Follow Slashdot stories on Twitter


Forgot your password?

Comment Re:Can you buy these panels yourself? (Score 4, Informative) 176

Like this?

Point is, you need a panel. And you need a microinverter. And you need a wire to the roof. And you need a box, called a combiner box, the wire goes into. There is usually a cutoff switch on that box. Then, after that, the wire from the combiner box is usually backfed into your main breaker panel, with the power going backwards through an appropriate breaker rated for the wire's ampacity. Really, the tricky part is the power company has to come and approve the design and install their 2 way meter. Everything else, any idiot can do.

Comment Can you buy these panels yourself? (Score 1) 176

As other commentators have pointed out, the install prices these days, compared to the prices of the panels, are insane. The installations have gotten simpler than ever - with microinverters, you literally can go up there and install 1 panel per weekend as the system functions just fine with N number of panel/inverter modules installed. (as long as N is smaller than the number of panels that can fit on your roof)

Anyways, SunPower won't sell you the panels directly. I have seen them available online but only their scratch and dent models with no warranty.

Comment Re:Yes? And? (Score 0) 275

Allegedly, the Swedish government refuses to promise not to extradite him. That is supposedly what this is all about. All they have to do is promise this in writing and this whole spat gets resolved.

It is possible the reason they are not doing this is that Sweden plans to give him to the United States. It is more likely that as a government, they just don't care - the Swedish government doesn't have to sit in an embassy cell waiting. They don't have to cater to individuals, they can do whatever they want.

Comment Why no test (Score 1) 456

Send her into a Faraday cage. "sense anything, ma'am". If she says yes, experiment over. If she says now, have a cellphone or powerful RF transmitter inside an opaque box. turn it off and on.

If her guesses whether it is on are not are no better than chance, experiment over. If they are correct...well...that would be very interesting.

Comment Re:Is it really THAT hard? (Score 1) 168

I think you're basically right. I read about an even simpler system. They wanted to prove if a robotic surgical arm, controlled by a multi-axis joystick, would always no matter what move only when the surgeon commanded it.

So basically, you read the joystick position sensor for an axis. You multiply by a coefficient, usually less than 1. You send that number to the arm controller. Arm controller tries to move to that position.

Smooth, linear, no technically only need to check about 3 states (the edges and the middle) for a linear system without discontinuities. If it works, you're done. (for each axis so if it's 3 axis that's 27 states to check)

Somehow their system had bugs in it that they found with formal verification. Not sure how...

Comment Restating his argument (Score 1) 262

The good professor's arguments are asinine and deadly wrong. Retranslated, "I see no reason why you should be concerned about the dangers of a so called "atomic explosion". With the tiny amount of U-235 you have managed to isolate, you have barely managed to demonstrate more than the slightest bit of warmth resulting from radioactive decay. I see no reason to believe your extraordinary claims that it will detonate in a flash with the energy equivalent to thousands of tons of explosives"

The evidence that superintelligent AI is better than our evidence for nuclear fission in the 1940s. We know we are intelligent. We know you can build an intelligent machine with 86 billion neurons * 1000 interconnects. We know that our current neural hardware is thousands of time slower than the clock rates of trivially constructible digital circuits.

Today, our current efforts are tiny. Most advanced artificial neural network models only use 1000 or so connections, not the trillions we know it actually takes. We don't have the patterning for arranging those trillions of connections properly. Similarly, if you isolated a gram of U-235 by itself, it would seem harmless.

The theories in the 1940s knew it wasn't harmless, that putting enough of it in one place would lead to a chain reaction that would create nuclear driven heat. They eventually built, at great expense, the first reactors to test this.

Similarly, we know that the rate we think limits how fast we can invent and prepare new technology. We know that technology vastly better than what we have now is possible - machines that are constructed with careful thought atom by atom, that can self replicate and rearrange matter at an atomic level...

The professor's wrong, and is the same blithe ignorance as stating that it's totally ok with slam together those pieces of purified U-235 with no safety measures.

Comment Roughly, how did this happen? (Score 2) 173

I remember thinking in the 90s "no one would be stupid enough to put safety critical computer systems on a network at all..."

And, here we are.

If someone gave me a blank sheet of paper and asked me to sketch out the system for a car's braking controller, I'd slap down a CPLD or microcontroller, and have it use some locked firmware to read the various sensors and send out the control signals.

Oh, they want networking? I'd isolate or use the inherent properties of a CPLD/FPGA programmed in combinatorial logic style (you can program a CPLD/FPGA to act like a microcontroller instead which is vulnerable)

In combinatorial logic style, all the processing is through various gates, and is a boolean combination of flip flops and logic gates. So, say they want the ability to read(but not alter) the current state of the vehicle's brakes. A tiny communication processor (a low pin count PIC is one choice) would receive from the vehicle's CAN bus the command to give the vehicle's brake state. The communication processor would toggle high an outpin pin connected to an input pin on the microcontroller/CPLD that actually controls the brakes. That high pin state would mean that every few control loop cycles, the microcontroller/CPLD would blast out the current state on a serial output pin.

Note that there's no opportunity for a hacker who got into that communication processor to do any worse than toggle a pin on and off. No effect on the steering/braking.

Ok, maybe now we want to be able to change the "style" of steering and braking. So now there's a finite set of legal states that are stylistically desirable. That's when you'd isolate with the inherent property of an FPGA/CPLD state machine to not be capable of any other states BUT the states you defined. (there's no global memory and no stack, so nothing a hacker can do to affect the machine's behavior)

Comment Re:Yes, that's the claim of the prosecutor. (Score 1) 169

If between 6 and 13% of all men have committed a rape, what's your proposed solution? Lock up between 22 million and 48 million people?

What happens when you let them out? You've just created between 22 and 48 million people who are now on the sex offenders list and cannot get a job or reintegrate. What do you think they are going to do now?

Oh, so you want to kill them or lock them up for life? What do you think 22 to 48 million men will do when you come for them with the intention of giving them a sham trial and murdering them?

Comment Starship engines (Score 1) 576

If we reject the OPs "jumping in" and assume the statement is from a person who's watched too much sci-fi, what would we see as the alien fleet arrives?

Well, the first question is, what methods do we know of right now that could work for the alien's engines?

There are :

                        1. Nuclear salt water or nuclear pulse (orion drive)
                        2. Fission Fragment
                        3. Fusion
                        4. Black holes
                        5. Antimatter annihilation
                        6. Some kind of sci fi method to just release the rest mass as energy in ordinary matter without the antimatter needed.

Number 1 is some variant on a fission bomb propelling the ship. A couple percent of the speed of light, tops. Number 2 and 3 have the problem of pathetically low thrust although high isp. Black holes depends upon assumptions about a black hole that makes them movable (they have to be electrically chargeable) and constructible (you need solar system sized mass drivers to accelerate metal rods to slam into each other at a sliver below the speed of light to form the black hole). But, they are a near perfect form of engine - you feed the black hole a particle beam of ordinary matter, collected by ramscoop, and you get back gamma rays that your enormous ship reflects like a parabolic dish. Antimatter annihilation is similar to black holes except it requires you to carry all your antimatter with you, and it's immensely difficult to avoid blowing up the ship.

Anyways, all these methods have a common factor. All of them will release a flare of gamma rays as the alien fleet decelerates. The alien fleet probably would not even use their engines except to maintain speed and slow down - they'd probably use a stream of mass accelerated pellets launched by mass drivers in their starting system to reach their cruising speed.

Also, all these methods have the problem that they provide pathetically low acceleration. 0.1 g (1 m/s^2) at best, a tiny fraction of that at worst. Realistically, the alien fleet will be decelerating for about 10 years to centuries. We'd be able to see the gamma ray flare from this for many years if a gamma ray telescope is pointed the right way.

As for vulnerability - they'd be immensely vulnerable upon arrival. Not to the technology we have now, but technology we could probably develop relatively rapidly. The alien ships would not have high acceleration engines able to avoid incoming fire or outmaneuver attackers because that kind of engine is too inefficient for interstellar travel. Their ship is unlikely to have anything on it more than a payload of factories and data, because the mass for weapons or engines is too much.

Their plan would almost certainly have to involve decelerating to rest near an object with some mass in our solar system, preferably one close enough to the star so that solar energy is available. One of the various comets or asteroids would do fine. They'd eat the rocks, turning it into more equipment, and essentially regrowing all their technology and infrastructure from the actual starship seed payload.

This is when you jump them. You need an orion drive space battlewagon to show up before the aliens eat enough rocks to build something to fight with.

Comment From reading the actual article, this could work (Score 4, Interesting) 101

The primary problem with this concept is that you have to know very precisely the composition of the ground where you install this barrier. Another problem is that environmental changes - soil moisture, temperature, are going to affect the material properties somewhat (but maybe not enough to matter).

Essentially, extremely low frequency waves that trash buildings don't perceive the ground as atomic, the waves act over their wavelength, which is very long, and so if you put things into the ground, it changes the material properties. Carefully drilled holes apparently can change the properties in dramatic ways. The word "cloak" is sexy, but the more interesting bit mentioned at the end of the paper was the prospect of building a bandstop damper with the low corner at 0 Hz.

It doesn't do you much good if your earthquake prevention device reflects the energy somewhere else dependent on the epicenter, and it also doesn't do you much good if it doesn't block enough frequencies to stop it from trashing your buildings. A bandstop filter would operate over a broad enough band to attenuate all the frequencies, and it wouldn't reflect energy to other buildings (which could have obvious liability concerns.) Imagine a plaintiff's attorney showing a standing wave pattern of destruction emanating from a field of holes drilled by the defendant's firm.

The other satisfying nature of this tech is that it's proactive. Instead of building structures that will probably collapse if a magnitude 8 happens anyway, you go out there and build armor that will stop the earthquake entirely. Also, a field of holes and concrete and various pertubations, all buried, is a lot less ugly than the structural changes needed to reinforce a building against a major earthquake.

It would be expensive to do the detailed surveys and compute the solution, but it would create more high education jobs, and it's probably worth doing.

Comment Re:How I've been taught to do it (Score 1) 367

You feel this solution is a kludge? How should it be done? The way I see it is it provides a nice neat system of separate, extremely reliable and simplified subsystems that are as independent of each other and as simple as they can possibly be.

User Interface layer - instead of running a huge, complex, and memory and power hungry windows OS, you are running a newer OS that is really a flavor of Linux with a bunch of fancy libraries for fancy graphics and multitouch and other features added on.

Communication and transaction layer - instead of running it on the same computer that does the UI (creating the possibility that someone can corrupt the much more complex UI layer and cause it to give them free money), you do all the transactions on a much simpler computer, running well documented (and fully sourced) code and nothing else.

Hardware control layer - instead of doing this on the same computer doing the above, you give each one a dedicated (but extremely tiny and simple) computer for each task.

Comment How I've been taught to do it (Score 1) 367

Finishing my computer engineering degree this semester. The way I've been taught how to implement a system like this is the following :

1. The outermost "user land" control panel should use an OS that is both lightweight, will work on a lot of hardware (so you can switch hardware if during the production of the ATM a vendor goes out of business), and offers a lot of graphical libraries for a pretty interface. Android sounds ideal for this.

2. The android display would communicate via network (probably TCP/IP) with a small server running an embedded flavor of Linux. This server would be stripped down to the minimum features and services, running on a tiny little ARM architecture chip. It would be the computer that actually talks to the bank via encrypted link and controls the cash dispensing process.

3. For the actual physical interlocks and running the motors to dispense the cash, you'd communicate via a serial bus with several small microcontrollers or PLL controllers. Each would be running a very simple program written in C (or ladder logic tree) to do their jobs, which would be to do the actual dispensing and monitoring all the various switches and so forth.

The point of this hierarchy (rather than using one computer to do everything directly) is to compartmentalize the design, allowing you to debug it more easily and also improving security. Someone compromises the outer control panel - they won't be able to dispense cash.

New York... when civilization falls apart, remember, we were way ahead of you. - David Letterman