Computational comparison of two formulations for dynamic supply chain reconfiguration with capacity expansion and contraction

The strategic dynamic supply chain reconfiguration (DSCR) problem is to prescribe the location and capacity of each facility, select links used for transportation, and plan material flows through the supply chain, including production, inventory, backorder, and outsourcing levels. The objective is to minimize total cost. The network must be dynamically reconfigured (i.e., by opening facilities, expanding and/or contracting their capacities, and closing facilities) over time to accommodate changing trends in demand and/or costs. The problem involves a multi-period, multi-product, multi-echelon supply chain. Research objectives of this paper are a traditional formulation and a network-based model of the DSCR problem; tests to promote intuitive interpretation of our models; tests to identify computational characteristics of each model to determine if one offers superior solvability; and tests to identify sensitivity of run time relative to primary parameters.     

Stochastic contraction-based observer and controller design algorithm with application to a flight vehicle

This paper focuses on a stochastic version of contraction theory to construct observer-controller structure for a flight dynamic system with noisy velocity measurement. A nonlinear stochastic observer is designed to estimate the pitch rate, the pitch angle, and the velocity of an aircraft example model using stochastic contraction theory. Estimated states are used to compute feedback control for solving a tracking problem. The structure and gain selection of the observer is carried out using Itô's stochastic differential equations and the contraction theory. The contraction property of integrated observer-controller structure is derived to ensure the exponential convergence of the trajectories of closed-loop nonlinear system. The upper bound of the state estimation error is explicitly derived and the efficacy of the proposed observer-controller structure has been shown through the numerical simulations.     

Czochralski单晶拉制过程中一种自由边界问题整体解的存在唯一性

通过引入由晶体温度u(x,t)和晶体的自由边界s(t)构成的向量空间Sd,以及定义在其上的映射d,研究了基于Czochralski单晶拉制方法的数学模型中一类自由边界问题解的存在唯一性.采用压缩映照原理方法证明了该问题在Banach空间(Sd,d)上局部解的存在唯一性,并利用延拓方法得到了整体经典解的存在唯一性.     

Basic Properties of the Projective Product with Application to Products of Column-Allowable Nonnegative Matrices

We use basic properties of the projective product to obtain exponential bounds for the Lipschitz constant associated with the projective product of column-allowable nonnegative matrices. We obtain similar bounds for the associated linear tangent maps. Date received: May 14, 1998. Date revised: November 18, 1999.     

高拱坝伸缩横缝的开合对拱座岩体稳定的影响研究

高拱坝在强震作用下，伸缩横缝出现开裂，在一定程度上削弱了坝体的整体性能，不仅使得坝体的动力反应重新分布，坝肩岩体抗滑稳定的主要参数一拱端推力也产生很大变化，横缝的存在增加了对坝肩岩体进行抗滑稳定分析的复杂程度。本文给出了用动态子结构法计算有伸缩横缝坝体拱端推力的计算公式，并对坝体设有伸缩横缝的溪洛渡双曲拱坝的计算模型分别在人工地震波及柯依那地震波作用下，考虑库水 坝体相互作用、坝体自重、上游淤沙等因素的影响，对溪洛渡拱坝的拱端推力进行了计算，并通过拱端推力计算了拱座岩体的抗滑稳定安全系数。文中算式同样适用于其它结构。     

Complex response of a sand-bed stream to upstream impoundment

Mangrove Creek Dam, the eighth highest dam in NSW, Australia has induced a complex response of the downstream, sand-bed channel. Since dam closure on 1 October 1981, mean daily flows and the peak instantaneous discharge of floods have been reduced greatly (up to 94 per cent) and nearly 100 per cent of the incoming sediment load has been trapped behind the Dam. The magnitude of the hydrologic effects decreases with distance downstream. River response varies in direct proportion to the magnitude of the altered hydrologic regime and includes alternating but localized bed aggradation and degradation as well as channel contraction. Contraction has occurred by a combination of in-channel bench construction, the formation and bank attachment of longitudinal bars and bank deposition. Leptospermum polygalifolium has rapidly colonized these in-channel deposits and will result in the stabilization of benches. Armouring has not been a significant feedback process to date because of the limited degradation and low gravel supply. It is postulated that the above trends will continue, thus converting the former large, straight, active sand-bed channel into a small, sinuous, well- vegetated sand-bed stream.     

一类常见广义电报方程的概周期解

本文用最大值原理和Banach压缩映像原理研究了一类常见广义电报方程的概周期解问题，证明了该概周期解的存在性及在｜｜u｜｜L-＜1中的唯一性．     

Refined Epistemic Entrenchment

Epistemic entrenchment, as presented by Gärdenfors and Makinson (1988) and Gärdenfors (1988), is a formalisation of the intuition that, when forced to choose between two beliefs, an agent will giveup the less entrenched one. While their formalisation satisfactorilycaptures the intuitive notion of the entrenchment of beliefs in a number ofaspects, the requirement that all wffs be comparable has drawn criticismfrom various quarters. We define a set of refined versions of theirentrenchment orderings that are not subject to the same criticism, andinvestigate the relationship between the refined entrenched orderings,the entrenchment orderings of Gärdenfors and Makinson, and AGM theorycontraction (Alchourrón et al., 1985). To conclude, we compare refinedentrenchment with two related approaches to epistemic entrenchment.     

Simulation of particle migration in free‐surface flows

The migration of particles in free surface flows using the diffusive flux model was investigated. As the free‐surface flows, a planar jet flow and a slot coating flow were chosen. The suspension was assumed to be a Newtonian fluid with a particle concentration dependent viscosity. The governing equations were solved numerically by the finite volume method, and the free‐surface problem was handled by the volume of the fraction model. The result shows that even though the velocity profile is fully developed and becomes flat, the particle distribution never reaches the uniform distribution for both of the cases. It is also shown that the die swell of the free jet is reduced compared to the Newtonian fluid and when the particle loading is 0.5, die contraction is observed. The change in die swell characteristics is purely due to particle migration since the suspension model does not show normal stress differences. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

特大型地下室底板及外墙裂缝控制设计与施工

介绍了某超长超宽特大型地下室底板及外墙的无缝设计与施工情况,认为通过采取适宜的设计及施工措施,超长超宽的地下室底板及外墙不设永久性伸缩缝是可行的。该工程施工期间及建成运营2年多来,均未发现地下室底板及外墙有渗漏现象,是一个非常成功的案例,可供类似工程设计参考。