探讨物理微观教学的手段

每当同行老师讨论物理的微观教学时,往往都有同感:微观结构难教,学生难学,若想学好,就更难了.笔者运用几种特殊手段进行微观教学,收到很好的效果.1 运用类比教学 培养学习兴趣 学习兴趣是提高课堂教学效果的关键.但枯燥的物理概念使某些学生学习兴趣不浓.如何改变这种状况?恰当的类比,将可培养学生的学习兴趣,提高学习的积极性.     

关于CAI物理教学的思考

1传统物理教学与CAI物理教学的比较 目前，CAI在各学科教学中的应用也越来越广泛，而对于采用CAI进行物理教学和传统教学相比较，有着它们各自的特点．     

例谈物理与数学的相互应用

物理与数学是两门古老的学科 ,它们之间有着密切的联系 ,下面用例子浅谈物理与数学的相互应用 .1　物理在数学上的应用在物理学里 ,我们知道 :若 AB为一根以O为支点的平衡杠杆 ,A、B、O三点受力分别记为 f A、 f B、 f O,则由杠杆原理知 :AOOB=f Bf A且 f O=f A f B从而得 :AO     

教学过程设计——物理教学设计系列讲座之四

教学过程是为实现教学任务和达成教学目标，通过对话、沟通和合作，以动态生成的方式推进教学活动的进程；其基本环节和内在逻辑结构都是动态的．教学过程设计形成的是一个“弹性化”方案，但一般应对教学顺序、教学组织形式、学习方式、教学模式、教学方法、学习环境及课堂管理等方面进行分析和设计．     

大学物理学研究性教学(续)

20 0 3年 1 2月 1 9～ 2 1日 ,受清华大学物理系和高等教育出版社以及教育部高等学校物理学与天文学教学指导委员会支持的大学物理学研究型教学高级研讨班在清华大学举行 .在连续 3天时间内首届国家级教学名师奖获得者卢德馨教授作了主题报告 .本刊 2 0 0 4年第 1期已经刊出了报告的前半部分 ,本期续完 .     

启发式、讨论式、研究式物理教学的实践与体会

文章介绍了笔者在大学物理教学中采用启发式、讨论式、研究式教学方面所做的改革尝试以及有关体会．     

例说两种教学论下的物理概念教学设计

以科学取向教学论为主线, 通过具体案例设计, 对比研究了在概念教学下的哲学取向教学论和科学取 向教学论, 并提出了教学设计的新观点     

试论双语教学的前景和困难

二十一世纪是经济全球化的时代，是知识经济的时代，社会经济发展对教育事业提出了更高要求，教育的国际融合是大势所趋。“教育要面向世界”，二十一世纪“国际化”已经成为当今教育改革和发展的方向和趋势。新世纪所需要的建设不仅要具备坚实的科学知识基     

任务分析的理论在物理教学中的应用

1　何为任务分析理论“任务分析”是继教学目标之后 ,依据认知心理学的理论 ,运用安德森的激活论 ,加涅的智慧技能层次、奥苏泊尔同化论等思想 ,用逆向设问法揭示、完成教学目标从起点到终点的层次关系 ,它既是教学设计的一种技术 ,又是一种教学理论 .它主要包括学习起点能力分析、使能目标分析、知识类型与学习方法分析及课的类型等几个方面 .通常教学中 ,教学目标是指课程学习结束时学生所要学得的能力或技能 .称为终点目标 .教师在描述教学步骤时 ,往往会遇到这样的困难 :是否所有目标在起始步骤都应指出来 ,这是因为教学设计中至少有两…     

双语物理教学的研究

随着我国社会经济发展和对外交流日益频繁，双语教学已经成为我国教育领域教学改革的一个重要课题。本文结合国内外有关理论成果和教学实践谈谈如何在大学物理教学中开展双语教学，从而拓展学生的物理知识和外语词汇，提高学生的能力，适应社会的需要。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.