介绍《力学小问题及全国大学生力学竞赛试题》

第五届全国周培源大学生力学竞赛即将举办之际，我们应广大读者的要求，受《力学与实践》编委会委托，整理了《力学小问题与全国大学生力学竞赛试题》，现已由清华大学出版社出版。     

Design of new seismometer based on laser Doppler effect

In order to improve the resolution of seismic acquisition,a new seismic acquisition system based on tangential laser Doppler effect with an optimized differential optical configuration is proposed.The relative movement of the inertia object and the immobile frame is measured by laser Doppler effect,which can avoid the electromagnetic and thermometric interference,and the adoption of frequency-modulated (FM) transmission can improve the ability of anti-jamming.The frequency bandwidth is properly determined by analyzing the frequency of the Doppler signal.The velocity, displacement,acceleration, and frequency to be measured can be real-time acquired by frequency/velocity (F/V) converting the FM Doppler signal. A 100-dB dynamic range and the linear frequency range of 1.0 to 1000 Hz are realized.     

Optical fiber temperature sensor based on wavelength-dependent detection

Semiconductor fiber temperature sensors have been used widely in many fields, but most of them pick up temperature by measuring the optical intensity of certain fixed narrow-band in absorption spectrum.Furthermore, they are sensitive to the loss of optical intensity and the fluctuation of light source power.The novel temperature measurement system proposed in this paper is based on the semiconductor absorption theory and the spectral analysis of method. To measure temperature, the sensor model detects not the certain narrow-band spectrum but the most spectra of the optical absorption edge. Therefore the measurement accuracy and the stability can be improved greatly. Experimental results are in agreement with theoretical analysis results perfectly.     

巧用等价转化解含参数的恒成立不等式问题

求解合参数的恒成立不等式问题是近几年来各类考试的热点题，这类问题由于既有参数又有变量，学生往往感到很棘手，常因解法不当花费过多时间或半途而废．如何处理好这类问题呢？等价转化是解决问题、减少运算量的重要途径，即运用等价转化思想将其转化为大家熟悉的函数问题，运用函数的性质求解．1转化为一农函数问题、经过恰当的变形，将其转化为一次函数，运用一次函数的性质求解．一次函数人X）一kx十b（kwt0）有下面性质：‘（1）人x）＞0在b，n」上恒成立ed人m）＞O且人n）＞0；（2）若k＞0，N4人x）＞0在【m，n」上恒成立ed八m）＞…     

~(58,60,62,64)Ni25.1MeV质子非弹性散射研究及其低激发态能谱和B(E2)比率的IBA分析

使用上海原子核研究所1.4m等时性迥旋加速器提供的25.1MeV质子束,测量了偶镍同位索弹性散射和第一激发态2_~+的非弹性散射微分截面。用零程扭曲波玻恩近似(DWBA)作理论分析,得到~(58,60,62,64)Ni 2_1~+态的四极形变参数β_2分别为0.23、0.28,0.25,0.21。采用相互作用玻色子近似(IBA)计算了这些核低激发态能谱及其约化电跃迁几率B(E2)。并对IBA唯象参数作了初步的准粒子无规位相近似(QPRPA)微观计算。     

Magnetic Properties of Hf0.8Ta0.2（Fe0.97A0.03）2 （A=Al, Co, Mn） Systems

Moessbauer studies on the effect of substitution with 3% Al, Co, Mn atoms in the intermetallic compound of Hf0.8Ta0.2Fe2 are reported. The Al substitution leads to increase of the FM-AFM transition temperature and to decrease of the AFM-PM transition temperature. The Co substitution leads to disappearance of the FM state, only showing some FM impurity component, while Mn substituted compound indicates coexistence of FM and AFM states at low temperature. The phenomena imply complex itinerant electron properties in these magnetic systems.     

微波相转移催化合成DL—苯丙氨酸

在微波作用下,仅用1min便完成了苯甲醛亚胺的固—液相转移催化苄基化反应,然后经酸水解得到d1—苯丙氨酸,全程总产率为62.5×10(-2)。     

ZnCuCoAlNO3型四元水滑石及其多氧阴离子柱撑物的合成与催化氧化性能

Anionic clay, ZnCuCoAlNO₃ and its polyoxometalate intercalates were synthesized, and were characterized by XRD, IR, ³¹PMAS NMR, DTA and elemental analysis. The pillared products are found to be effective catalysts for oxidation of cyclohexene with molecular oxygen under mild reaction conditions     

流通池介质交换差示脉冲阳极溶出伏安法用于多元素重叠峰的分…

本文用流通池介质交换差示脉冲阳极溶出伏安法在盐酸介质中富集，而以碳酸钠－碳酸氢钠缓冲溶液为溶出介质，有效地分离了酸性介质中Ｃｕ（Ⅱ）、Ｓｂ（Ⅲ）、Ｐｂ（Ⅱ）、Ｔｌ（Ⅰ）、Ｃｄ（Ⅱ）、Ｉｎ（Ⅲ）的重叠溶出峰，实现了多离子的同时测定。     

流通池介质交换差示脉冲阳极溶出伏安法用于多元素重叠峰的分离及其同时测定

本文用流通池介质交换差示脉冲阳极溶出伏安法在盐酸介质中富集,而以碳酸钠-碳酸氢钠缓冲溶液为溶出介质,有效地分离了酸性介质中Cu(Ⅱ)、Sb(Ⅲ)、Pb(Ⅱ)、Tl(Ⅰ)、Cd(Ⅱ)、In(Ⅲ)的重叠溶出峰,实现了多离子的同时测定。