Engineering

Why IP telephony haven't become a landline communication standard yet? Some people say this is because Internet is less reliable than phone. But why is it less reliable if exactly the same hardware is used for signal transmission? If hardware is different, where exactly the difference is?

Just finished a great documentary on the Millau Viaduct in France, and it inspired me to create this thread about the biggest, baddest bridge near you. Know idea why, but bridges have always fascinated me. Even when I was a kid, I would stare out of the car window as we crossed rivers and gorges, awestruck at this road in the sky and how it was created. Here in South Carolina, the baddest bridge is the Arthur Ravenel Jr. Bridge about 75 miles away from me in Charleston. The cable-stayed bridge has a main span of 1,546 feet (471 m), (total length is 13,200 feet) and is the third longest among cable-stayed bridges in the Western Hemisphere. More bad a** …

I have two identical containers with vents at the bottom of each container, a tube connecting them at the top and each container filled half way with water, both are located in a larger tank of water. Question is: - If i press down on one of the containers forcing more water into the bottom of the container, will the air transfer to the other container via the connecting tube and force out the water in the second container?

I read that wood glue is supposed to bond better than wood, which didn't jive with my physical intuition. I did some stress testing with various types of wood, and here are my results!

I’m looking for some advice. For weeks at a time, I’ll be woken up once or twice a night. Sometimes I can lay in bed and at the same times I usually wake up I’ll feel an odd sensation of pressure in my head. Two successive housemates have felt the same thing. They’ve described it as a clicking, pinching, snapping or pressure sensation that lasts just a split second. It’s not painful, but its enough to wake us apparently. A while back I spotted tracks in the snow in a neighbors back yard. So, I approached that neighbor. He refused to install security lighting, or cameras, and just dismissed my reports. I was able to pay another neighbor to let me set…

Does Ballistic Capture mean solar engine ships can efficiently bring cargo to Mars? Since Mars gets about half the solar energy the earth does, braking near Mars is that much harder for solar powered spacecraft. Also, Ballistic Capture allows a continuous stream of cargo to be sent, keeping the solar ships continuously operating, no need to wait for that window only open every ~26 month. Return trip doesn't carry as much cargo, so the efficiency lost due to lack of solar energy is reduced. Thoughts?

Maaany years ago read about a figure that made sense to me... The delta t from a internal combustion engine related to the ambient temperature its cooling radiator was exposed. Cannot remember now. Was something like outlet temperature minus ambient temperature equals something near constant. Or ambient temperature plus inlet temperature equals a near constant figure. That ideal figure escapes me now... Any light or explanatory link please ?

Hi, I need to some kind of sensors/tags which can be placed outdoor. The same needs to be read from about 25 m. (There will be need of setting multiple sensors in proximity, so the reader had to be a pin point and accurate system.) On reading it should open particular pdf file on computer.

I'm currently creating a theoretical space habitat that would resemble a collection of Torus rings. Now, to keep them away from each other, I'm attaching them by 7 poles of 2219 aluminum on each ring to a motor that rotates them for artificial gravity and slight position adjustments. Now, I still need to do the trig, but I'm wondering if these poles will become stressed by rotations and if they can could withstand losing a pole. I'll get the trig on a soon as possible.

I want to engineer a room that has electromagnetic tiles on the floor and the surface of these tiles would be polarized south. i also want to create a suit that has various magnetic metals on the suit placed in specific anatomical positions and the surface of these metals would be polarized north. if calibrated correctly this could be used in space to pull down the person in the suit and allow the user to walk freely in a spacecraft. this would cause the person to use their muscles more often and the bones would have pressure on them. I believe this would either slow down or halt the process of bone and muscle loss. it isnt a complete solution but its a new approach to so…

What are the main reasons centralized electric networks use alternative currents aside the fact AC/AC transformers are cheap and is it guarantied we will never switch to DC in distributed electric systems? Can we design a bipolar DC outlet? What about DC/DC converter prospects?

Krypton-85 85Kr is a beta emitter with 687keV maximum energy and 10.7 year half-life. It's produced by uranium fission with 0.27% yield (137Cs and 90Sr: 6%). Here a report, a bit old and in French, but figures read the same in English anyway. 85KrIpsn.PDF When reprocessing used nuclear fuel rods at La Hague, solid fission products like 137Cs and 90Sr and separated for storage, but 85Kr is just diluted and emitted in the atmosphere. For instance in 1999, La Hague emitted 2.9*1017 Bq of 85Kr, more than the radioactivity of 137Cs and 90Sr released by the Chernobyl disaster. Iodine, caesium, strontium radioisotopes fall on the soil more quickly and locally if emitted…

Hi all. Magnets inside hard drives are bracketed by mu metal. Is the outside plate seen in some hard drive covers also mu metal ? Like the greyish portion on the cover below: The covers without an attached 'plate', are they usually made of mu metal ? Cover alone :

Hello everybody! We read again and again "Face-centered cubic metals are ductile, body-centered are not, while hexagonal close-packed are brittle". Some authors want even to justify it through numbers of slipping planes. Worse, a few ones would curb Nature to their reasoning if only they could, like "Ti-Al5V is brittle because it's a hexagonal alpha alloy" or "Zinc breaks upon bending because hexagonal" - no, I won't tell you who wrote that one. About every metallurgy textbook has a crystallography chapter that reproduces this nonsense, and I'm getting tired of it, so I've just made a table with metals of mechanical use. Most metals go against the claim. Observations…

I would appreciate any advice on finding the best insulation material for my food carrier. I have been testing an insulated reusable/returnable one hand-held carrier design to hold freshly prepared food hot as to be delivered. It works, but the heat retention is insufficient. The temperature is good for 45 minutes. It is made of blow molded polyurethane. I want to improve the heat retention to as long as possible, two hours! I have tested ways to maintain the food for a fresh appearance. Numerous material were tested, money was spent and lessons were learned. High-density Styrofoam, low cost, in different applications had good insulation quality but required too man…

The stem body with the motor, gears and batteries does not counter-spin in this stirrer gadget, it still manages to revolve the thick sauce/soup. How is it achieved ?

I usually sit next to a window at home and I hear that 80% of UVA penetrates glass and UVA is what causes aging. So my skin has been exposed to unecessary aging for years. I bought blackout shades. But I am concerned that they might be facing the wrong way. My question is. If blackout shades/blinds face the wrong way 1)would more UVA penetrate into my apartment than if they faced the right way? 2) IF UVA does penetrate, would it then bounce off the the walls and hit the blackout shades (which are facing the wrong way and which allowed UVA im) and then reflect back onto my skin again - so then my skin would be hit by twice as much UVA than it wo…

I get an increase in payload of ~5% using gravity feed tank to tank, 2 extra bulkheads in the boosters (mass not accounted for), LOX tank at bottom of main core (which may need some extra plumbing – mass not accounted for). Not really worth it? It seems throttling back the core engines to 70% reduces crossfeed advantage, but it seems like throttling back incurs some loss I haven't accounted for? It looks like this - stacks represent core and boosters tank placement. red is RP-1, blue is LOX, green is crossfeed LOX. Main core mass LOX: 243t (always metric tonne) RP-1: 161t Total mass: 404t Booster mass L…

Hi all, Im inventing a new product and need some advice as to what material i should use to create part of it. The goal is for it to be a clear material, thats heat resistant (wont bend or misshape) when a lit cigarette is touching it. Basically i just need to figure out what cheapest compound can be used as an ash tray almost. If i need to provide clearer instructions as to my request, just ask. Thanks!

Good day looking to build a electromagnet that is very powerful and curious as to best power supply(110 or 12 volt) unit will be made from largecopper coil I will source and will have a 24 x 24 inch metal plate on top unit is to attract metal filings from our small milling mill (prototype) that I will attempt to build on our farm with my son unit must be very strong able to pull metal from at least 4 inches away. Any help with materials list greatly apreciated regards steve

Hello all, I'm doing sorption studies of certain heavy metals (Pb, Cu, Zn, Ni, Cd, Cr) in soil (natural clay and kaolinite) with ph as a variable (2,4,7,10,12).On adjusting pH to reach a constant value using NaOH and HCl, my heavy metals in nitrate salts form are getting precipitated. thus unable to maintain the concern concentration (50ppm, 250ppm, 500ppm, 750ppm, 1000ppm). help me out please.. thanks in advance.

Or How To Sail The Cosmos. Any takers?

Want to learn how a 2500 watts PEL Hi-Power electronic stabilizer works? It does not provide 220 volts although values mentioned on it are as: Input = 90V - 250V Output = 220V I opened it and it has two meters which show input and output voltages. It has a transformer (not sure step up or down). It has a circuit which have 2 10A relays. Relays number is H200Fd12-10A. This circuit also have two rotating screw like things which can be adjusted to increase amperes or decrease amperes as one of person while repairing told me. The problem I believe is with this circuit. I am ready to change whole circuit along with relays. The maximum size relay I can get is 30A relay…

Turbofans work by burning jet fuel to spin turbines, ultimately powering the massive fan you see in the front of the engine. Could you substitute the jet fuel with liquid hydrogen and, in theory, make a jet plane that produces no CO2

I have been working on a rocket engine and I have cad models and everything and I am getting ready to build it. Then, I was running over the numbers one more time and I realized that the thrust I was getting was completely different from what I should have been getting. The big problem is the nasa equations. It uses the variables Ttotal and Ptotal. NASA states, "pt is the total pressure in the combustion chamber, Tt is the total temperature in the combustion chamber." However, when I plug in 300 psi and 5742 degrees fahrenheit and the exhaust values for each variable as given by NASA's isentropic equations, I get a thrust of 735 pounds, whereas the first time…