管肋式辐射器排热特性的数值分析与优化设计

为得到按单面辐射方式布置的管肋式空间辐射器的排热特性，建立了相应的数学模型．采用数值模拟方法分析了管内流体温度、肋片几何尺寸和等效热沉温度对辐射器排热特性的影响，得到了不同参数值下辐射器单位面积排热量以及特定参数范围内的辐射器肋片最佳宽度和肋片效率．数值模拟结果对辐射器的工程结构设计以及空间站热管理方案的优化分析具有一定的参考价值．     

多级轴流压气机全工况特性计算

本文使用三维粘性流动计算软件Fine／Numeca,对某十五级轴流压气机进行了内流流场和全工况特性的数值计算尝试。分析了该压气机在设计工况和非设计工况的性能,同时把整机计算结果和前七级叶片的计算结果进行了比较。计算结果表明,当计算的级数较少时,目前的软件和硬件平台可以比较合理地预测压气机的全工况特性;而当计算的级数较多时,准确的数值模拟仍需要更为准确的多级模型和数值方法。     

Meshless simulation of equilibrium swelling/deswelling of pH‐sensitive hydrogels

Hydrogels have been widely used in microelectromechanical systems (MEMS) and Bio‐MEMS devices. In this article, the equilibrium swelling/deswelling of the pH‐stimulus cylindrical hydrogel in the microchannel is studied and simulated by the meshless method. The multi‐field coupling model, called multi‐effect‐coupling pH‐stimulus (MECpH) model, is presented and used to describe the chemical field, electric field, and the mechanical field involved in the problem. The partial differential equations (PDEs) describing these three fields are either nonlinear or coupled together. This multi‐field coupling and high nonlinear characteristics produce difficulties for the conventional numerical methods (e.g., the finite element method or the finite difference method), so an alternative—meshless method is developed to discretize the PDEs, and the efficient iteration technique is adopted to solve the nonlinear problem. The computational results for the swelling/deswelling diameter of the hydrogel under the different pH values are firstly compared with experimental results, and they have a good agreement. The influences of other parameters on the mechanical properties of the hydrogel are also investigated in detail. It is shown that the multi‐field coupling model and the developed meshless method are efficient, stable, and accurate for simulation of the properties of the stimuli‐sensitive hydrogel. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 326–337, 2006     

基于界面跟踪方法的汽蚀模型和算法的有效性验证

针对两相附着汽蚀流动机理,基于界面跟踪方法发展了新的汽蚀模型和算法。所发展的汽蚀模型和算法不仅考虑了液相／气相界面处的压力差,而且考虑了耦合Reynolds-Averaged Navier-Stokes方程求解技术得到的流场压力梯度信息来迭代计算附着汽蚀形状。采用具有试验数据的半球形头部圆柱体汽蚀绕流作为算例来验证所提出的汽蚀模型和算法的有效性。采用不同的网格数和松弛因子数值验证了发展的汽蚀模型和算法的有效性。三种汽蚀数下的数值计算结果得到的压力系数分布与试验数据完全吻合。结果表明所提出的汽蚀模型和算法能够准确模拟出汽蚀发生点和汽蚀长度。     

SUPER TOUGH GELS WITH A DOUBLE NETWORK STRUCTURE

 Living tissues work with fantastic functions in soft and wet gel-like state. Thus, hydrogels have attracted much attention as excellent soft & wet materials, suitable for making artificial organs for medical treatments.However, conventional hydrogels are mechanically too weak for practical uses. We have created double network (DN) hydrogels with extremely high mechanical strength in order to overcome this problem. DN gels are interpenetrating network (IPN) hydrogels consisting of rigid polyelectrolyte and soft neutral polymer. Their excellent mechanical properties cannot be explained by the standard fracture theories. In this paper, we discuss about the toughening mechanism of DN gels in accordance with their characteristic behavior, such as large hysteresis and necking phenomenon. We also describe the results on tissue engineering application of DN gels.     

电场作用下苏氨酸的电流特性研究

制备了以液态苏氨酸为沟道材料的四端有机场效应晶体管,观测了其随着栅极电压的不同呈现出源漏两极之间不同的电学特异现象;还观测了苏氨酸在外电场作用下,阻抗随着源漏之间电压频率变化的关系,提出一个极性液体模型解释了其导电机理。     

Phenomenological and neural-network modeling of cephalosporin C production bioprocess

Cephalosporin C production process withCephalosporium acremonium ATCC 48272 in synthetic medium was investigated and the experimental results allowed the development of a mathematical model describing the process behavior. The model was able to explain fairly well the diauxic phenomenon, higher growth rate during the glucose-consumption phase, and the production occurring only in the sucrose-consumption phase. Moreover, the process was simulated utilizing the neural-networks technique. Two feed-forward neural-networks with one hidden layer were employed. Both models, phenomenological and neural-networks based, satisfactorily describe the bioprocess. The difficulties in determining kinetic parameters are avoided when neural networks are utilized.     

表面能与晶体生长/溶解动力学研究的新动向

界面现象使物质在结晶过程中出现了临界现象.但最近的研究指出在物质溶解过程中,在表面能量的控制下也存在着临界现象以及尺寸效应.实验发现,当晶体自身小到一 定的程度时(通常在纳米尺度上并和临界蚀坑的大小相近),在溶解过程中其速度会自发降 低,反应被抑制乃至停止.尽管在热力学上表面能的因素可以赋予小颗粒晶体较大的溶解度 ,但表面能却也能通过对临界条件的控制而使这些微粒在动力学上不被溶解.这个发现不仅 解决了纳米颗粒在水溶液中稳定性的问题,而且还从动力学的角度解释了生物矿物选择纳米 尺度作为其基本构成单元的原因.由于表面能和晶体生长/溶解的动力学有着密切的关系, 我们可以通过对表面能的调节来修改它们的动力学速度和晶体的形貌.反过来,也可以用动力学的方法来测定表面能及表面吸附/脱附常数等.相对于常规的界面研究手段,通过生 长和溶解动力学途径所得的数据有着很好的可靠性及重复性.我们认为,晶体生长和溶解的 动力学和表面能的研究相结合,不仅为界面研究提供了新的思路和方法,而且也会推动晶体生长和材料科学的发展.     

六次甲基四胺与酚类化合物包结现象的研究

Bishop开发的主体化合物1,6-二甲基-1,6-二羟基二环[3,3,1]壬烷可与乙酸乙酯等形成包结物~[1,2],柏木醇通过氢键作用可与酚类化合物形成包结物~[3].比较上述两个主体分子的结构可知,其相似之处在于它们都是桥环化合物,且具有近似球状的分子结构.考虑到六次甲基四胺也是一个球状桥环化合物,且具有与客体分子形成氢键的条件,故它与酚类化合物的包结现象也有助于氢键共晶现象的研究~[4].     

A Dynamic Analysis and Numerical Simulation of Explosive Development of an Extratropical Cyclone Over Land

The present paper has made a dynamic and diagnostic study of the process of explosive deepening of an extratropical cyclone over North China on April 25-26, 1983, in order to gain an insight into the physical mechanism of explosive development of cyclone over land. It turns out that this cyclone occurred in the strong baroclinic zone, and the vorticity and thermal advection triggered the initial development of the cyclone. Subsequently, as the rainfall increased, the effect of condensational heating became more and more important. During the time period of rapid intensification (from 1200GMT 25 to 0000GMT 26 April, 1983, the central surface pressure fell down from 998. 2 to 988. 3 hPa), the peak of diabatic heating profile continuously descended, leading to a rapid increase in heating amount in the lower troposphere. This condition is favorable to the explosive development of rotational circulation or vortex. The numerical simulations have further demonstrated the importance of the lowering of heating p