基于DEFORM微型齿轮模具入模角分析及选用

对微型齿轮模具入模角挤压成形的影响进行有限元模拟,利用DEFORM软件模拟其成形过程中的金属流动充填规律和变形中应力应变、载荷特征,揭示了其微成形过程的变形机理,选择合理入模角实验,挤出形状良好的微型齿轮。     

Pooling data for the analysis of dynamic marketing systems

Vector autoregressive (VAR) models have become popular in marketing literature for analyzing the behavior of competitive marketing systems. One drawback of these models is that the number of parameters can become very large, potentially leading to estimation problems. Pooling data for multiple cross-sectional units (stores) can partly alleviate these problems. An important issue in such models is how heterogeneity among cross-sectional units is accounted for. We investigate the performance of several pooling approaches that accommodate different levels of cross-sectional heterogeneity in a simulation study and in an empirical application. Our results show that the random coefficients modeling approach is an overall good choice when the estimated VAR model is used for out-of-sample forecasting only. When the estimated model is used to compute Impulse Response Functions, we conclude that one should select a modeling approach that matches the level of heterogeneity in the data.     

由机械与电子谈数控机床

机械和电子是一对共生体,机械是运动的基础,是运动的实施者;电子是灵魂,是运动的指挥者。二者相互配合,取长补短,相得益彰,共同为人类社会的生产服务。     

物流配送中心工作流程的建模与仿真

根据配送中心的作业特点,分析了物流配送中心基本组成和作业流程,将物流配送中心剖析为进货、存储、流通加工、分拣、出货子系统,应用赋时着色Petri网(TCPN)对配送中心系统进行建模.通过对配送中心系统进行计算机仿真,找出了该系统在作业过程中的"瓶颈",提出了资源和流程的改进措施.     

不同厚度钢板加固RC梁受力性能的数值模拟研究

钢筋混凝土梁的变形与受力性能与结构的服役环境关系密切,在严酷的自然环境中,混凝土结构常发生劣化而影响其正常使用。本文采用ABAQUS非线性数值模拟方法,开展了不同厚度钢板(Q235钢材)加固钢筋混凝土梁的应力和位移。分析结果表明在梁底粘贴钢板可显著增强混凝土梁的抵抗变形能力,而钢板厚度是影响混凝土梁变形的主要参数。;粘贴钢板所形成的复合截面能够有效降低混凝土的拉伸损伤程度,并有效限制混凝土裂缝的开展,同时也显著降低了纵向受拉钢筋的应力。     

基于Web的城市交叉口虚拟仿真实验教学系统

城市交叉口作为城市交通的瓶颈和关键性节点,是一个多因素决策的复杂系统。在实验室的仿真模拟往往需要借助大多数仿真软件进行,且仿真设备购买成本昂贵。因此,提出了一种适用于实验室教学的解决方案,通过无人机拍摄以及图像识别技术收集实验所需实验数据,使用自主研发的基于Web的城市道路交叉口虚拟仿真系统仿真城市交叉口。仿真实验结果表明,所设计的系统可满足智能城市交叉口的仿真实验的基本要求。该解决方案具有维护便捷,可移植性强,成本低廉等优点,为智能城市交叉口的教学与科研提供了强有力的支持。     

柳工856装载机电气故障模拟试验台开发

由于装载机结构庞大,电器元件隐蔽分散,不适合实物教学。我院研制开发的柳工856装载机电气故障模拟试验台结构紧凑、尺寸小,可在实验室内直接进行实验。教学效果较好,而且经济效益明显,占用实验室空间小。对国内高职院校工程机械电气课程教学有一定的示范和借鉴作用。     

Evaluating the economy embedded in the Brazilian ethanol–gasoline flex-fuel car: a Real Options approach

The introduction of the flex-fuel cars in the Brazilian market in 2003 changed considerably the consumer decision-making process. Prior to this date, it was necessary to choose the automobile type only by gasoline or by ethanol fuel; today it is possible to choose a car type with both fuel options. This flexibility generates economic advantages for his owner, but what are the financial benefits of a flex-fuel car in comparison with a car using only gasoline? Geographically, where is the owner of the benefits from this flexibility located? This article presents an empirical application of the Real Options Theory in the analysis of the flex-fuel car option for five geographic Brazilian regions: Northern, Northeastern, Central-Western, Southeastern and Southern. The regional price differences as well as the consumer preferences of these regions were met. For this purpose, historical fuel prices were considered stochastic and following a Mean Reverting Stochastic process. The prediction and option values were generated by a Monte Carlo simulation. The results indicated that the option embedded on the Brazilian flex-fuel car adds considerable value to the owner in all regions and car models considered, with the Southeastern Region receiving most benefits by the flex option.     

Simulating Price-Taking

In this article, the author presents a price-takers’ market simulation geared toward principles-level students. This simulation demonstrates that price-taking behavior is a natural result of the conditions that create perfect competition. In trials, there is a significant degree of price convergence in just three or four rounds. Students find this simulation to be a fun, educational experience that adds value to their understanding of competitive markets.     

县(市)级土地利用总体规划中耕地需求量预测方法及其应用

科学准确地预测耕地需求量,是制定县(市)级土地利用总体规划的基础.文章根据中国南方某县1996-2005年来的耕地变更调查统计数据,分别采用趋势分析法、回归分析法、指数平滑法、GM(1,1)模型法和灰色-马尔柯夫链模型的方法,对该地区耕地总量进行了模拟和预测.不同方法的预测结果表明,基于灰色-马尔柯夫链方法的预测结果更加准确可靠,更有利于土地管理决策者的经济决策行为.在当前耕地利用方式的背景下,灰色-马尔柯夫链模型可以作为县(市)级土地利用总体规划中耕地需求量预测方法的一种好选择.