制造商主导的供应链产品绿色度与定价协调

针对需求信息不对称下制造商主导型供应链中产品绿色度与定价协调决策问题,分析了产品绿色度与产品销售价格、批发价格及市场需求间的关系,运用收益共享契约原理,建立了以收益共享系数为变量的零售商产品销售价格函数和利润函数以及制造商产品绿色度函数、批发价格函数和利润函数,运用不对称Nash协商原理,进一步构建了在制造商谈判能力给定条件下的收益共享系数优化模型,并通过数值仿真分析验证了需求信息不对称下供应链产品绿色度与定价协调优化结果.研究表明:供应链产品绿色度和定价协调优化不仅有助于制造商和零售商实现共赢,而且有助于制造商为客户提供更好的绿色产品.制造商的谈判能力越强,产品最优绿色度越高,而最优收益共享系数和产品的批发/销售价格则越小.此外,客户对产品绿色度的敏感系数与制造商谈判能力系数的共同升高将会加快最优收益共享系数的降低.研究结论可为制造商产品绿色度和绿色供应链协调决策提供有益的参考.     

变序结构局部弱非控点的二阶刻画

引进了一种二阶切导数,借助该切导数给出了变序结构集值优化问题取得局部弱非控点的二阶最优性必要条件.在某种特殊情况下,给出了一阶最优性条件.通过修正的Dubovitskij-Miljutin切锥导出的约束规格,给出了两个集值映射之和的二阶相依切导数的关系式,进一步得到目标函数与变锥函数的二阶相依切导数分开形式的最优性必要条件.     

基于损失规避行为的最优保险投资与再保策略选择

保险公司决策者一方面通过投资来实现保险资金的保值增值,另一方面通过再保险业务来控制承保风险.保险投资市场假定是由两种资产构成:一种是无风险资产,另一种是风险资产.与已有研究不同,文章基于累积前景理论,假定保险公司决策者具有损失规避异质性的非理性行为人.保险公司的盈余过程用跳跃扩散过程来刻画,保险公司的决策目标是最大化最终财富的"S"型期望效用,借助于鞅理论将动态的最大化问题转化为静态问题,通过求解静态优化问题得到了最优投资和再保险策略的解析表达式.数值模拟分析了最优策略的动态性质.     

面向节能的单/多列车优化控制研究

主要研究了以节能为目标的单/多列车优化控制问题.对于单列车,建立了以最小化牵引耗能为目标的优化控制模型.采用了逐步修正法对模型进行求解,计算结果表明每公里牵引耗能仅为7.8 kWh.对于多列车,建立了以停车时间为决策变量,最大化再生能量利用为目标的多列车优化控制模型,并采用遗传算法进行了求解.计算结果表明,模型能够节省大约25%-30%的牵引耗能.最后对实际运行中可能出现的延误,给出相应的调整策略,并对其进行了蒙特卡罗模拟.     

一种基于在线优化的排队系统分配策略

优化医院的病床分配可以有效地提高医院的管理水平.基于层次分析法建立了一套医院病床分配的评价体系,通过模拟多服务台的排队模型计算其综合评价指数.再以每天不同疾病对床位的优先级作为决策变量,引入虚拟函数f表示决策变量到综合评价指数的映射关系,对函数通过Matlab模拟及在线优化,从而确定使综合评价指数更高的改进分配方案.最后,以某眼科医院的实际数据,验证了模型和模拟策略的有效性.     

α-阶近似锥-弧连通集值优化弱有效元的最优性条件

引进了α-阶近似锥-弧连通集值映射,举例说明了它是锥-弧连通集值映射的真推广.借助Y-切锥引进了广义Y-切上图导数,讨论了它与广义切上图导数的关系.当目标函数为α-阶近似锥-弧连通集值映射时,得到集值优化取得弱有效元的充分和必要条件.     

基于不同距离的TOPSIS油田开发方案组合优选

为了衡量TOPSIS方法中不同距离函数对油田开发最优决策方案的影响,综合考虑技术、经济和效益等指标,分别采用曼哈顿距离、欧式距离、切比雪夫距离和垂面距离来探究油田开发方案排序之间的差异性.同时,为解决这种差异,通过计算4种距离函数下方案排序对理想开发方案的隶属度,并采用加权组合决策的方法对4种优选结果进行综合决策.     

基于白化值的区间DEA建模

传统数据包络分析要求输入输出数据为精确数,然而在某些实际应用中,区间形式的数据相较于精确数更容易获得.将区间数转化为白化值,并基于传统C~2R模型提出了基于白化值的区间C~2R模型.考虑到决策单元的有效性不易通过基于白化值的区间C~2R模型来判断,因此将非阿基米德无穷小概念引入到上述模型,构建了具有非阿基米德无穷小的区间C~2R模型.此外,还给出了用于判断决策单元有效性的区间目标规划方法:分别通过G_(IC~2R)模型和WG_(IC~2R)模型判断决策单元是否为区间DEA有效与区间弱DEA有效.     

基于FLAC-3D砂岩块体超低摩擦鞭梢效应研究北大核心CSCD

随着矿山开采深度的持续增加,深部岩体力学行为呈现出新形式、新特征.广泛应用于建筑行业的鞭梢效应与深部岩体部分动力响应现象极为相似.故从结构特征出发,以砂岩块体为研究对象,工作块体(水平冲击作用块体)水平位移及加速度为参考指标,通过试验及FLAC-3D数值模拟计算的方式,探究工作块体“位置”及“尺寸”对其超低摩擦鞭梢效应影响机制.研究表明:系统产生超低摩擦鞭梢效应的难易程度与工作块体尺寸密切相关,模拟中工作块体边长为标准块体(边长100 mm立方体)边长2/5时,系统结构诱发超低摩擦鞭梢效应尤其显著;在一定范围内,工作块体所处位置距扰动源越远,超低摩擦鞭梢效应强度越大,当超过这一范围时,则会出现减小趋势,即超低摩擦鞭梢效应强度随工作块体与震源块体间距离呈先增后减关系.     

一种新的二阶次梯度及其在刻画集值优化弱有效元中的应用

引进了一种新的修正的二阶切锥,借助此切锥针对集值映射引进了一种新的二阶切导数,讨论了它的若干性质.利用此修正的二阶切导数,引进了一种新的在弱有效元意义下的二阶次梯度,并建立了它的一个存在性定理.借助此二阶次梯度给出了集值优化弱有效元的一种新刻画.     

Nonlinear dynamics of regenerative cutting processes—Comparison of two models

Understanding the nonlinear dynamics of cutting processes is essential for the improvement of machining technology. We study machine cutting processes by two different models, one has been recently introduced by Litak [Litak G. Chaotic vibrations in a regenerative cutting process. Chaos, Solitons & Fractals 2002;13:1531–5] and the other is the classic delay differential equation model. Although chaotic solutions have been found in both models, well known routes to chaos, such as period-doubling or quasi-periodic motion to chaos are not observed in either model. Careful analysis shows that the chaotic motion from the Litak’s model has sharper spectral peaks, a smaller correlation dimension and a smaller value for the largest positive Lyapunov exponent. Implications to the control of chaos in cutting processes are discussed.     

Modeling of cutting force prediction in machining high-volume SiCp/Al composites

Variations in cutting forces significantly influence the tool wear and part quality in machining high-volume SiC-particle-reinforced aluminum matrix (SiCp/Al) composites. Properties of the reinforcement SiC particles, such as size and volume fraction, contribute to the change in the cutting forces. This paper presents a cutting force model based on the geometrical and mechanical nature of the tool and workpiece, considering the effect of the SiC reinforcement particles. The cutting force is predicted as three components (F_z, F_x, and F_y) and the resultant cutting force F_τs. The cutting force was considered to generate three deformed zones: (a) shear deformed zone, (b) friction deformed zone on the chip–tool interface, (c) plow deformed zone. The effect of SiC reinforcement particles on friction deformed zone is analyzed emphatically. The friction force from friction deformed zone was obtained by calculating the sliding friction force and rolling friction force. To verify the feasibility and validity of the predicted model of cutting force, cutting experiments were performed with different combinations of cutting speed, feed rate, depth of cut, and tool nose radius. The predicted cutting force values demonstrate good agreement with the measured experimental cutting force values in most cutting conditions. The average percentages of the prediction error were 1.93%, 6.20%, and 10.48% for the F_z, F_x, and F_y components, respectively, thus proving the validity and accuracy of the predicted model of cutting forces.     

考虑生产计划的多周期切割问题优化研究

切割生产广泛存在于工业企业,是原材料加工的重要环节。已有文献主要关注单周期切割问题,但是切割计划也是生产计划的一部分,切割计划和生产计划应该协调优化,达到全局最优。本文研究考虑生产计划的多周期切割问题,目标是最小化运营成本,包括准备成本、切割成本、库存成本以及母材消耗成本。首先建立混合整数规划模型;提出动态规划启发式算法;最后对算例在多种情境下测试,分析成本因子变化对最优结果的影响。算法结果与CPLEX最优结果比较,平均误差为1.85%,表明算法是有效的。     

An integrated approach to the one-dimensional cutting stock problem in coronary stent manufacturing

This paper presents a two-stage approach for pattern generation and cutting plan determination of the one-dimensional cutting stock problem. Calculation of the total number of patterns that will be cut and generation of the cutting patterns are performed in the first stage. On the other hand, the second stage determines the cutting plan. The proposed approach makes use of two separate integer linear programming models. One of these models is employed by the first stage to generate the cutting patterns through a heuristic procedure with the objective of minimizing trim loss. The cutting patterns obtained from Stage 1 are then fed into the second stage. In this stage, another integer linear programming model is solved to form a cutting plan. The objective of this model is to minimize a generalized total cost function consisting of material inputs, number of setups, labor hours and overdue time; subject to demand requirements, material availability, regular and overtime availability, and due date constraints. The study also demonstrates an implementation of the proposed approach in a coronary stent manufacturer. The case study focuses on the cutting phase of the manufacturing process followed by manual cleaning and quality control activities. The experiments show that the proposed approach is suitable to the conditions and requirements of the company.     

Mathematical modelling of chip thickness in micro-end- milling: A Fourier modelling

This study developed a model of undeformed chip thickness in micro-end-milling for the use in estimating cutting constants based on measured cutting forces. The proposed estimation method is based upon the invertibility of the average milling force model. In this paper, chip thickness in micro-end-milling was estimated by summing the thicknesses of the conventional chip component and the additional chip component. Thickness was then expressed in terms of Fourier series. The analyses showed that the fast convergence of Fourier series gives the Fourier chip thickness model sufficient accuracy when using only five terms of the truncated Fourier series for common micro-end-milling processes. The Fourier coefficients can be expressed in terms of the ratio of feed per tooth to cutter radius for different numbers of cutter teeth. The accuracy and conciseness of the chip thickness model enables the modelling of average cutting force in a closed form, which can be applied to identify the cutting constants. Cutting force experiments verify that the model prediction agrees very well with the experimental results.     

中国海洋可持续发展的SD模型与动态模拟

发展海洋经济,走海洋可持续发展之路,是振兴我国经济的一项举足轻重战略决策.从我国海洋的实际出发,运用系统动力学理论与方法建立了海洋可持续发展仿真模型.选择技术投资比例、单位海洋产业产值排污系数以及单位海洋产业产值资源消耗系数作为控制参量,分别取用不同的数值进行模拟.得到模拟结果表明,同时加大海洋经济中技术投资比,减少排污系数和资源消耗系数,海洋经将得到持续发展.并提出适合我国海洋可持续发展的政策建议.     

Modeling multistage cutting stock problems

In multistage cutting stock problems (CSP) the cutting process is distributed over several successive stages. Every stage except the last one produces intermediate products. The list of intermediate products may be given or arbitrary. The goal is to minimize the total amount of material taken out of stock to cut finished products sufficient to meet customer demands. If the intermediate sizes are given, the column generation technique can be applied to multistage cutting problems. If the intermediate sizes are not given then another dimension is added to the problem complexity. We propose a special procedure for this case that dynamically generates both rows (intermediate sizes) and columns (patterns). We refer to this method as row-and-column generation. The method uses an auxiliary problem embedded into the frame of the revised simplex algorithm. It is a non-linear knapsack problem that can be solved efficiently. In contrast to the column generation method the developed technique cannot guarantee the optimal solution. However, the results of computational experiments are very promising and prove that the method is a valuable addition to the set of tools for modeling and solving multistage CSPs.     

Simulation and experiment on standoff distance affecting gas flow in laser cutting

A three-dimensional axial symmetrical model of laser cutting is established by adopting N–S equation and RNG k–ε onflow model in the paper, and numerical simulation is put up to analyze the flow field of shield gas in cutting slot. The investigation reveals the law about how standoff distance affects the dynamic characteristic of gas jet in cutting process, and the distribution of pressure and velocity of gas jet with different standoff distances are shown in the study. Two typical subsonic nozzles are designed for the laser cutting experiment. At the end of the paper experimental results are compared with the numerical simulation results.     

流域可持续发展系统的协调控制

流域可持续发展是以流域作为特殊区域的一种可持续发展模式,本将流域可持续发展视为一个整体,提出了“流域可持续发展系统”的研究框架,讨论了流域可持续发展系统协调控制的指导原则和协调控制的主要内容,详细研究分析了流域可持续发展系统在技术层次上协调控制的技术路线。     

Cutting Angle Method and a Local Search

The paper deals with combinations of the cutting angle method in global optimization and a local search. We propose to use special transformed objective functions for each intermediate use of the cutting angle method. We report results of numerical experiments which demonstrate that the proposed approach is very beneficial in the search for a global minimum.