A route set construction algorithm for the transit network design problem

The transit network design problem (TNDP) aims to determine a set of bus routes for a public transportation system, which must be convenient from the viewpoints of both users (people who use public transportation) and operators (companies who own the resources to give the service). This article presents a constructive algorithm for the TNDP. It is specially designed to produce a set of routes that fulfils demand covering constraints, while taking into account the interests of both users and operators. Its general structure is inspired in the Route Generation Algorithm (RGA) of Baaj and Mahmassani, where its original expansion of routes by inserting individual vertices is replaced by a strategy of insertion of pairs of vertices. The algorithm proposed, called Pair Insertion Algorithm (PIA) can be used to generate initial solutions for a local improvement or evolutionary algorithm, as well as to complete an unfeasible solution with respect to demand covering constraints. Numerical results comparing PIA with RGA over a real test case show that both algorithms produce solutions with similar quality from the users viewpoint (in terms of in-vehicle travel time), while the former produces better solutions from the operators viewpoint (in terms of number of routes and total route duration) and requires a higher execution time. Since the TNDP arises in a context of strategic planning, a solution that reduces the operation cost of the system is highly desirable, even though it takes more time to be computed. The experimental study of the proposed algorithm also shows its ability to produce diverse solutions in both decision and objective spaces; this is a useful property when looking at the use of PIA as a subroutine in the context of another algorithm such as metaheuristics, in particular for a multi-objective problem like TNDP.     

Optimization models for operative planning in drinking water networks

The topic of this paper is minimum cost operative planning of pressurized water supply networks over a finite horizon and under reliable demand forecast. Since this is a very hard problem, it is desirable to employ sophisticated mathematical algorithms, which in turn calls for carefully designed models with suitable properties. The paper develops a nonlinear mixed integer model and a nonlinear programming model with favorable properties for gradient-based optimization methods, based on smooth component models for the network elements. In combination with further nonlinear programming techniques (Burgschweiger et al. in ZIB Report ZR-05-31, Zuse Institute Berlin, 2005), practically satisfactory near-optimum solutions even for large networks can be generated in acceptable time using standard optimization software on a PC workstation. Such an optimization system is in operation at Berliner Wasserbetriebe.     

An optimal power flow plus transmission costs solution

This paper is aimed at the solution of the optimal power flow (OPF) problem with embedded security constraints (OPF-SC) by the particle swarm optimizer. The major objective is to minimize the overall operating cost while satisfying the power flow equations, system security, and equipment operating limits. The overall operating cost is composed by the generation cost, transmission cost, and the consumer benefit. A modification of the conventional particle swarm optimizer (PSO) has been used as the optimization tool, which uses reconstruction operators and dynamic penalization for handling constraints. The reconstruction operators allow the increase of the number of particles within the feasible region. The power equations mismatch, loss active power transmission, and voltages are calculated by the Newton–Raphson method. To demonstrate its robustness, the proposed algorithm was tested on systems from the open literature. Several cases have been studied to test and validate the proposed approach.     

电阻电路的位函数及其应用

本文用简明的方法推导了直流线性和非线性电阻电路的位函数,对于含压控型电阻和流控型电阻的混合电路,引入了混合容度的概念,最后讨论了位函数的两个新应用:估计输入电阻、非线性规划的电路模拟。     

近红外光谱分析技术在蛋鸡配合饲料质量监测上的应用

本文采用常用饲料原料参照通用配方,按蛋白、水分、脂肪、纤维的梯度分布配制成58个蛋鸡配合饲料样品。用该配制样品的化学成分计算值建立近红外反射光谱(NIRS)定标方程。并用从哈市饲料研究所试验厂采集的30个原料相同、配方近似的蛋鸡配合饲料样品检验上述定标方程。蛋鸡配合饲料的七项指标的NIRS测定值均达到了与常规化学方法分析值(ME为计算值)相接近的水平。证明了将NIRS技术应用于饲料工厂配合饲料生产线上的产品质量监测是快速可靠的。     

汽车拖拉机差速器优化设计

以最小空间回转体积为优化目标,建立汽车拖拉机差速器优化设计数学模型,约束条件全面考虑了边界、性能、安装及结构工艺诸方面的因素,优化方法采用混合离散变量法。给出直齿圆锥齿轮角变位系数的计算公式与设计实例。     

均粒混合滤料过滤技术的研究

提出了均匀粒径的陶粒和均匀粒径的无烟煤滤料，组成均粒混合滤料滤床，形成一种反粒度过滤，使整个滤床的截污作用都得到了充分发挥。     

矿井机车运输最优化探讨

本文建立了矿井机车运输优化问题的多目标整数线性规划数学模型；揭示了一种用模糊线性规划理论求解该类问题的方法；并进行了实例分析。     

燃速仪燃烧室内气流速度的流量修正计算法

对带视窗的燃烧室来说,固体推进剂燃烧产生的烟经常影响观察和测量,采用流动氮气可以消除烟的影响,但流动氮气流又会对固体推进剂燃烧发生影响,因而正确确定固体推进剂药条附近的气流速度对这种实验装置很重要.本文提出了一种较简单、实用的燃烧室内气流速度的计算方法,并以激光燃速仪的燃烧室为例,计算了排烟口和排气口的气流速度,计算结果与激光多普勒测速仪测量结果一致.     

混合电解质溶液热力学——从渗透系数计算溶质活度系数的新型公式和计算方法

从热力学基本关系式出发,应用变量替换,导出从混合电解质溶液的渗透系数计算溶质活度系数的通用热力学方程。分别讨论了在以离子强度I和组分离子强度分数y为变量,或以总离子浓度m和组分离子浓度分数y为变量时方程的各种实用形式。以m和y为变量的方程与C. Pan的方程相同,但不需要两电解质具有相同电价形式的限制。从电解质溶液的理论分析导出渗透系数φ的合适的函数式,使φ的曲面拟合能在较大的浓度区间上进行且有较高的精度。将拟合的φ曲面函数式代入本文的方程能非常简单地求出溶质的活度系数,解决了I=0端点的广义积分问题。四个体系的计算结果与Pitzer方程的结果吻合,本文的公式和计算方法还适用于溶质为非挥发性的非电解质体系。