How does stream entry occur?

Question: When a person becomes a stream enterer/Sotapanna, I understand they no longer have the first 3 fetters of belief in a self, doubts about the Buddha, his teachings or the noble sangha, or attachments to rites and rituals. But what's not clear to me is the mechanics of it. Does a person have a glimpse of Nibbana in a moment of true mindfulness and the three fetters drop away? Or does a person work at eradicating the first 3 fetters and if successful have a taste of Nibbana? Or can it happen either way?
Comment: This is a great question with great answers.
Answer: Stream-entry is very simple, there is nothing supernatural about it. Stream-entry is when the practitioner has fully understood the vision behind Buddha's teaching, has fully assembled the puzzle, and now has no doubts about what Buddha meant when he said certain things or why he said them. Having a clear vision of what Buddha was referring to includes clearly seeing the reality behind Three Marks of Existence and the actual mechanism behind the Four Noble Truths.
Because most of us are so dominated by our preconceptions about the world, and about Buddha-Dharma, stream-entry is difficult or virtually impossible to attain from mere theoretical study of sutras, or from one super-successful meditation session, when one gets a "glimpse of Nirvana". Instead, stream-entry requires an effort consistently applied over a long period of time, targeted at putting Sat-Dharma to practice in day-to-day life.
The reason it's called "stream"-entry, is not because one enters some magical stream, but because one finally sets foot on the unquestionably right road towards Nirvana, having really understood the whole thing.
As I understand, what he subsequently called stream-entry (attaining a clear understanding of Three Marks of Existence and Four Noble Truths -- and therefore cutting all doubts) was attained by Buddha at time of his Bodhi, but because he had already liberated his mind from most of the other asavas by then, he effectively achieved full Nirvana at once. But in case of Buddha's students (and ourselves), because we do have the advantage of teaching available to us, we can assemble the puzzle while still having residual mental/emotional obscurations. Hence the need to have a separate name for this stage, distinct from "bodhi".
As for how exactly stream-entry occurs. It occurs through exhausting samsara. In order to exhaust samsara you must exhaust ego. In order to exhaust ego you must explore all corners where Enlightenment might hide, until you know you couldn't have possibly missed it. Then it finds you :)
Comment: For both logical as well as didactic reasons I have to say, yes, it is possible to regress. Not necessarily due to discontinuing formal sitting meditation (because there are advanced practitioners whose awareness grew so much that they effectively meditate-in-action) but mostly because of careless misdirected attention, which can lead to experiences which (when applied on top of residual ignorance) can gradually accumulate as new unhealthy samskaras. Can't fall back further than srotapanna though, that's for sure.
Comment: Eating healthy, exercising regularly, sleeping well, and so on I remain fit and healthy. Sometimes my body can compensate for minor lapses, other times it is less able. Enlightenment is a living thing like my body, though relatively unaffected by old age and sickness, if abused, it also regresses. Sometimes it has the ability to bounce back from abuse, other times it needs lots of care and attention to heal back to good health. Nirvana isn't a goal to attain and rest easy, even though the first moment of attainment is special, it is a state of mind that is continuously attained.
Comment: Thanks. Very well explained. Is it possible to fall back due to discontinuing meditation? Anagami to sagdagami. Sagdagami to sotpanna and so on.
Comment: @kevin, during the 2nd council held 100 years after Buddha's Parinirvana, Sthavira (so-called elders, of which Theravada is a remote offshoot) separated from Maha-sangha (majority, which eventually developed into Mahayana). Most of the latter believed that stages up to anagami were fallible (due to residual ignorance), and some even held that arahants were fallible too (google "five points of Mahadeva"). Unfortunately most of the information about early extinct schools exist only in form of references in later texts. If you google for "arhats fallible" you should find plenty of citations.
Comment: What is made of the mind can be unmade by the mind. "Happiness and enlightenment are living things and they can grow. It is possible to feed them every day. If you don't feed your enlightenment, your enlightenment will die. If you don't feed your happiness, your happiness will die. If you don't feed your love, your love will die. If you continue to feed your anger, your hatred, your fear, they will grow. The Buddha said that nothing can survive without food. That applies to enlightenment, to happiness, to sorrow, to suffering." http://www.lionsroar.com/in-engaged-buddhism-peace-begins-with-you
Comment: @Andrei Volkov Friend, I will quote the following from you: "For both logical as well as didactic reasons I have to say, yes, it is possible to regress." Now, are you trying to say that a person can regress from one stage of enlightenment to another (e.g: Anagami back to sakadagami)? If that's the case, can you do me the great favor of providing some sources? Amplifying what you meant by that would also be appreciated. kevin. Note: I don't have a 50 reputation to comment to what you said.
Comment: For people who didn't hear/know about Budha's teachings?
Answer:
Does a person have a glimpse of Nibbana in a moment of true mindfulness and the three fetters drop away?

Yes, this is the correct explanation. The path of purification is as follows:

The meditator undertakes the practice of morality, specifically guarding the mind from unwholesomeness (sīlavisuddhi)
Guarding the mind, the meditator cultivates focus, gaining clarity of mind based on the objects of experience (cittavisuddhi)
Having a clear mind, the meditator cultivates an understanding of the nature of experience as composed of impersonal physical and mental constituents (diṭṭhivisuddhi)
Observing the physical and mental phenomena, the meditator cultivates an understanding of the causal interactions between the physical and mental phenomena (kaṅkhāvitaraṇavisuddhi)
Through the understanding of positive and negative causal relationships, the meditator cultivates an understanding of what is an what is not the path (maggāmaggañāṅadassanavisuddhi)
Through an understanding of the path, the meditator cultivates the right path (paṭipadāñāṅadassanavisuddhi)
Through cultivating the right path, one attains knowledge and vision of the noble path and fruition (ñāṅadassanavisuddhi)

Sotāpanna occurs upon attainment of the seventh stage. The right path (#6) is the gradual understanding that all formations are impermanent, suffering, and non-self. Once this realization becomes all-encompassing, the meditator attains an absolute certainty of one or another of the three characteristics and this leads to a release based either on knowledge of signlessness (based on impermanence - that there is no telling what will happen in advance), desirelessness (based on suffering - that there is no benefit to clinging to any formation), or emptiness (based on non-self - that all formations are void of self and there is no relationship of ownership or control in regards to all formations).
This release leads to an experience of cessation, where there is no arising of sense experience (including mental sense experience). This is the realization of nibbāna, and this is what leads to the eradication of the first three fetters.

Wrong view is eradicated because one can never believe that anything could be permanent, satisfying or controllable, having seen them all cease without remainder.

Attachment to wrong practice is eradicated because one can never be confused about the practice that leads to nibbāna after seeing nibbāna for oneself.

Doubt about the Buddha, Dhamma or Sangha can never arise, because one knows what the Buddha taught to be true with complete certainty, and the results that one attains having followed said teachings.

Here are some source quotes from the Visuddhimagga:

Then, while every sign and occurrence appears to him as an
impediment,when conformity knowledge's repetition has ended,
change-of-lineage knowledge arises in him, which takes as its object
the signless, non- occurrence, non-formation, cessation,
Nibbāna,—which knowledge passes out of the lineage, the category, the
plane, of the ordinary man and enters the lineage, the category, the
plane, of the Noble Ones,—which, being the first adverting, the first
concern, the first reaction, to Nibbāna as object, fulfils the state
of a condition for the path in six ways, as proximity, [673]
contiguity, repetition, decisive-support, absence, and disappearance
conditions,—which is the culminating peak of insight,—which is
irrevocable

and

The abandoning of the states beginning with the fetters by the
noblepath knowledge in such a way that they never occur again, like a
tree struck by a thunderbolt, is called abandoning by cutting off.
With reference to this it is said: "Abandoning by cutting off comes
about in one who develops the supramundane path that leads to the
destruction [of defilements]" (Paṭis I 27).
(Both from Nyanamoli's translation of Vism XXII)
Comment: Are there also relevant quotes from the suttas (rather than the commentaries)?
Answer: For stream entry to happen you have to go beyond the realm of mind and matter (Nirvana). Momentarily your faculties stop working you enter into Nirodha Samapatti / Phala Samapthi. When going in to this stake you see the links of Dependent Origination in the forward direction and when you come out of it you see it in the reverse direction. Depending on the intensity of your experience you enter into some stage of sainthood. If it the weakest it is stream entry.
Before you enter into Niroda you have to extinguish all Sankara leading you to births in the lower realm through Vipassana. Once you experience Nirvana your mind is at the sate that you cannot do any Karma giving birth in the lower realms (falling away of the 3 fetters) and you have eliminated all your store of Sankara which leads to birth in the lower reams hence you cannot be born in any of the lower realms.
(This is as per interpretation in the Ledi Sayadaw linage.)
Comment: Why the downvote? What is wrong or what needs improvement?
Comment: First paragraph:  That is exactly how the Bhante Vimalaramsi teaches it.  Plus, of course, there is the two-fold attaining: of the path and then, after that, of the fruit knowledge.
Comment: First parapgraph:  Is there an English-speaking source available, where the Venerable Ñanadhaja explains this?
Answer: I believe there are probably a few ways to enter the stream.
I have entered the stream (as a lay person)
Having no parents has really helped me to connect more deeply with the
true nature of the way things are. I have had little conditioning, no
preconceptions. As an autodidact, things have been revealed to me
intuitively over many years.
For the last 20 years I have been going on walks (walking meditation)
in the local forests asking questions. Nature has been my mother
and father, my teacher. My eye has always been open on these walks.
I realized that whatever arises would cease and it was heartwarming.
For me, being a stream winner is like this: When you have to overcome
extreme trauma and appalling loss and you don't become cruel and
you can forgive and you can let it go, you stop the cycle.
You have done what you came here for and you transform.
That and  maybe 20 years of walking in woods...lol. I doubt I could
do another 20! Be Well.
Answer: Factors for Stream Entry.

Then the Venerable Sāriputta approached the Blessed One, paid homage
to him, and sat down to one side. The Blessed One then said to him:
"Sāriputta, this is said: 'A factor for stream entry, a factor for
stream-entry.' What now, Sāriputta, is a factor for stream-entry?" (1)
'Association with superior persons, venerable sir, is a factor for
stream-entry. (2) Hearing the true Dhamma is a factor for
stream-entry. (3) Careful attention is a factor for stream entry. (4)
Practice in accordance with the Dhamma is a factor for stream-entry.'
"Good, good, Sāriputta! Association with superior persons, Sāriputta,
is a factor for stream-entry. Hearing the true Dhamma is a factor for
stream-entry. Careful attention is a factor for stream-entry. Practice
in accordance with the Dhamma is a factor for stream entry." - SN 55.5

Here is a book free for downloading (no breaking 2nd precept here :-)
http://watnapahpong.com/static_media/Sotapanna_Handbook_English_version_30.pdf
Buddha gave 50+ definitions (40+ in this book) of what stream enterer is and what not.  Also how to get there.   one thing certain, buddha allowed only him and yourself to predict if you have reached the state.
and as for Nirvana, nibbana.  it is not a place where 5 skandha is ..
vijñāna (consciousness) since it is not permanent (dukkha) ,thus, cannot take root or manifest  in Nirvana.  the 3rd of 4 noble truths does not describe nirvana but cessation of desires.   That is something  vijñāna (conscious) can take place.
Answer: With great respect, if stream entry is sought for, I can recommend 'Liberation Unleashed'.
This is a group run entirely free and by volunteers (of which I am one) who have also realised the emptiness of self, and are willing to guide others to the same realisation. Simply request a guide in the forum - Alternatively, visit us on Facebook and request a guide there.
http://www.liberationunleashed.com
Comment: This answer reads like an advertisement.
Comment: Welcome! I hope you might add something to answer the specific [question-as-asked](http://buddhism.stackexchange.com/q/216/254) which was something like, "Is stream entry sudden, or is it gradual?" or maybe it was about what is cause versus what is effect: "Do the fetters drop because of glimpse, or is the glimpse because of fetters dropping?" Perhaps you can [edit your answer](http://buddhism.stackexchange.com/posts/9592/edit), either to include some extra information directly, or to identify any specific page/text within the web site you referenced, which might help to answer this question.
Comment: Hello and welcome to Buddhism.SE! We've put together some information to help you here started [here](http://meta.buddhism.stackexchange.com/questions/1502/i-am-a-new-user-here-at-buddhism-se-what-should-i-know-before-i-post?).
Comment: @ruben2020  Well technically it is an advertisement, but the product is great, and absolutely free. I have worked with two guides from LU and both were extremely patient, helpful and knowledgeable.
Answer:
Does a person have a glimpse of Nibbana in a moment of true mindfulness and the three fetters drop away?

Yes. In a moment of true mindfulness and equanimity, nibbana can happen and when it does, the fetters drop away. That is why attainment of path is referred to as "clear knowing and release" in the suttas.

Or does a person work at eradicating the first 3 fetters and if successful have a taste of Nibbana? Or can it happen either way?

No, Nibbana happens first and that results in eradication of fetters. The behavioral changes might take a while to come into effect though, after the review cycles. Post stream entry, mind starts cycling through various insight stages, which result in changes in external behaviour.
Answer: First of all one becomes faith-follower by gaining conviction in regards the nature of these phenomena;

feelings
forms
perception
knowing
intentions

as;

not belonging to a self
not constituting a self
not being apart from a self
not being in a self

This is called safeguarding the truth having placed conviction, one does not yet come to a definite conclusion.
Further having pondered the nature of these phenomena as such one comes to a point where the nature of these phenomena has been penetrated by modicum discernment.
This stage is called Dhamma-Follower, the second type of a Noble Disciple, also he safeguards the truth.
As i understand it, in the Theravada Tradition the two type of Followers are thus classified as people working towards the realization of the first fruition and would be included in the 1st category in the 8 fold delineation of the 4 pairs of Noble Disciples, namely;

One working towards realization of the 1st path fruition
... of the 2nd path fruition
... of the 3nd path fruition
... of the 4th path fruition
One who has realized the 1st path fruition
...the 2nd path fruition
...the 3rd path fruition
...the 4th path fruition

The followers are however not included in the 5-fold classification of Noble Disciples, namely;

One attained to view
One liberated by faith
One liberated by wisdom
One liberated in both ways
A bodily witness

Therefore i assume that the list of 5 refers to types who have transcended the stage of Safeguarding the Truth because the one attained to view has seen with discernment and cut the three fetters and the other types are Arahants.
Therefore to transcend the stage of safeguarding the truth one needs to go beyond pondering and "see with discernment" as to come to know and see that the phenomena (feelings etc) are actually that way and only that is true and everything else is false;

the Dhamma being taught is deep, hard to see, hard to realize, tranquil,
refined, beyond the scope of conjecture, subtle, to-be-experienced by
the wise.
Exerting himself, he both realizes the ultimate meaning of the truth
with his body and sees by penetrating it with discernment.
"To this extent, there is an awakening to the truth.

This implies a direct experience of discerning the escape from the made;

There is, monks, an unborn — unbecome — unmade — unfabricated. If there were not that unborn — unbecome — unmade — unfabricated, there would not be the case that escape from the born — become — made — fabricated would be discerned. But precisely because there is an unborn — unbecome — unmade — unfabricated, escape from the born — become — made — fabricated is discerned. - Ud 8.3

After this "experience" one is a stream-enterer and has transcended the stage of safeguarding the truth and is one awakened to the truth.
What remains is further development of those same qualities for the final attainment of the truth and becoming one of the Arahants in the 5-fold classification of Noble Disciples.
Answer: Once one attain the enlightenment as stream entry, all four Noble Truths perceived at the same time eradicating the first three fetters. As a bhikkhu(not necessarily a monk), afraid of Sansara, working hard on meditation achieving sixteen stages of wisdom , come to reach the Phala and clearly know what is Nibbana  with Magga nana getting rid of all doubts on Buddha teachings. Out of sixteen stages of wisdom, even at fourth stage one can have clear view  of non-self, no wonder stream-entry have no single grain of the three fetters left. But how this detail is so subtle that if you wish to know , as one of Dhamma Characteristics, ready to take on, come and try to achieve it.
Answer: One of the strongest delusions we live with is the Self. We can't even begin to imagine being without it, and we even imagine it's somehow eternal and or immortal. But like everything else, it's impermanent, it's not a thing in and of itself (it's made up entirely of non-self elements), trusting in this delusion causes suffering, and breaking the delusion brings freedom. This is why we practice the way we do. When we experience seclusion, quiet, and calm, the obscuring and clouding effects of thoughts and experiences settle down. We return to who we essentially are, impermanent and self-less. Stream Entry is basically just returning from meditation to the every-day world and not losing the direct experience of that. Seeing the world in this way is why we become convinced. The mechanism is practical and makes plenty of sense. Of course this is an important first step, as old habits and lifestyles are still going to be in the way. Really not having any inclination towards the "delights" of samsara is much better.

"Sariputta, 'The stream, the stream': thus it is said. And what,
Sariputta, is the stream?"
"This noble eightfold path, lord, is the stream: right view, right
resolve, right speech, right action, right livelihood, right effort,
right mindfulness, right concentration."
"Very good, Sariputta! Very good! This noble eightfold path — right
view, right resolve, right speech, right action, right livelihood,
right effort, right mindfulness, right concentration — is the stream."
— SN 55.5
Answer: I experienced what I would call stream entry without knowing anything about Buddhism other than a typical, ignorant, western perspective.
I was meditating and in my minds eye I saw a radiant white pearl with smaller discolored pearls floating around it (in many ways like a solar system). As I began to investigate the discolored pearls, I realized they were my wants and desires. I realized, "these are not me"; they began to fall away until all that was left was the white pearl. In that moment I realized that the "white pearl" is within us all.
Next I experienced a feeling of death overwhelming me. I knew I was dying; it was the most fear filled experience I have ever had. Then I felt reborn. In that moment I was only a body and a stream of consciousness. After that, all that was left was a feeling of love.
I can not say from experience but I believe that the same insight could come from persistent determination to remove the three fetters.
To clarify, this can be seen as reverting the 12 link chain, experiencing cessation and then being reborn
Comment: i'm no expert, but wouldn't the fact that this experience involved specific perceptions and feelings—make the experience not a glimpse of nibbana, and therefore stream entry did not occur?
Comment: @qweilun These are the moments immediately proceeding stream entry and the effects after stream entry. The moment between death and rebirth was nirvana.
Answer: For me it was an instant. A moment of realization: that I "am" Nothing. As I looked at each layer that I thought was "me" I recognized that "this is not me". After peeling back every layer I realized there was nothing left, yet I was still here. How could that be? THat must mean I am "this". And it was in that instant that I realized my true nature. It didn't have any "mechanics" to it. It was just a realization. The only mechanics, if you could call it that was an intense desire to know what I am and doing everything possible to find that.

How does stream entry occur?


Nextcloud integration

Question: I just read the September updates blog post and updated via App Center. I don't see anything added to Online Accounts; so, I'm assuming I still connect to the Nextcloud server through Files>Connect to server. When I do that, I still get the same behavior as I previously would which was, after entering the information, the configuration screen comes back and nothing connects.
Answer: While nothing to offer in regards to the libcloudproviders update to files (because it makes no difference here, on my system, at all)
It sounds like you would like to connect to nextcloud via Webdav. Let me help you do that.
Open files, and click -> Connect to Server
choose whichever fits (Https if you have set up nextcloud with SSL or HTTP if not)
in the serverfield input: url or ip address as appropriate. no protocol spec. e.g.:
nextcloud.yourdomain.com

or
 192.168.0.20

etc.
then under dir/folder, input:
/remote.php/webdav/

then input your username/password. If you set it up with a selfsigned certificate, you will be prompted to accept an untrusted certificate. Then it should be connected. but please notice: This webdav connection will not be seen by files as anything related to nextcloud, as that is abstracted away when using something like webdav (and that is really what such protocols are for)
Answer: You can create the folder /usr/share/cloud-providers, and then put the file com.nextcloudgmbh.Nextcloud.ini there. You can get the file from the Archlinux package here:
https://www.archlinux.org/packages/community/x86_64/nextcloud-client/
You will also need the Nextcloud desktop client installed, which you can install from the Nextcloud ppa. Configure and set the Nextcloud client to start at login. Log out and login again, and you should see the Nextcloud option in Files.
Comment: Information about NextCloud integration in Files can also be found here https://linux.marco.betschart.name/elementary-OS/Nextcloud-Client.html
Answer: in addition to rasmus91 solution

works fine on eOS 5.1.7 Hera and Nextcloud 20.0.1

if NC is installed on a path like: yourdomain.com/nextcloud

add the path before remote.php nextcloud/remote.php/webdav/

I needed to figure that out for 10min..

Nextcloud integration


Does easy credit in a region cause property to be more expensive?

Question: Does easy credit (e.g. lower minimum down payment, lower interest rate) cause housing prices (purchase, rent) in that area to be more expensive? Intuitively, this seems to be the case, because the availability of credit means more people can be a potential buyer, which drives up demands, which should increase price. Has there been an empirical research that backed this up or refuted it?
Comment: Empirical or theoretical research? Or both?
Comment: If one believes the effect is symmetric to some degree, you can also look for evidence for the other direction: does tightening credit cause declines in housing prices.
Comment: I prefer empirical (edited the question)
Comment: Not quite what you asked, but anyway: the book "The greatest trade ever" explains how John Paulson predicted the credit crunch. They drew a graph of house prices adjusted for inflation, saw a sharp upswing around 2000, and realised this coincided with loosened lending requirements.
Answer: Theoretically, multiperiod borrow and lend models I am familiar with suggest that an increase in ease of credit (increasing the credit supply) should increase demand. This in turn raises the price of housing. So I believe your intuition here is correct.
Empirically, I am only familiar with one paper analyzing this relationship, which finds the same thing.

...because of geographic diversification, treated banks expand credit: Housing demand increases, house prices rise, but to a lesser extent in areas with elastic housing supply, where the housing stock increases instead.

Credit Supply and the Price of Housing
Favara and Imbs (2014)
http://www.jeanimbs.com/papers2_files/Favara_Imbs_May2014.pdf
Comment: (+1). The excerpt says it essentially all: it pushes prices up but also supply of houses, if this is feasible in the area. But building and offering new houses takes more time than offering increased credit, so we expect a net rise in house prices at least in the short term.


Need help for ice maker line splitter to be used for coffee maker

Question: We have a coffee maker that keeps needing to be refilled. I had an idea to split of the ice maker line (which is easy) to supply the coffee maker. The only issue is, is there any attachment that with a press of a knob or nozzle water can be dispersed?  This would have to fit the regular sized ice maker lines. Thx.
Comment: Have you considered a coffee maker that can hookup to a waterline and automatically fill?
Comment: I'm happy with my Keuring :)
Answer: The problem with your idea is the risk of damage of the line and associated leakage.
While ice makers use thin copper or plastic lines, they are permanently attached and not handled once installed. The valve that controls the filling is built into the ice maker, and is automatic.
A similar approach to your coffee maker would require that you have a fixed mounting for the valve that is substantial and protects the line and attachment from rough handling. There are such systems used as pot fillers, like this one

These are permanently mounted on a wall very close to the point you fill pots, such as a stove.  The risk is spilling water in an area with no drain. These units are usually installed with standard plumbing (copper, pex, etc.), not lightweight tubing, although adapters probably could be used to accommodate small tubing.
While there are small plastic valves that are used on things like water jugs, these are also intended for fixed mounts of the valve.
Answer: You can add a typically kitchen side sprayer (probably has some actual product name too)

It will not have the same connection as your ice maker line but you can buy adapters. If you have a flexible line (or T off to a flexible line) you can probably cut the end of off the sprayer line and get one barbed connector as your adapter.


Firefox/Opera password manager

Question: On Windows machines, Firefox and Opera both will fill in and save passwords in the password manager.  Why does it not function the same way in Ubuntu?
Comment: Can you explain what do you mean by Password Manager?
Answer: Also in Ubuntu, Firefox will auto-complete usernames and passwords, unless you except a specific web page. Opera does not do so, but it has a key-shaped button beside the web badge (or a shortcut-key Ctrl+Enter) to login automatically.

Opera, unlike Firefox or Chrome, won't show saved passwords in Password Manager – I like this security guard.

Firefox/Opera password manager


Multiply clock frequency by three or more times?

Question: Frequency of a digital clock signal can be doubled by using an EXOR gate (clock at one input pin and delayed clock at another).
Can we use any similar circuit which can multiply frequency by three times ?
Comment: Usually on a VCO (NE565) the multiplication of frequency obtaneid by a divider inserted between VCO output and the phase comparator. So to get fout=3x, a divide by 3 network needed (7490 4-bit binary counter).
Answer: You can use a third harmonic filter (inductor and capacitor) to resonate at clk*3 and then a schmitt trigger inverter (or other gate) to turn the sine wave into a decent square wave at clk*3.
This works because a typical square wave has fundamental and odd harmonics in its spectrum: -

The blue waveform is the output from the tuned circuit when excited by a 1 MHz square wave. This can be magnified to logic levels with a comparator with a little bit of hysteresis.

Can we use any similar circuit which can multiply frequency by three
  times ?

I cannot tell you to believe it's similar but in my mind it is.
Answer: The most common way it to use a PLL based frequency multiplier.

Source (www.ee.ucl.ac.uk/~pbrennan/E771/PLL.ppt)
The Phase Locked Loop works for frequency of a signal (or more correctly -phase), like an op-amp works for Voltage. It has a high enough gain to keep the two inputs of the phase detector equal in frequency (and usually phase).
Applying a reference signal to the input,  the other phase detector frequency becomes equal to the reference by virtue of the loop gain changing the frequency of the Voltage Controlled Oscillator (VCO) until the frequency error is zero and therefore the output frequency is Finput * N.
I've taken some liberties with the details like lock range, loop bandwidth etc.. but I hope you get the idea.
You may find it interesting that an XOR gate can be used as the phase detector in a Digital PLL frequency Multiplier:
Answer: If one wants a clean 3x waveform with uniformly-spaced rising edges and a known timing relationship to the original, a PLL is the best way to go.
If one wants something with 3x as many rising edges as the original waveform, but doesn't particularly care how even they are, a simple approach is to use an oscillator that runs at least 6x the speed of the reference along with a counting circuit.  As a possible implementation, have the 3x clock operate a three-bit counter a flop which captures the state of the reference, and a flop which captures the state of that flop.  Have the counter jump to 000 any time the latter two flops read "01", and otherwise advance once per count whenever its value isn't 101.  The LSB of that counter will pulse three times for each reference clock edge, provided that the input clock is fast enough for it to do so.


Concentration meditation vs awareness meditation

Question: Which meditation is better to do: Awareness meditation(such as:Vipasana) or concentration meditation (such as:
Tratak)?
Comment: Hatha yoga focuses on Trataka Meditation. Buddhism focuses on Vipassana Meditation...
Comment: I am not aware of what the roots of 'awareness' meditation are. it seems to be to use meditation to heighten sensual awareness - not a type of Hindu or Buddhist meditation technique. My understanding of Vipassana is that it is the same as concentration meditation. The goal of meditation is freedom FROM the senses; not freedom of the senses.
Answer: Vipassana meditation is basically used not to concentrate or focus you just sit and observe you sensation.
yes when you are sitting and you feel hot, cold, itch, pain, thoughts, anger, hatred, breathing everything inside your body sensation.
So what happens is sometimes you feel very good and enjoy meditation there comes the problem you are supposed to observe this enjoyment as well, i mean do not just get flown away by good or bad feelings.
You should do this in group sitting, that may give you more confidence.
See there are 108 ways of meditation given by Lord Shiva, you can pick any of them all leads to the same place, as Swami Vishwananda said in comments "The goal of meditation is freedom FROM the senses; not freedom of the senses"
I would suggest you can try different meditation techniques from different gurus and pick one which makes you more confident but remember in all meditation you are not supposed to get attach to a feeling just sit observe and get up, because you may get stuck at a point for your entire life.
So in essence of this answer if it does not matter which one you pick, it is just that how bad you want it, also how you eat is also very important in Yoga.


CH and wellfounded models of ZFC containing all reals

Question: Is it known whether there is a wellfounded model of ZFC, containing all reals, in which CH fails? In which it obtains?
Answer: Cole:
Suppose first that $V=L$. Then certainly there is no well founded model as you want, because any well-founded model $M$ is correct about $L$, meaning $L^M=L_{ORD^M}$, and if $M$ contains all the reals, then this model must contain $L_{\omega_1}$ and must therefore satisfy CH.
(The assumption of $V=L$ is certainly an overkill here, one can easily produce by forcing many other examples of models where CH holds and no well-founded model with all the reals will satisfy not-CH. In fact, much more is true. For example, Jensen's remarkable "coding the universe" theorem shows that using class forcing techniques, there is an extension of the universe that has the form $L[r]$ for some real $r$; but in $L[r]$ we have CH for the same reason that we have it in $L$. Now, note that no inner model with all the reals can satisfy not-CH, since of course any such model contains $r$ and so is correct about $L[r]$, so the argument from the previous paragraph applies.)
However, the technique of forcing gives us that it is also consistent that there is a model as you ask. For CH could fail, but one can always force to add CH without adding any reals (simply add generically an enumeration of the reals in type $\omega_1$ using as conditions initial countable initial segments of the enumeration). This is actually a useful thing to know. It gives us that, as long as we are only interested in first-order statements about the reals, assuming CH is harmless: Any first order statement about the reals that holds under CH is in fact true. This is used sometimes in descriptive set theory, since amenability of groups is particularly nice in the presence of CH.
This shows that the answer to your question is independent of the usual axioms of set theory. (Of course, the answer is yes if we assume not-CH to begin with.)
Let me close with the comment that, if you are willing to forgo the axiom of choice, there are interesting ways in which you can have such models. For example, assuming enough large cardinals, then the inner model $L({\mathbb R})$ (the smallest transitive model of ZF that contains all the ordinals and all the reals) is an example of a model where CH fails in one sense (there is a surjection from ${\mathbb R}$ onto $\omega_2$, for example), independently of whether CH fails or holds in the universe. Note this is now a theorem, not just a consistency result. The situation is in fact a bit stranger, because in $L({\mathbb R})$, CH holds in another sense (every subset of ${\mathbb R}$ is either countable or has the same size as ${\mathbb R}$).
Comment: Haha, 51 seconds!
Comment: Hehe. I had seen this happen to other people, but I think it is the first time I'm involved.
Comment: Well, I was pausing over the part I got wrong, so perhaps I should have taken longer. :-)
Answer: Assuming the existence of suitable large cardinals, the Axiom of Determinacy holds in $L(\mathbb R)$, which implies or does not imply CH depending on what you take CH to be:
If you take CH to be the statement that no set of reals has cardinality between countable and the cardinality of the reals, then yes, CH does hold in this model.
However, if you take it to mean that $2^{\aleph_0}$=$\aleph_1$(in the sense of bijections), then no, CH does not hold. Assuming AD, there is no injection from $\omega_1$ to $2^{\aleph_0}$. If there were, you could build all sorts of pathological sets which AD does not allow(for example, an uncountable set which is not perfect).
I'm a little hazy about what follows:
Also, assuming $V=L$, then $L$ contains(?) all the reals, and CH also holds in it.
In any case, CH or not CH can be forced from any given model, so I would guess that from any model containing all the reals you can go to one where CH or not CH holds by doing the right sort of forcing. I also can't see why these forcing extensions would not have all the reals given that they are forcing extensions of models which did.
$\text{Edit}$: As Andres mentions in the comment, the above paragraph is not correct. Andres' answer explains how much of it can be fixed.
Anyhow, given the experts here, I'm sure you'll get a better, more detailed answer with fewer disclaimers.
Comment: Tanmay: If CH holds, you cannot go by forcing to a model where it fails, unless you add reals. (Of course, if CH fails, there is no need to do anything.) And it is independent that CH holds and there is an inner model of choice where CH fails. (I address this issue in my answer.)
Comment: Deleted that comment. It didn't make any sense. I seem to be a little sleepy on top of every thing else! Again, nice answer.


Should I learn Hangul as soon as I start learning Korean?

Question: I'm learning Korean but Hangul looks hard. Is it really important, or can I get by with studying only Romanizations of words until I feel more confident?
Comment: I know that beta needs questions,but come on, how can you learn a language without the alphabet it is based on?
Comment: @Mihai I have many friends who know a lot better Korean than I do, and learned it exclusively from watching K Drama. They cannot read or write, but they have a huge vocabulary and pretty decent grammar. I, on the other hand, have been taking classes, and am not good at Korean vocab and grammar at all, but I can read/write perfectly.
Comment: I was a bit sorry to see that this has already been closed - seems very much on-topic and possible to answer in an evidence-based way.
Comment: Too opiniated, but not a stupid question, I'd say. Some people only wish to learn to listen/speak, while others want to read/write. That said, language users tend to use references to the writing system in spoken language all the time. Perhaps one or more slightly reworded/refined questions?
Comment: @topomorto It's also an *extremely* common question I hear from people who are starting to learn the language.
Comment: http://meta.korean.stackexchange.com/a/12/64 might or might not be a point for discussion. Note that you can vote to reopen, though we don't want silly voting wars!
Comment: Though it is opinion-based, there are clear situations (from experienced speakers, or from language learning point of view) where one of the two possible opinions largely dominates. Being able to read hangul when you   live in Korea makes things drastically easier.
Comment: In the answers I have read over quickly, one thing is missing in my humble opinion: Does the person asking the question have English as mother tongue. I am from the Netherlands and I find Romanization exasperating because English does not use the latin letters the way Dutch does. So reading Korean in romanization forces me to read 'back to English'. For example if I would pronounce jeo 'in Dutch' I would say 얘요 not 저.
Comment: Asking this question for the sake of having it here. But with that said, would this be the kind of question that should be closed as "opinion-based"? Or is it possible to have a satisfactorily correct answer?
Comment: I think this is way too simple/obvious of a question.
Comment: It might be better to ask, "what are the advantages of learning Hangul when learning Korean?"
Answer: My experience is that learning to read Korean is easier than learning to read English. You will be severely limited in what you can learn if you never learn Hangul.
Picture trying to learn English using only Hangul. That would be rather tough. And you would tend to learn things such as pronunciation quite inaccurately.
Reading romanized Korean correctly is much harder than learning to just read Hangul. And moreover, learning to read romanized Korean correctly would in essence entail learning the sound of every letter of Hagul anyway.
Comment: I totally agree with this answer. I'd say I learned 80% of Hangul *on a flight to Korea* (10 hour flight). Learning the remaining 20% took a bit more time because there are some subtleties and rules with exceptions and exceptions to the exceptions. But it's really not that hard to get started!
Comment: I also like to point that there's no really well established standard of romanized Korean representation. Even government official standard has been changed multiple times over decades, and still can be changed again eventually. Even Koreans are confused, and I really can't recommend learning with it.
Comment: I'm studying Hangul for its own sake; I don't have a need to speak Korean just yet. Hangul is widely considered the most ideal writing system worldwide because of its ability to reproduce any sound from any language. It is also one of the most modern writing systems, though hundreds of years older than the first artificial languages.
As other users have suggested, you can learn vocabulary by ear while simultaneously studying the alphabet, though both Duolingo and Memrise start with the characters. Japanese schools also start with or require prior knowledge of the phonetic alphabets.
Answer: Learning Hangul is the absolute easiest thing about learning Korean.
I learned in a couple of hours in a cafe in Guatemala with a Korean backpacker girl over a decade ago and never forgot it.
Pronunciation, vocabulary, and grammar are all way harder for me. I can read signs and often menus but I can't have a rudimentary conversation.
(Well I don't know all the words I can read - a bit like reading French or Turkish perhaps.)
Answer: Yes, learning Hangul is one of the first things that a student of Korean should do. There are many aspects of the language that are closely tied to a word's spelling in Hangul that may be unintuitive or impossible to carry over to romanized Korean. Among the things that get lost in translation when not using Hangul are...

Pronunciation.

Korean pronunciation is practically impossible to correctly show in any romanization system without assigning arbitrary pronunciations to letters.

Meaning and Etymology

The meanings of many words are often clarified by their spellings in Hangul, which is very difficult to carry over to Romanized Korean.

Additionally, Hangul is relatively easy to learn when compared to many other Asian writing systems like Kanji. It has 24 letters which are arranged into single-syllable blocks and takes only a few hours or days to get a basic ability to read and write.
Answer: If you want to know and understand Korean, you need to learn the Korean writing system.
There are a few important reasons.

The Korean language uses a syllable-block system with several pronunciation rules based on the placement of a particular sound in the syllable block and how different syllable blocks interact. This is quite easy to understand in Hangeul, but would seem like total nonsense if you use a Romanized characters.
There are also a lot of grammar/conjugation rules which are dependent on character placement in the syllable block. Same as with 1., if you aren't looking at the syllable block, it is much harder to make sense of and recognize the use of these rules.
Material - There is very little material for studying Korean in romanized characters. You would be hard pressed to consistently find study material in a romanized format.
Romanized Korean is hard! There have been two major romanization formats and the difference in sounds between English and Korean lead to sometimes bizarre or complex English compounds that can be hard to understand.
Learning Hangul is easy! If you're worried, don't be! Hangul looks overwhelming from the outside, but once you figure out how the system works (which is quite simple) and how few characters their actually are (Only around 30ish(!), off the top of my head), you realize it only takes an our or two of study to know it all, and a few days of practice to grind it in.

Minimal effort, huge reward!  There's really no excuse not to!
Answer: Hangul is not really that hard to be honest. You could, for example, use flashcards to remember all Hangul letters and repeated writing of Hangul will also help you to remember them.
I would say that it is imperative to learn Hangul before you start learning Korean grammar or words.
Another good way to learn Hangul fast is this game here: http://dandani.eu/language/learn_korean_hangul_game
an
It's simple and easy to use and I learned Hangul very fast with it, it shouldn't take more than an hour for you to remember all letters.
Answer: Learn Hangul first. It is super easy. So easy, in fact, that sometimes I use Hangul
to write English when I am taking a course having nothing to do with Korean.
You can learn it in a day or 2. If you are not visually inclined, it may take a week.
The other reason you should learn it first is that there are different Romanisation systems which could cause you some confusion when attempting to pronounce the Korean
word.
Answer: After reading all the comments, I don't disagree because I myself am trying to learn Korean and I've been having a slightly difficult time. Though, I just wanted to ask, since Korean words are different as English (ex. Noona - Sister) wouldn't it be more helpful if you learnt vocabulary first, Then Hangul? Or I mean both since you're learning the word and the writing. I mean, I've started to learn Hangeul, but that question just popped in since I've been learning some conversation passages in the book that I study with and I don't understand it at all even if I can read and pronounce it.
Comment: Hi Yoyo - as this is more of a question than an answer (and I think it's slightly different to the original question asked here), would you mind re-posting it as a new question? http://korean.stackexchange.com/questions/ask
Comment: may be this can be changed to a comment


MOO FAQ component in joomla is not working

Question: we have purchased the "moo faq" component..  but it is not working form our side...  we have installed the component as the component package consists of the plugins and the module...  we have made a section and under that section we have made a category..  under that same section and the category we have made an article but the content of the article is not showing..  we have made a menu and linked it to the category...  the front-end link is only showing the "expand" and "Collapse" link but not showing the content of the article..  this is the link where you can see the problem "http://www.musiclibrary.fi/en/for-now/faqtest"..    you can see this link under the "For now" link in the menu which will come after logged in...  the login details is UN==samitbose PW==samitbose2011 .. we are using joomla version 1.5.23 and MooFaq version is 188.8.131.52...  Please have a look on this point ..  any help will be greatly appreciated..  thanks in advance...
Answer: Looks like you are still struggling with this.
If so, I'd check the following:
The FAQ category is published
The FAQ question itself is published
The menu links to the same category that contains the question
The category/question are no set to 'special' access level
My initial thought on reading the question was that this would be a clash with Mootools/jQuery or perhaps Mootools in the component and the Mootools upgrade plugin. I don't see anything in the page to point to this though.
If none of the above points you in the right direction - chase the developers, especially as this is a paid extension.


Can I upgrade the carrier settings without the original SIM?

Question: I have an iPhone 4 that I got from my uncle (it's a little used), but I don't have the original SIM that came with that iPhone, and I want to unlock it, can I ask the old carrier to unlock it with only the IMEI and others information that do not depend on the SIM card? Will it be able to receive a carrier settings update on iTunes?
Comment: Since you said you had to take it to the carrier, please post that as an answer. The question can still stand. Thanks.
Answer: Yes. Carrier settings are sent when you connect to their respective cellular service. So if you purchased an unlocked iPhone 4 from Apple, and inserted a SIM from AT&T, you would be pushed the latest carrier update. If the next day, you removed the AT&T SIM and inserted one from Bell Mobility, then you would be pushed a carrier update for that respective carrier.
The updates are based on your iOS version number and the wireless network you are connected to (of course you need the respective SIM as well). You won't receive updates should you remove the SIM (or fail to insert one), but then it becomes a moot point because you need the card to connect to a network, making a carrier update rather pointless to begin with.
When the original carrier unlocks the device, it will be able to handle any wireless network. And the new carrier you sign with, will issue you a SIM.
Comment: My situation is the following: I asked my old carrier to unlock my iPhone, I couldn't give them a phone number, I'm not sure if they can do that with only the IMEI number, instead of the original SIM, can I connect one from the same carrier and get the unlock via iTunes?
Comment: The unlock is provided by the carrier. iTunes has nothing to do with it. You'll have to call the carrier the phone was originally locked to a speak with a customer service representative. State your situation and hopefully they can unlock the device based on the UDID (Unique Device Identifier).
Comment: But as far as I know the unlock is delivered via iTunes, well, I'll talk to them, thanks anyway.
Comment: Where did you hear the unlock was sent through iTunes?
Comment: I live in Brazil, at least here it's delivered using iTunes, my dad's unlock was sent through it. Also, I found this on Google: http://gigaom.com/apple/apples-official-iphone-3g-unlock/
Answer: I had to take it to the carrier, they didn't tell me if I could do this without them. That's all I know :(
Answer: Been having the same problem for 4 months. I backed up and restored and it still didn't worked. I was pretty bummed out..and I really didn't want to go to a repair shop for phones cause they cost a tonnnn! So I just randomly thought that maybe something sticky got inside the button and used a pair of eyebrow tweezers (the pointy ones like this one: http://ecx.images-amazon.com/images/I/31xBWTSHbiL.jpg)
and I basically just stuck it around the button maybe 3 or 4 times really well and TADA! I DON'T HAVE THE ISSUE ANYMORE!!! I'm so happy I saved money by not getting it repaired :'D


Different heads on Dodge Magnum 360

Question: I'm working on a 98 Dodge Ram 2500 with a Magnum 360 V8 (roller cam shaft). It had a cracked head on one side, so I purchased a pair of remanned heads from an eBay retailer. These heads are the 466/671 combination (as expected). The problem is, the heads which I pulled off are an identical set (both 466 heads - this engine has had head work done before, obviously). I need to know which one goes on which side (driver's/passenger). I read on a couple of different sites which say they are identical, which I am doubting. The reason I am doubting is due to the fact everywhere I've looked, it specifies for different heads. (If they are exactly the same, or interchangeable, why would they make and specify two different heads??). I've seen one site (actually a seller) which actually specifies which head is supposed to go on which side, but it uses right/left. I have a major problem with this, as some people view right/left while standing in front of the car, while others use the view as sitting in the vehicle. Driver side and passenger side are much more descriptive. Also, if anyone knows what exactly the differences are, it would be appreciated.
Answer: After an exhaustive search on the internet, I came to the conclusion that while the two heads have a different part number and are different in some very minor ways, I have just thrown the heads on there and done the deed. If there is a significant difference I couldn't see, there doesn't seem to be an issue with them. The truck started right up without any leaks or problems with the heads that I can tell. It is my understanding (now) that it doesn't matter which head goes on which side.
Comment: @kmarsh - Same heads, just two less combustion chambers. The V10 Magnum, same-same, just two more.
Comment: Did you have a chance to check the deck for flatness? If you crack another head, be sure and do this before putting on more heads.
Comment: @kmarsh - I was working on a truck for someone else. The problem turned out to be there was a clogged cat. The owner just continued to push the truck with it that way. These heads are known to have a weak spot between the valves  in the combustion chamber (I believe on the last chamber - either cyl 1 or 7 depending on which bank it's on). That's where it cracked, but it was mainly due to poor ownership. Put the heads/cat on and it ran just fine, no worries. No problems with the deck, but point well taken.
Comment: Thanks for the follow-up. Yes, the 3.9L Magnum V6 has the same head crack issue, between the valves.
Answer: The heads are the same, left or right
When it is stated left on the vehicle it means that when you are sitting in the driver's seat, not when looking at the vehicle from the front.

Different heads on Dodge Magnum 360


What is the liquid that forms after chicken goes through the freeze-thaw cycle, and how can I extract it more efficiently?

Question: When I vacuum seal chicken pieces, freeze them, and then thaw them again, there is always a small amount of liquid in the bag after the thaw. When this liquid hits hot oil, it forms a crispy, airy puff that is absolutely delicious. I'm trying to figure out what the liquid is, and how I can extract more of it, so that I can make crispy fried chicken liquid for garnishes.
Comment: Are these chicken pieces brined/salted?  My best guess is it's chicken juices with residual proteins. Since you say it tastes delicious, I'm wondering if there's salt in there that makes it so
Comment: I added salt, and there may be some brine in them from processing. I think you must be right that there are residual proteins, or else it wouldn't fry into anything solid.
Answer: When you freeze meat the water in the cells crystallizes into ice, and in some case ruptures the cell walls. When you thaw the chicken again, the contents of the ruptured cells' are free. These are mostly the water, and the cells proteins.
Additionally, processed meats often have some water and additives added to the at the factory.
The "juice" you are seeing is probably a combination of these things.
Comment: So the only way that I can extract more of the liquid would be to freeze-thaw it a few times? Or maybe if I flattened it with a mallet first to expose more surface area?
Comment: @josh you may not want to do that. If it works, it'll ruin the texture of the chicken. If it doesn't, you're just wasting time and energy.


Equiprobable model for Pearson's goodness-of-fit method.

Question: There is a very long introduction to this problem. I can provide this if needed but for now I will stick with the actual question.
"A question of interest to the researchers was whether there were any "nonrandom features" about the location of the 296 sites of potential importance for reproduction of a certain genome. Strands of the DNA have almost 230 thousand bases. One way to study this question is to divide the locations into 20 ranges, to count the number of potential important sites in each range, and to determine if the counts are consistent with an equiprobable model "
(A table is then given that describes the 20 location groups and number of sites associated with each. The first, for example, is location group: $0<X<11500$, number of sites: $12$)
"Use Pearson's goodness-of-fit method to determine if the potentially important sites are randomly distributed over the genome in the sense given above (that is, to determine if the counts in the table above are consistent with an equiprobable model)."
I understand how to use Pearson's goodness-of-fit model but my professor never explained what an equiprobable model is. I am therefore unsure how to find the probability of each range to be used in calculations for the goodness-of-fit. Furthermore, I am unsure about what $n$ would be. Is it $20$ or is it $296$ or is it $23000$?
Answer: The equiprobable model is that there are an equal number of sites in each location group, i.e., $296/20=14.8$ sites per group, and, assuming that you are using the $\chi^2$ test, you should use a $\chi^2$ statistic with one less degree of freedom than the number of groups, i.e.,$19$ degrees of freedom.


Offline Signing 2/3 Multisig

Question: Interested in weather offline signing for 2/3 Multisig wallets is possible in this setup.
I have three computers Airgapped from the internet, and a USB. I imagine i can pull down some outputs for the ring signature creation from the blockchain from a online connected computer. I put these outputs onto a USB stick and transfer them to computer A, A conducts some offline signing process and builds the transaction, then i transfer on a USB A's signed TX + key image which B also signs. then that tx is taken to the online computer and submitted to the network.
So i have some questions, is the process described above possible? if so how would i get the data from the online computer into computer A, IE how does the process work is there some command in the CLI?
Answer: Details of multisig in the answers to this question: How to Use Monero Multisignature Wallets (2/2 & 2/3)
But no, actual signing doesn't need to be done while online.

Offline Signing 2/3 Multisig


Updating from Jaxb 1 to Jaxb 2

Question: I'm looking to update our project's jaxb version from 1 to 2.  Has anyone tried doing this on their projects and are there any tips that anyone wanting to do this?  I understand that each project is unique, I'm just looking for general tips.
Answer: JAXB2 will generate enum classes for simpletype restrictions.  Any Java code which relies on setting string values for uses of these types will require you to use the appropriate enum instead.  I think this is great, since you get the typechecking when compiling rather than a validation warning at runtime.
JABX2 uses typed lists instead of untyped lists, so you can remove a lot of casting from your java code.
Date support is greatly improved.  IIRC, most of the date types in JAXB1 generate Calendar, whereas in JAXB2 they generate XMLGregorianCalendar.
Answer: Today I was reading a tutorial on JAXB 1, and tried compiling the example using JAXB 2.1 (as included in JavaSE 6).
The elements in the XSD used unnamed types, such as:
<code><xs:element name="logging">
        <xs:complexType>
                <xs:attribute name="debug" type="xs:boolean" use="required"/>
                <xs:attribute name="file" type="xs:string" use="required"/>
        </xs:complexType>
</xs:element>
</code>
For what I see, JAXB 1.0 generated a Logging class and a LoggingType class (referring to the unnamed type of the logging element), while JAXB 2 generates just a Logging class. This happens regularly on all tags of this example, so I guess this happens quite regularly in such cases. However, it sufficed to remove the "Type" suffix to fix the compilation, without any need for other changes.

Updating from Jaxb 1 to Jaxb 2


I'm trying to confirm my BCH is being held on my trezor

Question: When I go to https://trezor.io/claim-bch/ I'm being told my trezor needs a firmware update. However, I have updated my firmware on wallet.trezor.io. Is there an issue with claiming BCH? If not, why am I being told I need new firmware? My firmware version is 1.5.0.
Answer: TREZOR says that Bcash (Bitcoin Cash) will only be available in TREZOR Beta Wallet for now. They chose this strategy, as they don't want to force a firmware update on users that are not interested in Bcash. Mode details on Claim your Bcash (BCH) in TREZOR Wallet
Answer: This issue is now not relevant; on the current website - https://wallet.trezor.io - there is already a firmware, that supports Bitcoin Cash.


Why do hard links exist?

Question: I know what hard links are, but why would I use them? What is the utility of a hard link?
Answer: The main advantage of hard links is that, compared to soft links, there is no size or speed penalty. Soft links are an extra layer of indirection on top of normal file access; the kernel has to dereference the link when you open the file, and this takes a small amount of time. The link also takes a small amount of space on the disk, to hold the text of the link. These penalties do not exist with hard links because they are built into the very structure of the filesystem.
The best way I know of to see this is:
$ ls -id .
1069765 ./
$ mkdir tmp ; cd tmp
$ ls -id ..
1069765 ../

The -i option to ls makes it give you the inode number of the file. On the system where I prepared the example above, I happened to be in a directory with inode number 1069765, but the specific value doesn't matter. It's just a unique value that identifies a particular file/directory.
What this says is that when we go into a subdirectory and look at a different filesystem entry called .., it has the same inode number we got before. This isn't happening because the shell is interpreting .. for you, as happens with MS-DOS and Windows. On Unix filesystems .. is a real directory entry; it is a hard link pointing back to the previous directory.
Hard links are the tendons that tie the filesystem's directories together. Once upon a time, Unix didn't have hard links. They were added to turn Unix's original flat file system into a hierarchical filesystem.
(For more on this, see Why does '/' have an '..' entry?.)
It is also somewhat common on Unix systems for several different commands to be implemented by the same executable. It doesn't seem to be the case on Linux any more, but on systems I used in the past, cp, mv and rm were all the same executable. It makes sense if you think about it: when you move a file between volumes, it is effectively a copy followed by a removal, so mv already had to implement the other two commands' functions. The executable can figure out which operation to provide because it gets passed the name it was called by.
Another example, common in embedded Linuxes, is BusyBox, a single executable that implements dozens of commands.
I should point out that on most filesystems, users aren't allowed to make hard links to directories. The . and .. entries are automatically managed by the filesystem code, which is typically part of the kernel. The restriction exists because it is possible to cause serious filesystem problems if you aren't careful with how you create and use directory hard links. This is one of many reasons soft links exist; they don't carry the same risk.
Comment: About "The link also takes a small amount of space on the disk, to hold the text of the link." On modern file systems, no extra space is used to store the link path as the directory entry itself is used to store it, at least if the name isn't too long to fit. This is called "fast symlinks"
Comment: Also, if you delete the target of a symlink, the file is gone and the symlink is broken. An issue that does not exist with a hard link.
Comment: But hard links have a piece of info as well - their names. So it supposed to take space.
Comment: I would add that some applications do not know how to handle soft (sym)links, and thus hard links may be useful to avoid redundancies when configuring them by referencing to the same data/config files. An example is ioquake3, which can't follow symlinked pk3 files, but can follow hardlinked pk3 files.
Answer: One usage of hardlinks which is extremely useful is in incremental backups combined with rsync. It saves lot of space and makes the restoration procedure really easy. I use that approach for backup in my servers.
Take some time to read this explanation.
Answer: There are any number of uses.  I use them to create file-based locks.  The link(2) system call is atomic, unlike most other system calls.
Another use is within rsnapshot, where backups are taken over time using hard-links to reduce the amount of disk space.  If a file has not changed, then the file is hard-linked to the older instances of the file, files that have changed are copied anew.
I also use them to swap out config files on servers: rm file.cfg && ln ~/tmp/file.cfg file.cfg, then the ~/tmp/* files can be deleted safely.
Comment: Why the separate `ln` and `rm` instead of just a `mv`?
Answer: If after reading that wikipedia page your question is "why would I ever use them" then you don't understand what hard links are.
A link is a directory entry that points to blocks on disk. In other words every file on your system has at least one link. When you rm a file the actual system call is unlink(). It removes the directory entry. The blocks on disk haven't changed but the link is gone, thus the file is gone from the directory listing.
You personally may not ever use hard links, but they are all over your system. For example:
$ ls -li /bin | grep 53119771
53119771 -rwxr-xr-x 3 root root  26292 2010-08-18 10:15 bunzip2
53119771 -rwxr-xr-x 3 root root  26292 2010-08-18 10:15 bzcat
53119771 -rwxr-xr-x 3 root root  26292 2010-08-18 10:15 bzip2

You can see that bunzip2, bzcat and bzip all use the same inode. In essence, it is one file with three names. You could have three copies of the file, but why? It would only use up disk space unnecessarily.
Comment: This answer fails to provide any reason at all for using hard links over soft links.
Comment: But there is also a number of symlinks in `/bin`, I guess that's one of the sources of confusion. Why sometimes executables would be symlinked and sometimes - hardlinked?
Comment: The question didn't ask why should one prefer hard links or soft links. The question is "what is a hard link?" And that's the question I answered.
Answer: I should probably cover a pitfall scenario of hard links. A hard link will be just the same file with a different name and/or a different location as long as the original linked file exists. It's not even correct to think of the file as "original": both are directory entries in their own right, and both (or more) are all equal peers. For long-lived files, this may be a blessing, but if one of the pair is deleted and then created, even with the same name and contents, the files will separate.
Suppose you created a hardlink /foo/myfile linking to /repo/myfile. Both are pointers to the same file data; change one, the other changes. But suppose that /repo happens to hold a Git repository. If you check out a branch that does not contain myfile in it, /repo/myfile is deleted. At this moment, /foo/myfile becomes a simple copy of /repo/myfile, as it were at the moment the other of the pair was unlinked. It's easy not to even notice as you flip between branches that file repertoire changes, but, when you checkout the original branch, a new file /repo/myfile is created by Git. If you did not pay attention, you'd wonder why the two files now have different contents, although it is easy to grok, as the hard link relationship between the files has no idea about their names. A soft link, on the opposite, would survive through this delete-create cycle.
On the other hand, software that uses hard links is acutely aware of this, and Git is a prime example. Git clones a repository on the same filesystem for nearly free, because it uses hard links by default instead of copying files. For Git the hard link is a perfect use case, because its object and pack files never change, so one clone of the repository will never modify the other (Git knows not to hard-link modifiable files), and any of the clones can be deleted without any precaution: there is no need to track which one is the "original" and actually contain the files: any of hard links is an equal partner and "contains" the full file. Soft links just would not work here.
Another advantage of the hard link is that any link can be moved without breaking access to the file contents. With soft links, moving the original file renders all soft links to it dangling.
The bottom line is that in many use cases either link type works equally well, but in some one or the other type is advantageous. The efficiency, mentioned in many answers here, is probably of a very little concern with modern machines and filesystems, unless you are scavenging a filesystem on a FLASH chip of a puny embedded controller. The functional differences are more important, and usually dictate the engineering constraints and the ultimate choice:

The hard link "source" can be moved safely, while the soft link will break.
The hard link is indistinguishable from the file it was linked from, and the file is alive as long as any of the hard links is alive; the soft link is asymmetrical.
The hard-linked peer breaks out of the linked group if deleted and re-created, but the soft link does not lose its target.
The soft link may cross filesystems, the hard link cannot.
The soft link may point to a directory, the hard link usually cannot (and practically always should not).

Also, I must point that the library call that deletes a file is called unlink() for a reason! Every directory entry is just an initially singular hard link to its inode.
Answer: To add to the several good discussions already present...

The way resource access for programs is implemented in unix (i.e. "everything is a file"), means that the infrastructure for handling multiple references to a file is required for the OS to work at all, so there is no added cost here.
The way directories were implemented in the original unix filesystems (i.e. a fixed format list of (inode, name) pairs means that there is no extra cost on in the filesystem to having hardlinks (well, as long as we prevent cycles by disallowing hardlinke to directories (other than . and .. (is this begin to feel like lisp to anyone else?)))

so we get them for free.
Answer: Symlinks are very brittle. If any element within whatever path you use as the target changes, it will break. This might be caused by renaming the original file, moving it, or renaming any of its parent directories.
In contrast, a hard link will survive any of those actions, although it comes with its own gotchas — software that copies and moves files instead of writing to them, without checking if there are multiple hard links, will break the connection.
Comment: But if you want to associate filenames that are on two different file systems, you have to use a symlink. Also, if you move one entry of a hardlinked file to a different file system you do wind up with two copies of the file; something that may be unintended.
Comment: True. I personally rarely have that use case — it's all about using the appropriate type of link in a given situation.

Why do hard links exist?


Is it bad for a piano player to work out?

Question: I'm not sure if this is a myth, but is it bad for a pianist to work out (e.g. lift weights)? I've heard that building strength this way will reduce fine muscle control.
Comment: If this was the case, other occupations that require fine and precise hand motor skills (like surgery) would have recommendations against working out.  I cannot google any advice to surgeons to avoid gym, and, if this was the case and/or had some evidence, there would be at least some discussion on this topic on surgery forums and in articles describing technique, because precise and error-free surgery is much more important than precise musical performance.
Comment: I highly doubt it, as long as you're keeping up with your practice and not damaging your body or bulking to the point that you can't move your arms properly :P
Comment: Keep in mind that, of course, working out *incorrectly* can cause bad things to happen that may affect piano playing capabilities, like correct posture.
Answer: This is a myth.  An untrained person with large muscles will be just as clumsy as an untrained person with wimpy muscles.  Fine motor control is a skill learned independent from the rest of the muscles in your body - if it were related, all brass players would have gi-normous lips and pianists would have gi-normous hands, and as well all know, this is simply not the case.
Physique only becomes a factor when a given body type will not allow a person to play an instrument with correct technique.  For example, someone with a severe underbite who wants to learn to play clarinet.  Other examples would be a person with fantastically large hands who is interested in oboe or a person with a weak jaw that wants to play tuba.
With respect to piano, it usually comes down to hand size - the larger the hands the easier it is to play.  Certainly if you're of the muscular persuasion, piano will not hinder in the slightest as playing to the extremes of the instrument may be thought of like doing "flys."
Comment: Taking this to an illogical extreme: http://www.youtube.com/watch?v=r7Jb_4Y5A-4 :P
Comment: @JanDVorak - The largest issue with that would be pressing more than 1 key simultaneously, though I've never heard of this being an issue.  A larger and more prominent issue are fingers that are too short.  Pianists with short fingers can still be virtuosic, but they need to alter their technique a bit.
Comment: @nreilingh: ....what the hell?
Comment: Couldn't (literal) fat fingers be an issue when trying to hit individual keys? Not that fat fingers are caused by excercise...
Answer: Let me add some perspective here from a completely different angle: climbing.
Climbing is obviously a sport where people train a lot, and people "working out" in the sense of "sculpting an impressive body" tend to be amusingly bad (from the perspective of climbers not overly impressive to chicks while they keep their shirt on) at it.
That's because "working out" is generally geared towards gaining muscle mass.  In order to achieve that, repetitions in training sets are geared towards the 7-15 rep range.  Decidedly fewer reps (often as "excentric" loads somewhat akin to controlled yielding) only exercise maximum activation of muscle fibers, decidedly more reps are geared towards endurance, creating additional capillars and veins and circulation over time.
But the middle range used for body building profits from encouraging local buildup of storage space for nutrients and electrolytes around the muscle fibers doing the work but affects the actual available momentous maximum strength at best secondarily.
Since weight is a number one concern for climbers, and since the difficulties in a hard climb are either isolated (requiring quite brief peak bursts of power) or continuous for a longer passage (overhangs etc requiring endurance), the impressive "work out" musculature is dead weight not helpful for carrying you across larger passages.
For most music instruments you have a similar problem: of course you need bodily fitness and endurance and can profit from it.  But what you don't need is having to move bulky muscle pads along with your fingers that have more than desirable inertia, compete for room to move with other bulky muscles, and that tire easily nevertheless.
So you should really first figure out just what you mean by "working out" and what goals your working out is supposed to achieve, and then figure out whether the goals in itself are incompatible in some manner with doing music fast and effortlessly and/or whether some particular manner of pursuing those goals might interfere more with your musical interests than necessary.
If you are aiming to turn your body into a coherent sculpture, spindly underarms make for a somewhat incoherent picture.  But bulging underarms will interfere with what you can achieve in piano play.
Comment: "bulging underarms will interfere with what you can achieve in piano play" - if you gain this mass over a prolonged period, during which you continue to practise piano, I think you'd naturally adapt without noticing, unless you get into proper "strong-man" physique but that's a very niche area compared to just working out.
Answer: I ve started to play now after working out and it is terrible -  I am making much more mistakes, but unless I am not playing right after gym, it is ok - I would maybe say working out is better for pianist, you can play longer without fatigue (which causing errors).
Answer: I play the piano for more than 30 years. The type of workout that have been doing recently (past months) involves several different exercises using kettlebell weights. I am 100% sure that, if I play right after a workout woth kettlebells, my fingers do not respond to playing the piano in the usual way, they are more lazy, more stiff, it's like stepping back 15 years in my piano technique. The next day seems to be fine. I haven't figured out yet how the curve of recovery works in detail.


How large will a MySQL database be relative to the dump file?

Question: I'm restoring a ~52GB dump to a MySQL database. The ibdata1 file has already exceeded the size of the dump file and the restore is still incomplete. Is there any way to estimate the final size of the ibdata1 file if the size of the MySQL dump file is known?
Answer: Just from the words in your question I suspect the following: You most likely have innodb_file_per_table disabled.
NOTE : The following info is based on innodb_file_per_table being disabled
When insert data into InnoDB tables, everything and its grandmother lands in the system tablespace file, better known as ibdata1. What does ibdata1 actually contain?

Table Data
Table Indexes
Metadata
MVCC Info

Table Data and Indexes while initially bloat ibdata1. The metadata is just simply the data dictionary + the list of tablespace_ids assign on a per-table basis.
What about MVCC (Multiversioning Concurrency Control)? This represents the systrem objects designed to support transaction isolation, rollbacks, undo logs, insert buffers for secondayr indexes, and the double- write buffer.
You need to clean up the InnoDB infrastructure. I already wrote StackExchange posts on how and why to do this:

Why does InnoDB store all databases in one file?
Is innodb_file_per_table advisable?
https://stackoverflow.com/a/4056261/491757
https://serverfault.com/a/231400/69271

Getting back to your original question, the only way to estimate the size of the ibdata1 on reload would have been to run this query before the mysqldump:
<code>SELECT
    data_length/power(1024,3) InnoDBData,
    index_length/power(1024,3) InnoDBIndexes,
    (data_length+index_length)/power(1024,3) InnoDBSize
FROM
    information_schema.tables
WHERE
    engine='InnoDB';
</code>
This will report the size of the data in GB. Upon a fresh reload of the ibdata1 (with innodb_file_per_table disabled in your case), this would have been the rule of thumb for the size estimation.
From the dump file size, it is hard to judge because the combined total size of data pages and index pages maybe far less that the size of ibdata1 the dump was created from. That difference would be have leftover space from the bloating of MVCC system objects (rollback segments, undo logs, double-write buffer, secondary index insert buffer). From another perspective, data pages could outnumber index pages, and vice versa. This could be due to too many indexes, bad design, or just a judicious amount of data.
Comment: 50GB dump file resulted in 99GB ibdata1
Comment: Is your innodb_file_per_table enabled or not? Please run : SHOW VARIABLES LIKE 'innodb_file_per_table'; and tell me.
Comment: @RolandoMySQLDBA I believe the answer is certainly no if `ibdata1` became that large during restore.


Login loop screen problem

Question: After write my password the screens goes and give a line of code not readable for one second then goes back to login screen. Any help ? I have almost all my work there is an a partition on my surface pro 2017.
Answer: for some reason did you run startx with administrator privileges? (sudo xstart).
if so, you must change the root .Xauthority owner to your user. you should probably do the same with .ICEauthority.
Press Ctrl+Alt+F1 and login into the shell, then run "ls -lA". If you see the line:
-rw-------  1 root root   58 Ago 22 17:10 .Xauthority
 do chown yourusername:yourusername .Xauthority.
after that press Ctrl+Alt+F7 and login again.
cya.
Comment: Thanks for your answer Javier A. I have done what you said but not a success, now I have installed Juno but I have 2 new big problems with it, so I guess is that Microsoft Surface Pro's are not ideal for this OS
Answer: I've had that issue before as well and Javier A's answer usually works for me. There was one time that it didn't and the following command worked:
<code>sudo service lightdm restart
</code>

Login loop screen problem


First note of a chord vs bass note of a chord

Question: I am a bit confused as to what the bass note of a chord is. Isn't it the first note of the chord (or any of its inversions)?
Or it can be any note that not necessarily belongs to the chord, as long as it's the lowest note played? So a C chord can have D as a bass?
Comment: You may also want to know what the root note of a chord is: i.e.: What is the difference between a root note of a chord, and a bass note of a chord. "first note" has no meaning in music theory that I am aware of.
Comment: @amalgamate Yeah, I meant the lowest pitched note. The root is always the same for a given chord and the one that defines the chord, no matter of the order of the notes, right?
Comment: Correct. Here are some more words added so I can make that small comment.
Answer: The bass note of a chord is simply the lowest pitched note that is part of the harmony. If you are looking at the notes of a chord bottom up then yes it is the "first" note. The bass note of a chord in general is very important in defining how the chord functions so we make note of it in the form of inversions and slash chords to notate exactly what note is in the bass.
In your example, yes you could have a C major chord with a D in the bass and you would see it written as the slash chord C/D. Notice how the D is not a chord tone of a C major chord. When you see this it typically  alludes to a chromatic bass line that is taking you somewhere while the overall harmony is getting you there in a slightly different manner.  You may also see the chord written as a Cadd9/D which means almost the same thing, but now we are directly considering the bass note as a chord tone.
Comment: Not sure how important the C with D in the bass is for the OP but I would mention that C/D is a slash chord that can be used to spell out a sus chord in a Jazz setting, where C/E/G would be 7/9/4 of a D sus.  And just to be a little picky, this could be a part of a chromatic bass line but this particular chord would more typically be part of a diatonic step-wise bass line.
Answer: The bass note is the lowest note being played.  It's not an analytical term, merely a description of what's happening.
In harmony theory, the root of a chord is the letter-name that gives it it's name.  It may be at the bottom (root position).  3rd at the bottom gives first inversion, 5th at the bottom gives second inversion.  We could logically extend this to call a 7th chord with the 7th underneath as "third inversion", a 9th with the 9th underneath as "fourth inversion"... but we generally don't!
When we get into chords like C/D, let go of the theory book a bit!  It MIGHT be useful to call this a third inversion of C(add9), but almost certainly isn't.  More likely C/D refers to a quite specific voicing where the D HAS to be the bass note and shouldn't be included in the upper structure.
Answer: Well if you dont play the bass note of your chord that is the lowest note of any of your chords and let the bass player do the bass for you. Then it actually wont matter.because he can do all the jumbling of bass line he wants that would fit your chords.
Comment: A bit late comment. This does not answer my question at all. Actually I don't even play an instrument and I'm not in a band. I compose using computer software. I needed to understand if there is difference, if any, between for example, a C in 3rd inversion and a C/G chord.