Serial NOR Flash - Vague

Question: What are the structural differences between Serial NOR Flash and Parallel NOR Flash? If there is a structural difference , then What are the differences between Serial NOR Flash and Serial NAND Flash?
I can't seem to get the resource for this particular question from Googling
Comment: Reverted to the original version with its mention of search attempts, as the user deserves credit for making an effort to research this question themselves before asking it.  Hopefully there will be fewer downvotes now.
Answer: Wikipedia: Flash memory has a pretty good explanation of the structural difference between
NOR flash and NAND flash.
NOR flash:

-- NAND flash
Both kinds of Flash memory use floating-gate transistors.
To read out a word, other stuff on the flash chip drives the selected word line to a "small" positive voltage.
When the floating gate is charged with electrons, it shields the transistor from the word line enough that the transistor stays OFF. So the resistor pulls the bit line HI, and the CPU sees a one (1) bit.
When the floating gate is erased, even that "small" positive voltage on the word line is enough to turn ON the transistor and pull the bit line to LO, overpowering the resistor, and the CPU sees a zero (0) bit.
NOR flash connects those transistors in a NMOS NOR gate.
To avoid interfering with the selected word line,
other stuff on the flash chip sets
the non-selected word lines to GND (turning their transistors off).
NAND flash connects those transistors in a NMOS NAND gate.
To avoid interfering with the selected word line,
other stuff on the flash chip sets
the other word lines to a "larger" positive voltage (turning their transistors on).
The pull-down path from the bit line to GND goes through many transistors in a NAND flash.
The pull-down path goes through only one transistor in NOR flash.
So NOR flash can be significantly faster than NAND flash (when built from equivalent transistors).
(But even NAND can be faster than a spinning hard drive).
As you can see from the purple chip cross-section, the NOR flash requires many more contact vias from the bit line down to the transistors.
Because NAND flash does not need those vias, the physical layout of NAND can be packed significantly less area per bit.
So NAND flash can cost significantly less than NOR flash (per bit, and when built from equivalent transistors).
(But even NOR flash costs less per bit than DRAM).
Both parallel and serial off-chip interfaces are possible with either NAND or NOR flash.
Execute-in-place applications (XIP) execute directly out of Flash.
All the bits of the instruction need to be fetched every instruction cycle, so such applications tend to use parallel NOR flash.
Solid-state disks (SSDs) tend to use parallel NAND flash chips.
Flash configuration memories are usually serial Flash chips. I think I've seen both serial NOR flash and serial NAND flash in this application.
(The pull-up is usually not a literal resistor. The details didn't seem relevant here.)
Comment: @davidcary I do understand the structure of NAND and NOR ('parallel connection of cells closely resembles to the parallel connection of transistors in a CMOS NOR gate, that's how it derives the name as NOR flash. In NAND-flash, cells are connected in series resembling a NAND gate, and so the name. The series connection prevents the cells from being programmed individually. These cells must be read in series.') Source:[HERE](http://www.eeherald.com/section/design-guide/esmod16.html) That's y after reading this i though there should be "structural" difference in Serial and Parallel NOR Flash
Comment: BTW, I wonder what the relation between pages, erase-blocks, and transistor-strings is.  I wonder if a "page" represents (once represented) one transistor on each of a whole bunch of strings, and an "erase block" represents a bunch of complete strings?
Comment: I read the article, but I don't understand certain aspects.  I can understand that the random read access time of NAND flash would be much longer than for NOR flash, but I don't understand why it would be limited to serial access.  The flash chip is going to be a 3d matrix (rows by columns by transistors in each string); at any given time, one can only access one row in a matrix, and one transistor per string, but is there any reason other than external pin-count limits why one should not be able to simultaneously read e.g. transistor #5 in each string on every column of row 28?
Comment: @supercat: I, too, am mystified. My understanding is that most SSDs use parallel NAND flash chips. Therefore parallel NAND flash chips exist. Therefore NAND is not "limited to serial access". How could I fix my text (or the Wikipedia article) to fight this common misunderstanding?
Comment: I don't know.  I suspect the main issue is that the long random access times inherent to a NAND-flash array have led chip designers to optimize their interfaces for sequential access; even if it were possible to design a chip which allowed a 5us on-chip random access time and a 20ns on-page random access time, that wouldn't offer much advantage over simply having a 5us random access time and a 20ns "fetch next byte" time.  Indeed, the sequential scenario may be faster if data from one page can be clocked out while the next page is read from the array into some latches.
Answer: Serial flash uses serial bus to write and read the data from the device. Popular serial buses include I2C and SPI. Serial signaling involves address, data and control signals on 2-3 wires.
Parallel flash uses parallel 8 Bit I/O or Bus to write and read the data from the device. Parallel signals needed are Data bus (usually 8 bit), address bus (depends on device density) and control bus (en, oe).
I could have added more details but the question is too generic, hence generic answer.
Comment: Thanks, I'm new to this technology and I thought the differences were present in the cell structure.. That's why my question included NAND flash which should be confusing to look at.
Comment: Now I know that the "internal structure" or so, as i called it, isn't the problem at all.. Your answer was just what I was looking for.. As I said I'm new to this tech, & I didn't even consider taking I/O access type in to account.
Comment: Cell structure can be explained by memory designers. I have worked in a memory company and usually the memory circuit designers don't discuss internals on newsgroups. Such questions can also answered by Si technologists (usually PHD guys)
Answer: I don't know what you mean by structural - if you mean the internal structure, I have no idea.
Yet, the main difference between serial and parallel NOR flash is the way the memory is accessed. Serial NOR Flashes are accessed via SPI, therefore having a low pin count whereas parallel NOR flashes are accessed via the usual data/address bus.
Check out the following:

http://www.spansion.com/Products/Serial-Flash/Pages/Spansion%20FL.aspx (Serial)
http://www.spansion.com/Products/Parallel-Flash/Pages/Parallel-NOR-Flash.aspx (Parallel)
Comment: Yeah I meant the cell structure( I thought the differences should be in this level as the low pin count I'd read about already didn't explain why it's "serial") Now that i learnt that it's SPI accessed, i can understand the interface differences. Thanks anyway..

Serial NOR Flash - Vague


Castle Monorail Databinding in an Action

Question: We have an issue whereby we have a download link on our website (running Castle Monorail) that downloads some data as a CSV. The Action method is as follows:
<code>public void TransactionReportSearch([DataBind("searchParameters", Validate = true)]TransactionSearchParameters searchParameters, int page,
                                        bool showStatistics)
</code>
Strangely enough, the databinding is working on our test environment but does not work on our live environment. We have discovered that the DataBindAttribute is working when we are doing a HTTP POST but it doesn't seem to be working on a HTTP GET. This of course could be a red herring as it is working on the test environment.
I suspect this could be a configuration issue. What should I check between the test and live environment to ensure that Castle Monorail databinding in the Action is configured correctly?
Comment: are you binding against Form? or QueryString?
Answer: I didn't test but can you try Databind's From=ParamStore.Params option. It says "From QueryString, Form and Environment variables.".


Explain the concept underlying the recent Serra-Lutz cold-to-hot experiment

Question: I'm trying to understand in a simple, non-mathematical way the basic concept underlying why a particular, very recent experiment turned out the way it did.
The experiment, by Serra and Lutz entitled 'Reversing the thermodynamic arrow of time using quantum correlations', demonstrated an interesting wrinkle in the 'arrow of time' and entropy concepts.
I understand this much: the experimenters took a chloroform molecule and cooled the Carbon atom and warmed the Hydrogen atom, and also created a correlation between the hydrogen and carbon atoms. Because this correlation constituted 'information', and information isn't just something in the mind of a human being but has a physical meaning in the world, this correlation/information represented 'organization' as opposed to 'randomness' and therefore the system in the experiment had-- as an initial value for entropy-- less entropy than would have been the case if there were no correlation between the H and C atoms in the nucleus. (I think I've presented everything up to this point correctly-- if not, please indicate exactly what errors I've made.)
Then, apparently two things happened next: the correlation between the H and C atoms decohered, and 'heat' flowed from the cold Carbon atom to the warm Hydrogen atom in the nucleus of the chloroform. Because the dissolving of the correlation was accompanied by an increase of entropy, heat was released, as is always the case when entropy increases. That much I understand.
What I don't understand (and what wasn't explained in either Serra and Lutz's paper or the article I read about their paper) is this: why, in this case, did the release of heat because of the loss of 'information' contained in the now-decohered correlation not just go into the environment and nothing more-- why was it accompanied by a flow of heat from the cold Carbon atom to the warm Hydrogen atom, which was therefore doing 'work' by creating less randomness and thus we see a lesser net entropy increase (Entropy increased by X amount because of the end of the correlation between H and C atoms, but entropy decreased by Y amount because of the flow of heat from the cold C to the warm H, thus reducing the net Entropy increase in the system.)
Why did that happen?-- and since it was predicted to occur, there must be some physical requirement for it to happen that is well understood by physicists. Could you explain it to me please? I'm wondering if the correlation that existed between the H and C atoms required that some of the heat generated by the dissolving of the correlation 'stay at home' with the correlated pair and be used to offset the decreased organization from the lost correlation by increasing the organization elsewhere if possible, and in this case that meant having heat flow from the cold C to the warm H. (That is sheer speculation on my part based on no knowledge at all!)
Here is a link to the Serra-Lutz paper: https://arxiv.org/abs/1711.03323
Answer: The energy flowed from one qubit to the other, instead of to the environment, because the qubits were set up to interact much more strongly with each other than with the environment. Namely, the two qubits were adjacent atoms on the same CHCl$_3$ molecule, so it makes sense that they would interact more with each other than with atoms on different molecules.


What is the best Layout to be used While designing for multiple screens and for both landscape and portrait

Question:
Hello! I have just started playing with android layouts and i wonder if there is a general way of applying basic layout so that it will adjust itself to multiple screens and automatically to landscape view. For example:
 In the picture above, I have added some buttons. Now what i want to learn is which layout or options(like weight,gravity,alignment) to b used so that they remain the same in Every view & on every screen. Some says to use linear layout within linear and then add weight and alignment. They said that by doing this, you have flexibility to remove any button and yet no other button looses its place(unlike in relative layout). Can there be better way that will have same layout on all screens and yet flexible??
Answer: You can use multiple linear layouts if you want to create a FORM.
otherwise Absolute layout is also good but not much preferable.
Relative layout needs practice, as you have to set widgets with respect to other.
multiple linear layouts may be useful.
Answer: RelativeLayout is very easy to use and if you learn to align the widgets in it, the layout will look the same on every screen BUT it's good for a layout that is very simple (few widgets on layout) or a layout that you know that will never change because changing on RelativeLayout is so hard and the best way is editing the XML not working on DesignView.
LinearLayout is not flexible like RelativeLayout but making change in it is so simple and other widgets will not lose their positions.
After all if you want to design layout for multiple screen size I recommend to use Fragments.


Is there a direct flight from Sucre to Uyuni in Bolivia?

Question: I've seen various references on online forums and websites to a direct flight from Sucre to Uyuni in Bolivia provided by Amaszonas since September 2017. But I cannot verify this. Does a direct flight exist?
Comment: I don't think that route is offered as a non-stop anymore. It used to be once daily M/W/F but now on those days I can only find an option with a long connection in La Paz
Comment: I sure don't see one on their web site!
Answer: Amazonas used to be the airline that did this.  However, their route map now shows this is no longer the case. Flight searches on search engines all seem to support this - you have to hop via say, Cochabamba or La Paz.


Is it Possible to Read stdout and stderr of Apps Launched From the Desktop?

Question: Suppose I launch Firefox from my apps. Is the stdout and stderr redirected to a specific file or is it redirected to /dev/null? If it is indeed redirected to a specific file, I'd also like to know how to how to run applications from the terminal (e.g. nohup, & disown) without knowing where to redirect stdout and stdin. In other words, how would I tell the desktop to launch an app, instead of launching it from terminal myself as a detached process. Of course, if the redirection is to /dev/null, then nohup APP >/dev/null 2>&1 and & disown is sufficient.
Answer: Typically the standard output & error from desktop environment components is redirected to ~/.xsession-errors or a similar file by default (may vary between distributions), and when you start an application like Firefox via GUI, it would inherit that redirection.
The standard input of a GUI application would typically be /dev/null.
But you can do whatever you want.
Redirecting to /dev/null is a valid option and a common choice, particularly if you aren't interested of any debug output a GUI application might produce on stdout/stderr, or know that the application in question won't produce any.
Comment: We're trying to relaunch the GUI from a post-install script. I guess I can always use a GUI command line argument to inform the app to relaunch. Thanks for giving me ideas.


Unit of work is driven by external event. How to ensure one unit starts only after the previous one ends?

Question: I am not sure how to refactor my app. I have read something about ChainedDefered, but I am lost at how to apply the technique to my situation. Any pointer/suggestions are welcome.
I am using a third party library to monitor some external data source which changes very rapidly in real time. Whenever a change is detected, the library will call a callback function in my code. My callback function will in turn retrieve data from database and perform some processing.
class MyApp(object):
    def start(self):
        for i in range(1, 1000):
            mycallback = CallBackHandler(x, y, z)
            thirdPartyLib.subscribe(event_name + str(i), mycallback)

     reactor.start()

class CallBackHandler(object):
    def __init__(self, x, y, z):
         ....

    def getSomeDataAndDoSomething(self):
        ...

    def __call__(self)
       callLater(self.getSomeDataAndDoSomething)

The problem is that the CallBackHandler can be called consecutively for numerous times when events happen rapidly in a very short interval. If these callbacks are executed more or less simultaneously, they will produce identical result.
How can I fire the callback iff the last callback has finished processing? I'd prefer to use constructs offered in twisted to achieve it instead of, says, by comparing timestamps of events (so drop callback if it has been fired 1 sec before) or a global variable as flag.
Answer: In the future, please include complete code samples.
If you want to execute something Deferred-returning with a limited level of concurrency, Twisted includes a class called DeferredSemaphore that you can use.
In 2006, Jean-Paul Calderone wrote a great blog post about how to limit parallelism with it.


Recursively search directories in C#

Question: I need to recursively traverse directories in C#. I'm doing something like this. But it throws exception when iterating through system folders. How to check it before exception is thrown?
Answer: You would have to check the access rights, but I would urge to to catch the exceptions instead, that makes the code easier to understand and would also deal with other issues like when you want to parse directories remotely and network gets down...
If you make a GUI for a directory tree you could also add some nice Lock icons on the places where you get access right exceptions and Error icons elsewhere... In C# there is already a nice free open source component for starting that.
If you want to count files and sizes there is no way to overcome the rights issue, you have to run your tool under a more privileged user.
Comment: Catching execption in recursive function can cause poor performance, can you perform a check to see whether a directory is accessible first
Comment: @Rohan, checking access to directory will require more code and overhead on cpu rather then trying to access directly and let exception fire, the reason is, the ACL is native win32 code, so when you try to check access to directory, you will indeed spend more time on marshelling data between win32 and CLR objects. It will not put any performance overhead against checking access.
Answer: I took a look at your link, and the code.  In the code sample, the try...catch construct is used to just stop searching when you get to a folder where you don't have permissions.
So based on this, my understanding of your question could be phrased as "How can I tell if I have permission to read a folder without trying to read the folder and throwing an exception if I don't have rights?"
If that's the case, then this related post will likely be helpful to you.
Checking for directory and file write permissions in .NET
Added
I would agree with @jdehaan's answer, but only after reading the link I posted for the reason behind the recommendation.
Answer: What type of exception are you getting?
If you are getting a SecurityException you should have a look at this example on MSDN

Recursively search directories in C#


intellij idea wsl 2 can't load projet from \\WSL.LOCALHOST\[distrib]

Question: With intellij idea version 2021.2.3, I can't open a project located in my Ubuntu WSL , path \wsl$\Ubuntu\home***
As soon as I point to the path the loading window closes
any idea ?
thank you by advane
it's work with Eclipse IDE.
I try this :
Here's how to do it (as of April 2023):
Open the IDE's property file: Help > Edit Custom Properties
Add the following on a new line:
ide.ui.new.file.chooser=true
Restart your IDE,
but not working
Comment: File a bug at https://youtrack.jetbrains.com/newIssue?project=IDEA with the logs attached (Help | Collect Logs and Diagnostic Data).
Answer: I faced this same issue and I figured out that the IntelliJ couldn't find the SDK (JDK) to load the project. I had no JDK in Windows neither WSL, so I had to install the the JDK in WSL and IntelliJ could find the SDK and load the project.
If the IntelliJ can't load the project even with SDK installed, try to open any other random folder and setup the SDK in Project Structure.


Get posts from a custom post type by child categories of a parent category

Question: I have a custom post type called guides, there are 3 categories a post can be within, the 3 categories are child categories of a category with id 87.
Currently I can loop through these categories and display their name and/or ID. I need to loop through each category and display the posts in that category. I can't seem to figure out how. This is the code I have that loops through the categories and displays their ID. In this loop I would like to display the posts. How can I do this?
$categories = get_categories( array(
    'orderby' => 'name',
    'child_of'  => 87,
    'order'   => 'ASC'
) );

foreach( $categories as $category ) {
    echo $category->term_id;
}

Answer: Your start looks already ok. You now need to get the posts which have the term_id of your $category.
$categories = get_categories( array(
    'orderby' => 'name',
    'child_of'  => 87,
    'order'   => 'ASC'
) );

foreach( $categories as $category ) {

    // display current term name
    echo $category->name;

    // display current term description, if there is one
    echo $category->description;

    // get the current term_id, we use this later in the get_posts query
    $term_id = $category->term_id;

    $args = array(
        'post_type' => 'guides', // add our custom post type
        'tax_query' => array(
            array(
                'taxonomy' => 'category', // the taxonomy we want to use (it seems you are using the default "category" )
                'field' => 'term_id', // we want to use "term_id" so we can insert the ID from above in the next line
                'terms' => $term_id // use the current term_id to display only posts with this term
            )
        )
    );
    $posts = get_posts( $args );

    foreach ($posts as $post) {

        // display post title
        echo $post->post_title;

        // display post excerpt
        echo $post->post_excerpt;

        // or maybe you want to show the content instead use ...
        #echo $post->post_content;

    }

}

As I pointed out, its not clear from your question if you are using the default "category" taxonomy of wordpress or a custom taxonomy.
As you can see this is just bare minimum code. So Iam sure you will need to extend it a little bit, for example adding permalinks to the post and stuff.
Also take a look at the codex regarding the get_posts() function.
Here you get some info about taxonomy query´s with get_posts().
For all usable taxonomy parameters visit the wp_query() codex here.
Here you will see that in some cases (for example if a post is in multiple sub categories) you can also use an array of ID´s instead of a single term_id, like so:
'field'    => 'term_id',
'terms'    => array( 103, 115, 206 ),


Methods of Learning Cryptography

Question: We're currently approaching the end of our semester, but I've found that our homework is starting to consist more of encrypting and decrypting using different types of algorithms instead of learning any other core fundamentals. Even though we've switched over from symmetric to asymmetric algorithms. I'm wondering if we're missing any other core fundamentals in a semester of learning cryptography? We've seemed to just focus on different types of algorithms this entire semester along with what aspects of cryptanalysis they meet. What else are we missing? (This is for personal use to learn more on the side)
Comment: Well…cryptography is a large field with many major conferences and journals, used by essentially every computer on the planet for a multitude of different applications.  So, your course certainly isn't covering it all!  There are some common textbooks, like Bellare & Goldwasser's lecture notes, Katz & Lindell's introduction, Schneier/Ferguson/Kohno's _Cryptography Engineering_, JP Aumasson's _Serious Cryptography_, Menezes/van Oorschot/Vanstone's somewhat dated but still useful _Handbook of Applied Cryptography_.  For a firehose, read the index of preprints at https://eprint.iacr.org.
Comment: I see "teaching" tag potentially useful to the site.
Answer: Learning Cryptography in academic is something between science and practice. For science part,the aim is to studying and focus on topics related to cryptographic primitives(building block of cryptographic protocols).Based on categorizing these primitives, we can learn them easily:

Unkeyed primitives-----> Arbitrary Hash Functions,One way permutation,Random sequences
Symmetric-key primitives ----->Symmetric ciphers(Block ciphers,Stream ciphers),Arbitrary length hash functions(MAC),Signatures,Pseudo-random sequences,Identification primitives
Public-key primitives------->public-key ciphers,signatures,Identification primitives.

In this category, fundamental Topics like signatures, Hash,Identification,Pseudo-random sequence generators highlighted. Also topics such as Authenticated encryption,secrete sharing and subjects related to key-management based on cryptography.
In the practice part, the intention is to design and implement a cryptosystem, which means that use the logic of cryptographic primitives in an algorithm and then evaluate its soundness based on mathematics. In this side, we can name topics as cryptanalysis and attacks(theoretic  and implementation),methods for designing a cryptosystem,Lightweight cryptography and ways of implementing ciphers and cryptosystems in different devices.
At the end, examination of different ciphers and cryptosystems, gives analyse and design method ideas and also the way of using them in real world.

Methods of Learning Cryptography


Mildew or Mold?

Question: There was a roof leak in our art studio. In the past few weeks this has appeared. Does this seem like it can be cleaned (with mold killing methods seen online) and repainted or does the drywall need to be cut out and replaced?

thank you!
Answer: Even if the leak has been stopped, the drywall might still be soaked. Let it dry, then wipe those spots with diluted bleach and paint over them. That should take care of the issue. If the area remains dry, there's little risk of the mold reappearing.
Answer: The only way you can really, fully answer this is by digging in to the wall to check the condition of everything behind the surface. If it's all saturated behind there, you might have ongoing problems with mold even if you bleach and paint over the spot. There's a couple other approaches you can take though. One is to get a moisture meter - they aren't particularly expensive - and use that to measure the drywall to see just how saturated it is. The other is to YOLO it, bleach the spot, paint over it, and deal with it if and only if the problems come back. For any of these approaches you might want to run a dehumidifier in the space for a few days first to draw the moisture out of everything.

Mildew or Mold?


algebraic series with transcendental conjugate

Question: Let $a$ be an algebraic number such that $|a|<1$ and $(d_k)_{k\in\mathbb N}$ be a sequence of positive integers. Assume that $\sum_{k\ge0}\frac{a^k}{d_k}$ is an algebraic number. Denote by $a_1,\cdots,a_n$ the conjugates of $a$ over $\mathbb Q$. Suppose that for every $1\le i\le n$ $|a_i|<1$. Is the series $\sum_{k\ge0}\frac{a_i^k}{d_k}$ an algebraic number for every $1\le i\le n$?
Comment: After your edit, the question makes even less sense. It's now unclear to me what you exactly want to ask. So I deleted my answer, which says nothing but the sum is $\frac 1{1 - a_i}$ hence algebraic. Edit: alright this last edit finally makes sense.
Comment: I made edit to my answer and now it gives you a counterexample.
Answer: No, not necessarily.

We first prove a lemma:

For every real number $x$ such that $0 < x < 2$, there exists a squence of positive integers $(d_k)_{k\geq0}$ such that $\sum_{k\geq 0}\frac{2^{-k}}{d_k} = x$.

Proof: we define sequences $(x_k)$ and $(d_k)$ recursively by:
$$x_0 = x, d_k = \lfloor \frac 1 {x_k}\rfloor + 1, x_{k + 1} = 2(x_k - 1/d_k).$$
To verify that this is well-defined, we show that $0< x_k < 2$ implies $0 < x_{k + 1} < 2$.
Since we have $\frac 1 {x_k} < \lfloor \frac 1 {x_k} \rfloor + 1 = d_k$, it is clear that $x_{k + 1} > 0$.
To show that $x_{k + 1} < 2$, we separate into two cases.

If $x_k \leq 1$, then we have $x_{k + 1} < 2x_k \leq 2$.
If $x_k > 1$, then we have $d_k = 1$ and hence $x_{k + 1} = 2(x_k - 1) < 2$.

Thus both sequences are well-defined and every $d_k$ is a positive integer.
By induction on $k$, it is easy to show that $x - \sum_{k = 0}^{n - 1}\frac{2^{-k}}{d_k} = 2^{-n}x_n$.
Taking limit $n\rightarrow \infty$, we have $x = \sum_{k\geq 0}\frac{2^{-k}}{d_k}$ as desired.

Now it's easy to give counterexamples to your question.
We choose $a = 1/\sqrt 2$ so that its conjugate is $-a$.
Choose a transcendental number $x$ with $0 < x < \sqrt 2$.
By the lemma, there exist sequences of positive integers $(u_k)$ and $(v_k)$, such that $\sum_{k\geq 0} \frac{2^{-k}}{u_k} = x$ and $\sum_{k\geq 0} \frac{2^{-k}}{v_k} = \sqrt 2 x$.
We define a sequence $(d_k)$ such that $d_{2k} = u_k$ and $d_{2k + 1} = v_k$.
We then calculate:
$$\sum_{k \geq 0}\frac{(\pm a)^k}{d_k} = \sum_{k \geq 0}\frac{2^{-k}}{u_k} \pm \frac{1}{\sqrt 2}\sum_{k \geq 0}\frac{2^{-k}}{v_k} = x \pm x.$$
Hence for $a$, the sum is $0$, which is algebraic, while for $-a$, the sum is $2x$, which is transcendental.
Comment: Very impressive. Thanks!!
Answer: Let $S$ be the set of sequences $d_k\ge 4^k$ such that $\sum_k \frac{(-\sqrt{15})^k}{d_k}=0$. It is uncountably infinite thus for most of those $\sum_k \frac{(\sqrt{15})^k}{d_k}$ is transcendental.
It is hard to give a concrete example because there is a natural norm on $\overline{\Bbb{Q}}$ which is $$\|x\|=\sup_{\sigma\in Gal(\overline{\Bbb{Q}}/\Bbb{Q})} |\sigma(x)|$$
If $(x_n)$ is Cauchy for $\|.\|$ then for all $\sigma$, $(\sigma(x_n))$ is Cauchy in $\Bbb{C}$. This way we can define $$\sigma(\exp(\sqrt{2})) = \exp(\sigma(\sqrt{2}))=\exp(-\sqrt{2})$$ even if $\sigma$ is not continuous $\Bbb{Q}[\sqrt{2}]\to \Bbb{Q}[\sqrt{2}]$. The completion of $\overline{\Bbb{Q}}$ for $\|.\|$ is weird, it is not the complex numbers, ie. in there $\exp(\sqrt{2})$ is not a complex number, it is the limit of the exponential defining series, not the same.
The common functions such as $\exp,\log$, the algebraic functions satisfy their properties in $\overline{\Bbb{Q}},\|.\|$ not only in $\Bbb{C}$, thus we can't obtain a counter-example to your problem from them. My dream is to use  $\overline{\Bbb{Q}},\|.\|$ to connect the properties (the non-trivial zeros..) of $L(s,\chi^\sigma)$ to those of $L(s,\chi)$.
Comment: This $\|\cdot\|$ is not a norm in the usual sense, as it is not multiplicative. The multiplicative norms are of course well classified.
Comment: In particular, you will not be able to show that the completion is a field. In fact it's easy to see what it looks like. Let's consider the restriction to $\Bbb Q[\sqrt 2]$. Then the completion of $\Bbb Q[\sqrt 2]$ w.r.t. this norm is nothing but $\Bbb Q[\sqrt 2]\otimes_{\Bbb Q }\Bbb R$, which as a ring is isomorphic to $\Bbb R\times \Bbb R$, hence not a field. This example of course generalizes to arbitrary number field $F$, whose completion becomes $F\otimes_{\Bbb Q }\Bbb R$, which is the product of $F_v$ for all archimedean places $v$ of $F$.
Comment: Therefore the completion of $\overline{ \Bbb Q}$ w.r.t. this norm is something like direct product (or sum?) of all $\overline {\Bbb Q}_v$, where $v$ ranges through all archimedean places of $\overline {\Bbb Q}$. The topology is perhaps something like weak topology, which I don't understand well. And the action of any $\sigma\in Aut(\overline {\Bbb Q})$ is simply permuting the components, hence not very interesting. I don't think this norm and the completion can be seriously useful.


How can I build a price feed oracle for my Substrate chain?

Question: What components do I need to implement an oracle for a Substrate chain, such as a price feed? I'm looking to understand the general steps and considerations I should make. What libraries or projects already exists that I could use?
Answer: There is an implementation of a price feed pallet in the Chainlink-Substrate integration. It connects to and uses the Chainlink oracle network to fetch the price feed.
You can follow a similar approach to build an oracle pallet to connect to any service or oracle for getting data in the chain.
Here is the code - https://github.com/smartcontractkit/chainlink-polkadot
Also, here is a good tutorial that explains the process - https://github.com/LaurentTrk/chainlink-substrate-tutorial
This could be a bit outdated considering the evolving code. But the overall approach still makes sense.
Also, as an alternative, you can look at Substrate off-chain workers for getting data via http calls. Here is a good overview - https://docs.substrate.io/v3/concepts/off-chain-features/
These are just some examples, and could be useful in understanding how to approach building your own price-feed or any other oracle integration.
Comment: I believe Sacha is asking how to build a feed oracle rather than how to connect to Chainlink
Comment: As I said in my answer, "You can follow a similar approach to build an oracle". The chainlink implementation is shared as a reference.
Answer:
orml-oracle pallet template from the Open Runtime Module Library (ORML), which is a community maintained collection of Substrate runtime modules, shows the foundations of how to create an oracle to make off-chain data available on-chain using off-chain workers.

substrate-price-oracle by Shawn Tabrizi shows specifically how to create an oracle that fetches off-chain price data and stores it on-chain using offchain workers.

pallet-chainlink-feed by Chainlink is a more complex example of how to create an oracle that fetches off-chain price data and interacts with a seperate token pallet for separation of concerns.

example-offchain-worker pallet and numerous online tutorials with Tomasz Drwięga show how to use an oracle to fetch data from an external API using off-chain workers and store it on-chain.


Methods for applying full color graphic decals to the surface of a 3d printed part?

Question: I'm trying to find a way of applying graphics to my ABS printed parts.
I need a robust method which can produce a decent amount of detail with true color and legible fine text .
I also was hoping to avoid the use of stickers and opt for something that's slightly more permanent.
I was wondering if there are ways in which a vinyl decal or other types of decal material could be pressed into the face of a plastic part and then thermally fuse the two layers together using heat transfer method?
Most of the surfaces I work with would be flat, but there are some parts that are slightly curved and it would be totally amazing if I could somehow apply graphics to those areas as well.
Thanks for any hints
Comment: [Computational Hydrographic Printing](https://www.youtube.com/watch?v=YlUhPrAqiY0) seems like what you're looking for, but given that it's quite experimental and not generally available, I'm not sure if it would make a good answer.
Comment: I'd look into silk screening.
Comment: Well that was just awesome! A little beyond what I'm hoping to accomplish, but thank you for sharing that
Answer: Industry has for years used a 'pad printer' to put images on complex shapes, like plastic or ceramic travel mugs, etc.
I have observed these, but never used one.  I see no reason why there couldn't be a DIY version made.
Best of luck, and I look forward to seeing what you come up with!
Comment: @kamuro [Pad printing is extremely common.](https://en.wikipedia.org/wiki/Pad_printing)
Comment: jcoats, welcome to the 3D Printing Stack Exchange site. I think your answer could be greatly improved if you have a design of one of these 'bad printers' in mind. To me, from your answer it is not clear how to proceed given I wanted to print graphics on an ABS part. Could you elaborate?
Comment: ups, misread that completely, as seen in what I wrote in my answer. Apologies. I would still want to encourage a written outline on how to build such a printer DIY.
Answer: I think this will work for you...
Laser Printer Image Transfer:

Print reverse image with color laser printer on regular paper.
Apply Mod Podge or artist arcylic or artist matte gel to the 3d printed surface.  You may need to sand it first to get it nice and smooth.
Apply same to picture and put picture, face down, onto the surface that you're transferring to.
Let dry.
Wash and rub off paper with water.
Apply protective clear coat...polyurethane or some other waterproof sealer.
...
Profit

This method has been popular in the DIY craft world for years so you should be able to google around for more tips.  My wife transferred pictures onto coasters this way...pretty easy.  Also, since paper is flexible, I think this would work on a simple curve.
Hope this helps.  :-)
Comment: Yep, very similar to toner transfer with PCBs...but without heat.  I've done PCB toner transfer with iron.  That process might work well if heat doesn't damage part.  Either way, dark parts would show through so black plastic may require a white or light colored coating under the image.  The final clear coat could be skipped, but it does make the image more scratch resistant.
Comment: This does sound like a neat idea to try. And I do currently have parts to do toner transfer (as I make PCBs this way). Just need a color laser printer.. Were the colors bright even when on black plastic? Does it scratch easily (reason for clear coating)?. Thanks.
Answer: You really can't. That said the only group that has this kind of tech is .. Disney of all companies. That said their tech is good at simple shapes. Nothing more.
I have seen some hydro transfer techniques. However that will not let you position a graphic as it is all done with a stretch transfer material ontop of a water bed. No one has a hand steady enough.
Realistically you either need a high end full color powered base 3d printer, or simple designs that you can apply with you hand, or paint by hand.
Well. Rereading your question... If you just want readable text. Then use a 2+ nozzle printer and print in colors that are contract. IE white model and black text. A lot more work but an order of magnitude cheaper than other options.
Disney article
Hydro transfer video


Selecting the Correct View for an Object Type

Question: I've had this problem many times before, and I've never had a solution I felt good about.
Let's say I have a Transaction base class and two derived classes AdjustmentTransaction and IssueTransaction.
I have a list of transactions in the UI, and each transaction is of the concrete type AdjustmentTransaction or IssueTransaction.
When I select a transaction, and click an "Edit" button, I need to decide whether to show an AdjustmentTransactionEditorForm or an IssueTransactionEditorForm.
The question is how do I go about doing this in an OO fashion without having to use a switch statement on the type of the selected transaction?  The switch statement works but feels kludgy. I feel like I should be able to somehow exploit the parallel inheritance hierarchy between Transactions and TransactionEditors.
I could have an EditorForm property on my Transaction, but that is a horrible mixing of my UI peanut butter with my Model chocolate.
Thanks in advance.
Answer: You need to map your "EditorForm" to a transaction at some point. You have a couple options:

A switch statement...like you, I think this stinks, and scales poorly.
An abstract "EditorForm" property in base Transaction class, this scales better, but has poor seperation of concerns.
A Type -> Form mapper in your frontend. This scales fairly well, and keeps good seperation.

In C#, I'd implement a Type -> Form mapper like this:
Dictionary <Type,Type> typeMapper = new Dictionary<Type,Type>();
typeMapper.Add(typeof(AdjustTransaction), typeof(AdjustTransactionForm));
// etc, in this example, I'm populating it by hand,
// in real life, I'd use a key/value pair mapping config file,
// and populate it at runtime.

then, when edit is clicked:
Type formToGet;
if (typeMapper.TryGetValue(CurrentTransaction.GetType(), out formToGet))
{
    Form newForm = (Form)Activator.CreateInstance(formToGet);
}

Comment: I think this will work great for me, and the ext. config file suggestion from you and Bill K will really make this nice.  Thanks!
Answer: You probably don't want to tie it to the inheritance tree--that will bind you up pretty good later when you get a slight requirements change.
The relationship should be specified somewhere in an external file.  Something that describes the relationship:
Editing AdujustmentTransaction = AdjustmentTransactionEditorForm
Editing IssueTransaction = IssueTransactionEditorForm

With a little bit of parsing and some better language than I've used here, this file could become very generalized and reusable--you could reuse forms for different objects if required, or change which form is used to edit an object without too much effort.
(You might want users named "Joe" to use "JoeIssueTransactionEditorForm" instead, this could pretty easily be worked into your "language")
This is essentially Dependency Injection--You can probably use Spring to solve the problem in more general terms.
Comment: I really like your comment about not tying it to the inh. tree, that makes a lot of sense in the scenario you describe.
Comment: I've had big problems with stuff like that in the past--using reflection to "Figure out" which things go together, but it makes stuff really inflexible.  Ruby's "make the common easy and the uncommon possible" fits too--binding classnames and the like breaks the second part of that rule.
Answer: Do I miss something in the question? I just ask because the obvious OO answer would be: Polymorph
Just execute Transaction.editWindow() (or however you want to call it), and
overwrite the method in AdjustmentTransaction and IssueTrasaction with the required functionality. The call to element.editWindow() then opens the right dialog for you.
Comment: He wants to separate the UI from the transaction state class.
Answer: An alternative to the Dictionary/Config File approach would be
1) to define a interface for each of the transaction editors.
2) In your EXE or UI assembly have each of the forms register itself with the assembly that creates the individual transaction.
3) The class controlling the registration should be a singleton so you don't have multiple form instances floating around.
3) When a individual transaction is created it pulls out the correct form variable from the registration object and assigns it do an internal variable.
4) When the Edit method is called it just uses the Show method of the internal method to start the chain of calls that will result in the display of that transacton editor.
This eliminates the need for config files and dictionaries. It continues to separate the UI from the object. Plus you don't need any switch statement
The downside is having to write the interface for each every form in addition to the form itself.
If you have a great deal of different types of editors (dozens) then in that case I recommend that you use the Command Pattern
You have a master command that contains the dictonary recommend by Jonathan. That commands in turns will use that dictornary to execute one of a number of other command that calls the correct form with the correct object. The forms continue to be separate from the object themselves. The forms reside in the Command assembly. In addition you don't have to update the EXE to add another editor only the Command assembly. Finally by putting things inside of Command you can implement Undo/Redo a lot easier. (Implement a Unexecute as well as a Execute)


Why did the Americans abandon kerosene after F-1 while the Soviets continued to develop it to very high sophistication?

Question: What is the reason behind America's switch to LH2/LOX, and (USSR's) Russia's decision to stay with it and develop it to spectacular technical sophistication such as the Oxygen-rich staged combustion technology used on RD-170 series? If LH2/LOX offers so clear an advantage in terms of $I_\mathrm{sp}$, then why did only Americans make the switch? The advantage of LH2/LOX seems to be partially offset by the complication of storing the deeply cryogenic LH2 and much heavier turbopump, which adds back some dead weight.
Comment: To be clear, the US never stopped working with kerosene--it just wasn't used on the main launch platform: the Space Shuttle. And since then it has reentered mainstream use with the Falcon rockets.
Comment: Many rockets used kerosene in the first stages, particularly the Delta and Atlas families. NASA thought at first that the Space Shuttle would be taking everything into space, but after the Challenger disaster the expendable rockets made a comeback. So I think we can say that kerosene was always mainstream except for a brief hiatus in the Shuttle era. LH2/LOX has been long been popular in upper stages.
Comment: For the record @called2voyage, it has been in near continuous use in the US. Atlas has always used Kerosene.
Comment: @PearsonArtPhoto Yeah, that's what I was referring to--thanks for clarifying.
Comment: @Greg Yeah, mainstream probably wasn't quite the right word perhaps "flagship" would have been a little more accurate.
Answer: Each technology has their own strengths and difficulties. It's really difficult to explain this without going in to a great detail about how rocket engines work, but let me try and give a brief overview.
There are a number of different ways you can power a rocket engine. In general, for the same fuel and engine size, the higher the chamber pressure, the more thrust you get. To get the highest thrust you need to pump it. This is usually done with some degree of rocket fuel. One of the biggest problems facing high efficiency rocket engines is what do you do with the exhaust from this system.
The most efficient rocket engines will use the exhaust from the rocket as exhaust itself. Many less efficient ones will simply throw the exhaust away. The basic idea to using the fuel itself somehow is in only partially burning the fuel, either a fuel rich or an oxygen rich method.
The fuel rich method for kerosene leads to a lot of carbon, which can clog up the engines, and thus isn't desired. The way the US and Russia overcame this problem diverged down two very different paths.
The US path was to switch to hydrogen, which is more efficient in and of itself, and won't deposit any carbon. The Soviets figured out a way to go oxygen rich by inventing new alloys that could handle the very hot very oxygen rich combustion. Both of them have a lot of complexities, it really just came down to the path each decided to go down.
Lastly, which of them is fundamentally better? Theoretically kerosene is better for a lower stage, because it offers more thrust, and hydrogen/oxygen for the upper stage, because ISP matters more once you leave the gravity of the Earth.
BTW, the Everyday Astronaut has a video coming out about the strengths of the 3 main rocket fuels coming out soon, keep an eye out for that! The video will be more focused on Raptor, which uses Methane, but...
Comment: @PearsonArtPhoto I understand what you mean. $T=\dot{m}\cdot\Delta v$, LH2 is very good on the second term but only $7\%$ as dense as water, while kerosene is $80\%$  as dense as water. So a kerosene rocket will be less bulky but heavier than an LH2 first stage given that they lift the same upper stage flying the same mission.
Comment: nice answer; good clear explanation.


Live Corner Illustrator

Question: Is there a way to restore live corners in a shape? For example when I expand a text or object, sometimes the symbol of dynamic corner doesn't appear.
Answer: The corner widget has a hard limit of 100 handles of the current selection. When you expand your text, if it generates more than 100 handles, the corner widgets will not appear. You can select a few letters at a time and it should work as normal, so long as the number of selected handles does not exceed 100.
Answer: I think you are referring to live corners.
In that case you just need to go under the View menu and down to Hide/Show Corner Widget

I would also recommend checking out Adobe's site on the topic

Live Corner Illustrator


What does it mean if I am non billable on my project yet a useful resource. Will they fire me?

Question: I work as a non billable member in my company. But I complete my tasks assigned to me on time for my project. Is there a chance that in future my company will fire me just because I am non billable?
Comment: Is your job by definition non-billable? Or are you assigned some internal tasks to keep you busy?
Comment: Did someone tell you that being designated non-billable would somehow lead to your termination? Where did you get this idea from?
Comment: @esqew it seems fair to assume that being non-billable (different from non-valuable, but still) could drive you to be in the first to go out if money comes short...
Answer: No.
It's simply a cost code and I wouldn't worry about that, this usually means that the work you do isn't billed to the end customer but is internal only. Individual projects within the company might well have their own cost codes so that they can track use of resources against projects.
Ask your manager or team lead for clarification on what this means for your company and role.
Comment: You might also hear "direct" and "indirect" which mean the same thing.
Answer: In some other answers I talked about the existence of so-called "bullshit jobs". However I still think that in a lot/the majority of the cases all people who work at a company contribute something essential to it. Nobody is employed just because they are such a nice guy/gal. If the cleaners wouldn't clean the office of your company it would soon become such a mess that people cannot work there anymore. Whatever tasks you are working on are probably needed for the "billable" persons to do their work or is in some other way essential for the company. So the distinction between "billable employees" vs "non-billable employees" and "profit centers" vs "cost centers" is actually hogwash. In most cases all employees do important work that makes it possible for the company to earn money. Personally I think that categorizing some employees as "non-billable" or working in "cost centers" is disrespectful to them.
Comment: I must say I subscribe to this idea of bullshit jobs. But non-bullshit jobs may not be essential to any company as such. And non-billable doesn't mean bullshit or non-bullshit job. I don't see how being in a "cost center" is disrespectful. Everybody should be reasonable enough to admit that some costs are necessary and/or happily paid because of the service they provide, still they are costs. That's a fact, not a sign of (dis)respect...
Comment: I think it's disrespectful because the distinction is made between employees working in "profit centers" vs employees working in "cost centers". All employees have costs associated with them in the form of their salaries. But as I explained in my answer all employees contribute something useful to the company as well.
Comment: @thieupepijn: billable means that the employees hours are directly passed along to clients, non-billable means they aren't.  It's an important factor in project planning.  It doesn't of itslf mean that the employee is less or more valued. Depending upon the project and the employee it can easily go either way.
Answer: Yes.
I mean, they're not going to just up and fire you for spite for being non billable (unless you work for a purely consulting company in which case they may). But in any organization, when hard times come, the first cuts are always in cost centers, not profit centers.  So on the whole, working as a source of cost carries less job security than if you were directly contributing to revenue.
That doesn't mean you're sure to get fired for being in a cost center, but if you are comparing the two in terms of job stability, profit always comes first.
Comment: When you're a contractor, and your job title changes to "contingent worker" after your initial contract period is up, that's when you know you're in trouble!
Comment: not sure why this is down voted
Comment: I don't know either.  I will do a drive-by up-vote.
Answer: The answer is yes, no, and maybe.
Within some companies tasks can be classified as billable or non-billable. Some employees are almost always billable, or almost always non-billable. Many are a mix.
You see this type of designation when the bulk of the income from the company is through tasks/contracts with a customer. You see this with government contractors. But it can also be done with other types of business. An auto repair shop can only use the time of the mechanics to bring in income. A law office only generates income from the work of lawyers and other similar employees.
In these types of companies everything else needs the billable hours to be maximized to be able to pay their salaries and benefits. This non-billable work is still vital. This non-billable work is still valuable. These jobs can include accountants, sales people, security, warehouse, and management. Of course management has to watch all expenses to be able to pay all the employees, and all the expenses from the billable hours.
Companies that have large percentage non-billable employees can struggle. Each billable employee needs to be 100% billable, or they need to charge a very high rate to fund the rest of the operation. If they need too high of a rate they can lose the ability to when new contracts.
Some tasks being done by highly skilled employees can be non-billable. Some companies have internal teams doing research and development to create new products. These new products can later generate new business, or can be used to allow company employees to be more efficient and therefore generate more income per hour.
Yes it is true that non-billble employees are generally the first things that can be cut if money is tight. But billable employees are also vulnerable to job cuts. If they spend too much time in an overhead state while waiting to be put on a contract, they may find their only option is a change of position or unemployment.
Some employees are mixed. In companies I have work for the first level of management is expected to be moistly billable. The rest of their hours are doing management and business development tasks that the customer won't pay for. As their empire grows their expected billable percentage is reduced. Once they start having mangers working for them they rarely have billable hours. Of course if their empire suffers enough losses in business they may find themselves back to doing billable work.


What is the tipping point for "non sequitur"?

Question: What is the point at which a non sequitur morphs into the incongruous?  Is it predicated upon contextual ideas leading up to the statement, or is it subjective based on the conclusion of the idea being propagated?  I'm just curious if there are any hard/fast rules, or is it subjective -- like finding something funny or not?
Comment: It's 42, obviously.
Comment: I still think this question could benefit from more context. What do you mean by "incongruous" here?
Comment: Er, false dichotomy here.  Hard and fast rules, *or* subjective?   I think we will find the truth lies somewhere between the two (though in my opinion, 2/3 or the way towards *subjective*, or perhaps 3/5ths.)
Answer: I see it as somewhat orthogonal, though often related. incongruous means "not in harmony or keeping with the surroundings or other aspects" (New Oxford American Dictionary), while a non sequitur is something that doesn't follow logically from the premises. A non sequitur is thus often incongruous, but might not always be: in a series of collected non sequiturs, they would not be incongruous.[1] Nor would a non sequitur be incongruous if the speaker were known to be subject to dementia.
For me, the distinctive element is: incongruous is linked to the absence of harmony, while non sequitur relates to the absence of logic.
Note [1]: I believe there are quite a few comic strip series that follow this scheme, but can't think of any (in English), so suggestions in comments would be welcome.
Comment: I was thinking of comics, Will Ferrell springs to mind, who have made millions straddling the border between the two...good call
Answer: A non-sequitur is always incongruous, in that it does not follow (literally) from the preceding conversation.  Did you have something more specific in mind?
Comment: Any particular reason for the downvote?
Comment: He or she didn't like that shade of plaid.  I do happen to have some votes here, however....
Answer: It is 100% subjective. The connection may make complete sense to me, the speaker, while you as the listener simply "don't know what I'm talking about". To you, it's a non sequitur, to me, I'm just speaking within my own world view and not bending my speech to ensure that it will be close enough to yours that it "makes sense".
"+42"


Anisotropic effect doesn't work (blender 4.0)

Question: I faced with the problem that anisotropic effect doesn't applies neither using eevee renderer, nor cycles. Could you help me? File is attached
Answer: It works fine but you need to be in Rendered preview mode and in Cycles. The Material preview uses Eevee and Anisotropic doesn't work in Eevee (as indicated here):
Answer: Anisotropy only works with cycles (as indicated here). You need to be in render mode in order to use cycles. In the image you sent, you are in preview mode, so you'll have to switch modes

The default world scene is dark and unlit, so you wont see anything. Lighten your scene so you can see the effect


Can I replace a single corrupted block?

Question: I'm running Bitcoin Core on Linux and it seems I have a single corrupted block file which is causing problems. It's taken me 2 weeks to download 75% of the blockchain, so I'd like to replace the individual block itself and duplicate the entire chain into a new folder if I can, rather than start again from the beginning. My guess is for somebody who isn't a Linux noob this would take moments but I still get lost quite fast ATM! The block file in question is blk02425.dat
What I can't seem to do is download a single block on its own in the necessary format. Noob-centric help most welcome and if you like please send a lightning address and I'll zap some appreciation.
Comment: Can you post log files that show the error you are encountering?
Answer: Upon checking my node, the file blk02425.dat has a size of 127 MB. While it might be technically possible to share and download this file online, I would not recommend doing so. Note that the file does not consist of just one block, but rather has numerous blocks compressed and combined in a specific format. The format of data can vary depending on the specific version of Bitcoin used to create it.
Don't Trust, Verify: For ensuring the accuracy of blockchain data on your node, I would recommend you to use your own hardware and follow the standard synchronisation process to download and verify the complete blockchain data.
It is an intriguing idea to consider if an attacker would be able to manipulate and inject inaccurate transaction data into a node through this method. Such an attack would require significant technical expertise. Any attempts at such an attack would be likely heavily scrutinised and detected by the wider bitcoin network, which could result in the banning of your node.
Would you rather wait for the complete download and verification of the blockchain by your hardware over one month or take the risk of your node getting banned and operating your node with incorrect data?
Comment: A bitcoin node builds the blkxxx.dat files as it hears about new blocks on the network, and it will most likely not hear about those blocks in sequential order. The result is that every node will have a unique set of blkxxx.dat files, as they will have received blocks in a unique order. So copy/pasting a subset of those files isn't going to work, in any case. What OP is asking about is different though: re-writing a single block's info, with the assumption that OPs node will then still validate this block's info itself (ie, not just trusting someone else's file).

Can I replace a single corrupted block?


Change the input format in drupal 8

Question: I would like to know how to change the input format (automatically or by sql ) for all articles in my website, because I migrated from D6 to D8 and I face a nasty bug that requires to edit all my nodes (more than 2000) manually and set either filtered HTML or FULL HTML format to all nodes.
Answer: Thanks to No Sssweat. His answer works. But I prefer to use sql so here it is.
Using Phpmyadmin navigate to node__body table (or just search it) then in SQL tab, write this:
<code>UPDATE `node__body` SET `body_format`='full_html' WHERE `body_format`='full_html1';
</code>
Please notice the following:

in my case, I use different body format in my website so it is not good to change all body_format to full_html.
after the migration I got full_html1, but you may get different body_format.

After execution the SQL command, Clear Drupal cache
Answer: In node click the (+) and you will see more tables. For example: node__body

All you gotta do now is export this table as a CSV. Open the file on Microsof Excel. Then CTRL+F click on the replace tab, and replace filter_html with full_html. Save and import back to database, check mark replace data option. Then in Drupal clear the cache.
Comment: Thanks, it works. What I missed before is clearing the cache.

Change the input format in drupal 8


System of equations $x + xy + y = 11$ and $yx^2 + xy^2 = 30$

Question: I have problem with solving this one.
Total number of solutions from system of equations?
\begin{cases}
x + xy + y = 11 \\
x^2y + y^2x = 30
\end{cases}
There is a system of equation and I have tried to get some normal solutions, but I always get the fourth degree polynomial from which I do not know how to get simple 'x's and 'y's. I know that task asks me to just find total number, but I would like to know which solutions are those. This is adjusted for high school mathematics level.
Answer: make a change of variables $$x+y = u, xy = v. $$ then the equation in the new variables are $$\begin{align}u+v = 11\\uv = 30  \end{align}$$
this has solutions $$u = \frac{{11}^2\pm\sqrt{{11}^2-4 \times30}}{2}=6,5\quad v = 5,6$$
and $$x, y = \frac{u^2\pm\sqrt{u^2-4v}}{2}. $$
Answer: try substituting $p=x+y$ and $q=xy$
this will give you a simple quadratic for $p$ and/or $q$ and then some more quadratics for $x$ and $y$
Answer: Hint:
This can be written as $xy(x+y)=30, xy+(x+y)=11$.
First solve for $x+y$ and $xy$, then for each of those solutions, solve for $x,y$.
Answer: Hint: Use the substitution a=x+y
and b=xy.
Thus your two equations become a+b=11,   ab=30.
Can you solve the above equation, and from that solve for x and y?
Answer: There are exactly $4$ solutions (over characteristic zero), namely $(x,y)=(1,5),(2,3),(3,2),(5,1)$. To see this, note first that $y+1\neq 0$. In fact, for $y=-1$ the first equations implies $11=0$, a contradiction. It follows that $x=-\frac{y-11}{y+1}$. Substituting this into the second equation gives
$$
(y - 1)(y - 2)(y - 3)(y - 5)=0.
$$
Answer: x+xy+y=11             (i)
x^2y+xy^2=30          (ii)
from (ii)
xy(x+y)=30            (iii)
from (i)
xy= 11-(x+y)          (iv)
put value of xy in    (iii)
11-(x+y)=30
let x+y= z
therefore, (11-z)z=30
therefore, 11z-z^2=30
z^2-11x+30=0
solve for z
you will get z=5
<code>      or  z=6
</code>
therefore, x+y can be equal to 5 or 6
as 11-(x+y)=xy
therefore, we will take cases
case 1
when x+y=5
then, xy=6
the only two cases thus formed are {2,3} and {3,2}
here we cannot take x or y = 6 because in (ii) it is clearly given that x^2y+xy^2=30. if x is 6 then {x^2y+xy^2} is greater than 30 which is not possible.
case 2
when x+y=6
then, xy=5
the only cases formed are {5,1} and {1,5}
so the final answer would be {1,5}; {5,1}; {2,3} and {3,2}.
hope you are clear with the solution..
Comment: https://math.meta.stackexchange.com/q/5020/306553 mathjax reference


Sealing siding around a chimney

Question: I have water coming in from around my chimney. The roofers didn't finish it, unfortunately I just bought the house so I need to fix it myself. What's the easiest and best solution to sealing off the top of the siding around my chimney? Pictures are attached. Thanks.
Answer: You need to install aluminum or copper flashing all around chimney perimeter that would overlap vertically down from the top of the siding by at least 5–10 inches down.
You would need to grind out a thin continuous horizontal channel 1-1.5 inches deep in the mortar seam directly above where the siding top terminates. Get a roll of aluminum flashing and unroll enough + a foot or so extra to go around entire chimney perimeter.
You'd then create a slightly more than 90 degree bend along the entire length of the flashing (it will look like a upside down "L" shape. You can use a long board and a rubber mallet to do this. The little horizontal part of the L will tuck into the channel and the long vertical part of the L will extend over and down the siding. At the corners of the chimney, you will make a vertical snip across the part of the "L" that tucks into channel so that the long part will be able to bend 90 degrees and wrap around the corners. At the end, you want to overlap the end of the flashing onto where you started by at least 6 inches. Put some tripolymer sealer underneath and secure seam with either rivets or small self-tapping downspout screws. You'd then fill in the channel in with mortar.
This is the crude way of doing it if you don't have access to a metal hand break. If you can get access to one, you can create fancier shaped flashing that will have a little kick-out at the bottom to allow the water to roll off at the bottom easier.
Comment: Metal hand breaks are usually available at rental shops.  Using them to make nice shapes is the hard part, the first time.
Comment: Yes - I suggest cutting up a bunch of short lengths of metal and practicing. Depending on rental price, may be cheaper to hire someone that would do it quicker

Sealing siding around a chimney


Any way to share certain folders to certain users in workgroup network with 11 PCs?

Question: So we have 11 PC workgroup network and a server without AD DS with windows server 2012 operating system. Is there any way to share folder1 to user1 and so on without setting up domain and active directory? currently there is a entire partition shared to everyone and users cause mess in files. also in sharing option i can only see local users on server not every workgroup PC on network. i would be very thankful if someone could help me. thanks. All PCs use Windows 10.
Comment: Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.
Comment: I really suggest you install Windows server, if financially it's too much, setup a Linux samba sever for minimal cost. I think 11 pc's is a bit much for a workgroup, others may disagree.
Answer: Yes, it is actually done mostly the same way as with AD – the only difference is that you need to manually create all the user accounts on your "server" system.
(You can use the regular Windows 10 user panel, but it will be easiest to do so through lusrmgr.msc or the net user command. Don't forget to set "Password doesn't expire".)
Once user accounts have been created, the rest is the same as with AD. Remove Everyone or Users from the folder's (and/or the share's) access list, then replace it with access entries for individual users instead. (Might be better to create a group for this purpose.)
In a workgroup, clients will be prompted to enter the username/password when connecting to your share. Though if you make sure that the usernames and passwords on your "server" exactly match those of the clients, then connections will happen automatically (just like with AD).
Finally, if you want to prevent those users from logging in to the server directly (or via RDP), you can configure that through secpol.msc "User Rights Assignment".
Comment: you need to manually create all the user accounts on your "server" system. ..... I am well used to this approach and it works great up to Windows 10. I have not yet been able to use this for NET USE from Windows 10 to Windows 11 (all Pro).
Comment: I see no reason why Windows 11 wouldn't work, given that it is basically just rebranded Windows 10, while the basic concept goes all the way back to WinNT3 (it worked between Win2000 and XP, it worked between XP and Vista, it worked between Vista and Win7...)
Comment: It all worked from XP to Windows 10. But on Windows 10 Pro - NET USE T: \\Windows11\folder does not even see the machine. I have been working at this for a while without success. Windows 11 NET USE T: \\Windows10\folder is fine.
Comment: "Doesn't see the machine" goes beyond accounts. If it cannot resolve the hostname, that's either a LLMNR or DNS problem. If it can resolve the hostname but not connect (or cannot negotiate a common SMB version), that's probably SMB being turned off in general. Accounts don't factor into that. (Either way, it's a separate thread.)
Comment: Hi again. i tried and it doesn't seem to work properly. i did make local user account with same name and password as on local user machine but it doesn't apply the permissions i'm setting for that user. maybe the problem is in windows server 2012 os while all machines run win 10?. the folder is sharing is working only for built in group(everyone,users and other groups).
Comment: i can make domain and set ad ds by the way. i just wanted an easier solution.
Comment: Does your client actually _log in to the share_ as the correct user? What user do you see in the session list of `fsmgmt.msc`?
Comment: i finally made it work. thanks


What is the effect of the wavelength on the spectrophotometric measurements of protein?

Question: Does the wavelength setting affect the absorbance reading of a spectrophotometer? For example, if I am using a spectrophotometer at 550 nm to determine the protein concentration of my samples, would my results be different if I analyze them at 500 nm?
Comment: I don't understand your question, can you clarify it?
Comment: The change in absorption due to concentration (Beer's Law) is the most at the wavelength of maximum absorption. But using another wavelength should give you similar results, but they would be so accurate.
Comment: correct me if I'm wrong. The change of the wavelength would result in a lower absorption, but it will be similar to the one with the bigger wavelength.
Comment: Molecules will have a certain range of absorbance with a peak at a certain point. A wavelength longer than the peak absorbance and shorter than the peak absorbance will result in more light being recorded by the detector. You can determine peak absorbance by taking several readings of the same sample  and varying the wavelength of the spectrophotometer. you will need to make very small changes around the peak to find the exact peak wavelength, but you should be able to find it this way. On the opposite sides of the peak, absorbance will fall off to near 0 if you have calibrated for solvent.
Comment: @AMR perfectly described what I mean by wavelength of maximum absorption. You should do your analysis at this wavelength. But if you do it at another wavelength, then it will give you similar results but the result would be less accurate.
Answer: Light absorption happens because of interaction of light with electrons (in a way) such that the energy of the light is transferred to some electrons that moves them to a higher energy state.
As per quantum chemistry (Bohr's model of hydrogen can be referred for a basic understanding), there are distinct energy states (solutions of the Schrödinger equation) and there are no intermediate levels. Therefore, to excite an electron to a higher energy level the energy of the incident light should match the energy gap between the ground state and the excited state.
In a molecule, there are different electrons, that reside in different orbitals and environments; only a few electrons can be exited by the energy that UV-Visible range of the electromagnetic spectrum can provide. These electrons are typically referred to as chromophores. You should refer to a book on spectroscopy for more details. A molecule can have multiple chromophores and each may absorb a different wavelength.
Having said that, there are energy bands (multiple closely spaced energy levels) in the molecule instead of fixed energy state which allows absorption in a range of wavelengths around a value at which the absorption is maximum. The wavelength vs absorption graph will give a peak at the maximum (which usually looks symmetrical but not always necessarily be so).

 From ChemWiki

The width of this absorption band would differ between different chromophores; so in your hypothetical case, some chromophore which has an absorption maximum at 580nm may absorb 530nm while another chromophore with same maximum, may not.
The Beer-Lambert's law will hold for all wavelengths that can be absorbed i.e. the absorbance would be proportional to the concentration of the molecule (unless there are complex phenomena like energy transfers that may be dependent on concentration; this is unlikely in dilute solutions).
As a practical suggestion, I would say that if your spectrophotometer has fixed options then choose the wavelength that is closest to the absorption maximum.
If you see the above example graph and let's say your aim is to quantify nitrophenolate in a mixture of nitrophenol and nitophenolate. Then a measurement at 350nm instead of 400nm would give you erroneous result. In other cases a 50nm difference may not matter (for e.g. measuring at 450 for the nitrophenolate). It all depends on what you are analysing. You should know the molecule that you are analysing.
Comment: @AMR We are not even arguing which is the best atomic model. I had mentioned Bohr's model because it is easy to understand for a beginner in spectroscopy. Though it is obsolete, the fundamentals that describe energy levels are not incorrect even though they are applicable only for hydrogen atom. I cannot take the OP through a course on quantum mechanics. Nothing that I had said is misleading I guess; however, for your satisfaction I made the edit :)
Comment: The Bohr model is only valid for hydrogen. However the Schrödinger Equation takes into account all the rest... so I would probably edit, to just mention Schrödinger.
Comment: From Chemistry 8th Ed - Zumdahl & Zumdahl "At first Bohr's model appeared very promising. The energy levels calculated by Bohr closely agreed with the values obtained from the hydrogen emission spectrum. However, when Bohr's model was applied to atoms other than hydrogen, it did not work at all. Although some attempts were made to adapt the model using elliptical orbits, it was concluded that Bohr's model was fundamentally incorrect."
Comment: I would probably have mentioned something about conjugated systems reducing the energy of the photon needed to get the electrons to change energies, resulting in "absorbing" longer wavelengths and probably not worried about mentioning Bohr and the Man with the Cat, as the OPs lab exam is more likely to have a question about why PNP can absorb light in the visible spectrum that about quantum theory,... but then that is just me.
Comment: @AMR Conjugation is just one case but there can be several ways including splitting of orbitals, interaction with solvent or other dipoles in the molecule, etc. That will go in a different direction altogether. Best to avoid that IMO.
Answer: In addendum, keeping the wavelength around the absorption maximum for the light-attenuating species avoids introducing error into Beer's Law. There are limitations to the law, outlined here where we can see that around the lambda max, there's little change in absorption per unit wavelength:

In case B, this would end up returning a bad extinction coefficient! You can experimentally determine this point either by testing the solution at different wavelengths or more accurately, running a program where the machine goes through it's entire wavelength range and measures absorption for you. You'll get a parabola where the maximum is your lambda max, so it's solvable by calculating the maxima if necessary (take the first derivative, set y'= 0, solve for y when x = (y'=0) for the associated ordered pair). You also want to be careful when you're using something like the Bradford assay where the bound form of the dye shifts the lambda max!
Comment: Nice information +1. However, in an experiment I would not expect the wavelength of the incident light to change (if the light is monochromatic). Also, I do not understand Figure B. Why would absorbance vs concentration become non-linear for non-λmax wavelengths?
Comment: I think this is the explanation [here](http://www.chem.uoa.gr/applets/appletbeerlaw/appl_beer2.html). As far as the math goes I'll admit I'm not actually 100%!


Unwanted slug in my website

Question: There is an unwanted slug /question/ in my WordPress website. Slugs are automatically changed to /question/ when I open many pages. I have thoroughly checked my phpMyAdmin and I have no /question/ slug on my website. My .htaccess also have nothing other than standard piece of code.
Though I have a custom post type /questions/ but it does seem to be a problem.
It's very very annoying because when I open my custom login page www.ideabroad.com/sign-in/, it also change to www.ideabroad.com/question/.
Any help would be greatly appreciated.
Comment: Post the code that you use for rewriting your custom post type URL's
Answer: Looks like your canonical URL is set to http://www.ideabroad.com/question/. I suspect your Yoast SEO plugin is doing this. You need to reconfigure it appropriately.

Unwanted slug in my website


Lost phone contacts after deleting Gmail acount

Question: How can I restore my Gmail account once I've deleted it and it's been almost a month since I deleted from my iPhone 10? I have lost most of my important contacts and no other way to recover
Answer:
Recover a recently deleted Google Account
If you deleted your Google Account, you may be able to get it back. If it's been a while since you deleted your account, you may not be able to recover the data in your account. If you recover your account, you'll be able to sign in as usual to Gmail, Google Play, and other Google services.

Follow the steps to recover your account.

You'll be asked some questions to confirm it's your account. Answer as best you can.
If you're having trouble, try the tips to complete account recovery steps.

If your account is recovered, create a password that you haven't already used with this account. Learn how to create a strong password.

https://support.google.com/accounts/answer/6236295?hl=en


Income tax code changes mid year - what exactly is your personal allowance for the tax year?

Question: Suppose that your United Kingdom tax code changes mid way through the tax year e.g. your spouse successfully applies for the marriage allowance, which increases your personal allowance. Does this mean that your personal allowance is updated so that, for the current tax year, your 'old' personal allowance is completely irrelevant? Or, is your personal allowance for the year some kind of mixture of the old and new personal allowances?
Comment: Just to note that you may have cause and effect mixed up here - it's your personal allowance that changes triggering a tax code change. The final liability to tax for the tax year is on the full year's income against a full year's personal allowance etc. The tax code+PAYE is intended to assist in collecting the right amount of tax throughout the year.
Answer: When you receive a new PAYE coding notice it supersedes any previous notices you have received for the same tax year.
The new coding notice will incorporate the changes from when they took effect. In the specific case of marriage allowance it applies to the whole year as your partner is effectively transferring some of their personal allowance for that year to you.
Useful references here and here.
Comment: Thanks for your answer. Looking at https://www.gov.uk/marriage-allowance I now see that it talks about receiving a tax credit rather than an increased personal allowance, so maybe there isn't technically a change in the recipient's personal allowance in this instance, though there is a new tax code.


Restrict user from entering tab in a textfield using regular expression

Question: I want to restrict the user from entering a tab in a text field using regular expression.
Comment: Is this field in a Lightning component, Visualforce page, a standard Salesforce page layout, or somewhere else? I think you can accomplish this in any of those scenarios, but the approach will be very different.
Answer: <code>[ ]{2,}
</code>
It will check 2 or more spaces
You could also check that before and after those spaces words follow. (not other whitespace like tabs or new lines)
<code>\w[ ]{2,}\w
</code>
The same, but you can also pick (capture) only the spaces for tasks like replacement
<code>\w([ ]{2,})\w
</code>
or see that before and after spaces there is anything, not only word characters (except whitespace)
<code>[^\s]([ ]{2,})[^\s]
</code>
To be specific about Tab, you can use. It will check 1 or more that once tab
<code>[ \t]{1,}
</code>


Can we create B2B eCommerce Website using SharePoint Online

Question: I have one requirement, to create a B2B eCommerce Website. I was thinking to check the possibilities with SharePoint Online. Or if anyone can recommend any other software.
I heard about magento is best for B2B eCommerce Site.
Answer: You can create eCommerce B2b website with SharePoint but you need to have SharePoint skills to actually work on that.There is no out of box template in SharePoint for this
I think if you need to create eCommerce website, Magneto is best option as you will get out of the box templates with which you can start working on. Some of  other  features of Magneto are

Magento B2B e-commerce includes all that you need for your online store – you can offer multiple brands through channel partners and key accounts, and seamlessly manage all your accounts
With Magento B2B e-commerce, you can carry out customer segmentation and tailor experiences to specific groups of companies or individuals based on their browsing behavior or purchase history.
Since B2B selling involves bulk orders at regular intervals, Magento offers a robust quotation system that allows buyers to request a quote.

You can then integrate SharePoint and your eCommerce platform to get more insight about your eCommerce website.
Example: Microsoft SharePoint has tools that allow the gathering of actionable business intelligence which gets better insight into the performance of your business and into what you might do to improve it.
Other platform you can use is Shopify , Wix, Volusion
Comment: Thanks for reply Amit, We have drooped the plan to use SharePoint. we are creating that using Magento.


Book found inside baneswood

Question: As I entered baneswood following the left side of the mountains in the forge lands. I came across a book on top of a post. I can't seem to find any information about it also I can't pick it up. I can move it around, but I can't put it in my inventory with all the other items. Can you please help me figure out what this book is?
Answer: It is part of the quest 'Makers Chronicle', which you can take after completing a side quest called 'Wandering Stone' (You have to find his 2 legs and 2 arms).
Note that 'Makers Chronicle' is available if you have the 'Death Rides' DLC.

If you talk to Oran after finishing the Wandering Stone side quest he will assign you with another one.  He talks about a time about a lost item called the Maker's Chronicle. It has long been lost and he hopes to give it back to the Makers but he needs your help to do so.  He tells you to go speak to Muria back at the Tri-Stone.
Once you get back to the Tri-Stone go talk to Muria.  There she will tell you that she doesnt know where it is but that she can give you an item that will help you locate it's where abouts. However, there is a catch.  Muria asks you to first collect for her 6 life seeds for her practices.
These items are pretty common in enemies you kill.  If you can find a large assortment of enemies.  The easiest place to get these is the Fjord or Drenchfort.  There you can find a respawning insect like enemy and hive.  By continually killing the insects and leaving the hive alone you can gather the life seeds in no time flat.
Once the seeds are gather head back to Muria and she will reward you with the Lodestone.  The Lodestone will allow you to locate the Chronicle, which if you bring up the map and set the quest to active will allow you to track it down no problem. Fast travel to Baneswood and you can locate the Chronicle there.
After locating the Chronicle take it to Oran and you will finish the quest.

Source: http://www.ign.com/wikis/darksiders-2/Makers_Chronicle

Book found inside baneswood


Congruent parts of triangles

Question: How can you show that if two sides of a triangle are not congruent, then the angles opposite those sides are not congruent, and the larger angle is opposite the larger side of the triangle. [clue: Use isosceles triangles.]
Comment: Is it a homework problem?
Answer:
Clearly, $\angle ABC>\angle ACB$
Let $D$  be a point on $AC$ such that $\angle ABD=\angle ADB$
Also let $E$ be the midpoint  of $BD$
So, in $\triangle ABE, \triangle ADE$
$(1) BE=DE,(2) AE$ is the common side and $(3) \angle ABE=\angle ADE$
So,  $\triangle ABE, \triangle ADE$ are congruent (Using $SAS$ formula)
So, $AB=AD$  and $\angle AEB=\angle AED=\frac{\angle AEB+\angle AED}2=\frac\pi2$
Using Pythagoras Theorem,  $AC^2=AE^2+EC^2,AD^2=AE^2+ED^2\implies AC^2-AD^2=EC^2-ED^2>0$
So, $AC>AD\implies AC>AB$
Comment: Great job! I draw a triangle to check your answer and it answered all what is required. =)
Comment: @caleb, hope I could make the idea clear.

Congruent parts of triangles


Jasper report JasperFillManager.fillReport very slow

Question: I am using jasperreport api-s to generate reports for my web application and i am converting the same in HTML , PDF , EXCEL and CSV formats .
I am creating it in the following way .
JasperReport jasperReport = null;
JRDesignQuery jq = new JRDesignQuery();
jq.setText("select * from employeetab"); //SQL Query might return 10-1000 or more records
jasperDesign.setQuery(jq);
jasperReport = JasperCompileManager.compileReport(jasperDesign);
JasperPrint jasperPrint = null;
jasperPrint = JasperFillManager.fillReport(jasperReport, null, dbconnection);

while executing JasperFillManager.fillReport(jasperReport, null, dbconnection) , but the server is taking too much time at times , and sometimes it does not even show up .
The issue is not very consistent .
The application is deployed in a Linux Server .
I have also tested in windows but i hardly face the above issue .
Any idea what might be the issue ??
Answer: If you are exporting to HTML, jasper can be very, very slow.  This is because the HTML it is outputting is super verbose - if your report has 1000 lines in it, it could be several megabytes in size.


Integrate Passbook App in my iPhone App

Question: In my iPhone application there is a list of gift coupons. I need to add coupons to the Passbook. How can I do this ?!
How to generate passes for each coupon?!
Is there any way to generate this pass dynamically?!
Answer: I am going to assume that by 'dynamically' you mean on-the-fly from within the app. The short answer is no.
Passes must include a signature which is a composition of a certificate provided by apple that is signed with your private key. From a security standpoint it is a terrible idea to include this information in your app, and as a result if Apple thinks you are signing passes from inside your app they will likely reject it from the app store.
This being the case, passes must be created and distributed by a server.
You should check out the Passbook Programming Guide. This is a dense document, so it might be useful to start with the Passbook Ecosystem Design

Integrate Passbook App in my iPhone App


implementation different than simulation

Question: I have to build the below series RLC circuit , and output its bode diagram using NI ELVIS Instrument Launcher. It is for a bandpass filter, so the output is taken across the resistor. Before proceeding I simulated the circuit on Multisim, and it worked perfectly, however the implementation didn't give me quite the expected results. I measured the two cut-off frequencies, and they had high percentage errors. Any reason as to why this could happen? Does the software assume certain things?
Comment: The software assumes what you put in as parameters. Did you include ESR and ESL of the capacitor? Did it include DC Resistance of the inductor? Did it include inductance of the wire loop? Did it include the output impedance of the signal source?
Comment: @Asmyldof Oh no I didn't, we never did that in our previous labs so I had no idea about such things, I thought they are negligible. Anyways it is a design lab, so maybe I need to find another combination of values that give me my required cut-off frequencies.
Comment: What means "high percentage errors" (5% or 20%)? More than that, because of the very small resistor (3.3 ohms), the bandwidth will be rather small. Did you take into account tolerances?
Comment: @LvW more like i am supposed to get lower frequency of 677Hz and upper frequency of 915Hz, but i got 549 and 1258, around 16% and 36% i guess. Yes I did, my theoretical resistor value is 3.47 ohm, simulation-wise it is still close. I tried using 1 ohm too for implementation to lower my bandwidth, but it didn't make that much of a difference. My problem statement requires me to build a bandpass series rlc filter with 677 and 915 as the cut-off frequencies, the choice of values was done by me.
Comment: The biggest difference between simulation and 'real life' components is tolerance. In simulation you can use values such as 18u6 (accuracy claimed <1%?) for the capacitor. In 'real life' this will probably be a 22uF with  +/- 20%. (Don't believe the printed value is the actual value). Its not surprising that you get such different results. Large value capacitors are to be avoided in filters due to the large tolerance .
Comment: @JImDearden I worked first with 22uF, then realized I could have 47uF, 33uF and 470uF in series, and it gives me 18.6uF, but maybe it's as you said the large values could be the problem.
Comment: You have to remember that each component has its own tolerence which means that although the nominal value was calculated at 18u6 it still has a potentially large  error in that value (in this case 15 - 22uF if 20%)  Re-run the simulation with **worst  case values** (allowing for all component tolerences) and see what the spread  of results will be.
Answer: In theory, theory and practice are the same.  In practice they're not.
A simulator will happily crunch away on unrealistic values that make real components far from ideal.  Some non-ideal characteristics may be simulated for, if you specified them and entered their values, but the real world will always be more complicated.
In your case, your impedances are very low.  Consider the current required to drive a 3.3 Ω load.  It's just numbers in a simulator that assumes V1 is a ideal voltage source, but V1 certainly isn't.  If V1 is a function generator, then it may have output impedance of 50 Ω.  That's still a lot higher than the 3.3 Ω load that will be presented to it at the center frequency.
Simulators can be useful, but there is no substitute for actually thinking about the circuit.  Use a calculator or let the simulator determine the details of the numbers, but you have to think about the broad picture first.  In this case, 3.3 Ω loading on the voltage source should have been a obvious consideration.
Make the input impedance of your filter several times the output impedance of the signal source.  If the signal source has 50 Ω output impedance, then R1 should be 500 Ω minimum.  Using common values, so 1 kΩ it is.  Now the ESR of the cap and the DC resistance of the inductor will be effectively irrelevant, which they weren't when acting against a 3.3 Ω load.  At 1 kΩ output impedance, it will also be easier to find realizable values for the inductor and capacitor.
Comment: Thank you, I will try increasing the resistance and see how it goes.
Answer: 32px - I think the problem with your circuit is the following:
At resonance frequency the total load resistance will be approximately 3.5 ohms (neglecting copper wire resistance). This will require a current of app. 0.3 A.
I think, this load will overload your signal generator.
So - why not using a parallel RLC bandpass?
If you are required to use a series RLC circuit, use a larger ohmic resistor in aacordance with the required quality factor Q=midfrequency/bandwidth=(1/R)*SQRT(L/C).
Example: R=25 ohms, C=15.4µF, L=105mH.
Comment: Yeah, I have to use series! Q=3.31, giving me R=3.29 ohm which is almost 3.3 ohm, thanks for your effort though. I will ask the lab instructor to look over my circuit again, just in case.


Why do cats suddenly run crazy at home

Question: There are two cats in my family, one is 7 years old and the other is 3 years old. They are usually very quiet at home and sleep most of the time. But sometimes, they will suddenly run around the house like crazy. Do you know why?
Comment: Do they run around playing and chasing? Or do they seem scared?
Comment: this question is most likely asked here before in some shape or form so i think it might be a duplicate.
Answer: While there are many theories on why cats make sudden movements, the one I like the most is built-up energy. A cat's anatomy is evolved for short bursts of extreme movement, followed by hours of rest. A housecat, however, does not have a predator chasing him or prey he wants to pounce. As a result, he might not have any reason to move as his wild ancestors. Therefore, one way to discharge the built-up energy is these crazy runs, without a proper reason.
Another explanation is simply being spooked. Cats do not see as well as humans in most occasions, but their hearing is impeccable. Something that you can't hear might spook them which results in these crazy runs.
Note that these theories are not necessarily disjoint. Cats might look for a reason for bursting into action and some auditory cue that we can't perceive might just trigger it. This is actually something you can experiment yourself. While we cannot control the auditory cues as we can't hear them, we can control how much energy the cat has. Tire your cats until they can't move a couple of hours before they act crazy and see for yourself if they are still running crazy.
It is also common for cats to move like crazy if their partner is moving like crazy. This kind of behaviour suits prey more than predators, i.e., a prey animal gets agitated simply because another member of his herd is agitated without knowing the reason of agitation. However, predators might act this way too. I have seen a cat getting fixated on a point on the wall urging his buddy to get fixated on the same point.
The bottom line is that it is a normal behaviour. There is no reason to be alarmed, both for your safety and for your cats' health.
I hope this helps.
Answer: only they know why. It's often referred to as "the zoomies" and most cats (especially younger ones) will do it on occasion.
Generally it's thought to be caused by excess energy, maybe in combination with them thinking they hear something that needs investigating.
More jokingly, cat owners tend to see it as proof that cats can see ghosts and chase them around the house :)
It's pretty harmless, though they can end up making a mess if they bump into something that then falls over.
My old cat was an elderly gentlecat of 12 years and generally didn't engage in it, my 2 current youngsters who are a year old do it a few times a day and then end up falling asleep shortly after, more often than not snuggling together.

Why do cats suddenly run crazy at home