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OldChemE

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Everything posted by OldChemE

  1. I love this post! Very often we solve problems ourselves simply through the thought process of describing the problem. I cannot count the number of times my batter math students have begun to describe the problem they were trying to solve, only to end the conversation with "oh!... nevermind" Well done!
  2. The element hidden in several of the replies is creativity, or the lack thereof. In my experience, collaborative teams where several members are very creative, especially if they have different skill sets, produce amazing results (because they tend to build on each other's inspirations). But-- one good engineer, if sufficiently creative, can outperform a group that lacks creativity.
  3. Yes-- frustrating-- but not without purpose. It facilitates part numbering. For example, 787ST-24 is a model 787 hose, super tough cover, 24/16 ID. Virtually every industry over the years has faced the issue of creating meaningful part numbers primarily intended to be intelligible to professionals in their industry. This is just one example.
  4. By now I presume you will have already found your answer. But-- if you are still struggling with dimensional analysis maybe a teacher's perspective will help. 1.. You have two pieces of information: liters used and km traveled, but the question asks for efficiency in km/L So, step 1: you need numbers arranged in a ratio that matches the desired answer. It wants km/L (a ratio), so the ratio has to match: 100100100 km/88 L Here, we made a ratio using the actual numbers making it so that the km's are on top and the L's on the bottom so that it matches the units in the required answer. Step 2, do the math (100100100 divided by 88) Step 3: you now have a number that has the units of km/L this is your answer. Think about this: We look at the dimensions that the answer is supposed to have, and form our ratio so that the arrangement of the dimensions we have matches the arrangement of the required answer (that is, km on top of the fraction and liters on the bottom). Then, we put in the numbers in the same arrangement and do the math. This is what Dimensional Analysis is all about: Using the dimensions of the answer we want to decide where to put the numbers in the math.
  5. If you want a 'real' answer I'm not sure it can be done very easily. It will depend on the friction losses in the tube, which depends on configuration, length, surface roughness and even the shape of the exit in the end of the tube. Sorry to not be very helpful.
  6. And the remarkable thing in my view is that the sequence in the periodic table correlates so well to both the number of neutrons and protons in the nucleus and the sequence of available valence electrons, and to the actual energy levels of electrons (s, p, d, f, etc), even though this information was unknown at the time. The real value of the Periodic Table is that it groups the elements in ways that reflect their chemical behaviors--a very valuable 'shorthand' way of understanding the elements. Perhaps there are a few places in the table that minor 'tweaks' might be of value, but I don't know off hand where those might be. For a while after retiring from Chemical Engineering I taught High School chemistry. The Periodic Table proved to be an excellent way to give students the "Big Picture" of Chemistry.
  7. This is difficult to interpret-- but I notice the heading says 'Expands the least expensive node first.' So-- my interpretation is that the red dashed lines are intended only to indicate the order in which the pathways are tested-- not the actual path used. The dashed line from A indicates that the first path examined is from A to C, because the cost from A to C is less than from A to B. The red line from C to B is only to indicate that the next pathway examined is the one that leads to B (from A). The next path examined is the one that leads to D from C, the next is the one that leads form B to D. The next is from D back to B (pathway ACDB - which fails) and finally the next pathway examined is ACDE, a success. In other words, I'm postulating that the red dashed lines show the order in which the algorithm tests destinations, not the path taken to test them. Summarizing, the system keeps testing paths starting with the least values until it finds the solution. The paths tested, in order, are AC, AB, ACD. ABD. ACDB, and finally ACDE.
  8. There is a difference. The arguments about heavier than air flying machines, like may similar arguments, were arguments based on ignorance of the science. The theory with regard to light speed has implications that have been tested and found to be correct, even though nobody has propelled a rocket to light speed. Einstein's predictions have been tested in so many ways and found to be correct to such an extent that the preponderance of evidence suggests he was right.
  9. Being alive is dangerous. What value is there in living if one cannot enjoy life in the manner they prefer, within the bounds of behavior permitted by society?? Total Deaths in 2018 were over 2 million. Motor vehicles are a minor component of the risk of living.
  10. Speaking as a licensed HIgh School math teacher I would say no-- not something we should teach in High School. Benford's law is indeed very interesting, but the High School math curriculum is focused on continuing the development of math skills started in lower grades, in a building block fashion, in order to prepare the student for post-HS education. Pre-Algebra, Algebra, Geometry, Algebra 2, pre-calc and sometimes early stages of Calculus. That is, we are still in the process of building connected competencies-- one topic building on the previous. Benford's law and its implications is pretty much outside the things that have to get done in High School. The amount of material to be mastered is very large and difficult to do as is-- I would not want to add more.
  11. "The theory claims, and the article deduces from empirical knowledge", which is stated in the link, involves scientific thought, but does not prove anything, particularly since the authors have no proof for the timelessness they theorize occurs at death. It might be true, and might be of some benefit in understanding what a person goes through at death, but it is not proven. As such, its a significant stretch to say it is supported by science. The idea that a person might experience some feeling attributable to heaven or hell at death is not new (pleasure or regret about how one lived one's life)
  12. Pure vegetable oil is usable in diesel engines. That does require oxygen (as noted by Sensei). Ignition under those conditions is achieved a t 15-120 atm. For ignition or decomposition without oxygen it will depend on temperature as well as pressure-- so there is no single correct answer. While I do not know for certain. I suspect that since the oil is essentially not compressible, it will not significantly heat up as it is compressed and therefore high pressure alone will neither cause it to ignite nor decompose.
  13. Color codes for resistors: Bad Boys rape....... Totally out of place today and I would not repeat it now-- but it got me through my EE courses 54 years ago.
  14. I don't think the number of people represented is a direct issue. That is, I don;t think it matters if a district is 750k or 120 k as long as they are all the same population. But-- the disparity in district populations and the gerrymandering are issues. I would love to see some simple-minded criterion for districts that would minimize gerrymandering, but I'm not sure what it should be. "All districts shall consist of a single rectangle of sufficient size to encompass x people?" I suspect this might be like th famous problem of how to draw a map in different colors without having two adjacent areas the same color.
  15. OldChemE

    NRA dissolvement

    I must have worded things badly. What I meant was that they have NOT been seeking to solve the problems, whereas, they probably know the technology best.
  16. OldChemE

    NRA dissolvement

    I very much agree the leadership of the NRA should be held accountable for any provable acts along the lines of those charged. As a gun owner, I want the Second Amendment to remain, but have long felt that the organizations that know gun technology best (Manufacturers and the NRA) should have been working with government to solve the problems instead of blindly fighting everything. So-- I hope this lawsuit will lead to some positive results.
  17. Good summary. Having just recently retired from teaching I see many challenges here. Certainly, until now, online learning has been underutilized, but in some areas where it is used it is not used well. Case in point is Math. Quite a number of schools now do online instruction in Math, but the success rate has been uneven. I suspect the issue is that online systems cannot always detect why a student gets a wrong answer and provide the correct guidance (making students do math on paper and reviewing the actual paper is a very important part of math instruction). But-- there are efforts to overcome these type of issues and COVID has given us the impetus to take on the challenges. More to the point of the OP-- I think the answer is that education is being changed. We are very, very, lucky that the development of online learning was already well underway before the virus arose. I do not, however, think we will do away altogether with physical schools. Socialization is an important part of education, along with activities like art, music, performing arts, and similar things that do not so easily lend themselves to online studies.
  18. The Speed of light in a vacuum is approximately 1.8 x 10^12 furlongs per fortnight (assuming I didn't screw up the math)
  19. Internal combustion engines that use pistons have two design problems. First, they must operate at some minimum RPM so that the vehicle is not subject to the significant vibrations due to individual explosions in cylinders. Second, they have maximum RPM limitations due to the conversion of linear to rotary motion, the loads on bearings and the attendant stresses. In a conventional system we have a flywheel and a transmission which serve to smooth the vibrations due to individual cylinder explosions and to give the vehicle the ability to accomplish speeds of zero to over 100 MPH (160 kph) while the pistons move in relatively small rpm range that allows them to function well. Your diagram does not appear to address these issues. How do you anticipate going from near zero velocity to high velocity while keeping the piston system operating in the relatively narrow range that will produce smooth energy flow without over-stress due to high RPM?
  20. The primary relationship between the mind and the real world is that the mind interprets the real world based on the inputs of the bodies senses. The mind does not create the real world. If it did, then the odds of dying if you step in front of a truck that your mind was unaware of might change. That is to say, the mind interprets reality but does not control reality.
  21. I've got degrees in Chemical Engr (B Sc) and Nuclear Science (M) so I will toss in my thoughts. However, you need to realize that I am retired, and entered the Chemical Engineering field 50 years ago. Things do change. The primary benefit of Chemical Engineering when I took my degree was that I had to study both the pure science (mostly chemistry, but also physics) and applications and to some extent project management. This meant my pure science background was somewhat less, but my ability to translate into practical uses was maybe a little stronger. In my case, this gave me a great deal of flexibility to take on different types of engineering as opportunities presented themselves. I was able to work in plant design and construction, project management, synergy projects (taking the outputs from many engineering disciplines and pulling them into a complete package) and even a little mechanical and electrical engineering. In Europe, where I spent 6 years, there is even a Nuclear Power plant that has operated safely for 40 years now whose pressure vessel is held to its foundation by bolts designed by a chemical engineer (me). I can't honestly say if this is typical-- but I have always been glad I chose the engineering route. Good luck!
  22. Good point. Actually, we are thinking along the same lines. By 'take care of the climate' I meant controlling CO2 emissions and such-- what you are calling environment (rightly so), because the environment and climate are simply two aspects of the same system. Studiot - to your question, I have not been able to find any research or data on the effect on areas to the south and east of northern Nevada. I think we can rightly speculate that dropping more water in Northern Nevada should create a water shadow. This could have bad effects. However, with the overall warming we are seeing increased evaporation from the Pacific Ocean. Interestingly enough, we have been seeing what appears to be more frequent cloud cover in our area, both in the winter and spring. Historically, our area of Northern Nevada has been in the rain shadow of the Sierra Mountains. With the increasing north-south amplitude of the jet stream we seem to be getting more moisture passing north of the Sierras, increasing our cloud cover. Thus, it might be that we can continue to take more of that moisture through seeding operations without causing a net deficit to the south. This is, of course, very speculative. Only time will tell. These thoughts are, of course, somewhat contrary to the BBC article. I'm wondering if this is a time lag issue (time from research to publication). Our part of Northern Nevada was in a major drought period up until two years ago. This winter, even the seeding operations I mentioned have not been done as the reservoirs continue to remain in good shape. PS: for those who will ask for evidence I will have to admit this is all so new in our area that I have not seen any proper studies. Its still all presumptive based on personal observations.
  23. Sorry I have been late replying-- I have been away for awhile. That is a very good question for which I do not know the answer. I'll try a little research.
  24. If you take any two objects, keep them carefully insulated, and apply a like electrical charge to both, they will repel each other. But--its not the materials that are repelling each other, but the charges.
  25. Obviously, the best solution is to take care of the climate properly-- but things can be done. For example, here in northern Nevada we had a major reservoir go dry (<5% capacity) a couple of years ago. As a solution a wintertime cloud seeding project was started focused on the mountain systems that feed the local rivers. By cloud seeding at strategic times, the project built the snow pack to 150% of the historic norm, and the spring runoff has refilled the reservoir without any deleterious flooding.
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