一篇有趣的文章

1、一篇(y pin)有趣的文章An interesting article-by Octave Levenspiel共三十二页Octave LevenspielEducation:Ph.D. Chemical Engineering, Oregon State University, 1952M.S. Chemical Engineering, Oregon State University, 1949 B.S. Chemistry, UC Berkeley, 1947 Interests and Research:Octave Levenspiel served as a faculty me

2、mber for 25 years until he retired in 1991. He authored 5 books and many papers and proceedings, two of which have been listed as Citation Classics. He was awarded AIChEs 1977 W.K. Lewis Award, the 1979 R.H. Wilhelm Award, and the 2003 Founders Award and Gold Medal, the highest honor given by the so

3、ciety. In 2000 he was inducted into the National Academy of Engineering. He also received two honorary doctorates, one from France. He is known as the founder of Chemical Reaction Engineering. Primary writings：Chemical Reaction Engineering，1st ed., wiley, 1962.Chemical Reaction Engineering，2nd ed.,

4、wiley, 1972.Chemical Reaction Engineering，3rd ed., wiley, 1999.Chemical Reactor Omnibook, OSU Bookstores, Corvallis, OR ,1996.Fluidization Engineering, 1st ed., wiley, 1969.Fluidization Engineering, 2nd ed.,B-H,Boston,MA,1991.共三十二页Octave Levenspiel 男，1926年出生于上海，波兰裔美籍人，美国工程院院士，美国俄勒冈州立大学教授，华东理工大学名誉教授。

5、毕业于华东理工大学前身(qinshn)之一的震旦大学化工系，后于加利福尼亚大学伯克利分校（University of California，Berkeley）获学士学位，美国俄勒冈州立大学获硕士学位，1952年获博士学位，留校任教25年，于1991年退休。曾发表100余篇学术论文和会议报告，其中两篇已被列为“引文经典之作”。他曾被授予美国化学工程师学会1977年W.K. Lewis奖、1979年R.H. Wilhelm奖、2003年创始人和社会赋予的最高荣誉金奖。2000年被聘为美国工程院院士。长期从事化学反应工程领域的研究，是世界著名化学反应工程学科领域的专家学者，国际著名的化学反应工程鼻祖

6、，有化学反应器之父的著称。他著述的化学反应工程一书，被世界上十几个国家翻译出版，并作为本国大学化工类教材。共三十二页震旦大学（Aurora University）原名震旦学院，1928年改称震旦大学，是天主教耶稣会在中国上海创办的著名教会大学，是中国近代著名高校，由中国神父马相伯于1903年2月27日，在徐家汇天文台旧址创办。“震旦”一词出自梵文，意即中国，在英语中，亦有黎明、曙光的含义。由此可见，马相伯将震旦学院喻作旭日东升，担负着以教育开启中国曙光的重任，必将(b jin)前途无量。英、法文校名分别为Aurora和LAurore。1952年10月高校院系调整，震旦大学撤销，医学院和圣约翰大

7、学医学院、同德医学院合于原址组建上海第二医学院；其余院系分别并入复旦大学、上海第一医学院、华东师范大学、交通大学、同济大学、华东化工学院、华东政法学院、上海财政经济学院等高校；附属中学改为上海市向明中学。震旦大学原址现为重庆南路227号和280号上海交通大学医学院校舍。共三十二页Opening words In 1915, Alfred Wegener, a meteorologist proposed that the continental land masses drifted about the world, wrote a book presenting these ideas ,

8、and supplied evidence to back his proposal.A pipe dream a fairy story Completely opposed this theory Jeers, sneers, derision, and sarcasm, but it did not disappear.共三十二页 It was not until the 1970s that the American geology establishment finally accepted this concept, and today we talk of continental

9、 drift as if we always believed it.共三十二页 We should realize that any idea about our distant past is always accompanied by uncertainty; however, these ideas suggest new questions which add to the idea or help to destroy it. One should question and explore new ideas and not dismiss them offhand with st

10、atements such as “We paleontologists dont believe in aerodynamic theory,” “this is a waste of paper” as that words.共三十二页 Highly speculative investigations, especially by an unknown author, are best brought before the world through some other channel than a scientific society which naturally hesitate

11、s to admit into its printed records matter of uncertain value._ Lord Rayleigh共三十二页Atmospheric Pressure at the Time of DinosaursIn fact, most scientists have just accepted that the atmosphere was not much different in the past from what it is today. True, some have speculated that the CO2 concentrati

12、on was as much as 800 times larger than todays value, or about 0.25 bar, but little else is assumed to differ.共三十二页If so, the author proposed three questions: ? The Bioenergetic Problem of the Quetzalcoatlus;? The Aeronautical Problem of the Quetzalcoatlus;?The Problem of Pumping Blood to the Head a

13、nd Brain of a Giant Dinosaur.共三十二页The power of resting warm-blooded creatures (in effect, their metabolic rate) is represented by the mouse-to-elephant curve, see Fig. 2, with its representative equation Power available M0.734 Figure 2. The “mouse-to-elephant” curve shows that the power of a warm bl

14、ooded animal is proportional to its mass to the 0.734 power. 共三十二页Now the minimum power needed for the level flight of any creature was given by Renard over a century ago as Power needed M 2/3/(A1/21/2) (2) If L represents the size of the flying creature, then for creatures of different size but of

15、similar geometry Mass, M L3 (3) Wing area, A L2 Replacing eq. 3 in eq. 2, we find that the power needed for a creature to fly is given by Power needed to fly M 7/6/(1/2) (4) 共三十二页? How then could 86-100 kg creatures fly in the age of dinosaurs, 64-100 Mya?Figure 1. Wingspan of a quetzalcoatlus compa

16、red to todays largest bird and a Boeing 737 jet aircraft. 共三十二页Figure 3. Aeronautics plus thermodynamics tells that the power needed to stay aloft depends on the creatures mass and the atmospheric density, as given by eq. 2. Figure 4. The maximum mass of todays flying birds is 14.5 kg. Heavier birds

17、 can fly in denser air. 共三十二页 The biology of these ancient flyers differs from todays flyers in that they were more efficient in their use of oxygen, living at a much higher metabolic rate. this would put them far above the present day mouse-to-elephant curve. From biological considerations this is

18、quite unlikely, see Fig. 2. These creatures were not true flyers. They stay on the ground and waited for a strong wind. With a wind speed of over 5 m/s they would spread their wings and glide about. They sat on top of hills peering down. When they spied dinner hopping about down below they would swo

19、op down, snatch their meal and then trudge back up the hill, to rejoin their cousins there, see Fig 5.Figure 5. One theory holds that pterosaurs may only have glided rather than flown. 共三十二页 The pteranodon could not stand bipedally because its legs were positioned wrongly on its body. It probably sl

20、id along on its stomach by reaching forward with its legs gripping the ground with its feet and pulling itself along, as does a crawling bat. Most importantly, large pteranodons appear to have lacked the physical power to perform hovering, thus could not have taken off from level ground. So it proba

21、bly lived at edges of cliffs. To counter this deficiency others proposed that the Andes in the southern half of South America somehow did not exist 60 Mya, so the strong westerly winds (the “roaring 40s”) could sweep practically continuously across the low-lying continent unopposed by any mountain r

22、ange. This allowed pterosaurs to fly, see Fig. 6.共三十二页Figure 6. Southern South America minus the Andes mountain range will allow strong prevailing westerly winds to blow continually. All these difficulties lead to improbable scenarios. To have survived and thrived for millions of years, these flyers

23、 had to be fast, efficient, and well adapted to their environment. Since the power needed is lower at higher atmospheric pressure, see eq. 2, let us propose an alternate explanation, that the atmosphere in the Cretaceous period was different from todays in that it was denser. 共三十二页We know of no othe

24、r scenario which can account for and explain why the metabolic rate of these giant flyers differs from all other warm blooded fliers, and why the flight energetics of pterosaurs is not consistent with all other flyers from the smallest of insects, to birds and aircraft, all the way to the Boeing 747

25、.共三十二页Figure 9. Relative size of animals. 共三十二页These numbers suggest that the dinosaur heart should not weigh more that one ton. However, taking into account the blood flow rate and the fact that the blood has to be pumped 10 or more meters upward, suggests that the heart should weigh about 5 tons.

26、Whether one ton or 5 tons, it would be a giant heart pumping blood up to a high pressure, somewhat like that of an automobile tire.共三十二页Figure 10. Proposed explanations. (a) Dinosaurs with multiple hearts . (b) Horizontal necked dinosaurs who cannot raise their heads . (c) Dinosaurs with their heart

27、s near their heads. This requires that the lungs be near the heart, but I do not know how to show this in the figure . 共三十二页Figure 11. From the first law of thermodynamics the three flow systems in this figure all require the same pumping power. 共三十二页water can be sucked up about 10 m, minus about 1

28、m to account for frictional loss caused by fluid flow and by the vapor pressure of the water. So if a siphon tries to raise water more than about 8 m it wont work. Similarly, for blood with its different physical properties, a siphon can not raise blood more than about 7 m.共三十二页(a) Water siphons les

29、s than about 9 m high will work. (b) Above about 9 m will not work. (c) Partial siphons are just nonsense. (d) 共三十二页This design is clever but will not work. 共三十二页With a higher atmospheric pressure taller siphons will work. 共三十二页by assuming a higher atmospheric pressure we have a physically reasonabl

30、e explanation for how to operate a siphon taller than 7 m. Figure 14 shows that when the atmospheric pressure is roughly over 2 bar these long necked creatures could exist. Thus we tentatively conclude thatthe atmospheric pressure at the time of the dinosaurshad to be higher than one bar, at least 2

31、 bar.At these higher atmospheric pressures taller siphons would work at 1 bar 7 m high; at 2 bar 14 m high, and so on.共三十二页ConclusionIf you allow yourself to entertain the idea that a higher atmospheric pressure, say between 3 and 5 bar, could have existed in the time of the dinosaurs, it would reso

32、lve two of the anomalies that face us today, which are:how a dinosaurs heart could pump blood 7 or more meters upwards, without introducing the ideas of multiple hearts (as many as 8), giant hearts, and hearts located right under their chins, and* how a giant flying quetzalcoatlus had the energy to stay airborne, something that biology and aerodynamics says is not possible in todays atmosphere.All of this lea