The coal power plant has much better energy efficiency and makes much less pollution per kWh of energy produced then the small automotive internal combustion engine. By ?plugging? your electric car to the said hot'n'smoky power station you ARE actually making significantly less pollution. I am not advocating fossil fuel energy production and would actually like to see it phased out. Electric vehicles are the step in right direction.
Let's get the physics straight
on
Homemade Gauss Gun
·
· Score: 2, Insightful
If You observe system in its initial "armed" condition you will find that it is not in its lowest possible energy configuration. Steel balls that are not immediately adjacent to magnets, do have higher potential energy than the balls touching the magnets. After firing, all the balls (except the projectile) are touching the magnets, meaning that the system has lower potential energy. The difference is the kinetic energy of the projectile.
You are, of course, right when you say that initial energy of the system came from the hands of the person who arranged the balls.
Now let's get semantics straight.
>However, none of the fixed magnets imparts energy to the ball
When the kinetic energy of the particle is enhanced at the expense of the system's potential energy (for the conservative system), the common expression in physics literature is that "field imparted energy to the particle". The expression: energy is "released" is also quite common and it simply means that system is in the configuration with lower potential energy.
Now let's get you straight.
>The energy of separating the magnets is not 'released' during this experiement, as the magnets do not move.
Indeed magnets did not move, but the balls did and the potential energy of the system is lower....
My 386 DID run faster than any 286. It was 33 MHz:). Granted, early adopters had no benefits in DOS applications. You made the valid point that "some hardware development has a much higher payoff than others" but I am not sure it applies to 386. Protected mode, introduced by 386 is THE advancement that enabled "modern" OS-s on consumer desktop. One may argue that X86 architecture was the worst possible one to start with (bunch of legacy crap: 1Mb barmier, etc, etc), but it is the standard accepted by the market. I would say that this particular development brought handsome payoff at least to Intel.
As for your remark about "OS and Apps that don't run 'fast enough' on any existing hardware" it is hen or egg seniority paradox. Every new generation of software prompts (commercial) development of hardware and vice versa. Conspiracy theoreticians drool about unholy alliance between hardware and software vendors. Funny thing is that they are probably right. However, the end result is that we have more powerful computers at affordable prices. Computer hardware is one of the few things that has millions of engineer-hours behind its development and still sells for peanuts.
I could not agree more! Every now and then one can find opinions like: Nobody normal needs such speed or that much of memory... I can still remember zealous defenders of "good ol' 286" and their arguments that 386 is "unnecessary complication". I agree that every new development of the cpu muscle is usually wasted on making office assistant doing more fancy tricks. However, a new hardware development eventually gets employed for the more useful purposes. Geeks that frequent this board often discuss things like DV cameras and editing video material. Only few years ago such things were reserved for expensive SGI-s. Today you can do it on a platform with the price tag below $1k (only hardware though). Bottom Line: Every new breakthrough in technology is Good Thing (TM). It means that by the time it hits consumer market, geeks will have plenty of inexpensive toys to play with.
Wrong! Energy levels are eigen-value solutions of the schrodinger equation for the given system (atom, molecule,...). For particular shapes of the potential part of the Hamiltonian, solutions CAN lie in the continuum.
Hmrr, parent post is a valid question and deserves a proper answer.
Lasing phenomena occurs in some media if you have so called "inverse population" of metastabile states of molecules. "Metastabile" means that those (excited) states cannot de-excite in to the lower energy level by spontaneous photon emission (e.g. momentum conservation forbids singlet-triplet transitions). However, if such metastabile molecule is hit by the photon with the energy that corresponds to the difference between upper and lower energy level of the molecule, a stimulated emission occurs. Emitted photon has the same wavelength, phase and direction as the incident one. In the conditions of inverse population (lots of metastbiles and sparsely populated lower levels), something similar to chain reaction happens. The initial photon gets multiplied in the geometric progression as it propagates trough the medium. This accounts for "Amplification" in the acronym LASER. In many cases upper and lower energy levels are well defined i.e. discrete, but they can be energy bands or even continuum. In the later case the wavelength of the "triggering" photon can lie in the range of values. This is actually the answer to the parent of this thread.
The lasing medium is usually confined in so called resonant cavity consisting of parallel mirrors. The reason for this is to effectively enhance the length of propagation in one preferential direction. The bunch of photons are bouncing back and forth between the mirrors many times and each time they traverse medium their number is increased. One of the mirrors is somewhat transparent and the portion of the beam exits the cavity.
The speed of the signal propagation trough the medium is not equal to the speed of electrons. The actual speed (group velocity) depends on properties of the "transmission line". For the good old coax cable it is about 0.66% of the speed of light. It is obvious that electrons in the coax cable do not even remotely approach that velocity but, the fact remains that signal travels ~20 cm during period of 1 ns. The actual fraction of c for the lines on silicon chip is very similar to the previous example.
When you discuss physics it helps if you know basic facts.
Did anybody actually built /configured a cluster?
on
Macintosh Clustering
·
· Score: 1
Well I did. Our cluster is intended for solving complex problems in radiation transport theory. Applications are ranging from Monte Carlo simulations (trivially paralellizable) to the numerical solving of coupled differential equations (damn hard to parallelize). We are using every tool in the book: PVM (parallel virtual machine), MPI (message parsing interface) as well as various batch queuing systems. Language of choice for this kind of computation is FORTRAN.
My point is following: If you need a cluster for the scientific research you have to do a lot of your own programming and customization. Many of the comments posted here are along the lines of high costs for the configuration of linux cluster. That argument is simply not applicable in this case. The overhead spent on actual configuration is negligible in comparison to the time spent on actual coding. Moreover above mentioned tools make the task of parallelization much easier.
I admit, I don't know much about Mac's, but: Are there any good FORTRAN compilers for Mac (comparable to HPF)? It seam's that "pooch" drag'n'drop approach does not give me much of the control of how the subprocesses are spawned. What sort of the libraries and toolkits are provided?
One more point: Using SMP machines as cluster nodes is not necessarily the best way to go. MPI, for example, does not like threads much. At any rate, it is very hard to write an application that will fully utilize high bandwidth that SMP offers, while simultaneously having lower bandwidth utilization between ethernet connected nodes.
Lastly, for all the/. geeks here is our configuration:
24 nodes, each node having:
Epox 8KHA+
512 Mb Mushckin high performance cas2 ram
Athlon XP 1900+
20 Gb Maxtor HDD
Lynksys Gigabit NIC
$45 el chipo case (we had a good previous experience with the particular model though)
Slashdot Mirror
A word about hot'n'smoky power station.
The coal power plant has much better energy efficiency and makes much less pollution per kWh of energy produced then the small automotive internal combustion engine. By ?plugging? your electric car to the said hot'n'smoky power station you ARE actually making significantly less pollution.
I am not advocating fossil fuel energy production and would actually like to see it phased out. Electric vehicles are the step in right direction.
If You observe system in its initial "armed" condition you will find that it is not in its lowest possible energy configuration. Steel balls that are not immediately adjacent to magnets, do have higher potential energy than the balls touching the magnets. After firing, all the balls (except the projectile) are touching the magnets, meaning that the system has lower potential energy. The difference is the kinetic energy of the projectile.
You are, of course, right when you say that initial energy of the system came from the hands of the person who arranged the balls.
Now let's get semantics straight.
>However, none of the fixed magnets imparts energy to the ball
When the kinetic energy of the particle is enhanced at the expense of the system's potential energy (for the conservative system), the common expression in physics literature is that "field imparted energy to the particle". The expression: energy is "released" is also quite common and it simply means that system is in the configuration with lower potential energy.
Now let's get you straight.
>The energy of separating the magnets is not 'released' during this experiement, as the magnets do not move.
Indeed magnets did not move, but the balls did and the potential energy of the system is lower....
My 386 DID run faster than any 286. It was 33 MHz :). Granted, early adopters had no benefits in DOS applications.
You made the valid point that "some hardware development has a much higher payoff than others" but I am not sure it applies to 386. Protected mode, introduced by 386 is THE advancement that enabled "modern" OS-s on consumer desktop. One may argue that X86 architecture was the worst possible one to start with (bunch of legacy crap: 1Mb barmier, etc, etc), but it is the standard accepted by the market. I would say that this particular development brought handsome payoff at least to Intel.
As for your remark about "OS and Apps that don't run 'fast enough' on any existing hardware" it is hen or egg seniority paradox. Every new generation of software prompts (commercial) development of hardware and vice versa. Conspiracy theoreticians drool about unholy alliance between hardware and software vendors. Funny thing is that they are probably right. However, the end result is that we have more powerful computers at affordable prices. Computer hardware is one of the few things that has millions of engineer-hours behind its development and still sells for peanuts.
I could not agree more!
Every now and then one can find opinions like: Nobody normal needs such speed or that much of memory... I can still remember zealous defenders of "good ol' 286" and their arguments that 386 is "unnecessary complication".
I agree that every new development of the cpu muscle is usually wasted on making office assistant doing more fancy tricks. However, a new hardware development eventually gets employed for the more useful purposes.
Geeks that frequent this board often discuss things like DV cameras and editing video material. Only few years ago such things were reserved for expensive SGI-s. Today you can do it on a platform with the price tag below $1k (only hardware though).
Bottom Line: Every new breakthrough in technology is Good Thing (TM). It means that by the time it hits consumer market, geeks will have plenty of inexpensive toys to play with.
Wrong! ...). For particular shapes of the potential part of the Hamiltonian, solutions CAN lie in the continuum.
Energy levels are eigen-value solutions of the schrodinger equation for the given system (atom, molecule,
Hmrr, parent post is a valid question and deserves a proper answer.
Lasing phenomena occurs in some media if you have so called "inverse population" of metastabile states of molecules. "Metastabile" means that those (excited) states cannot de-excite in to the lower energy level by spontaneous photon emission (e.g. momentum conservation forbids singlet-triplet transitions). However, if such metastabile molecule is hit by the photon with the energy that corresponds to the difference between upper and lower energy level of the molecule, a stimulated emission occurs. Emitted photon has the same wavelength, phase and direction as the incident one. In the conditions of inverse population (lots of metastbiles and sparsely populated lower levels), something similar to chain reaction happens. The initial photon gets multiplied in the geometric progression as it propagates trough the medium. This accounts for "Amplification" in the acronym LASER. In many cases upper and lower energy levels are well defined i.e. discrete, but they can be energy bands or even continuum. In the later case the wavelength of the "triggering" photon can lie in the range of values. This is actually the answer to the parent of this thread.
The lasing medium is usually confined in so called resonant cavity consisting of parallel mirrors. The reason for this is to effectively enhance the length of propagation in one preferential direction. The bunch of photons are bouncing back and forth between the mirrors many times and each time they traverse medium their number is increased. One of the mirrors is somewhat transparent and the portion of the beam exits the cavity.
oooops 66%
The speed of the signal propagation trough the medium is not equal to the speed of electrons. The actual speed (group velocity) depends on properties of the "transmission line". For the good old coax cable it is about 0.66% of the speed of light. It is obvious that electrons in the coax cable do not even remotely approach that velocity but, the fact remains that signal travels ~20 cm during period of 1 ns. The actual fraction of c for the lines on silicon chip is very similar to the previous example.
When you discuss physics it helps if you know basic facts.
Well I did. Our cluster is intended for solving complex problems in radiation transport theory. Applications are ranging from Monte Carlo simulations (trivially paralellizable) to the numerical solving of coupled differential equations (damn hard to parallelize). We are using every tool in the book: PVM (parallel virtual machine), MPI (message parsing interface) as well as various batch queuing systems. Language of choice for this kind of computation is FORTRAN.
/. geeks here is our configuration:
My point is following: If you need a cluster for the scientific research you have to do a lot of your own programming and customization. Many of the comments posted here are along the lines of high costs for the configuration of linux cluster. That argument is simply not applicable in this case. The overhead spent on actual configuration is negligible in comparison to the time spent on actual coding. Moreover above mentioned tools make the task of parallelization much easier.
I admit, I don't know much about Mac's, but: Are there any good FORTRAN compilers for Mac (comparable to HPF)? It seam's that "pooch" drag'n'drop approach does not give me much of the control of how the subprocesses are spawned. What sort of the libraries and toolkits are provided?
One more point: Using SMP machines as cluster nodes is not necessarily the best way to go. MPI, for example, does not like threads much. At any rate, it is very hard to write an application that will fully utilize high bandwidth that SMP offers, while simultaneously having lower bandwidth utilization between ethernet connected nodes.
Lastly, for all the
24 nodes, each node having:
Epox 8KHA+
512 Mb Mushckin high performance cas2 ram
Athlon XP 1900+
20 Gb Maxtor HDD
Lynksys Gigabit NIC
$45 el chipo case (we had a good previous experience with the particular model though)
Overall hardware cost ~$16000
OS: RedHat 7.2
My 0.02 Dinars