I like CDE. But then my prefered environment on linux is Xfce4. I don't want icons on the root window, I'm not that into the pointy clicky thing.
The screenshots show the default CDE desktop at a low resolution. Yep, it looks like crap. But CDE is quite customizable. Probobly the first thing to do is just click the middle mouse button and iconify the ugly app bar, then change the background to something not ugly, then set the resolution to something reasonable.
I have CDE running on Solaris 10 on an old Ultra60 with dual 1600x1200 screens and it runs and looks great. I think it looks better than JDS on the same system.
Hey, I like Slackware a lot. I started with slack from a book and kernel 1.2 in 1994. It was all I used until I discovered LFS and then gentoo.
ok, pandering out of the way, now I have to say it:
PV is sounding a bit like a kook in his letter.
First, it is long and rambling and mostly irrelevant. Then he mentions how he prescribed himself a 2 month supply of ciproflaxacin in OCT 2001, now he disagrees with the ABX he is being prescribed and wants to prescribe himself something else. WTF? Throw in this weird "popping and draining" symptom despite CT scans which have not shown abscess, empyema, or much of anything, plus a narative that demonstrates a misunderstanding of some basic medical facts, plus he has been to multiple hospitals and nobody has thought he was sick enough to warrant admission. Sure, doctors make mistakes all the time, but one really starts to wonder how much of this is comming from above the neck.
Anyways, I hope he gets well soon. And remember, a little knowledge can be a dangerous thing.
I use card export on my original Tungsten T and it works great. Don't need to install anything on the windows computer and the palms card shows up as a drive in explorer.
Imagine you are a small hospital, one with a 10 bed ICU. You have 10 patients.
First, a 10 bed ICU is not small. It is average Your hypothetical 750 bed unit does not exist. Can you afford to have someone near enough to each heart monitor to hear when it has an irregular heartbeart? Can you even detect a slightly altered heart-rate just by a casual listen/look every now and then? What about all the other funny intrumentation? Of course not. It would take one RN/CNA/Med. Tech per ICU patient per shift.
We are talking about an ICU, as in intensive care unit. What do you suppose that means? I will give you a clue: it means intensive care, typically about two patients per RN. As far as CNAs and Med. Techs go, they don't really have any medical training and are not the ones watching the monitors.
I find it interesting that the New York Times version of the story is titled, 'Apple Chief Has Emergency Cancer Surgery' seems they had to throw that 'Emergency' in there. The other places I have seen the story never mention 'Emergency' in the title or the body of the article.
Consider this: Jobs had his surgery on a saturday. Hospitals (at least in the US) pretty much run on a skeleton crew on the weekends. It would be pretty unusual to schedule a case on saturday. Any time someone has surgery on a sturday or sunday you can be fairly certain it was because there was some sense of urgency.
The New York Times 'Emergency' title is probably closest to the truth.
This is actually an interesting question. I am not specifically aware of any general screening possible for pancreatic cancer either. There are many blood markers that can be positive for specific cancer types, but it seems more likely that an MRI or CT scan for something else (unrelated) showed this tumor.
Actualy, that is probobly not how it went down.
One can think of the pancreas as functionaly divided into two systems: the exocrine pancreas and the endocrine pancreas.
The exocrine pancreas is involved in the digestion of food and is where the vast majority of pancreatic tumors occur. One of the reasons they are so often fatal is that tumors of the exocrine pancreas rarely produce symptoms befor they extend into other structures.
The endocrine pancreas produces several hormones, including insulin, glucogon, VIP, somatostatin, and so on. Tumors of this portion of the pancreas often do produce symptoms secondary to overproduction of one or more of these hormones.
Jobs tumor was one of the endocrine types (he does not say more specificaly) so it would not be unusual for his tumor to have prompted studies which led to its detection.
This book takes one from zero to writing a compiler in a few hundred pages, including a chapter on writing code for register machines which gives the student a good idea of what is going on "under the hood."
To those who would say that Scheme is useless outside of academics, I would counter that once the concepts in this text are mastered, it is easy to transfer them to other languages.
DynaSoar said: ...lesioning them with the neurotoxin thought to cause Parkinson's apoptosis, MPTP.
Actually, MPTP is not involved in the pathophysiology of Parkinson's. MPTP is, however, very usefull for creating an animal model of Parkinson's disease, and has proven to be a very useful tool for the study of PD.
Consider a see-saw with one side twice as long as the other, measured from the fulcrum. The load on the short end of the see-saw is twice as massive as the load on the long end, and the see-saw balances. Motion of either load causes the other to move, such that the lighter mass moves twice as far as the heavy one.
The analogy, I believe, is that the mass of the loads would be the electric pressure, or voltage. The distance moved would be the amount of electric current, or amperage. The long side of the see-saw has half as many transformer windings as the other side, and thus a large current of small voltage on that side induces a smaller current of a larger voltage on the other side.
You are on the right track, but not quite there yet. see below.
Or maybe that analogy sucks, and it would make more sense intuitively if you used mass=current, height=voltage? Then the long side would be the more-windings side.
You are getting closer here. One of the most important points is that the "stuff" which is "flowing" must be conserved (in the physics sense). Think of electronics here: current is a "flow" of charge, and charge is conserved. Think about it for a minute and you will see how this conservation of charge leeds directly to the nodal equations for current in a circuit. Whatever you pick to "flow" in the see-saw example must be conserved if you want to use the same equations. For example, using a hydraulic analogy, mass is conserved, so the sum of flows into a junction of pipes must equal zero. In the hydraulic example, mass=charge, mass flow=current.
Also, whatever is providing the force to drive your "stuff" must meet the definition of a "potential." I don't want to go into that now, but their is a fairly rigorous definition of what a "potential" is and voltage meets that definition. Whatever you pick as providing the force to drive your "stuff" in the see-saw analogy must meet be a "potential" if you want to use the same equations.
But the basic idea is right, yes?
Yes, getting there.
I am not familiar, though, with "coupled transducers" and domains... can you explain?
Sure, I will start. First, think of a "transducer." Probably the one most people are familliar with is a loudspeaker. You put electrical energy in one side of the speaker and and acoustic (kinetic) energy comes out the other end. What is really going on? You have a "flow" of one sort of "stuff" (charge) going in one end, and a "flow" of some other conserved "stuff" coming out the other end. In the process you have converted energy from one "domain" to another (electrical to kinetic). I don't want to give too much away here. Now, one can run the loudspeaker in reverse and convert kinetic energy into electrical energy (think microphone). this is a general property of "transducers." Two loudspeakers pointed at each other are an example of coupled transducers. You can put electricity into one speaker and get it out of the other, maybe not very efficiently, but one can imagine tweaking the number of windings, etc, and having something which behaves like a very inefficient trasformer.
This transformer built out of speakers is actually very similar to one built the conventional way: they are both examples of "coupled transducers," only the "domain" in the middle is differant.
More apropos to the see-saw analogy, one may think of a wrench as a trasducer. Think about what goes on when you tighten a bolt with a wrench. Think about having a second wrench on the other side of the bolt. Think about what is conserved and what is "flowing."
Accelerating objects experience a force against the direction of the acceleration vector. I can imagine transverse structural members in an assembly (read: "rocket ship") having limits to how fast lateral (from their reference frame) force changes can be accomodated. Thus, they'd have "jerk" limits.
Um, actually they do not. You are correct that your hypothetical rocket could be torn apart, but it doesn't have anything to do with a force "against the direction of acceleration." There is no such force. I think you got confused because you are thinking in terms of the non-inertial reference frame of the rocket.
A slinky with a string tied to one end can serve as a model for your hypothetical rocket. Jerk the string hard enough and you can break the slinky, but there is no force pulling any part of the slinky in the other direction.
What is really going on is that you have an object which is not perfectly rigid so it temporarily stores some of the energy you have provided with your jerk. It takes a while for the momentum (speed * mass) to "flow" from one end of the slinky to the other. If the energy density from storing this "flow" is too large, well, then you have breakage.
Keep in mind that momentum is conserved, just like energy. Of course, some of the energy you applied with your string can become heat energy rather than kinetic energy, but the momentum has nowhere else to go.
Now, if this reminds you a bit of basic electronics, you are on the right track: in both case you have some conserved "stuff" (charge in one case, momentum in the other) and a "potential" (voltage on one case, force in the other) which can move your "stuff" around, subject to certain rules.
It is no coincidence that the same equations which work for electronics work for this mechanical stuff.
Give yourself extra-credit if you can reason out which circuit element is analgous to the slinky. is it a resistor, capacitor, or inductor?
A+ if you can describe how the see-saw/transformer are two coupled transducers, and describe the flowing "stuff" and "potential" in each case, and which domains the transducers operate in.
Hrm. I encountered that problem in
kindergarden. Some annoying damn kid (you know, the one that always smelled funny and had snot pouring out of his nose constantly) named Larry (I think). Wouldn't leave me alone; he wanted to see my dick.
One day, he followed me into the restroom, and I went into the stall. He poked his head from underneath the divider, and I pissed on his face. Needless to say, he never bothered me again.
Hey Genius! You do know that this sort of behaviour (wanting to see your dick) in a five year old is a sign of child abuse?
You were not expectected to know this at the time (I assume you were five also), but now you are.
So you pissed on the face of a five year old child who almost certainly had been sexualy abused, and you brag about it now that you are a teen/adult?
Bonus points to bags with material that actually absorbs inpact force, although it's typically destructive (think the foam inside helmets, or crumple zones in cars).
Um, No. It is only important to reduce the acceleration of the object you are trying to protect.
Of course, I understand that force and acceleration differ only by a scaling factor (Newton's second law: F=mA). Describing "impact force" as being "absorbed" make no sense, just as it makes no sense to describe "acceleration" as being "absorbed," just as it makes no sense to describe "temperature" as being "absorbed."
Remember that first chapter in your physics book, where they talked about "intensive" versus "extensive" properties?
Dunbar is 100 percent correct on this. A couple of common examples of physics at work, at the same scale he describes (1.0mm to 20mm), are motorcycle helmets and boxing gloves, which both work quite well.
If you use emacs you might like: calc(scroll down the page a bit).
Calc does RPN, symbolic math, graphing, and more, all from within emacs. If you are using emacs 21.1 you need to apply a patch to the calc source before compiling. the patch can be found by doing C-h P in emacs and searching for "calc" in the displayed problems file.
[obCaveat: "Unless I'm missing the point entirely."]
Why yes! you are missing the point entirely, as others have pointed out.
Also, the they you mention is actually a he who really does know a little something about optics, not a "semi-dabbler."
Re:some interesting applications
on
Powered by Blood
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· Score: 1
Good point. Somewhat more realisticaly, if this device had any sort of longevity, it could be used as an implantable glucose sensor. With that, one could make a closed loop insulin pump. There exist pumps now, of course, but their control is open loop, total crap compared to what one could do if they had a glucose sensor.
What does this mean? Are you saying that theoritically perfect DAC reproduction at the Nyquist limit requires infinite bit depth?
Think about quantization for a moment: it is a many-to-one mapping of an input signal to a quantized signal. Therefor, it is an irreversible process. Another way of saying this is that there are an infinite number of signals which will have the same quantized representation.
Without going into detail, the effect of quantization can be modeled as adding an error signal to the orriginal signal. If the input signal meets certain conditions, this error signal will look like white noise. There is no way to remove this noise once the signal is quantized.
What adding more bits does is to reduce the power of this added noise signal. (it also tends to make it look more like white noise)
So, briefly, adding more bits improves the signal to noise ratio but has no effect on the frequency response.
In some simple tests I have done I have seen this as worth while. I have two pages I have created that might be worth a read:
I took a look at your pages. Particularly interesting is the page with the benchmarks. You had better take a look at the code gcc is generating with these options. The reason -O3 gave a factor of 20 speedup with your simple tests is because gcc is smart enough to tell that your code never does anything with the variable named "something." Because this variable is never used, gcc eliminates all of the arithmetic involving this variable when you ask it to optimize. The inner loop is completely eliminated from your code when you pass gcc -O3.
Re:It is not the bits..
on
Is Louder Better?
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· Score: 4, Informative
Nyquest states that the highest frequency digital sampling can reproduce is half the sample rate. Think about that: that means that at that frequency you are getting only 2 samples per cycle of the wave. Connect the dots and you have a triangle wave. But what if the original signal was a sine wave? You've lost the shape of the original wave.
By reproducing a triangle wave, you've added harmonics to the sound that didn't previously exist. Granted, they are out of the range of human hearing, but they can still have an audible effect on the sound due to canceling and phase shifts. But take even a frequency at 1/4 the sampling frequency. Now you've got 4 points to reproduce the sine wave, but its still going to be a jagged approxamation. As you can see, more samples per second gives a better reproduction of the original signal.
Sorry, but you seem to misunderstand the situation. What the sampling theorem tells us is that as long as the input signal is bandlimited to frequencies below one half the sampling frequency, it can be reproduced exactly by the DAC. (nb: this is for samples which have not been quantized) The reconstruction is taken care of by what is commonly known as a reconstruction filter. You are correct that the samples of a sine wave near the Nyquist frequency will look like a triangle wave, but once passed through the reconstruction filter what comes out is the original sine wave.
Note that the requirement that the signal be bandlimited means, for example, that one can not have as input a triangle wave near the nyquist frequency, because, as you correctly stated, a triangle wave of such a frequency contains harmonics which are greater than the nyquist frequency. Typicaly, they would be removed by an antialiasing filter at the input to the ADC.
Of course, I realize that it is not possible to implement an ideal reconstruction filter, and also that quantizing the signal introduces distortion which it is not possible to remove.
I must say that while working at a VA hospital last year I was very much impressed with their computer system.
The VA is the largest healthcare organization in the US, so they have the resources to build their own system. Contrary to what I was expecting, it is intuitive, just plain works, and IMHO blows away the stuff from Cerner or Meditech.
They have been working on it for twenty years, so it has the advantage of maturity, but even the newer bits such as windows interfaces running on Citrix are nice and stable.
Slashdot Mirror
I like CDE. But then my prefered environment on linux is Xfce4. I don't want icons on the root window, I'm not that into the pointy clicky thing.
The screenshots show the default CDE desktop at a low resolution. Yep, it looks like crap. But CDE is quite customizable. Probobly the first thing to do is just click the middle mouse button and iconify the ugly app bar, then change the background to something not ugly, then set the resolution to something reasonable.
I have CDE running on Solaris 10 on an old Ultra60 with dual 1600x1200 screens and it runs and looks great. I think it looks better than JDS on the same system.
I really enjoyed reading this advertisement.
Hey, I like Slackware a lot. I started with slack from a book and kernel 1.2 in 1994. It was all I used until I discovered LFS and then gentoo.
ok, pandering out of the way, now I have to say it:
PV is sounding a bit like a kook in his letter.
First, it is long and rambling and mostly irrelevant. Then he mentions how he prescribed himself a 2 month supply of ciproflaxacin in OCT 2001, now he disagrees with the ABX he is being prescribed and wants to prescribe himself something else. WTF? Throw in this weird "popping and draining" symptom despite CT scans which have not shown abscess, empyema, or much of anything, plus a narative that demonstrates a misunderstanding of some basic medical facts, plus he has been to multiple hospitals and nobody has thought he was sick enough to warrant admission. Sure, doctors make mistakes all the time, but one really starts to wonder how much of this is comming from above the neck.
Anyways, I hope he gets well soon. And remember, a little knowledge can be a dangerous thing.
...It hurt his credibility a little...
We have arrived at a truly sad state when it hurts someones credibility if they tell the truth.
I use card export on my original Tungsten T and it works great. Don't need to install anything on the windows computer and the palms card shows up as a drive in explorer.
Imagine you are a small hospital, one with a 10 bed ICU. You have 10 patients.
First, a 10 bed ICU is not small. It is average
Your hypothetical 750 bed unit does not exist.
Can you afford to have someone near enough to each heart monitor to hear when it has an irregular heartbeart? Can you even detect a slightly altered heart-rate just by a casual listen/look every now and then? What about all the other funny intrumentation? Of course not. It would take one RN/CNA/Med. Tech per ICU patient per shift.
We are talking about an ICU, as in intensive care unit. What do you suppose that means?
I will give you a clue: it means intensive care, typically about two patients per RN. As far as CNAs and Med. Techs go, they don't really have any medical training and are not the ones watching the monitors.
I find it interesting that the New York Times version of the story is titled, 'Apple Chief Has Emergency Cancer Surgery' seems they had to throw that 'Emergency' in there. The other places I have seen the story never mention 'Emergency' in the title or the body of the article.
Consider this: Jobs had his surgery on a saturday. Hospitals (at least in the US) pretty much run on a skeleton crew on the weekends. It would be pretty unusual to schedule a case on saturday. Any time someone has surgery on a sturday or sunday you can be fairly certain it was because there was some sense of urgency.
The New York Times 'Emergency' title is probably closest to the truth.
This is actually an interesting question. I am not specifically aware of any general screening possible for pancreatic cancer either. There are many blood markers that can be positive for specific cancer types, but it seems more likely that an MRI or CT scan for something else (unrelated) showed this tumor.
Actualy, that is probobly not how it went down.
One can think of the pancreas as functionaly divided into two systems: the exocrine pancreas and the endocrine pancreas.
The exocrine pancreas is involved in the digestion of food and is where the vast majority of pancreatic tumors occur. One of the reasons they are so often fatal is that tumors of the exocrine pancreas rarely produce symptoms befor they extend into other structures.
The endocrine pancreas produces several hormones, including insulin, glucogon, VIP, somatostatin, and so on. Tumors of this portion of the pancreas often do produce symptoms secondary to overproduction of one or more of these hormones.
Jobs tumor was one of the endocrine types (he does not say more specificaly) so it would not be unusual for his tumor to have prompted studies which led to its detection.
All just speculation, of course.
My advice is go to a good doctor...
Let me get this straight. Are you suggesting I not go to a lousy doctor?
Sounds like a bad idea to me, for reasons pointed out in other posts.
.
For a first course in CS, I think it would be hard to do better than one based on Structure and Interpretation of Computer Programs
This book takes one from zero to writing a compiler in a few hundred pages, including a chapter on writing code for register machines which gives the student a good idea of what is going on "under the hood."
To those who would say that Scheme is useless outside of academics, I would counter that once the concepts in this text are mastered, it is easy to transfer them to other languages.
DynaSoar said: ...lesioning them with the neurotoxin thought to cause Parkinson's apoptosis, MPTP.
Actually, MPTP is not involved in the pathophysiology of Parkinson's. MPTP is, however, very usefull for creating an animal model of Parkinson's disease, and has proven to be a very useful tool for the study of PD.
Consider a see-saw with one side twice as long as the other, measured from the fulcrum. The load on the short end of the see-saw is twice as massive as the load on the long end, and the see-saw balances. Motion of either load causes the other to move, such that the lighter mass moves twice as far as the heavy one.
The analogy, I believe, is that the mass of the loads would be the electric pressure, or voltage. The distance moved would be the amount of electric current, or amperage. The long side of the see-saw has half as many transformer windings as the other side, and thus a large current of small voltage on that side induces a smaller current of a larger voltage on the other side.
You are on the right track, but not quite there yet. see below.
Or maybe that analogy sucks, and it would make more sense intuitively if you used mass=current, height=voltage? Then the long side would be the more-windings side.
You are getting closer here. One of the most important points is that the "stuff" which is "flowing" must be conserved (in the physics sense). Think of electronics here: current is a "flow" of charge, and charge is conserved. Think about it for a minute and you will see how this conservation of charge leeds directly to the nodal equations for current in a circuit. Whatever you pick to "flow" in the see-saw example must be conserved if you want to use the same equations.
For example, using a hydraulic analogy, mass is conserved, so the sum of flows into a junction of pipes must equal zero. In the hydraulic example, mass=charge, mass flow=current.
Also, whatever is providing the force to drive your "stuff" must meet the definition of a "potential." I don't want to go into that now, but their is a fairly rigorous definition of what a "potential" is and voltage meets that definition. Whatever you pick as providing the force to drive your "stuff" in the see-saw analogy must meet be a "potential" if you want to use the same equations.
But the basic idea is right, yes?
Yes, getting there.
I am not familiar, though, with "coupled transducers" and domains... can you explain?
Sure, I will start.
First, think of a "transducer."
Probably the one most people are familliar with is a loudspeaker. You put electrical energy in one side of the speaker and and acoustic (kinetic) energy comes out the other end. What is really going on? You have a "flow" of one sort of "stuff" (charge) going in one end, and a "flow" of some other conserved "stuff" coming out the other end. In the process you have converted energy from one "domain" to another (electrical to kinetic). I don't want to give too much away here. Now, one can run the loudspeaker in reverse and convert kinetic energy into electrical energy (think microphone). this is a general property of "transducers." Two loudspeakers pointed at each other are an example of coupled transducers. You can put electricity into one speaker and get it out of the other, maybe not very efficiently, but one can imagine tweaking the number of windings, etc, and having something which behaves like a very inefficient trasformer.
This transformer built out of speakers is actually very similar to one built the conventional way: they are both examples of "coupled transducers," only the "domain" in the middle is differant.
More apropos to the see-saw analogy, one may think of a wrench as a trasducer. Think about what goes on when you tighten a bolt with a wrench. Think about having a second wrench on the other side of the bolt. Think about what is conserved and what is "flowing."
Accelerating objects experience a force against the direction of the acceleration vector. I can imagine transverse structural members in an assembly (read: "rocket ship") having limits to how fast lateral (from their reference frame) force changes can be accomodated. Thus, they'd have "jerk" limits.
Um, actually they do not. You are correct that your hypothetical rocket could be torn apart, but it doesn't have anything to do with a force "against the direction of acceleration." There is no such force. I think you got confused because you are thinking in terms of the non-inertial reference frame of the rocket.
A slinky with a string tied to one end can serve as a model for your hypothetical rocket. Jerk the string hard enough and you can break the slinky, but there is no force pulling any part of the slinky in the other direction.
What is really going on is that you have an object which is not perfectly rigid so it temporarily stores some of the energy you have provided with your jerk. It takes a while for the momentum (speed * mass) to "flow" from one end of the slinky to the other. If the energy density from storing this "flow" is too large, well, then you have breakage.
Keep in mind that momentum is conserved, just like energy. Of course, some of the energy you applied with your string can become heat energy rather than kinetic energy, but the momentum has nowhere else to go.
Now, if this reminds you a bit of basic electronics, you are on the right track: in both case you have some conserved "stuff" (charge in one case, momentum in the other) and a "potential" (voltage on one case, force in the other) which can move your "stuff" around, subject to certain rules.
It is no coincidence that the same equations which work for electronics work for this mechanical stuff.
Give yourself extra-credit if you can reason out which circuit element is analgous to the slinky. is it a resistor, capacitor, or inductor?
You get an "A" if you can explain how a see-saw is equivilant to an electrical transformer.
A+ if you can describe how the see-saw/transformer are two coupled transducers, and describe the flowing "stuff" and "potential" in each case, and which domains the transducers operate in.
Hey, it's for nerds, right?
Oh, IANAL.
Hey Genius! You do know that this sort of behaviour (wanting to see your dick) in a five year old is a sign of child abuse?
You were not expectected to know this at the time (I assume you were five also), but now you are.
So you pissed on the face of a five year old child who almost certainly had been sexualy abused, and you brag about it now that you are a teen/adult?
If so, you are quite sick and need help.
I hope I have been trolled.
Um, No.
It is only important to reduce the acceleration of the object you are trying to protect.
Of course, I understand that force and acceleration differ only by a scaling factor (Newton's second law: F=mA). Describing "impact force" as being "absorbed" make no sense, just as it makes no sense to describe "acceleration" as being "absorbed," just as it makes no sense to describe "temperature" as being "absorbed."
Remember that first chapter in your physics book, where they talked about "intensive" versus "extensive" properties?
This is like that.
Maybe you meant to say "energy?" Maybe not.
Dunbar is 100 percent correct on this.
A couple of common examples of physics at work,
at the same scale he describes (1.0mm to 20mm),
are motorcycle helmets and boxing gloves, which
both work quite well.
You are thinking of Mrs. Hewlett Hodges in 1954. She was bruised. The dog in Egypt is the only recorded death by meteorite.
If you use emacs you might like:
calc(scroll down the page a bit).
Calc does RPN, symbolic math, graphing, and more, all from within emacs. If you are using emacs 21.1 you need to apply a patch to the calc source before compiling. the patch can be found by doing C-h P in emacs and searching for "calc" in the displayed problems file.
[obCaveat: "Unless I'm missing the point entirely."]
Why yes! you are missing the point entirely, as others have pointed out.
Also, the they you mention is actually a he who really does know a little something about optics, not a "semi-dabbler."
Good point. Somewhat more realisticaly, if this device had any sort of longevity, it could be used as an implantable glucose sensor. With that, one could make a closed loop insulin pump. There exist pumps now, of course, but their control is open loop, total crap compared to what one could do if they had a glucose sensor.
Think about quantization for a moment: it is a many-to-one mapping of an input signal to a quantized signal. Therefor, it is an irreversible process. Another way of saying this is that there are an infinite number of signals which will have the same quantized representation.
Without going into detail, the effect of quantization can be modeled as adding an error signal to the orriginal signal. If the input signal meets certain conditions, this error signal will look like white noise. There is no way to remove this noise once the signal is quantized.
What adding more bits does is to reduce the power of this added noise signal. (it also tends to make it look more like white noise)
So, briefly, adding more bits improves the signal to noise ratio but has no effect on the frequency response.
GweeDo wrote:
In some simple tests I have done I have seen this as worth while. I have two pages I have created that might be worth a read:
I took a look at your pages. Particularly interesting is the page with the benchmarks. You had better take a look at the code gcc is generating with these options. The reason -O3 gave a factor of 20 speedup with your simple tests is because gcc is smart enough to tell that your code never does anything with the variable named "something." Because this variable is never used, gcc eliminates all of the arithmetic involving this variable when you ask it to optimize. The inner loop is completely eliminated from your code when you pass gcc -O3.
Sorry, but you seem to misunderstand the situation. What the sampling theorem tells us is that as long as the input signal is bandlimited to frequencies below one half the sampling frequency, it can be reproduced exactly by the DAC. (nb: this is for samples which have not been quantized) The reconstruction is taken care of by what is commonly known as a reconstruction filter. You are correct that the samples of a sine wave near the Nyquist frequency will look like a triangle wave, but once passed through the reconstruction filter what comes out is the original sine wave.
Note that the requirement that the signal be bandlimited means, for example, that one can not have as input a triangle wave near the nyquist frequency, because, as you correctly stated, a triangle wave of such a frequency contains harmonics which are greater than the nyquist frequency. Typicaly, they would be removed by an antialiasing filter at the input to the ADC.
Of course, I realize that it is not possible to implement an ideal reconstruction filter, and also that quantizing the signal introduces distortion which it is not possible to remove.
I must say that while working at a VA hospital last year I was very much impressed with their computer system.
The VA is the largest healthcare organization in the US, so they have the resources to build their own system. Contrary to what I was expecting, it is intuitive, just plain works, and IMHO blows away the stuff from Cerner or Meditech.
They have been working on it for twenty years, so it has the advantage of maturity, but even the newer bits such as windows interfaces running on Citrix are nice and stable.
Some background on the system can be found here.
Seems that is is mostly implemented in MUMPS so they score poorly in the buzzword complience department.
Anyways, I was just surprised that the government sometimes does seem to "get it".
I wonder how long it will be before T. Gondii evolves to affect humans?
Toxoplasma Gondii does infect humans, mostly those with AIDS.