Accommodating Uncertainty in Comparative Risk

Comparative risk projects can provide broad policy guidance but they rarely have adequate scientific foundations to support precise risk rankings. Many extant projects report rankings anyway, with limited attention to uncertainty. Stochastic uncertainty, structural uncertainty, and ignorance are types of incertitude that afflict risk comparisons. The recently completed New Jersey Comparative Risk Project was innovative in trying to acknowledge and accommodate some historically ignored uncertainties in a substantive manner. This article examines the methods used and lessons learned from the New Jersey project. Monte Carlo techniques were used to characterize stochastic uncertainty, and sensitivity analysis helped to manage structural uncertainty. A deliberative process and a sorting technique helped manage ignorance. Key findings are that stochastic rankings can be calculated but they reveal such an alarming degree of imprecision that the rankings are no longer useful, whereas sorting techniques are helpful in spite of uncertainty. A deliberative process is helpful to counter analytical overreaching.     

Antecedents or Effects of Being a Manager in the Nonprofit,Public, or Private Sector

In this correspondence I postulate a complementary consideration to an article recently published in Nonprofit Management & Leadership: “Factors Attracting Individuals to Nonprofit Management over Public and Private Sector Management” (LeRoux and Feeney 2013). The aim of this correspondence is to provide avenues for further research based on an evaluation of the authors’ analysis and their embedded assumptions on causality and interdependency of the variables used. I perform an extended empirical analysis of the same data as used in LeRoux and Feeney (2013) in which inherent assumptions are adjusted based on available literature. Results show that their conclusions need nuancing, and that further research could focus on (1) a clearer distinction between antecedents and effects of sector of employment, and (2) the different relationships across sectors between work‐related variables, such as job satisfaction, job flexibility, or job clarity.     

非支配排序遗传算法(NSGA)算子分析

介绍了一种基于遗传算法的多目标进化算法-非支配排序遗传算法(NSGA)。并用NSGA对三个多目标优化问题进行了详尽的计算,对采用不同的算子和不同的算子取值进行了对照,初步得出了一组适用于不同类型问题的NSGA的遗传算子取值,对其他同类问题的计算提供了参考。     

遥操作机器人系统基于前向观测器的状态反馈控制

针对遥操作机器人系统传输通道中存在的通讯时延 ,建立系统的状态空间表达并提出用时间前向观测器预测从手系统状态 ,用力、位置和速度反馈以消除或减小时延对系统的影响。以系统的渐近稳定性 ,主、从机械手静态跟踪误差为零为目标 ,设计反馈控制器并对控制器的设计参数进行了分析。仿真结果表明提出的方法是有效的。     

北京大学与中国民俗学的建立

五四新文化运动中风行一时的“整理国故”运动，扩大了国学研究的范围，把学术的重心由清末的经史子集扩大到民间文化与社会心理方面，推动了考古学，社会学，心理学等新学科的建设，开创了中国现代学术的新天地，作为新文化运动中心的北京大学，组织发起了全国性的歌谣征集与风俗调查活动，搜集整理了大量原始资料，在此基础上，北大的国学研究乾们结合西民俗学原理，对歌谣与民俗学之间的关系，民俗学的界定以及民俗学的研究方法等方面进行了研究和探讨，使民俗学理论与学术实践实现了有机结俣，最终使中国民俗学以一门新的学科的面貌出现于学术界，北大也因首倡之功而成为我国民俗学的发源地。     

机关枪与线装书:从"国学书目"论争看民初科学与国学之间的紧张(三)

1923年初胡适和梁启超为清华学生开具"国学书目",引发一场关于整理国故的论争.参与者基本皆新派人物,因而也可视为新派内部就此问题整合观念的努力.争论中不论支持还是反对整理国故之人都经常援引"科学"以为助,像吴稚晖、康有为这样政治、文化立场都相当不同的老辈此时均特别强调中国急需的是"科学"的物质层面,而林玉堂等几位对"国学"认知不甚相同的年轻留学生却更注重"科学"的整体性(其实是更侧重其"精神与方法"),并进而提出了"科学的国学"的口号.这些与学术相关的现象折射出超越于学术的意义,应置于近代中国思想演变的历史框架中进行考察.     

食品检测咀嚼机器人灵活性分析与运动仿真

为了解决目前食品检测中检测不准确,反馈速度慢,评价不客观等问题,设计了基于Stewart平台的咀嚼仿生机 器人;介绍了咀嚼仿生机器人的工作原理;推导了机构的雅克比矩阵;分析了机构在中位时的局部灵活性;建立了仿真咀 嚼平台的虚拟样机模型;模拟了下颌简单的张合运动。仿真结果表明驱动杆的各种物理量变化曲线与人类真实咀嚼运 动比较吻合,机构的设计合理可靠。该机构能准确、快速、客观地实现食品的检测。     

基于超声的非完整移动机器人避障控制

介绍了路径规划的发展状况,并对非完整移动机器人的模型进行了讨论.为实现非完整移动机器人的自主避障,给出了移动机器人的超声定位结构,并提出一种基于超声避障的控制策略,对不同方向上的障碍作不同的考虑,突出正前方的障碍.将避障策略应用于实验平台,结果表明,移动机器人能在布满障碍的环境中有效实现避碰.     

Optimal Acquisition and Sorting Policies for Remanufacturing

The condition of the used items acquired by remanufacturers is often highly variable, and sorting is an important aspect of remanufacturing operations. Sorting policies—the rules specifying which used products should be remanufactured and which should be scrapped—have received limited attention in the literature. In this paper, we examine the case of a remanufacturer who acquires unsorted used products as needed from third party brokers. As more used items are acquired for a given demand, the remanufacturer can be more selective when sorting. Thus, two related decisions are made: how many used items to acquire, and how selective to be during the sorting process. We derive optimal acquisition and sorting policies in the presence of used product condition variability for a remanufacturer facing both deterministic and uncertain demand. We show the existence of a single optimal acquisition and sorting policy with a simple structure and show that this policy is independent of production amount when acquisition costs are linear.