形成人工血栓的Chandler圆环内的流动分析

本文应用流体力学方法对Chandler 圆环内人工血栓形成的流动情况进行了细致分析。结果表明,形成血栓的下弯月面附近是一个既有迴流,又有二次流的区域,而且迴流的中心主流冲击着弯月面,为颗粒的聚集提供了有利的条件。本文对分析与血液流动有关的人工脏器和体内血栓形成的机理有一定的价值。     

相关攻击与相关免疫函数

本文首先介绍了如何采用ＤＣ攻击法对一类流密码体制进行相关攻击，从而说明在密码学中有必要研究相关免疫（ＣＩ）函数。在综述了域Ｆ２上相关免疫（ＣＩ）函数的研究进展的同时，给出了ＣＩ函数在一般有限域上的特性和构造，并进一步研究有限环Ｚ／（ｍ）时的情景，本文详尽描述了ＣＩ函数的五种充要条件。最后提出了几个值得研究的未解决的问题。     

新星爆发后赤道带形成的电流环模型

本文用双绝热磁流体方程组阐明新星爆发后主壳层向赤道面运动的规律,当主壳层在强偶极磁场作用下向外抛射时,由漂移电流产生平行于赤道平面的等离子体电流环,它们在磁场作用下向赤道面逐渐靠拢形成赤道带;在极冠区由于等离子体流速与磁场平行,不能产生电流环而形成单独的极冠凝块,极冠凝块与赤道带速度的差异是由于等离子体流横越磁场时感应电场能量的消耗。根据本文提出的电流环模型,对于新星DQ Her作了估算:新星爆发时的磁场约为10⁶—10⁷高斯,赤道带形成的时间约为4—6年,与观测大致相符,文中还提供了观测上进一步检验模型的一些方法。     

有限流体域内不同位置处的柔性管涡致振动机理研究

针对有限流体域内柔性管的涡致振动问题,将柔性管离散为若干空间梁单元,流体域采用实体单元离散,建立了有限流体域内柔性管系统的流固耦合模型及数值计算方法,设计并加工圆柱流体域内柔性管振动专用实验装置,采用GWT-2B双轴加速度传感器对柔性管的振动进行监测,并与数值模拟结果进行对比,吻合程度较好.基于该文的模型和方法,对圆柱流体域内不同位置处柔性管的涡致振动机理进行研究.结果表明,柔性管偏离入口流速位置的角度越大,越容易发生流体弹性不稳定性,柔性管的振动愈剧烈;而正对入口流速的位置,不易发生流体弹性不稳定性,柔性管振动减弱.     

恒磁场对刚性圆直管中脉动流的影响*

本文研究了恒磁场对于刚性圆直管中脉动流的影响,并根据现有的实验资料考虑了磁场对于血液粘度的影响,给出了恒磁场作用下刚性圆直管脉动流的分析解以及恒磁场对刚性圆直管中的流速分布、流量以及阻抗的影响的计算结果.这些结果对于深入研究磁场对于血液动力学的影响具有一定参考价值.     

磁场对具有压力梯度的低频振荡自然对流的影响

研究了磁场对具有非定常压力梯度的振荡自然对流的影响．假设流体是在两平行板内流动．由于在航天材料中的重要性，重点研究在微重力作用下由于矿振荡器诱发的低频振荡自然对流．得到了在非定常磁场下的振荡流体的一般解．还给出了一些特殊的振荡流和对作用磁场的响应．发现振荡流的性质依赖于频率、驱动浮力的振幅、温度梯度、磁场、壁面的导电情况．当没有磁场时，浮力在驱动流体振荡中起主导作用，并且速度的大小还受温度梯度的影响．为了控制振荡流，可以应用外磁场．还发现：当壁面是导体时，速度的减小与作用磁场的平方成反比；当壁面是绝缘体时，速度的减小与作用磁场成反比．一些详细的计算结果反映了真实的状态．     

有限长螺管对高频等离子体电磁场的端部及匝间效应

在实际应用中,高频等离子体发生器感应螺管的高度一般与螺管的直径大小相近,因此在高频等离子体理论计算中螺管端部对等离子体电磁场的影响不容忽视.本文在等离子体为均匀电导率、无限长直圆柱的假设下,求解了它在有限长分离螺管中的电磁场分布,得到一些新的结果.指出,等离子体轴心处的磁场与空心螺管轴心处的有很大不同,甚至会出现逆向磁场;而在等离子体半径处的磁感应强度值仅稍大于空心螺管时的值,且其相位差与空心螺管时的也相差甚微.应用此处的空心螺管电磁场作为高频等离子体计算中电磁场的边值条件与实际更为接近.     

一般系统结构理论与人体血液自然运动环行为关系定理

在人体血液自然运动过程中,人活体内存在顺时针的血液自然运动,由于静脉血液成分在其起源处成分不同,存在自然分类,这也就形成了多个以不同成分进行顺时针运动的血液自然运动环,这些不同成分的血液自然运动环在自然交汇的过程中就会自然发生关系,应用一般系统结构理论研究这些活体血液自然运动环之间的关系,得出人体血液自然运动环关系定理及血液自然运动环之间关系的模型,应用一般系统结构理论,研究人体血液复杂自然运动环网络的关系流,包括肠系膜上静脉流、肠系膜下静脉流、脾静脉流、肝静脉流、肾静脉流、下腔静脉流、上腔静脉流等和人体血液复杂自然运动环网络行为或功能之间的关系及规律,将推动人体血液复杂自然运动环网络的研究.     

RRA环及其不动子环

本文讨论了Camillo和Krause所定义的RRA环的一些性质，进而研究了RRA环在某些特殊的有限自同构群作用下的不动子环的环论性质．     

Hartmann共振管及超音速雾化喷嘴

采用基于Roe解法的有限体积法，对Hartmann共振管中的气体流场进行了数值模拟，研究了当喷嘴轴线处存在针型激励器的情况下流场的振动情况，数值计算的结果与理论和相关的实验结果符合得较好．计算结果表明移除或引入激励器，将会使Hartmann共振管的共振模式发生转换．通过对超音速雾化喷嘴流场的数值模拟，研究了其中Hartmann共振腔和二级共振腔共同作用下的振动现象以及各物理参数对振动的影响，并对喷嘴中气流从亚音速向超音速的转变机理进行了研究．     

Magnetic field effects on Newtonian and non-Newtonian ferrofluid flow past a circular cylinder

The changes in the flow properties under the action of electromagnetic body forces are investigated numerically for ferrofluid flow past a circular cylinder. Ferrofluid is modeled as both a Newtonian and a non-Newtonian Power-Law fluid. Magnetic forces are applied by placing magnets at different locations on the surface of the cylinder. The magnetostatic effects on the structure of the wake region, on drag reduction and on vortex formation length and frequency are shown and compared in terms of Reynolds number, interaction parameter, Power-Law index and magnet location. It is shown that the increase in the interaction parameter reduces drag for both Newtonian and non-Newtonian model. This decrease is observed to be higher for shear thinning and lower for shear thickening fluid compared to Newtonian case. It is also shown that vortex street formation in the wake region behind the cylinder may be delayed under high magnetic effects. The Strouhal number is higher for shear thinning case at both low and high Reynolds numbers, and lower for shear thickening case at high Reynolds numbers, compared to Newtonian fluid. The vortex formation frequency also decreases under the action of the magnetic field in all cases, however the vortex formation length increases. Placing the magnet towards the front region of the cylinder increases considerably the drag coefficient for both Newtonian and non-Newtonian model. This increase in drag coefficient is higher in the shear thinning fluid and lower in the shear thickening fluid compared to the Newtonian case.     

Coupled wetting meniscus model for the mechanism of spontaneous capillary action

Capillarity plays a significant role in many natural and artificial processes, but the mechanism responsible for its dynamics is not completely understood. In this study, we consider capillary flow characteristics and propose a coupled wetting meniscus model for the mechanism of spontaneous capillary action. In this model, capillary action is considered as the dynamic coupling of two interfacial forces, i.e., the wall wetting force at the contact line and the meniscus restoring force on the free interface. The wetting force promotes the motion of the contact line directed toward an equilibrium contact angle, whereas the meniscus restoring force promotes a reduction in the interface curvature, which is more consistent with a 90° contact angle. The competing interaction between these two forces is coupled together via the evolution of the interface shape. The model is then incorporated into a finite volume method for a two-fluid flow with an interface. Capillary flow experiments were performed, including vertical and horizontal flows. Phenomena analysis and data comparisons were conducted to verify the proposed model. According to the results of our study, the model can explain the capillary flow process well and it can be also used to accurately guide capillary flow calculations.     

Global existence and asymptotic analysis of weak solutions to the equations of Ferrohydrodynamics

In this paper, we consider the three-dimensional equations of Ferrohydrodynamics describing the motion of an incompressible ferrofluid under the action of an external magnetic field. We first consider the system introduced by Rosensweig. We establish the existence of globally defined finite energy weak solutions and also investigate the large-time behavior of such solutions. Then we study the asymptotic behavior of the solutions as some physical parameters in the angular momentum equations tend to zero, we prove that the limit functions will be weak solutions of the equations proposed by Shliomis. This shows rigorously the exact relationship of these two principal systems which describe the motion of ferrofluids.     

The development and interaction of terrorist and fanatic groups

Through the mathematical study of two models we quantify some of the theories of co-development and co-existence of focused groups in the social sciences. This work attempts to develop the mathematical framework behind the social sciences of community formation. By using well developed theories and concepts from ecology and epidemiology we hope to extend the theoretical framework of organizing and self-organizing social groups and communities, including terrorist groups. The main goal of our work is to gain insight into the role of recruitment and retention in the formation and survival of social organizations. Understanding the underlining mechanisms of the spread of ideologies under competition is a fundamental component of this work. Here contacts between core and non-core individuals extend beyond its physical meaning to include indirect interaction and spread of ideas through phone conversations, emails, media sources and other similar mean. This work focuses on the dynamics of formation of interest groups, either ideological, economical or ecological and thus we explore the questions such as, how do interest groups initiate and co-develop by interacting within a common environment and how do they sustain themselves? Our results show that building and maintaining the core group is essential for the existence and survival of an extreme ideology. Our research also indicates that in the absence of competitive ability (i.e., ability to take from the other core group or share prospective members) the social organization or group that is more committed to its group ideology and manages to strike the right balance between investment in recruitment and retention will prevail. Thus under no cross interaction between two social groups a single trade-off (of these efforts) can support only a single organization. The more efforts that an organization implements to recruit and retain its members the more effective it will be in transmitting the ideology to other vulnerable individuals and thus converting them to believers.     

A finite element scheme for domains with corners

This paper is concerned with the rate of convergence of the finite element method on polygonal domains in weighted Sobolev spaces. It is shown that the use of different spaces of trial and test functions will restrict the usual low rate of convergence to a neighborhood of each vertex of the polygonal domain.L ₂-convergence and lower bounds on the error are also studied.This research was supported in part by the Atomic Energy Commission under contract no. AEC AT-(40-1)-3443/4.This research was supported in part by the U.S. Naval Academy Research Council.     

Collective bargaining: A differential game

Earlier differential game models of collective bargaining deal only with the strike phase. The model proposed here allows for negotiations without and with a strike.This paper is based on research supported by NSF under Grant No. GP-24205.     

Blow-up phenomena for a semilinear heat equation with nonlinear boundary condition, II

This paper deals with the blow-up of the solution to a semilinear second-order parabolic equation with nonlinear boundary conditions. It is shown that under certain conditions on the nonlinearities and data, blow-up will occur at some finite time and when blow-up does occur upper and lower bounds for the blow-up time are obtained.     

Propagation of nonlinear magnetoacoustic waves in a compressible medium of finite electrical conductivity

We study the one-dimensional propagation of weakly nonlinear waves in a compressible medium of finite electrical conductivity subjected to the action of a magnetic field. We obtain evolution equations that describe the wave processes under small and finite magnetic Reynolds numbers. It is shown that in a medium of finite conductivity the evolution of perturbations in a fluid is described by the modified Bürger's equation. We find the stationary and automodel solution of this equation and use them as the basis for analyzing the influence of effects of electrical conductivity on the structure of weak shock waves.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 32, 1990, pp. 73–76.     

Inventory control by different service levels

This paper examines the multiple period inventory control problem of a single product with multiple (two) prices, depending on service level, in which optimal pricing and ordering decisions are made in each period. Traditional inventory and pricing models consider only single products, single prices, and single service levels. However, this research paper finds that a seller can improve inventory control and revenue by offering multiple prices depending on service level. This research considers a single product with multiple (two) pricing policies corresponding to service level as follows: if the customer is willing to delay the shipment, he/she will be offered a lower regular price. Otherwise, the customer will pay the regular price plus extra charges for express service. In this paper, I show the following: (1) there is an optimal pricing and replenishment policy that can control inventory and (2) there exists a finite threshold for inventory levels such that if the inventory level at the beginning of each period is higher than the threshold, the customer will be offered the express service at the regular price, without any extra charge.     

Blow-up phenomena for a system of semilinear heat equations with nonlinear boundary flux

This paper deals with the blow-up for a system of semilinear r-Laplace heat equations with nonlinear boundary flux. It is shown that, under certain conditions on the nonlinearities and data, blow-up will occur at some finite time, and when blow-up does occur upper and lower bounds for the blow-up time are obtained.