How to sharpen knife with chunk missing?

Question:
Is it better to grind off the whole blade or should I find someone to add metal and then sharpen it again?
Comment: I could be wrong, but my honest thought is to just toss it. If it's a *good* knife, then the composition of metals in the blade may well be different in the body of the knife, so grinding the the current edge off might literally grind off the entire part of the knife meant to keep an edge. For the same reason, I'd think adding metal is a no-go. If it's not a fantastic knife, It's probably worth it just to replace it. Why do you *want* to save it?
Comment: That's a gonner!
Answer: Grinding the blade down that much would potentially change the shape of the blade. Due to the full depth bolster you would have to either try to reshape the bolster as well or create a blade that tapered very differently.
The knife is an Oxo Good Grips 8" chefs knife which sells for around £20. It's difficult to see that either of your options would be as effective as replacing the knife, unless it has sentimental value.
Comment: I'm fairly tolerant of damaged kitchen knives especially as spares, but that would end up in my garden shed (for cutting courgettes off the plant, opening sacks, all sorts of tasks)
Comment: Yeah, the poor thing's had a rough life; the rest of the blade isn't straight either & it's been sharpened on a rock, so the entire profile already needs re-shaping.. Time to put it out of its misery, I think.
Answer: I had the same happen to me because I was in a hurry and cut frozen cheese thus being in the same situation as you.
I brought the knife to a professional to have it sharpened and he did a great job of grinding the blade evenly.  That was 5 years ago and the knife is still serving me well.
He asked 15€ to do the job, but that was a fraction of what a new knife would have cost me.  So if you have the tools and knowledge of doing it yourself: Grind the blade!  Otherwise, bring it to a professional; it's not an easy job!


Does varchar result in performance hit due to data fragmentation?

Question: How are varchar columns handled internally by a database engine?
For a column defined as char(100), the DBMS allocates 100 contiguous bytes on the disk. However, for a column defined as varchar(100), that presumably isn't the case, since the whole point of varchar is to not allocate any more space than required to store the actual data value stored in the column. So, when a user updates a database row containing an empty varchar(100) column to a value consisting of 80 characters for instance, where does the space for that 80 characters get allocated from?
It seems that varchar columns must result in a fair amount of fragmentation of the actual database rows, at least in scenarios where column values are initially inserted as blank or NULL, and then updated later with actual values. Does this fragmentation result in degraded performance on database queries, as opposed to using char type values, where the space for the columns stored in the rows is allocated contiguously? Obviously using varchar results in less disk space than using char, but is there a performance hit when optimizing for query performance, especially for columns whose values are frequently updated after the initial insert?
Answer: You make a lot of assumptions in your question that aren't necessarily true.
The type of the a column in any DBMS tells you nothing at all about the nature of the storage of that data unless the documentation clearly tells you how the data is stored.  IF that's not stated, you don't know how it is stored and the DBMS is free to change the storage mechanism from release to release.
In fact some databases store CHAR fields internally as VARCHAR, while others make a decision about how to the store the column based on the declared size of the column.  Some database store VARCHAR with the other columns, some with BLOB data, and some implement other storage,  Some databases always rewrite the entire row when a column is updated, others don't.  Some pad VARCHARs to allow for limited future updating without relocating the storage.
The DBMS is responsible for figuring out how to store the data and return it to you in a speedy and consistent fashion.  It always amazes me how many people to try out think the database, generally in advance of detecting any performance problem.
Comment: +1: The question also assumes a significant amount of update that expands VARCHAR fields.  Even this may be -- in some applications -- a vanishingly small percentage of rows.
Comment: Thanks for the replies. My basic question was how the DBMS stores variable length data, and the answers have shed light on that for me. The DB in question does have a number of somewhat large columns that are initialy blank on insert and filled in later, so my general concern was how this is handled by the DBMS, and possible performance issues due to hopping around the disk vs using chars.
Comment: @E.  Depends entirely on your DBMS, and it's possible they may not publish that information.  However, most modern DBMSes are aware of issues like data fragmentation and include optimizations to avoid loss of performance.  Unless you detect a performance problem, I'd let the database handle it for you.  (At a guess, I'd imagine that most DBMSes will write the row back over current storage if it fits, or in new storage if it doesn't, freeing the old storage, with more-or-less the same performance in either case).
Answer: The data structures used inside a database engine is far more complex than you are giving it credit for!  Yes, there are issues of fragmentation and issues where updating a varchar with a large value can cause a performance hit, however its difficult to explain /understand what the implications of those issues are without a fuller understanding of the datastructures involved.
For MS Sql server you might want to start with understanding pages - the fundamental unit of storage (see http://msdn.microsoft.com/en-us/library/ms190969.aspx)
In terms of the performance implications of fixes vs variable storage types on performance there are a number of points to consider:

Using variable length columns can improve performance as it allows more rows to fit on a single page, meaning fewer reads
Using variable length columns requires special offset values, and the maintenance of these values requires a slight overhead, however this extra overhead is generally neglible.
Another potential cost is the cost of increasing the size of a column when the page containing that row is nearly full

As you can see, the situation is rather complex - generally speaking however you can trust the database engine to be pretty good at dealing with variable data types and they should be the data type of choice when there may be a significant variance of the length of data held in a column.
At this point I'm also going to recommend the excellent book "Microsoft Sql Server 2008 Internals" for some more insight into how complex things like this really get!
Answer: The answer will depend on the specific DBMS.  For Oracle, it is certainly possible to end up with fragmentation in the form of "chained rows", and that incurs a performance penalty.  However, you can mitigate against that by pre-allocating some empty space in the table blocks to allow for some expansion due to updates.  However, CHAR columns will typically make the table much bigger, which has its own impact on performance.  CHAR also has other issues such as blank-padded comparisons which mean that, in Oracle, use of the CHAR datatype is almost never a good idea.
Answer: Your question is too general because different database engines will have different behavior. If you really need to know this, I suggest that you set up a benchmark to write a large number of records and time it. You would want enough records to take at least an hour to write.
As you suggested, it would be interesting to see what happens if you write insert all the records with an empty string ("") and then update them to have 100 characters that are reasonably random, not just 100 Xs.
If you try this with SQLITE and see no significant difference, then I think it unlikely that the larger database servers, with all the analysis and tuning that goes on, would be worse than SQLITE.
Comment: SQLite is a perfect example of what I was saying in my comment, above, about not knowing the storage mechanism for data.  Under the hood, SQLite doesn't even HAVE typed storage — you can insert VARCHAR-like data into any column type (even INTEGER).
Comment: The question is, does this make any difference to performance? Only a test will tell for sure. For one thing, the software developers may have realised the potential for fragmentation and mitigated it in some way. For another, the extra padding of fixed length chars will likely cause more file I/O, but that too can be mitigated. You need to benchmark the variations in order to know if there is a significant difference.
Answer: This is going to be completely database specific.
I do know that in Oracle, the database will reserve a certain percentage of each block for future updates (The PCTFREE parameter).  For example, if PCTFREE is set to 25%, then a block will only be used for new data until it is 75% full.  By doing that, room is left for rows to grow.  If the row grows such that the 25% reserved space is completely used up, then you do end up with chained rows and a performance penalty.  If you find that a table has a large number of chained rows, you can tune the PCTFREE for that table.  If you have a table which will never have any updates at all, a PCTFREE of zero would make sense
Answer: In SQL Server varchar (except varchar(MAX)) is generally stored together with the rest of the row's data (on the same page if the row's data is < 8KB and on the same extent if it is < 64KB. Only the large data types such as TEXT, NTEXT, IMAGE, VARHCAR(MAX), NVARHCAR(MAX), XML and VARBINARY(MAX) are stored seperately.


Two different mediums can have equal index of refraction?

Question: In other words: given a certain medium, is light's phase velocity unique?
Comment: If we consider the complex refractive index vs. the frequency  then probably the whole function $n(\omega)$ contains a lot information about the medium, with the absorption lines at the resonances etc; maybe gives enough information to uniquely identify the medium.
Answer: Two media can have equal indices of refraction. For example, you could pick the densities of two different gases so as to make their indices of refraction equal. You could do the same thing with different liquids containing properly chosen concentrations of solutes.
Answer: Well it is a very popular, and useful property of some optical glasses used in lens design.  If you look at a glass catalog from say Schott or Hoya, and others, you will be able to find from their data, pairs of glasses, which have the same refractive index (n) at some wavelength (He d line or Na D line) but have different dispersions (V value) or change of index with wavelength.
So you can include a lens in your design, that has that common index, to achieve some property.  But you then split the lens into two (cemented) elements, one from each of the chosen pair.
Since both glasses have the same d index, it doesn't matter at all, what the common cemented surface radius of curvature is, so the common surface is invisible or "buried".
But now if you investigate the total lens properties, as a function of wavelength, for chromatic effects, you find that the common surface radius is a very useful control of chromatic aberrations, with virtually no effect on the monochromatic aberrations.  Well it will affect chromatic variation of monochromatic aberrations, (like spherical, coma, astigmatism, and distortion) but those are higher order aberrations, than the Seidel aberrations.  so the short answer is yes.
Answer: I'd say, given a certain media, light's phase velocity is not unique, because there is aways some dispersion (unless the medium is a vacuum).


Dominated convergence theorem (computing limit)

Question: I need to compute $\displaystyle\lim_{n \rightarrow \infty} \int \frac{\sin (x^n)}{x^2} \, dx$ using Dominated Convergence theorem. I have taken the function $g$ such that $|f_n| \leq g$ , where $f_n =\dfrac{\sin (x^n)}{x^2} $ to be $\dfrac{1}{x^2}$. I am not sure how to proceed forward. Do I need to find another function $f$ s.t. $f_n \rightarrow f $ almost everywhere. If not then what should be my approach?
Comment: Just as a side remark: $g(x) = \frac{1}{x^2}$ is not a good choice for the dominating function as $g$ is not integrable: $$\int g(x) \, dx \geq \int_0^1 g(x) \, dx = \infty.$$
Comment: Sorry, I forgot that g needs to be integrable. Can you suggest any other?
Comment: For example $g(x) := 1$ for $|x| \leq 1$ and $g(x) := \frac{1}{x^2}$, $|x| \geq 1$ does the job. To see that this is a dominating function (for $|x| \leq 1$) use the elementary inequality $|\sin(x)| \leq |x|$ (which follows e.g. directly from the mean value theorem). And are you sure that you have to compute the limit for the integrand $\frac{\sin(x^n)}{x^2}$ and not $\frac{(\sin (x))^n}{x^2}$....?
Comment: Ok. after that should I compute $\displaystyle\lim_{n \rightarrow \infty}  \frac{\sin (x^n)}{x^2} \ = f$ and then compute the integral of $f$ which will give me my answer?
Comment: It is not so clear if the function converges pointwisely at all to any function when $x>1$/
Comment: @JohnMa Actually, it is clear that the function does *not* converge for $|x|>1$ since $\lim_{y \to \infty} \sin(y)$ does not exist.
Answer: I think that you must do some changes before using DCT.
a) Change of variable $u=x^n$. Your integral is now
$$I_n=\int_0^{+\infty}\frac{\sin(x^n)}{x^2}dx=\frac{1}{n}\int_0^{+\infty}\frac{\sin(u)}{u^{1+1/n}} du$$
b) Integration by parts, using $(1-\cos(u))^{\prime}=\sin(u)$ :
$$I_n=\frac{n+1}{n^2}\int_0^{+\infty}\frac{1-\cos(u))}{u^{2+1/n}}du$$
And now you have to use the DCT on $\displaystyle \int_0^{+\infty}\frac{1-\cos(u))}{u^{2+1/n}}du$. Note that $\displaystyle |1-\cos(u)|=2\sin(u/2)^2\leq \frac{u^2}{2}\leq u^2$, and as $n\geq 2$, we have $\displaystyle \frac{1}{u^{1/n}}\leq \frac{1}{\sqrt{u}}$ on $[0,1]$.


Concerning opinion-based/broad questions and alternatives

Question: I understand the need for this, but I feel like it's really a shame that questions seeking opinions from this extremely knowledgeable community are automatically downvoted/closed/put on hold. I think a lot of people deal with large scale projects, and would appreciate being pointed in the right direction by people who have a lot more experience. Internet is very scarce on message boards with helpful and experimented users like Stack Overflow. If not here, where is one supposed to go for direction on a new project?
Comment: Generally such people have colleagues or classmates. You don't do large scale projects alone.
Comment: @SimonBesozzi If you're working on it alone it's almost certainly, by definition, not a large scale project.  A really *large* scale project takes more man-hours to create than a single human's lifespan.
Comment: @Gimby That's a pretty bold assumption. A lot of people prefer working alone, and if they're working with, say, classmates, chances are they're on the same level as them.
Comment: It's like asking _What should I code in C# or VB.NET?_. It's just not answerable and would cause a lot of opinions to blow up on the question. Or _Which database should I use, MySQL, SQL-Server, SQLite, MS Access or Oracle to store my data?_ Nobody can answer that but you.
Comment: I think large is pretty subjective. I think it's relative to the effective work-force. I consider a project that could take a single person 500+ hours to be a large scale project, if done alone. That's not the point of the post though.
Comment: @SimonBesozzi times have changed them, when I was in school people varied in skill level right from day one ranging from people with programming experience to people who picked informatics because they didn't know what else to do. Other than that: what Servy said.
Comment: @Gimby actually you can if you considering building a video game like an RPG a large scale project. not all Indie Devs have friends who can help them
Comment: I have always found it extremely ironic that a site that is run by engineers, developers, and designers has such a HORRIBLE UX  where new users are concerned. I mean, isn't the whole point (or at least one of the main pillars) of web app design to ensure that the user experience is pleasant from START to finish. Show me a first time poster who says their experience was pleasant, and I'll show you a liar. You all know what I'm talking about. I do think this site serves a very valuable purpose, but I wouldn't call it user friendly in any sense of the term.
Answer: Stack Overflow is not a forum where you can discuss about "MySQL vs MongoDB", or other debat dealing with subjective opinions.
Is only deals with questions and answers. That's all.
You can't really answer a question that is too broad (too many answers), or primarily opinion-based. That is why we prefer to close it.
I think the primarily opinion-based flag explain well this, so I quote it:

Many good questions generate some degree of opinion based on expert
  experience, but answers to this question will tend to be almost
  entirely based on opinions, rather than facts, references, or specific
  expertise.

I'm not saying that questions about "MySQL vs MongoDB" are bad, but there are others blogs/forums discussing about this, and it is simply not the purpose of Stack Overflow.
Comment: @Simon it is a catch 22 actually. No other forums have expertise because they allow this type of Q.... stack has that expertise partly because of their quality standard, which blocks this type of Q...
Comment: @SimonBesozzi And that's not a coincidence.  SO is the way that it is precisely *because* of the questions that it allows and doesn't allow.  Experts come to SO to share their expertise because they know that there are going to be quality questions with objectively verifiable answers, rather than random people just shouting their opinions.
Comment: To me, a simple resolution to that issue would be to have another Stack community where users could ask for guidance in specific project. I understand SO might not be the place, but surely there's a way to make use of Stack's users' experience through their opinions
Comment: @SimonBesozzi They tried that.  It ended exactly as you would expect, it was an awful place full of low quality content that nobody wanted to use, so it died.  They've learned from their mistake and aren't planning to repeat it.
Comment: That's the thing though. In all other threads about this issue on Meta, people refer to ''There are other forums to... etc.'', but no one has a concrete example, because none of those small scales forums have the reach and expertise of stack communities.
Comment: I didn't say it was, I meant that all of these other resources don't offer the same level of expertise as Stack.
Comment: But again... the experts that flooded here did so (some of them at least) BECAUSE these questions aren't allowed. Seems like a 'bait n switch' if we suddenly allow thwm
Comment: @SimonBesozzi People want to ask opinionated and broad questions here because this is where the expertise is, not realizing that those types of questions are what actively drive away expertise and lower quality.  By allowing them, you're driving away the very expertise you want to answer them.  It's a self-defeating cycle.


Security -- Subnets

Question: Network Segment Diagram

This is my setup.  Want to use main and remote guest networks ( on different subnets ) for IOT devices and guest wireless access.  The IOT devices only access from internet ( smartphone ).  How much protection do these give my main network, both from IOT devices and from malicious things on my guest's devices?
My setup works well for my needs, but I am concerned about protecting the computers on my main network.
Answer: From other reading here, security is questionable if main computers can be pinged from a computer connected to the different subnets.  Does increase difficulty for malicious intent, but not enough to ensure security.

Security -- Subnets


Movie about underground creatures

Question: I don't remember much about the movie, but I know it came out a while ago.  The most I remember about the plot is an earthquake causes creatures from underground to attack residents of a city hotel. I believe it focuses heavily on a father and son with survivors of the attacks. In the end they make it out of the hotel to find giant crystals coming out of the ground and neighboring buildings under attack.
Comment: https://www.imdb.com/list/ls050510252/ - One of these, presumably. Earthquakes releasing big nasties is a pretty common trope in B-Movies of the 1950s and 60s.
Comment: A look at our [guide](https://scifi.stackexchange.com/tags/story-identification/info) to asking story id questions may be helpful in jogging your memory for more pertinent details.
Comment: When is "a while ago"? Was the film in colour or black&white? What did the creatures look like? What was the budget like? Who were the actors? How old was the father, how old was the son? Where was the mother? Why were they in a hotel? Did they receive help from the outside world?
Comment: If the correct answer is posted, you can accept by clicking on the checkmark by the voting buttons as per the [tour].
Comment: I didn't even notice how old this question was.
Answer: I suspect this is the 2009 film The Blackout as per 2000s Movie about creatures coming from Basement drain of Apartment Building
From this review (bolding mine):

it's Christmas eve and westphalia is under quakes and severe high temperatures with power surges going around the city( Los Angeles that is) . Scientists can't figure it out. There's a Christmas party in a tenement block, and the couples presented are living in the same building - 1 family (man + woman + man's brother + 2 kids boy and girl) , 1 about-to-get-divorced-couple, 1 about-to-get-married-couple, and some random dudes and girls. The newsman tells the power-surges are connected with the temperature and the quakes.
Mom and dad are trying to have fun(in bed) but the kids find them out and they get sent to the basement to bring up their presents. Nasty creature eats their guts.
There's an agoraphobic guy at the 2nd floor, friend with the superintendent and the electrician, and he's a master in discovery channel and electronics and communications. Electrician "Ralph" gets torn to bits. The party is ruined, more creatures come and claim lives. Some guy's brother tries something he saw on TV ("Hey the creatures might be photosensitive" ) but he gets a big head-shot and dies. The little girl is not dead - apparently she managed to survive ( somehow I have no idea ) and she got in a defunct elevator ( again HOW is a big question ). The group manages to kill 2 creatures, find out the main building entrance is blocked and head for the roof. They go through that defunct elevator's shaft and find out the little girl.
The dad and dad's brother end up dead, and tadam: 3 survivors - The mom, the little girl and that agoraphobic fat guy. They get to the roof where they see LA has been torn apart by some nasty volcano-type spikes ( ?!WTF ) that erected from the underground. They start squirting something out from their top (lava probably), and... that's it.. The movie ends. I must say the ending was very stupid. I expected the military or something to grab and save them...like "ye mam we got everythin under control". There's no outcome. The FX were pretty good I must say...

Trailer

Movie about underground creatures


Letter or icon for app icon

Question: Do you guys think a letter (like Vine, tumblr, Facebook, Vimeo) is a better representation of a brand/app than an icon (like SnapChat, Evernote, Twitter, Dropbox)?
Comment: I think it depends.
Comment: Hey @A user this is a really broad question and would definitely depend on the context of the app. There is no right or wrong answer :)
Comment: Actually, brands you mentioned don't have separate symbol and typographical. Would be strange if Facebook or Vimeo would use some symbol for app icon.
Answer: I think depends on strength of a brand.
Icons - images are much more recognizable for eye because they are complex. But thats just visuality.
I don't think just letters are good representation a especially if its a small brand. There is only finite number of letters and their shapes. But for big brands i think it works because... well they are everywhere so you have no problem to remember and recognise them. The simplicity makes them more grand somehow.
Also note, the brands that use just letters almost aways connect strong color with very specific typeface (Klavika that Facebook uses for example).
I don't think its so simple though. Branding can be pretty complicated.
Btw there is great free resource (course) on branding from Wolff Olins - Secred Power of Brands
Answer: Icon is better, that letter like "F" (in facebook) is a icon, mind sees as a image
Comment: Hi there, and welcome to GD! Though we get your general point, I would suggest you edit your question to expand and explain your view, with reason and preferably examples. This site is based on the expectation that people give good, well reasoned answers.

Letter or icon for app icon


Number of binary arrays of length n with k consecutive 1's

Question: What is the number of binary arrays of length $n$ with at least $k$ consecutive $1$'s?
For example, for $n=4$ and $k=2$ we have $0011, 0110, 1100, 0111, 1110, 1111$ so the the number is $6$.
Comment: I suggest migrating this to m.se.
Answer: It's easier to count strings that avoid $k$ consecutive $1$'s. Let $a_n$ be the number of those strings of length $n$. Append a digit at the end, $0$ or $1$. The only "bad" strings thus created are those ending on exactly $k$ consecutive $1$'s (i.e. $1^k$ or $\dots01^k$). Thus,
$$
2a_n=a_{n+1}+a_{n-k}, \qquad n\ge k,
$$
and $a_n=2^n$ for $0\le n\le k-1$, $a_k=2^k-1$, so the generating function $A(x)$ for $a_n$ is
$$
A(x)=\frac{1-x^k}{1-2x+x^{k+1}}.
$$
The number of binary strings containing $k$ consecutive $1$'s is $b_n=2^n-a_n$, so the corresponding generating function is
$$
B(x)=\frac{1}{1-2x}-\frac{1-x^k}{1-2x+x^{k+1}}=\frac{(1-x)x^k}{(1-2x)(1-2x+x^{k+1})}.
$$
Answer: More in general, words of length $n$ with a finite alphabet $A$, that contain (or that avoid, if you like) a given pattern as a factor. The solution of the enumeration problem is given in terms of a rational generating function, which can be easily computed by means of the "autocorrelation polynomial" of the pattern.
Answer: Let $a_n$ be the sought number. Consider the first occurence of $k$ consecutive $1$'s in an array of length $n \geq k$. Either they are the first $k$ bits followed by any sequence of $n - k$ bits, or they are preceded by a $0$ preceded by a sequence of $i \geq 0$ bits that do not contain $k$ consecutive bits, and followed by $n - k - 1 - i$ arbitrary bits. This implies $a_n = 2^{n - k} + \sum_{i = 0}^{n - k - 1}(2^i - a_i)2^{n - k - 1 - i}$. Denote $b_n = a_n \cdot 2^{-n}$, and $f(x) = \sum_{n = 0}^{\infty} b_n x^n$ the o.g.f. of $b_n$. After some standard manipulations we arrive at $f(x) = \frac{x^k (2 - x)}{2^{k + 1}(1 - x)^2 - x^{k + 1}(1 - x)}$, and $a_n$ is $2^n / n!$ times $n$-th term of Taylor expansion of $f$.


Do i need installing antivirus on Windows partition of Mac

Question: I have installed Windows 10 on MacBook Pro with Boot Camp. Now I would like to know if I should also install antivirus on Windows 10, or is all virus protection handled by the Mac?
Answer: Of course, installing an antivirus on your Windows is recommended, but it is not a necessity. Generally, if there was a virus, your mac would not be damaged, as the OS X file format is read only on Windows AFAIK (unless the virus was so well made, that it bypassed this).

or is all virus protection handled by the Mac?

There is no way for that to happen as when you run Windows with BootCamp, then Mac is not even running, and only mounted as a read-only format on Windows. It is almost like running 2 different systems.
Answer: Windows and Mac actually different OS run, so Mac can't handle all service on Windows.
Virus can run in Windows systems in virtual or native install. So you need install Antivirus on Windows systems.
Hopefully that's answer your questions.


Timezone for server

Question: I am building a application where the clients are supposed to pass a datetime field to query the database. But the client will be in different timezones, so how to solve that problem.
Should I make it a point that the client's timezone is used as deafult for each user or the server for every user. And if so than how can I do it?
Answer: generally, the server is setup to run as UTC, which has no daylight saving time, etc, and each user's settings contains their preferred timezone. Then you do the time difference calculation. You DB might have that feature.
Comment: What do you mean my DB will have that feature? I am using MySQL, so where will that feature be?
Comment: @SaranshMohapatra See http://stackoverflow.com/questions/4141611/handling-timezones-in-mysql-without-zoneinfo
Comment: @SaranshMohapatra See also http://stackoverflow.com/questions/1697304/php-mysql-timezone-clarification
Answer: Just use the django timezone feature to get the timezone of the user and to convert it to your local timezone for the db-query.

Timezone for server


Problems installing landscape-server-quickstart

Question: I'm looking into Landscape for managing our ubuntu clients within our business in a more efficient way however I'm running into problems at the first hurdle.
I've installed Ubuntu server 16.04.03 LTS in an ESXi VM and tied the 17.03 quickstart install I'm following the basic instructions: https://landscape.canonical.com/set-up-on-prem
But get the following results:
DERLAND01:~$ sudo apt install landscape-server-quickstart
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 landscape-server-quickstart : Depends: landscape-server (>= 17.03.3-0ubuntu1) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

The server is a plain vanilla install with only an IP address and domain suffix changes.  I've also tried performing sudo apt-get upgrade before I run the apt install but to no avail.
After a few tips from internet searches, I used sudo aptitude install landscape-server-quickstart rather than apt to see if I can get a more detailed output and then get complaints about juju:
The following packages have unmet dependencies:
 juju : Depends: juju-2.0 (>= 1:2.1.2-0ubuntu1~16.04.1~juju1) but it is not going to be installed.
The following actions will resolve these dependencies:

     Keep the following packages at their current version:
1)     juju [Not Installed]
2)     landscape-server [Not Installed]
3)     landscape-server-quickstart [Not Installed]

     Leave the following dependencies unresolved:
4)     landscape-hashids recommends landscape-server

Accept this solution? [Y/n/q/?]

I've also tried installing the latest stable juju from the ppa, but to my understanding juju should already be taken care of by the landscape install.
If I revoke to my VM to post OS install snapshot and run through the process with Landscape 16.06 ppa - everything works fine.  Am I missing something obvious or is something broken?
Any help would be appreciated as I've been going round in circles for hours!
Thanks!
Rich
Comment: OK - problem now resolved.  i386 ISO was used to build the server - now using AMD64 and all is well.
Comment: please post your solution as an answer and accept it, so searcher know that there is a solution
Answer: You must use an amd64 system.
A bit obtusely, but it's documented here:

https://landscape.canonical.com/static/doc/user-guide/ch03.html

You can install Landscape On Premises on any server with a dual-core
  processor running at 2.0GHz or higher, at least 4GB of RAM, and 5GB of
  disk space. The operating system must be Ubuntu Server 12.04 LTS
  x86_64 or higher. You must also have PostgreSQL installed and network
  ports 80/tcp (http) and 443/tcp (https) open. You can optionally open
  port 22/tcp (ssh) as well for general server maintenance.


Difference between escape velocity and speed

Question: What is the difference between escape velocity and escape speed , is their any error if we use them interchangeably?
Answer: I think it is escape speed because it is derived by summing the kinetic energy (which depends on speed, not velocity) with gravitational potential energy. If the sum is greater than zero then the object will be on a hyperbolic escape trajectory (as long as there are no other forces involved eg no air resistance and you are not firing the object into the ground).
The term escape velocity is misused, unless you can show me instances of where it used and expressed properly with both a magnitude and direction...
The Wikipedia page https://en.m.wikipedia.org/wiki/Escape_velocity on escape velocity (sic) is particularly guilty:
"In physics, escape velocity is the minimum speed needed for an object to "break free" from the gravitational attraction of a massive body."
and then further down the page:
"The term escape velocity is actually a misnomer, and it is more accurately referred to as escape speed since the necessary speed is a scalar quantity (not a vector quantity) which is independent of direction (assuming a non-rotating planet and ignoring atmospheric friction or relativistic effects)." !
Comment: @Floris "as long as there are no other forces involved" is clear enough.


Are there any countries where ex post facto amnesty laws are a thing?

Question: laws that decriminalise acts and sentences that also retroactively free or reduce the sentances of convicts who commited various offences prior to the decriminalisation / sentance reduction
Comment: I believe that in France, when the statutory sentence for a crime is reduced or a crime is repealed, that this automatically retroactively benefits people currently serving sentences for that crime but I am looking for a citation to support that proposition and have misplaced the reference where I originally saw that stated.
Comment: What do you mean by "ex post facto amnesty laws"? Almost all amnesties are post-facto, pardoning people after their crime. If you think some act should not be punished, you do not issue an amnesty for future crimes, you either change the law to decriminalize the act or even instruct the executive branch to not seek conviction for those offenses.
Answer: Article 15 of the International Covenant on Civil and Political Rights:

prohibits the retroactive application of criminal law, both in
relation to criminal conviction (Article 15(1), first sentence) and
greater severity of any sentence (second sentence). It also requires
a more lenient penalty to be applied if one is introduced after the
offence was committed (third sentence). Article 15(2) preserves the
legitimacy of the trial and punishment of crimes 'according to the
general principles of law recognized by the community of nations',
prompted by concerns that the post-Second World War prosecution of war
crimes may otherwise be called into question.

But, as Wikipedia in the link above explains, this only "requires the imposition of the lesser penalty where criminal sentences have changed between the offence and conviction."
Many countries have adopted it, but some have adopted it only with reservations. The United States, for example, has specifically reserved and not assented to those provisions of Article 15:

The United States has made reservations that none of the articles
should restrict the right of free speech and association; that the US
government may impose capital punishment on any person other than a
pregnant woman, including persons below the age of 18; that "cruel,
inhuman and degrading treatment or punishment" refers to those
treatments or punishments prohibited by one or more of the fifth,
eighth, and fourteenth amendments to the US Constitution; that the
third clause of Paragraph 1, Article 15 will not apply; and that,
notwithstanding paragraphs 2(b) and 3 of Article 10 and paragraph 4 of
Article 14, the US government may treat juveniles as adults, and
accept volunteers to the military prior to the age of 18. The United
States also submitted five "understandings", and four "declarations".
Answer: canada
Canada has An Act to provide no-cost, expedited record suspensions for simple possession of cannabis (described here).
It also has the Expungement of Historically Unjust Convictions Act (described here).
united-states
Statutes can retroactively reduce sentences and allow for those in custody to seek resentencing. See e.g. Terry v. United States (2021) (relating to the Fair Sentencing Act of 2010 and the First Step Act of 2018).
Comment: I forgot about my question here. my bad but still can you answer the specific details of my other question in relation to this , over here ?
Answer: The Amnesty Act of 1872
The USA was embroiled in a civil war with separatists. The very act of fighting against the USA was illegal, people were convicted and ineligible for office due to being part of the confederate army. But in 1872, all people who fought and had been made ineglible were forgiven.
Answer: france
Article 34 of the Constitution of France as currently in force (French text) expressly provides:

Statutes shall determine the rules concerning:
...

the determination of serious crimes and other major offences and the penalties they carry; criminal procedure; amnesty; ...

The provision has been used at least 10 times (partial list on the French version of Wikipedia) since the Constitution was enacted in 1958.


Why are multiple wides not considered as a bye plus wides?

Question: If a wide ball runs away to the boundary, it's considered as 5 wides, rather than 1 wide plus 4 byes. Is there a reason for this breakdown of the extra runs?
Answer: The question is "whose fault is it"? Wides are considered to be the bowler's fault, and are  scored as runs conceded by the bowler. On the other hand, byes are considered to be the wicket-keeper's fault and not scored as runs conceded by the bowler. The typical case for 5 wides is a ball either so wide or so high that the keeper doesn't have a reasonable chance to stop it, so it's reasonable that these are debited to the bowler.
Comment: That's correct for leg byes, but incorrect for byes - there's no requirement to play a shot. Please see [Law 26](http://www.lords.org/mcc/laws-of-cricket/laws/law-26-bye-and-leg-bye/).
Comment: To add to the answer, a bye/leg bye is given only if the batsman tried to play a shot. But a wide is given even if the batsman leaves the ball to go it to the keeper.


would a core failure on a multicore computer cause system instability?

Question: Say for example, one of the cores in a quad core computer overheated and died, would the system compensate by routing all operations to the remaining 3 cores, or would the computer be inoperable? If the system compensates, could it compensate for 3 of 4 cores failing?
Comment: @Hennes: Cylinders cannot be compared to CPU cores, given that it's possible to turn off any given core manually. It's more similar to four engines in a single car.
Comment: If you have a 4 cylinder car and one of the cylinders breaks, do you expect it to run fine on the remaining 3?
Comment: ... or trying to develop a software product with a staff of three programmers  when you had expected to have four.
Answer: It largely depends on the exact failure (and the system architecture, but I'll assume you're talking about a standard x86 based system).
In short, the system will not function properly - with exact symptoms ranging from appearing to be okay "most of the time" to a complete failure to boot.
There is no mechanism to ignore the bad core at run time, and as such anything that attempts to execute there risks failing/corruption/crashing.
Comment: I have a broken core and my computer works, i disabled it via BIOS
Answer: No. Your computer is not supposed to start-up at all if any core has failed.
If any core failure is detected at testing and packaging stage, it can be disabled like those AMD 3-core processors.
Answer: A CPU core cannot be compared to a car engine. Depending on the system BIOS, it may or may not detect a core failure. Most probably it will still route operations to the core and fail. The BIOS may allow for discrete core disabling (trial and error on each core), in which case you will be able to operate normally. At the end of the day, time to replace the CPU
Answer: I can say that I have a i7 6700k with 3 out of 4 cores working. If I have all 4 cores active, it will just blue screen when I start my computer. However, when I go into BIOS and change to only 3 active cores, it will perform normally. I have no idea how the core was damaged as I bought this computer broken for a cheap price and fixed it.


Understanding APR - can it be calculated as a dollar amount

Question: If the APR (as used in the US Truth in Lending Act) is considered "the cost of your credit as a yearly rate," can an APR be converted to a dollar amount?  For example 10% simple interest per year on a $\$100$ loan would be $\$10$ per year (right?  I'm not a math whiz).  So if a $\$100$ loan has an APR of 10%, would that mean 10% of the amount financed?  If that was correct, wouldn't the annual figure X the number of years in the loan = the total finance charge?  I've tested this using a sample TILA disclosure but it doesn't seem to work, so I'm wondering what I've got wrong.  (I understand the general idea of the APR, finance charges, and amount financed).
Answer: Actually, it makes no sense to express APR as anything but a percentage.  The reason is that APR is the effective interest rate you are actually paying due to compound interest.  It is an artifact of the computation involved in compound interest and nothing else.  It does not cost any additional money,; what costs money is compound interest.
For example, consider a loan having an interest rate $r$ to be paid in $12$ monthly installments per year.  The APR is then
$$\left ( 1+\frac{r}{12}\right )^{12} -1$$
Note that, for sufficiently small $r$, the APR is roughly the interest rate.  In general, however, this is not the case.


Column SubscriberKey into a SendLogDE doesn't populate any data

Question: I'm new with the SendLogDE but I have searched and found (What custom fields can I include in the SFMC send log? and https://trailhead.salesforce.com/es-MX/content/learn/modules/marketing-cloud-data-management/collect-data-with-a-send-log) that one of the most common custom field is SubscriberKey. So I added to my SendLogDE but it doesn't populate any data. Do you know why?
Answer: For this answer, I'm assuming the custom field added to the sendlog is named "SubscriberKey".
If you do not have a field in your sending data extension named "SubscriberKey" (as @Swati suggests), you can also set the value for the field using a personalization string (as @David M suggest) or AMPScript variable.
The personalization string for subscriberKey is "_subscriberKey".  But since you cannot create data extension fields with a leading underscore, try the following AMPScript.
<code>%%[
var @SubscriberKey
set @SubscriberKey = _subscriberkey
]%%
</code>
Comment: Hi David, your are assuming well. The field in the sendable DE is called "SubscriberKey" as well. That's why I don't understand why is not getting populated.
Answer: The custom field names must match the fields in the source Data Extension, that is, the one you use to send the email (your audience). You can also use some personalization strings:
Personalization Strings in Email Studio
Just keep in mind you cannot reference personalization strings that starts with underscores.
Answer: The field will get populated only if you have a field 'SubscriberKey' in your sendable DE. If you wish to poulate it with subscriber key, you could make a field with the same name which has a send relationship with subscriber key in your DE.
Comment: Hi. The field in the sendable DE is SubscriberKey. Thats why I don't understand why is not getting populated.
Comment: Once the email is sent, when you query the sent data view for that job, do you see the subscriber key populated?


What is difference between Lightsail and EC2?

Question: Recently Amazon launched Lightsail. Is there any difference between them? If yes, then what's the difference? Are Lightsail instances more powerful than EC2?
Answer: Testing¹ reveals that Lightsail instances in fact are EC2 instances, from the t2 class of burstable instances.
EC2, of course, has many more instance families and classes other than the t2, almost all of which are more "powerful" (or better equipped for certain tasks) than these, but also much more expensive.  But for meaningful comparisons, the 512 MiB Lightsail instance appears to be completely equivalent in specifications to the similarly-priced t2.nano, the 1GiB is a t2.micro, the 2 GiB is a t2.small, etc.
Lightsail is a lightweight, simplified product offering -- hard disks are fixed size EBS SSD volumes, instances are still billable when stopped, security group rules are much less flexible, and only a very limited subset of EC2 features and options are accessible.
It also has a dramatically simplified console, and even though the machines run in EC2, you can't see them in the EC2 section of the AWS console.  The instances run in a special VPC, but this aspect is also provisioned automatically, and invisible in the console.  Lightsail supports optionally peering this hidden VPC with your default VPC in the same AWS region, allowing Lightsail instances to access services like EC2 and RDS in the default VPC within the same AWS account.²
Bandwidth is unlimited, but of course free bandwidth is not -- however, Lightsail instances do include a significant monthly bandwidth allowance before any bandwidth-related charges apply.³  Lightsail also has a simplified interface to Route 53 with limited functionality.
But if those sound like drawbacks, they aren't.  The point of Lightsail seems to be simplicity.  The flexibility of EC2 (and much of AWS) leads inevitably to complexity.  The target market for Lightsail appears to be those who "just want a simple VPS" without having to navigate the myriad options available in AWS services like EC2, EBS, VPC, and Route 53.  There is virtually no learning curve, here.  You don't even technically need to know how to use SSH with a private key -- the Lightsail console even has a built-in SSH client -- but there is no requirement that you use it.  You can access these instances normally, with a standard SSH client.

¹Lightsail instances, just like "regular" EC2 (VPC and Classic) instances, have access to the instance metadata service, which allows an instance to discover things about itself, such as its instance type and availability zone.  Lightsail instances are identified in the instance metadata as t2 machines.
²The Lightsail docs are not explicit about the fact that peering only works with your Default VPC, but this appears to be the case.  If your AWS account was created in 2013 or before, then you may not actually have a VPC with the "Default VPC" designation.  This can be resolved by submitting a support request, as I explained in Can't establish VPC peering connection from Amazon Lightsail (at Server Fault).
³The bandwidth allowance applies to both inbound and outbound traffic; after this total amount of traffic is exceeded, inbound traffic continues to be free, but outbound traffic becomes billable.  See "What does data transfer cost?" in the Lightsail FAQ.
Comment: Very informative. My favorite [IT red top](https://en.wikipedia.org/wiki/Tabloid_journalism#Red_tops) "The Register" has a write-up about the launch of Lightsail: "[Cheap virtual box hosters – Amazon's Lightsail is out to destroy you (yes, you, Digital Ocean)
Look out for bill shock, though, devs](http://www.theregister.co.uk/2016/11/30/amazon_lightsail/)". Check out the curmudgeon-occupied comment section too. I may well give Lightsail a spin.
Comment: This is so well written and clear that it should be in the Amazon docs. Well done!
Comment: Coming from EC2 to Lightsail an important difference is you can't change instance type on Lightsail - you have to launch a new instance from a snapshot - and [you can only go up in size](https://lightsail.aws.amazon.com/ls/docs/en/articles/understanding-instance-snapshots-in-amazon-lightsail)!
Comment: Note that Lightsail's firewall controls are less fine-grained than EC2. EC2 allows you to whitelist IP ranges, but Lightsail only allows you to enable all access to specified ports.

With EC2 you can specify to allow ssh for only your IP address, changing it in the console if you log in from a new location. With Lightsail, you cannot do this. You can, of course, still use iptables.
Comment: The [Lightsail GetBundles API](https://docs.aws.amazon.com/lightsail/2016-11-28/api-reference/API_GetBundles.html) reports the underlying instance type :-)
Comment: @TylerA. that's a good point.  Lightsail's simplified security group settings also do not allow any protocols other than TCP and UDP -- no ICMP, ESP, GRE, etc.
Comment: @jonatan that's a good point.  Thank you for the link.
Comment: "Lightsail instances do include a significant monthly outbound bandwidth allowance" It is not just outbound, it will also calculate inbound bandwidth under that free quota. @Michael-sqlbot
Comment: @PradipVaghasiya only outbound is billable, but you are correct to point out that  inbound traffic means less outbound traffic will be included in the free quota.  The answer has been updated
Answer: Lightsail VPSs are bundles of existing AWS products, offered through a significantly simplified interface. The difference is that Lightsail offers you a limited and fixed menu of options but with much greater ease of use. Other than the narrower scope of Lightsail in order to meet the requirements for simplicity and low cost, the underlying technology is the same.
The pre-defined bundles can be described:
% aws lightsail --region us-east-1 get-bundles
{
    "bundles": [
        {
            "name": "Nano",
            "power": 300,
            "price": 5.0,
            "ramSizeInGb": 0.5,
            "diskSizeInGb": 20,
            "transferPerMonthInGb": 1000,
            "cpuCount": 1,
            "instanceType": "t2.nano",
            "isActive": true,
            "bundleId": "nano_1_0"
        },
        ...
    ]
}

It's worth reading through the Amazon EC2 T2 Instances documentation, particularly the CPU Credits section which describes the base and burst performance characteristics of the underlying instances.
Importantly, since your Lightsail instances run in VPC, you still have access to the full spectrum of AWS services, e.g. S3, RDS, and so on, as you would from any EC2 instance.
Comment: If these are actually t2 instances, do they have the same cpu credit limitations?  An issue I have with Nanos is when they run out of cpu credits, they're brutally slow.
Answer: In lightsail a virtual machine, SSD-based storage, data transfer, DNS management, and a static IP are all offered as a package. Whereas in normal case you provision an EC2 instance and then setup the rest of these things.Also Bandwidth included in the price, no security groups to set up, no need to worry about EBS volumes sizing.
Answer: Check official website
https://aws.amazon.com/free/compute/lightsail-vs-ec2/

Amazon Lightsail – The Power of AWS, the Simplicity of a VPS
https://aws.amazon.com/blogs/aws/amazon-lightsail-the-power-of-aws-the-simplicity-of-a-vps/
Amazon EC2 vs Amazon Lightsail  (comparison on point )

Web Performances
Plans
Features and Usability

Source : https://www.vpsbenchmarks.com/compare/features/ec2_vs_lightsail
Comment: Those are really misleading graphs. It's good to start them at 0. Something this is 2x value in real life, shouldn't have a chart bar 6x the size.
Comment: Suppose I have 3 light sail instances (also knows as vps - virtual private server), then, can they by default talk to each other?
Answer: I think the lightsail as the name suggest is light weight and meant for initial development. For production sites and apps with high volume it simply becomes unavailable and hangs....It is just a sandbox to play with things. Further lack of support reduces its reliability.
      There should be an option to migrate to EC2, when u fully develop your apps or sites..So that with same minimum configuration you can migrate to scalable EC2..
Comment: Tou can now explort lightsail snapshots to EC2 https://lightsail.aws.amazon.com/ls/docs/en_us/articles/amazon-lightsail-exporting-snapshots-to-amazon-ec2


Difference between N3K and N5K

Question: I have 4-5m PPS and ~12Gb bps and around 650 interface vlan and each vlan has 3-4x prefix such as /29 or /28 and i have 6-7 bgp session with no full table and around 2000 IP routes with around 3000 mac address , as i read nexus 3k datasheet and 5k datasheet it seems both can handle my traffic, but i do not know what is their real difference , and does n3k really is able to handle these traffics ?
my exact 3k part number is N3K-3064PQ-10GX
and if i want to use N5K i want to use N5k-5548UP-AF with N55-D160L3-V2 Layer 3 module.
and i have that N3k in stock but if i want to use n3k i should purchase it so i like to save my money :P
i will appreciate if anyone can guide or help me.
Thank you.
Comment: As others have said, the n5k is not so string in the L3 world. Your 3064 may physically support everything you want to do, but it's not ideal. Maybe look at the n6k. If you have the budget and space, n7k. Or a n9k, but they (9300) have a long list of restrictions as well.
Comment: Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
Answer: Be sure to understand the limitations of the N5K
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5500/sw/Verified_Scalability/730N11/b_5500_Verified_Scalability_730N11/b_5500_Verified_Scalability_702N11_chapter_01.html
That document ist for NXOS 7.3.0, but I don't think that these figures grew all that much on the way to 7.3.3.
Most important:

only 256 SVIs
only 7'200 or 14'400 dynamic routes (depending on version of the L3 card)
only 160Gbps of L3 throughput (see below)
can't configure routed ports (if memory serves right)

And then I have a fragement of memory of throughput rating dropping from 960Gbps to 240Gbps with the L3 card - but I'll try to find better info source for that.

[EDIT]
So it's only 16x10G in/ouit of that L3 Daughter card.
Source: http://n-sistem.net/pdf/Architecture_Nexus5000_5500_2000.pdf Which is from a presentation at Cisco Live 2011 in Las Vegas (Session BRKARC-3452, Cisco Nexus 5000/5500 and 2000 Switch Architecture) from where I'll try to quote:

Layer 3 Forwarding Engine connects the the X-Bar via two UPC (160GBps)

And this diagram:

[/EDIT]

Hence: The N5K is a very fine L2 switch with can be persuaded to do "some" L3 work. A full-fledged L3 switch, it is not.
Answer: Start from this page for the 5500's verified scalability and this for the 3K.
In short (...and as mentioned above) the L3 switching module on the 5500 is basically a router on a 16x10GE switch.  The verified scalability guide calls out a 256 SVI limit.  If your requirement for 650 'interface vlan' maps to SVI's then the 5K is likely not fit for purpose.  The 5500 is, however, capable of supporting up to 4000 active VLAN's (...once again reinforcing that the 5500 began life as a competent L2 switch).
The 3064 can support 1024 SVI's, but the platform can only support 507 active VLAN's concurrently (assuming MST).  Again, if you're defining 650 SVI's then this would tend to imply defining at least 650 VLAN's and is over spec for the switch.  The 3K was built as a low-cost top-of-rack switch with (old) merchant silicon that could support L3 and decent throughput but wasn't intended to do any kind of L2 heavy lifting.
If I were forced to choose, I'd use the 5500 as an L2 switch to terminate other switches and deal with trunking, whatever flavor of STP, etc and then use the 3064 via an LACP bundle to handle L3.
That said, this is a no-win situation in terms of real operations.  Both platforms are old.  The 5500 hit end of software support in May of 2020 and is full LDOS (last date of support) in 2024.  The 3064PQ was announced EOS in 2016 and hits full LDOS in 2022.
Basically the point is that neither switch should be newly deployed into any kind of production role.  Beyond any question of scalability they're both going to soon hit a point where there aren't even security updates, much less bug fixes or useful enhancements.  Both platforms have been in the process of active retirement for years at this point.
If these are your two options, find a third.
Comment: SVI = Switched Virtual Interface, so basically any time you have `interface vlan xxx` and an L3 definition you're using one of the 256 interfaces that the L3 card supports.  Would it work at 280?  Maybe, but it's outside what's been tested and certified for that platform and you could hit anything from a software limit to unexpected (and potentially catastrophic) behaviors.  The 5500 was a decent choice as an L2 aggregation platform but the L3 module was kind of an afterthought (nb - the 56xx has native L3 routing, as do most modern DC switches).
Comment: i have N55-D160L3-V2 for my n5k-5548up-af and i have create 280x interface vlan with different IP address on them and all of them are up and routes are available in show IP route, do i understand svi correctly? it N55-D160L3-V2 cause that i can have much more vlans ?
Answer: The N3k is suitable for your application.
The main advantages of the N5k are the ability to use fabric extenders (very similar to stacking tbh) and to combine fibre channel & Ethernet for networks which have legacy SAN needs, as well as some models having expansion slots.  However, it is a more complex product line; and doesn't offer very large MAC & layer-3 tables as compared to many other modular multi-layer switches.
You didn't describe your plan for aggregating the 650 interfaces/ports but I assume you are confident in that aspect of your plan.
Comment: Just because you can see 350+ SVI's up doesn't mean that they're going to function as expected.  You're almost 50% beyond what Cisco's QA ever tested and certified for that platform.  It might work perfectly.  It might crash randomly.  It might cause completely unpredictable behavior.  If these services are even faintly important you'd be better served looking at a platform that's both supported and within the vendor's listed limits.
Comment: we have 20x full rack in a datacenter and we are offering colocation services , and each interface vlan may have 3-4 x prefixes such as /29 or /28 or ... , but i just create 350x interface vlan on a n5k-5548up-af and assign 1x /24 to each vlan , i can see all vlans are up and from a server behind the router i can ping their gateway and in show IP route i can see their routes, and as i read in that n5k guide it says the verified limit is for that time that all features are enabled! i just enable 2-3 feature

Difference between N3K and N5K


How to translate "见字如面" into English?

Question: As far as I know, I think "见字如面" literally means when you see someone's letter, it's as if you were seeing him or her face to face. So I believe this word sort of indicates your familiarity with the letter guy and how glad you are when you receive his or her letter.
Answer: From museum archives, we can see this phrase appears in lots of letters among family members, i.e., husband and wife. At least in these examples, writers and the receivers know well each other and have already seen handwriting before. So it definitely indicates closeness and has a fairly strong emotion.
In other words, it's NOT just politeness of a simple greeting, such as 'Yours', 'Regards' in English. It's weird if the letter is to a stranger.
Strictly speaking, this expression can only be used in the same generations. So you can use it if you write a letter to your sisters/brothers but not to your parents. In a preparation document for the college entrance exam, there is an example use of this phrase. Here is a link!
It points out that it's incorrect if you use it to write a letter to your grandpa.
That said, the use of the phrase is pretty flexible nowadays. I see people use it in an email as a simple greeting. Given the fact that the phrase now is not commonly used, especially in handwriting letters, I think it's fine with both opinions.
Answer: Your understanding is partially correct. This phrase is used at the beginning of the letter to address the receiver.
The meaning of the phrase - "see the letter as we've met", or "see the letter as seeing me/each other", indicates the closeness/close relationships between the letter writer and the receiver, but does not necessarily have emotion attached (as a greeting).
If I didn't make mistake, the original phrase should be "见字/信如晤(meet)" then.
Comment: Do you have any source to back up the claim that the phrase is used to address people "who have a lower generation ranking than the letter writer"?
Comment: @Betty No. I don't. Revised.
Comment: @Betty I couldn't find any source that supports my comment, but after a long thought, I still stand by it. Because, though the sentence implies closeness and affection of the letter writer and the receiver, it lacks the "respect" aspect that is usually expected from a Chinese person who writes to their elders (長輩). But nevertheless, I revised my answer for it could be controversial.
Comment: Hi, I didn't mean to disagree. I'm just not sure about this, because I seldom encounter the phrase in real life. I'd be happy if some sources can be found to confirm it in either direction.
Comment: @Betty It is very important in choosing the right word or phrase when a Chinese person writes to his/her elder, for example, "近來**您**可安好" will replace "近來**你**可安好", which is generally used between people of the same generation but lacks the means of "respect/regard". Well, this is just a personal opinion maybe.
Comment: I could see @r13 view point. "closeness and affection" in the context of a past ultra conservative Chinese society only occur or "practiced" among peers with gender differentiation thrown in. Familial generational interactions in any form was frown upon and it was considered ill-mannered to address, spoken or in letters, an elder too informally, unlike now. So, I don't think your remark is that controversial.
Answer: What a nice day! I thought that the letterhead greeting maybe different from the different relationships/people, so there is no fixed translation in this case. For me, the translation is already answered in the letter! v
Answer: 見字如面 sounds similar to 見字如見人

通过你的字可以看出你是怎么样的人...

People can tell who you are by your handwriting.

A person's handwriting is like his face, it is recognizable and it leaves an impression
I don't believe it is a greeting. The one who read a letter from a friend might feel he is looking at his friend's face in the handwriting, but that's a reaction to the letter, the one who wrote the letter wouldn't presume it

How to translate "见字如面” into English?


Decreasing returns to scale vs downward sloping demand curve

Question: How can one show that decreasing returns + perfect competition is equivalent to monopolistic competition + constant returns?
Comment: 1. It is not; though some variables do have the same equilibrium values. Please provide context/source for your claim, otherwise it is hard to tell what exactly you are asking.
Comment: 2. Your title includes "*downward sloping demand curve*", but then it does not come up in the body of your question; please edit to clarify.
Comment: Downward sloping demand curve is implied by monopolistic competition.
Answer: A simple case to show these two are isomorphic in terms of the firm problem.
Perfect Competition:
Each firm $i$ produces a homogeneous good with a decreasing returns to scale production technology $f(i) =  (s(i) n(i))^{\theta}$, where $s$ is productivity, $n$ is the only input labor, and $\theta<1$. Each firm maximizes their static profit $\max_{n_i} pf(s_i, n_i)-wn_i$ and use $n_i^*(s_i,p,w)$ labor.
Monopolistic Competition with Constant Return:
Each firm $i$ produces a differentiated good with linear production function, $f(i)=s(i) n(i)$. Assume representative agent has preferences over different goods $U=\left(\int c(i)^{\theta} d i\right)^{1 / \theta}$. (Alternatively assume a final good produced by perfectly competitive firms with the production function of this.)
From the utility maximization problem we obtain $U^{1-\theta} c(i)^{\theta-1}=\lambda p(i)$ , where $\lambda$ is the multiplier of consumer's budget constraint (or $\lambda^{-1}$ is the aggregate price index).
Each firm's revenue is thus $p(i) c(i)=U^{1-\theta} \lambda^{-1} c(i)^{\theta}= U^{1-\theta} \lambda^{-1}(s(i) n(i))^{\theta}$ where we assume the agent has measure of 1 and thus $c(i)=f(i)$. Each firm thus maximize $\max_{n_i} p(s(i) n(i))^{\theta}-wn(i)$ where $p \equiv  U^{1-\theta} \lambda^{-1}$ and use $n_i^*(s_i,p,w)$ labor.
In summary, both decreasing return to scale and monopolistic competition provide some curvature  in firm objective function to pin down the firm size.
Comment: I would not call the two cases "isomorphic". Yes, the firms' optimization problem is identical given a specific functional forms and a parameter $\theta$ that is used in different aspects of the models but just happens to coincide, but I don't see how this is "isomorphic".
Comment: Perfect thanks!


Time for journal reviewing / referring in mathematics - Is there a recent study?

Question: In the question: Lengths of review process of mathematical journals a nice question was asked and answered: how to compare journals in terms of time for the review processing. The article cited in the answer is quite nice http://www.ams.org/notices/201310/rnoti-p1390.pdf but is from 2013. Seven years after, are there some similar studies which can tell what kind of backlogs/ times needed for mathematical journals to accept / reject articles? A young mathematician asked me this today and I gave him the link, but a more recent one would certainly be more helpful.
Comment: This is the same report from November 2019: https://www.ams.org/journals/notices/201910/rnoti-p1713.pdf
Comment: Thanks a lot. That is exactly the answer I needed. Why not putting it as an answer and I will accept it.
Answer: The American Mathematical Society provides regular (annual, I believe) on journal backlog times. The latest can be found here: https://www.ams.org/journals/notices/201910/rnoti-p1713.pdf
Depending on your subfield it may not contain data on all relevant journals, but it is quite comprehensive. The reports are published in the November issue of the Notices of the AMS, which is also available online.
The data in the report is based on information provided by the journals itself.
Comment: Thanks, that is exactly what I was looking for. It is a pity that most of the new free journals are not there, but it could be improving in the future.
Answer: A general source for many, many domains beyond just mathematics is SciRev, a site where authors submit reviews of their experience with the peer-review process at many (hundreds or thousands?) of journals across many disciplines. If you click on the "All reviews" tab, you can then search for journals by name or discipline; it includes many subfields of mathematics.
For me, the most useful feature of SciRev is that I use it to track my personal peer-review process, and then when a final decision is received, I can conveniently submit a review of my experience with that journal.
However, the downside of a site like this is that it is entirely self-reported, so without a large number of submissions for a given journal, you cannot consider the averages reported there to be scientifically valid. That said, it probably has reports for more journals than a scientific study like the one you originally mentioned, so it can at least give an indication of delay times.
Comment: Thanks. I did not know this website. In mathematics, there are very few results, but maybe if the website is used it can be helpful.


How to edit .pub format files on fedora?

Question: Is there an aplication/software that I can use to edit the Microsoft publisher (.pub) format files on fedora14.
Answer: The short answer is "no."
The longer answer is that you can probably set up Publisher with CodeWeaver's Crossover Linux with some degree of success.
Probably using that and slowly/rapidly transitioning existing files to Scribus or LibreOffice's Draw would be the best way to go.


What is the best way to forward all requests on a certain port to another machine on the network?

Question: I have two dedicated servers and no hardware firewall. I'd like to forward all requests that come into the primary server on port 1008 to be fulfilled by another dedicated server on the same network. I know I need to set up some kind of TCP proxy, but I first heard of IPTables yesterday. Any quick tips?
Answer: The easiest way is to use something which is just a TCP proxy. It is possible to achieve this using iptables, but not easy.
It is easy to forward requests from A intended for B to C (using DNAT) but harder to get C's responses to go back to A via B (because DNAT does not change the sender address). A would then ignore the responses as they'd be coming from C rather than B.
Essentially the way of doing it would be to set up B as C's default gateway, and using forwarding, however, this places an additional point of failure in B; if B fails, C's outbound traffic (including responses to requests sent to C directly) would end up going down a black hole.
Using IPtables it is possible without this routing trick I think, but you'd need to have the same connection SNAT'd and DNAT'd, which is tricky at best.
Normally in such situations, most people put another host (firewall) in front of the two machines and have it make DNAT decisions - of course this introduces a point of failure as well, which is why in critical setups, the firewall typically has a rendundant backup (its configuration is synchronised and sometimes its connection tracking table is)
Answer: First off I would recommend you get a firewall in place. I've used Shorewall for a long time to manage iptables and it is pretty easy to configure. Second if you use something like Shorewall there are easy guides on how to do DNAT (port fowarding).
Answer: Carson is right: put a bridging firewall between servers and clients. Shorewall (IP tables) can then redirect traffic to different ports and different machines.
With the firewall being a bridge, you don't have to change your network settings, yet the bridge interface has to be assigned one IP address of each network clients and servers are in. Else the redirection won't work.
Caveat: the machine where the connection originally was pointed to has to be online (means: its IP address has to be in use), else the redirect won't work.
If the redirection is meant as a means of failover for high-availability, I would consider a load balancer (cluster) instead of the firewall, which leads to linux virtual server (for a general approach) or to a load balancer software like Apache (with mod proxy_balancer), balance or pount (if only http request are to be balanced). There's also hardware appliances like from f5 for load balancing.


Executing ArcMap AddIn function when there is mouse click on map?

Question: I am developing an add-in for ArcMap 10.0 where I need to execute code when there is a click on the map open. How do I do this? I am using VB in Visual Studio 2010. I also need to get the coordinates from the click event.
Answer: If you have created an add-in and added a ESRI.ArcGIS.Desktop.AddIns.Tool to it then stub out the following event:
Protected Overrides Sub OnMouseDown(ByVal arg As
    ESRI.ArcGIS.Desktop.AddIns.Tool.MouseEventArgs)

' --write your function here--

End Sub

arg.X and arg.Y will be the coordinates where the user clicked.
You will most likely want to convert the x and y values to the transformation used by the display:
Dim mxDoc As IMxDocument = CType(My.ArcMap.Application.Document, IMxDocument)
Dim clickedPoint As ESRI.ArcGIS.Geometry.IPoint =
    mxDoc.ActiveView.ScreenDisplay.DisplayTransformation.ToMapPoint(arg.X, arg.Y)

Comment: I had this code already, but it says ESRI.ArcGIS.Desktop.AddIns.Tool.MouseEventArgs is not accessible because it is protected. How can I fix this?
Comment: `code` Public Class toolIdentify Inherits ESRI.ArcGIS.Desktop.AddIns.Tool Public Sub New() End Sub Protected Sub OnClick() End Sub Protected Overrides Sub OnMouseDown(ByVal arg As ESRI.ArcGIS.Desktop.AddIns.Tool.MouseEventArgs) End Sub Protected Overrides Sub OnUpdate() End Sub End Class `code`           Did you put it in the ITool class itself?
Comment: I'm only using a button currently, because I don't need it to be in a specific tool. Should I do this with a tool? Or is a button fine?
Comment: Ok, I may have misread your question or you may need to clarify. If you need something to happen when user opens a map document using the open button then your addin needs an event handler (IDocumentEvents_Event interface). If you want to capture a mouse click on the map then you need an ITool as I described.
Comment: Thank you! I figured out that I was being dumb, I thought the button had to be on a tool but I just needed the tool. Also, Michael I saw your edit about the transformation. Is that to get the actual latitude and longitude? I'm trying to get latitude and longitude in decimal degrees as individual variables. I am currently trying that code but it says "Type 'IPoint' is not defined". How do I make it work? Clearly I'm new to this add-in programming, so I appreciate all the help.


In the heliocentric model of planetary motion, is Sun assumed to be stationary at the center?

Question: In Kepler's first law, the earth moves around the sun in a elliptical path. The sun is at one of the focuses. Now, would this suggest that sun is always at the focus? i.e: it's position is fixed?
Comment: Possible duplicates: https://physics.stackexchange.com/q/323183/2451 and links therein.
Answer: These laws  assume the sun  has to be in one of the focal points. This workes because the sun is so much heavier than any of the planets. In truth all bodies revolve around the barycenter of the composite planetary system, including the sun itself.

In astronomy, the barycenter (or barycentre; from the Ancient Greek βαρύς heavy + κέντρον center1) is the center of mass of two or more bodies that orbit one another and is the point about which the bodies orbit. It is an important concept in fields such as astronomy and astrophysics. The distance from a body's center of mass to the barycenter can be calculated as a two-body problem.
If one of the two orbiting bodies is much more massive than the other and the bodies are relatively close to one another, the barycenter will typically be located within the more massive object

The present  day heliocentric orbits are about the barycenter.

A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun itself are in such orbits, as are many artificial probes and pieces of debris

Kepler's orbits were agood approximation for that time and accuracy of observations.
Answer: Yes, Kepler assumed that the centre of the Sun is exactly at a focus of the planet's elliptical orbit. However, Newton showed that that's not quite correct, and in a two body system both bodies execute elliptical motion, with the centre of mass of the system at a focus of each of the ellipses.
For more details, please see the two-body problem and the gravitational two-body problem.
Of course, in our solar system there are many bodies, which all have some effect on each other's orbits. The dominant masses are of course the Sun, Jupiter and Saturn. Here is a diagram from Wikipedia of the motion of the barycentre (centre of mass) of the solar system, relative to the Sun. Jupiter's orbital period is around 12 years, Saturn's is around 29 years. You can see that Jupiter has quite a strong influence on the barycentre.
Comment: Wait a second I thought newton proved keplers third law by assuming the orbit to be circular :t
Comment: So he used that assumption even tho he knew it was wrong?
Comment: It's quite straightforward to derive Kepler's  3rd law for a circular orbit from $F=Gm_1m_2/r^2$ and the formula for centripetal acceleration, $a_c=v^2/r$. But Newton was more thorough than that. ;) Wikipedia has some good info on [Kepler's laws](https://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion).
Comment: "Using Newton's Law of gravitation (published 1687), this relation can be found in the case of a circular orbit by setting the centripetal force equal to the gravitational force:"

He set centripetal = gravity...

So that means he was thinking it was a circle
Comment: No, Newton proved that the trajectory of a particle around a fixed central mass *must* be a conic section, i.e., a parabola, ellipse, or hyperbola; a circle is just a special case of an ellipse. And he showed how to analyze the motion of a two-body system where both bodies have substantial mass by using the concept of [reduced mass](https://en.wikipedia.org/wiki/Reduced_mass).
Comment: Does this suggest the time period law is same for any conic section?
Comment: The time period law applies to elliptic (& circular) orbits. Parabolic & hyperbolic trajectories aren't closed orbits, so the concept of periods doesn't apply to them. Low energy [radial trajectories](https://en.wikipedia.org/wiki/Radial_trajectory) also have periods; radial trajectories can be treated as degenerate conics.
Comment: Please see https://astronomy.stackexchange.com/a/44903/16685 for more info & diagrams of the solar system barycentre, including an interactive 3D diagram.


Can 2S (i.e. general compartment) tickets be booked online for trains in India?

Question: Can general compartment tickets (2S) be booked online? If yes then on what website?
Comment: 2S (Second seating) is not same as General Compartment/UR(unreserved). This question is ambiguous.
Answer: 2S (Second sitting) Class can be booked online using irctc.com, but 2S is not same as General Compartment.
2S stands for Second Sitting, it is a reserved class and your ticket will have your seat number, it is not the same as General Compartment which is Unreserved Class (UR).
General compartment ticket cannot be booked online and can only be obtained from the Station directly and sometimes available only from few hours before departure till the actual departure as it doesn't have any Seat reserved.
Answer: No. General compartment tickets can only be bought at the local railway station. Although there is no information which specifically suggests this in the Indian rail booking portals web site https://www.irctc.co.in/beta_htmls/term_src.html#Q1, but if one goes on to the website and tries to buy a general compartment ticket, there is no option to do so. This answer here may also give more insight.
Comment: This answer is wrong. vivek_bye's answer is the correct one. 2S is not same as UR and it can be booked online
Comment: @SouravGhosh Why do you say the answer is wrong ? The *answer* is correct to the question asked wrt General compartment tickets. I never said 2S cannot be booked online. May be you meant to propose an edit to the question ?
Comment: Sorry. I only noticed '2S' in the question. I overlooked 'General compartment' part. Yes. I also think that the question needs to be edited because 2S is not the general compartment. :) But editing is not the right judgement too because we don't know what the OP actually meant. (2S/General Compartment) :D


The UIView rotation in the overlay layer of camera controller view

Question: I am writing an application about the Augmented Reality.
In the CameraOverlayView, i have made a AR layer, which works fine.
I have planned the layer can be rotate, based on the iPhone orientation,
and its works fine.
However, I want to add some UIView elements on it, e.g. Radar, Slider.
For example, the Layer of AR = L0, I add the radar view, called L1, using
<code>[augViewController.view addSubview:radarView];
</code>
L2 --do not want to rotate,L1 --do not want to rotate,L0 --want to rotate
The radarView will follow the rotation of the AR layer L0....I want the upper layer stay static.
How can it be done ??
Answer: You should apply rotation to top views to nullify the rotation made by the bottom view.


WSGI django ModuleNotFoundError: No module named 'django'

Question: I have been trying forever to get my django api to deploy via apache. I have installed mod_wsgi for python 3.7 and my venv is using python 3.7.15. Trying to go to my django app url I am getting a 500 error.
Error log shows:
[Tue Dec 20 21:31:30.690951 2022] [:error] [pid 19216] /usr
[Tue Dec 20 21:31:30.691287 2022] [:error] [pid 19216]  mod_wsgi (pid=19216): Target WSGI script '.../project/project/wsgi.py' cannot be loaded as Python module.
[Tue Dec 20 21:31:30.691323 2022] [:error] [pid 19216]  mod_wsgi (pid=19216): Exception occurred processing WSGI script '.../project/project/wsgi.py'.
[Tue Dec 20 21:31:30.691393 2022] [:error] [pid 19216]  Traceback (most recent call last):
[Tue Dec 20 21:31:30.691423 2022] [:error] [pid 19216]    File ".../project/project/wsgi.py", line 19, in <module>
[Tue Dec 20 21:31:30.691428 2022] [:error] [pid 19216]      from django.core.wsgi import get_wsgi_application
[Tue Dec 20 21:31:30.691444 2022] [:error] [pid 19216]  ModuleNotFoundError: No module named 'django'
[Tue Dec 20 21:31:51.190670 2022] [:error] [pid 19217] 3.7.15 (default, Oct 31 2022, 22:44:31)
[Tue Dec 20 21:31:51.190707 2022] [:error] [pid 19217] [GCC 7.3.1 20180712 (Red Hat 7.3.1-15)]

apache conf file:
<VirtualHost *:80>

    ServerName api.project.com

    DocumentRoot path/to/project/root

    WSGIScriptAlias / /path/to/wsgi.py
    WSGIDaemonProcess project-name processes=4 threads=1 display-name=%{GROUP} python-path=path/to/lib/python3.7/site-packages:/path/to/project/root
    WSGIProcessGroup project-group

    <Directory "/path/to/project/root">
        Require all granted
    </Directory>

    #SSL stuff...

</VirtualHost>

wsgi.py:
import os
import sys

from django.core.wsgi import get_wsgi_application

path = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
if path not in sys.path:
    sys.path.append(path)

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'project.settings')

application = get_wsgi_application()

I originally had the wrong mod_wsgi installed (built for python2). I removed that and installed python3-mod_wsgi.x86_64 and changed module path in httpd.conf. I then realized that my mod_wsgi was for python version 3.7, but my application venv was running python 3.6.8. I then wiped the venv and created a new one with python 3.7.15. Changed the conf WSGIDAEMONPROCESS path to the correct 3.7 site-packages. Still same error.
Answer: Just installing a virtual environment is not enough, then you'll have to activate it.
Run pip install -r requirements.txt to install the required packages for the project.
The Error
The first error line states Target WSGI script '.../project/project/wsgi.py' cannot be loaded as Python module.
This means your environment variable DJANGO_SETTINGS_MODULE is not set properly. In order to do it, go to .bashrc and set it to the same value as in the asgi.py/wsgi.py file.
Run source .bashrc to reload the configuration file, and restart the bash terminal (or open a new one) where you're trying to run the application.
This should work.


Can i insulate the extra space in the room

Question: My house has one room that has an extra closet space but this is not insulated. The house has 2 stories and the top is triangular shaped so the rooms have that little bit of space behind the wall, we have a door and it's now being used as a storage space. Can I insulate it? I want to create a little space for my kids to play in (it is big enough to fit another bed and for adults to stand in). I live in Texas and I was reading that we shouldn't insulate the attic but this is not in the attic and I can't find any information on it on Google. Thank you
Comment: Attics usually need ventilation to keep the roof deck cooler.  The living space of a house(walls and top ceiling) should be insulated as much as possible.  As long as the attic ventilation is not blocked, usually found on the under side of the roof outside of top wall and roof peak, then can insulate the walls as much as you want.
Answer: Insulating is the least of your concerns. Before you build out a space that will actively be occupied by people and furniture, you need to have someone qualified look at the flooring structure to make sure it's strong enough for that. An attic space that might be used for a little bit of static storage needs much less strength than a room of bouncing kids, walking adults and furniture.


Bitcoin core wallet backup corrupted by an external tool

Question: Do you know if my wallet.dat which has become wallet.axx due to incorrect handling of an external program
(I do not know the name of the program, but it is used to encrypt Windows files)
has the possibility of reverting to initial format ".dat"
by myself ?
And above all without damaging the backup "Core" that it is ?
Answer: According to a random website coughed up by Google:

A file with the AXX file extension is an AxCrypt Encrypted file. AxCrypt is a file encryption program that scrambles (encrypts) a file to the point that it's unusable without first being decrypted with a specific password/passphrase.
When an AXX file is created, it's automatically assigned the exact same name as the unencrypted file but with the .AXX file extension appended to the end. For example, encrypting vacation.jpg results in a file called vacation.jpg.axx.
You can double-click an AXX file to open it with the AxCrypt software. However, note that if you're signed in to your AxCrypt account, double-clicking the AXX file will open the true file and not actually decrypt the AXX file.
Use the program's File > Open Secured menu to open the AXX file but not actually decrypt it. To decrypt the AXX file requires that you either right-click it and choose AxCrypt > Decrypt or use the File > Stop Securing option
Answer: You would first need to decrypt the file using whatever program you used to encrypt it in the first place. Once decrypted, the file will return to its original state. I'm marking this answer as off-topic since it is not necessarily related to bitcoin, but to file encryption software.


Are all phrase verbs informal?

Question: Are all phrasal verbs informal and not appropriate to use in academic texts? For instance, 'carry out'. I see this word in papers very often. Is it formal? Is it necessary to distinguish which phrasal verb is formal and which not?
Comment: Why do you think all phrasal verbs might be informal? If you see them often in papers then obviously a lot of academic writers think they're appropriate.
Comment: This should perhaps be combined with [Phrasal verbs ... formal and informal use](https://english.stackexchange.com/questions/61681/phrasal-verbs-formal-and-informal-use).
Answer: It is not true that "all phrasal verbs are informal and not appropriate to use in academic texts". The first two entries in the Collins Cobuild Dictionary of Phrasal Verbs are abide by and accede to, both of which the dictionary marks as formal.
What can said, however, is:

highly informal phrasal verbs should be avoided in academic text (e.g. knock off, wise up, do in),

most words in the Collins dictionary can be considered as existing around the center of the informal/formal cline,

writers aspiring to a greater degree of formality can often choose a single-word equivalent (e.g. carry out → perform, conduct),

often the phrasal verb may be the best choice, as  the Collins dictionary states:

It is often said that phrasal verbs tend to be rather 'colloquial' or
'informal' and more appropriate to spoken English than written, and
even that it is better to avoid them and choose single-word
equivalents or synonyms instead. Yet in many cases phrasal verbs and
their synonyms have different ranges of use, meaning and collocation,
so that a single-word equivalent cannot be substituted appropriately
for a phrasal verb. (Foreword)

As @nnnnnn said in the comment, if you are seeing phrasal verbs such as carry out many times in the writings in your academic field then you are safe to use them. But see point 3. above.
Comment: Thank you very much for the explanation.
Answer: This article from Typely.com amplifies and enlarges upon previous answers (there is a previous thread). It includes some useful examples (though the actual definition of 'phrasal verb' they use seems, from some claimed examples,  more than usually imprecise), classifying by register (formality):

Because of their frequent occurrence in informal speech and writing,
it's not unreasonable to think that phrasal verbs are always informal.
You may have read that phrasal verbs should be avoided in formal
writing, and that the single verb equivalents should be used instead.
While to some extent that's true, the reality is more complicated.
Phrasal verbs in formal writing
There are many phrasal verbs that can and also should be used in
formal writing. You will often see them used in many quite formal and
formal texts such as business letters, academic writing, scientific
papers, technical papers, legal documents, news reports, and official
government documents.
Before we move on to examples of phrasal verbs that are useful and
appropriate for formal writing, let's look at language register for a
moment...
'Register' is the term we use to refer to different varieties or
styles of speaking and writing, and also the degree or level of
formality with which we speak or write. Degree of formality is on a
sliding scale rather than in distinct categories, and although phrasal
verbs are often thought of as an informal part of language, most of
them are neutral, and some are in fact rather formal.
Some phrasal verbs are definitely informal, for example:

beaver away [at] – work hard for a long time
belt out [T] – sing or play a musical instrument very loudly
harp on [about] – talk non-stop about something in a boring or annoying way
pig out – eat a lot of or too much food

In your formal writing, you should of course avoid phrasal verbs that
are at the informal end of register, and steer clear of slang phrasal
verbs, and those that would be considered by many to be offensive. A
good phrasal verb dictionary will tell you which phrasal verbs are
informal, slang, or offensive.
It's true that very often, single verbs are more formal and therefore
are more appropriate for formal writing than their phrasal verb
equivalents. Some examples of these are:

Single verb/Phrasal Verb

constitute/make up

calculate/work out

cause/bring about

discover/find out

discuss/talk about

emerge/come out

eradicate/stamp out

increase/go up

maintain/keep up

organize/set up

propose/put forward

select/pick out

However, most phrasal verbs are neutral, neither informal or formal,
and in general there's no reason to specify they shouldn't be used in
formal writing. In fact, in some cases it's more appropriate to use a
phrasal verb in place of a single verb. For example, the phrasal verb
'carry out':
"Researchers carried out a survey into …" sounds much better for
formal writing than
"Researchers did a survey into …"
At the other end of the formality register, there are phrasal verbs
that are so formal they're only used in very formal or serious speech
or writing. If you were to use them in informal writing they would
very strange and out of place.
Examples of formal phrasal verbs

adhere to
appertain to
ascribe to
disabuse of
emanate from/to
depart from
engage in
enlarge on/upon
enter on/upon
offend against
permit of
pertain to
provide against
set forth

As always with writing, context is everything – remember to use the
language most appropriate to your audience. Your university,
organization, etc. will most probably have a guide to the language you
should use for formal writing, including their preferences for using
phrasal verbs or their single verb equivalents.
Summary
Often, single verbs are more formal than phrasal verbs and therefore
can be more appropriate for formal writing than their phrasal verb
equivalents. Nevertheless, phrasal verbs are very common in formal
writing. Offensive, slang, and informal phrasal verbs are not
appropriate for formal writing. Most phrasal verbs are neutral and
therefore, in general, there's no reason to specify they shouldn't be
used in formal writing. Some phrasal verbs are so formal they're only
used in very formal or serious writing. Yes, you can use phrasal verbs
in formal writing, as long as you choose those that are the most
suitable for your context or audience.
Comment: I upvoted for Elena, it's a solid well-organised answer (even if most is copied and pasted) but the listing of more formal equivalents is very helpful.
Comment: Thank you very much
Answer: Shoe's and Edwin Ashworth's answers are useful, but one thing I think can be added is that "phrasal verb" is not a very specific term, so you may need to get more specific.
In particular, many of the examples of "formal phrasal verbs" in those two answers are actually verbs that take prepositional phrases as complements.
I don't think "prepositional verbs" sound informal
Verbs like "abide by", "accede to", "disabuse of", "engage in", "enlarge on/upon" all fall into that category: according to most analyses of English syntax, the second word here is a preposition that does not form a phrase with the preceding verb, but forms a prepositional phrase with the following noun phrase.
I would say prepositional verbs do not have any special tendency to sound informal. Many formal latinate verbs take a prepositional phrase as their complement; in fact, there are verbs in Latin itself that work the same way. For example, accedo, the Latin verb that is the source of the verb accede, could take as its complement a prepositional phrase starting with ad (the Latin preposition meaning "to").
One thing to consider: the highly formal "pied-piping" construction found in phrases like "important problems to which we must attend" is fully compatible with prepositional verbs like "attend to". If prepositional verbs were inherently informal, it would be odd if they could be used freely in such a formal construction.
"Particle verbs" might sound informal, but not always
The other type of "phrasal verb" is what are also called "particle verbs": words where the verb is accompanied by a word that (usually) has the same form as a preposition, but that does not take a noun phrase as its complement. For example, in the sentence "You need to push in the tab using a screwdriver", the word "in" does not form a phrase with the noun phrase "the tab", which can be seen from the alternative word order "You need to push the tab in using a screwdriver." Traditionally, words like in were considered to be used as "adverbs" in this kind of sentence, but modern linguists may categorize them as prepositions used intransitively.
Unlike prepositional verbs, particle verbs do not have a close parallel in classical Latin (Latin verbs could be prefixed with prepositions, but they couldn't have prepositions used without nouns as separate words going with the verb). This construction is I think the main type of "phrasal verb" that might be felt to be informal. "Carry out" is a particle verb: we can say "carry it out", showing that "out" does not form a phrase with a noun in this construction. I don't actually find that "carry out" sounds particularly informal to me, but I have never tried to write with a very high degree of formality (as you see, I use contractions, another feature that is sometimes said to be "informal"), so you'll have to look at the usage in the community that you want to be a part of, as Shoe advised.
Comment: Thank you very much

Are all phrase verbs informal?