论政府在农产品质量安全保障中的作用

随着三聚氰胺等农产品质量问题的再次出现,我国农产品质量安全问题已引起全球的广泛关注,政府在农产品质量安全监管中的职责和作为受到严峻的挑战。文章基于农产品质量安全市场失灵和政府职责的理论,就政府在农产品质量安全保障中的作用进行分析,从宏观和微观的视角,对政府在农产品质量安全保障中的主要作用进行定位。     

The business case of a network that serves both public safety and commercial subscribers

Deploying a single nationwide broadband wireless network to serve all public safety users would have great advantages over the existing fragmented public safety systems. A nationwide system could be created to serve both public safety and commercial subscribers, which would allow a provider to exploit important economies but force it to meet the more costly requirements of public safety. This paper analyzes the viability of a public-private partnership that serves public safety and commercial subscribers from a for-profit provider's perspective. A model is presented that estimates the net present value (NPV) of a wireless network by calculating costs based on the number of cell sites required and revenue based on the projected number of subscribers acquired. The model is applied to both a network that serves only commercial subscribers on 10 MHz of 700 MHz spectrum and a public-private partnership that serves commercial subscribers and public safety personnel on 20 MHz of 700 MHz spectrum. It is found that NPV is greater for the public-private partnership than for the commercial-only network for any population density, which shows that the value of 10 MHz of spectrum exceeds the cost of meeting public safety requirements. Furthermore, the paper demonstrates that NPV/cell increases with population density, so urban areas are profitable and rural areas are unprofitable. The paper demonstrates that a partnership covering 94% of the US population breaks even because the most urban 56% of population subsidizes coverage for the next 38%. If initial deployment is subsidized, a financially sustainable public-private partnership can serve much more than 94%. Additionally, it is shown that allowing urban municipalities to opt-out of the partnership can significantly increase the subsidies required.     

The implementation and structuring of divestitures: the unit's perspective

Existing literature on value creation of divestitures focuses on their antecedents, typically relating them to the parent company's financial performance. Whether and how divestitures can create value for the divested unit remains unclear. This paper presents an exploratory study based on multiple cases, to examine which factors of the implementation and structuring of a divestiture may increase the performance of a divested unit. The emergent granular framework consists of previously unreported aspects of the divesting process and provides new insights into divestitures and their outcomes. Results indicate that antecedents alone may be insufficient for understanding the outcomes of divestitures. Different combinations of understanding of the rationale for the divestiture and perceived capabilities in the divesting process affect perceptions of divestiture feasibility. Sense of opportunity emerges as the key element of the divesting process for the success of divested units. Factors that participate with sense of opportunity in determining the success of divested units are further considered in the theoretical framework. Copyright © 2010 John Wiley & Sons, Ltd.     

Sheltering network planning and management with a case in the Gulf Coast region

This paper studies sheltering network planning and operations for natural disaster preparedness and responses with a two-stage stochastic program. The preparedness phase decides the locations, capacities and resources of new Permanent Shelters. Under each disaster scenario, both evacuees and resources are distributed to shelters in the response phase. To address the computational burden, the L-shaped algorithm is applied to decompose the problem into the scenario level with linear programs. A case study for hurricanes in the Gulf Coast region of the US is conducted to demonstrate the implementation of the proposed model.     

The power of dimensional analysis in production systems design

Dimensional Analysis (DA) is a well-known methodology in physics, chemistry and other traditional engineering areas. In its simplest form, DA is used to check the meaningfulness of a set of equations (dimensional homogeneity). In the last century, the dimensional theory has been profoundly investigated: its highest achievement is the Buckingham theorem (or pi-theorem), which states that any equation modelling a physical problem can be rearranged in terms of dimensionless ratios, thus saving variables to be handled, and especially enriching the inner physical knowledge of the studied phenomenon.In this paper we investigate how DA can be applied to Operations Management (OM) topics and which benefits it can bring to researchers in this area. A literature review is performed to clarify the main operative issues regarding DA application (assumptions and limitations); then existing applications of DA to OM are explored, pointing out that few researchers have tried to apply this methodology in the OM research field.Stemming from this analysis, we applied the pi-theorem to the design of a Flexible Manufacturing System. A complex problem, requiring 13 dimensional quantities to be expressed, is first studied via simulation; then DA is applied, reducing the number of variables to 9 dimensionless ratios. The reduced problem has a suitable size to be analytically explored and a regression model is formulated which, compared with the simulation study, offers the same precision in analysing the FMS behaviour, being more compact and powerful. This application shows the potential of DA in OM research, and will hopefully draw the attention of researches to this powerful, but unfamiliar and therefore neglected, methodology.     

井下套管封井器在气藏开发的应用

根据气藏开发的风险及难点,探讨了井下套管封井器在气藏开发的应用优势,并从气藏保护、作业安全等方面,对欠平衡起下管柱作业期间,井下套管封井器在关闭前后,井筒内各压力变化、天然气运移规律进行了理论分析,并总结出相应的技术方法;列举了井下套管封井器在部分井次的应用实例,并提出了建议。     

基于现代设计方法学的平面研磨机设计

针对现有大回转半径平面研磨机整机重、效率低的问题,采用现代设计方法学为指导,给出了平面研磨机的黑箱模型和整机功能的形态学矩阵,依据形态学矩阵设计了多工位、大回转半径平面研磨机系统方案,并讨论了主要的研磨参数.     

浅析高层在建工程施工现场存在的消防安全问题及对策

针对高层在建工程施工现场中发现的火灾隐患,分析了火灾隐患的成因,并提出了高层在建工程施工现场的消防安全管理对策,为高层在建工程施工现场的消防安全管理提出了建议.     

电网规划设计覆冰观测研究需求与经济分析

电网规划设计由于缺少详尽的区域覆冰资料,给走廊方案优化和工程投资分析带来一定的困难。覆冰资料缺乏是当前电网建设质量与工期保障的一大瓶颈问题。在总结我国电网受覆冰灾害影响的基础上,介绍了覆冰资料缺乏的现状,论述了其对电网建设的重要性;深入分析了电网规划设计在技术和经济上对覆冰资料的需求状况。     

电力设计企业开展海外输电线路EPC总承包的基本策略

目前在工程项目EPC总承包中,以设计企业为龙头的总包形式居多。结合_v-fir．实践,对电力设计企业开展海外输电线路EPC总承包的基本策略进行了探讨,指出设计企业可通过投标阶段的细致工作、中标后设计方案的优化、施工图设计阶段的基础合理配置、分包招标阶段主材供应商和施工分包商的甄选以及组建强有力的项目管理团队等方式达到控制投资、安全、质量、工期和规避风险的目的。