纳米颗粒悬浮液池内泡状沸腾的实验研究

本文对纳米颗粒悬浮液在平壁面上池内沸腾进行了实验研究。实验用的纳米粒子为26 nm的铁粉和13 nm的三氧化二铝纳米粉末,基液为去离子水。分别配成体积浓度为0．1％, 1％和2％的悬浮液。实验结果表明,纳米悬浮颗粒对液体沸腾换热过程的影响会随着纳米颗粒性质,颗粒浓度及热流密度大小的不同而出现不同的效果;加入纳米颗粒后, 对基液沸腾换热的影响存在着两个相反的作用机制,它们分别为:纳米颗粒增强了液体内部的热量迁移能力(热物性的影响)和改变了加热面的表面结构特性(加热面特性的影响)。     

Representation surfaces of Young''s modulus and Poisson''s ratio for BCC transition metals

 The general expressions for the compliance , Young's modulus E(h k l) and Poisson's ratio υ(h k l) along an arbitrary direction [h k l] are given for cubic crystals. The representation surfaces, for which the length of the radius vector in the [h k l] direction equals to E(h k l) or υ(h k l), are constructed for seven BCC transition metals Cr, Fe, Mo, Nb, Ta, V and W. Neglecting W, which is isotropic, both representation surfaces of Young's modulus and Poisson's ratio are spherical surfaces. The remaining BCC transition metals may be grouped into two classes. In the first group (Cr, Mo, Nb and V) with negative values of s_A, Young's modulus surface has eight depressed corners and six rounded protuberances at the centers of the faces. In the second group (Fe and Ta) with positive values of s_A, on the contrary, Young's modulus surface has eight rounded protuberance corners and six depressions at the centers of the faces. The contrary conclusions are obtained for Poisson's ratio.     

非均匀散射层矢量辐射传输(VRT)方程高阶散射解的迭代法

将散射介质层在z轴方向划分成薄层，用薄层的一阶散射强度、Fourier变换和迭代方法求解散射介质整层的矢量辐射传输(VRT)方程的高阶散射解.该方法将一阶散射与高阶散射迭代结合起来，计算公式简明，可计算高阶迭代解，计算时间少.计算结果与一层均匀散射介质的VRT方程一阶Mueller矩阵解、半空间均匀散射介质二阶Mueller矩阵解、以及离散坐标-特征值特征矢量法的VRT热辐射的数值解作了全面的比较.提出并讨论了非均匀散射层主动与被动VRT方程的高阶解.本计算程序可以通用于非球形粒子多层结构及非均匀介质的散射和热辐射计算. 关键词： VRT方程 分层 迭代解     

NOESY技术在地胆草倍半萜内酯化合物结构鉴定中的应用（I）

明确从地胆草中分离得到的两对牦牛儿内酯型的立体异构体即地胆草种内酯（scabertopin）、异地胆草种内酯（isoscabertopin）、异去氧地胆草内酯（isodeoxyelephantopin）和去氧地胆草内酯（deoxyelephantopin）的C-2相对构型；方法 NOESY技术，并结合这4个化合物的¹H NMR，¹³C NMR，HMQC谱；结果 两对立体异构体的NOESY谱有明显差异；结论 通过分析NOESY谱，找寻H-1相关信息，若发现H-1与H-8，H-9β和14-CH₃有NOE相关，可以判断化合物的C-2为α构型，若H-1与H-5，H-7，H-3α及H-9α之间有NOE相关，则化合物的C-2为β构型.     

激光水下扫描成像系统的图像修正机理

同步扫描系统可以克服后向散射，但同时也产生了两种非线性，一是扫描线速度的非线性，一是由于距离对光能衰减造成的非线性，两种非线性都需要修正，本文从原理上讨论水下激光成像时能量衰减的修正原理与修正方法，并给出仿真结果。     

Ab-initio molecular dynamics simulation on nano-system under external pressure

A new constant-pressure molecular dynamics (MD) method is developed to simulate the dynamic behavior and structure transition of finite system under external pressure. In this method, no artificial parameter is introduced and the computation overheads are very small. As an application, a hard-soft transition of single wall carbon nanotube (SWCNT) under external pressure is found, which is in agreement with the experiments.

     

互补型自适应滤波器在心磁信号处理中的应用

将心磁信号从干扰噪声中加以提取并有效地消除噪声干扰是心磁信号处理中尤为重要的环节 .从改进算法的角度出发，提出互补型自适应滤波器结构以实现心磁信号的消噪处理.该滤波器针对心磁这类非平稳信号进行设计，有效地解决了常规自适应滤波器应用于心磁信号处理时收敛速度和稳态误差的矛盾.通过仿真实验和心磁实验结果表明，该算法能有效地消除心磁信号的背景噪声和工频干扰噪声.同时该算法也可用于其他非平稳信号的消噪处理. 关键词： 自适应滤波 心磁图 最小均方误差     

A New Cytotoxic Acetogenin from the Seeds of Annona squamosa

A New Annonaceous acetogenin,squamostolide(1),was isolated from the seeds of Annona squamosa.Its structure was elucidated based on spectroscopic methods and comparison with known compounds.It is the first example of Annonaceous acetogenin with each of the two ends of the aliphatic chain bearing a γ-lactone.Thenew compound exhibited cytotoxic activity in vitro against bel-7402 and CNE2 human tumor cell lines.     

Second order parabolic equations in Banach spaces with dynamic boundary conditions

In this paper, we exhibit a unified treatment of the mixed initial boundary value problem for second order (in time) parabolic linear differential equations in Banach spaces, whose boundary conditions are of a dynamical nature. Results regarding existence, uniqueness, continuous dependence (on initial data) and regularity of classical and strict solutions are established. Moreover, several examples are given as samples for possible applications.

     

摄像型等厚干涉实验仪器的研究

介绍了“摄像型等厚干涉实验仪”的构造及等厚干涉实验新的测量方法。