Before the advent of good silicon rectifiers, generators for cars used exactly this arrangement. The field was a separate winding and the field current was controlled by the regulator which monitored both the output current and voltage. Alternators of course have the field on the rotor connected through slip rings. Some model years during the transition had either system and you could tell the difference via visual inspection because the generators were narrower then the alternators.
AC motors do have power and efficiency advantages but what I was getting at in my original reply is that there is nothing inherent about a DC commutating motor which precludes regenerative breaking. The small market for high power DC motors limits the availability of a suitable controller.
I have seen some very large polyphase alternators that had a small DC generator on the same shaft to power their field winding where the field winding on the DC generator itself was controlled. The residual magnetism in the DC generator's stator was enough to bootstrap the system.
I am not sure why that would be true. If so it is probably a controller issue. Effective DC regenerative breaking would certainly require an impedance transformation via a switching regulator to be effective but that is no different then dealing with an AC motor. High power AC motor control design certainly benefits from large scale use since high power DC motor applications are relatively rare.
AC motors can be used as incredibly effective non regenerative breaks if DC is applied to the field.
One of my books on genetics mentioned that the optimal relatedness for humans based on the number of fatal recessive genes was between first and second cousins. Outside of that fitness slowly declined and inside of it fitness rapidly declined although I suspect the problem is often exaggerated.
The specific section was about an experiment that measured mate selection preferences in pheasants which apparently use such a rule.
From what little I remember, refractive index is the ratio of the speed of light in a medium and the speed in vacuum. Negative index means, negative speed of light? Speed is not a vector. How does one get negative speed?
The index of refraction is the ratio of the speed of light in a vacuum to the phase velocity in the material and the later under certain conditions can be negative meaning that the wave fronts are moving in the opposite direction to the flow of energy.
These materials display some other odd characteristics:
I am reminded of an article in Radio Electronics long ago showing the design and construction of a refractive satellite antenna. It is much easier to cut concentric circles in a flat piece of material then to shape a 3 dimensional parabola. That you can create a lens by obscuring a distant signal in a specific way is not intuitive and I can only imagine what people would think seeing one constructed today.
Stone construction where only compressive forces are used has the advantage that scaling can be used almost indiscriminately. When doubling the size all lengths double, all areas go up by 4 times, and the mass goes up by 8 times. The doubled compressive forces are insignificant to the strength of the stone so it is possible to get by with very simple rules instead of exhaustive mathematical analysis.
Eventually of course you have problems as the medieval cathedral builders and other found out however they were really pushing the state of the art unlike the Romans whose bridge designs often had a static load safety factors exceeding 100 if you exclude their foundations.
Modern structures tend to be limited by buckling which Euler figured out a little more then 200 years ago.
The problem with the Silver Bridge was not so much underdesign, but the lack of redundancy in the eyebars used in the suspension members.
While the suspension eyebar design certainly lacked redundancy it also was not designed in such a way that cracks smaller then the critical crack length for the material at the design load could be discovered through inspection.
In the case of the Silver Bridge, when one of the pins holding two of the eyebars broke, there was no redundant member to take up the load.
It was actually the eye of the eyebar which failed and not the pin. They were single piece castings and it was not possible to inspect the inside area between the pin and the eyebar where the crack formed.
Also that steel gets brittle when cold. See Liberty Ships.
Didn't they use the same steel that was used in the riveted ships preceding them?
One of my engineering materials books lists the Liberty Ship failures as caused by a lack of understanding in stress distribution which the all welded design exasperated. Riveted construction had the advantage of allowing stress relief because the joints had a small amount of give in them.
There was a famous incident where a cook noticed a crack forming from the corner of a joint and was told it was not serious. He used a marker to record its progress by writing the dates down on the surface and when the ship broke in two it was found that catastrophic failure occurred when the fracture exceeded the critical crack length for that material at the designed load.
I had not noticed that. I wonder what their problems are.
I considered why Google does not support IPv6 and came up with nothing. As far as I have been able to tell from my own testing, hosting a dual stack IPv4 and IPv6 web server and other services is not difficult. The only problems I have had so far involve IPv6 firewalling for which I had to roll my own and a rare router connectivity problem at my tunnel provider apparently do to buggy firmware.
I actually make great use of my IPv6 connectivity. It reminds me a lot of the pre-WWW days of the internet with open FTP upload directories and such. It is amazing what is out there.
The first rule of ipv6porn is do not talk about ipv6porn.
All kidding aside:
This page is describing the IPv6 experiment itself, and is primarily intended for networking researchers and software professionals to learn about and discuss the experiment. If you're here for the free content, it's not here! We're not ready for the world to know about this experiment yet, so don't go submitting this to Slashdot or Digg until the actual site is up.
Of course, I already have my IPv6 connectivity through http://www.sixxs.net/ for research purposes. That is my story and I am sticking to it, so to speak.
I figured one short quip deserves another one. If you found my brevity to be insufficient for the seriousness of the problem, please forgive me.
Ignoring for the moment the practical problems in placing the apple back on the tree, the existence of firearms within American society is at best orthogonal to violence. We have proportionally high rates of assault using other weapons such as knives, bats, and a variety of household items. Unless you can successfully argue that the proliferation of firearms increases the number of knife assaults and rapes, I am not prepared to believe that firearms in of themselves are a cause of violence. Certainly they have the potential to make a merely crippling assault deadly but they have the virtue of more then compensating by doing so for the attacking party as well. Nothing says I will not be a victim more then a seriously injured or dead attacker.
Further, by restricting access to firearms and their use beyond those who are obviously disqualified to handle them, we both remove a valuable crime fighting tool (although not a decisive one) and encourage the type of society which would prefer to acquiesce to a hijacking or other violent act ultimately to the detriment of all.
While we are at it, let's make the Republicans and Democrats the only legal parties so as to reduce ambiguity, save money, and remove the third party spoiler effect.
Rail guns are linear, they have no ballistic arc . ..
Of course a rail gun is a ballistic weapon. Over a short range, projectile weapons can be considered line of sight but at some point depending on the muzzle velocity and exterior ballistics compensation for the ballistic trajectory has to be made. For artillery sized weapons, even the curvature and rotation of the earth has to be considered.
Think of a rail gun as a smooth bore cannon with arbitrarily high muzzle velocity. Projectile weapons directly powered by chemical explosives have a muzzle velocity limitation of about 5000 ft/s.
Intel included hardware random number generation in their 82802 firmware hub used in some of the 8xx series chipsets. I never understood why they discontinued that feature.
The only real problem I have had with double NAT setups like this is either buggy modem NAT firmware or NAT state table limitations. My preference is to configure the modem as a bridge and use BSD as the PPPoE endpoint. As a bonus, tech support will completely give up stalling and actually help when faced with BSD.
I am just kidding about the later. I lie and pretend I have a Windows machine connected.
It is even more complicated then that. Like a lot of behaviors, fear depends on a genetic component which requires stimulus from the environment to manifest making it is easier to teach fear of some things then of other things:
. . . So she set up an experiment in which she videotaped the wild-born monkey reacting with fear to a snake, and she then showed this video to a captive-born monkey, which immediately acquired a fear of snakes and was not then prepared to reach across even a model snake to get a peanut. She now doctors the video, so that it has the same monkey reacting in the same way in the background, but the bottom half of the screen now instead of having a snake has a flower. Again, the captive-born monkey has never seen a flower, so after it sees a monkey reacting with extreme fear to this new thing called a flower it should just as easily learn a fear of flowers. But it doesn't. It just learns that some monkeys are crazy. . ..
This would not be the first time I have seen a nVidia based motherboard with multiple LAN ports where the extra third party ones were very useful because the nVidia ones suffered from poor performance, data corruption, and lack of documentation.
There are compromises that have to be made in high current switching voltage regulators that multiphase designs somewhat ameliorate.
At very high currents, not only does the switching element performance become critical (*1) but the parasitic inductance in the layout becomes significant. Using multiple switching stages in parallel allows for easier heat dissipation, easier circuit layout, and less expensive components to be used for a given level of performance. Running the switching stages out of phase lowers the input and output ripple current which can lower the filter capacitor series resistance and inductance requirements considerably.
(*1) Gate drive current is usually limited to about 2 amps or less which limits switching speed with larger MOSFETs which in turn limits efficiency. At higher gate drive, inductance becomes significant enough to begin limiting switching speed without special circuit layout techniques.
I do not have a reference to the court case but I remember reading that federal funds may only be linked to state laws insofar as they have a direct connection with the regulated activity. Federal highway funds for instance may be linked to drunk driving laws, seatbelt laws, and speed limits but may not be linked to activities that do not involve driving.
Like many others in this discussion, I agree that the federal government has misused the interstate commerce clause and the tenth amendment.
Slashdot Mirror
Before the advent of good silicon rectifiers, generators for cars used exactly this arrangement. The field was a separate winding and the field current was controlled by the regulator which monitored both the output current and voltage. Alternators of course have the field on the rotor connected through slip rings. Some model years during the transition had either system and you could tell the difference via visual inspection because the generators were narrower then the alternators.
AC motors do have power and efficiency advantages but what I was getting at in my original reply is that there is nothing inherent about a DC commutating motor which precludes regenerative breaking. The small market for high power DC motors limits the availability of a suitable controller.
I have seen some very large polyphase alternators that had a small DC generator on the same shaft to power their field winding where the field winding on the DC generator itself was controlled. The residual magnetism in the DC generator's stator was enough to bootstrap the system.
I am not sure why that would be true. If so it is probably a controller issue. Effective DC regenerative breaking would certainly require an impedance transformation via a switching regulator to be effective but that is no different then dealing with an AC motor. High power AC motor control design certainly benefits from large scale use since high power DC motor applications are relatively rare.
AC motors can be used as incredibly effective non regenerative breaks if DC is applied to the field.
One of my books on genetics mentioned that the optimal relatedness for humans based on the number of fatal recessive genes was between first and second cousins. Outside of that fitness slowly declined and inside of it fitness rapidly declined although I suspect the problem is often exaggerated.
The specific section was about an experiment that measured mate selection preferences in pheasants which apparently use such a rule.
From what little I remember, refractive index is the ratio of the speed of light in a medium and the speed in vacuum. Negative index means, negative speed of light? Speed is not a vector. How does one get negative speed?
i ndex#Negative_refractive_index
The index of refraction is the ratio of the speed of light in a vacuum to the phase velocity in the material and the later under certain conditions can be negative meaning that the wave fronts are moving in the opposite direction to the flow of energy.
These materials display some other odd characteristics:
http://en.wikipedia.org/wiki/Negative_refractive_
I am reminded of an article in Radio Electronics long ago showing the design and construction of a refractive satellite antenna. It is much easier to cut concentric circles in a flat piece of material then to shape a 3 dimensional parabola. That you can create a lens by obscuring a distant signal in a specific way is not intuitive and I can only imagine what people would think seeing one constructed today.
Thanks for pointing that out.
I was thinking "exacerbated" when I typed "exasperated" and of course poof read it wrong also. I hope next time I will remember.
We are so far down the track that I can not even see them slicing salami.
Stone construction where only compressive forces are used has the advantage that scaling can be used almost indiscriminately. When doubling the size all lengths double, all areas go up by 4 times, and the mass goes up by 8 times. The doubled compressive forces are insignificant to the strength of the stone so it is possible to get by with very simple rules instead of exhaustive mathematical analysis.
Eventually of course you have problems as the medieval cathedral builders and other found out however they were really pushing the state of the art unlike the Romans whose bridge designs often had a static load safety factors exceeding 100 if you exclude their foundations.
Modern structures tend to be limited by buckling which Euler figured out a little more then 200 years ago.
The problem with the Silver Bridge was not so much underdesign, but the lack of redundancy in the eyebars used in the suspension members.
While the suspension eyebar design certainly lacked redundancy it also was not designed in such a way that cracks smaller then the critical crack length for the material at the design load could be discovered through inspection.
In the case of the Silver Bridge, when one of the pins holding two of the eyebars broke, there was no redundant member to take up the load.
It was actually the eye of the eyebar which failed and not the pin. They were single piece castings and it was not possible to inspect the inside area between the pin and the eyebar where the crack formed.
Also that steel gets brittle when cold. See Liberty Ships.
Didn't they use the same steel that was used in the riveted ships preceding them?
One of my engineering materials books lists the Liberty Ship failures as caused by a lack of understanding in stress distribution which the all welded design exasperated. Riveted construction had the advantage of allowing stress relief because the joints had a small amount of give in them.
There was a famous incident where a cook noticed a crack forming from the corner of a joint and was told it was not serious. He used a marker to record its progress by writing the dates down on the surface and when the ship broke in two it was found that catastrophic failure occurred when the fracture exceeded the critical crack length for that material at the designed load.
I had not noticed that. I wonder what their problems are.
I considered why Google does not support IPv6 and came up with nothing. As far as I have been able to tell from my own testing, hosting a dual stack IPv4 and IPv6 web server and other services is not difficult. The only problems I have had so far involve IPv6 firewalling for which I had to roll my own and a rare router connectivity problem at my tunnel provider apparently do to buggy firmware.
I actually make great use of my IPv6 connectivity. It reminds me a lot of the pre-WWW days of the internet with open FTP upload directories and such. It is amazing what is out there.
The first rule of ipv6porn is do not talk about ipv6porn.
All kidding aside:
This page is describing the IPv6 experiment itself, and is primarily intended for networking researchers and software professionals to learn about and discuss the experiment. If you're here for the free content, it's not here! We're not ready for the world to know about this experiment yet, so don't go submitting this to Slashdot or Digg until the actual site is up.
Of course, I already have my IPv6 connectivity through http://www.sixxs.net/ for research purposes. That is my story and I am sticking to it, so to speak.
I figured one short quip deserves another one. If you found my brevity to be insufficient for the seriousness of the problem, please forgive me.
Ignoring for the moment the practical problems in placing the apple back on the tree, the existence of firearms within American society is at best orthogonal to violence. We have proportionally high rates of assault using other weapons such as knives, bats, and a variety of household items. Unless you can successfully argue that the proliferation of firearms increases the number of knife assaults and rapes, I am not prepared to believe that firearms in of themselves are a cause of violence. Certainly they have the potential to make a merely crippling assault deadly but they have the virtue of more then compensating by doing so for the attacking party as well. Nothing says I will not be a victim more then a seriously injured or dead attacker.
Further, by restricting access to firearms and their use beyond those who are obviously disqualified to handle them, we both remove a valuable crime fighting tool (although not a decisive one) and encourage the type of society which would prefer to acquiesce to a hijacking or other violent act ultimately to the detriment of all.
The only reason we need guns is to protect us from the sort of jerks who own guns...
Because violence did not exist before firearms.
While we are at it, let's make the Republicans and Democrats the only legal parties so as to reduce ambiguity, save money, and remove the third party spoiler effect.
It is not fascism when we do it.
Rail guns are linear, they have no ballistic arc . . .
Of course a rail gun is a ballistic weapon. Over a short range, projectile weapons can be considered line of sight but at some point depending on the muzzle velocity and exterior ballistics compensation for the ballistic trajectory has to be made. For artillery sized weapons, even the curvature and rotation of the earth has to be considered.
Think of a rail gun as a smooth bore cannon with arbitrarily high muzzle velocity. Projectile weapons directly powered by chemical explosives have a muzzle velocity limitation of about 5000 ft/s.
Intel included hardware random number generation in their 82802 firmware hub used in some of the 8xx series chipsets. I never understood why they discontinued that feature.
I am altering the deal. Play I do not alter it any further.
The only real problem I have had with double NAT setups like this is either buggy modem NAT firmware or NAT state table limitations. My preference is to configure the modem as a bridge and use BSD as the PPPoE endpoint. As a bonus, tech support will completely give up stalling and actually help when faced with BSD.
I am just kidding about the later. I lie and pretend I have a Windows machine connected.
It is even more complicated then that. Like a lot of behaviors, fear depends on a genetic component which requires stimulus from the environment to manifest making it is easier to teach fear of some things then of other things:
5 .html
.
http://www.edge.org/3rd_culture/ridley03/ridley_p
. . . So she set up an experiment in which she videotaped the wild-born monkey reacting with fear to a snake, and she then showed this video to a captive-born monkey, which immediately acquired a fear of snakes and was not then prepared to reach across even a model snake to get a peanut. She now doctors the video, so that it has the same monkey reacting in the same way in the background, but the bottom half of the screen now instead of having a snake has a flower. Again, the captive-born monkey has never seen a flower, so after it sees a monkey reacting with extreme fear to this new thing called a flower it should just as easily learn a fear of flowers. But it doesn't. It just learns that some monkeys are crazy. . .
This would not be the first time I have seen a nVidia based motherboard with multiple LAN ports where the extra third party ones were very useful because the nVidia ones suffered from poor performance, data corruption, and lack of documentation.
Since the switching regulator chops the DC into AC the use of the term phase is completely accurate.
There are compromises that have to be made in high current switching voltage regulators that multiphase designs somewhat ameliorate.
At very high currents, not only does the switching element performance become critical (*1) but the parasitic inductance in the layout becomes significant. Using multiple switching stages in parallel allows for easier heat dissipation, easier circuit layout, and less expensive components to be used for a given level of performance. Running the switching stages out of phase lowers the input and output ripple current which can lower the filter capacitor series resistance and inductance requirements considerably.
(*1) Gate drive current is usually limited to about 2 amps or less which limits switching speed with larger MOSFETs which in turn limits efficiency. At higher gate drive, inductance becomes significant enough to begin limiting switching speed without special circuit layout techniques.
If you were plowing a field, which would you rather use: Two strong oxen or 1024 chickens? - Seymour Cray
I do not have a reference to the court case but I remember reading that federal funds may only be linked to state laws insofar as they have a direct connection with the regulated activity. Federal highway funds for instance may be linked to drunk driving laws, seatbelt laws, and speed limits but may not be linked to activities that do not involve driving.
Like many others in this discussion, I agree that the federal government has misused the interstate commerce clause and the tenth amendment.