水平管道中堆积速度的确定

在借鉴已有成果,特别是许振良教授提出的水平管道固体粒子处于滑、跳移时的速度分布模型理论的基础上,结合底层固体颗粒的起动条件,运用数值逼近方法确定堆积速度的计算公式。最后用相关数据对这些公式进行检验,计算结果与实际测量结果较为符合。     

横倾状态下舰船液舱容量计量修正方法研究

本文介绍了横倾状态下舰船液舱容量计量修正方法的研究。重点阐述了利用三次样条曲线拟合和双圆弧样条函数逼近的液舱容量计量计算和修正方法     

非扩张映象的Ishikawa迭代与最佳逼近元

在严格凸Banach空间中研究了非扩张映象T的耦合不动点集F(T)的闭凸性,获得了当F(T)是Hilbert空间中的闭线性子空间时,Ishikawa迭代的极限元与其初始元的最佳逼近元之间的关系.     

尺寸可变的装箱问题的近似算法的研究

给定物品系列,要求将所有物品装入到不同类型的箱子中,以实现从第1个箱子到最后1个箱子被使用的箱子的总尺寸最小化.用最坏情况绝对性能研究在线算法,给出了一种最坏情况绝对性能比是3的近似算法.作为这种算法的应用,给出了一种脱线算法,其最坏情况绝对性能比是2.     

Application of the optimal Latin hypercube design and radial basis function network to collaborative optimization

Improving the efficiency of ship optimization is crucial for modern ship design. Compared with traditional methods, multidisciplinary design optimization (MDO) is a more promising approach. For this reason, Collaborative Optimization (CO) is discussed and analyzed in this paper. As one of the most frequently applied MDO methods, CO promotes autonomy of disciplines while providing a coordinating mechanism guaranteeing progress toward an optimum and maintaining interdisciplinary compatibility. However, there are some difficulties in applying the conventional CO method, such as difficulties in choosing an initial point and tremendous computational requirements. For the purpose of overcoming these problems, optimal Latin hypercube design and Radial basis function network were applied to CO. Optimal Latin hypercube design is a modified Latin Hypercube design. Radial basis function network approximates the optimization model, and is updated during the optimization process to improve accuracy. It is shown by examples that the computing efficiency and robustness of this CO method are higher than with the conventional CO method.     

Norm approximation method for handling traffic count inconsistencies in path flow estimator

Path flow estimator (PFE) is a one-stage network observer proposed to estimate path flows and hence origin–destination (O–D) flows from traffic counts in a transportation network. Although PFE does not require traffic counts to be collected on all network links when inferring unmeasured traffic conditions, it does require all available counts to be reasonably consistent. This requirement is difficult to fulfill in practice due to errors inherited in data collection and processing. The original PFE model handles this issue by relaxing the requirement of perfect replication of traffic counts through the specification of error bounds. This method enhances the flexibility of PFE by allowing the incorporation of local knowledge, regarding the traffic conditions and the nature of traffic data, into the estimation process. However, specifying appropriate error bounds for all observed links in real networks turns out to be a difficult and time-consuming task. In addition, improper specification of the error bounds could lead to a biased estimation of total travel demand in the network. This paper therefore proposes the norm approximation method capable of internally handling inconsistent traffic counts in PFE. Specifically, three norm approximation criteria are adopted to formulate three L_p-PFE models for estimating consistent path flows and O–D flows that simultaneously minimize the deviation between the estimated and observed link volumes. A partial linearization algorithm embedded with an iterative balancing scheme and a column generation procedure is developed to solve the three L_p-PFE models. In addition, the proposed L_p-PFE models are illustrated with numerical examples and the characteristics of solutions obtained by these models are discussed.     

基于NURBS的船体曲面自适应三角网格剖分

针对面向曲面的三维船体性能计算和真实感图形显示问题,应用NURBS曲线、曲面理论,提出一种新颖的船体NURBS曲面三角形网格自动生成算法,运用四角编码方法和改进的曲面片平坦性检验方法,保证在递归分割船体NURBS曲面时,能够快速有效地分割出四边形网格,在曲面片的高度方向和边界处同时满足给定的精度要求,在此基础上,应用割角剖分算法将一个四边形网格剖分成两个或多个三角形网格。应用结果表明,应用该算法生成的三角形平面片能够较好地逼近船体曲面,避免出现网格间的裂缝,与二叉树、四叉树方法相比,四角编码方法明显节省了时间和空间,提高了算法效率。     

Dynamic pricing for managed lanes with multiple entrances and exits

Priced managed lanes are increasingly being used to better utilize the existing capacity of the roadway to relieve congestion and offer reliable travel time to road users. In this paper, we investigate the optimization problem for pricing managed lanes with multiple entrances and exits which seeks to maximize the revenue and minimize the total system travel time (TSTT) over a finite horizon. We propose a lane choice model where travelers make online decisions at each diverge point considering all routes on a managed lane network. We formulate the problem as a deterministic Markov decision process and solve it using the value function approximation (VFA) method for different initializations. We compare the performance of the toll policies predicted by the VFA method against the myopic revenue policy which maximizes the revenue only at the current timestep and two heuristic policies based on the measured densities on the managed and general purpose lanes (GPLs). We test the results on four different test networks. The primary findings from our research suggest the usefulness of the VFA method for determining dynamic tolls. The best-found objective value from the method at its termination is better than other heuristics for all test networks with average improvements in the objective ranging between 10% and 90% for revenue maximization and 0–27% for TSTT minimization. Certain VFA initializations obtain best-found toll profiles within first 5–50 iterations which warrants computational time savings. Our findings also indicate that the revenue-maximizing optimal policies follow the “jam-and-harvest” behavior where the GPLs are pushed towards congestion in the earlier time steps to generate higher revenue in the later time steps, a characteristic not observed for the policies minimizing TSTT.     

NUCLEAR OPERATORS ON C（Ω，X）

ＮＵＣＬＥＡＲＯＰＥＲＡＴＯＲＳＯＮＣ（Ω，Ｘ）ＨｅＣｈｅｎ（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓ）ＡｂｓｔｒａｃｔＴｈｉｓｐａｐｅｒｉｓｔｏｄｅｃｉｄｅｔｈｅｎｕｃｌｅａｒｏｐｅｒａｔｏｒｏｎｔｈｅｓｐａｃｅｏｆｖｅｃｔｏｒ...     

QF18D航空双凸极起动/发电机关键特性研究

起动/发电一体化是现代飞机供电系统的主要发展趋势之一。QF18D航空起动/发电机采用的三相双凸极电机具有转子无磁钢无绕组、结构强度高、制造方便、可逆性好等优点,适于高空高速飞行的应用条件。文章首先扼要介绍了QF18D发电及电动工作的结构原理;然后基于有限元仿真和实验验证相结合的方法详细研究了QF18D双凸极直流发电机的空载、短路、外特性和调节特性的特点,主要探讨了换相重叠和电枢反应对电机关键特性的影响机理;最后通过航空涡喷发动机的冷热开车试验验证了QF18D的系统起动性能优越。