Group items matching

in title, tags, annotations or url

Did you know about this Weather Modification Office? Promising or dodgy?

Yes. In China it happens apparently quite often that weather is regionally modified, e.g. in order to have good weather conditions during certain events (like olympics in Beijing). But also in other countries weather modification is applied, for reasons of agriculture, pollution, skiing, etc. Obviously, one wonders on the environmental impact of such an artificial cloud feeding process with silver iodide. I just googled, stumbling upon this report http://www.weathermodification.org/AGI_toxicity.pdf which published the result: no environmentally harmful effects...

and w.r.t. ur question: I mean different weather conditions which we experience locally (like droughts or other extreme weather events) are (often) due to large-scale/global climatic changes. Hence, cloud seeding just describes a local, short-term mitigation of these events. However, there is a geoengineering proposal (so climate modification) which also suggests to seed clouds above the sea (i.e. increase cloud coverage, e.g. by using seaspray as cloud condesation nuclei), thereby increasing the planetary albedo (Earth reflectance) and reducing the energy reaching the Earth surface. If this idea is promising or not, I couldn't judge upon, but for sure it is worthwhile to take a closer look at.

This is the guy of Luzy's joke: "Dear, this is not what it seems. I can explain EVERYTHING!"

yeah an interesting theory, definitely worth following. But it is far from being mature, and a lot of work remains before saying that it is viable or not... I posted something on this some time ago (http://www.diigo.com/user/pacome/horava_theory) and proposed to do smthing on it in the idea storm (our new creative game...), which didn't have a lot of success... I like also the idea of matrix gravity (see Matrix general relativity: a new look at old problems, Ivan G Avramidi, CQG 21, 103)

you are among what???

A good example of how loosing perspective makes so-called "novel ways" actually "rubish ways"

here the paper: http://arxiv.org/abs/1104.1401 well spent defence funding ....

for Tobi! nice analogy between the threat and the fast responding in human network

Yet another example of "because scientifically accurate title would sound sooo boring".

Tokyo has a very large population and one of the smallest crime rates in the world, in fact Tokyo is known to be the safest big city in the world (w.r.t. crime). It is hard to believe that the crime rate in L.A. is in the same order of magnitude.

The Economist this week has a 14-page special on the rise of the robots. Don't expect a very indepth technical review but an interesting read nonetheless for some maybe.

This article nailed the issue, as far as I'm concerned. By the way the diagram in the Economist is hilarious.. amazing combination of American and male chauvinism!

At a meeting of the American Geophysical Union in San Francisco in December, he reported an average figure that was between 0.005 and 0.008 per cent greater than the value for Earth's mass established by the International Astronomical Union. A disc of dark matter around the equator 191 kilometres thick and 70,000 km across can explain this, he says. Harris has yet to account for perturbations to the satellites' orbits due to relativity, and the gravitational pull of the sun and moon. Maybe relativistic GPS could improve this even further? As a side note however, the Juno spacecraft flyby showed an gravity acceleration which matched the calculations, casting doubts on the earlier calculations.

Theoretized 80 years ago was Breit-Wheeler pair production in which two photons result in an electron-positron pair (via a virtual electron). It is a relatively simple Feynmann diagram, but the problem is/was how to produce in practice a high energy photon-photon collider... The collider experiment that the scientists have proposed involves two key steps. First, the scientists would use an extremely powerful high-intensity laser to speed up electrons to just below the speed of light. They would then fire these electrons into a slab of gold to create a beam of photons a billion times more energetic than visible light. The next stage of the experiment involves a tiny gold can called a hohlraum (German for 'empty room'). Scientists would fire a high-energy laser at the inner surface of this gold can, to create a thermal radiation field, generating light similar to the light emitted by stars. They would then direct the photon beam from the first stage of the experiment through the centre of the can, causing the photons from the two sources to collide and form electrons and positrons. It would then be possible to detect the formation of the electrons and positrons when they exited the can. Now this is a good experiment... :)

True, but isnt it E2=(pc)^2 + (m0c^2)^2 such that for photons E\propto{pc} and for mass E\propto{mc^2}. I agree it will take a lot of energy, but this assumes that that wont be the problem at least. The question therefore is whether the mass flow of the photon rocket (fuel consumed to create photons, eg fission/fusion) is higher/lower than the mass flow for e-p creation. You are probably right that the low e-p cross-section will favour direct use of photons to create low thrust for long periods of time, but with significant power available the ISP might be higher for e-p pair creation.

In essence the equation tells you that for photons with zero rest mass m0 all the energy will be converted to momentum of the particles. If you want to accelerate e-p then you first spend part of the energy on creating them (~511 keV each) and you can only use the remaining energy to accelerate them. In this case the equation gives you a lower particle momentum which leads to lower thrust (even when assuming 100% acceleration efficiency). ISP is a tricky concept in this case because there are different definitions which clash in the relativistic context (due to the concept of mass flow). R. Tinder gets to a I_SP = c (speed of light) for a photon rocket (using the relativistic mass of the photons) which is the maximum possible relativistic I_SP: http://goo.gl/Zz5gyC .

Recently, it was shown that slowly rotating neutron stars exhibit an interesting correlation between their moment of inertia I, their quadrupole moment Q, and their tidal deformation Love number λ (the I-Love-Q relations), independently of the equation of state of the compact object. By exploiting this relation, we can describe quite accurately the geometry around a neutron star with fewer parameters, even if we don't know precisely the equation of state. Side note: I-Love-Q relations? Some inner chuckles in the Fundamental Physicist community.. :)

Other possible study: get a textbook example of an image of a pen, evolve it just enough so NN can't recognize it anymore, while minimizing the distance between the original and evolved images. EDIT: Its been done already: http://cs.nyu.edu/~zaremba/docs/understanding.pdf

Of course, you can't really use them to extrapolate. The unknown unknown is always the trickiest :P They should just make another class "random bullshit", really and dump all of this stuff in there. I think there's a potential paper right there

A personal interest of mine that I want to explore a bit more in the future. I just bought a ZigBee electricity monitor and I am wondering whether from the signal of the mains one could detect (reliably) the oven turning on, lights, etc. Probably requires Neural Network training. The idea would be to make a simple device which basically saves you money by telling you how much electricity you are wasting. Then again, its probably already done by Google...

Randomly I found this: http://spectrum.ieee.org/view-from-the-valley/consumer-electronics/gadgets/curb-startup-home-electricity-tracking Isn't it a similar kind of stuff Thijs?

haha, yep, that's it... but we can do better than that right! :)

In a work published on Nature (http://www.nature.com/nature/journal/v517/n7536/full/nature14090.html#affil-auth) a new DFT based simulation of convection in Earth's Core iron shows that electron-electron scattering has a similar contribution to electron's thermal vibration. The outcome is that using the old dynamo theory the simulation matches the Earth magnetic field experimental results, solving an 80 years old puzzle.

Yay to science! I'm always intrigued by related experiments that try to measure material properties at the GPa range. Especially, the efforts of reaching 'metallic hydrogen' (http://en.wikipedia.org/wiki/Metallic_hydrogen), requiring pressures above 25GPa at which hydrogen becomes conductive. It is thought that gas giant planets could have such a core, but no-one has been able to produce/verify this theory as off yet.

Mitsubishi Heavy Industries said Friday that it has succeeded in transmitting 10 kW of power through 500 m. An announcement that comes just after JAXA scientists reported one more breakthrough in the quest for Space Solar Power Systems (http://phys.org/news/2015-03-japan-space-scientists-wireless-energy.html). One step closer to Power Generation from Space/

from the press release (https://www.mhi-global.com/news/story/1503121879.html) "10 kilowatts (kW) of power was sent from a transmitting unit by microwave. The reception of power was confirmed at a receiver unit located at a distance of 500 meters (m) away by the illumination of LED lights, using part of power transmitted". So 10kW of transmission to light a few efficient LED lights??? In a 2011 report (https://www.mhi-global.com/company/technology/review/pdf/e484/e484017.pdf), MHI estimated this would generate the same electricity output as a 400-megawatt thermal plant - or enough to serve more than 150,000 homes during peak hours. The price? The same as publicly supplied power, according to its calculations. There are no results to boost these claims however. The main work they do now is focused on beam steering control. I guess the real application in mind is more targeted to terrestrial applications, eg wireless highway charging (http://www.bbc.com/future/story/20120312-wireless-highway-to-charge-cars). With the distances so much shorter, leading to much smaller antenna's and rectenna's this makes much more sense to me to develop.

Today we released the Astro Drone app. People that have the Parrot AR drone can freely download the game. While they fly their drone in the real world, they are trying to dock to the ISS in the virtual world. But the app is more than a game. Players can choose to participate in a scientific crowd sourcing experiment that aims to improve autonomous capabilities of space probes, such as landing, obstacle avoidance, and docking. If participating, the app extracts visually salient features from the images made by the drone's camera. The features are then combined with the estimates of the drone's state and uploaded. The data is then used in a research aiming to improve robot navigation.

Visit the main ESA website and you'll be greeted with a 6-minute Rosetta promo movie by a kickass Polish artist... P.S. You can also find the video here. P.P.S It seems I've just discovered a way to hijack old diigo entries ;-)

is this the breaktrough that we were waiting for?

That depends on what application you are thinking of. For circuit board electronics this will allow integration of micro sized supercapacitors to provide operational power. They will have to be fed by external batteries still, but the close proximity allows for better tailored power demands. They also propose tapping into thermal/mechanical energy to charge the supercaps. In the end, they can provide significant specific power (W/kg) but you still need to upscale the production to cover large areas to also gain high specific energy (Wh/kg). This breakthough is for micro sized applications, not for replacement of large scale energy storage (electric vehicles, satellites) going up to kWh. That said, I know of several studies in supercaps at ESA, but they are still qualifying current relatively old commercial solutions.

Engineer Roger Shawyer's controversial EM Drive thruster jets back into relevancy this week, as a team of researchers at NASA's Eagleworks Laboratories recently completed yet another round of testing on the seemingly impossible tech.

I like this just because it will end up on Thijs' desk :D

Interesting that the new comes in... Yahoo Finance :). Another more complete article http://nextbigfuture.com/2015/11/nasa-eagleworks-has-tested-upgraded.html

Simulating the economic state of the Galaxy after the resistance has blown up the Death Stars. See the paper here: http://arxiv.org/pdf/1511.09054.pdf

Love this type of friday afternoon research questions. There is also a now famous scene in the movie Clerks discussing the loss of independent contractors lives as the Death Star was being build.. https://www.youtube.com/watch?v=iQdDRrcAOjA

That analysis is quite crappy and is easily demolished in the video's comments.

Genetic algorithms are a competitive alternative for training deep neural networks for reinforcement learning. For paper see: https://arxiv.org/pdf/1712.06567.pdf

Interesting pointers in this one! I would like to explore neuroevolution as well, although it seems extremely resource-demanding?

Not necessarily, I think it can be made to be much faster hybridizing it with backprop and Taylor maps. Its one ideas in the closet we still have not explored (Differential Intelligence: accelerating neuroevolution).