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Drone Sightings Near Other Aircraft Up Dramatically

joe_frisch Re:These idiots are going to ruin it for everyone (132 comments)

Maybe this suggests a technical solution.
Equip drones with GPS and nav databases so that they will not fly in controlled airspace. (with the ability to override with some sort of approval).

There are flights in uncontrolled airspace but it is much less of an issue.

about two weeks ago
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New Particle Collider Is One Foot Long

joe_frisch Re:SLAC FACET accelerator (161 comments)

Unfortunately for ion drives you want high current but very low energy. The amount of electric power required by an ion drive increases as the exhaust velocity increases, and for present day space applications you are better off with less particle energy, not more.

about three weeks ago
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New Particle Collider Is One Foot Long

joe_frisch Re:Not exactly (161 comments)

Its a good question .
I don't understand astrophysical shocks, but see: http://www.slac.stanford.edu/e...
As far as I can tell the rely on magnetic fields bending the particles back into the shock.

When relativistic particle trajectories are bent by magnetic fields, they emit synchrotron radiation which increases rapidly with increasing particle energy.

Longitudinal fields don't do the same thing. There is a tiny amount of radiation, but it is not strongly dependent on particle energy. I believe this is because Lorentz contraction increases transverse, but not longitudinal electromagnetic fields: http://en.wikipedia.org/wiki/C...

Ideally the fields in the plasma accelerator are longitudinal on axis. If the particle enters slightly off axis it will get a transverse kick and will radiate synchrotron radiation, and we do see that. For very high energies that radiation might be large, but the effect would be to damp the transverse motion of the particle, but not affect the longitudinal acceleration.

  I know that the plasma wakefield people are seriously thinking about TeV scale machines: https://accelconf.web.cern.ch/...

It is possible that the concept fails at some much higher energy.

about three weeks ago
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New Particle Collider Is One Foot Long

joe_frisch Re:SLAC FACET accelerator (161 comments)

That is a slightly different concept. This uses a medium-energy (20GeV), high current electron beam to drive the plasma, which then accelerates a high energy beam.

There is also a scheme to use a high energy proton beam to drive the plasma, and a scheme to use a high power (Peta-watt) laser to drive the plasma.

All are being seriously considered / developed by various laboratories.

This type of scheme probably doesn't apply well to a circular machine like LHC because the energy limit there is the magnets used to bend the beam into a ring .You might accelerate the protons at the end, but you wouldn't be able to send them back for re-use and you would not get enough collisions to get interesting physics.

about three weeks ago
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New Particle Collider Is One Foot Long

joe_frisch Re:Not exactly (161 comments)

If you do everything right, you should get the same added energy from each section. So a 10 GeV input beam woudl go to 11.6, and a 1000 GeV beam would go to 1001.6. The beams are ultra-relativistic - for all practical purposes speed of light (off by only a part in a billion) and this acceleration mechanism doesn't depend on the beam energy .

about three weeks ago
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New Particle Collider Is One Foot Long

joe_frisch Re:Not exactly (161 comments)

Yes - in principal. You will need a separate bunch of 20 GeV drive electrons for each section, but that is not very difficult to do with a single accelerator. You need to separate the waste beam from the previous stage and the magnetic system to do that may be inconveniently long unless there is a beam-optics trick (which there may be).

Staging two sections together is on the list of things that they are going to try. The eventual goal is to put together a lot of stages to get to TeV scale energies.

about three weeks ago
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New Particle Collider Is One Foot Long

joe_frisch Re:Not exactly (161 comments)

If you do a Google search on

SLAC PUB plasma wakefield
you will find a lot of non-paywalled papers on this and related plasma accelerator experiments at SLAC.

about three weeks ago
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New Particle Collider Is One Foot Long

joe_frisch SLAC FACET accelerator (161 comments)

I am peripherally involved in the SLAC plasma wakefield accelerator described in the article.

It provides a very high energy gain in a short distance, but needs to be driven by a high energy drive beam. The present design uses a 20GeV drive beam (using part of the old high energy physics accelerator).The required drive beam energy could be reduced to ~10GeV but probably not a whole lot lower. So this is a way to build a relatively short very high energy accelerator, but not a way to build a very short low-medium energy machine.

Other labs are working on laser driven plasma accelerators that do not need to start with a high energy beam, but do need an enormous laser system and are presently limited to much lower average beam powers .

Plasmas are very promising for future accelerators and there was some excellent work done at SLAC as well as laser / plasma accelerators at other labs. There is still a lot to do. There are issues with staging multiple plasma cells to get high energies, beam quality and stability issues etc.

about three weeks ago
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Space Tourism Isn't Worth Dying For

joe_frisch Re: Well (594 comments)

We know how to put people in space and have been doing so for over half a century - spaceship2 is not doing anything new. The comparison with very early engines and engine driven vehicles is really not appropriate. The largest problem is that it has been very expensive to put people in space. Does spaceship2 address that problem? (there is also a very real safety issue, but presumably that would get better if the volume of space travel increased).

Spaceship2 uses air launch, and a conventional but low delta-v rocket to do a parabolic flight. Air launch has been used on small rockets before but is very difficult for manned missions because of the enormous fuel weight required to get a manned craft into orbit. Spaceship2 doesn't address this issue because it doesn't attempt orbital speeds and so can be very light weight.

Spaceship2 does not need to deal with significant reentry heating so its high drag mode doesn't really apply to a "real" reentry.

So I don't see any clear use of the spaceship2 technologies to "real" space vehicles.

That said, it is somewhat mysterious why space is so expensive. The fuel costs are 1% of the total launch costs, it is is not a fundamental "energy is expensive" problem. Presumably the cost is related to the combination of very low volume production and very difficult design issues. It is possible that the spaceship2 program would be able to address some of those issues, but I have not seen any discussion of specifics.

"Space planes" seem about as practical as "air ships" and "flying cars".

about three weeks ago
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LAX To London Flight Delayed Over "Al-Quida" Wi-Fi Name

joe_frisch Re:A Pox on Both Your Houses (339 comments)

I know terrorists aren't the brightest bulbs in the chandelier but they know enough not to name their networks after a famous terrorist group. What exactly is the threat that caused the delay?

A "few hours" X 400 passengers IS a big deal - and delayed flights mean missed connections, The aircraft my not be available for its next schedule flight etc.

about a month ago
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What Will It Take To Make Automated Vehicles Legal In the US?

joe_frisch Re:For Starters (320 comments)

The compelling reason is that self-driving cars could free up tens of billions of man-hours a year in the US alone. People could use the time they spend in cars for entertainment or productivity. It would be one of the truly great labor saving inventions.

For that to work though, the car would need to be truly autonomous and that gets into tricky legal issues.

about 1 month ago
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How To Beat Online Price Discrimination

joe_frisch Re:No Haggle ! (163 comments)

Agreed, and the problem with haggling is that it takes time. If I buy a $300 piece of electronics, it is not efficient for me to spend $100 of my time to reduce the price by $50. Unfortunately if it is possible to track individual purchasers habits, vendors can continue to increase the prices those consumers see until they are essentially forced to waste time price comparing.

Of course it won't be an "increase", Instead the "list" price will be $1000, and people will get varying discounts depending on how much price comparing they do. People who compare a lot, must not value their own time, and are more likely to only accept a low price. People who don't compare probably place a high value on their time and are willing to pay more.

This has the positive effect of effectively reducing wealth disparity, but the very large negative effect of providing an incentive for people to spend a large amount of time in a non-productive activity (price comparing). Its great for vendors, but bad for the overall efficiency of the economy.

about a month ago
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Decades-old Scientific Paper May Hold Clues To Dark Matter

joe_frisch Re:And they saw nothing (93 comments)

Yes, by not seeing something under know conditions, you can rule out some possibilities. If the particles had properties withing a certain range they would have shown up in this experiment - since they did not, we know that the particles do not have properties in that range (assuming the experiment was done correctly).

This sort of null experiment is common in many types of science.

about a month ago
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The One App You Need On Your Resume If You Want a Job At Google

joe_frisch Re:Octave (205 comments)

Why is matlab on a cluster stupid? It has some parallel tools that work well for certain types of jobs.

about a month ago
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The One App You Need On Your Resume If You Want a Job At Google

joe_frisch Re:Python (205 comments)

I use Matlab and Python at work. They are good for different things.
IMHO matlab has much more powerful graphics and debugging features. It is better set up for doing vector algebra problems. Python is better for some other forms of non-mathematical data operations. For most of my work Matlab is the better tool. On the windows platform it is much easier to install and manage .

We run the SLAC accelerators using both for analysis and non-realtime feedback, but Matlab is generally the preferred tool by most of the physicists.

Talking about which is better is like asking if a Semi-truck or a bus is a better vehicle. It all depends on what you are trying to move .

You can solve any problem in either of them (or in C, or fortran or COBOL if you really want), its just a case of which tool is better for the types of problems you are solving.

about a month ago
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FBI Director Continues His Campaign Against Encryption

joe_frisch I feel pretty safe (284 comments)

Seriously. By a large margin I am most likely to die due to an age related illness.Somewhere after that are non-age related illnesses. Then accidents.Then Suicide. Being killed by "bad people" is WAY down the list. Why on earth should I give up my rights to protect myself from a tiny chance of death?

Obviously people in power would like more control over me, but why should I agree to it?

about a month and a half ago
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When will the first successful manned Mars mission happen?

joe_frisch We no longer do things because they are hard (219 comments)

We could go to mars. Build colonies, expand into the universe. It would be very hard and very expensive and take centuries, and all we would get in return would be... everything.

 

about a month and a half ago
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Wind Power Is Cheaper Than Coal, Leaked Report Shows

joe_frisch Re:Diseconomies (610 comments)

Economics has the concept of "externalities" - basically effects of an activity that are not captured in its production costs. These can be negative (like pollution) or positive (like increasing productivity from a transit system).

One of the primary jobs of governments is to help correct the effects of externalities through regulation and taxes. The particular problem here is that the externalities (for CO2) are global, but the governments are local. This makes proper taxation / regulation difficult. If a government taxes industry to account for global pollution, but if other governments do not, that will tend to drive industry to non-regulated and likely dirtier locations (resulting in MORE pollution not less). It may be possible to fix this with import taxes on these goods, but that gets into the very difficult and political world of international trade regulations.

Not saying it can't be done, but its tricky.

about a month and a half ago
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VeraCrypt Is the New TrueCrypt -- and It's Better

joe_frisch Re:Nope not suspicious at all (220 comments)

That is EXACTLY the problem. Determining a chain of trust is tricky. Producing a chain of trust that a non-expert can trust is almost impossible. Most users cannot verify the algorithms themselves so they have to rely on the evaluation of other people. But, how to trust those other people?

Government organizations have the resources to flood discussion groups like this with reasonable-sounding statements about how well something has been verified, while discrediting anyone who posts an message disagreeing.

If someone posts that I am wrong, how can I, or any non-expert know if the arguments against this post are valid?

about a month and a half ago
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Independent Researchers Test Rossi's Alleged Cold Fusion Device For 32 Days

joe_frisch Re:Any suffiently advanced tech... (986 comments)

There are too many ways for this result to be wrong.

As many have pointed out an open-air calorimeter is the wrong way to measure heat. Any competent experimental scientist would know this. Its very easy to get this wrong by a big factor.

A very big problem is that the "dummy reactor" was operated at low power .(500W). since the thermal emisssion and convection are nonlinear, this is a very poor way to do a calibration. The excuse:

". In fact, it is well known that some Inconel cables have a crystalline structure that is modified by temperature, and are capable of withstanding high currents only if they are operated at the appropriate temperature"

Is VERY thin. If true it simply means that the dummy reactor is not an appropriate calibration. Again a competent experimental scientists would know this.

Then if it is intentional fraud, there are a LOT of ways to sneak power into the system. We are only talking a couple of KW of output - you can hide a wire carrying a couple of amps at a KV very easily. Also if there is a possibility of fraud you need to check EVERYTHING. Is the mains voltage what is claimed? Did the experimenters provide all of their own test equipment - thermal cameras, voltmeters etc. Is the lab locked and sealed from any possible entry? Are there hidden wires or fuel lines inside of the test apparatus?

The combination of poor experimental technique, lack of a physical model for fusion without radiation, and the huge financial motivation make it extremely unlikely that this is real. Whether it is outright fraud or misunderstanding is not clear.

about a month and a half ago

Submissions

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Ask Slashdot: Computers for the elderly

joe_frisch joe_frisch writes  |  more than 2 years ago

joe_frisch (1366229) writes "There is a growing group of elderly computer users who have learned to be productive with a particular interface, say windows XP and office 2003, and who do not have the interest or energy to learn something new like Windows 7 or the office "ribbon". They continue to use aging and unreliable computers because they do not know how to order new computers with the older interface. Many of these users are relatively wealthy so this is potentially a valuable market.

While it it possible to cobble something together, with time it becomes increasingly difficult, especially for the often minimally computer-literate people in this market. In addition, as older software is no longer supported it will be increasingly susceptible to viruses. What would be ideal is a old style interface to updated programs and operating systems.

What are the options — and remember the target market is NOT people who read slashdot, suggesting that they use Debian is not going to work."

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