混沌态下的四则运算

基于1-D分段线性映射函数构造的混沌系统符号动力学,并结合混沌轨道的距离定义,探讨了混沌符号序列与二进制序列之间的相互关系.并在此基础上提出了利用混沌符号轨道间相互的“加减乘除”四则运算来得到另一混沌轨道符号序列的方法.最后通过FIR数字滤波器卷积操作的计算机数值仿真,结果表明采用这些方法运算得到的结果与传统二进制算术编码算法完全等效,可应用于混沌信号处理系统.     

CFD技术在三体船阻力性能研究中的应用

三体船作为一种新型的高性能船型,由于其出色性能而受到越来越多的重视.同时,三体船型仍不是一种成熟的船型,对它的研究和应用还面临很多难题.文中在粘性理论的范畴内,将目前较流行的CFD技术应用于三体船的阻力性能研究中,在考虑自由水面效应的前提下,模拟了2种三体船构型在不同航速下的粘性流场,与三体船模型水池拖曳试验结果相比较,采用CFD技术模拟的结果是合理的.表明CFD技术可以在三体船型水动力性能研究中发挥重要作用.计算与试验结果在高Fr数段的较明显偏差表明对应用的方法或者算法本身有改进的必要.     

焦化废水亚硝化过程的动力学研究

在用亚硝化-厌氧氨氧化组合工艺处理焦化废水时,亚硝化的动力学研究对好氧反应器构筑物的设计及运行具有重大指导意义.根据亚硝化菌与硝化菌世代周期的不同,利用劳伦斯-麦卡蒂模型研究焦化废水亚硝化的动力学参数,求得vm ax=2.03 mgNH4 -N.mgVSS-1.d-1,Ks=22.07 mgNH4 -N.L-1,Y=0.257 4 mgVSS.mgNH4 -N-1,Kd=0.086 4 d-1.利用所得的动力学模型分析曝气池内生物量浓度与污泥龄的关系,根据多组试验数据得到二者之间的相关关系式.     

环境激素邻苯二甲酸丁基苄酯的动力学

采用同位素标记方法示踪环境激素邻苯二甲酸丁基苄酯的生物转运过程,用NDST21动力学处理软件判断房室模型,建立邻苯二甲酸丁基苄酯的数学模型,计算各种参数.实验结果表明:3H-BBP经口染毒后被迅速吸收,5 min即在血中检测出,0.5 h达高峰,并呈一级动力学线性过程,符合二室开放模型;测得吸收半衰期约为13 min,分布半衰期约为25 min,消除半衰期约为7 h,说明该化合物的吸收和分布较快、消除较慢;3H-BBP的主要排泄途径是从尿和粪中排泄,在4 d之内从尿和粪累计排泄量占染毒量80%左右.     

乙烯-醋酸乙烯酯的结构与降凝性能的关系

用溶液聚合法合成了各种结构的乙烯-醋酸乙烯酯共聚物(EVA)降凝剂,考察了它们的结晶性质、溶解性质和降凝效果.由实验得到以下结论:EVA降凝剂的CH2链上只有远离极性基团的碳原子能够参与结晶.当参与结晶的碳原子数约等于原油中蜡的平均碳原子数的3/4时,EVA降凝剂的降凝效果最好.EVA降凝剂的相对分子质量分布的宽窄对降凝效果的影响不大,平均相对分子质量在1.2×104时降凝效果较好.     

Rigidly connected overlapping spherical particles: a versatile grain model

This paper describes a method to simulate the dynamics of granular systems consisting of irregularly shaped grains. This method is a simplification and partial improvement of a method that has been developed and employed earlier in simulating the toning process in electro-photographic copiers. Here, grains are modeled as rigidly connected overlapping spherical particles. For each grain a bounding sphere around the center-of-mass is known. Therefore, it can efficiently be decided whether two particles intersect and thus exert contact forces upon each other. A second order time stepping algorithm for such grains is given which needs only one evaluation of the interparticle forces in a time step. In a ten grain example system a favorable but poorly understood phenomenon of energy restoration is exemplified.U. Mutze retired from R&D for a subsidiary of Heidelberger Druckmaschinen AG, after R&D work for a subsidiary of Eastman Kodak Company.     

Buckling dynamics of imperfect Elastica subject to various loading conditions

Buckling dynamics of a pinned-pinned flexible imperfect beam attached to a sliding mass is investigated using nonlinear Elastica theory. Initially straight flexible buckling beam having pinned end boundary conditions loaded at one of its end with curved imperfection is considered. Large deflection analysis of flexible beam is studied using nonlinear Elastica theory. Imperfection analysis of the flexible beam is investigated considering the imperfection as an initial curvature. The governing differential equations are expressed in terms of nonlinear functions that are typical of flexible beams, generally leading to highly implicit relationships involving elliptic integrals and functions. Dynamic simulation of the flexible beam is studied using numerical simulation procedures with various types of loading (step, ramp, and sinusoidal) assuming this member buckles in its first mode. Dynamic response of the imperfect buckling Elastica has been obtained by using numerical Runge-Kutta methods. Load deflection characteristics of flexible beams are presented in polynomial curve fits. The polynomial curve fits obtained from nonlinear inextensible exact beam theory may then be used as the nonlinear lumped system stiffness. The buckling Elastica may find applications in compliant mechanism design. The motivation behind this research is not only to present the dynamic behavior of the buckling beam considering the magnitude of the imperfection but also to provide a tool to design new types of compliant mechanisms. Original compliant mechanism designs are presented demonstrating where the buckling dynamics of imperfect Elastica or flexible curved beams might be needed in mechanism design and synthesis.     

A combined dislocation—cohesive zone model for fracture in a confined ductile layer

The collective dislocation behavior near a crack tip in a ductile layer sandwiched between two brittle solids is analyzed via two-dimensional dislocation dynamics (DD) simulations that incorporate a cohesive zone (CZ) model. The cohesive crack tip is treated as part of a much larger finite crack confined in the ductile layer. The underlying boundary value problem is formulated with a set of boundary integral equations and numerically evaluated with a collocation method. The fracture energy of the layered composite material is shown to be strongly correlated with the layer thickness and is directly influenced by the cohesive strength of the ductile layer (Hsia KJ et al. (1994) J Mech Phys Solids 6 877–896).     

纳米水平热量传输中温度定义的讨论

纳米水平热量传输明显不同于宏观和微观系统的热量传输。由于热量携带子——电子、光子、声子或分子的平均自由行程与被研究物体的特征长度之间具有可比性，经典理论已经不再适用，人们必须采用新的理论来预测纳米水平的热量传输。在许多仿真模型的研究中存在对温度定义的分歧，因此出现不同的研究结论。针对于在仿真模型研究中可能出现的有关温度的定义给出了明确阐述。     

C32C60C180、C60@C180富勒烯分子的压缩力学特性

采用Tersoff-Brenner势与L—J势的分子动力学方法，研究了双石墨层作用下C32、C60、C180以及C60@C180富勒烯分子的压缩力学特性。根据计算结果，讨论了几种富勒烯压缩过程中的变形、能量、压缩栽荷等的变化及其差异。研究表明，由于分子几何构形上的差异，压缩时，C180出现了明显的“塌陷”现象，“塌陷”过程中，能量及外载荷一度下降；几种富勒烯压缩时的能量吸收能力排序为：C32〉C60〉C60@C180〉C180，承载能力的排序为：C60@C180〉C180〉C60〉C32。