Look, most job interviews are hopeless. Not only is the interviewer barred from asking the REALLY important questions, but the interviewee is putting on a total ACT and trying to be more devious than Bill Clinton in front of the BJ inquiry comittee.
So with the wrong namby-pamby questions and misleading answers, what's the point of any followup?
On the other hand, there3's the new "behavioral questions", which try to get at the really important topics without coming right out and asking "are you not a jerk, a goofoff and an idiot to boot?" But thena gain, there are plenty of web sites with stock answers to the standard behavioral questions, so it's trivially easy to deceive on these too.
It's been my experience if somebody totally bombs and thinks they're hot stuff, they're far too clueless to beleive any feedback anyway.
>Firstly, gold plated speaker wire isn't gold plated to improve the capacitance or resistance properties of the wire - it's done to prevent corrosion.
Wrongo, Bub. Wire strands are usually tin-plated to reduce corrosion and improve solderability.
Nobody, but nobody gold-plates wire, even for the most demanding aerospace and military applications. I've taken apart Titan missle guidance computers, Mil-spec avionics, even old satellite guts and havent found an inch of gold-plated wire.
Now connector edges and IC and transistor leads that are going into sockets are often gold-plated. And I've even seen a very few Sprague electrolytic capacitors, MIL-spec, maybe one in a million, with gold-plated leads. But not wire.
> and tend to introduce a small amount of phase shift into whatever AC signal you're passing through them.
Wrongo again Bub. As you should know, the phase shift is proportional to the capacitance, and NOTHING ELSE. So a 100uF electrolytic capacitor will have EXACTLY the same phase shift as a polypropylene capacitor of the same value. And doubly false, as electrolytics are hardly ever used anywhere in their phase-shifting frequency range-- they're almost always used at frequencies where they're nearly dead shorts to AC and near zero phase angle. Exceptioin-- old cruddy speakers used non-polarized electrolytics in their phase-shifting range, but that's about it.
>And yes I am an electrical engineer!:D
Yep, I've met way too many EE's that don't recall the basic physical facts.
Do alittle math, and this engine doesnt look very good:
First calculate how many horsepower you get per cubic inch. An auto engine does about 1/2 HP per cubic inch. A good old radial airplane engine, say the R4360, gives about 3/4 HP per cubic inch. Now do the math for this diesel-- about 1/14th of a HP per cubic inch. That's very low volumetric efficiency.
That's mor ethan a theoretical issue-- each cubic inch of displacement has to be surrounded by a corresponding cubic inch of iron. Iron is heavy. calculate the horsepower per pound-- for a car engine it's about three pounds per horsepoer. For the R4360 it's down to about ONE horsepower per pound. For this diesel, it's a whopping FOURTY SIX POUNDS PER HORSEPOWER. This diesel is over FORTY times heavier per pound than a good aircraft engine.
Engines do not scale up well-- even at this really low volumetric and weight efficiency, the engine needs sophisticated piston and head cooling systems just to keep it from melting down.
>Those little hairdryers deliver up to 50 pounds of thrust and sell for $3000-$5000.
Thanks! Some facts at last. I stand corrected-- he may have been flying.
But please realize that these things are doubly inefficient--
Jet engines work best at speeds comparable to their exhaust-- at typical human flight sppeds under 100MPH only a small fraction of the thrust is delivered as useful power.
Scaled-down jet engines of this size are intrinsically inefficient.
Combine these two gotchas and you have this situation-- 50lbs of thrust at 100MPH is about 6 horsepower.
6 horsepower for $3K to $5K is a factor ot ten or so higher in price, and a similar factor lower in efficiency than using internal combustion and propeller technology.... You're paying a very high premium for the gee-whizzyness of jet power.
Just on general principles, it's unlikely he's really flying, as in having enough thrust to overcome drag.
Jet engines do not scale down very well-- somewhere around the size of a kosher salami the friction exceeds the power generated, the thrust to weight ratio drops very quickly, making the thing little more than a swooshing kerosene heater.
We need some more facts, such as jet engine thrust, specific fuel consumption, and cost.
Is it just me, or does this article sound like random babbling? Nowhere did I see any explanation of what CTCP is, what it does, how it does it, or why it's a good or bad thing. Instead there's lots of uninformed speculation. Apparently it has something to do with bigger TCP windows and/or better or throttled thruput. But we end up more mystified than when we came in.
Doing some advanced math, it looks like they're not willing to spend two tenths of one percent of the total on this foot soldier stuff. And parents are having to send kevlar vests and helmet liners to their kids cause the Army is too cheap and/or slow. Kinda bad for morale if you ask me.
The current used vegetable oil was currently being thrown away, lubricating landfills I guess.
But it's not, it's already going into special dumpsters, which I suspect get dumped into recycling systems that filter the oil and resell it for non-human consumption by mouth uses, such as candles, ointments, plastic feedstocks, greases, etc....
there were a LOT of veg oil per person being used. But if you think about it, it's doubtful that you're using more than a cup of oil a day, which doesnt translate into a significant amount of energy. Most people use at least a gallon of gas a day-- offsetting that with a cup of veggie oil is not a big win.
And let's not forget a good percentage of that oil is effectively consumed in the process of shipping, filtering, and re-refining the oil.
p.
Perhaps it would be better overall to nip this "waste" in the bud, and we all cut back on our consumption of fried foods. Less waste and less "waist"-- a two-'fer
Perhaps we need to clarify the various flavors of vaporware, distinguished by intents and causes:
(1) Deceit-o-ware: Marketing announces a "product" in order to discourage competitors, stake out mindshare, commit the partners and developers, and other dishonorable reasons. ( Taligent, others )
(2) Wish-o-ware: Developers promise to enhance a product, not realizing the current code isnt extendable. ( Copeland )
(3) Bloat-o-ware: Soo many promised features, the resulting code is too embarrasingly complex or slow to ever be released. ( Cairo, SQL file system,.NET code in the OS )
Now #1 is totally indefensible, but #2 and 3 are more likely unintended consequences of good intentions.
A solar cell that needs "concentrators" means you spend twice, once for the expensive cell, then again for the mirror to concentrate the light. Then again for motors to rotate the mirror so you don't have this expensive solar cell lying in the shadows.
Now estimate the cost of a mirror, per square meter, plus the cost of keeping it clean, plus the cost of the motors to move the mirror, plus the cost of making everything strong enough to survive for a decade or two.
You're going to end up with a figure of several hundred dollars per square meter. Now a square meter's work of power, once converted to electrical power, is only worth about $30 per year. Which doesnt even pay the interest on the principal.
Probably has effects like other microwaves. The military found out long ago that exposure to microwaves increases the incidence of cataracts. That's why there are rather low exposure limits-- a few milliwatts per cm^2.
I was innocently looking for some bar-code scanners ( I was hoping to label my books with bar codes ), and bid on a batch of 9 of them on eBay.
Got them for under $1 each.
To my dismay, they can't read standard bar codes.
To my amusement, and dismay, I figured out WHY they wouldnt read standard bar codes.
Some airline sold them to a liquidator. With their custom code in the flash memory to scan their baggage and boarding pass tags.
It wasnt too hard to learn all this. Every scanner had several stickers on it with diagonal red stripes and phrases like
"/// SECURITY DEVICE #xxxxxxxx/// "
"/// USER MUST HAVE SIGNED CONFIDENTIALITY AGREEMENT A8R55-2/// "
"/// FIRING OFFENSE TO REMOVE FROM RED ZONE (UNION HBK, PG 37)/// "
"/// DEADULUS & EARHART AIRLINE CUSTOM FIRMWARE VERSION 1.22"/// .
I wonder what their thought processes where?, something like:
These old hand scanners are getting dirty, let's throw them away.... Wait, there's probably a few cents of value left in them, lets sell them to that liquidatior, you know, the one that pays us $20 per pallet of old stuff.
Never mind these will help somebody impersonate a baggage loader or gate agent.
Never mind someone can use them to validate that their tag-faking software is printing out valid tags.
I was looking for some bar-code scanners and bid on a batch of 9 of them on eBay.
Got them for under $1 each.
To my dismay, they can't read standard bar codes. ( I was hoping to label my books with bar codes )
To my amusement, and dismay, I figured out WHY they wouldnt read standard bar codes.
Some airline sold them to a liquidator. With their custom code in the flash memory to scan their baggage and boarding pass tags.
I wonder what their thought processes where?, something like:
These old hand scanners are getting dirty, let's throw them away.... Wait, there's probably a few cents of value left in them, lets sell them to that liquidatior, you know, the one that pays us $20 per pallet of old stuff.
Never mind these will help somebody impersonate a baggage loader or gate agent.
Never mind someone can use them to validate that their tag-faking software is printing out valid tags.
And why would anybody use this paper? It's likely to cost many times more than regular paper, and unlikely to ever be reused-- the slightest curl and it won't feed properly the next time thru most printers. And you're likely to need a separate printer with the special paper and the "special ink". It's going to take many, many years for any "savings" to pay for the cost and inconveniences.
Not to mention confidentiality issues if there's any chance the old images can be ressurected. it certainly couldnt be used in most businesses, legal, govt, or medical practices.
"Thermionic energy" sounds really wizzy, until you think about it a bit. You are trying to get electrons to boil off a hot surface and plonk themselves onto a cooler collector plate. Which means you need a hot emitter, a cool colector, and in between something that will pass electrons, but not too much heat. Basically, a losing proposition, as anything that passes electrons is almost by definition an excellent conductor of heat. Try to think of somethign that conducts electricity but insulates heat. Hard to come up with isnt it?
There are thermionic devices already around, you're probably looking at one. Vacuum tubes and CRT's are thermionic devices. Not very powerful ones--a typical tube only boils off microamps of current at under a volt, while requiring several watts of electrical power to heat the emitter. Not very impressive.
I'm amazed at the claim that IBM's marketing sunk OS/2. Their marketing may have been marginal , but there were many other deeper reasons OS/2 didnt make it:
OS/2 was tied to the old 80286 architecture, as IBM was making lots of PS/2 boxes with 286's. That was a major millstone around its neck-- it could never do any of the clever real to protected mode switching and emulation that Windows 3.1 could do.
IBM had a lot of programmers in the UK assigned to OS/2. Distance, before the Internet, was a big hindrance.
The UK crew had some very strange ideas, many of them impractical and antithetical to the PC world.
OS/2 first came out with a very crippled "text only" version, with most of the overhead but none of the benefits of the GUI version. A great way to make a poor OOB experience.
OS/2 was not torpedoed by Microsoft, in fact for the first year or so Bill gates worked quite hard to fix many of the worst design choices in OS/2.
I suspect 97% of families cannot reduce their electricity usage by that much. If you have children, there are clothes and dishes to wash and dry. Using human labor for this is not an efficient use of human resources. In cold places there are furnace fans to turn, or a lot of time and expense in gathering and chopping or buying wood. One can cut back maybe 50%, but 90% is probably unattainable.
The cost of running power to the house, although considerable, is not a lost investment. Eventually the house will be sold, and without AC power, the house is likely to be unsellable, unless you drop the price by at least the cost of running power to it. So there's no net benefit in the long run, and you're losing the advantages ofd having power there in the short run.
Storage batteries are fine, except they require periodic attention and total replacement every few years. After a few hundred cycles even deep-cycle batteries lose a lot of their storage capacity, which is never grerat to begin with. That's a lot of $, many times more than the cost of the equivalent AC power.
Again, I respect those folks, but it's not an economic decision by any means.
>at $10,000 per installation (in Canadian funds), it only takes about three to five years before you've saved that much through not buying electricity from the power company.
10K Canadian is about $8,800 US.
For that you can buy a solar power system that can generate about 5KWh per day. That's about 25 cents worth.
Not many households can run off that little power-- the US average is about 30KWh per day.
At 25 cents a day, you're saving about $75 a year. But if you'd kept the $7K in a bank at 3% interest, you'd have made $210.
And you would be able to buy three times the energy, plus not have the cost of maintaining the system, or the risk of no power after a few cloudy days.
Yep, I've seen those claims of "paying it off after 3 years" too. Totally bogus of course, but it sells solar panels.
>This is Slashdot. Provide us the numbers and research links for your theory. Someone else will crosscheck your calculations and debunk you. Or not.
Okay:
First you have to figure out how to make a steerable reflector at low cost, yet stand up to wind and rain.
First observation:: the weight and cost of a steerable reflector go up as the cube of the diameter, but the solar collecting area only go up as the square. So you want to make them big enough so the fixed overhead costs are not a big consideration, but not too big so the cube factor gets too big.
Note: this makes a non-starter of the idea of having just one big honkin reflector.
Let's go with the cost of a satellite dish-- they're doing roughly the same job. A 3 meter dish costs about $8000 retail, let's guess $4000 wholesale.
So we have a 10 meter^2 collecting surface. Sunlight is about 1KW per square meter, so we have 10KW on a sunny day. Subtract half for nighttime, subtract another third for clouds and rain, and we're down to 1/6th of 10KW, or 1,600 watts thermal average.
If we could aim that at a photovoltaic cell, with 13% efficiency, we'd get 208 watts. In a year we'd get about 1822 kilowatt-hours. At wholesale rates, that's about $72 a year.
if you aimed it at a steam generator, you might get 20% efficiency, still under $100 a year.
---
Let's say this whole shebang is going to last 20 years.
So every year you have to pay back 1/20th of the principal, plus interest, just to break even after 20 years. Let's say you have a friendly banker that will loan you the money at 7% interest (very very low for an unsecured loan of high risk)!
If the photocells and steam plant are free, just for each dish you have to pay back $200 of principal and
$280 of interest. But you're only making $70 to $100. You're about FIVE TIMES below break-even costs, actually much worse as it's hard to imagine a dish needing less than $70 a year of maintenance. And we're assuming free solar cells or steam plant.
This technology just aint going to fly anytime soon.
Slashdot Mirror
Aero and space are very unforgiving of human coding errors.
So with the wrong namby-pamby questions and misleading answers, what's the point of any followup?
On the other hand, there3's the new "behavioral questions", which try to get at the really important topics without coming right out and asking "are you not a jerk, a goofoff and an idiot to boot?" But thena gain, there are plenty of web sites with stock answers to the standard behavioral questions, so it's trivially easy to deceive on these too.
It's been my experience if somebody totally bombs and thinks they're hot stuff, they're far too clueless to beleive any feedback anyway.
Wrongo, Bub. Wire strands are usually tin-plated to reduce corrosion and improve solderability.
Nobody, but nobody gold-plates wire, even for the most demanding aerospace and military applications. I've taken apart Titan missle guidance computers, Mil-spec avionics, even old satellite guts and havent found an inch of gold-plated wire.
Now connector edges and IC and transistor leads that are going into sockets are often gold-plated. And I've even seen a very few Sprague electrolytic capacitors, MIL-spec, maybe one in a million, with gold-plated leads. But not wire.
> and tend to introduce a small amount of phase shift into whatever AC signal you're passing through them.
Wrongo again Bub. As you should know, the phase shift is proportional to the capacitance, and NOTHING ELSE. So a 100uF electrolytic capacitor will have EXACTLY the same phase shift as a polypropylene capacitor of the same value. And doubly false, as electrolytics are hardly ever used anywhere in their phase-shifting frequency range-- they're almost always used at frequencies where they're nearly dead shorts to AC and near zero phase angle. Exceptioin-- old cruddy speakers used non-polarized electrolytics in their phase-shifting range, but that's about it.
>And yes I am an electrical engineer! :D
Yep, I've met way too many EE's that don't recall the basic physical facts.
First calculate how many horsepower you get per cubic inch. An auto engine does about 1/2 HP per cubic inch. A good old radial airplane engine, say the R4360, gives about 3/4 HP per cubic inch. Now do the math for this diesel-- about 1/14th of a HP per cubic inch. That's very low volumetric efficiency.
That's mor ethan a theoretical issue-- each cubic inch of displacement has to be surrounded by a corresponding cubic inch of iron. Iron is heavy. calculate the horsepower per pound-- for a car engine it's about three pounds per horsepoer. For the R4360 it's down to about ONE horsepower per pound. For this diesel, it's a whopping FOURTY SIX POUNDS PER HORSEPOWER. This diesel is over FORTY times heavier per pound than a good aircraft engine.
Engines do not scale up well-- even at this really low volumetric and weight efficiency, the engine needs sophisticated piston and head cooling systems just to keep it from melting down.
Thanks! Some facts at last. I stand corrected-- he may have been flying.
But please realize that these things are doubly inefficient--
Combine these two gotchas and you have this situation-- 50lbs of thrust at 100MPH is about 6 horsepower. 6 horsepower for $3K to $5K is a factor ot ten or so higher in price, and a similar factor lower in efficiency than using internal combustion and propeller technology.... You're paying a very high premium for the gee-whizzyness of jet power.
But unfortunately the correlation may not imply causation. i.e. people who live longer drink more, but not vice-versa.
Lotsa possible ways to spoil things.
Should take about five lines of code to fix, in any firewall that really want to.
Is it just me, or does this article sound like random babbling? Nowhere did I see any explanation of what CTCP is, what it does, how it does it, or why it's a good or bad thing. Instead there's lots of uninformed speculation. Apparently it has something to do with bigger TCP windows and/or better or throttled thruput. But we end up more mystified than when we came in.
Doing some advanced math, it looks like they're not willing to spend two tenths of one percent of the total on this foot soldier stuff. And parents are having to send kevlar vests and helmet liners to their kids cause the Army is too cheap and/or slow. Kinda bad for morale if you ask me.
- The current used vegetable oil was currently being thrown away, lubricating landfills I guess.
- But it's not, it's already going into special dumpsters, which I suspect get dumped into recycling systems that filter the oil and resell it for non-human consumption by mouth uses, such as candles, ointments, plastic feedstocks, greases, etc....
- there were a LOT of veg oil per person being used. But if you think about it, it's doubtful that you're using more than a cup of oil a day, which doesnt translate into a significant amount of energy. Most people use at least a gallon of gas a day-- offsetting that with a cup of veggie oil is not a big win.
- And let's not forget a good percentage of that oil is effectively consumed in the process of shipping, filtering, and re-refining the oil.
p. Perhaps it would be better overall to nip this "waste" in the bud, and we all cut back on our consumption of fried foods. Less waste and less "waist"-- a two-'ferPerhaps we need to clarify the various flavors of vaporware, distinguished by intents and causes: (1) Deceit-o-ware: Marketing announces a "product" in order to discourage competitors, stake out mindshare, commit the partners and developers, and other dishonorable reasons. ( Taligent, others ) (2) Wish-o-ware: Developers promise to enhance a product, not realizing the current code isnt extendable. ( Copeland ) (3) Bloat-o-ware: Soo many promised features, the resulting code is too embarrasingly complex or slow to ever be released. ( Cairo, SQL file system, .NET code in the OS )
Now #1 is totally indefensible, but #2 and 3 are more likely unintended consequences of good intentions.
A solar cell that needs "concentrators" means you spend twice, once for the expensive cell, then again for the mirror to concentrate the light. Then again for motors to rotate the mirror so you don't have this expensive solar cell lying in the shadows.
Now estimate the cost of a mirror, per square meter, plus the cost of keeping it clean, plus the cost of the motors to move the mirror, plus the cost of making everything strong enough to survive for a decade or two.
You're going to end up with a figure of several hundred dollars per square meter. Now a square meter's work of power, once converted to electrical power, is only worth about $30 per year. Which doesnt even pay the interest on the principal.
Probably has effects like other microwaves. The military found out long ago that exposure to microwaves increases the incidence of cataracts. That's why there are rather low exposure limits-- a few milliwatts per cm^2.
To Pluto in an hour would take about 6 times the speed of light. Not likely to happen anytime soon.
Got them for under $1 each.
To my dismay, they can't read standard bar codes.
To my amusement, and dismay, I figured out WHY they wouldnt read standard bar codes.
Some airline sold them to a liquidator. With their custom code in the flash memory to scan their baggage and boarding pass tags.
It wasnt too hard to learn all this. Every scanner had several stickers on it with diagonal red stripes and phrases like
"/// SECURITY DEVICE #xxxxxxxx/// "
"/// USER MUST HAVE SIGNED CONFIDENTIALITY AGREEMENT A8R55-2/// "
"/// FIRING OFFENSE TO REMOVE FROM RED ZONE (UNION HBK, PG 37)/// "
"/// DEADULUS & EARHART AIRLINE CUSTOM FIRMWARE VERSION 1.22"/// .
I wonder what their thought processes where?, something like:
Got them for under $1 each.
To my dismay, they can't read standard bar codes. ( I was hoping to label my books with bar codes )
To my amusement, and dismay, I figured out WHY they wouldnt read standard bar codes.
Some airline sold them to a liquidator. With their custom code in the flash memory to scan their baggage and boarding pass tags.
I wonder what their thought processes where?, something like:
Not to mention confidentiality issues if there's any chance the old images can be ressurected. it certainly couldnt be used in most businesses, legal, govt, or medical practices.
There are thermionic devices already around, you're probably looking at one. Vacuum tubes and CRT's are thermionic devices. Not very powerful ones--a typical tube only boils off microamps of current at under a volt, while requiring several watts of electrical power to heat the emitter. Not very impressive.
Then it's not an antenna.
It's a resonant circuit with high circulating currents.
These kind of fields drop off as the cube of the distance, making them mostly useless.
Senor Marconi punctured this scheme in 1902.
I thought we'd advanced a bit since then, apparently not.
AFAIK Maxwell's equations havent changed in 130 years.
If you read TFA you see this has only been simulated.
Power transmission follows well-known laws, as a rough estiamte,
power transmission efficiency at 6.4 MHz is going to be about 0.01% at a few meters.
There's no way for an antenna to "reabsorb" the uncollected power.
And "Resonance" is over 100 years old, well explored, and has nothing to do with improved power transfer and "non-radiating" antenas.
What nonsense.
Again, I respect those folks, but it's not an economic decision by any means.
Not many households can run off that little power-- the US average is about 30KWh per day.
At 25 cents a day, you're saving about $75 a year. But if you'd kept the $7K in a bank at 3% interest, you'd have made $210.
And you would be able to buy three times the energy, plus not have the cost of maintaining the system, or the risk of no power after a few cloudy days.
Yep, I've seen those claims of "paying it off after 3 years" too. Totally bogus of course, but it sells solar panels.
Okay:
First you have to figure out how to make a steerable reflector at low cost, yet stand up to wind and rain.
First observation:: the weight and cost of a steerable reflector go up as the cube of the diameter, but the solar collecting area only go up as the square. So you want to make them big enough so the fixed overhead costs are not a big consideration, but not too big so the cube factor gets too big. Note: this makes a non-starter of the idea of having just one big honkin reflector.
Let's go with the cost of a satellite dish-- they're doing roughly the same job. A 3 meter dish costs about $8000 retail, let's guess $4000 wholesale.
So we have a 10 meter^2 collecting surface. Sunlight is about 1KW per square meter, so we have 10KW on a sunny day. Subtract half for nighttime, subtract another third for clouds and rain, and we're down to 1/6th of 10KW, or 1,600 watts thermal average.
If we could aim that at a photovoltaic cell, with 13% efficiency, we'd get 208 watts. In a year we'd get about 1822 kilowatt-hours. At wholesale rates, that's about $72 a year.
if you aimed it at a steam generator, you might get 20% efficiency, still under $100 a year. --- Let's say this whole shebang is going to last 20 years.
So every year you have to pay back 1/20th of the principal, plus interest, just to break even after 20 years. Let's say you have a friendly banker that will loan you the money at 7% interest (very very low for an unsecured loan of high risk)!
If the photocells and steam plant are free, just for each dish you have to pay back $200 of principal and $280 of interest. But you're only making $70 to $100. You're about FIVE TIMES below break-even costs, actually much worse as it's hard to imagine a dish needing less than $70 a year of maintenance. And we're assuming free solar cells or steam plant.
This technology just aint going to fly anytime soon.