
Don't ask me exactly how, as you would assume that there would be other issues that would attribute to it, and you would figure that an oil pump relief valve would have kept it from happening.  I never heard more, beyond that they put the right size on and the car ran fine.
Take it for the grain of salt, but just a thought.
Answer: What would be more important is was the ABV, if necessary for your engine was present?
What bypass pressure you had vs what you required?
Granted you want as much surface as possible, but the other factors aren't going to be simply time-based issues as the filter media is.
Micron Filtration Beta, albeit to a much less extent as almost no one pays any attention to that.
Those are the issues that you would want to be concerned about, rather than simply size.


MakeTableView error

Question: I'm trying to join a layer with an Excel CSV utilizing the first 6 digits of the column called "concated" and "BBL". but I get the following error:

Runtime error  Traceback (most recent call last):   File "",
line 16, in    File "c:\program files
(x86)\arcgis\desktop10.6\arcpy\arcpy\management.py", line 7554, in
MakeTableView     raise e ExecuteError: ERROR 999998: Unexpected
Error.

import arcpy

    # Define input CSV file and feature layer
    csv_file = r""
    layer = r""

    # Define field names for join
    csv_field = "Concated"
    layer_field = "BBL"

    # Delete existing csv_layer view if it exists
    #if arcpy.Exists("csv_layer"):
    #    arcpy.Delete_management("csv_layer")

    # Create feature layers for both the CSV file and the layer
    csv_layer = arcpy.MakeTableView_management(csv_file, "csv_layer")
    layer_feature = arcpy.MakeFeatureLayer_management(layer, "layer_feature")

    # Extract the first six digits of the "Concated" field in the CSV file
    arcpy.AddField_management(csv_layer, "First6Digits", "LONG")
    arcpy.CalculateField_management(csv_layer, "First6Digits", "int(!Concated![:6])", "PYTHON_9.3")

    # Join the two feature layers based on the extracted digits and the "BBL" field in the layer
    arcpy.AddJoin_management(layer_feature, layer_field, csv_layer, "First6Digits", "KEEP_COMMON")

    # Copy the joined layer to a new feature class
    joined_fc = r""
    arcpy.CopyFeatures_management(layer_feature, joined_fc)

Answer: You do not define the path to your CSV file or layer, you have set them to be empty strings, so that is why the make table view tool fails as your input is nothing. csv_file should be some thing like csv_file =r"c:\temp\mydata.csv". But your code is flawed further on. A CSV file is read only to ArcMap and you attempt to add a field to it. If you need to do that you need to convert your CSV to a proper table that supports proper table functions. You need to read and understand this page.

MakeTableView error


Almost every section of measurable set in $[0,1]^2$ is measurable

Question: Let $A\subseteq[0,1]^2$ be a Lebesgue-measurable set. For $x\in [0,1]$, we define $A_x$ as $\{y:(x,y)\in A\}$. Prove that $A_x$ is measurable for almost all $x\in[0,1]$.  I know that the "almost every'' is indeed needed, since we could have $A=V\times\{0\}$ for $V$ the Vitali set -- then $A$ has outer measure zero, so it is measurable, but $A_0$ is not measurable. This question is similar, but it asks about product measure, while the Lebesgue measure on $[0,1]^2$ is not just the product measure, but completion of it.
Answer: I think the following argument works:
Let $(I\times I,\mathcal L, \lambda_2)$ be the completion of $(I\times I,\mathscr B([0,1])\times \mathscr B([0,1]), \lambda\times \lambda ),$ set  $f=1_A$ and choose a $\mathscr B([0,1])\times \mathscr B([0,1])$- measurable function $g$ such that $g=f\ \text{a.e.}\ \lambda_2.$   Note that the sections $g_x$ are $\mathscr B([0,1])$-measurable.
Then, $h=f-g=0\ $a.e.-$\lambda_2$  and therefore, there is a $B\in \mathscr B([0,1])\times \mathscr B([0,1])$ such that $\left \{ h\neq 0 \right \}\subseteq B$ and $\lambda_2(B)=\lambda \times \lambda (B)=0.$
We have now $0=\lambda \times \lambda (B)=\int_I \lambda (B_x)d\lambda$ so $\lambda(B_x)=0$ for almost all $x\in I.$ But then, $\lambda (\left \{ h\neq 0 \right \}_x)\le \lambda (B_x)=0\Rightarrow A_x=f_x=g_x$ for almost every $x\in I.$
Answer: This is just a more detailed and extended version of the accepted answer. I just want to make sure everything is understood properly.
Let $\lambda_d$ denote the $d$-dimensional Lebesgue measure and $\mathcal{L}_d$ the set of Lebesgue-measurable subsets of $\mathbb{R}^d$. Moreover, let $\mathcal{L}_d\times\mathcal{L}_{d'}$ denote the product $\sigma$-algebra, i.e., the smallest $\sigma$-algebra containing all cartesian products $X\times Y$ for $X\in\mathcal{L}_d$ and $Y\in\mathcal{L}_{d'}$. (That is, $\mathcal{L}_d\times\mathcal{L}_{d'}$ is not just the cartesian product of the two sets.)
Note that $\mathcal{L}_2$ is the completion of the product $\sigma$-algebra $\mathcal{L}_1\times\mathcal{L}_1$, i.e., every set $X\in\mathcal{L}_2$ can be expressed as $X=Y\Delta Z$ for $Y\in\mathcal{L}_1\times\mathcal{L}_1$ and $Z$ a null-set.
We will be using the standard Fubini's theorem for product measure spaces that claims that for $X\in\mathcal{L}_d\times\mathcal{L}_{d'}$, we have $X_x\in\mathcal{L}_{d'}$ for every $x\in\mathbb{R}^d$.
Let $A$ be given and decompose $A=B\Delta C$ for $B\in\mathcal{L}_1\times\mathcal{L}_1$ and $C$ a null-set.
Claim. There exists $D\in\mathcal{L}_1\times\mathcal{L}_1$ such that $C\subseteq D$ and $\lambda_2(D)=0$.
Proof of claim. Since $C$ is null-set, for every $\varepsilon>0$ there exists a countable collection $O_1^\varepsilon, O_2^\varepsilon,\ldots$ of open boxes such that $\sum_{n=1}^\infty |O_n^\varepsilon|\leq\varepsilon$ and $C\subseteq\bigcup_{n=1}^\infty O_n^\varepsilon$. Then we can set $$D=\bigcap_{m=1}^\infty\bigcup_{n=1}^\infty O_n^{1/m},$$ which is an intersection and union of open boxes, hence Borel, hence from $\mathcal{L}_1\times\mathcal{L}_1$.
So by Fubini we have $$0=\int_{[0,1]^2}1_D(x,y)dxy=\int_{[0,1}\left(\int_{[0,1]}1_D(x,y)dy\right)dx=\int_{[0,1]}\lambda_1(D_x)dx.$$
Since $\int f=0$ implies that $f\equiv 0$ almost everywhere, it follows that $\lambda_1(D_x)=0$ for almost every $x\in[0,1]$. Moreover, since $C\subseteq D$, we also have that $\lambda_1(C_x)=0$ for almost every $x\in[0,1]$.
Finally, for almost every $x\in[0,1]$ we have $A_x=B_x\Delta C_x$ with $B_x\in\mathcal{L}_1$ (by Fubini) and $\lambda_1(C_x)=0$, it follows that $A_x$ is Lebesgue measurable (since $\mathcal{L}_1$ is itself a complete measure space).
Comment: I made a couple of small changes to your post. They are supposed to be helpful, but please check that I haven't made any mistakes.
Comment: I think you can just use the outer regularity of Lebesgue measure to say there are open sets $U_n\supseteq C$ s.t. $\lambda_2(U_n)<1/n.$ Then $U=\cap_n U_n$ is Borel, contains $C$ and satisfies $\lambda_2(U)=0.$


Using MySQL partial replication with --replicate-do-table with queries that depend on a non-replicated table

Question: I'm considering using --replicate-do-table on a MySQL slave to only replicate certain tables. When the master is configured to use MIXED mode binary logging, deterministic queries will be written to the binary log using a statement, not the ROW binary data. If this INSERT/UPDATE contains a JOIN on a non-replicated table, however, it could potentially break on the slave.  Is there any way around this or am I totally misunderstanding?
Answer: I think you understand correctly, a query that references tables that aren't replicated will fail on the slave causing replication to halt.  You could create dummy tables on the slave so that the join would succeed but if the results of the query would be affected then the update on the slave would not match the master and the two would diverge.


Automating creation of this chart in Excel 2016

Question:
I am trying to figure out a way to create this graph automatically on Excel and link it to PowerPoint so that when the data in Excel gets refreshed, the PowerPoint chart gets updated as well. Currently, the underlying chart in this photo is a 100% stacked column chart with gap width set to 0 so that there's no space between the bars for different years. However, I have had to manually place the rectangles on top of the stacked column chart and adjust the height and width so that it's spatially accurate (for example, 16% is 16% of the area of the rectangle below). As you can imagine, it's a very long and frustrating process to update the rectangles manually when the underlying data gets updated. Is there a way to automate the creation of such a chart in excel?
I was thinking of creating a Marimekko chart in Excel (which requires manipulations for the data to be in the format desired but can be done) for, let's say, FY18 and rotating it by 90 degrees clockwise. But I'm not sure how to rotate the chart without saving it as an image first. Also, by this method, I'll have to create Marimekko charts for each of the financial years (18, 19, 20 and 21) individually and then place them side by side which might reduce some labor as compared to the method I am currently using but will not be immensely helpful.
Any thoughts on a solution to this problem will be much appreciated. I have been wrapping my head around this for a while now but haven't been able to make much headway.
Answer: have you tried recording a macro and then updating the necessary parts with code?
You can name some ranges in your spreadsheet and then use those to communicate with your macro.


Middle mouse button stopped working

Question: My Dell WM123 wireless mouse's middle button has stopped working. Clicking the scroll wheel in chrome used to open new tab or clicking it on any app pinned to the taskbar used to open another instance of the app. Suddenly it has stopped working.
  I have restarted the laptop and also tried to uninstall & reinstall the mouse drivers. Nothing is working so far. TIA.
Comment: did you checked it in another machine? because this question could be auto answered just with that test.
Answer: I had the same problem with a Logitech G602 mouse. The issue was with hardware button. I opened the mouse (mine has screws hidden behind plastic pads) and put some WD40 on the button just below the wheel. I let it dry a bit, move and used the button several times and added again some WD40 and repeated the click and shake of the button. I reassembled the mouse and voila! the middle click button is working again.
As a comment suggested, you should try your mouse on another PC known to support middle click in order to make sure that the problem comes from your mouse before opening it.

Middle mouse button stopped working


Why and how would I transmit emails via several Mail Transfer Agents?

Question: I read in some Mail-Relay explanation that emails can be delivered from the sender's MTA to the recipient's MTA via more MTAs. How does it work (I thought, the sender's MTA simply determines the recipient's MTA's IP address by using DNS and directly sends the email to it, so no other MTA is involved) and what is the benefit of doing so?
Comment: Find how to view e-mail headers on e-mails you received (may be "view headers", "view source" or other such options depending on what client you use). Then check the headers of multiple e-mails, and count the number of lines starting with "Received:". Each one of those lines is a hop through an MTA. You'll realise that there are often quite a few hops.
Answer: It's VERY common for there to be more than 2 MTAs (1 sender, 1 receiver) in an email transaction. Possible reasons include:

Edge MTAs in a large environment. (Edge servers handle sending/receiving external email, while one or more internal servers handle mail storage and client connectivity.)
Third-party spam/security solutions. (Which then forward the message on to another MTA.)
Forwarders. (Which then forward the message on to another MTA.)

I would bet that multiple MTAs are MORE common that just single MTA configurations nowadays.
Comment: A particular case of Forwarders that was more common in the early days was relaying between networks with different protocols (e.g. from the Internet to UUCP).
Answer: In addition to longnecks answer.
Please also take a look at how  Wikipedia explains the MX record and the backup MX record.
A senders mail server will deliver to a  backup  MX whenever a primary MX can't be reached. The backup MX will accept the mail and hold it in the their queue until the messages either expire or until they can be delivered the primary MX.
This removes the burden of queueing undelivered messages away from the sender and makes the queue managed by the recipient.
Nowadays backup MX records are most likely only necessary for planned maintenance and outages, but in the past it was much more common for systems to be online only intermittently. Domains would often make an agreement with the operators of a mail server with much better connectivity to use their server as the backup (when they couldn't operate their own) or their ISP would provide that as a service. Mail would be queued on the backup MX server (for much longer than most senders did)  and whenever the primary MX server came online, delivery of all queued messages would be triggered (with the ETRN command).  That would allow sites to run their own on-premise mail server, without being online 24x7 (on an expensive dial up connection).


UFW: How to block http requests on another port than 80?

Question: I am running an application on port 7000 which is part of a network. So it has to communicate over port 7000 with all other servers of the network (not LAN, dynamic IPs). It has also a web frontend you can access at http://my.ser.ver.ip:7000 but I want to block the access to the webfront end. How is this possible without block my application at all?
Comment: In your question you say that your application needs to communicate over port 7000 and you also say that you want to block port 7000. You can't have it both ways. Can you please edit your question and clarify? Perhaps you're getting source port and destination port mixed up?
Comment: If I'm reading this correctly, you want to block only traffic specifically using HTTP as an application-level protocol, and not all traffic to port 7000, just HTTP traffic. If that's the case, you've painted yourself into a kind of small corner, and you're getting into content-aware firewalls and DPI. I won't say it's impossible, but I will say it'd probably be a lot easier to simply run HTTP traffic on a different port.
Answer: If i understood your question correctly, you have multiple ways to block access to your application from outside the server.

You can set your application to work only with a 127.0.0.1/8 IP address.
You can block it via iptables.

My best practice is the first option.
Answer: You can block this via .htaacess file. In .htaccess fle you need to allow application only via your public IP address and deny all other IP address. Below i have shared the content which needs to be entered in .htaccess file.
<code> Order deny,allow
 allow from 220.127.116.11  #Your Public IP, only this IP is accessible to application.
 deny from all
</code>
This will sort out the problem for you.
Comment: Where did the OP say they were using Apache?
Comment: Either way, though... From the docs: ["You should avoid using .htaccess files completely if you have access to httpd main server config file. Using .htaccess files slows down your Apache http server. Any directive that you can include in a .htaccess file is better set in a Directory block, as it will have the same effect with better performance."](https://httpd.apache.org/docs/trunk/howto/htaccess.html)
Comment: (Plus, separating data and code is always a good idea.)
Answer: You need to block any access to port 7000, then allow access to port 7000 to only the servers in your network. That way you effectively block the Web UI from being accessed unless you're accessing it from a server inside your network.
HTTP is a protocol (P in HTTP) and runs on port 80. UFW can't block it based on it being a web page or not since it only manages iptables, and only knows it's a web page after a connection has been established.
Depending on which web server you use, you could possible use imvikasmunjal's suggestion. However "block all to access port 7000" and then giving specific access to specific IP's is the best way forward IMO
Comment: Sorry, if I communicated it wrong. The network is not a LAN network. We are talking about servers around the globe and their IP are not always static and may change.

What about using NGINX as a reverse proxy? I tried it by one DigitalOcean tutorial but I were not able to make it work.
Comment: Well, in my opinion then, put the web front-end on port 80 and have it communicate with whatever it needs to on port 7000, then block access with a normal authentication request that a web server has built in


Does Karaite Judaism necessarily reject the Documentary Hypothesis?

Question: If a person believes that the written Torah contains thematic truths as a result of foreknowledge and intent by G-d, but that words of the Torah itself have been influenced by the affairs of mankind (in a manner similar to that put forward in the "documentary hypothesis"), could such a person still be said to have beliefs within Karaite Judaism?
Comment: Related: https://judaism.stackexchange.com/q/56994/8775, although that addresses a rabbanite, rather than Karaite perspective.
Answer: Your title is Does Karaite Judaism necessarily reject the Documentary Hypothesis? Yes it does necessarily reject the DH
The reason for this is that your question as asked would be rejected by both the Karaites and those who follow the Documantary Hypothesis.
The body of your question has the phrase (in a manner similar to that put forward in the "documentary hypothesis")
As I explain, the basic Karaite belief is in the divinity of the Torah as given to Moshe and the basic belief of the DH is that the Torah was written by human authors and editors starting in the time of Solomon and ending in the time of Ezra, with no divine input.
The Karaites believe that the Torah was given to Moshe at Har Sinai and has not been changed. While they accept Neviim and Kesuvim, those sections are not a change to the Torah. The Karaites do not accept the mishnah or talmud because they say that they are a change to the Torah.
Qaraite Judaism

Being a Karaite Jew means we only recognize the Miqra or Tanakh as
  divinely given.

Karaite Korner

Karaism is the original form of Judaism as prescribed by God in the
  Torah. Karaite Judaism rejects later additions to the Tanach (Jewish
  Bible) such as the Rabbinic Oral Law and places the ultimate
  responsibility of interpreting the Bible on each individual. Karaism
  does not reject Biblical interpretation but rather holds every
  interpretation up to the same objective scrutiny regardless of its
  source.

The Karaite "Declaration of Faith"

The Karaite Declaration of Faith, called Tuv Ta'am (after the first
  two words in Hebrew) has been recited in the Karaite Synagogue on High
  Holidays since at least the 13th Century, with an abridged version
  being recited twice daily. The Karaite "Declaration of Faith" consists
  of a series of statements read aloud by the Hazan (cantor). The
  congregation responds to each statement by emphatically shouting Emet!
  meaning "Truth!".

This includes the bullet point that

The Karaite "Declaration of Faith" includes the main principles and
  practices which give Karaism its unique character including:

The truth of the Torah given to Moses.

This means that the part of the statement that says but that words of the Torah itself have been influenced by the affairs of mankind (in a manner similar to that put forward in the "documentary hypothesis") would not be true, since the Torah was not changed since Moses received it.
On the other hand, the Documentary Hypothesis would not accept the part of the statement the written Torah contains thematic truths as a result of foreknowledge and intent by G-d because they would not accept that Hashem gave the written Torah to Moses in any form.
As discussed in articles like The History and Salient Points of the Documentary Hypothesis, this myth pretends that every section of the Torah can be attached to a human author (or authors) with a mythical (human) editor who could not be bothered to insist on consistency. Additionally, this hypothesis insists that different sections were written and edited starting from the beginning of the first temple, to after the time of Ezra.

J, the oldest, begins at Genesis 2:4b and includes large portions of
  Genesis as well as portions of Exodus and Numbers and a few short
  texts in Deuteronomy. It may be dated to the early monarchy
  (Solomonic?) period.
P was produced last, in the exilic period. It begins at Genesis 1:1
  and includes large portions of Genesis, Exodus, and Numbers and all of
  Leviticus. In Genesis, P refers to God as Elohim since, like E, it
  assumes that the divine name Yahweh was first revealed at the exodus
  (Ex 6:3, a P text). It is dominated by genealogies, priestly
  regulations, and a highly stylized manner of narration. P was soon
  redacted into JED by RP. The Pentateuch was thus formed.

The article cited actually goes into great detail as to the presuppositions of the Documentary Hypothesis and why it can be seen that it does not believe in the divine origin of the Torah. However, that would be too long for this question and would be the subject of a post to a different question.


Can a UK indefinite leave to remain sticker in an expired passport be used alongside a valid passport for travelling?

Question: I am a UK national as are all my children, but my wife is not. She does however have an indefinite leave to remain sticker in her old expired passport. Will she still be able to travel, using her old and new passports together?
Answer: The UKVI explains what to do:

You can still use your visa even if your passport's expired, but you can choose to replace it with a biometric residence permit (BRP) if you're in the UK.
You must replace your visa with a BRP if your name or personal details change.
If your passport has expired
  You can still use the valid visa in your expired passport, but you'll need to show your expired passport and your new passport when you're travelling to and from the UK.
If you're in the UK, you can apply for a BRP instead.
If you're outside the UK, you can transfer your visa to your new passport.
Comment: I can confirm this is not merely theoretical.  My wife did it for many years, each time getting a "VIPP" (Visa In Previous Passport) note alongside her entry stamp.
Answer: Your wife can continue to travel with her existing ILR provided she carries both expired and current passports when travelling to and from the UK
(Source:Gov.UK Visas and Immigration)
If you're in the UK you can apply to have a Biometric Residence Permit added to her new passport for a fee of GBP237 (!).
(Same source)
Comment: Thanks for the invaluable advise, it's definitely put my mind at ease. I will be travelling abroad around mid-March and unfortunately the only way to get a BRP between now and March is if I pay £600 on top of the £240 fee for a BRP. I think this is way over the top. I will apply for a BRP when I get back to the UK. I wont need to pay the £600 fee, as I don't mind waiting 6 months for the BRP application to be processed.


Gravity: Quantum Field Force or Entropic Force?

Question: Does the LIGO experiment shed any light on the idea that Gravity is an Entropic Force over a Quantum Field Force?
Comment: Define what you mean? What is an entropic force?
Comment: It is what  Erik Verlinde is proposing, that it is analogous to a thermodynamic like event.  So, no force particle but an equilibrium reached thru entropy.  Hope that helps.
Comment: Was this prompted by Verlinde's new paper, ["Emergent Gravity and the Dark Universe"](https://arxiv.org/pdf/1611.02269v1.pdf)?
Answer: Entropic gravity has been around since Erik Verlinde around 2010, but it does not seem to have found any experimental backup since then. I don't see many papers on entropic gravity either nowadays.
Motl just about totally assassinated (or demolished) Verlinde's theory, and that is probably applicable to Jacobson's similar theory. See Motls's energetic demolishment of entropic gravity at http://motls.blogspot.com/2010/07/many-faces-of-emergence.html
Carroll had a recent paper in 2016 in arxiv that discusses holographic and entropic gravity (Jacobson's version, similar to Verlinde's but not identical), and argues that holographic gravity (using the holographic principle) can be made consistent with quantum field theory and supports various entanglement ideas, but that in entropic gravity it does not seem possible to formulate a consistent definition of entropy. See it at https://arxiv.org/abs/1601.07558.
That is fairly consistent with Motl's earlier blog article that one cannot define entropy in entropic gravity such that a locally Lorentz invariant treatment is possible. Motl argues that it also in fact it runs counter to observed experimental results of neutron double slit interferometers in gravitational fields, that entropic gravity would be inconsistent with the equivalence principle.
Motl argues that other quantum gravity theories like string theory and holographic gravity do not have those inconsistencies, Carroll argues similarly for holographic gravity in significant but not thoroughly mathematical detail.
I have not done a literature review to see all the latest, and a cursory search did not find much, and I've not heard any recent highlighting news for entropic gravity. Not sure how alive it is.
So, as far as LIGO is concerned, it has been found 100% consistent with Einsteins GR, the equivalence principle, and the GR calculations (they not only find the parameters for the gravitational waves, but also if there is any deviation from that predicted through GR computations, and the sigmas to which verified). See the GR tests from LIGO's first detection at
http://www.ligo.org/science/Publication-GW150914TestingGR/
LIGO will do more GR and in fact alternative gravity tests (but I've not seen anything on entropic gravity, maybe others have from LIGO), as it gets more sensitive, and other interferometer arrays get combined into a network. eLISA space borne interferometers in the next decade would be even more sensitive. They expect to be able to probe the extent to which for instance black holes do or do not have 'hair' (I.e., any other conserved properties besides mass, angular momentum and charge), as well as some of the parameters during the dynamic merger phases when the horizons are deformed, and other tests of gravity and GR.
Comment: Sure Ed Yablecki. It's good question and there continue to be proposed alternatives, mainly to try to explain the dark energy and try to make it more quantum friendly, but none that don't reduce to GR in the right limit have had any evidence for them. So far. You never know. The hottest topic has been the holographic correspondence, for a quantum correspondence, but still too many unknowns on it
Comment: Shouldn't you take Verlinde's paper ["Emergent Gravity and the Dark Universe"](https://arxiv.org/pdf/1611.02269v1.pdf) into account, published about 3 days prior to this answer?
Comment: @peter, feel free to do so in formulating an answer. I've not evaluated it yet


MC34063 issue. Switches off every cycle

Question: I am using MC34063 in step down configuration but the converter switches off every cycle. Following are the calculations and specifications:
Vin - 9 to 12V
Vout - 5V
Imax - 0.3A
Rsc - 0.36 ohms
L - 47uH 1.6A
Ct - 270pf
I have tried reducing the current limit resistor value (Rsc), but it didn't help. The usable current is below the designed rated current. I have attached an oscilloscope image showing the output voltage ripple on channel-1 and switching transistor emitter (pin-2 of MC34063A) voltage on channel-2.
Note that the transistor switches off completely causing a low frequency ripple in the output voltage which is unnecessary. Kindly help.
Comment: Its possible that you didnt correctly choose the feedback resistors. What values did you choose?
Comment: please show circuit
Comment: @Golaž The feedback resistors values are correct since I am getting DC output as 5V, but the OFF period and AC ripple is my concern
Comment: @markrages Added the circuit and its calculations
Comment: what are you powering the circuit with?  please add a photograph of the circuit that you built.
Comment: @markrages Using 3 cell li-ion battery(12.6V 2300mAh) to power the circuit
Comment: When you selected an inductor did you account for the fact that the inductance drops off at higher currents - if you look in the datasheets there is usually an I vs L graph, and if you didn't choose wisely you may find the inductance at 0.6A is less than you need.
Comment: Do you have a load on the output? That looks suspiciously like 'burst mode' operation where the output voltage is rising until it exceeds the feedback reference and the switch is shut down until the feedback is back within normal range.
Answer: Turns out that since it is a switching regulator, it switches OFF completely when the output voltage is more than what it is designed for which is exactly what I don't want. I have shifted my design to MC34166 which is a PWM controlled DC-DC converter and everything seems to be working fine. I am getting an output voltage ripple of 10-15 mV peak to peak @ 5 V o/p and no such 10 Hz ripple.

MC34063 issue. Switches off every cycle


Coca Cola on Pesach

Question: Yabia Omer writes that Citric Acid isn't a issue on Pesach. Does that deem Coca Cola Kosher for Passover even without a hechsher as a Sefardi?
Answer: [this was written before the OP edited his question and made it sefardi-specific, I will leave it up for Ashkenazim interested in the question]
For Ashkenazim, the problem with regular Coca Cola is not just the question of the citric acid but rather the high-fructose corn syrup. See here for instance

In its year-round formula, Coca-Cola uses high-fructose corn syrup for
  sweetness. But for Ashkenazim — Jews of Eastern European descent —
  corn and corn-based products are forbidden during Passover. To satisfy
  the sweet tooth of Jews who strictly observe Passover, Coca-Cola
  substituted cane sugar for corn syrup.

Or see here which focuses on the fact that some non-Jews prefer Pesach Coke

During Passover, Jews are forbidden to eat a category of grains known
  as kitniot, which includes corn. The Ashkenazi rabbis who came up with
  this stricture many centuries ago probably didn't foresee how their
  edict would collide with the invention of high fructose corn syrup
  [...] the end result today is that there are all sorts of
  HFCS-sweetened products that are kosher for most of the year but are
  not kosher during Passover. In some cases, special Passover editions
  of these products—sweetened with cane sugar, which is
  Passover-sanctioned, instead of HFCS—appear on the market in the weeks
  leading up to the holiday.
Comment: Note even for Ashkenazim the corn syrup in the Coca Cola may be Batel if purchased before Pesach.
Comment: Also citric acid could very well be a problem as it is often derived from wheat
Comment: mbloch you haven't cited any support for "For Ashkenazim, the problem with regular Coca Cola is not the citric acid" which is the only part of this which remotely addresses the question.
Comment: Is this a question for a Rav? It doesn't fit to this forum?
Comment: The Conservative Rabbis just declared that it's okay to eat corn on Pesach.
Answer: According to Rav Yitzchak Abadi, coca cola is inherently kosher for Sephardim and Ashkenazim during Passover without a hecsher according to halakha.
His responses are as follows:

Questioner:   Is it permitted to drink plain coca cola on Pesach?
Rabbi Abadi: Yes

Source: http://kashrut.org/forum/viewpost.asp?mid=56956&highlight=coca%20cola

Questioner: What's going on here? (copied from a Jerusalem Post
  article)
"Kosher for Passover Coca-Cola has been barred from California.
California's new state laws on toxic chemicals are keeping kosher for
  Passover Coke out of the state, a company spokesman told the San
  Gabriel Valley Tribune. Related:
Coke was required to change the way it manufactures caramel due to the
  high levels of the chemical 4-methylimidazole, or 4-MEI, which
  California has listed as a carcinogen under its new guidelines. The
  manufacturing changes in California affected the kosher for Passover
  status of the cola, according to reports.
The company expects to offer the Kosher for Passover variety of coca
  cola in California by 2013, the newspaper reported citing the company
  spokesman.
The Passover version of Coke uses sugar in place of corn syrup, which
  is not kosher for Passover for Ashkenazi Jews. Some kosher stores in
  California carried limited amounts of kosher for Passover Coke, which
  bears a yellow cap, imported from other states. "
Thanks again and moed tov.
Michael
Rabbi Abadi:  It would be Halachically permitted for Ashkenazim, but
  they choose too be Machmir

Source: http://kashrut.org/forum/viewpost.asp?mid=51992&highlight=coca%20cola

Questioner: ...why is it that they produce a special Peasach Coke (it
  tastes awful :) if the regular one is okay? Thanks for all you help.
Rabbi Badi: It is a business decision

Source: http://kashrut.org/forum/viewpost.asp?mid=51660&highlight=coca%20cola
Comment: Worth noting that R Abadi is known for being incredibly lenient about supervision requirements in general, so this response isn't necessarily indicative of how most rabbis would rule.

Coca Cola on Pesach


Get global keyboard input with Java

Question: How can I get what is being inputed in any program outside my java program.. Is there a way ?
For example, I'm running my java program then I start typing in notepad, and I can see with my java program what is being typed.
Answer: The term you should looking for is Keyboard hooks, here is example using WinApi http://www.codeproject.com/KB/DLL/keyboardhook.aspx
Answer: You cannot do this in pure Java.  At some point, it will involve talking to an external application or a native library, and will be platform specific in either case.
Answer: There is a library to handle native keyboard and mouse control:
http://code.google.com/p/jnativehook/

Get global keyboard input with Java


Negative work enviroment

Question: I came to Australia 6 years ago. After getting my second master's degree and PR in Australia, I started looking for a professional job but I ended up working in supermarket. Finally I could find a related part time job in a foreign engineering company(not Australian) . It was not the best place to work but I was happy for working there and I had good colleagues . The company was small and could not afford paying for training lessons. I decided to pay the fees by myself and attended several training lessons. Last Jun, my contract was not extended (because they could not get a new project). After a month, I could find a new job in a big company. I was very happy and enthusiastic. but I were not welcomed. The senior engineer which I am working with is from the same nationality as my manager and started working for the company 1 week before me. She is rude, un-supportive,lazy, disorganized and from the first day her attitude was so bad to me. I think she sees me as a threat. I don't get good projects. she is continuously bragging how experienced she is and tell people that i am a graduate. Surprisingly the other team members support and help here a lot. overall, the work environment is negative . what should I do? Should I look for another job and leave this company (I think what she wants) or stay and fight?
Answer: If you don't like where you work, and don't see it changing, you should find a new job, give your notice, then leave.
Answer: Working in a negative environment is not ideal, however should you leave based on someone else's actions and/or attitude to shape the course of how you should make career decisions?
I wouldn't look at it as battle (or fight as you put it), look at it as a social experiment within a professional environment.
You can't change an emotion you don't own. The ability to recognize, own, and shape your own emotions to negativity is the masterful skill for magnifying influence in the workplace, and amplifying your ability to turn ideas into results.
By doing so overtime you would have built an invaluable skill of social influence and leadership that no book or course will ever provide you.
In your case there is a specific individual in mind that comes across as passive aggressive. People who treat others distastefully, normally has some insecurities within their own life so they seek to put others down or demoralise them to make them feel better about themselves.
Master your emotions when receiving a social attack. When they go low road, you go high. In time, people will associate you as a leader and someone that is worth paying attention to. The manager over time will be viewed as insignificant.
Plan to be 10 steps ahead. Visualise how you think a daily scenario may play out. Construct in your mind how are you going to deal within it in a way that is professional and that portrays a leadership figure like presence without putting down the individual. Your colleagues will respect you and your manager will develop a self awareness overtime.

Negative work enviroment


iPod sync issue

Question: I just upgraded my computer from Windows XP to Windows 7.  I upgraded my iPod and when I plug my iPod into my computer I get the message "iTunes Library.ITL cannot be read because it was created by a newer version of iTunes."  What needs to be done so I can sync it with the computer again?
Answer: It's very easy. just go to C:\Users(your username)\Music\iTunes and rename the file iTunes Library.itl to iTunes Library.OLD
..... than Open your iTunes, got to "Help" --> "Check For Update". Once you update iTunes, go back to "C:\Users(your username)\Music\iTunes" rename newly created "iTunes Library.itl" to "iTunes Library.NEW" and your old file, "iTunes Library.OLD" rename back to "iTunes Library.itl".
You will be able to open your iTunes and all Libraries with in.
Source: WikiAnswers

iPod sync issue


Will Android apps be compatible with the Ubuntu Phone OS?

Question: I have heard that there is some similarity in the code used for both Ubuntu and Android programs, but has there been any mention in all the recent publicity over the forthcoming Ubuntu OS for phones, whether or not existing Android apps will be compatible with Ubuntu?
Comment: @EricCarvalho This is asking about Android apps in Ubuntu for Phones not Ubuntu Desktop.
Comment: possible duplicate of [Can I run Android apps on Ubuntu?](http://askubuntu.com/questions/1732/can-i-run-android-apps-on-ubuntu)
Comment: people are installing the desktop chrome on the phone, won't make much of a difference in a bit, that page may lead to a similar solution when xmir and other desktop land for converged phones
Comment: The opposite thing is certainly possible. https://askubuntu.com/q/1332793/124466
Answer: So far, the Ubuntu QML toolkit is just a preview, so there is no definite answer possible.
But Richard Collins, head of Ubuntu mobile products, has stated in an engadget interview:

Q: Since Android is also Linux-based, is there any plan for Ubuntu to
  run Android apps?
A: Many Android developers already use Ubuntu as their desktop OS and
  we have a very close affinity with them. We intend to encourage them
  to make their Android applications run on Ubuntu, but we won't
  engineer any middleware for running Android apps. Developers are
  intelligent and capable enough to make their apps run on our devices.
  We have an active initiative right now to directly help them achieve
  this.

So this makes it pretty clear: the apps should be either web apps or ported to Ubuntu.
Comment: someone should create an app for Ubuntu Touch like Wine, just where you can use android apps instead of windows software :D
Comment: I agree with @Jeggy - I won't use UbuntuOS when I can't do everything I could do previously on my Android
Answer: It may be possible with OpenMobile's Application Compatibility Layer. They have already demonstrated it with Tizen OS and from its site, it is clear that it will be available for Ubuntu too.
Source: OpenMobile ACL for Ubuntu
Comment: http://www.openmobileww.com/#!acl-for-ubuntu/c1sz2
Answer: As previously answered, canonical won't support android apps on ubuntu touch. Their official reasoning is that "native" apps are faster. A point they don't mention is that oracle draged google on a billionaire lawsuit for using java on android (google "google oracle java lawsui"t). It should be pretty simple for ubuntu to support android apps, but it would require the "dalvik vm" which might drag canonical in a lawsuit too big to make it all worth it. However, third parties can, and most probably will port dalvik to ubuntu in order to support android apps, I bet someone will do it right after the official ubuntu touch is released. The problem with all this is that it does not solve the problem of legally runnning apps bought for android. I don't think it should be a problem for free apps though.
Comment: [Now that Oracle severely *lost* that lawsuit](https://en.wikipedia.org/wiki/Oracle_v._Google), using alternative implementations of Java is probably much safer for everyone (including Canonical) than it ever has been before (including before Oracle's acquisition of Sun). *But I am not a lawyer and this is not legal advice. :)* As a separate matter, why would it be illegal to run *an app you have purchased* on a "weird" system? It's not illegal to run properly purchased payware apps on CyanogenMod. (I can think of possible weird licensing restrictions, but that could apply to gratis apps too.)
Comment: As an update: The dalvik VM is being obsoleted by ART, which translates the Java apps into native apps upon installation. Thus, even if it isn't official, I'm positive that once Ubuntu phone devices are established, some hacker will port ART to Ubuntu phone.
Answer: I remember seeing this article a while back.
You can run android apps using Google-Chrome with a few tweaks.
I have not tried it myself.  I found the link and others by googling
"run android apps on ubuntu"
http://www.omgubuntu.co.uk/2014/09/install-android-apps-ubuntu-archon


Backing up all Visual Force pages with Eclipse and Force.com

Question: How could be possible to backup all the Visual Force pages using Force.com Eclipse?
Comment: Usually, I zip the whole project code.                                                         Steps: File > Export.
Select the General > Archive File export wizard.
Select the project(s) to be exported.
Choose the archive file type (ZIP or TAR), and other options.
Enter the archive file name.
Click Finish.
Answer: Authenticate to your org with the Force.com IDE (using your SFDC username/password + security token if applicable), make sure "Visualforce Pages" are included in your local project (I haven't used Eclipse in some time, unsure if VF pages are subscribed by default), create project -> the files for the pages (and other metadata types you specified during setup) will be in your local project directory on your machine.
As an aside, I suggest you check out Mavensmate for Sublime or Welkin Suite, I think you may prefer both over Eclipse.
Comment: So, by using the "Choose Metadata Components -> Pages" am I going to download all the salesforce pages? Thanks in Advance!!
Answer: Using eclipse you can take backup of metadata by creating a project as mentioned in previous answers. But each time when you need to take backup, you have to refresh metadata from server and back it up manually.
Follow the steps below for backup your developed application.

Create new project and select Force.com
Enter username, password,security Token
Select Environment in which you have to take backup e.g Sandbox.

Now Select options which way you have to use for download your data. After that show the list of folder in which you have to find your folder Like Object,Trigger,Classes, Pages etc. Click on each component to fetch data from server into Eclipse.
Note:
If you want to backup meta data then create a new project using eclipse and then use a version control system like git or svn to back it up.
You cannot backup data using eclipse.


How can I access Apache (on VirtualBox guest) from host?

Question: I installed Apache on an Ubuntu VM. When I go into the guest and load up Firefox I can see that Apache is working fine when I browse to localhost.
I would like to access this same page through the host. I've tried using the IP address of the guest but nothing comes up. Ideally I would love to set up my Windows 7 (host) to request http://guestserver.com of the Apache server on the guest. How can I do this?
Comment: I found site which helped me solve it. Below answers are correct but not showing anything about creating virtual adapter in VM. Site I referred is:
https://christophermaier.name/2010/09/01/host-only-networking-with-virtualbox/
Answer: If you need other machines in your physical network to be able to reach your VM (or if the VM needs Internet access), use bridged networking. Otherwise, stick to host-only networking.

Stop your VM and open its settings in the VirtualBox (OSE) Manager
Go to the Network tab
Select the network mode at your choice (bridged networking or host-only) (in the below example, I'm using host-only)
If you want to use bridged networking, you've to select the right network adapter at Name. For wired connections, you'd select something named like eth0. Wireless connections are usually named wlan0 (the numbers may vary)
Save the settings
Start the Ubuntu VM
When up, you can gather the IP address by running:
ifconfig | grep addr

In the below output, 192.168.56.101 is the IP address that can be used in your Win7 host system to access your VM:
eth0  Link encap:Ethernet  HWaddr 08:00:27:70:27:fe
      inet addr:192.168.56.101  Bcast:192.168.56.255  Mask:255.255.255.0
      inet6 addr: fe80::a00:27ff:fe7b:25fe/64 Scope:Link
      inet addr:127.0.0.1  Mask:255.0.0.0
      inet6 addr: ::1/128 Scope:Host

In your windows host system, edit C:\Windows\System32\drivers\etc\hosts as administrator and add a line:
192.168.56.101   guestserver.com

If you've a Ubuntu host system, edit /etc/hosts using sudo nano /etc/hosts
Profit!
Comment: On windows 7/8 host file is here: C:\Windows\System32\drivers\etc\hosts
Comment: ipconfig is not a command on Linux, it's ifconfig. Did you mean that?
Comment: This worked perfectly for host-only networking and I can now access the guest from the host's browser. However with a bridged connection, which I would like, I don't have access to the internet from the guest.
Comment: Enabling two network adapters, one NAT and bridged, allowed me to see and bee seen.
Comment: @begueradj Those steps above apply to bridged networking but some networks do not allow/give you multiple addresses. On my uni, I could not use bridged networking because of that, in those situations I would use NAT with port forwarding instead.
Comment: If anyone can help me out with the bridged connection that would be great, I don't know if I'm doing anything wrong, I just selected bridged and started up the guest, but didn't have any connection to the internet, neither from the host.
Comment: That's weird, perhaps you need to reboot your physical machine? Please note that this Q&A site is for Ubuntu. If you've windows-related questions, visit http://superuser.com/
Comment: Ok thanks, I switched to wireless connection and it works now, I'll restart later and if it doesn't work I'll ask on superuser.com, thanks for your help.
Comment: @drtanz: I forgot about that, see the notes at step 3
Comment: If you really mean ipconfig, then 'config' is not a command on Windows. Where do you run the command in step 6?
Comment: @Max That was a typo, it should be `grep`. An alternative command is just `ip addr`, but definitely not `config`.
Comment: @Max Yes, you are right! I overlooked that one again.
Comment: @Lekensteyn Are the steps you mentioned above valid for the bridged mode also or some change must be done somewhere ?
Comment: On my Debian 8.7 I do not have ifconfig command. I use ip a instead.
Comment: I struggled with this because I got tunnel vision. My bridged adapter was working fine, I forgot to check that my firewall was allowing tcp on 8080...
Answer: In my case, I have a router assigning a static IP to my Host PC.

Set the network adapter as Bridge:
Settings > Network > Adapter 1 (Enable Network Adapter) > Attached to: (Bridge Adapter) > OK

Start the Virtual Machine > log in

Change the VirtualMachine's IP from dynamic to static
sudo nano /etc/network/interfaces

Under The primary network interface change the word dhcp to static
and enter your new static IP or comment the line and add a new one

:
#iface eth0 inet dhcp
iface eth0 inet static
        address 192.168.10.110
        netmask 255.255.255.0
        gateway 192.168.10.1
        network 192.168.10.0
        broadcast 192.168.10.255

Notice my router is working at
xxx.xxx.10.x
and yours could be at
xxx.xxx.0.x
or
xxx.xxx.1.x
or some else.
After you do that, you can have internet conection in both host and guest machine, and type that static IP in your web browser to check you apache server.
Comment: I forgot to say you have to make sure your /etc/hostname is properly configured this way:

`nameserver [your_isp_primary_dns] ` and
`nameserver [your_isp_secondary_dns]`
Answer: Instead of trying to set the adapters to Bridged or Host Only Network Adapter, you can try Port forwarding under Firewall/ Other ports, with your port no set to tcp and udp connections.
Comment: This is by far the easiest option for just a web server. Leave your guest networking as NAT, and forward any ports you need onto your host. Simple. The bonus is you still have access to all your networks from the guest. When you bridge you only have access to the bridged network.
Answer: The accepted answer did not work for me (I installed virutalbox inside ubuntu 12.04 LTSand inside virtualbox I installed ubuntu 14.04 LTS Server). I just swapped the network settings for Adapter1 and Adapter2 i.e. setting up Adapter1 for "bridged networing" and Adapter2 for "NAT" and it started working.
Comment: After hours of reading and trying every other solution I could find online, this idea of yours worked like a charm. Thank you so much for writing it! Using Ubuntu 18.04 as host and guest.
Comment: This was useful, but switch the adapter order so the guest uses NAT by default and be able to connect to the internet.
Comment: This actually worked for me. I'm trying to access a Windows VM from within a Mac Host.
Answer: If you cant connect over ip you're not likely to have any success with dns names on a default apache install.
check the network settings of the virtual host, I always putt it to bridged to it can be accessed throughout the entire network.
Comment: I set it to bridged but now the guest doesn't connect to the internet.
Comment: do you get an IP in the quest OS? I usually set up multiple NIC's to match all my physical NIC's.

Can you perhaps dump your ifconfig from the quest and host
Comment: When I'm working with wireless it works but with cable no, here are some screenshots showing my config:
http://imageshack.us/photo/my-images/832/guestr.png/
http://imageshack.us/photo/my-images/846/virtualbox.png/
http://imageshack.us/photo/my-images/9/hostwin7.png/
Comment: any help on this please?
Comment: it looks like your computer is directly connected to the internet and that may be the reason why your client isn't getting a IP (v4)
Comment: my computer connects to the router and then to the internet. Is there anything I can do to make the guest user be able to connect?
Comment: are you sure it's a router (with NAT)? and not a modem?
Comment: it's a modem actually sorry
Comment: so it is impossible to connect my virtualbox guest to the internet when my host is directly connected to the modem?
Comment: if you configure it to NAT it would be but I dont think your ISP will give you 2 IP's so it wouldn't be possible to do that with bridged settings.
Answer: If you only need a specific port (Say if you are running a web application like Jetty or Tomcat) just do:
Settings -> Network -> Set one of the adapters as NAT -> Press 'Port forwarding' -> Set the relevant host and guest port.
Once you save, You could just go from your local machine to localhost:hostport and it'll be redirect to the virtual box relevant port and you are done.
Answer: In bridged mode, if your host uses a static IP address, you should manually config your guest IP in the same range with the host IP. Otherwise, the guest will not be automatically allocated with a valid IP address. HTH.
Answer: Lekensteyn's answer is right.  But if you are in a corporate environment, you might have to disable the proxy server for your guest's IP address.  For example, if you are using Mozilla Firefox on your Host machine and you are trying to access 192.168.56.101/ on the guest, you need to go to Firefox's Tools->Options->Advanced->Network->Settings and use "No Proxy" or "No Proxy For ->  192.168.56.101".
Answer: If you need to access a guest which gets different IP due to use of DHCP, I suggest accessing via it's hostname. However accessing via hostname when the host is Windows might require an extra tool.
The following text was copied from my own answer at superuser.com.:
I suggest you use Multicast DNS to fix this.
Ubuntu is using this by default via Avahi.
The Windows host needs an Avahi-client for it to discover other Avahi-services. If your host already uses some Apple software this is probably already there via a service called Bonjour. However, if this is not already installed then a small version of Bonjour is available for download here: Bonjour Print Services. After installation you should be able to access your guest via .local.
Note: The mDNS system seem to use the .local postfix by default. So, if your hostname is "dev.myapp.com", then the actual hostname will be "dev.myapp.com.local".
Answer: i solved the same problem after search a lot and read a lot of message in the next form:

Mount a Virtual Machine in Virtual Box 6.1 with an empty versión of Ubuntu Server 16.04, 2GB RAM and one CPU. The host Machine is Windows 7 conected to a router. I've a public IP, and configured mi Router vía IP Forwarding and open port 80 for the local IP of my host machine: 192.168.xx.xx.

Then in Virtual Box, go to Tools->Preferences -> Network ->Add New NAT Network. Then Edit this new NAT Netw. -> Name = "NatNetwork". Then  Click in Forward Ports -> IPv 4 -> Rule 1; TCP; Host IP 192.168.xx.x (the local IP of the Host computer); Host Port = 80; Guest IP = 10.0.2.xx (it's the IP of my guest ubuntu server, what i'm seeing vía $ifconfig from console); Guest Port = 80. Then click in ACEPT.

In Virtual Machine (Ubuntu in my case) go to Configuration -> LAN Configuration: Conected to: RedNat; Name = "NatNetwork" (select the Nat Netw. what created in 2).

Next i RUN my guest machine (Ubuntu Server 16).

In the console i installed Apache2 follow the steps in https://www.digitalocean.com/community/tutorials/como-instalar-linux-apache-mysql-php-lamp-en-ubuntu-16-04-es

When apache2 is installed i can view my Apache Server via $ curl 10.0.2.xx (local ip of my guest machine) and the same Apache Server via Chrome in my Host Machine in the local IP 192.168.xx.xx and the same Apache Server in my public IP (because i've already configured my router for IP Forwarding).
Answer: If you are using the Bridged connection , allow the http services in the firewalld can help you to access the server page.
Comment: Not sure how this answer is different from the one accepted 9 years 10 months ago …


Left edge mouse hoover doesn't bring up Unity menu when fullscreened

Question: When I have an app full-screened in 11.10, hoovering my mouse on the left edge doesn't bring up Unity menu. I have three 11.10 computers and this is only happening on the dual-screen twin-viewed Nvidia box. Any ideas what's wrong?
Answer: I had this too from an upgrade but it wasn't related to nvidia. The resolution was to start 'ccsm' (Compizconfig settings manager), go to desktop, Unity plugin, and select "Dodge active window" next to "Hide Launcher".
Comment: That worked but I had to restart X after changing the setting - Thanks.
Comment: It actually looks like I just needed to change the "Hide Launcher" setting. I was able to change it back to "Dodge Windows" once it was working.
Answer: I found rebooting fixes the issue. I am not using multiple monitors, I have it running on a laptop.
When this happens the Launcher IS actually appearing, but doing so behind the other windows. I can actually see it behind my partially transparent terminal window. I can see is slide out and go back away.
The other weird thing is this: It thinks it is in front. I can hover over an apps icon, and see the name appear (back there behind the terminal) and I can even click on one and launch the app.
Comment: Oh, and when this happens, the alt-tab switcher wont come to the front either.


Is energy conserved in general relativity? Does $\nabla_aT^{ab}_{\rm matter}=0$ represent the conservation of energy and momentum?

Question:
For example, the radiation dominated cosmology, the energy density of radiation is proportional to $a^{-4}$ and the volume is proportional to $a^3$, where $a$ is the scale factor. So the total energy of radiation is propotional to $a^{-1}$. So where is the loss of energy of radiation? Is it because the gravitational field has the energy?
Does $\nabla_aT^{ab}_{\rm matter}=0$ represent the conservation of energy and momentum of matter field in GR?
Comment: In a word, yes.
Comment: possible duplicate of [Energy conservation in General Relativity](http://physics.stackexchange.com/q/2597/)
Comment: In a word, no. -
Comment: @SeanD But how can you explain the radiation dominated cosmology? It is a very easy solution of GR. What's wrong with it?
Answer: After taking a look at the answer by Jim, I am not sure in my knowledge at the moment. However, lets try to figure out the details. I claim, that energy-momentum tensor of matter in GR is not conserved by itself since matter always interacts with gravitational field and the total energy should be taken into account instead.
Vanishing of the covariant divergence $\nabla_a T^{ab}=0$ exactly reflects this feature. Consider this equation integrated over a 4-dimensional volume
\begin{equation}
\begin{aligned}
0=&\int_V d^4x \sqrt{-g}\;\nabla_a T^{ab}=\int_V d^4x \nabla_a(\sqrt{-g}\; T^{ab})=\int_V d^4x \partial_a(\sqrt{-g}\; T^{ab})+\ldots\\
=&\int_{\partial V} d\Sigma_a T^{ab}+\ldots,
\end{aligned}
\end{equation}
where dots represent whatever Christoffel symbols appear there. Hence, we see, that if we choose the surface $\partial V$ in the usual way when only its $x^0=const$ parts contribute to the integral we will get the usual conservation law deformed by the connection terms
\begin{equation}
0=P^b(x^0=t_2)-P^b(x^0=t_1)+\dots.
\end{equation}
So, since the difference of 4-momentum at different time does not vanish, the energy momentum tensor of matter is not conserved by itself.
However, if we take into account the contribution from gravity that is calculated in the usual way
\begin{equation}
T^{grav}_{ab}=\frac{1}{\sqrt{-g}}\frac{\delta S_{EH}}{\delta g^{ab}}=R_{ab}-\frac12g_{ab}R,
\end{equation}
we see the well known feature of GR that the total energy-momentum tensor vanishes due to the Einstein equations
\begin{equation}
T_{ab}+T_{ab}^{grav}=0.
\end{equation}
That is kind of obvious, because the total energy momentum tensor is obtained by variation of the total action wrt $g_{ab}$ and therefore gives exactly EOM for gravitational field with a source.
It seems, that the loss of energy of radiation goes into energy of the gravitational field. In addition, you may read the 2 volume of Landau-Lofshitz to find out how people define energy-momentum pseudo-tensor of gravitational field that does not cancel the matter energy-momentum tensor and therefore is more useful for some applications.
Comment: Thanks. I'm a beginer of GR, but I listened that the energy of gravtiy is not local and have no density of energy. So why is there a energy-momentum tensor of gravity?
Comment: I can always formally apply the rule $T_{ab}=(-g)^{-1/2}\delta S/\delta g^{ab}$ to the Einstein-Hilbert action. The point is, that this rule always gives the symmetric energy-momentum tensor for matter fields. However, for gravity it obviously gives just EOM and hence vanishes. That is to say that energy-momentum tensor for gravity is not defined. At least in this simple way.
Comment: It is right that the equation $\nabla_aT^{ab}=0$ only describes the energy of the matter fields and you need to include gravity to get the full conservation law. However the full expression for energy including gravity is not given by simply varying the metric as you suggest. The required expression from Noether's theorem is different and does not give something equal to zero. The Landau-Lifshitz method is one valid approach but there are better ways that do not need pseudo-tensors.
Comment: That's true, I agree. I meant the usual prescription, that suggests to vary by metric. Certainly, there should be a way to get something non-trivial instead of $T^{ab}_{full}=0$, however I know only the LL approach.
Answer: $\nabla T=0 $ is not a conservation law. You are not considering the energy of the gravitational field in this way.
If you do the calculation you find something like $\partial_{\nu} (\sqrt{-g} T^{\mu \nu}) \neq  0 $, so you can't define a conserved charge like $P^{\mu}= \int \sqrt{-g} d^4x T^{\mu0} $.
To account for the gravitational scalar field you could construct a pseudotensor, but this is not satisfactory. Anyway, in some cases you have symmetries that allow you to have conserved quantities.
For the energy loss due to cosmological redshift see here: redshift
EDIT: I add something due to comments. Going from curved space to a local inertial frame of course you have $\nabla T=0 \rightarrow \partial T=0$ and the latter IS a conservation law. But not in general.
In a generic dynamical spacetime the energy is indeed not conserved.
References: Hartle, Gravity, pag. 482 cap. 22 (Local Cons. of En-Momentum in Curved Space). See in particular the example on FRW cosmology that nicely answer the initial question.
Comment: The stress-energy *tensor* is conserved. $\nabla_{\nu}T^{\mu\nu}=0$ The non-gravitational energy and momentum are not always conserved globally in general relativity, which corresponds to a non-zero covariant divergence of the stress-energy *pseudotensor*. And what Kyle refers to is that there is always a way to express this pseudotensor such that it is conserved locally. This means non-gravitational energy-momentum conservation laws apply locally. But $T^{\mu\nu}$ (the tensor, not the pseudotensor) includes gravitational energy-momentum and is still conserved globally.
Comment: I've looked through a few books just now (Crowell's *GR*, Franklin's *Advanced Mech & GR*, and Wald's *GR*) and all three say that $\nabla_\nu T^{\mu\nu}$ is a conservation law. Now, all three *do* state that this would be a *local* conservation law and not a *global* one. Perhaps this is the point you are trying to make?
Answer: The energy of radiation falls off like $a^{-1}$ because space is expanding. As space expands, the peaks of an electromagnetic wave expand with it, which makes them get farther apart. This means the wavelength of radiation increases as space expands, thus the frequency decreases. Since energy is $E=h\nu$, if the frequency decreases proportional to $a^{-1}$, then the energy also falls off like $a^{-1}$. This is called cosmological redshift.
Also, as mentioned in the comments, $\nabla_{\mu}T^{\mu}_{~\nu}=0$ means that the energy-momentum tensor is conserved. It is the GR equivalent of the conservation of energy and the conservation of momentum laws.
Comment: I disagree on the conservation argument for $\nabla T$. See my answer.
Comment: @Rexcirus I'm saying that $\nabla T$ is the GR equivalent; the analog of the classical energy-momentum conservation laws. I don't want that interpreted as me saying it means non-gravitational energy-momentum conservation laws are valid, which they aren't globally.


How should a painted wall be prepared before being tiled?

Question: I want to apply tiles to a kitchen/bathroom wall. The surface is clean and freshly painted. Should the surface be prepared before being tiled, or will the tiles adhere properly to the painted surface?
Comment: As a matter of opinion, if you are talking about ceramic tile, not peel and stick vinyl junk, you have on the one hand: "here's this wall I want to tile" and on the other hand "Here's a lot of money for tile and (mortar/mastic) and grout and sealer, so saving less than a buck a square foot by not using backerboard as the best available tile substrate is putting a lot of investment at risk." Your call, but I know what my call is in that case. The result is no more reliable than the foundation it's built on.
Comment: @Ecnerwal - I agree with everything you said.  But many people and builders still get away with mounting wall tiles directly to sheetrock, either regular or the green (for damp locations) variety.  I had a master bath built that way and except for in the shower (where they should have used cement backer board), the walls were still fine after 20 years.
Answer: Obviously the tiles can adhere no better than the paint is adhering to the wall.  So if there is any peeling you should remove the paint first.
In kitchens and bathrooms semi-gloss or gloss paint is often used.  The tile may not adhere to these as well as to other paints.  Usually washing with a product like TSP (tri-sodium phosphate) which is a super strong soap will rough the surface up pretty well.
In all cases, however, you should read and follow the tile adhesive manufacturer's recommendations regarding wall preparation.  The specific brand you are using may have different requirements.


Encryption size for DKIM Keys

Question: I'm trying to determine what level of encryption salesforce supports for DKIM keys? In sum, when Salesforce generates a DKIM key, is it using 1024 bit encryption or 2048 bit encryption?
Answer: It is using 1024 bits as of today, February 6th 2019. Keys are rotated often though.
Comment: Please include a link to the source for your answer. See [answer]
Answer: The salesforce documentation does not explicitly describes the DKIM RSA key size, but the options are visible when creating a new key:
it is either 1024-bit or 2048-bit (attached screenshot for reference)
Take note of following recommendation, which is also mentioned in salesforce documentation in above link and setup page when creating a new key:
Consider industry-specific security regulations or email recipient limitations when chosing a RSA key size. Some regulations, such as the Federal Information Processing Standard (FIPS), require specific key sizes.

Encryption size for DKIM Keys


resetting the root password in linux

Question: How do I reset the root password in fedora ? Is there any way out ? I have googled a lot but couldn't find any useful result.
Comment: Do you just want to reset the password or do you not have it to begin with?
Comment: @MaQleod reset the password
Answer: the Fedora documentation gives Information on how to reset the root password.
You can also use this more general approach here with init=/bin/bash which works
on about any distro.
This is from the Ubuntu documentation:

Reboot your computer
Press SHIFT or ESC at the grub prompt (as earlier).
Select your image.
Highlight the line that begins kernel and press 'e' to edit
Go to the very end of the line, change the ro to rw and add init=/bin/bash

press enter, then press b to boot your system.
Your system will boot up to a passwordless root shell.

Type in passwd username
Set your password.
Type in reboot

This should work,too
Answer:  With sudo access:
When you at least have sudo access to the machine you can use sudo bash to aquire a root shell and passwd afterwards.
 With chroot:
Another way would be to boot from a LiveCD (or USB Stick with a live System). Then you have to mount your system partitions. At least the ones containing /etc and the location of passwd, probably /bin check with which passwd.
Afterwards you chroot into that directory.
 mount /dev/sda1 /mnt/system
 mount /dev/sda2 /mnt/system/etc
 chroot /mnt/system /bin/bash

Now you are virtually inside your new environment and can use passwd. Maybe you have to update your environment with hash -r before.
Answer: This works in debian distros, should work in Fedora I think (assuming you have sudo privs)

sudo passwd root

type and verify the new password and done.

resetting the root password in linux


opening jar file with admin privilege

Question: I am getting this exception when i open jar file using cmd:
java.io.FileNotFoundException: C:\Windows\System32\drivers\etc\hosts.File (Access is denied)
How can i open jar file with administrator privilege?
Simply double clicking the jar file does not open the jar file.I am using win7 as OS.
Answer: If I understand correctly, you're trying to run java from a command prompt but want admin privileges. In that case, right-click on the "command prompt" and choose "run as administrator", then you can
java -jar myprogram.jar

from the command prompt as before.
However do you really want to allow this program to edit your hosts file? I'd recommend you find out what it's trying to do and make the change manually if you're happy with it.
Answer: If you want to run jar file with admin privileges from console or by double clicking, without explicitly executing it with admin rights Which is most obvious from user's point of view as he might just know how to click and not internal working. Then this is my post answering your quest in simple steps.
Run Java file as Administrator with full privileges

opening jar file with admin privilege


cardano-cli is marked as depricated. Is there a replacement or is that what we are supposed to use?

Question: I see that the cardano-cli is marked as deprecated.
Can someone tell me what is being used in it's place?
If there is no replacement right now then I would like to know that please.
Just trying to direct my time and attention most productively as I try and get oriented to developing on Cardano.
Much thanks
Answer: You are looking at the wrong cardano-cli. It you go to the cardano-node repo, one of the components is the real, current and maintained cardano-cli.
Comment: Thank you @erik-de-castro-lopo, I wonder how it is possible to request that a notice of redirection can be placed in the README.md of the old deprecated repository?
Comment: I will look into it.


What causes double appearance in a single picture?

Question: My kids was taking photos of me and my wife and in one of them I appeared double on each side of my wife. Would you help me understand how it happened. We used a LG phone. Thank you]1
Answer: I am quite sure that the answer is here: Is it possible to get a double exposure with a digital camera?
Your wife's camera phone has a feature called "HDR", where it takes two pictures in quick succession and combines them, in order to better capture both bright and dark areas. It happens quickly, but if the subject (here, it's you) moves quickly, you'll get this kind of doubled image. This also explains the blurred representation of your wife.
Comment: Thank you so much Matt but I have one more question if you would allow. Is this double image possible to happen with two pictures not in quick succession? I am asking because it took time to pass behind my wife's back, switch the car keys from my right hand to the left, put my right arm around my wife's neck and finally pause for the picture. what do you think about photo stitching?  Thank you so much for taking the time and effort to answer. I really appreciate!!!
Comment: I guess it's possible that the camera has a special mode that does that. Were you using the default app? Or, it could be that it took longer than expected due to some software glitch.


Mathematics needed for string theory

Question: I'm interested in cutting edge string theory studied by research physicist. I'm wonder what  mathematics is needed and how far am I in terms of mathematics background needed and how much more mathematics do I need in order to study it properly and reach my goal. My mathematics level is at calculus/Linear algebra.
Comment: You have a very long way to go in terms of math knowledge.
Comment: tensor calculus, group theory, topology, etc. The list is long.
Comment: Why string theory? Even Sheldon knows better.
Comment: Related: https://physics.stackexchange.com/q/5495/2451
Answer: Some years ago, Gerard 't Hooft posted "How to Become a Good Theoretical Physicist", which is more inclusive than just string theory but which you'll probably still find a valuable list.  Here's what he recommends for mathematics:
"Primary Mathematics":

Natural numbers: 1, 2, 3, …
Integers: …, -3, -2, -1, 0, 1, 2, …
Rational numbers (fractions): 1/2, 1/4, 3/4, 2379/1773, …
Real numbers: Sqrt(2) = 1.4142135… , π = 3.14159265… , e = 2.7182818…, …
Complex numbers: $2+3i$, $e^{ia}= \cos(a) + i \sin( a)$, … they are very important!
Set theory: open sets, compact spaces. Topology.  You may be surprised to learn that they do play a role indeed in physics!
Algebraic equations. Approximation techniques. Series expansions: the Taylor series.
Solving equations with complex numbers. Trigonometry: sin(2x)=2sin x cos x, etc.
Infinitesimals. Differentiation. Differentiate basic functions (sin, cos, exp).
Integration. Integrate basic functions, when possible. Differential equations. Linear equations.
The Fourier transformation. The use of complex numbers. Convergence of series.
The complex plane. Cauchy theorems and contour integration (now this is fun).
The Gamma function (enjoy studying its properties).
Gaussian integrals. Probability theory.
Partial differential equations. Dirichlet and Neumann boundary conditions.

"Advanced Mathematics":

Group theory, and the linear representations of groups
Lie group theory
Vectors and tensors
More techniques to solve (partial) differential and integral equations
Extremum principle and approximation techniques based on that
Difference equations
Generating functions
Hilbert spaces
Introduction to the functional integral

There is almost nothing on these lists that's jumps out at me as unnecessary for string theory, with the possible exception of probability theory (and even then, it's so baked in to quantum mechanics that it'd be hard to leave it out.)
Comment: +1 because of how depressing it is to read this list and see how much more one has to learn to be a good physicist.
Comment: Update: I have learnt a lot since, I now have calculus, multivariable calculus, ODE,Group Theory, Real Analysis, Numerical Analysis,Fourier Analysis, Complex Analysis, PDE
Comment: @yswong Have you studied QFT yet?
Answer: It really depends on what you want to research within string theory, but it's one of most mathematically intensive areas within physics. List a mathematical discipline, and chances are you can apply it within string theory.
At a bare minimum, you'll need everything through quantum field theory and general relativity, which includes calculus of variations, complex analysis, group theory, PDEs, path integrals, differential geometry, maybe some topology and anything else I've forgotten. String theory usually builds on this with at the very least a little algebraic geometry. If you take cues from people on the nLab, category theory can be big in string theory. Pick any combination of differential/algebraic and geometry/topology and it will be useful in string theory. Number theory as well.
Pick some math and learn it and it's hard to go wrong.

Mathematics needed for string theory


Is there a different construction of "the" tensor product of two modules?

Question: It may be a pseudo question. But I still decide to ask. Given two $k$-modules $M$ and $N$,it seems to me that in the literature the tensor product $M\bigotimes_kN$ is always defined as the quotient of the free module generated over the set  $M\times N$ modulo the ideal generated by the bi-linearity relations. But I am curious to see a different construction of $M\bigotimes_kN$ which is of course isomorphic to the one mentioned above.
Comment: Mariano: only if the vector spaces are finite-dimensional.
Comment: Well, you could consider the set of all pairs $(P,B:M\times N\to P)$ where $P$ is a $k$-module and $B$ is bilinear, and then define the tensor product as a certain submodule of the product, over all such pairs,  of all of the modules $P$ (or rather you could use a modified version of this construction that does not violate the rules of set theory).
Comment: You don't only want to construct an object, but also a projection map.  The universal property says any such gadgets doing the right thing will all be isomorphic.  So I am not sure what more you can really ask...
Comment: The tensor product is usually constructed in the manner you mentioned. It is usually defined, on the other hand, via the universal property: briefly, any billinear map $M\times N\to P$ lifts to a unique map $M\otimes N\to P$; this is the universal property, and by this any construction of the tensor product is isomorphic to any other.
Comment: For *vector spaces*, one can construct $V\otimes W$ as the dual space of the vector space of bilinear maps $V\times W\to\text{base field}$.
Comment: For $\mathbb Z$-modules, or abelian groups, it's the dual to the space of bilinear maps $M \times N \to S^1$.
Comment: For finite-dimensional vector spaces, you can also take $Hom(V^{*},W)$ together with the bilinear map $\tau$ which is $\tau(v,w)(\lambda) := \lambda(v)w$.
Comment: Tom's suggestion works in ZFC if you restrict your pairs to have rank less than any sufficiently large limit ordinal.
Comment: For arbitrary vector spaces, you can take the subspace of the space of bilinear forms $V^*\times W^*\to k$ generated by $v\otimes w$ (defined in the obvious way), $v\in V,w\in W$.
Comment: So far there are two intersecting lines of thought: one is to start a different set theoretic construction directly and the other is to use the tensor-hom adjointness and possibly the double dual isomorphism under finiteness assumption to express the tensor product in a variety of different ways. Both supplement and advance my understanding of $\bigocross$ greatly.
Answer: In my first encounter with the tensor product of modules (in a course on representation theory by prof. Lenstra), it was done in the following spirit:
First, the tensor product $M\otimes _RE$ is defined using the universal property. Next, we prove the following (and other) elementary properties (here I am concentrating on the object and leaving out the morphism):

$M\otimes _RR$ exists, and equals $M$.
'$\otimes$ commutes with $\oplus$': if $(M\otimes E_i)_i$ exist, then $M\otimes \oplus_iE_i$ exists and equals their direct sum.
'$\otimes$ commutes with $coker$ (right-exactness of $M\otimes_R-$)': Let $f:E\to F$ be $R$-linear, and assume $M\otimes_RE$ and $M\otimes_RF$ exist. Then $M\otimes_R coker f$ exists and equals $coker(M\otimes_RE\xrightarrow{1\otimes f}to M\otimes_RF)$

Theorem: The tensor product $M\otimes_RE$ exists.
Proof: Take a generating set S of E, i.e. the natural map $f:R^{(S)}\to E$ is surjective. Next pick a generating set T of ker(f), so the natural map $h:R^{(T)}\to R^{(S)}$ has image ker(f). Now $coker(h)=R^{(S)}/\ker f$ is (isomorphic via f to) $E$.
By property 1 and 2, $M\otimes_RR^{(T)}$ and $M\otimes_RR^{(S)}$ exist. By property 3, we conclude that $M\otimes_RE$ exists.
Remark:  I guess a didactical merit of this approach (compared to the standard construction as the free abelian group on the product modulo bilinear relations) is that it forces you to think and reason in terms of the universal property and exact sequences. I am not sure if this is also the reason my teachers had in mind.
Answer: A rather general definition of tensor products, far beyond the algebraic setup can be found in the arxiv papers 0808.0095, 0807.1436. A recent application to quanta is in the arxiv paper 1203.0412.
Comment: I will look more into the three papers especially the last one. Thank you.


What is the difference between iSpec2200 and S1000D specifications?

Question: I know the iSpec2200 and S1000D are the specifications which are used in the aircraft maintenance manual, I have to know how they actually work in the aviation domain and what is the difference between them.
Answer: I've only worked with S1000D, but what I understand is that they share a common origin in ATA Spec100, with some differences being:
iSpec2200

maintains a focus on "legacy", monolithic publications
scope is more limited to aircraft
specification costs money (https://publications.airlines.org/CommerceProductDetail.aspx?Product=274)

S1000D

focuses on modular data, with concepts such as data modules and the CSDB
scope is more generalized to any product (air, land, sea, etc.)
specification is free (http://public.s1000d.org/Downloads/Pages/S1000DDownloads.aspx)
Comment: Welcome to Av.SE!
Answer: S1000D is the successor of iSpec 2200 since 2012. The standard is now free of charge and can be easily downloaded from S1000D website.
Comment: I'm not doubting you, but I _am_ surprised that an organization went from `iSpec` to just `` in its naming convention. I mean, dropping the "lowercase 'i', uppercase word" thing in the internet age? Whoda thunk it?? (Unless, of course, Apple sued...) Also, it's odd that they went from the numeric `2200` "backwards" to `1000`.  Everything about those two identifiers indicates (to me, at least) that `iSpec2200` is newer than `S1000D`.
Answer: iSpec2200 is ATA 2100 + ATA 100 combined and was a means to make these standards more modern with a new improved numbering system and things like gender-neutral terms.  The ATA 100 is from 1956, and I'm not sure about the genesis of the ATA 2100.  Both were retired in 1999.
The S1000D is based on the iSpec2200 so as to enable a simple back-and-forth transition between the two of them.  The main difference in that the S1000D is embracing a digital future for output to web, mobile, pdf, ...  It is based on the authoring of data modules that are small topic-specific modules that are "specification agnostic" and allows the data to be converted to ATA 2100 if that is required by the customer (such as they have a publishing system that takes ATA documents as input) or to any output format imaginable.
And of course the data modules are combined to form a larger publication.


valuing options

Question: So in my finance textbook I have the following question: T-bills currently yield 5.5 percent. Stock in Nina Manufacturing is currently selling for $70/share. There is no possibility that the stock will be worth less than $65 per share in one year. What is the value of a call option with a $60 exercise price? What is the intrinsic value?
The answer book says that the value is found like this: C0 = $70 – [$60/1.055] = $13.13. I don't understand how this works. Could anyone explain? Thanks!
Answer: Below I will try to explain two most common Binomial Option Pricing Models (BOPM) used.
First of all, BOPM splits time to expiry into N equal sub-periods and assumes that in each period the underlying security price may rise or fall by a known proportion, so the value of an option in any sub-period is a function of its possible values in the following sub period. Therefore the current value of an option is found by working backwards from expiry date through sub-periods to current time.
There is not enough information in the question from your textbook so we may assume that what you are asked to do is to find a value of a call option using just a Single Period BOPM.
Here are two ways of doing this:
First of all let's summarize your information:
Current Share Price (Vs) = $70
Strike or exercise price (X) = $60
Risk-free rate (r) = 5.5% or 0.055
Time to maturity (t) = 12 months
Downward movement in share price for the period (d) = $65 / $70 = 0.928571429
Upward movement in share price for the period (u) = 1/d = 1/0.928571429 = 1.076923077
"u" can be translated to $ multiplying by Vs => 1.076923077 * $70 = $75.38 which is the maximum probable share price in 12 months time. If you need more clarification here - the minimum and maximum future share prices are calculated from stocks past volatility which is a measure of risk. But because your textbook question does not seem to be asking this - you probably don't have to bother too much about it yet.
Intrinsic Value:
Just in case someone reading this is unclear - the Value of an option on maturity is the difference between the exercise (strike) price and the value of a share at the time of the option maturity. This is also called an intrinsic value.
Note that American Option can be exercised prior to it's maturity in this case the intrinsic value it simply the diference between strike price and the underlying share price at the time of an exercise.
But the Value of an option at period 0 (also called option price) is a price you would normally pay in order to buy it. So, say, with a strike of $60 and Share Price of $70 the intrinsic value is $10, whereas if Share Price was $50 the intrinsic value would be $0. The option price or the value of a call option in both cases would be fixed.
So we also need to find intrinsic option values when price falls to the lowest probable and rises to the maximum probable (Vcd and Vcu respectively)
(Vcd) = $65-$60 = $5 (remember if Strike was $70 then Vcd would be $0 because nobody would exercise an option that is out of the money)
(Vcu) = $75.38-$60 = $15.38
1. Setting up a hedge ratio:
h = Vs*(u-d)/(Vcu-Vcd)
h = 70*(1.076923077-0.928571429)/(15.38-5) = 1
That means we have to write (sell) 1 option for each share purchased in order to hedge the risks. You can make a simple calculation to check this, but I'm not going to go into too much detail here as the equestion is not about hedging.
Because this position is risk-free in equilibrium it should pay a risk-free rate (5.5%).
Then, the formula to price an option (Vc) using the hedging approach is:
(Vs-hVc)(e^(rt))=(Vsu-hVcu)
Where (Vc) is the value of the call option, (h) is the hedge ratio, (Vs) - Current Share Price, (Vsu) - highest probable share price, (r) - risk-free rate, (t) - time in years, (Vcu) - value of a call option on maturity at the highest probable share price.
Therefore solving for (Vc):
(70-1*Vc)(e^(0.055*(12/12))) = (75.38-1*15.38) =>
(70-Vc)*1.056540615 = 60 =>
70-Vc = 60/1.056540615 =>
Vc = 70 - (60/1.056540615)
Which is similar to the formula given in your textbook, so I must assume that using 1+r would be simply a very close approximation of the formula above.
Then it is easy to find that Vc = 13.2108911402 ~ $13.21
2. Risk-neutral valuation:
Another way to calculate (Vc) is using a risk-neutral approach.
We first introduce a variable (p) which is a risk-neutral probability of an increase in share price.
p = (e^(r*t)-d)/(u-d)
so in your case:
p = (1.056540615-0.928571429)/(1.076923077-0.928571429) = 0.862607107
Therefore using (p) the (Vc) would be equal:
Vc = [pVcu+(1-p)Vcd]/(e^(rt)) =>
Vc = [(0.862607107*15.38)+(0.137392893*5)]/1.056540615 =>
Vc = 13.2071229185 ~ $13.21
As you can see it is very close to the hedging approach.
I hope this answers your questions.
Also bear in mind that there is much more to the option pricing than this. The most important topics to cover are:

Multi-period BOPM
Accounting for Dividends
Black-Scholes-Merton Option Pricing Model
Comment: Any standard deviation (volatility) would give a chance of less than $65. A stock with a zero standard deviation of zero isn't a real stock, but a mental exercise. Of no use to the real investor. In my opinion.
Comment: It is not a zero volatility stock. Probable Up and Down movements are calculated using standard deviation of course. Simply in this question the values are already given i.e. lower is $65 then we find the upper artificially. In reality one would use stock's historical volatility as you said. So to get an upward movement we calculate: u = e^[(v)*(sqrt(t/n)] , where (v) - standard deviation, (t) - time to expiry, (n) - number of sub-periods, and to find downward movement: d = 1/u ; then Vs times u and Vs times d to find $ values of upper and lower probable limits.
Comment: A bell curve never reaches zero. A standard deviation of  $1, gives a small, but non-zero chance of a $5 move. If you assume a zero chance of this move, how can the STDev be any number greater than zero? Clearly, I'm being dense here.
Comment: Because there is always some probability of an extreme outcome and bell-shaped curve never reaches zero - we never assume a zero chance of any move. SD is measured from historic data (how true or accurate it is and how perfect is the method to evaluate it is another question) so if in the past the stock had a 10% volatility over a single period of, say 30 days, this is generally accepted as a good indicator of the fact that it is highly unlikely that it would move more than that in the next 30 days. Obviously such moves happen and these are the times when people make or lose fortunes.
Comment: "There is no possibility that the stock will be worth less than $65 per share in one year" - from this statement, how do you offer the number to use for volatility?
Comment: @JoeTaxpayer, assume a distribution other than the normal? Not every probability distribution has tails that go on forever.
Comment: True, but I believe BS uses normal distribution.
Answer: Your strike is $60 but you are given the information that spot cannot drop below $65.
The value of a call option in Black Scholes is given by:
S * N(d1) -e^{-rT} * X * N(d2)
You can look up the formula on wikipedia where it includes dividends. In essence, a call option is the difference between the Spot rate and the Present value of your strike X, price with some probability adjustments.
The probability of the underlying expiring above strike is 100% (by design of the question). N(d2) measures that probability. Likewise, N(d1) will also be 1, since you do know that there is no way the price will drop anywhere near your strike. This is only possible if Implied Vol is very low. Either way, given this setup, N(d1) = N(d2) = 1.
That way, you end up with S -e^{-rT}*X which is your solution. The Black Scholes model uses continuous interest rates but that is immaterial here.

valuing options


How to bind wget to download through a specific port?

Question: I'm trying to download a file through wget. But I want to download it through a port which I configured as a proxy.
How can I configure wget to download through a specific port in my computer?
In other words, I want to bind wget to for example "localhost:8080"
Comment: What kind of proxy your special port is configured as? A HTTP proxy, some other protocol proxy, or a generic TCP connection proxy (like SSH port forwarding)?
Comment: I think I'm using socks5 proxy (I'm using Dynamic Forwarding in ssh command)
Comment: 'bind' in sockets is an operation entirely different from and unrelated to using a proxy which is what you want, and the _tag_ 'bind' is for a particular DNS-server _program_ that is not related to either of those. `ssh -D` handles both socks4 and socks5, but 5 is (unsurprisingly) preferred.
Answer: wget supports http, https and ftp proxies. You can use these types of proxies by typing extra arguments,
wget <url> -e use_proxy=yes -e http_proxy=127.0.0.1:8080
wget <url> -e use_proxy=yes -e https_proxy=127.0.0.1:8080
wget <url> -e use_proxy=yes -e ftp_proxy=127.0.0.1:8080

or, you can export them as environment variables.
However, in case of a socks5 proxy, I recommend installing proxychains. It also supports http, https etc. After installation, you should configure it through /etc/proxychains.conf. Then you can use wget as,
proxychains4 wget <url>
Comment: In it's documentation page it writes that proxychains is just for tcp connections: "This program forces any tcp connection made by any given tcp client to follow through proxy (or proxy chain). It is a kind of proxifier." So what about other protocols?