Defender–Attacker Games with Asymmetric Player Utilities

The presence of strategic attackers has become an important factor in the security and protection of systems, especially since the 9/11/2001 attacks, and considerable efforts have been dedicated to its study. When defending against the strategic attacker, many existing studies assume that the attacker would seek to minimize the defender's utility, which implies that the defender and attacker have symmetric utilities. However, the attacker's objective is determined by its own valuation of the system and target of the attack, which is not necessarily consistent with the defender's utility. If the attacker unexpectedly targets a different utility, then the defense strategy might no longer be optimal. In particular, the defense strategy could be inferior if the attacker's utility is not known to the defender. This study considers a situation where the defender's utility is the system survivability and the attacker's utility is the expected number of destroyed elements in the system. We investigate possible attack strategies under these two different utilities and compare (a) the conservative defense strategy when the attack utility is unknown to the defender with (b) the optimal defense strategy when the attack utility is known to the defender. We show that the conservative protection strategy is still optimal under asymmetric utilities when the contest intensity is smaller than one.     

客户集中度、市场环境与存货管理效率

客户处在供应链的下游,对企业存货的采购、生产和销售都会产生重要影响,而多变的市场环境也在无形当中影响着客户与企业之间的关系。从企业所处行业、地区产品市场和客户三个角度所带来的市场环境变化入手,采用2011—2017年我国沪深两市A股制造业上市公司的数据,实证分析客户集中度与企业存货管理效率之间的关系。研究发现:(1)客户集中度越高,企业存货管理效率越高；(2)产品市场竞争力度越强,客户集中度对企业存货管理效率的影响越大；(3)产品市场发育越好,客户集中度对企业存货管理效率的影响越大。进一步研究发现,当企业因客户生产经营原因导致需求发生较大变化时,客户集中度对企业存货管理效率的正向影响更加显著。研究结论表明,政府应当注重市场竞争力的提升和良好经营环境的建设,使得企业在维护客户关系的同时充分发挥客户集中度对企业存货管理效率的积极作用。     

英语写作初学者学习日记写作的重要性(英文)

如何有效地引导初学者学习英语写作,在英语写作教学研究领域这一直都是个备受热议的话题。本文从三个方面简要分析了日记写作在教授这类学生英语写作中的重要性,旨在为如何提升低水平学生或初学者英语写作水平提供参考。     

基于DEA方法的地区财政支出效率评价——以四川省为例

财政支出的效率高低对地区经济和社会发展有重要影响。利用数据包络分析法(DEA)对四川省21个地级市(州)的财政支出效率进行测算和评价。研究表明,四川省整体财政支出效率较低,且近年来呈现下降趋势;财政支出效率存在明显的地区性差异,经济较发达地区的财政支出效率较高,欠发达地区的财政支出效率相对较低。     

吕氏集团对汉初岭南政策的两次调整

关于吕氏集团执政期间汉朝与南越国的矛盾冲突,传统研究多集中于吕后及其称制时期,而忽视了对事件整体性的把握,即未从吕氏集团执政的全过程加以审视。事实上,吕氏集团对南越国的政策存在两次重要调整,一是吕后时期从怀柔转向对抗,二是"诸吕"时期从南征转为罢兵。吕氏集团的第一次调整只是对原有政策的过激推行,第二次调整则可能是缓和双方关系的一种尝试。但前者不顾客观现实而冒险行事,后者缺乏后续措施而加剧了危机。因此,虽然吕氏集团的两次政策调整均出于巩固政权的需要,但其冒进与盲动的行为只能导致汉朝南部藩属体系陷入空前的危机之中。     

Adaptive and repeated cumulative meta‐analyses of safety data during a new drug development process

During a new drug development process, it is desirable to timely detect potential safety signals. For this purpose, repeated meta‐analyses may be performed sequentially on accumulating safety data. Moreover, if the amount of safety data from the originally planned program is not enough to ensure adequate power to test a specific hypothesis (e.g., the noninferiority hypothesis of an event of interest), the total sample size may be increased by adding new studies to the program. Without appropriate adjustment, it is well known that the type I error rate will be inflated because of repeated analyses and sample size adjustment. In this paper, we discuss potential issues associated with adaptive and repeated cumulative meta‐analyses of safety data conducted during a drug development process. We consider both frequentist and Bayesian approaches. A new drug development example is used to demonstrate the application of the methods. Copyright © 2015 John Wiley & Sons, Ltd.     

BAN网络节点低功耗MAC协议的设计

本文针对IEEE802.15.6标准中的MAC层协议采用固定保护时间弥补时钟漂移而造成能量浪费这一问题研究并实现一种低功耗的适宜BAN网络的MAC协议。该协议依据超帧结构的模式构建了一种新的MAC帧结构模型,并结合时间补偿算法对帧结构中的保护时间进行自适应调整,最后使用OPNET14.5仿真两种MAC协议。结果表明,本文研究的基于自适应时间补偿帧结构的MAC协议相对于固定的保护时间IEEE802.15.6的MAC协议而言,降低了终端节点能耗以及延长了网络的生存周期。     

Assessing Major Accident Risks to Support Land‐Use Planning Using a Severity‐Vulnerability Combination Method: A Case Study in Dagushan Peninsula,China

Major accident risks posed by chemical hazards have raised major social concerns in today's China. Land‐use planning has been adopted by many countries as one of the essential elements for accident prevention. This article aims at proposing a method to assess major accident risks to support land‐use planning in the vicinity of chemical installations. This method is based on the definition of risk by the Accidental Risk Assessment Methodology for IndustrieS (ARAMIS) project and it is an expansion application of severity and vulnerability assessment tools. The severity and vulnerability indexes from the ARAMIS methodology are employed to assess both the severity and vulnerability levels, respectively. A risk matrix is devised to support risk ranking and compatibility checking. The method consists of four main steps and is presented in geographical information‐system‐based maps. As an illustration, the proposed method is applied in Dagushan Peninsula, China. The case study indicated that the method could not only aid risk regulations on existing land‐use planning, but also support future land‐use planning by offering alternatives or influencing the plans at the development stage, and thus further enhance the roles and influence of land‐use planning in the accident prevention activities in China.     

The Effects of Nonprofit Reputation on Charitable Giving: A Survey Experiment

A nonprofit’s reputation is a crucial intangible asset that can bring significant benefits to the organization. Using a multidimensional framework, this study tested the effects of three dimensions of nonprofit reputation—financial efficiency, media visibility, accreditation status—on charitable giving behavior. The findings of this 2 × 2 × 2 full-factorial survey experiment show that each of the reputation dimensions has a significant individual effect on giving behavior. Furthermore, financial efficiency and accreditation status have an interaction effect on giving behavior. The findings also demonstrate the cross-level interaction between financial efficiency and the real-life giving behavior of individuals and between accreditation and the real-life volunteering behavior. This study provides implications for our understanding of the components of nonprofit reputation and their impact on charitable giving.