基于ANSYS的激光焊接温度场数值模拟与实验研究

为了探究钢铝2种金属材料的焊接性能,以B1500HS高强钢和6016铝合金为对象,基于ANSYS平台建立钢／铝激光平板搭接焊的三维有限元模型,进行焊接过程温度场数值模拟,采用热电偶同步测温方法测得焊接热循环曲线。将实测结果与数值模拟结果对比分析,表明吻合度较好。验证了模拟计算的准确性。     

Modelling process robustness: a case study of centrifugal casting

A robust process minimises the effect of the noise factors on the performance of a product or process. The variation of the performance of a robust process can be measured through modelling and analysis of process robustness. In this paper, a comprehensive methodology for modelling and analysis of process robustness is developed considering a number of relevant tools and techniques such as multivariate regression, control charting and simulation within the broad framework of Taguchi method. The methodology as developed considers, in specific terms, process modelling using historical data pertaining to responses, inputs variables and parameters as well as simulated noise variables data, identification of the model responses at each experimental setting of the controllable variables, estimation of multivariate process capability indices and control of their variability using control charting for determining optimal settings of the process variables using design of experiment-based Taguchi Method. The methodology is applied to a centrifugal casting process that produces worm-wheels for steam power plants in view of its critical importance of maintaining consistent performance in various under controllable situations (input conditions). The results show that the process settings as determined ensure minimum in-control variability with maximum performance of the centrifugal casting process, indicating improved level of robustness.     

绿色发展对水资源-能源-粮食系统的影响

水资源-能源-粮食系统协同发展是经济社会可持续发展的重要支撑。我国生态文明建设正处于压力叠加、负重前行的关键期,资源压力大、环境容量有限和污染物排放总量高之间矛盾突出,美丽中国建设任务依然艰巨。绿色发展作为新发展理念的重要组成部分,是生态文明建设的必然要求,是建设美丽中国的必由之路,以绿色发展为抓手把准我国资源环境问题的行动脉络,为水资源-能源-粮食管理实践提供了全新思路。从绿色发展对水资源-能源-粮食系统影响的内在机理出发,结合系统的复杂性和动态性特征构建系统动力学模型,诠释了绿色发展影响下水资源-能源-粮食系统的演变过程,并对不同绿色发展引导和约束政策成效和实施力度进行了仿真模拟。研究发现：绿色发展通过引导和约束主体行为实现经济-社会-环境和水资源-能源-粮食系统相协调,在保证社会经济系统稳定运行的基础上,绿色发展引导和约束政策的调整与实施能够促进水资源-能源-粮食系统降低资源消耗和减少污染排放,政府实施的政策强度不同所取得的效果也不同。在此基础上,结合区域资源禀赋及双碳目标,未来可进一步优化绿色发展约束性政策环境,加大绿色发展政策的实施强度以促进资源高效利用和污染存量降低,充分发...     

Monte Carlo Sensitivity Analysis of Unknown Parameters in Hazardous Materials Transportation Risk Assessment

The US Department of Transportation was interested in the risks associated with transporting Hydrazine in tanks with and without relief devices. Hydrazine is both highly toxic and flammable, as well as corrosive. Consequently, there was a conflict as to whether a relief device should be used or not. Data were not available on the impact of relief devices on release probabilities or the impact of Hydrazine on the likelihood of fires and explosions. In this paper, a Monte Carlo sensitivity analysis of the unknown parameters was used to assess the risks associated with highway transport of Hydrazine. To help determine whether or not relief devices should be used, fault trees and event trees were used to model the sequences of events that could lead to adverse consequences during transport of Hydrazine. The event probabilities in the event trees were derived as functions of the parameters whose effects were not known. The impacts of these parameters on the risk of toxic exposures, fires, and explosions were analyzed through a Monte Carlo sensitivity analysis and analyzed statistically through an analysis of variance. The analysis allowed the determination of which of the unknown parameters had a significant impact on the risks. It also provided the necessary support to a critical transportation decision even though the values of several key parameters were not known.     

Reliability Analysis for Hazardous Waste Treatment Processes

The reliability of a treatment process is addressed in terms of achieving a regulatory effluent concentration standard and the design safety factors associated with the treatment process. This methodology was then applied to two aqueous hazardous waste treatment processes: packed tower aeration and activated sludge (aerobic) biological treatment. The designs achieving 95 percent reliability were compared with those designs based on conventional practice to determine their patterns of conservatism. Scoping-level treatment costs were also related to reliability levels for these treatment processes. The results indicate that the reliability levels for the physical/chemical treatment process (packed tower aeration) based on the deterministic safety factors range from 80 percent to over 99 percent, whereas those for the biological treatment process range from near 0 percent to over 99 percent, depending on the compound evaluated. Increases in reliability per unit increase in treatment costs are most pronounced at lower reliability levels (less than about 80 percent) than at the higher reliability levels (greater than 90 percent, indicating a point of diminishing returns. Additional research focused on process parameters that presently contain large uncertainties may reduce those uncertainties, with attending increases in the reliability levels of the treatment processes.     

Extensions of Fill's algorithm for perfect simulation

Fill's algorithm for perfect simulation for attractive finite state space models, unbiased for user impatience, is presented in terms of stochastic recursive sequences and extended in two ways. Repulsive discrete Markov random fields with two coding sets like the auto-Poisson distribution on a lattice with 4-neighbourhood can be treated as monotone systems if a particular partial ordering and quasi-maximal and quasi-minimal states are used. Fill's algorithm then applies directly. Combining Fill's rejection sampling with sandwiching leads to a version of the algorithm which works for general discrete conditionally specified repulsive models. Extensions to other types of models are briefly discussed.     

数字经济、空间效应与全要素生产率

当前,数字经济蓬勃发展,已成为经济增长的新动能。本文从数字产业化与产业数字化 两个维度,采用主成分分析法构建了数字经济发展水平的指标体系,并利用2004-2017年我国省际面板 数据,在克服内生性问题的基础上,实证分析了数字经济发展对全要素生产率的影响。研究发现,数字 经济发展显著促进了全要素生产率的提升。但较之高生产率地区和东部地区,数字经济发展对低生产率地区和中西部地区全要素生产率的提升作用更大。就机制而言,人力资本投资与产业结构升级是数 字经济影响全要素生产率的两个渠道。进一步的空间计量分析表明,数字经济发展不仅会提升本地区 的全要素生产率,还存在显著的空间溢出效应,有助于提升邻近地区的全要素生产率。本文的研究为评估数字经济发展的影响效果提供了数据支撑和分析视角,也为探寻全要素生产率的提升路径提供了政策参考。     

高校新型钢琴教学模式的研究——我校数码钢琴教学方法的创新与实践

针对我校传统钢琴课“一对一”教学方法存在的不足,引出了具有创新手段的数码钢琴集体课“一对多”教学方法来解决问题,对我校数码钢琴集体课的发展问题展开分析和研究,寻求一种更好的高校新型钢琴教学模式。     

仿造、生产与模拟——波德里亚对现代性历史形态的分析

波德里亚把对拟像的研究与对现代性的研究结合起来,指出现代性突破封建秩序就是从拟像秩序开始的。他集中地分析了现代社会中各种毫无意义的而又冒充各种意义的人造符号体系,他把这种人造符号体系称为＂拟像＂。仿造、生产、模拟就是与＂拟像＂相关的人类历史的三个发展阶段。     

The diffusion of the Internet: Trend and causes

Over the last two decades, the Internet has changed various facets of social life, creating many social concerns. To better assess the impact of the Internet, it is important to understand the pattern of its diffusion. Using the Current Population Survey, this paper examines the diffusion process of the Internet between 1994 and 2007. The CPS provides seven cross-sectional data sets on Internet use over the period, four of which are spaced close enough to be turned into panel data sets. Simple trend analyses show that a logistic S-curve fits the seven observations very well, and that the diffusion took off around the time when the graphical user interface was introduced. Findings from multivariate trend analyses and panel data analyses include; (1) the digital divide is not likely to be closed in the near future, (2) exposure to the technology at school and workplace are important factors of initial and continued use of the Internet, and (3) of different online activities, email use is the most important predictor of continued use, implying that the diffusion process is highly social, rather than individualistic.