活动星系核宽线区标准模型的谱线轮廓

在标准宽线区模型的框架下,根据光致电离理论,通过构造细致的发射线云团的辐射结构,计算了活动星系核光谱中,Lya和CIVλ1549两条重要紫外宽发射线的轮廓,并根据所得谱线轮廓的特征,讨论了宽线区模型中的两相介质理论和运动学状态等影响谱线发射和谱线轮廓的主要物理因素.主要结论是,如果宽线区的运动学状态是引力所主导的径向内流,则当宽线区中存在一定的热相介质(其粒子数密度n_h≈2×10⁵cm^-3)时,所得理论谱线轮廓与观测特征符合的较好;如果对宽线区尺度进行合理的截取,Lya和CIVλ1549的理论谱线轮廓都向蓝端有一定的峰移,这可以用来定性解释活动星系核的观测谱中,高电离谱线和低电离谱线有系统性红移差别的现象.     

有限元线法的误差估计

有限元线法(FEMOL)是近年来由英国伦敦中心理工学院Sir G.Cayley研究所和清华大学土木系共同提出并发展起来的,以常微分方程求解器为支撑软件的新型半离散数值方法。该方法简便、灵活,对区域的适应性较强。大量的数值试验结果表明,它具有较高的精度。它兼有有限元法,线法、有限条法以及康托洛维奇法等的一些特点和优点,行之有效。本文拟对该法作一些理论分析,证明半离散常微分方程组解的存     

三维有限元本征值的外推

通过二维和三维积分恒等式,探讨泊松方程本征值问题三角线元和四面体线元Richardson外推的可行性.理论分析表明,如果剖分为均匀一致和拟一致,外推均可将解的精度提高二阶.     

横观各向同性体滑移线场理论

本文系统推演了横观各向同性体滑移线场理论.为解决地球动力学与岩土力学问题,考虑到成层地质体横观各向同性与非均匀温度场作用,本文选择了Gol'denblat-Kopnov破坏准则.并使物性参数随温度变化,建立了复杂介质的强度准则.通过关联流动法则,导出了塑性流动基本方程.应用特征线理论,导出了滑移线斜率公式、应力沿滑移线微分公式和速度沿滑移线微分公式.应用本文理论计算了基础承压问题.本文理论将许多着名的经典理论如Mises理论,Hill理论、Coulomb理论概括为特例.这一综合理论可应用于岩土工程、地质构造、石油、采矿等许多领域.     

层焰系统奇点结构的研究

在一定的假设条件下,将气体燃烧的物理模型简化为层焰系统．借助于热力学理论和相关的守恒定律建立了层焰系统的数学模型并对其进行了深入地分析．利用常微分方程的定性理论和方法,结合燃烧的实际需要,对应于参数的不同取值,研究了位于瑞利线上奇点的个数和位置,确定了暴燃区和爆炸区内不同奇点的定性结构及其稳定性,给出了在反应速度-滞止焓平面及燃烧速度-滞止焓平面内层焰系统轨线的相图．     

分子线伏-安特性第一性原理

发展了一套理论方法用于描述分子线的伏-安特性. 在该弹性散射Green函数方法中, 分子的电子结构和分子与金表面的相互作用能常数决定了分子线的伏-安曲线. 从第一性原理出发利用密度泛函理论计算了4, 4′-二巯基联苯分子的电子结构, 并利用了前线轨道理论和微扰理论定量地确定了该相互作用能常数. 研究结果表明当含有硫氢官能团的有机分子化学吸附于金表面时, 硫原子将与金原子形成以共价键为主的混合键, 此时扩展的分子轨道使分子线的电导呈现出欧姆特性. 而对于局域的分子轨道, 此时电子的输运只能通过隧道效应来实现. 对分子线伏-安特性的计算结果显示, 在零偏压附近, 存在一个电流禁区. 随着偏压的增加, 分子线的电导呈现出平台特征. 该工作将有利于未来的纳米电子学器件的设计.     

类星体和SeyfertⅠ型星系的Balmer减缩

本文收集了低红移类星体和Seyfert Ⅰ型星系的各Balmer线强度资料,在Cerenkov线辐射理论的框架下,比较了理论预言值和观测值,发现对有射电的类星体或Seyfert星系,它们的观测值都要比相应的射电宁静样本更靠近理论预言值。这表明,有射电的活动星系核,由于存在丰富的相对论电子,它们的Balmer线的Cerenkov线辐射特征更为明显。我们还讨论了存在于类星体和Seyfert星系中的尘埃红化问题,对Seyfert星系,其红化比类星体厉害,这表明它比类星体有更多的尘埃,这与目前一般的观点是相符的。     

凸二次-线性双层规划的共轭对偶及其性质

研究具有一般形式的凸二次-线性双层规划问题。讨论了这类双层规划问题的DC规划等价形式,利用DC规划共轭对偶理论,提出了凸二次-线性双层规划的共轭对偶规划,并给出相应的对偶性质。     

圆柱圆锥正交相贯的数学模型及其交线画法

在工程制图中,圆柱圆锥正交相贯时,其交线上的某些特殊点总是近似求出.以正投影理论为基础,以圆柱圆锥正交相贯的数学模型为依据,提出了一种准确、简便、可靠的求解方法.方法对于手工或计算机准确绘制该交线、对圆管平交正锥台三通下料等工程问题,都很有实用价值.     

一种裂纹梁振动响应分析和近似方法

本文以线弹簧模型为基础提出了一种近似分析裂纹梁振动响应的方法。把该方法同Ｅｕｌｅｒ－Ｂｅｒｎｏｕｌｌｉ梁理论，模态分析方法以及断裂力学原理等结合起来运用。导出裂纹梁振动的特征方程。     

R^3中曲率线为球面曲线的曲面

用Ｅ．Ｃａｒｔａｎ的外微分系统理论，研究了Ｒ＾３中一族（或两族）曲率线为球面曲线的曲面的模空间。     

Projection methods for the solution of one class of singular integrodifferential equations

In this paper we propose a computational scheme of the general projection method for the solution of singular integrodifferential equations in the theory of stream lines and thermal conductivity. We theoretically substantiate this scheme from the standpoint of the theory of approximate methods of functional analysis. We consider particular cases of the general projection method, namely, the method of moments and the collocation method.     

Counting bitangents with stable maps

This paper is an elementary introduction to the theory of moduli spaces of curves and maps. As an application to enumerative geometry, we show how to count the number of bitangent lines to a projective plane curve of degree d by doing intersection theory on moduli spaces.     

用线法分析中厚板的振动与稳定性问题

发展了基于胡海昌中厚板的振动与稳定性理论等特征值问题的线法.利用常微分方程(ODE)技巧给出求解固有频率及临界荷载的标准非线性ODE体系,并采用所谓初始特征函数法通过ODE求解器(Solver)直接解出指定的任一特征值,而不依赖于振型正交性等条件.算例表明,本文方法是有效和可靠的.     

准对称流的混沌和共振流线

采用计算Melnikov函数的方法 ,研究了描述qth(q=3或 6 )准对称流流体粒子运动的动力系统 .文中在分析未扰动系统轨道解析表示的基础上 ,深入考察了扰动系统的分岔情况 .结果表明 ,扰动系统在一定条件下能够分支出混沌和共振流线 .     

A model for the configuration of incoming wats lines

WearGuard is a direct marketer and retailer of uniforms and work cloths, which relies primarily on phone orders for sales. For this purpose it maintains a series of toll-free 800-number lines, known as WATS lines, to receive its incoming calls. These lines are of several types, where each type serves a different portion of the country and has a different usage fee. In this paper we determine how many of each type of WATS lines should be employed. After defining the problem more completely, we develop a queueing model to describe the system and a dynamic program to solve the configuration problem to optimality. The model has been applied to the problem by WearGuard since 1984. We present an example and examine the sensitivity of the solution to variations in various parameters. We validate the model by comparing the results of this model to other approximate models.Formerly: WearGuard, Director of Decision Support Systems, Longwater Drive, Norwell, MAmis 02061, USA     

Properties of serial kanban systems

In this paper we show some structural results of a kanban system by using results about the underlying GSMP. The main results from this connection are: dominance of allocations, optimal partition, upper and lower bounds on throughput, consistency of the IPA derivative, convexity of throughput as a function of service time parameters and concavity of throughput with respect to number of kanbans. Although the dominance and the partition results were obtained previously by sample path arguments, the proofs here are less cumbersome and generalize the earlier results. The second-order properties for kanban lines are new. These results form a basis for results in multi-product lines where proofs by sample paths require extensive notation.     

Asymptotic loss of priority scheduling policies in closed re-entrant lines: A computational study

In this paper we present an approximate but efficient analytical method to compute the asymptotic loss of buffer priority scheduling policies in closed re-entrant lines. For simple two-station closed re-entrant lines, this enables the verification of Harrison-Wein conjectures and Jin-Ou-Kumar resuts. For multi-station re-entrant lines, this provides an efficient way of comparing different buffer priority scheduling policies. We also use the method to evaluate the effect of high priority jobs in re-entrant lines.     

高速水面舰船型线的数学模型

提出了一种应用数学模型构建高速水面舰船船型的设计方法.该"数学船型"方法根据舰船的应用特性确定船型曲线的几何性质及应满足的定解条件,应用定解条件确定船型曲线的形状函数或型值函数,从而生成所需船型曲面.实验表明,"数学船型"方法无需型值即可得出设计舰船的型值表、型线图和任意视向的立体船图,且能保证船体的浮性、稳性和具有最小阻力等重要性能.方法可用于舰船设计的初始阶段,在与"数学船池"连接后,易于对船型做优化设计.     

Poisson Broken Lines Process and its Application to Bernoulli First Passage Percolation

In this note we introduce a process, which we call 'the Poisson broken lines process", and we compute the intensity of a point process which is obtained by intersecting the Poisson broken lines process with an abscissa axis. In the second part we apply this result to compute an explicit lower bound for the time constant of a planar Bernoulli first passage percolation model with the parameter p < p_c.