October 2014 - mathfun@mailman.xmission.com

Re: [math-fun] Phone question
by Henry Baker 10 Oct '14

10 Oct '14

Sorry to be dense, but what's a "phone call" ? At 08:12 PM 10/9/2014, James Propp wrote: >Sorry to veer a bit far from math, but some of you are phone-network folks, >so maybe you can tell me: What do you call it when person A calls person B >and after a few rings get shunted into voice-mail, without person B's phone >ever ringing? (It's not a "dropped call"; that means something different.) > >My wife and I have this kind of experience many times, and have sometimes >reproduced it with us and our two phones all in the same room or the same >car. It's not a device-dependent effect; all cellphone-types seem to >be equally susceptible. It's a network thing. It's the phone company saying >"Hey, we could be honest and admit that the network is too busy for us to >give you a connection right now, but then you'd probably consider switching >to one of our competitors, so we'll just pretend that your party isn't >answering." (Back in the days when AT&T had a monopoly, at least they were >honest. As Lily Tomlin put it: "We're the phone company. We don't care. We >don't have to.") > >Anyway, I'm considering switching carriers, except what if the competitors' >networks are even worse? What I need are comparative statistics on calls >that are never completed because of network issues. But before I can get >those numbers, I'll need to know what they're called! > >Can anyone supply the relevant phone jargon? > >Thanks, > >Jim Propp > >("Your call is important to us. That's why we want to make it last as long >as possible.")

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[math-fun] Phone question
by James Propp 10 Oct '14

10 Oct '14

Sorry to veer a bit far from math, but some of you are phone-network folks, so maybe you can tell me: What do you call it when person A calls person B and after a few rings get shunted into voice-mail, without person B's phone ever ringing? (It's not a "dropped call"; that means something different.) My wife and I have this kind of experience many times, and have sometimes reproduced it with us and our two phones all in the same room or the same car. It's not a device-dependent effect; all cellphone-types seem to be equally susceptible. It's a network thing. It's the phone company saying "Hey, we could be honest and admit that the network is too busy for us to give you a connection right now, but then you'd probably consider switching to one of our competitors, so we'll just pretend that your party isn't answering." (Back in the days when AT&T had a monopoly, at least they were honest. As Lily Tomlin put it: "We're the phone company. We don't care. We don't have to.") Anyway, I'm considering switching carriers, except what if the competitors' networks are even worse? What I need are comparative statistics on calls that are never completed because of network issues. But before I can get those numbers, I'll need to know what they're called! Can anyone supply the relevant phone jargon? Thanks, Jim Propp ("Your call is important to us. That's why we want to make it last as long as possible.")

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[math-fun] MH370 missing plane, update on the pathetic state of affairs
by Warren D Smith 09 Oct '14

09 Oct '14

I had earlier posted an simple high-school-geometry analysis, which given (1) handshake timings from satellite (2) assumption those controlling plane were not idiots (i.e. flew it on near-straight course and near-max-efficiency speed after it left radar coverage, did not try to commit suicide) conclude: the plane had to have ended up near the Pakistan/Afghanistan/Kazakhstan area. Also happen to conclude that the plane's course would have taken it mainly thru probably-low-radar areas, kind of as it it had been designed that way. I never managed to get any press or government attention for this simple analysis at all, far as I could tell. In the meantime, the officials in charge concluded several times it had to be in various watery places, which kept changing but ultimately ended up in the South Indian Ocean, at a place quite similar to where my geometry-analysis had predicted -- except actually there are two geometry solutions, and they picked the southern one I'd discarded as suicide, not the sensible northern one. They spent somewhere around $50M searching for it. At one point they announced they'd heard the "pinging" sounds and if so they should have located the plane soon after. Later they, much more quietly, announced they'd decided those "pings" were not genuine and they'd somehow confused themselves into "hearing" them, or they were a hoax. No trace of the plane, or debris, or anything, has been found to this day. So anyway, at that point I had several questions whose answers I did not see in the media I read, at least not in any comprehensible way: (Q1) why did they decide those pings were not genuine? (Q2) why did they decide it took the southern route? A NOVA television-science program just happened. It did not answer Q1. As far as I can presently tell, Q1 has no answer, they never had any evidence that the pings were not genuine, but I guess they eventually decided they would have found the plane if they had been. Kind of an (inherently unsatisfying) deduction from absence of evidence. For Q2, they *did* provide a claimed answer, which was "Doppler." The plane and a satellite exchanged handshakes every hour. And those handshake timings showed, at each hour, the plane had to be on a certain circle drawn on the globe. I already knew that. The new idea is that the frequency of those signals got shifted by doppler effects depending on the relative velocities & locations of the plane & satellite. The satellite logged frequency-error measurements for troubleshooting purposes. >From these logs, they deduced that the plane had to have taken the southern route. This analysis supposedly was carried out by the satellite company Inmarsat, whereupon everybody else believed it. However, do *we* believe it? I have been unable to find a published technical analysis on the internet. (Why was it kept secret? Why not release it for possible criticism?) Can anybody find one? The closest I found was http://aviationweek.com/commercial-aviation/routine-data-analysis-helped-pi… http://physicsbuzz.physicscentral.com/2014/03/how-did-inmarsat-really-find-… which both are pathetically un-detailed and offer no link to any real study. I will say this. Timing handshakes seems pretty easy technically, and if you could do it with 1 nanosec accuracy (which considering my computer runs at 2 GHz, seems possible) you'd measure the satellite-plane distance to +-1 foot. So I'm totally willing to believe those timing->distance deductions. But frequency measurements seem to me to be hard technically and to distinguish whether a plane is moving toward or away from you at 600 miles/hour you need to measure frequency with accuracy better than 2 parts in a million. Actually the plane in this case would NOT be moving toward/away from satellite, but almost perpendicularly to it, so more accuracy would be needed. In the limiting case of exact perpendicular motion at 600 miles/hour (or stationary) you'd need better than 1 part in 10^12 frequency accuracy to decide 600 versus 0. None of the media sources even says what the ping radio frequency was or how long the ping signals each lasted. If the ping was at 10 MHz and lasted 1 second, then clearly you are going to get, at best, about 1 part in 10^8 frequency accuracy, and that is probably too optimistic. But even that is assuming the plane's transmitter actually has an accurate fixed frequency at all. Actually, it is probably based on a quartz crystal, whose frequency varies with temperature and pressure (and with age since manufacture). Wikipedia says "Standard-quality quartz resonators of this type are warranted to have a long-term accuracy of about 6 parts per million at 31C (87.8F) temperature." It goes on to say that by means of thermal and other kinds of compensation, more expensive kinds of quartz resonators, e.g. used in chronometers, can attain 10X better accuracy. My guess would be probably some cheesy aircraft comm pinger (not intended for anything like the purpose it is here being used for) is not going to be using a fancy compensation scheme on its quartz crystal -- but again, none of the media I found even mention this issue. (A real study should.) So... do I believe in this doppler deduction? I have doubts. I'd want to see a genuine, published, available, and independently criticized study, before I would have those doubts removed. How about some tests with other planes? Were any done? For example, instead of concluding the plane went south, a perhaps equally valid conclusion might be "the pinger got a bit colder during a couple hours." -- Warren D. Smith http://RangeVoting.org

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Re: [math-fun] FullSimplify embarrassment contest
by Axel Vogt 09 Oct '14

09 Oct '14

> Fateman: > Log[Tan[x/2 + Pi/4]] - ArcSinh[Tan[x]] Differention (and using Maple) can give it as zero, though that is not a blackbox 'simplification command' > http://en.wikipedia.org/wiki/The_Guide_for_the_Perplexed Thx, the word choice in the article is funny for a paper :-)

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[math-fun] Architects Create a 3-D Printed Column
by Henry Baker 09 Oct '14

09 Oct '14

FYI -- Go to the linked article or Emerging Objects website to see very interesting & pretty pix. You could soon 3D print that Klein Bottle house that you've been lusting after! https://www.wired.com/2014/10/architects-create-3-d-printed-column-survives… http://www.emergingobjects.com/ Architects Create a 3-D Printed Column That Survives Earthquakes By Joseph Flaherty 10.09.14 6:30 am The aptly named Quake Column is a knurled pillar of 3-D printed concrete that combines an ancient Incan masonry technique with state-of-the-art manufacturing tools to create a structure that can withstand seismic shocks ***without mortar or rebar.*** [Rebar limits the life of concrete structures to ~100 years.] [Lots of pix.] Each block features molded handles and a code that tells the mason how the structure is to be assembled. Other experiments include turning waste product like hardwood sawdust into a building material. The result is an object with a 21st century design, but a 17th century patina. Emerging Objects experimented with a 3-D printer that produces objects made of sand and created this noise canceling wall. The wall's mass absorbs and release heat and the folds increase the surface area to help reduce sound levels. Emerging Objects has been focusing primarily on material explorations and producing small objects like this vase. These proof of concept models have emboldened the architects to take their approach to architectural scale applications. The result of these experiments are a catalog of parts that could one day be used to fabricate an entire home, from load-bearing walls to light-weight room dividers. In the last half decade thereÂs been a Cambrian Explosion of 3-D printers, filling every axis of competition from price to size to print resolution. Most engineers and designers have been fixated on tuning up the machines, but a California-based architecture firm called Emerging Objects is focused on pushing the limits of 3-D printer materials. The result is a structural column designed to withstand earthquakes. The aptly named Quake Column is a knurled pillar of 3-D printed concrete that combines an ancient Incan masonry technique with state-of-the-art manufacturing tools to create a structure that can withstand seismic shocks without mortar or rebar. In this system, bricks are designed in CAD tools to fit together like a 3-D puzzle and then printed in cement. Once assembled, interlocking features make the column resistant to earthquakes by preventing horizontal movement. ItÂs an interesting proof of concept, but utilizing a 3-D printer, rather than traditional ceramic manufacturing technique also unlocked a host of other advantages. The bricks are hollow, creating a high strength-to-weight ratio. Each brick is printed with a code that explains to the mason how the bricks should be configured. Molded handles in each brick make on-site assembly as easy as snapping together Legos. And according to the architectÂs calculations, this technique could be used to fabricate building code compliant, load-bearing walls. ÂWhile this was an experiment in connectivity, we have been able to create 3-D printed parts that are much stronger than reinforced concrete in compression,Â says architect Ronald Rael. ÂWe are also working on increasing the tensile strength of our materials using reinforcement fibers.Â Bone, Salt, Sawdust WhatÂs especially interesting is that the designers didnÂt set out to design a shake-resistant structure. Instead, it came out of a material exploration that explored using sawdust, ground-up tires, salt, and pulverized bone into effective, if strange, construction materials. Printing with such atypical materials might seem a bit gimmicky, but Emerging ObjectsÂ principalsÂ-Ronald Rael, an Associate Professor of Architecture at the University of California, Berkeley and Virginia San Fratello, an Assistant Professor of Design at San Jose StateÂ-take the pursuit of novel materials seriously. Together with a 10-person team, they have begun fabricating small objects, like tiles, screens, and home goods, but are quickly scaling production capacity to match their architectural ambitions. Emerging Objects employs off-the-shelf machines that typically use glue, or heat from lasers, to solidify layers of specially formulated plastic powders. However, these printers are more than capable of fabricating a complex shape, like a Klein Bottle from coffee grounds, if the designer is sufficiently experimental and willing to void the warranty on a six-figure machine. Their approach is a little off-kilter and some experiments, like bone and rubber printing, have yet to materialize into anything of note. When a breakthrough occurs, it tends to be spectacular, as is the case with their Walnut Screen. Made from hardwood sawdust, this waste product was given a second life when fused with a special glue and arrayed in a series of panels to divide a room. The screen boldly combines a 21st century form with a 17th century patina. ÂMost of our research takes a look at the past as so much has already been done,Â says San Fratello. ÂWe love to stand on the shoulders of the brilliant technologies that came before us and learn from them.Â Half a dozen architects and engineers are seriously experimenting with 3-D printing at an architectural scale, but almost all of them are focused on size. They share a goal to build full-size homesÂwalls, ceilings, the worksÂall in a single shot. Rael and San Fratello see their work differently, as catalog of systems and components to meet varied architectural needs. While others busy themselves trying to prove that itÂs possible to 3-D print a house, Rael and San Fratello are occupied with trying to design one people would actually want to live in.

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[math-fun] Fwd: hexagonal pyramids
by Bill Gosper 09 Oct '14

09 Oct '14

APG>At first I thought `gosh, an integer triangle with a 120° angle -- how amazing!'. Then I realised that it's basically just saying that |8 + 5w|² = 7², which is unremarkable when one considers that 8 + 5w is itself a square (of 3 + w), and the squared norm of 3 + w is 7. So basically we can create lots of these integer triangles. Starting from a + bw, we obtain: (a + bw)^2 = a^2 + 2abw + b^2w^2 = (a^2 - b^2) + (2ab - b^2)w which implies the existence of a 120° triangle with side lengths: a^2 - 2ab, 2ab - b^2, a^2 + b^2 - ab where we impose a > 2b to make everything positive. Your triad (3,5,7) is generated by setting (a,b) = (3,1). Incidentally, I seem to recall that the Ancient Egyptians marked out a loop of rope of length 12 units with marks at positions 0, 3, 7 and pulled it tight to function as a set-square. Your (3,5,7) triangle could presumably have been used as a similar set-hexagon...? Sincerely, Adam P. Goucher Sent: Wednesday, October 08, 2014 at 9:36 PM From: "Bill Gosper" < billgosper(a)gmail.com> To: math-fun(a)mailman.xmission.com Subject: [math-fun] Delayed reaction Hoohah? for waiting rooms and other foci of boredom: gosper.org/3-5-7hex.pdf (font deficiency may require downloading) --rwg Exactly. Last week I sent the kids ---------- Forwarded message ---------- From: Bill Gosper <billgosper(a)gmail.com> Date: Sun, Sep 28, 2014 at 12:56 PM Subject: hexagonal pyramids It is believed that ancient Egyptian surveyors laid out right angles by looping a rope with 3+4+5+1 equally spaced knots around three stakes, making a 3:4:5 triangle when the first and last knots coincide. With 3+5+7+1 knots, they could have laid out hexagonal fields instead of rectangular. Duh, with 1+1+1+1 knots, they could've made hexagons out of equilateral triangles. [...] ------- --rwg

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[math-fun] Ancient computers still live in cloud heaven
by Henry Baker 08 Oct '14

08 Oct '14

FYI -- No mention of 7094, PDP-10, Lisp Machines, etc. Wouldn't it be fun to boot up your favorite old computer on Amazon Web Services? Perhaps MIT can resurrect ITS & allow us old farts to log back in to check our old email. Stromasys loves "pennies from heaven": Oh every time it rains, it rains pennies from heaven Don't you know each cloud contains pennies from heaven You'll find your fortune fallin' all over town Be sure that your umbrella is upside down Trade them for a package of sunshine and flowers If you want the things you love, you must have showers So when you hear it thunder, don't run under a tree There'll be pennies from heaven for you and me http://www.metrolyrics.com/pennies-from-heaven-lyrics-billie-holiday.html http://www.datacenterdynamics.com/focus/archive/2014/10/stromasys-emulates-… Stromasys emulates legacy hardware in the cloud At last! Recycle your VAX, Alpha, PDP-11, HP 3000 and Sparc boxes 7 October 2014 by Max Smolaks Swiss software emulation expert Stromasys has launched a virtualization product that can take vintage VAX, Alpha, HP 3000, PDP-11, and Sparc applications to the cloud. Surprising numbers of critical services are running on platforms originally created for hardware which is no longer produced. Stromasys' service run them from a third-party data center, giving all the features and benefits of a cloud infrastructure, without having to recompile decades-old code. Out with the old PDP-11 and Vax by Digital Equipment Corporation (DEC), as well as HP 3000 by Hewlett-Packard were minicomputer systems created in the 1970s. The Sparc RISC chip (now owned by Oracle) was introduced by Sun Microsystems in 1987, while the 64-bit Alpha architecture from DEC appeared in 1992. Despite their venerable age, such systems are still used for many mission critical applications in fields such as banking, manufacturing and air traffic control. The OpenVMS operating system from the Vax, along with other venerable platforms, is still supported by HP. However, the aging components and disappearance of some suppliers (DEC was acquired by Compaq and then merged with HP) have made the operation of these systems on the original hardware increasingly difficult. Porting complete solutions to new hardware and a new OS is often expensive and associated with high risk. In response to this, Stromasys has launched a virtualization service that promises to solve the problem of legacy apps. It can reduce the costs associated with maintaining legacy infrastructure, while providing easy access from any device Â something we expect as standard today. ÂWe are proud to be the first company to give customers complete flexibility and choice in migrating their classic systems, either to the cloud or to the latest generation of on-premise servers,Â said John Prot, CEO of Stromasys. Stromasys is known for its Charon software, which has been used to emulate some of the older DEC systems on x86 hardware for the past 15 years. In Greek mythology, Charon was the ferry man whose task was to transport the dead across the river Styx to Hades, towards their afterlife. Of the 1990s RISC processors, Sun's Sparc and IBM's Power continue. Last week, Oracle reaffirmed its commitment to Sparc, with former CEO Larry Ellison singing praises to the upcoming Sparc M7 during his keynote at the Oracle OpenWorld conference. And IBM has launched the first new Power-based servers since handing management of the architecture to the OpenPower Consortium.

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Re: [math-fun] FullSimplify embarrassment contest
by Bill Gosper 08 Oct '14

08 Oct '14

MKleber> On Tue, Oct 7, 2014 at 1:14 AM, Bill Gosper <billgosper(a)gmail.com> wrote: Out[520]= 1/4 Sqrt[(a + b - c) (a - b + c) (-a + b + c) (a + b + c)] --rwg Side issue (Attention eavesdropping kids!): Given %520, how do you define Heron[a_,b_,c_], short of copying and pasting (which may not always be possible)? I'm guessing your solution doesn't create a value Heron[a_,b_,c_]:=1/4 ... , so you won't be able to reexecute the definition when you reload the notebook. How do you get an executable definition? No wonder everybody just copies and pastes! Heron[A_,B_,C_] := %520 /. {a->A,b->B,c->C} --Michael -- Forewarned is worth an octopus in the bush. ----- Interesting that you can't just say Heron[a_,b_,c_]:=%520 But your solution only lasts as long as %520 remains thus defined. How do we incorporate the actual radical into the body of Heron? And how do we get it as re-executable text? --rwg

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[math-fun] Logic in (old) pop music
by James Propp 07 Oct '14

07 Oct '14

Did anyone else notice, way back when, that the Beatles' affirmatory-sounding proclamation "There's nothing you can do that can't be done" is actually a tautology? Or that the Monkees' claim that "We're too busy singing to put anybody down", by slyly jabbing at the band's detractors, *was* in fact putting them down? Just wondering... Jim Propp

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Re: [math-fun] math-fun Digest, Vol 140, Issue 10, --- Logic in (old) pop music (Jim Propp)
by Stuart Anderson 07 Oct '14

07 Oct '14

> > t’s not unusual for retirees to have eccentric hobbies, but Bournemouth, > England’s Derek and Wilf <http://www.wilfturnbull.co.uk/> are probably > the only two old age pensioners who spend their free time dissecting rock > and pop lyrics and sending garrulous letters to the offending songwriters. Their > letter writing campaign began at a DJ’ed wedding, where they started > criticizing the songs being played. Their questions involve taking > whimsical or deadly earnest lyrics to their logical conclusions and > wondering the imponderable like why hungry like a wolf *in particular?* Why > not a penguin? *Or a raven?* Why would someone choose to live in a box > voluntarily? How does someone extract the milk of human kindness, *let > alone deliver it?* To their surprise, the musicians started responding. http://dangerousminds.net/comments/dear_gary_numan_two_old_geezers Stuart Anderson > > > Message: 5 > Date: Tue, 7 Oct 2014 13:47:25 -0400 > From: James Propp <jamespropp(a)gmail.com> > To: math-fun <math-fun(a)mailman.xmission.com> > Subject: [math-fun] Logic in (old) pop music > Message-ID: > < > CA+G9J-eZSd0DAuB-W-5pO0sjk-DAoQfS-WXsqF49qykNDTnBuA(a)mail.gmail.com> > Content-Type: text/plain; charset=UTF-8 > > Did anyone else notice, way back when, that the Beatles' > affirmatory-sounding proclamation "There's nothing you can do that can't be > done" is actually a tautology? > > Or that the Monkees' claim that "We're too busy singing to put anybody > down", by slyly jabbing at the band's detractors, *was* in fact putting > them down? > > Just wondering... > > Jim Propp > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > math-fun mailing list > math-fun(a)mailman.xmission.com > https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun > > > ------------------------------ > > End of math-fun Digest, Vol 140, Issue 10 > ***************************************** >

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