I'm not the author of the parent post, but I'll answer you anyway.
Taxes is what you pay to the state for being a citizen in it. Being a citizen nets you quite a lot of benefits, to name just a few, in my country we get free health care and free roads. I wouldn't insist that everybody else pays taxes, but I'd definitly insist that they pay their fair share of taxes if they wanted to be a citizen in my country and/or live in it. If they don't want to pay the taxes they can go find themselves some other country to live in, and I'd be happy to be rid of the freeloaders.
It doesn't matter that you have the invented the greatest algorithm since quicksort if you can't or won't tell other people about it. If you can't convince other people how great your work is, they won't use it, and therefore you won't have contributed to the field. When you die the knowledge disappears, and you might as well never have invented the algorithm in the first place.
Therefore, it is important to convince your audiance that: - Your algorithm gets the job done. (Proofs) - Your algorithm is better and/or just different than existing algorithms. (Extensive litterature search so that you can compare your algorithm to existing ones)
Just reporting your algorithm together with a "this is how I do it" doesn't cut it. We researchers don't have the time to examine every claim somebody makes about something in our field.
I spent two months of my PhD, first trying to find an elusive proof for an obscure bit of math that I needed, that, according to the papers on the topic, was "available in the litterature", and then, after I finally gave it up, I painfully reconstructed the proof.
"Available in the litterature" ticks me off, almost as much as "... from this, it is easily seen that...".
CANbus would be a really bad choice for a control system like this one, since the capacity of the bus [bits/s] is linearly proportional to the inverse of the length of the bus. Because of this CANbus is great for cars, satellites, and other "small" systems, but horrible for large systems that require fast sampling.
It's the norm in Scandinavia, so if you just pick a random company there's a good chance they'll be just like that. Also, we usually have a shortage of people with technical degrees (Preferably a masters or equivalent. Just a bachelors won't get you far.), but it's not so pronounced with the current crisis.
If you want the expansion as a volume you could use m^3/(s*m^3), i.e., rate of volumetric expansion per volume of space. m^3/s just gives you a rate of volumetric expansion, it doesn't say anything about the volumetric expansion being faster if you look at a larger volume, or equivalently, things move faster away from you the further away from you they are, i.e., m/(s*m), which is what Hubble's Law is all about.
You can of course calculate the expansion of af known volume of space e.g. the entire universe* or just our galaxy in m^3/s, using the newly reported observation.
*As far as I know, we don't know how big the universe is, or even if the universe is finite, so we couldn't actually calculate this.
Hogshead per fortnight (equivalent to m^3/s) is the wrong unit of measurement for expressing the expansion of the universe. I'd go with 2.4 +/- 0.068 exaHz for a whimsical and opaque way of expressing it.
I loved Starship Troopers. The whole movie was a brilliant commentary to the political situation in the US, and litteraly dripping with sarcasm. I mean, they even cast the main actors for their horrible acting performance. In that sense it was very true to the book, which, in its own time, was a great commentary on fascism.
Sensors that spit out text? Who in their right mind would want that?
SCADA grabs sensor readings from the underlying control system, most likely running on some PLCs, where you have to do calculations on the data in order to feed back control values to the process being controlled.
Now, a PLC is, admittedly, sort of like the general purpose CPU's dumb brother, and the instructions it accepts are rather limited. But, for a number of reasons, they're immensely suited for their task. The single most important one being the ability to safely and easily change a program that is in production. This feature is important because control systems often have to be tuned when they're commisioned, they don't just work out of the box. You have to fiddle with constants in order to get it working, perhaps even change the structure of the control algorithm.
Because we control engineers have to fiddle with the program while it is running, we really don't want to do string to int/float/whatever conversion and the reverse when working on the PLCs. That would just be yet another place where we could scew up horribly, causing a country wide electrical blackout in the proces. It's hard enough as it is, so keep it simple, stupid!
There were two teams at the LHC that independantly came to the conclusion that there was a particle.
And, though you might have been ironic, you caught the exact reason there are two independant sets of sensors, data analysis, etc. (Everything besides the accelerator ring.) Now, a third, completely independant reproduction of the result would be golden, but until we get it we'll have to make do with just a single reproduction of the result.
Consensus has nothing to do with science. Following the scientific method is science.
And the particle the people at CERN have discovered is consistent with what we believe to be a Higgs boson, and might therefore actually be one. We haven't had time to do enough experiments to tell. The only things we know about the particle is that it's there and that it has a mass of ~126 GeV. We're assuming that it's the Higgs, because the Higgs is the only particle that is missing with a mass in that neighbourhood. (Gravitons ought to be heavier, as do dark matter, etc.)
A feedback controller is a good example. Sure you can test it against a model, but you just won't know until you've had it running against the hardware. Also, models are expensive, so clients often don't want to pay for their development, but will allow for a bit more debugging and tuning against the hardware instead.
I would recommend the same approach, i.e., write papers and get them published, but for another reason.
If, after a while, you realise that grad school just isn't you, perhaps because of a stingy professor or something along those lines, then, when you quit, you'll still have your publications even if you didn't get your degree. And, since the papers have been through the peer review process, you'll have the word of your peers that you are a capable researcher.
That really depends on the mission. Powering directly towards Mars from Earth when they are the closest together is a rather inefficient (fuel-wise) transfer.
It is a "solved" problem. But that doesn't make it easy. Far from it.
When controlling an object like this you'd usually use a state-space controller, most likely an optimal controller.
First you need a mathematical model of the system. Since this is almost entirely a kinematic system they've most likely constructed a non-linear model using first order principles and then derived a first order approximation of it. The model won't be completely accurate, so they'll have to test it up against the actual system to see if it is "good enough". (Where the ability to judge if a model is "good enough" comes with practice.)
Then, using the linear model, you can construct an observer so that you'll be able to estimate the states from the actual measurements. In this case I'd probably go for a Kalman filter.
Finally you can synthesize you optimal controller, that generates the control signal from the estimated state.
As far as I can tell, this is the first untethered flight of this system. Therefore they haven't had the chance to test if their mathematical model is correct, since there's a good chance the tether will change the dynamics of the systems, and errors in the model will result in a bad estimator and a bad controller, that, because the estimator is bad, will be fed false information. Getting reality to conform to the used math is no simple feat.
...and that was just the mathematical core of the control system. All the calculations has to run on a RT-OS, and all the electrical components, e.g. computers, sensors and actuators, have to work perfectly. Add to that all the various start up procedures that also have to be controlled, the trajectory calculations, etc. etc.
Slashdot Mirror
I'm not the author of the parent post, but I'll answer you anyway.
Taxes is what you pay to the state for being a citizen in it. Being a citizen nets you quite a lot of benefits, to name just a few, in my country we get free health care and free roads. I wouldn't insist that everybody else pays taxes, but I'd definitly insist that they pay their fair share of taxes if they wanted to be a citizen in my country and/or live in it. If they don't want to pay the taxes they can go find themselves some other country to live in, and I'd be happy to be rid of the freeloaders.
Why was this modded flamebait?
Azure is webscale? I never knew!
The branch of engineering you're looking for is called "Control Theory".
Rushed and buggy. I usually buy games that aren't even fully developed yet, but look promising.
Communication skills matter in science!
It doesn't matter that you have the invented the greatest algorithm since quicksort if you can't or won't tell other people about it. If you can't convince other people how great your work is, they won't use it, and therefore you won't have contributed to the field. When you die the knowledge disappears, and you might as well never have invented the algorithm in the first place.
Therefore, it is important to convince your audiance that:
- Your algorithm gets the job done. (Proofs)
- Your algorithm is better and/or just different than existing algorithms. (Extensive litterature search so that you can compare your algorithm to existing ones)
Just reporting your algorithm together with a "this is how I do it" doesn't cut it. We researchers don't have the time to examine every claim somebody makes about something in our field.
Thank you!
I spent two months of my PhD, first trying to find an elusive proof for an obscure bit of math that I needed, that, according to the papers on the topic, was "available in the litterature", and then, after I finally gave it up, I painfully reconstructed the proof.
"Available in the litterature" ticks me off, almost as much as "... from this, it is easily seen that ...".
CANbus would be a really bad choice for a control system like this one, since the capacity of the bus [bits/s] is linearly proportional to the inverse of the length of the bus. Because of this CANbus is great for cars, satellites, and other "small" systems, but horrible for large systems that require fast sampling.
Oh! That's an eye opener!
As a scandinavian I never though of that. The health system in the US is just that alien to me I guess.
It's the norm in Scandinavia, so if you just pick a random company there's a good chance they'll be just like that. Also, we usually have a shortage of people with technical degrees (Preferably a masters or equivalent. Just a bachelors won't get you far.), but it's not so pronounced with the current crisis.
If you want the expansion as a volume you could use m^3/(s*m^3), i.e., rate of volumetric expansion per volume of space. m^3/s just gives you a rate of volumetric expansion, it doesn't say anything about the volumetric expansion being faster if you look at a larger volume, or equivalently, things move faster away from you the further away from you they are, i.e., m/(s*m), which is what Hubble's Law is all about.
You can of course calculate the expansion of af known volume of space e.g. the entire universe* or just our galaxy in m^3/s, using the newly reported observation.
*As far as I know, we don't know how big the universe is, or even if the universe is finite, so we couldn't actually calculate this.
Hogshead per fortnight (equivalent to m^3/s) is the wrong unit of measurement for expressing the expansion of the universe. I'd go with 2.4 +/- 0.068 exaHz for a whimsical and opaque way of expressing it.
Nope, I saw it at the local cinema, I don't know, perhaps a couple of months ago?
I expected it to be a horrible movie, but it turned out to be a quite enjoyable B-movie instead.
Seriously?
I loved Starship Troopers. The whole movie was a brilliant commentary to the political situation in the US, and litteraly dripping with sarcasm. I mean, they even cast the main actors for their horrible acting performance. In that sense it was very true to the book, which, in its own time, was a great commentary on fascism.
Sensors that spit out text? Who in their right mind would want that?
SCADA grabs sensor readings from the underlying control system, most likely running on some PLCs, where you have to do calculations on the data in order to feed back control values to the process being controlled.
Now, a PLC is, admittedly, sort of like the general purpose CPU's dumb brother, and the instructions it accepts are rather limited. But, for a number of reasons, they're immensely suited for their task. The single most important one being the ability to safely and easily change a program that is in production. This feature is important because control systems often have to be tuned when they're commisioned, they don't just work out of the box. You have to fiddle with constants in order to get it working, perhaps even change the structure of the control algorithm.
Because we control engineers have to fiddle with the program while it is running, we really don't want to do string to int/float/whatever conversion and the reverse when working on the PLCs. That would just be yet another place where we could scew up horribly, causing a country wide electrical blackout in the proces. It's hard enough as it is, so keep it simple, stupid!
You're right, thanks!
I haven't touched quantum physics in quite some years, so I'm rather rusty.
There were two teams at the LHC that independantly came to the conclusion that there was a particle.
And, though you might have been ironic, you caught the exact reason there are two independant sets of sensors, data analysis, etc. (Everything besides the accelerator ring.) Now, a third, completely independant reproduction of the result would be golden, but until we get it we'll have to make do with just a single reproduction of the result.
Consensus has nothing to do with science. Following the scientific method is science.
And the particle the people at CERN have discovered is consistent with what we believe to be a Higgs boson, and might therefore actually be one. We haven't had time to do enough experiments to tell. The only things we know about the particle is that it's there and that it has a mass of ~126 GeV. We're assuming that it's the Higgs, because the Higgs is the only particle that is missing with a mass in that neighbourhood. (Gravitons ought to be heavier, as do dark matter, etc.)
A feedback controller is a good example. Sure you can test it against a model, but you just won't know until you've had it running against the hardware. Also, models are expensive, so clients often don't want to pay for their development, but will allow for a bit more debugging and tuning against the hardware instead.
Misclicked while moderating.
I would recommend the same approach, i.e., write papers and get them published, but for another reason.
If, after a while, you realise that grad school just isn't you, perhaps because of a stingy professor or something along those lines, then, when you quit, you'll still have your publications even if you didn't get your degree. And, since the papers have been through the peer review process, you'll have the word of your peers that you are a capable researcher.
That really depends on the mission. Powering directly towards Mars from Earth when they are the closest together is a rather inefficient (fuel-wise) transfer.
That was the last capsule they designed. This one looks a bit more like we're used to. Which incidentally is also why they call it "apollo-like".
It is a "solved" problem. But that doesn't make it easy. Far from it.
When controlling an object like this you'd usually use a state-space controller, most likely an optimal controller.
First you need a mathematical model of the system. Since this is almost entirely a kinematic system they've most likely constructed a non-linear model using first order principles and then derived a first order approximation of it. The model won't be completely accurate, so they'll have to test it up against the actual system to see if it is "good enough". (Where the ability to judge if a model is "good enough" comes with practice.)
Then, using the linear model, you can construct an observer so that you'll be able to estimate the states from the actual measurements. In this case I'd probably go for a Kalman filter.
Finally you can synthesize you optimal controller, that generates the control signal from the estimated state.
As far as I can tell, this is the first untethered flight of this system. Therefore they haven't had the chance to test if their mathematical model is correct, since there's a good chance the tether will change the dynamics of the systems, and errors in the model will result in a bad estimator and a bad controller, that, because the estimator is bad, will be fed false information. Getting reality to conform to the used math is no simple feat.
...and that was just the mathematical core of the control system. All the calculations has to run on a RT-OS, and all the electrical components, e.g. computers, sensors and actuators, have to work perfectly. Add to that all the various start up procedures that also have to be controlled, the trajectory calculations, etc. etc.
Since I'm from Europe I'd like to add: Kudos to the people of the US for funding it!