Fisher类方程孤波解的新求法

本文给出了求解Ｆｉｓｈｅｒ类方程孤波解的一种新方法——待定参数法．每个方程可得到两族孤波解     

An ECN-based Optimal Flow Control Algorithm for the Internet

According to the Wide Area Network model, we formulate Internet flow control as a constrained convex programming problem, where the objective is to maximize the total utility of all sources over their transmission rates. Based on this formulation, flow control can be converted to a normal unconstrained optimization problem through the barrier function method, so that it can be solved by means of a gradient projection algorithm with properly rate iterations. We prove that the algorithm converges to the global optimal point, which is also a stable proportional fair rate allocation point, provided that the step size is properly chosen. The main difficulty facing the realization of iteration algorithm is the distributed computation of congestion measure. Fortunately, Explicit Congestion Notification (ECN) is likely to be used to improve the performance of TCP in the near future. By using ECN, it is possible to realize the iteration algorithm in IP networks. Our algorithm is divided into two parts, algorithms in the router and in the source. The router marks the ECN bit with a probability that varies as its buffer occupancy varies, so that the congestion measure of links can be communicated to the source when the marked ECN bits are reflected back from its destination. Source rates are then updated by all sessions according to the received congestion measure. The main advantage of our scheme is its fast convergence ability and robustness; it can also provide the network with zero packet loss by properly choosing the queue threshold and provide differentiated service to users by applying different utility functions.     

色散方程的显式与半显式差分格式

(一)引言 近年来,由于孤波的产生,引起人们对Kdv方程,从而对色散方程U_1=aUxxx的浓厚兴趣。对于其三层显格式构造稳定性经由文献[1]的|r|=|at/h~3|≤0.3849(t,h分别为时间和空间方向的步长),[2]的|r|≤0.7016提高到[3]的|r|≤1.1851,本文利用文献[4]中所谓加进耗散项的方法,构造出显式与半显式的差分格式。     

钢纤维混凝土栓钉—橡胶组合连接件抗剪刚度分析

为建立钢纤维混凝土(steel fiber reinforced concrete, SFRC)栓钉-橡胶组合连接件抗剪刚度设计计算方法,结合已有文献推出试验,采用ABAQUS显式准静态求解技术进行非线性有限元分析,仿真计算结果与文献推出试验结果基本吻合。以橡胶套高度、橡胶套厚度、混凝土强度和栓钉直径为影响参数,分析组合连接件抗剪刚度变化规律,并结合现有栓钉抗剪刚度计算式拟合出SFRC栓钉-橡胶组合连接件抗剪刚度设计计算公式。结果表明：ABAQUS显式准静态求解技术能较好地实现组合连接件推出试验数值模拟;采用橡胶套包裹栓钉后会大幅降低连接件抗剪刚度,抗剪刚度最大降幅约为60%;当橡胶套高度为25 mm、厚度为2.5 mm时,即可显著降低连接件抗剪刚度;钢纤维混凝土强度对抗剪刚度影响较小;组合连接件抗剪刚度与栓钉直径近似呈正比关系;提出的抗剪刚度设计计算式能较准确预测钢纤维混凝土栓钉-橡胶组合连接件抗剪刚度,为工程设计提供参考与借鉴。     

空时分数阶mBBM方程的新精确解

为了构造时空分数阶mBBM方程的新显式解, 本文首先利用分数阶复变换技巧将分数偏微分方程转化为常微分方程, 然后应用扩展的(G''/G)-展开法求解该常微分方程. 新精确解包括分别带有负幂次项的三角函数解, 双曲函数解及有理函数解.     

ABAQUS显式分析方法在钢筋混凝土结构中的应用

为了考察ABAQUS显式分析方法在钢筋混凝土结构上应用的适用性和准确性,用显式与隐式两种分析方法对迭代算法和求解时间进行了对比,并且对钢筋混凝土悬臂梁分别进行了隐式和显式模拟分析.用结果曲线详细地对比可知,显式分析方法能够在解决材料失效和破坏导致的收敛问题的基础上,较为准确地模拟钢筋混凝土结构响应.最后,给出了采用显式分析参数定义时的注意事项及判定分析结果稳定性的方法.     

Hirota-Satsuma方程的Darboux变换解

通过建立Lax对之间的规范变换,得到了Hirota-Satsuma方程的达布变换。作为应用,还得到了该方程的有理解,孤子解等。     

Improving TCP Performance over Wireless Links Using Link-Layer Retransmission and Explicit Loss Notification

In order to support the mobility of computers during communication, the transport control protocol (TCP) connections between fixed host and mobile host often traverse wired and wireless networks, and the recovery of the losses due to wireless transmission error is much different from congestion control. This paper analyzes the interaction between TCP and link layer retransmission scheme when the correlated packet are losses handled, indicates that a higher value of the maximum number of successive link layer timeout retransmissions has an adverse effect on TCP ability to perform congestion control rapidly. To achieve a better TCP performance, the paper proposes a strategy combining link-layer selective-reject automatic repeat request (ARQ) with explicit loss notification mechanism, which can respond to congestion quickly while keeping wireless link more reliable, and make TCP react to the different packet losses more suitably.     

Knowledge transfer across scientific disciplines

Thomas Kuhn suggested that symbolic generalizations are applied to concrete systems by a process involving exemplars and analogical reasoning. Using the related concepts of theoretical and formal templates, I argue that the process of applying templates can in some cases be made explicit and that we do not need to rely on similarity relations and tacit knowledge. In so doing I show how some formal models can be transferred from one scientific field to another. Examples include scale-free networks, the Lotka-Volterra model from biology, and the Goodwin model in economics. I also argue that this explicit approach has advantages over the more psychologically oriented approach of Kuhn and explain the sense in which templates do and do not produce unification.     

Concept of Compound-Agent and Its Application

The novel concept of Compound-Agent is proposed, which consists of some independent sub-agents that share common beliefs and employ community actions. The Explicit Model of Coordination, which is used in the coordination of the sub-agents of Compound-Agent, is provided. The actions of each sub-agent are rule-based determined, and the rule base can be adjusted on time. The approximate fuzzy reasoning is used to improve the speed of learn and reduce the number of rules, which makes Compound-Agent suitable for real time and dynamic applications. A real application, the design of the control system of flat-knitting machine employing the concept of Compound-Agent, is discussed briefly.