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i keep resistors in drawers organized by the first digits of value. r - 1, r - 12, r - 15, r - 18, r - 22 and so on. ( same for capacitors ) r - 1 contains 100ohm, 1k, 10k... r - 22 contains 22ohm, 220ohm, 2. 2k, 22k... | https://api.stackexchange.com |
the felis catus genome has been published, annotated, and updated quite a bit since 1996, including spans of so - called intergenic regions, which are basically scaffolding and other structures, along with perhaps some unidentified genes, pseudogenes, regulatory sequences, etc. basically, pretty much the entire dna seq... | https://api.stackexchange.com |
( and really, it is too many ), so i worked backwards. the final results are here ( sorry, link expires 10 / 13 / 16. to regenerate, go to blast link above and enter catcatcatcatcatcatcatcatcatcat ). apparently, popular wisdom is incorrect, and felis catus chromosomes really contain 10 cats each, one more than is neede... | https://api.stackexchange.com |
brian hayes wrote a very interesting article from a mathematical point of view : especially the " reality intrudes " section. basically people had created fancy mathematical reasons why it has to be exactly 20. nature, being nature, does not follow the reasoning, but has its own ideas. in other words there was nothing ... | https://api.stackexchange.com |
you are referring to the landau notation. they are not different symbols for the same thing but have entirely different meanings. which one is " preferable " depends entirely on the desired statement. $ f \ in \ cal { o } ( g ) $ means that $ f $ grows at most as fast as $ g $, asymptotically and up to a constant facto... | https://api.stackexchange.com |
formulate necessary and sufficient criteria for asymptotic notation as we use them in algorithmics, show that the common definition fails to meet them and provide a ( the, in fact ) workable definition. a general definition of the o - notation for algorithm analysis by k. rutanen et al. ( 2015 ) | https://api.stackexchange.com |
the question is relatively broad and one should take into account that the brain not only consists of neurons, but also glial cells ( supportive cells ) and pre - mitotic neuronal stem cells. furthermore, as critical fellow - scientists have indicated, developmental stage is very important, as the developing embryonic ... | https://api.stackexchange.com |
interesting question! the cause of tears and itching is the chemicals produced by onion ( allium cepa ). lets go into some details. onions, coming from the family liliaceae ( also containing garlic, chives, scallions and leeks ) store compounds known as amino acid sulfoxides, and the one we are talking about here is s ... | https://api.stackexchange.com |
c _ 3h _ 6o ~ + ~ h _ 2so _ 4 ~ + ~ 3 ~ h _ 2s } $ as you see, one of the products of hydrolysis of propanethial - s - oxide is hydrogen sulfide ( $ \ ce { h _ 2s } $ ). just like $ \ ce { h _ 2so _ 4 } $, $ \ ce { h _ 2s } $ also causes irritation in the eyes ( its effect on eyes has been well documented, see lambert ... | https://api.stackexchange.com |
do they exist? yes what are they called? marilyn roossinck calls them viral mutualistic symbiotes. she has an excellent review here. what are some examples? my personal favorite is gb - virus c, or hepatitis g, which appears to slow the progression of hiv using a number of different mechanisms : box 1. summary of the e... | https://api.stackexchange.com |
here are the $ \ ce { h - x - h } $ bond angles and the $ \ ce { h - x } $ bond lengths : \ begin { array } { lcc } \ text { molecule } & \ text { bond angle } / ^ \ circ & \ text { bond length } / \ pu { pm } \ \ \ hline \ ce { h2o } & 104. 5 & 96 \ \ \ ce { h2s } & 92. 3 & 134 \ \ \ ce { h2se } & 91. 0 & 146 \ \ \ hl... | https://api.stackexchange.com |
a bit wider. this explanation would be consistent with the $ \ ce { h - s - h } $ angle being slightly larger than the corresponding $ \ ce { h - se - h } $ angle. since the $ \ ce { h - se } $ bond is longer then the $ \ ce { h - s } $ bond, the interorbital electron repulsions will be less in the $ \ ce { h2se } $ ca... | https://api.stackexchange.com |
to my knowledge the pumping lemma is by far the simplest and most - used technique. if you find it hard, try the regular version first, it's not that bad. there are some other means for languages that are far from context free. for example undecidable languages are trivially not context free. that said, i am also inter... | https://api.stackexchange.com |
it can be broken into those five parts and have every derived pumped string remain in the language. the string $ s = a ^ { p } b ^ { p } a ^ { p } b ^ { p } $ is a suitable choice for this proof. now we just have to look at where $ v $ and $ y $ can be. the key parts are that $ v $ or $ y $ has to have something in it ... | https://api.stackexchange.com |
y $, but we know that they're in order ). then when we pump down ( i. e. the $ i = 0 $ case ), we get the new string $ s'= a ^ { p - k _ { 1 } } b ^ { p - k _ { 2 } } a ^ { p } b ^ { p } $, but then if $ s'$ could be split into $ ww $, the midpoint must be somewhere in the second $ a $ section, so the first half is $ a... | https://api.stackexchange.com |
let the real values data matrix $ \ mathbf x $ be of $ n \ times p $ size, where $ n $ is the number of samples and $ p $ is the number of variables. let us assume that it is centered, i. e. column means have been subtracted and are now equal to zero. then the $ p \ times p $ covariance matrix $ \ mathbf c $ is given b... | https://api.stackexchange.com |
that singular values are related to the eigenvalues of covariance matrix via $ \ lambda _ i = s _ i ^ 2 / ( n - 1 ) $. principal components are given by $ \ mathbf x \ mathbf v = \ mathbf u \ mathbf s \ mathbf v ^ \ top \ mathbf v = \ mathbf u \ mathbf s $. to summarize : if $ \ mathbf x = \ mathbf u \ mathbf s \ mathb... | https://api.stackexchange.com |
$ pcs by the corresponding principal axes $ \ mathbf v _ k ^ \ top $ yields $ \ mathbf x _ k = \ mathbf u _ k ^ \ vphantom \ top \ mathbf s _ k ^ \ vphantom \ top \ mathbf v _ k ^ \ top $ matrix that has the original $ n \ times p $ size but is of lower rank ( of rank $ k $ ). this matrix $ \ mathbf x _ k $ provides a ... | https://api.stackexchange.com |
there is still a lot to be learned about the roles introns play in biological processes, but there are a couple of things that have been pretty well established. introns enable alternative splicing, which enables a single gene to encode multiple proteins that perform different functions under different conditions. for ... | https://api.stackexchange.com |
this is a very interesting question. basically ( and this is the short answer ), geckos possess a unique self - cleaning mechanism in their feet which synthetic nano tapes do not have. this capability allows geckos to maintain their adhesive properties even in dusty environments. gecko feet mechanism gecko feet are cov... | https://api.stackexchange.com |
cleaning in gecko setae via digital hyperextension robust self - cleaning and micromanipulation capabilities of gecko spatulae and their bio - mimics carbon nanotube - based synthetic gecko tapes | https://api.stackexchange.com |
fun question! as you pointed out, $ $ \ theta \ approx 1. 22 \ frac { \ lambda } { d } $ $ for a human - like eye, which has a maximum pupil diameter of about $ 9 \ \ mathrm { mm } $ and choosing the shortest wavelength in the visible spectrum of about $ 390 \ \ mathrm { nm } $, the angular resolution works out to abou... | https://api.stackexchange.com |
some rotation ) again to get decent sampling of different baseline orientations. still, it seems like with a sufficiently sophisticated processor ( elf brain? ) he could achieve the reported observation. lubos motl points out some other possible difficulties with interferometry in his answer, primarily that the combina... | https://api.stackexchange.com |
is thicker than $ 24 \ \ mathrm { km } $ but its density drops rapidly with altitude. on the other hand the relatively uniform density and temperature at fixed altitude would cause less variation in refractive index than in the vertical direction, which might improve seeing. if i had to guess, i'd say that for very sti... | https://api.stackexchange.com |
there are several methods to do the conversion from finite automata to regular expressions. here i will describe the one usually taught in school which is very visual. i believe it is the most used in practice. however, writing the algorithm is not such a good idea. state removal method this algorithm is about handling... | https://api.stackexchange.com |
). l [ k, j ] l [ i, j ] + = l [ i, k ]. star ( l [ k, k ] ). l [ k, j ] l [ j, i ] + = l [ j, k ]. star ( l [ k, k ] ). l [ k, i ] note that both with a pencil of paper and with an algorithm you should simplify expressions like star ( ε ) = ε, e. ε = e, ∅ + e = e, ∅. e = ∅ ( by hand you just don't write the edge when ... | https://api.stackexchange.com |
state can be initial, too etc. note that now that the algorithm is written, this is a lot like the transitive closure method. only the context of the usage is different. i do not recommend implementing the algorithm, but using the method to do that by hand is a good idea. | https://api.stackexchange.com |
you're the second person i have ever seen using ncbi " chromosome names " ( they're more like supercontig ids ). normally i would point you to a resource providing mappings between chromosome names, but since no one has added ncbi names ( yet, maybe i'll add them now ) you're currently out of luck there. anyway, the qu... | https://api.stackexchange.com |
when the world was younger, and computers weren't all glorified pcs, word sizes varied ( a dec 2020 we had around here had 36 bit words ), format of binary data was a contentious issue ( big endian vs little endian, and even weirder orders of bits were reasonably common ). there was little consensus on character size /... | https://api.stackexchange.com |
as requested i'm posting this an answer. i wrote a short sage script to check the primality of numbers of the form $ 10 ^ n + 333 $ where $ n $ is in the range $ [ 4, 2000 ] $. i found that the following values of $ n $ give rise to prime numbers : $ $ 4, 5, 6, 12, 53, 222, 231, 416. $ $ edit 3 : i stopped my laptop's ... | https://api.stackexchange.com |
) : k = 10 ^ n + 333 if ( is _ prime ( k ) ) : print n and to check for numbers of the form $ 10 ^ n + 3 * 10 ^ i + 33 $ : for n in range ( 0, 500 ) : k = 10 ^ n + 33 for i in range ( 2, n ) : l = k + 3 * 10 ^ i if ( is _ prime ( l ) ) : print l | https://api.stackexchange.com |
a couple of decades ago i was peripherally involved with some research on the properties of ice cream being done by the company walls in the uk. the work was on relating the consistency of the ice cream to the microstructure, so it was quite closely related to your question. anyhow, ice cream has a surprisingly complic... | https://api.stackexchange.com |
it is commonly said, that a cyclopropane fragment behaves somewhat like a double bond. it can conjugate, and pass mesomeric effect similar to a double bond, but the donor orbital is $ \ sigma _ { \ ce { c - c } } $ instead of $ \ pi _ { \ ce { c = c } } $. cyclopropane can be considered as a complex of a carbene and an... | https://api.stackexchange.com |
), the cation has remarkable stability. similar effects are common in the chemistry of small bicyclic systems, with norbornane derivitives being the chosen test subjects for decades with the 2 - norbornyl cation being probably the most well - known example. march's advanced organic chemistry, 7th ed., section 10. c. i ... | https://api.stackexchange.com |
bowtie2 is no longer the fastest aligner. as you point out, bwa is faster, despite being based on the same burrows - wheeler transform as bowtie2. as @ user172818 points out, bwa - aln will work better for very short sequences under 36bp. for transcript mapping, salmon and kallisto are much faster, but have been design... | https://api.stackexchange.com |
i'd like to throw a tentative explanation for the ortho effect into the ring : in the molecules in question, an interaction between the protons of the methyl group and the lone pair of the amine nitrogen and the negative charge on the carboxylate, respectively, can be assumed. in the first case, the electron density on... | https://api.stackexchange.com |
as pointed out by @ johnrobertson in bag of tricks for denoising signals while maintaining sharp transitions, total variaton ( tv ) denoising is another good alternative if your signal is piece - wise constant. this may be the case for the accelerometer data, if your signal keeps varying between different plateaux. bel... | https://api.stackexchange.com |
( v ) - 1 / rho, 0 ). * sign ( v ) ; y = y - rho * ( u - d ( f ) ) ; end function y = d ( x ) y = [ diff ( x ) ; x ( 1 ) - x ( end ) ] ; function y = dt ( x ) y = [ x ( end ) - x ( 1 ) ; - diff ( x ) ] ; results : | https://api.stackexchange.com |
short answer yes. handedness ( or behavioral lateralization ) has been documented in numerous vertebrates ( mammals, reptiles and birds ) as well as invertebrates. this includes domestic cats ( see wells & millsopp 2009 ). long answer there have been numerous studies that have documented behavioral lateralization in ma... | https://api.stackexchange.com |
1997. lateralized behaviors in mammals and birds : bradshaw & rogers 1993 ; rogers & andrew 2002. lateralized behaviors in lower vertebrates : bisazza et al. 1998 ; vallortigara et al. 1999. some examples : invertebrates some spiders appear to favor certain appendages for prey handling and protection ( ades & novaes ra... | https://api.stackexchange.com |
. lateralization of neural control for vocalization by the frog ( rana pipiens ). psychobiology, 21, 243 – 248. bisazza, a., cantalupo, c., robins, a., rogers, l. j. & vallortigara, g. ( 1996 ). right - pawedness in toads. nature, 379, 408. bisazza, a., rogers, l. j. & vallortigara, g. ( 1998 ). the origins of cerebral... | https://api.stackexchange.com |
evolution of asymmetry for functional specialization. biology letters, 3 ( 2 ), 169 - 173. mcgrew, w. c., & marchant, l. f. ( 1997 ). on the other hand : current issues in and meta ‐ analysis of the behavioral laterality of hand function in nonhuman primates. american journal of physical anthropology, 104 ( s25 ), 201 ... | https://api.stackexchange.com |
##4. vallortigara, g., rogers, l. j. & bisazza, a. ( 1999 ). possible evolutionary origins of cognitive brain lateralization. brain research reviews, 30, 164 – 175. wells, d. l., & millsopp, s. ( 2009 ). lateralized behaviour in the domestic cat, felis silvestris catus. animal behaviour, 78 ( 2 ), 537 - 541. zucca, p.,... | https://api.stackexchange.com |
factor out the $ 2 ^ n $ and you get : $ 2 ^ n ( 100 + 20 + 8 ) = 2 ^ n 128 = 2 ^ { n + 7 } $ since $ 2 ^ 7 = 128 $ | https://api.stackexchange.com |
dilawar says in 2. that he knows linear dependence! so i will give a proof, similar to that of themachinecharmer, which uses linear independence. suppose each matrix is $ n $ by $ n $. we consider our matrices to all be acting on some $ n $ - dimensional vector space with a chosen basis ( hence isomorphism between line... | https://api.stackexchange.com |
zero padding allows one to use a longer fft, which will produce a longer fft result vector. a longer fft result has more frequency bins that are more closely spaced in frequency. but they will be essentially providing the same result as a high quality sinc interpolation of a shorter non - zero - padded fft of the origi... | https://api.stackexchange.com |
there are whole journals based primarily around publishing open source tools. the primary example of that is " bioinformatics ", where a lot of the open - source tools are published. we've also had luck publishing in the nucleic acids research yearly special webservers issue, since we make galaxy wrappers around our to... | https://api.stackexchange.com |
blood clots inside the body have an unfortunate tendency to get into the bloodstream and cause blockages, leading to severe problems such as strokes or heart attacks this statement is primarily true only for blood clots within blood vessels, especially in the veins. when you are talking about bruising, you are talking ... | https://api.stackexchange.com |
every cell phone ( as well as laptop and nearly everything with a rechargeable battery ) uses liion / lipo ( essentially equivalent for the purposes of this discussion ). and you're right : in terms of actual incidences, lithium - ion and lithium - polymer are the safest battery chemistry to be in wide use, bar none. a... | https://api.stackexchange.com |
, such as lead - acid or nimh or nicad, are not pressurized at room temperature, though heat does generate some internal pressure. they also have aqueous, non - flammable electrolytes. they store energy in the form of a relatively slow oxidation / reduction reaction, one whose rate of energy release is too low to, say,... | https://api.stackexchange.com |
an irreversible chemical reaction and will form metallic shunts. these shunts will be invisible, until charging expands part of the battery enough that the separating membrane is punctured by one of these shunts, creating a dead short, which of course results in fire, etc. : the lithium - ion failure mode we know and l... | https://api.stackexchange.com |
in a giant jet of flame for several seconds, and then continuing general burning - related activities for a bit after that. this is a chemical fire, so you cannot extinguish it ( lithium - ion batteries will still shoot out huge jets of fire even in the vacuum of space. the oxidizer is contained inside, it doesn't need... | https://api.stackexchange.com |
for the first part of my question, i found this very useful comparison for performance of different linear interpolation methods using python libraries : below is list of methods collected so far. standart interpolation, structured grid : unstructured ( scattered ) grid : 2 large projects that include interpolation : (... | https://api.stackexchange.com |
the word photon is one of the most confusing and misused words in physics. probably much more than other words in physics, it is being used with several different meanings and one can only try to find which one is meant based on the source and context of the message. the photon that spectroscopy experimenter uses to ex... | https://api.stackexchange.com |
charged particles, or the compton scattering ). this photon has usually definite momentum and energy ( hence also definite frequency ), and fairly definite position, since it participates in fairly localized scattering events. theorists use the word photon with several meanings as well. the common denominator is the ma... | https://api.stackexchange.com |
sometimes with schroedinger's equation added ). these are for example the photoelectric effect, compton scattering, black - body radiation and perhaps others. there always was a minority group of physicists who avoided the concept of photon altogether for this kind of phenomena and preferred the idea that the possibili... | https://api.stackexchange.com |
if you want the shifted output of the ifft to be real, the phase twist / rotation in the frequency domain has to be conjugate symmetric, as well as the data. this can be accomplished by adding an appropriate offset to your complex exp ( )'s exponent, for the given phase slope, so that the phase of the upper ( or negati... | https://api.stackexchange.com |
there are huge differences in culture, coding style, and capabilities. probably the fundamental difference is trilinos tries to provide an environment for solving fem problems and petsc provides an environment for solving sparse linear algebra problems. why is that significant? trilinos will provide a large number of p... | https://api.stackexchange.com |
the misunderstanding lies in what constitutes " solving " an optimization problem, e. g. $ \ arg \ min f ( x ) $. for mathematicians, the problem is only considered " solved " once we have : a candidate solution : a particular choice of the decision variable $ x ^ \ star $ and its corresponding objective value $ f ( x ... | https://api.stackexchange.com |
for the shield to be effective, it requires as low impedance connection as possible to your shield ground. i think those recommending resistors, or not connecting it to ground at all, or strictly talking about your digital logic ground, and assuming you have a separate shield ground. if you have a metal enclosure, this... | https://api.stackexchange.com |
if this is a topic that really interests you, i'd suggest searching for papers / reviews / opinions written by didier raoult. raoult is one of the original discoverers of the massive mimivirus and his work will lead you to some truly fascinating discussions that i couldn't hope to reproduce here. the main argument for ... | https://api.stackexchange.com |
theory alluded to above that eukaryotic life itself actually formed because of viruses. i can expand on this if you like, but here are some great sources : boyer, m., yutin, n., pagnier, i., et al. 2009. giant marseillevirus highlights the role of amoebae as a melting pot in emergence of chimeric microorganisms. pnas. ... | https://api.stackexchange.com |
i'm not sure but i think the answer is no, for rather subtle reasons. i asked on theoretical computer science a few years ago and didn't get an answer that goes beyond what i'll present here. in most programming languages, you can simulate a turing machine by : simulating the finite automaton with a program that uses a... | https://api.stackexchange.com |
$ values. this means that there is a finite maximum number of addressable objects. the values of char _ bit and sizeof ( void * ) are observable, so if you run out of memory, you can't just resume running your program with larger values for those parameters. you would be running the program under a different programmin... | https://api.stackexchange.com |
get the power of deterministic pushdown automata. i can't find a way to go further. ( of course you could make the program store the tape content externally, through file input / output functions. but then you wouldn't be asking whether c is turing - complete, but whether c plus an infinite storage system is turing - c... | https://api.stackexchange.com |
the state \ begin { equation } | \ psi \ rangle = \ frac { 1 } { \ sqrt { 2 } } \ left ( | \ psi _ 1 \ rangle + | \ psi _ 2 \ rangle \ right ) \ end { equation } is a pure state. meaning, there's not a 50 % chance the system is in the state $ | \ psi _ 1 \ rangle $ and a 50 % it is in the state $ | \ psi _ 2 \ rangle $... | https://api.stackexchange.com |
equation } \ begin { equation } | \ psi _ 2 \ rangle = \ frac { 1 } { \ sqrt { 2 } } ( | \ phi _ 1 \ rangle - | \ phi _ 2 \ rangle ) \ end { equation } then i can ask for the probability of measuring $ \ phi $ and having the system collapse to the state $ | \ phi _ 1 \ rangle $, given that the state is $ | \ psi \ rang... | https://api.stackexchange.com |
first off, don ’ t use rpkms. they are truly deprecated because they ’ re confusing once it comes to paired - end reads. if anything, use fpkms, which are mathematically the same but use a more correct name ( do we count paired reads separately? no, we count fragments ). even better, use tpm ( = transcripts per million... | https://api.stackexchange.com |
written. if you want to apply the code to multiple libraries, nothing is easier using dplyr › : tidy _ expression = tidy _ expression % > % group _ by ( sample ) % > % mutate ( fpkm = fpkm ( count, col _ data $ lengths ) ) however, the data in the question isn ’ t in tidy data format, so we first need to transform it a... | https://api.stackexchange.com |
two bits to this answer ; firstly, the class of languages recognised by turing machines is not context sensitive, it's recursively enumerable ( context sensitive is the class of languages you get from linear bound automata ). the second part, assuming we adjust the question, is that yes, a two - stack pda is as powerfu... | https://api.stackexchange.com |
the best solution that i know of is to program the symbolic expressions in mathematica, maple, or sympy ; all of the links go directly to the code generation documentation. all of the programs above can generate code in c or fortran. none of the programs above mentions accuracy in ieee 754 arithmetic ; in general, it w... | https://api.stackexchange.com |
this terminology goes waaaaay back to the days of vacuum tubes. generally, you would mount a number of tube - sockets on standoffs to a piece of wood ( the actual " breadboard " ), and do all the wiring with point - point wire and the components just hanging between the various devices. if you needed additional connect... | https://api.stackexchange.com |
relays offer complete isolation between the activating circuit and the load. they can switch ac and dc, and be activated by ac or dc. they can be very robust. they also have the advantage that one can often see if the device is actuated, and one can even hear the actuation in many cases. | https://api.stackexchange.com |
unlike your question suggests, it is not true that velocity is varied independently of position. a variation of position $ q \ mapsto q + \ delta q $ induces a variation of velocity $ \ partial _ t q \ mapsto \ partial _ t q + \ partial _ t ( \ delta q ) $ as you would expect. the only thing that may seem strange is th... | https://api.stackexchange.com |
higher spin particles have to be coupled to conserved currents, and there are no conserved currents of high spin in quantum field theories. the only conserved currents are vector currents associated with internal symmetries, the stress - energy tensor current, the angular momentum tensor current, and the spin - 3 / 2 s... | https://api.stackexchange.com |
ultra - short distance scattering, and consider the ultra - violet fixed point theory as the field theory you are studying, and this is sufficient to understand most examples. but the extended - object exception is the most important one, and must always be kept in the back of the mind. coleman and mandula assume a mas... | https://api.stackexchange.com |
with the supercurrent having spin 3 / 2. what is a qft? here this is a practical question - - - for this discussion, a quantum field theory is a finite collection of local fields, each corresponding to a representation of the poincare group, with a local interaction lagrangian which couples them together. further, it i... | https://api.stackexchange.com |
the scattering amplitude from this exchange around the k - axis by an angle $ \ theta $ counterclockwise, you should get a phase of $ \ theta / 2 $ in the outgoing photon phases. in terms of mandelstam variables, the angular amplitude goes like $ ( 1 - t ) ^ j $, since t is the cosine of the scattering variable, up to ... | https://api.stackexchange.com |
$ $ { g _ { \ mu \ nu } - { k _ \ mu k _ \ nu \ over m ^ 2 } \ over k ^ 2 + m ^ 2 } $ $ the numerator projects the helicity to be perpendicular to k, and the second term is problematic. there are directions in k - space where the propagator does not fall off at all! this means that when you scatter by spin - 1 exchange... | https://api.stackexchange.com |
large energies, just from the mandelstam argument presented before. the propagator growth leads to unphysical growth in scattering exchanging this particle, unless the spin - 3 / 2 field is coupled to a conserved current. the conserved current is the supersymmetry current, by the haag – lopuszanski – sohnius theorem, b... | https://api.stackexchange.com |
##blity for spin 2 in chapter 1 of green schwarz and witten, but i don't remember what it is, and i don't know whether it is viable. summary i believe that these arguments are due to weinberg, but i personally only read the sketchy summary of them in the first chapters of green schwarz and witten. they do not seem to m... | https://api.stackexchange.com |
no cancellations. it's actually remarkable that it works as a guideline, and that there aren't a slew of supersymmetric exceptions of higher spin theories with supersymmetry enforcing propagator cancellations and unitarization. maybe there are, and they just haven't been discovered yet. maybe there's a better way to st... | https://api.stackexchange.com |
people said silly things about the consistency of quantum field theory - - - but to be fair, quantum field theory people said equally silly things about s - matrix theory. weinberg came up with these heuristic arguments in the 1960s, which convinced him that s - matrix theory was a dead end, or rather, to show that it ... | https://api.stackexchange.com |
initial advice always run with - ksp _ converged _ reason - ksp _ monitor _ true _ residual when trying to learn why a method is not converging. make the problem size and number of processes as small as possible to demonstrate the failure. you often gain insight by determining what small problems exhibit the behavior t... | https://api.stackexchange.com |
type none. for simple saddle point problems, try - pc _ type fieldsplit - pc _ fieldsplit _ type schur - pc _ fieldsplit _ detect _ saddle _ point. see the user's manual and pcfieldsplit man page for more details. for more difficult problems, read the literature to find robust methods and ask here ( or petsc - users @ ... | https://api.stackexchange.com |
or make sure that all the equations are scaled in the same way if you want to use rediscretized coarse levels. the matrix is very ill - conditioned. check the condition number using the methods described here. try to improve it by choosing the relative scaling of components / boundary conditions. try - ksp _ diagonal _... | https://api.stackexchange.com |
first of all, as skillman and dan have pointed out, profiling is essential. i personally use intel's vtune amplifier on linux as it gives me a very fine - grained overview of where time was spent doing what. if you're not going to change the algorithm ( i. e. if there will be no major changes that will turn all your op... | https://api.stackexchange.com |
not that you should write stuff in assembler directly for that architecture, but it might inspire you to find some other optimizations that you may have missed. knowing about a feature is a necessary first step to writing code that can exploit it. update it's been a while since i wrote this and i hadn't noticed that it... | https://api.stackexchange.com |
don't care about the why, and the how is, well, what we do best. for example, i'm currently working with a bunch of computational cosmologists on writing a better version of their simulation code, based on sph and multipoles. it took about three meetings to stop talking in terms of dark matter and galaxy haloes ( huh? ... | https://api.stackexchange.com |
maybe to see the difference between rank 2 tensors and matrices, it is probably best to see a concrete example. actually this is something which back then confused me very much in the linear algebra course ( where we didn't learn about tensors, only about matrices ). as you may know, you can specify a linear transforma... | https://api.stackexchange.com |
really accurate. the rank of a tensor has to be given by two numbers. the vector to vector mapping is given by a rank - ( 1, 1 ) tensor, while the quadratic form is given by a rank - ( 0, 2 ) tensor. there's also the type ( 2, 0 ) which also corresponds to a matrix, but which maps two covectors to a number, and which a... | https://api.stackexchange.com |
there is no such right triangle. the maximum possible altitude is half the hypotenuse ( inscribe the triangle into a circle to see this ), which here is $ 5 $ inches. you would only get $ 30 $ square inches if you tried to compute the area without checking whether the triangle actually exists. | https://api.stackexchange.com |
addition is fast because cpu designers have put in the circuitry needed to make it fast. it does take significantly more gates than bitwise operations, but it is frequent enough that cpu designers have judged it to be worth it. see both can be made fast enough to execute within a single cpu cycle. they're not equally f... | https://api.stackexchange.com |
the sampling rate of a real signal needs to be greater than twice the signal bandwidth. audio practically starts at 0 hz, so the highest frequency present in audio recorded at 44. 1 khz is 22. 05 khz ( 22. 05 khz bandwidth ). perfect brickwall filters are mathematically impossible, so we can't just perfectly cut off fr... | https://api.stackexchange.com |
i work with an old toolmaker who also worked as a metrologist who goes on about this all day. it seems to boil down to exploiting symmetries since the only way you can really check something is against itself. squareness : for example, you can check a square by aligning one edge to the center of straight edge and traci... | https://api.stackexchange.com |
height varies as it rolls. edit : as mentioned by a commenter, this only checks diameter and you can have non - circular lobed shapes ( such as those made in centerless grinding and can be nearly imperceptibly non - circular ) where the diameter is constant but the radius is not. checking roundness via radius requires ... | https://api.stackexchange.com |
self - checking are what makes " straight ", " flat ", " round ", and " square " special. it's why we use these properties and not random arcs, polygons, or angles as references when calibrating stuff. actually making stuff rather than just measuring : up until now i mainly talked about measurement. the only manufactur... | https://api.stackexchange.com |
made though or how they are ground. there doesn't seem to be an obvious way to use spheres to make more spheres unlike the other things. | https://api.stackexchange.com |
graphviz should work. i believe that the images associated with the matrices in the university of florida sparse matrix collection were visualized using sfdp, a force - directed graph visualization algorithm developed by yifan hu. most of the matrices in the collection have a computational time associated with generati... | https://api.stackexchange.com |
your teacher was right. current is electric charges ( usually electrons ) moving. they don't do that by themselves for no reason, no more so than a shopping cart moves across the floor of a store by itself. in physics, we call the force that pushes charges the electromotive force, or " emf ". it is almost always expres... | https://api.stackexchange.com |
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