一阶最优性条件研究

本对由Botsko的关于多变量函数取极值的一阶导数检验条件定理^[1]进行了分析研究，给出了更实用而简捷的差别条件。最后，举出若干例子予以说明。     

简谐速度噪声及其与势场之间的频率共振

为了描述复杂的噪声环境，考虑了一种具有频率结构的噪声——简谐速度噪声，包括它的产生、关联函数、功率谱以及作为热噪声时的频率特性所导致的一些行为.结果表明：在频谱空间中简谐速度噪声是一种带通噪声，存在一个峰值频率，且噪声带宽由参量Γ控制.当简谐势中的一个布朗粒子受热简谐速度噪声驱动时，粒子能量极大值出现在两种频率相等的情况下.这表明噪声和势场的频率之间存在动力学共振，决定着粒子能量的大小. 关键词： 简谐噪声 简谐速度噪声 功率谱 频率共振     

Simulation of the Action of a Permeable Barrier on an Ideal Incompressible Channel Flow

Plane ideal incompressible flow in a rectangular channel partitioned by a thin permeable barrier (lattice) is considered. In flowing through the lattice the stream suddenly (jumpwise) changes direction and loses energy. The flow is assumed to be vortical; the vorticity is discontinuous on the lattice. A mathematical formulation of the problem for the stream function is proposed in the form of a nonlinear elliptic equation with coefficients discontinuous on the lattice line. A numerical solution is constructed using the finite-element iteration method. The results of the numerical simulation show how the flow velocity profile in the channel can be controlled by means of permeable barriers.     

93W合金有关力学参量的综合选评

 对93W合金材料进行了超声测量实验，并结合原有的超声测量结果进行了分析比较，提出了可以直接用冲击波速度关系式的三个系数c₀ 、λ和λ′来对钨合金的有关力学参量，如G₀、K₀、G₀′、K₀′等进行综合选评的方法。得到了一组对93W合金较为合理的力学参量推荐值。     

Nd0.5Ca0.5Mn1-xAlxO3 (x=0,0.03)体系中电荷有序态的超声研究

系统研究了Nd0．5Ca0．5Mn1-xAlxO3(x=0,0．03)单相多晶样品在低温下的电磁性质和超声特性．电阻和磁化率测量表明,Nd0．5Ca0.5O3体系在TCO-257 K处发生了电荷有序相变．超声声速从室温开始随着温度的降低逐渐减小,并在TCO附近达到最小,之后,随着温度的进一步降低,声速急刷增加,同时伴随着一个尖锐的超声衰减峰出现.TCO附近的超声异常表明体系中存在着强烈的电-声子相互作用,该电-声子耦合来源于Mn3 的Jahn-Teller效应．在低温下,出现了另一个超声衰减峰,它的出现归结为反铁磁相与顺磁相之间的相分离现象.随着Al在Mn位的掺入,超声声速的最低点和衰减峰向低温移动,表明体系中的电荷有序态和反铁磁相均被部分抑制,     

差分吸收光谱法测量大气污染的测量误差分析

差分吸收光谱技术被广泛地应用于测量大气中微量元素的浓度，尽管该技术利用最小二乘法来反演待测气体的浓度，能够得到很高的测量精度。但是，由于仪器本身的噪声以及测量波段其它气体的干扰等，使得仪器的测量有一定的误差，而且上述因素还决定着仪器的测量下限。对差分吸收光谱方法的测量误差以及引起误差的原因作了详细的分析。     

New FIR laser lines and frequency measurements for optically pumped CD3OH

Twenty new cw FIR laser lines in CD₃OH, optically pumped by a CO₂ laser, are reported. The frequencies of 39 of the stronger laser lines were measured relative to stabilized CO₂ lasers with a fractional uncertainty, as determined by the reproducibility of the FIR frequency itself, of 2 parts in 10⁷.Contribution of the U.S. Government, not subject to copyright.     

Reciprocating sliding wear behavior of laser-clad small amplitude Mo2Ni3Si/NiSi metal silicide composite coatings

Mo₂Ni₃Si/NiSi metal silicide composite coatings with a fine microstructure consisting of Mo₂Ni₃Si primary dendrites and the interdendritic Mo₂Ni₃Si/NiSi eutectics were fabricated on austenitic stainless steel AISI 321 by laser cladding process. Small amplitude reciprocating sliding wear resistance of the coatings is evaluated as functions of normal load and slip amplitude and the wear mechanisms were discussed based on worn surface morphology observations. Results showed that the Mo₂Ni₃Si/NiSi coatings have excellent small amplitude reciprocating sliding wear resistance.     

Mathematical modelling of the oxidation of nickel titanium alloys

A one-dimensional bulk reaction model for the oxidation of nickeltitanium is formulated, with preferential oxidation of titaniumbeing included. The modelling is directed at the better understandingof the dominant mechanisms involved in the oxidation processand their significance for the biocompatibility of the alloy.Two different regimes for the relative diffusivities of oxygenand the metals are investigated. By assuming fast bulk reactions,different asymptotic structures emerge in different parameterregimes and the resulting models take the form of moving boundaryproblems. Different profiles of nickel concentration are obtained:in particular a nickel-rich layer (observed in practice) ispresent below the oxide/metal interface for the case when oxygenand the metals diffuse at comparable rates.     

风力发电机组变速恒频控制系统研究

全面介绍了一种最新应用于风力发电中的新型电机—无刷双馈电机，并分析了这种新型电机作变速恒频运行的原理并对这种电机进行了动态特性仿真研究，给出了形式简洁的控制方程和易于实现的控制方案。