Validation and verification of social processes within agent-based computational organization models

The use of simulation modeling in computational analysis of organizations is becoming a prominent approach in social science research. However, relying on simulations to gain intuition about social phenomena has significant implications. While simulations may give rise to interesting macro-level phenomena, and sometimes even mimic empirical data, the underlying micro and macro level processes may be far from realistic. Yet, this realism may be important to infer results that are relevant to existing theories of social systems and to policy making. Therefore, it is important to assess not only predictive capability but also explanation accuracy of formal models in terms of the degree of realism reflected by the embedded processes. This paper presents a process-centric perspective for the validation and verification (V&V) of agent-based computational organization models. Following an overview of the role of V&V within the life cycle of a simulation study, emergent issues in agent-based organization model V&V are outlined. The notion of social contract that facilitates capturing micro level processes among agents is introduced to enable reasoning about the integrity and consistency of agent-based organization designs. Social contracts are shown to enable modular compositional verification of interaction dynamics among peer agents. Two types of consistency are introduced: horizontal and vertical consistency. It is argued that such local consistency analysis is necessary, but insufficient to validate emergent macro processes within multi-agent organizations. As such, new formal validation metrics are introduced to substantiate the operational validity of emergent macro-level behavior. Levent Yilmaz is Assistant Professor of Computer Science and Engineering in the College of Engineering at Auburn University and co-founder of the Auburn Modeling and Simulation Laboratory of the M&SNet. Dr. Yilmaz received his Ph.D. and M.S. degrees from Virginia Polytechnic Institute and State University (Virginia Tech). His research interests are on advancing the theory and methodology of simulation modeling, agent-directed simulation (to explore dynamics of socio-technical systems, organizations, and human/team behavior), and education in simulation modeling. Dr. Yilmaz is a member of ACM, IEEE Computer Society, Society for Computer Simulation International, and Upsilon Pi Epsilon. URL: http://www.eng.auburn.edu/~yilmaz     

Dose prediction and process optimization in a gamma sterilization facility using 3-D Monte Carlo code

A model of a gamma sterilizer was built using the ITS/ACCEPT Monte Carlo code and verified through dosimetry. Individual dosimetry measurements in homogeneous material were pooled to represent larger bodies that could be simulated in a reasonable time. With the assumptions and simplifications described, dose predictions were within 2–5% of dosimetry. The model was used to simulate product movement through the sterilizer and to predict information useful for process optimization and facility design.     

The European Eco-Management and Audit Scheme Accreditation – an overview

 Environmental quality is still deteriorating in the EU and worldwide despite all the Directives and Regulations in this field over the past 20 years. The European Community has devised a new approach to this problem with the introduction of the Eco-Management and Audit Scheme Regulation. This Regulation provides industry with an opportunity to demonstrate that it can achieve continuous improvement in its environmental performance through a voluntary scheme which is not based on the traditional command and control mechanisms of Directives. This paper gives an overview of the steps involved in implementing the European Eco-Management and Audit Scheme and the role of accreditation in supporting the scheme.     

直接解调方法在嫦娥一号卫星X射线谱仪地面验证实验数据分析中的应用

"嫦娥一号"卫星是我国的第一颗月球探测卫星,运行轨道高度为200 km,预计工作寿命为一年,其上配备的X射线成像谱仪具备了对月表进行X射线探测、成像和对太阳X射线进行监测的功能.该X射线谱仪由两个全同的探测器阵列组成,其中,为了实现对月表主要化学元素分布及其含量进行探测的科学目标,在每个探测器阵列还配备了2个低能探测器单元.这4路低能探测器单元的面积为25 mm2,采用的都是厚度为500 μm,具有优良探测性能的Si-PIN探测器,其探测能区为1～10 keV,能量分辨率为～5%@5.9 kev.文章主要介绍了嫦娥一号卫星X射线谱仪的地面验证实验,并且根据X射线谱仪的能量响应矩阵,利用直接解调方法和基本参数法对X射线谱仪地面验证实验中的探测数据,特别是对盲测样品中的Mg,Al,Si等元素进行了定性和定量分析.     

Asset portfolio securitizations and cyclicality of regulatory capital

This paper analyzes the level and cyclicality of regulatory bank capital for asset portfolio securitizations in relation to the cyclicality of capital requirements for the underlying loan portfolio as under Basel II/III. We find that the cyclicality of capital requirements is higher for (i) asset portfolio securitizations relative to primary loan portfolios, (ii) Ratings Based Approach (RBA) relative to the Supervisory Formula Approach, (iii) given the RBA for a point-in-time rating methodology relative to a rate-and-forget rating methodology, and (iv) under the passive reinvestment rule relative to alternative rules. Capital requirements of the individual tranches reveal that the volatility of aggregated capital charges for the securitized portfolio is triggered by the most senior tranches. This is due to the fact that senior tranches are more sensitive to the macroeconomy. An empirical analysis provides evidence that current credit ratings are time-constant and that economic losses for securitizations have exceeded the required capital in the recent financial crisis.     

ZSM-5分子筛酸位分布及其甲醇制烯烃催化性能的定向管理与调控

ZSM-5分子筛在甲醇制烯烃(MTO)过程中的催化性能和反应机理与其孔道中酸位点分布位置紧密相关. 本文证明在水热合成过程中加入适量的钠离子(Na⁺)可以增加ZSM-5分子筛交叉腔酸位点比例; 从而促进高级甲基苯的生成并加速芳烃循环, 有利于乙烯生成. 相反, 在合成过程中不添加钠离子, 所制备的ZSM-5分子筛直孔道和正弦孔道酸位点比例明显提高, 有利于促进烯烃循环并提高丙烯和C₃₊烯烃选择性.     

Hes1调控 AKT-MDM2-p53-PTEN通路的一种物理机制

基于Hill动力学与Michaelis-Menten方程,建立理论模型研究发状分裂相关增强子1(hairy and enhancer of split 1,Hes1)调控蛋白激酶B (Protein Kinase B,AKT)-鼠双微体2 (Murine Double Minute2,MDM2)-抗癌基因p53(p53)-第10号染色体缺失的磷酸酶及张力蛋白同源的基因(Phosphatase and tensin homolog deleted on chromosome ten,PTEN)通路的一种物理机制.研究发现,Hes1通过与PTEN结合抑制PTEN表达,并调控AKT信号.表明了Hes1蛋白的合成,以及Hes1与PTEN相互作用调控AKTMDM2-p53-PTEN通路信号,将会有效地控制细胞结果 . Hes1作为AKT-MDM2-p53-PTEN信号通路中上游调节的重要因素,还可以在一定程度上通过影响p53蛋白功能,改变p53对肿瘤的抑制性.理论结果可用于预测Notch通路信号异常诱导的致癌性,并进一步揭示了Notch信号通路影响细胞AKT-MDM2-p53-PTEN通路的激活...     

Combined implementing the hole-drilling method and reflection hologram interferometry for residual stresses determination in cylindrical shells and tubes

Main features inherent in simplified approach to residual stresses determination in cylindrical shells and tubes, external diameter of which is not less than 60 mm, by combing the hole-drilling method and reflection hologram interferometry are discussed in detail. Initial experimental information in a form of hole diameter increments in principal stress directions is derived from high-quality reflection holograms recorded near cylindrical objects of intermediate curvature value. Converting measured parameters into required stress values is based on the transition model that corresponds to plane stress conditions of pure membrane type. The technique developed is capable of determining residual stress component values within 5% accuracy in an absence of stress gradients over the probe hole diameter when a type of residual stress field corresponds to the transition model adopted. The accuracy analysis involved is based on matrix formulation of conventionally direct problem and an assumption on a pure membrane character of residual stress field under study for thin-walled shell. Required error estimations in a case of inspecting thick-walled cylindrical tube are obtained by combining the above-mentioned approach and an analogy of reconstructed fringe patterns with actual and artificial interferograms, which follow from drilling blind hole of the same geometrical parameters in thick-walled plates. Experimental verification of the developed approach is founded upon a determination of actual stresses in thin-walled cylindrical shell and obtaining residual stress distributions at the proximity of welded joint in thick-walled cylindrical tube.