Slashdot is powered by your submissions, so send in your scoop

 



Forgot your password?
typodupeerror

Comment Don't write it off just yet... (Score 1) 728

If you're very happy with what you do and such, great, but don't shut college out based on that cost analysis. I finished my BS with $10k in debt and could have done it with none. Your college costs are not equal to your final debt. I did a community college AS degree and then finished my BS at a state school. (I did work, 20 hours a week at ~$6-7/hour.) There are many good schools, so you can filter them based on the best cost to education ratio and come up with reasonable tuition rates - just google it and see what you find. And college life can be a lot of fun depending on what you make of it.

I did a technical degree in engineering. Six years after graduating (B.S.), my salary equates to $35 an hour, I have health insurance, a month a year off, and other benefits, and in this career path, I expect my salary will double over the course of 15-20 years and then cap out. Today this buys me a nice new home, a nice new sports car, and I have enough money left over to take vacations and to save as well. Importantly, I generally like what I do at work every day and enjoy talking with and learning from intelligent peers.

If you're on the fence, remember that you can always do community college part time, right now, so you don't need to quit the job you seem to be happy with. It certainly wouldn't hurt you. If you don't like it that well, just finish the 2 year degree so you get something out of it and call it a day. You'll only have spent a few grand, you'll have learned a few things along the way, and from then on you can list a college degree if you ever need to find a new job years down the road.

Comment Limited world view (Score 4, Insightful) 728

What does going to college tell you about a persons character? It tells me they're submissive to authority and lack initiative, which is great for many roles. A person who rejects the idea that he should sit at the feet of the wise old professor and learn and instead go out into the world and get to work making waves might not suck up what you give them and ask you if they're doing ok.

Mediocrity and reliability go to school. The worst and best reject it.

You can go about making your waves. Make big ones - I genuinely hope you do and you have a great time.

I analyze and evaluate the structural performance of supersonic fighter jets, which make waves, but of a different type entirely. My values and goals simply don't match yours.

Those of us who wish to be movers and shakers in STEM must first know the basic building blocks, and those are easily learned from the wise old professors who built these things before us. I strive for reliability in specific ways and pick an choose which authorities it is in my best interest to submit to. If you think my peers and I lack initiative and must be "mediocre," I think you need to open your eyes to different ways of viewing the world.

Comment Re:I'm getting a different message (Score 1) 728

I'm starting to think that a large part of the problem must be the costs varying heavily by region of the country.

My parents couldn't pay for my school, so I followed a similar path to yours. I went to a local community college at $1k a year, then I moved across the country specifically to get the best value on school while I earned my BS. I finished it with $10k in total debt. My tuition and books ran about $5000 a year for the last two years, and I worked in retail for 20 hours a week to cover my living expenses. I had seriously considered several Ivy League schools, but I couldn't justify spending the ~$20-30k/year when all I would get for it is a Bachelor's degree. My wife's medical school costs were lower than that.

Why don't families take a quick look at college costs and rankings together to find a good fit -- is it simply an issue of not knowing any better until it's too late?

Comment big brother (Score 1) 98

We went on a short self-guided car tour of Scotland this summer and were blown away at the number of cameras on the roadway. Many of the main roads had one or more speed camera covering all lanes of traffic every mile for tens of miles. I had no intention of doing any wrong, but all the 'invasion of privacy' bells were going off in my head.

I never got feelings like the system was going to be abused in any type of near term scenario, but I couldn't help but think how easy it would be for a Stalin type leader to use that envoronment to make inconvenient people disappear. In many places it is technically legal (*not that it happens*) for a police officer to bring you to jail for speeding or neglecting a turn signal during a lane change. I frequently hear the average citizen of the US commits one felony a day by being normal.

Comment Releases poisons - misrepresents the design (Score 5, Informative) 237

You seem to be under the impression fires in composite aircraft pose a risk of poisoning or harming passengers.

It's not that simple though. Composites (FRP) are made from a fiber and a resin, which can be thought of like a glue. Most plastics can be used as a resin. On an aircraft, they use many different resins in different places as they are tailored to the local requirements. Also, these plastics are subjected to a number of tests that are used to determine toxicity in a few reasonable ways; most of them concentrate on what happens when we burn the plastic.

Near passengers, they have requirements ensuring the parts are self-extinguishing in a short (1 minute) time frame and have no toxicity in their smoke (The flammability test is UL 94, V0 is a typical requirement; I forget the smoke and toxicity test numbers I've used). So the plastic that holds your luggage above your head is made of a less weight-efficient material because it must meet design requirements focused on passenger safety in the event of a cabin fire. And of course, in the middle of the wing, it doesn't much matter if the smoke from a fire would make a passenger sick--passengers aren't anywhere near there--but fuel is probably nearby, so the design requirements and fail-safe measures for flammability and smoke are different there and in other zones of the aircraft.

In the paper you cited, note that the focus was on emergency response personnel. If as a passenger you're exposed to such an explosion, respiration of the fibers that carry potentially toxic plastics isn't the top concern - if you're inhaling that, I would be wondering what punched a hole in the fuselage and how many people are dead. The respiration and other hazards are a big deal to a ground crew or fire department who would put out non-crash-related fires. But the words in bold, "A bigger issue: When composite burns it releases poisons," are easy to misinterpret as a major passenger safety hazard unique to this aircraft.

Comment drawbacks, fuel maps (Score 1) 375

Thank you for mentioning the details of what the damage means and for mentioning energy density. That's a real-world drawback we experience immediately. Ethanol does create domestic supply chains for oil for many nations though, and it's always beneficial to have a variety of effective methods to meet major demands of our societies. While the octane rating is higher for ethanol than gas, since we still buy the same ratings I can only assume oil companies are reducing the refining costs of the gasoline to minimize the net cost of the fuel.

For a data point on the car's behavior and how well optimized it would be to use a blend, I retuned the ECU on my 2006 Honda S2000 with a product by Hondata. The fuel injectors used a preset fuel-air ratio settings map for wide open throttle across the RPM range, and it used an oxygen sensor to approach ~14.7:1 air:fuel for part or light throttle. It was an open loop system with a long and short term fuel trim adjustment to keep it close to that target. The wide open throttle settings map was a little more rich than stoichiometric to keep the motor safe since running lean produces detonation--it targeted around 13:1, but the precise number seemed to vary by car model and even by individual years of the same make and model; a major trend was turbocharged cars typically were more rich than naturally aspirated vehicles. I understand my 370Z and others work generally the same way.

Comment Boeing's rationale (Score 2) 242

Boeing has an explanation of the rationale and the steps they've taken to examine the effects of electronics on aircraft in their "Aero" magazine. This is pretty old (2000) and would certainly benefit from an update, but they did real live technical investigation instead of just mixing assertions with quasi-technical arguments. A link to the full text:
http://www.boeing.com/commercial/aeromagazine/aero_10/interfere_textonly.html

TLDR Summary:
After receiving very specific, detailed claims/complaints from airlines, Boeing inspected the frequency range output and dB level of electromagnetic emissions from several specific devices. Their biggest concerns in the testing seemed to be the EMI due to frequency harmonics and interactions between devices--the premise and conceptual explanation seems unlikely but isn't completely meritless. No airplane susceptibility was demonstrated. Boeing clearly said that since they tested specific items, the testing was not conclusive for all devices and all interactions.

The excerpt on cell phones in particular deserves to be fully quoted, as it illustrates their thinking:
*Cell phone tests and analysis.*
Boeing conducted a laboratory and airplane test with 16 cell phones typical of those carried by passengers, to determine the emission characteristics of these intentionally transmitting PEDs. The laboratory results indicated that the phones not only produce emissions at the operating frequency, but also produce other emissions that fall within airplane communication/navigation frequency bands (automatic direction finder, high frequency, very high frequency [VHF] omni range/locator, and VHF communications and instrument landing system [ILS]). Emissions at the operating frequency were as high as 60 dB over the airplane equipment emission limits, but the other emissions were generally within airplane equipment emission limits. One concern about these other emissions from cell phones is that they may interfere with the operation of an airplane communication or navigation system if the levels are high enough.

Boeing also performed an airplane test on the ground with the same 16 phones. The airplane was placed in a flight mode and the flight deck instruments, control surfaces, and communication/navigation systems were monitored. No susceptibility was observed.

Telephones installed and certified on the airplane by Boeing or operators are not actually cell phones, but part of an airborne certified satellite system. These phones are electromagnetically compatible with the airplane systems because their emissions are controlled. In contrast, the emissions from passengers’ cell phones are not known or controlled in the same way as permanently installed equipment.

Comment The math isn't the moral question (Score 1) 604

The calculus of societal interests isn't the question. At the core, we have a larger moral question:
Is it ethically right to plan to kill one innocent person if it should save the lives of five, ten, or whatever number of people?

Individualist thinking is inclined to argue it's unconditionally wrong to knowingly place (force) an innocent person onto the altar to die. Societal/communal thinking is inclined to argue the greater wrong is that which produces the greater loss, therefore the innocent one must (perhaps unwillingly) give his/her life to preserve the safety of the others. We cannot expect our society as a whole to make a unified decision here; we must instead be convinced that we don't need to ask questions that are this hard.

Rather than trying to decide how many deaths are too many, we need to convince ourselves we've solved this causes-of-death question before we implement the solution. This will probably mean we first solve it for specific, well-controlled roads/freeways, and then over time we can extend the solution outward to additional classes of roads and conditions.

Comment Wind Tunnel - CFD / Aero visualization app for iOS (Score 2) 165

The iOS app Wind Tunnel is a pretty good simplified fluid dynamics solver. It has air entering one side of the screen, exiting the other, and the sides of the screen are free edges. You then draw airfoils or shapes with your fingers and see how the fluid patterns change. You can tweak quite a few parameters. For instance you can change speed, look at pressure and vorticity plots as well as velocity, and introduce particles to see where they go. He spent a lot of time on getting the visualizations to look impressive.

It's incompressible flow and he said he was forced to sacrificed some exactness (allowing a bit of mass loss vs. the N-S equations in some circumstances) to get the computations to run efficiently on iOS hardware in realtime, so the visualizations are pretty reasonable but the numbers won't be exact. Overall it's a great app with a solid math/science/engineering foundation.

Comment Supersonic parallel (Score 1) 235

There's no reason this needs to blow up the arrival (or departure) port; it's loosely analogous to supersonic travel producing sonic booms from stacking pressure waves. Supersonic aircraft don't blow up the airports or home cities.

Besides, we need to figure out negative mass before this is a big deal.

Comment 13.75 billion light years (Score 1) 228

I think this is pretty neat. I hope we as a race can soon learn more about why and how to effectively communicate/teach that to simple white collar desk workers like myself.

This proves nothing about the long term generation of all stars everywhere though - this is a trend describing the stars in our universe, so it's an observation based on the restricted population of those stars within 13.75 billion light years of us in observed spacetime.

I'm kind of curious what's outside that box. Let's fund that starship. Maybe my great grandkids will find out.

Comment Performance of product - seems promising (Score 4, Interesting) 208

This will require some years of development, but it certainly shows promise.

The strength and stiffness of a fiber are not the performance we'll directly obtain from the materials. It's more like a potential number. Typical 'carbon fiber' products have on the order of 60%-75% fiber and 40%-30% plastic by volume, where epoxy is one of the most common plastics. The carbon fibers contribute strength and stiffness, but it would fracture easily with a rigid binder. The softer plastic binder acts to share and redistribute loading efficiently (after some fibers break) to keep the carbon fibers more or less all carrying load effectively.

They'll have to go experiment until they find which plastics work well with this. That took a long time for composites since if the plastic binds too strongly to the fibers, the resulting composite is very brittle and loses a lot of potential strength. Also, to optimize the bond strength, carbon/kevlar/glass/etc fibers are typically treated with a 'sizing' that help the fibers bind optimally to a targeted plastic or set of plastics. Hopefully this new material can leapfrog off of the progress and work of the composites industry. Humidity will also be a concern that requires some testing and may cause some compromise on binder selection.

Also, 'typical' fiber properties really depend on the application. A typical aerospace carbon fiber is Hexcel IM7, which shows considerable improvement over the properties they reported in the article, and others can be a fair bit better or worse. The IM7 6k tow fiber is reported to have:
Ultimate Tensile Strength: 5.15 GPa
Elastic Modulus: 276 GPa
http://www.hexcel.com/resources/datasheets/carbon-fiber-data-sheets/im7.pdf

Sample properties of one finished product provide:
Ultimate Tensile Strength: 2.5 GPa
Elastic Modulus: 163 GPa
http://www.hexcel.com/Resources/DataSheets/Prepreg-Data-Sheets/8552_eu.pdf

A few years ago the least expensive carbon fiber would sell for ~$15/lb raw material with the epoxy typically around $9/lb, and the IM7 fiber above is probably an order of magnitude more costly. I don't know what figures they used for their cost comparison, but they can't really have the whole cradle to grave process figured out at this stage anyway, so we'll see what happens when they get some material fabricated.

There's a lot of work ahead, but this seems promising!

Comment Cognitive dissonance (Score 1) 1774

Subscribing to young earth creationism doesn't necessarily mean the individual is unable to think critically in general. An alarming amount of cognitive dissonance would easily enable that belief to be written off by the believer as a simple exception in a world view that is otherwise near-identical to the world view shared by the rest of the first world.

Not all people bother to develop a coherent world view. It's not always important to them.

Slashdot Top Deals

Truth is free, but information costs.

Working...