基尔霍夫定律中的“独立回路”

对电路理论基尔霍夫定律中“独立回路”概念进行讨论,提出较为合理的独立回路的概念,并运用线性代数、几何方法、拓扑图论等方法,分别对平面电路网络和立体电路网络进行讨论,证明在此规定下基尔霍夫方程的独立性和解的确定性.     

自然科学研究中的"纠错机制"及其推广——科学与人文漫话之十二

论述了自然科学研究中“纠错机制”的理论基础、实施步骤及其推广到人文社会科学研究中的有关问题．     

复杂性的刻画与“复杂性科学”

近些年来 ,关于“复杂性”、“复杂系统”乃至“复杂性科学”的议论在国内外颇为流行 .出现了大批讨论“复杂性科学”的专著和文集 ,召开了许多以“复杂性”为论题的会议 .中国的“复杂性热”固然有偏好“新”提法的科学管理人士起了推波助澜的作用 ,但这也确实反映出科学发展的一种趋势 .自然科学在宇观、宏观和微观三个前沿发展着 .探索宇宙演化奥秘和微观世界结构的两个尖端 ,涉及愈益庞大的投资和设备 ,往往成为单个国家难以独立支持的项目 .美国前几年下马的超级超导对撞机和现仍在巡天的哈勃望远镜是两个实例 .当今世界上 ,有幸直接从…     

The properties of gamma-radiation and high-energy neutron fluxes in "MIR" station orbit

The study of radiation background components in the near-Earth space is very important for different branches of space research, in particular for space dosimetry and for the planning of gamma-astronomy experiments. Detailed information on the neutral components (gamma-quanta, neutrons) of background radiation was obtained during the Grif-1 experiment onboard Mir orbital station (OS). The measurements of fluxes of 0.05-50 MeV gamma-quanta and >30 MeV neutrons with a large area instrument (approximately 250 cm2 for gamma-quanta, approximately 30 cm2 for neutrons) as well as corresponding charged particle measurements (0.4-1.5 MeV electrons, 1-200 MeV protons) were made during this experiment. The background components induced by the station's own radiation as well as the albedo gamma-rays from the Earth's atmosphere were revealed as the result of data analysis for about 600 h of observation. A mathematical model describing the latitude and energy dependences of atmospheric albedo gamma-rays as well as of those of gamma-quanta produced in the material of the station due to cosmic ray interactions was developed. An analytical approximation of the spectrum of induced gamma-rays from radioactive isotopes stored in the station and instrument's materials is presented. The dynamics of gamma-quantum background fluxes during the geomagnetic disturbances of January 10-11, 1997 are discussed. An analytical representation of the latitude dependence of the integral flux of neutrons with >30 MeV is given.     

The "overshoot" effect and sensory hearing impairment

The threshold for the detection of a brief tone masked by a longer-duration noise burst is higher when the tone is presented shortly after the onset of the noise than at longer delay times. This finding has been termed the "overshoot" effect [E. Zwicker, J. Acoust. Soc. Am. 37, 653-663 (1965)]. The present letter compared the size of the effect in the better and more impaired ear of six subjects with high-frequency unilateral or asymmetric hearing losses of sensory origin. Thresholds were measured for 5-ms 4-kHz tones presented 10, 200, and 390 ms after the onset of a 400-ms, 2- to 8-kHz noise burst. The better ear of each subject was tested using two noise levels, one equal in sound-pressure level and one equal in sensation level to that used for the impaired ear. Thresholds for all subjects and all ears decreased monotonically with increasing delay time, with the size of the effect typically 5 dB. Thus a small overshoot effect was observed regardless of hearing impairment.     

"功"的教学设计与构思

【教学课题】 普通高中课程标准实验教科书《物理·必修2》（人教社2006年第2版）第七章第2节“功”． 【设计思想】 学生对“功”并不陌生,他们已经知道做功的两个必要因素、功的计算公式和单位等知识．本节课新增的内容主要有功的计算的一般表达式、正功和负功的物理意义、合力做功和分力做功的关系等．通过对教材的分析发现,这些新内容完全可以在原有知识的基础上,运用学生已经掌握的力的合成与分解等方法得出．为此,笔者一改以知识主线安排教学内容的传统做法,依据新课程基于建构主义教学理念,     

"理想实验"在物理学中的作用

在物理学中，为了便于进行理论研究，除了建立“理想模型”外，还常常设计“理想实验”，为了顺利完成物理教学，也常常应用“理想实验”．     

《物理学》电子教案制作和使用的体会

目前多媒体教学已在全国高校普遍推广，并日益发挥其作用．为此，我们配合马文蔚改编的《物理学》(第四版)教材的使用，制作了配套的电子教案，在教学中边制作边使用．经过近五年的教学实践，广泛听取了学生和教师的反馈意见，并借鉴了兄弟院校制作课件的经验，不断修改，目前已由高等教育出版社高教电子音像出版社出版．此电子教案有如下的主要特点．     

Approximate expressions for viscous attenuation in marine sediments: relating Biot's "critical" and "peak" frequencies

Simple approximate relations are proposed for the viscous attenuation per cycle of the fast compressional and shear waves in the low-to-intermediate frequency range. Corresponding closed-form formulas are derived for frequencies at which maximum viscous attenuation per cycle occurs according to the Biot-Stoll theory of elastic wave propagation in marine sediments. In the new formulas, Biot's approximation [M. A. Biot, J. Acoust. Soc. Am. 34, 1254-1264 (1962)] for the frequency-dependent viscosity correction factor F(f) and the assumption of relatively low specific loss (Q(-1)<(0.2) [J. Geertsma and D. C. Smith, Geophysics 26(2), 169-181 (1962)] are used to provide an accurate representation of the fast compressional and shear wave attenuation from low frequencies through a transition region extending to two or three times Biot's critical frequency f(c). The approximate viscodynamic behavior of marine sediments for the fast compressional and shear waves shows similarities to that of a "homogeneous relaxation" process for an anelastic linear element [A. M. Freudenthal and H. Geiringer, Encyclopedia of Physics (Springer-Verlag. 1958), Vol. 6].