柔性铰链微位移机构在可调谐F-P滤波器中的应用研究

分析了由于反射镜倾斜导致的可调谐F-P(Fabry-Perot)滤波器失谐。设计了一种柔性铰链式微位移机构,由压电陶瓷驱动,采用平行四连杆机构进行传动导向。采用该机构驱动F-P腔镜扫描克服了直接使用压电陶瓷带来的腔镜倾斜问题。该机构已应用于可调谐F-P滤波器中,输出信号多周期峰值幅度均匀,重复性好。     

加速溶剂萃取技术在中药有效成分分析中的应用

以两种药材为研究实例,对加速溶剂萃取法（ASE）在中药材有效成分提取研究中的应用进行了简要介绍。采用正交试验法考察了提取丹参中丹酚酸B的提取条件（萃取温度、静态萃取时间、萃取溶剂以及料液比）,确定了较好的实验条件。比较了ASE、水蒸气蒸馏法、超声波提取法及索氏提取法对木香挥发油的提取效果,结果表明ASE对木香挥发油的提取效果最好。     

尿素法合成高结晶度类水滑石

尿素的高温分解特性被用于控制层状化合物合成过程中的pH值。室温下尿素可与硝酸盐形成均一溶液，当其高温分解时可以保证溶液内部各点的pH值始终一致，因而可获得高结晶度的水滑石样品。利用该法可合成出Mg-Al、Zn-Al及Ni-Al类水滑石，但难以合成出Co-Al，Mn-Al及Co-Cr类水滑石，相信这与不同金属离子发生沉淀时所需的pH值有关。     

广州市住宅室内外大气羰基化合物的监测分析

选择代表性住宅,在其室内、外同步开展大气羰基化合物的监测分析,准确评价大气羰基化合物的污染状况,揭示其来源。用涂覆2,4-硝基苯肼(DNPH)的硅胶采样管收集羰基化合物,借助高效液相色谱完成样品分析,共检测了13种羰基化合物,其中甲醛、乙醛两种物质的平均浓度最高,占被测物质总浓度的30%~67%。甲醛、乙醛的浓度,夏季室内平均为53.47μg/m3、17.81μg/m3,室外平均为15.00μg/m3、10.97μg/m3;冬季室内平均为37.97μg/m3、11.49μg/m3,室外平均为10.44μg/m3、8.15μg/m3。大气羰基化合物呈现夏季高于冬季、室内大于室外的浓度变化规律。甲醛/乙醛和乙醛/丙醛比值结果反映城市大气羰基化合物的人为污染。     

DYNAMIC STABILITY OF SKEW PLATES SUBJECTED TO AERODYNAMIC AND RANDOM IN-PLANE FORCES

This paper presents an investigation into the dynamic stability of skew plates acted upon simultaneously by an aerodynamic force in the chordwise direction and a random in-plane force in the spanwise direction. Due to this random in-plane force, the plate may become unstable before the aerodynamic force reaches its critical value. In this work, the finite element formulation is applied to obtain the discretized system equations. The system equations are then partially uncoupled and reduced in size by the modal truncation method. Finally, the unsmoothed and the smoothed versions of the stochastic averaging are used to calculate the system response, and the second-moment stability criterion is utilized to determine the stability boundary of the system. Numerical results show that the stability boundary obtained by the smoothed stochastic averaging is less conservative than that obtained by the unsmoothed version, and the former is the tangent of the latter at zero spectral density of the random in-plane force.     

THE FORCED VIBRATION AND BOUNDARY CONTROL OF PRETWISTED TIMOSHENKO BEAMS WITH GENERAL TIME DEPENDENT ELASTIC BOUNDARY CONDITIONS

The governing differential equations and the general time-dependent elastic boundary conditions for the coupled bending-bending forced vibration of a pretwisted non-uniform Timoshenko beam are derived by Hamilton's principle. By introducing a general change of dependent variable with shifting functions, the original system is transformed into a system composed of four non-homogeneous governing differential equations and eight homogeneous boundary conditions. The transformed system is proved to be self-adjoint. Consequently, the method of separation of variables can be used to solve the transformed problem. The physical meanings of these shifting functions are explored. The orthogonality condition for the eigenfunctions of a pretwisted non-uniform beam with elastic boundary conditions is also derived. The relation between the shifting functions and the stiffness matrix is derived. The boundary control of a pretwist Timoshenko beam is studied. The effects of the total pretwist angle, the position of loading and the boundary spring constants on the energy required to control the performance of a pretwisted beam are investigated.     

Comultiplications on a wedge of two spheres

In this paper we study the set of comultiplications on a wedge of two spheres. We are primarily interested in the size of this set and properties of the comultiplications such as associativity and commutativity. Our methods involve Whitehead products in wedges of spheres and the Hopf-Hilton invariants. We apply our results to specific examples and determine the number of comultiplications, associative comultiplications and commutative comultiplications in these cases.     

2000 Vol.11 No.8 P.Preparation of AChE Inhibitors From Jujubogenin

A dammarane derivative dihydrojujubogenin-2-en-1-one, which possesses a skeleton and pharmacophore partially similar to those of Territrem B, a potent AChE inhibitor, was synthesized via three different paths. The anti-AChE activity of this compound and related analogue was measured.