纳米尺寸Y2O3掺杂TiO3粒子材料的结构和电流变性能

用溶胶凝胶法合成了纳米尺寸Y2O3掺杂的TiO3粒子材料，将材料在不同温度下灼烧得到5种电流变(ER)材料。通过X射线粉末衍射(XRD)分析确定了材料的晶体结构，用元素分析、热重分析和XRD分析确定了材料的组成，分别研究了各粒子材料与甲基硅油混合(25％，质量分数)组成电流变液(ERF)，5种ERF的ER性能以及介电常数(ε)、介电损失(tanδ)。     

Low-Resistant Band-Passing Noise and Its Dynamical Effects

We propose an n-order noise, which is realized by driving an n-order linear differential equation with a Gaussian white noise. The time-derivative noise is a low-resistant band-passing noise. If the derivative noise is regarded as a thermal one, the system has a vanishing effective friction and it should induce ballistic diffusion of a free particle at long times. The simulation method for the generalized Langevin equation driven by the n-order noise is discussed systematically. The features of three-order derivative noises are presented when they are applied to a ratchet system.     

Wideband high-resolution direction of arrival estimation method based on the pressure-velocity combined processing using the acoustic vector sensor array

In order to solve the problem of DOA (Direction of Arrival) estimation of underwater distant wideband targets, a novel coherent signal-subspace method based on the cross spectral matrix of pressure and particle velocity using the Acoustic Vector Sensor Array (AVSA) is proposed in this paper. The proposed method is different from existing AVSA based DOA estimation methods in using particle velocity information of Acoustic Vector Sensor (AVS) as an independent array element. It is entirely based on the combined information processing of pressure and particle velocity, namely, the P-V cross spectrum, has better DOA estimation performance than existing methods in isotropic noise field. By theoretical analysis, both focusing principle and eigendecomposition theory based on the P-V cross spectral matrix are given. At the same time, the corresponding criteria for source number detection is also presented. Computer simulations with data from lake trials demonstrate that the proposed method is effective and obviously outperforms existing methods in resolution and accuracy in the case of low Signal-to-Noise Ratio (SNR).     

Analysis of the effect of blocking mass at corner interface of two plates at arbitrary angles on transmission of plane bending waves

Vibration energy transmission at corner interface of two infinite plates rigidly jointed at arbitrary angles was studied by wave approach so as to investigate the effect of blocking mass used for reducing plane bending wave transmission.Two local coordinate sys- tems were introduced and six new non-dimensional coefficients implying corresponding ratio governing characteristic impedances of plates or blocking mass were introduced to simplify for- mulations of transmission and reflection coefficients.Five samples were tested in experiment. Discussions were carried out based on the comparison between prediction and experiment in terms of insertion loss.It is concluded that blocking mass at corner interface acts like a"low- pass filter",effective for vibration attenuation above certain frequency.The value of TL and IL in"attenuation band"depends mainly on mass per unit length and band width of"attenuation band"on mass moment of inertia per unit length of the blocking mass.     

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征求对有机化学学科“十五”计划优先资助领域的建议 　　为做好国家自然科学基金委员会正在进行的“十五”计划优先领域战略研究以及“学科发展 及优先资助领域专题调研”和“十五”计划期间有机化学学科重大、重点的立项准备工作, 我们希望广泛听取和吸收科学家的意见和建议,并真诚地希望各位专家从有机化学学科发展 的高度出发,提出对优先资助领域或学科发展的建议,以支持有机化学学科的基金资助工作 。 　　以下几点仅供参考： 　　1．　从学科发展和国家需求两个方面阐明所提领域的地位和作用。 　　2．　阐明该领域目前在国际上的发展特点、前沿和发展趋势,并举例说明具有国际 领先水平的研究成果。 　　3．　分析和评价该领域在我国的研究现状,水平以及在国际上的地位。 　　4．　提出对未来发展方向的建议,重点是“十五”计划期间我国在该领域的发展方 向、目标、迫切需要优先资助的重要项目和关键性科学问题。 　　希望将所提建议的具体内容于2001年4月底以前寄来或以电子邮件传给有机学科。 国家自然科学基金委员会 化学科学部有机化学学科 2000年11月10日