Heisenberg’s invention of matrices     

Pradeep Kumar 《Resonance》2017,22(4):399-405

Richard Feynman once said: “nobody understands quantum mechanics”. Still, those who devised it are perhaps the ones closest to understanding their creation. It suggests that whenever the weirdness of quantum mechanics haunts you, it is better to go back to its creators in terms of their original publications. In the present article, the author has tried to seek help from Heisenberg’s 1925 paper, in order to reduce the weirdness of going from classical observables to quantum operators.  相似文献   

Channel adaptive rate control for energy optimization     

Blanch Carolina  Pollin Sofie  Lafruit Gauthier  Eberle Wolfgang 《浙江大学学报(A卷英文版)》2006,7(1):82-88

Low energy consumption is one of the main challenges for wireless video transmission on battery limited devices. The energy invested at the lower layers of the protocol stack involved in data communication, such as link and physical layer, represent an important part of the total energy consumption. This communication energy highly depends on the channel conditions and on the transmission data rate. Traditionally, video coding is unaware of varying channel conditions. In this paper, we propose a cross-layer approach in which the rate control mechanism of the video codec becomes channel-aware and steers the instantaneous output rate according to the channel conditions to reduce the communication energy. Our results show that energy savings of up to 30% can be obtained with a reduction of barely 0.1 dB on the average video quality. The impact of feedback delays is shown to be small. In addition, this adaptive mechanism has low complexity, which makes it suitable for real-time applications.  相似文献   

A Novel Whiteheadean Science Program for 14-16 Year Olds in England and Wales     

Michael Akeroyd 《Interchange》2007,38(2):167-173

A novel “Whiteheadean” science program was initiated in England and Wales in September 2006. Following a critical House of Commons report in 2002, the government altered the National Curriculum targets and thus forced the Examination Boards to alter their specifications in order to come in line. Assessment at GCSE level (i.e., the 14-16 year cohort) was criticised for: a) failing to inspire students to continue with science, b) discouraging students from thinking for themselves, c) neglecting contemporary science, d) lacking flexibility, and e) making practical work into a tedious and dull activity. The British government has insisted that all pupils in state funded schools must know the names of some modern scientists and their work. They must discuss some current scientific problems. History and philosophy of science is included under the topic heading “How Science Works.” In Chemistry these objectives have destroyed the traditional linear top-down sequential approach of teaching into an approach based more closely on Whiteheadean lines (cf., the ideas expressed in The Aims of Education, 1926, Chapters 1-3).  相似文献   

Random vibration analysis of switching apparatus based on Monte Carlo method     

ZHAI Guo-fu CHEN Yang-hua REN Wan-bin 《浙江大学学报(A卷英文版)》2007,8(3):422-425

The performance in vibration environment of switching apparatus containing mechanical contact is an important element when judging the apparatus’s reliability. A piecewise linear two-degrees-of-freedom mathematical model considering contact loss was built in this work, and the vibration performance of the model under random external Gaussian white noise excitation was investigated by using Monte Carlo simulation in Matlab/Simulink. Simulation showed that the spectral content and statistical characters of the contact force coincided strongly with reality. The random vibration character of the contact system was solved using time (numerical) domain simulation in this paper. Conclusions reached here are of great importance for reliability design of switching apparatus.  相似文献   

Homoharringtonine induces apoptosis of endothelium and down-regulates VEGF expression of K562 cells     

叶琇锦  林茂芳 《浙江大学学报(A卷英文版)》2004,5(2):230-234

Homoharringtonine (HHT) has currently been used successfully in the treatment of acute and chronic myeloid leukemias and has been shown to induce apoptosis of different types of leukemic cells in vitro. Emerging evidence suggests that angiogenesis may play an important role in hematological malignancies, such as leukemia. How ever, whether HHT can relieve leukemia by anti-angiogenesis is still unknown. We investigated the anti-angiogenesis potential of HHT with the human umbilical vein endothelial cell line (ECV304) and leukemic cell line (K562) in vitro. Cellular proliferation was determined by MTT assay and apoptosis was analyzed by flow cytometry. The mRNA expression of vascular endothelial growth factor (VEGF) was assessed by RT-PCR and VEGF protein production was detected by Western blot. Inhibition of cell proliferation and induction of apoptosis by HHT were discovered in ECV304 cells, and appeared in a dose- and time-dependent manner. Also, treatment with HHT caused down-regulation of VEGF mRNA expression in K562 cells in similar dose- and time-dependent manner and inhibition of VEGF protein production in K562 cells in response to the enhancing concentration of HHT. The results demonstrated that HHT could also induce apoptosis in endothelium and down-regulate VEGF expression in K562 cells. In conclusion, we believe HHT has anti-angiogenesis potential and speculate that HHT might exert its anti-leukemia effects via reduction of angiogenesis.  相似文献   

Two categories of e-learning in Japan     

Minoru Nakayama  Rowena Santiago 《Educational technology research and development : ETR & D》2004,52(3):100-111

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Activity of metalloproteinases and adiponectin in obese patients— a possible factor of incisional hernias after bariatric procedures     

Wojciech Szczęsny  Magdalena Kuligowska-Prusińska  Stanisław Dąbrowiecki  Jakub Szmytkowski  Adrian Reśliński  Maciej Słupski 《Journal of Zhejiang University. Science. B》2018,19(1):65-70

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The elusive nature of whole system improvement in education     

Michael Fullan 《Journal of Educational Change》2016,17(4):539-544

Whole system improvement—where the vast majority of schools improve—is difficult to achieve. Some jurisdictions use what turns out to be ‘wrong’ policy drivers like testing and evaluation. Rather, success turns out to depend on changing the culture of schools and their relationship to the infrastructure of policies and regulation. I examined the six cases studies in the light of whole system change criteria. Two of the case studies, South Africa and India, represent limited but useful examples in that they focus on basic skills like literacy. A second set of two studies, Escuela Nueva and LCP in Mexico, represent strong examples of how bottom up strategies can spread to significant levels. The final two, Long Beach in the US and Ontario, are strong examples of how deep change can be accomplished by focusing on a few core priorities and then building a culture over a number of years to support and sustain the changes. The paper then draws conclusions about the conditions that will be required for large scale change to occur.  相似文献   

一种用于宽动态范围上的高精度散射测量的标准方法     

赵恒凯  方振和  姚传亮  蔡春富  章俊 《上海大学学报(英文版)》2003,7(3):246-250

The co-effect of transmitted power fluctuation and system nonlinearity produce deviations in scatterometer measurement results . An internal calibration method to deal with this problem is proposed. The method can result in more precise scatterometric measurements in a wide range. The basic principle of the method is combining real-transmitted-power detection with the calibration of system nonlinearity. A practical scheme to implement the method is also presented, which is developed based on a special designed mechanism of a microwave radiometer-scatterometer combined system.  相似文献   

The rewarding effects of number and surface area of food in rats     

Devina Wadhera  Lynn M. Wilkie  Elizabeth D. Capaldi-Phillips 《Learning & behavior》2018,46(3):242-255

Visual cues have an important role in food preference for both rats and humans. Here, we aim to isolate the effects of numerosity, density, and surface area on food preference and running speed in rats, by using a forced-choice maze paradigm. In Experiment 1, rats preferred and ran faster for a group of multiple smaller pellets rather than a single large pellet, corroborating previous research (Capaldi, Miller, & Alptekin Journal of Experimental Psychology: Animal Behavior Processes, 15(1), 75–80, 1989). Further experiments tested the prevailing hypothesis that multiple food pieces are more reinforcing because they occupy a larger surface area. Experiment 2 controlled for numerosity by utilizing a continuous food: mashed potatoes flattened to cover a larger surface area or rounded into a ball. The rats preferred and ran faster for the flattened potatoes, suggesting surface area plays a role in quantity estimations. Finally, in Experiment 3, rats displayed no preference or difference in running speed between a group of scattered and clustered pellets when number of pellets were kept constant. Taken together, these results suggest that density has an important role in food perception—that is, the rewarding effect of higher numerosity or larger surface area is removed when the food does not fill out the entire space. Alternative explanations and implications for human diet are discussed.  相似文献