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Dario Izzo

Optimal Control Probem in the CR3BP solved!!! - 7 views

math.u-bourgogne.fr/...research

OCP CR3BP trajectory MAD

shared by Dario Izzo on 07 Jun 11 - No Cached
  • Dario Izzo on 07 Jun 11
     
    This guy solved a problem many people are trying to solve!!! The optimal control problem for the three body problem (restricted, circular) can be solved using continuation of the secondary gravity parameter and some clever adaptation of the boundary conditions!! His presentation was an eye opener ... making the work of many pretty useless now :)
  • ...13 more comments...
  • Ma Ru on 08 Jun 11
     
    Riemann hypothesis should be next... Which paper on the linked website is this exactly?
  • Joris _ on 08 Jun 11
     
    hmmm, last year at the AIAA conference in Toronto I presented a continuation approach to design a DRO (three-body problem). Nothing new here unfortunately. I know the work of Caillau, although interesting what is presented was solved 10 years ago by others. The interest of his work is not in the applications (CR3BP), but in the research of particular regularity conditions that unfortunately make the problem limited practically. Look also at the work of Mingotti, Russel, Topputo and other for the (C)RTBP. Smart-One inspired a bunch of researchers :)
  • Dario Izzo on 08 Jun 11
     
    Topputo and some of the others 'inspired' researchers you mention are actually here at the conference and they are all quite depressed :) Caillau really solves the problem: as a one single phase transfer, no tricks, no misconvergence, in general and using none of the usual cheats. What was produced so far by other were only local solutions valid for the particular case considered. In any case I will give him your paper, so that he knows he is working on already solved stuff :)
  • Dario Izzo on 08 Jun 11
     
    Answer to Marek: the paper you may look at is: Discrete and differential homotopy in circular restricted three-body control
  • Joris _ on 08 Jun 11
     
    Ah! with one single phase and a first order method then it is amazing (but it is still just the very particular CRTBP case). The trick is however the homotopy map he selected! Why this one? Any conjugate point? Did I misunderstood the title ? I solved in one phase with second order methods for the less restrictive problem RTBP or simply 3-body... but as a strict answer to your title the problem has been solved before. Nota: In "Russell, R. P., "Primer Vector Theory Applied to Global Low-Thrust Trade Studies," JGCD, Vol. 30, No. 2", he does solve the RTBP with a first order method in one phase.
  • Joris _ on 08 Jun 11
     
    I think what is interesting is not what he solved, but how he solved the problem. But, are means more important than end ... I dunno
  • Dario Izzo on 08 Jun 11
     
    I also loved his method, and it looked to me that is far more general than the CRTBP. As for the title of this post, OK maybe it is an exageration as it suggests that no solution was ever given before, on the other end, as Marek would say "come on guys!!!!!"
  • Joris _ on 09 Jun 11
     
    The generality has to be checked. Don't you think his choice of mapping is too specific? he doesn't really demonstrate it works better than other. In addition, the minimum time choice make the problem very regular (i guess you've experienced that solving min time is much easier than mass max, optimality-wise). There is still a long way before maximum mass+RTBP, Topputo et al should be re-assured :p Did you give him my paper, he may find it interesting since I mention the homotopy on mu but for max mass:)
  • Dario Izzo on 09 Jun 11
     
    Joris, that is the point I was excited abut, at the conference HE DID present solutions to the maximum mass problem!! One phase, from LEO to an orbit around the moon .. amazing :) You will find his presentation on line.... (according to the organizers) I gave him the reference to you paper anyway, but no pdf though as you did not upload it on our web pages and I could not find it in the web. So I gave him some bibliography I had with be from the russians, and from Russell, Petropoulos and Howell, As far as I know these are the only ones that can hope to compete with this guy!!
  • Joris _ on 09 Jun 11
     
    for info only, my phd, in one phase: http://pdf.aiaa.org/preview/CDReadyMAST08_1856/PV2008_7363.pdf I prefered Mars than the dead rock Moon though!
  • Dario Izzo on 09 Jun 11
     
    If you send me the pdf I can give it to the guy .. the link you gave contains only the first page ... (I have no access till monday to the AIAA thingy)
  • LeopoldS on 11 Jun 11
     
    this is why I like this Diigo thingy so much more than delicious ...
  • tvinko on 17 Jun 11
     
    What do you mean by this comment, Leopold? ;-) Jokes apart: I am following the Diigo thingy with Google Reader (rss). Obviously, I am getting the new postings. But if someone later on adds a comment to a post, then I can miss it, because the rss doesn't get updated. Not that it's a big problem, but do you guys have a better solution for this? How are you following these comments? (I know that if you have commented an entry, then you get the later updates in email.) (For example, in google reader I can see only the first 5 comments in this entry.)
  • LeopoldS on 18 Jun 11
     
    I like when there are discussions evolving around entries
  • LeopoldS on 18 Jun 11
     
    and on your problem with the RSS Tamas: its the same for me, you get the comments only for entries that you have posted or that you have commented on ...
Juxi Leitner

Asteroid Response System in Place (Complete With U.S. Military Eye Patch) - 1 views

www.dailygalaxy.com/...ith-us-military-eye-patch.html

space security asteroid response system telescope tech

shared by Juxi Leitner on 29 Jun 10 - Cached
LeopoldS liked it
  • However, the US air force, which funded the development of the telescope, requires that software automatically black out a swathe of pixels to hide the trajectories of passing satellites.
Juxi Leitner

How I became a Foursquare cyberstalker | Technology | The Guardian - 0 views

www.guardian.co.uk/...foursquare

tech technology INF fun privacy geo location social networks

shared by Juxi Leitner on 23 Jul 10 - Cached
  • Foursquare is now being widely touted as the app which will, after years of anticipation and prediction, mark the beginning of "life as a game" computing. Whatever you do, wherever you go, you will be scoring points, earning "medals", and be in, at the very least, social competition with other users around you.
  • Privacy seems to be very low down their priorities. In theory, if every user knows the risks, this is fine. But they just don't. It's being targeted at 18 to 25-year-olds. Facebook was forced in the end to change its default privacy settings due to public concerns. Foursquare should do the same. Some people are even checking in when they're at home. Think of the implications. It's crazy
  • Recruitment is a form of stalking, I suppose. But I can now see the negative implications of Foursquare in the real world.
  • ...1 more annotation...
  • Ten days ago Foursquare reached the two-million-users landmark, just three months after it had reached the one-million mark. A week earlier, the company received $20m in venture capital from a who's who of Silicon Valley luminaries. It appears the trajectory for Foursquare is only upwards. But as the critical mass of Foursquare users swells and intensifies over the coming months and years, the concerns over privacy are likely to magnify. In June, Webroot, a Denver-based internet security firm, surveyed 1,645 users of "geo-location-ready mobile devices", including 624 in the UK: 29% said they shared their location with people other than their friends; 31% said they accepted a friend request from a stranger; and, yet, 55% still said they were worried about their loss of privacy.
  • Juxi Leitner on 23 Jul 10
     
    anybody here using Foursquare already? Location is supposed to be "the future" (this time)
  • LeopoldS on 24 Jul 10
     
    this is worse than having a mobile ... !
LeopoldS

Non-equilibrium trajectory dynamics and the kinematics of gliding in a flying snake - 2 views

iopscience.iop.org/...045002

BIO technology science PHY

shared by LeopoldS on 27 Nov 10 - No Cached
  • LeopoldS on 27 Nov 10
     
    nice study ... flying snakes
pacome delva

3D invisibility cloak unveiled - physicsworld.com - 1 views

physicsworld.com/...42043

transformation_optics cloaking

shared by pacome delva on 29 Mar 10 - Cached
  • For Wegener the aim of the work is not about focusing all efforts on creating invisibility cloaks, but is about exploring a range of applications in transformation optics. This involves calculating what kind of material is needed to bend light in a certain way, by considering light trajectories as the result of the warping of space. Wegener says that transformation optics should lead, for example, to the design of better antennas or smaller optical resonators.
  • Luzi Bergamin on 29 Mar 10
     
    We don't have Science Express subscription here, so I have to wait till the normal paper is out. From what I heard about it, I doubt that this would have made it to Science without the names Pendry and Wegener in the autor list! Certainly, they are two of the smartest guys in Metamaterials, but they are also two of the absolut class A sellers. Pendry by definition is the first in whatever (at least in HIS talks...) but apart from this he's a very nice guy. Better let's not try to characterize Wegener...
santecarloni

[1106.1470] Evidence for Time-Varying Nuclear Decay Rates: Experimental Results and The... - 2 views

arxiv.org/1106.1470

phy technology

shared by santecarloni on 13 Jun 11 - No Cached
LeopoldS liked it
  • santecarloni on 13 Jun 11
     
    Unexplained annual variations in nuclear decay rates have been reported in recent years by a number of groups. We show that data from these experiments exhibit not only variations in time related to Earth-Sun distance, but also periodicities attributable to solar rotation. Additionally, anomalous decay rates coincident in time with a series of solar flares in December 2006 also point to a solar influence on nuclear decay rates....
  • LeopoldS on 13 Jun 11
     
    can we use space to make a smart experiment to solve this riddle? e.g. sending a decay detecter on a close solar orbit and one to Pluto and then compare decay rates? or a highly elliptical trajectory and compare during peri and apoapsis?
  • santecarloni on 13 Jun 11
     
    I think it could be possible. I need to look into the details. In fact it could probably be done already with the nuclear generators on the Voyager and Pioneer and other nuclear powered probes. That is if the data are precise enough...
Joris _

Space travel without fuel is no pipe dream - World News, Frontpage - Independent.ie - 0 views

www.independent.ie/...-is-no-pipe-dream-1884120.html

MAD space trajectory

shared by Joris _ on 14 Sep 09 - Cached
  • Joris _ on 14 Sep 09
     
    super-highways: an old stuff, but still very fascinating ...
Luís F. Simões

Speeding swarms of sensor robots - 2 views

web.mit.edu/...robot-algorithm-0503.html

robotics swarm sensorweb AI

shared by Luís F. Simões on 04 May 11 - No Cached
LeopoldS liked it
  • the algorithm is designed for robots that will be monitoring an environment for long periods of time, tracing the same routes over and over. It assumes that the data of interest — temperature, the concentration of chemicals, the presence of organisms — fluctuate at different rates in different parts of the environment.
  • But it turns out to be a monstrously complex calculation. “It’s very hard to come up with a mathematical proof that you can really optimize the acquired knowledge,”
  • The new algorithm then determines a trajectory for the sensor that will maximize the amount of data it collects in high-priority regions, without neglecting lower-priority regions.
  • ...1 more annotation...
  • At the moment, the algorithm depends on either some antecedent estimate of rates of change for an environment or researchers’ prioritization of regions. But in principle, a robotic sensor should be able to deduce rates of change from its own measurements, and the MIT researchers are currently working to modify the algorithm so that it can revise its own computations in light of new evidence. “
  • LeopoldS on 05 May 11
     
    smart!
jcunha

Space data representation - 1 views

phys.org/...-universal-language-space.html

PHY technology

shared by jcunha on 13 Apr 15 - No Cached
  • jcunha on 13 Apr 15
     
    A common data hub that allows the representation and comparison of data from numerous space missions. "The IMPEx portal offers tools for the visualization and analysis of datasets from different space missions. Furthermore, several computational model databases are feeding into the environment." As they say, with its massive 3D-visualization capabilities it offers the possibility of displaying spacecraft trajectories, planetary ephemerides as well as scientific representations of observational and simulation datasets.
jaihobah

An AI physicist can derive the natural laws of imagined universes - 1 views

www.technologyreview.com/...ral-laws-of-imagined-universes

PHY AI

shared by jaihobah on 01 Nov 18 - No Cached
  • dharmeshtailor on 01 Nov 18
     
    I'm afraid I take some issue with this rather glorious title. I've only skimmed this paper but looking at the experimental details, their 'imagined universes' comprise of a ball confined in a 2D space as well as a double pendulum. Work along this area is nothing new - it's known in the control community as Inverse Reinforcement Learning - learning dynamics of some system from demonstration trajectories. The paper title ('Toward an AI Physicist for Unsupervised Learning') is more moderate so yet again the issue is how AI is reported in the media...
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