基于运输代理制的运输企业合作关系风险分析

研究运输代理制下运输代理企业和运输企业合作风险问题,既能从实践上,明晰双方的风险分担机制,从而解决双方的利益分配问题,又能从理论上,充实运输代理制有关理论的研究。笔者从委托-代理关系角度,在分析运输代理企业和运输企业之间的合作关系特点的基础上,指出了合作中存在的风险及其产生的原因,并利用委托-代理理论建立了运输产出不确定情况下的委托代理数学模型;分析了合作中双方风险分担的条件及措施,同时讨论了与之对应的最优报酬合同和剩余索取权问题,并给出了具有现实指导意义的几个新的观点。利用信息经济学的委托-代理理论,研究运输代理与运输企业之间合作关系中的风险问题,这是方法应用上的创新。     

雅玛里克山植被类型及物种多样性的特征

采用典型样地法对雅玛里克山进行了植被调查，结果表明，该区的植物群落类型有14种；植物种类有223种植物．分属37科147属，植物生活型有9类；短命和类短命植物获得一定发育，旱生类型的植物占绝对优势，一年生植物占有一定比例等。     

新世纪WTO与外向型经济下的区际资源优化--以山东省为例

为缓解加入WTO对我国农业带来的冲击,顺利实现外向型农业经济的转变,以山东省为例,借助Mapinfo 6.5和SPSSV 10.0软件分别从宏观总量和微观效率两个层次对1999年山东省17个市(地)的农业状况进行了差异分析,根据比较优势原理提出了区域资源区际优化的解决思路和对策,为今后我国区域农业发展提供借鉴.     

资源枯竭型城市的出路

促进资源枯竭型城市产业转移，实现城市的可持续发展是我国经济发展和城市化进程中的重要问题。资源枯竭型城市的出路在于：立足自身特点，发挥比较优势，选择和培育替代产业，以市场为出发点，实现产业结构的多元化。     

VARIABLE DISCHARGE TYPE CURVE SOLUTIONS FOR CONFINED AQUIFERS1

ABSTRACT: Almost all of the existing solutions of aquifer test analysis assume constant discharge rate boundary conditions. In many actual pumping tests, constant discharge cannot be maintained. This paper presents a general solution for an aquifer test with variable discharge. The exact solution of drawdown distribution around an infinitesimally small diameter well in a uniform, horizontal, extensive, homogeneous, and isotropic confined aquifer is presented when the discharge changes with time during the aquifer test period. A general equation for the type curves resulting from any discharge variability is given, and its application for the exponential changes is presented in detail. A simple straight line procedure is proposed for field applications by considering late time drawdown data. The consideration of constant discharge leads to overestimation of transmissivity but storativity is underestimated. Practical application of the discharge variability is illustrated by a field example.     

ACIDIFICATION AND FISH OCCURRENCE IN THE UPPER CHEAT RWER DRAINAGE,WEST VIRGINIA1

ABSTRACT: The decline of many fish populations within the mid-Appalachian region has been attributed to stream acidification as a result of acid precipitation. Many previous attempts to examine relationships between fish occurrence and acidification have been hindered by a lack of data on water quality and fish distributions. To assess relationships between water quality and bedrock type in the upper Cheat River drainage, we used EPA STORET water quality data (1969–1993) and calculated mean pH and mean alkalinity of streams associated with four bedrock types (Hampshire, Chemung, Mauch Chunk, and Pottsville). We examined the relationship between fish occurrence and bedrock type for 53 headwater streams. We found that acidity in headwater streams associated with Pottsville and Mauch Chunk groups often exceeded biological thresholds for acid-sensitive fish species (pH < 5.5). Streams associated with the Pottsville group typically had fewer cyprinid species and fewer total species than those associated with Mauch Chunk, Chemung, and Hampshire bedrock types. The congruent occurrence of streams with low buffering capacity, streams with pH > 5.5, and streams with low fish species richness indicate that acidification has influenced fish distributions in the upper Cheat River drainage.     

Analysis of driver injury severity levels at multiple locations using ordered probit models

Problem: The occurrence and outcome of traffic crashes have long been recognized as complex events involving interactions between many factors, including the roadway, driver, traffic characteristics, and the environment. This study is concerned with the outcome of the crash. Method: Driver injury severity levels are analyzed using the ordered probit modeling methodology. Models were developed for roadway sections, signalized intersections, and toll plazas in Central Florida. All models showed the significance of driver's age, gender, seat belt use, point of impact, speed, and vehicle type on the injury severity level. Other variables were found significant only in specific cases. Results: A driver's violation was significant in the case of signalized intersections. Alcohol, lighting conditions, and the existence of a horizontal curve affected the likelihood of injuries in the roadway sections' model. A variable specific to toll plazas, vehicles equipped with Electronic Toll Collection (ETC), had a positive effect on the probability of higher injury severity at toll plazas. Other variables that entered into some of the models were weather condition, area type, and some interaction factors. This study illustrates the similarities and the differences in the factors that affect injury severity between different locations.     

粤西两类混合岩地质地球化学对比及与金成矿作用关系探讨

笔者在对粤西进行金银成矿作用研究的过程中,发现该地区存在两类不同成因的混合岩类,第一类为基底混合岩,第二类为断裂变质混合岩,两者在许多方面都存在很大差异。本文从它们的形成时间、分布空间、成岩方式、岩石学、矿物学、地球化学以及与金银等元素的成矿作用关系等方面进行了研究,分别阐述了两者的各自特点,并进行了对比,研究表明,基底混合岩化作用与金银的成矿作用关系主要表现为前者为后者提供了物质基础,而断裂变质混合岩化作用与金银的成矿作用关系则主要表现为前者或其邻近的构造带对后者的空间上的控制,其次才表现为成矿作用提供物质基础。     

振动筒式压力传感器技术及其应用

振动筒式压力传感器是一种技术成熟的高精度纸对压力传感器，具有测量精度高，稳定性好，工作温度范围宽，功耗低，抗振动，耐冲击，可靠性高，频率输出以及易与计算机连接等特点，且汞柱测压设备的理想替代仪器之一，文章对振动筒式压力传感器的工作原理，产品分类和技术特点以及气象观测上的应用作了介绍。     

西藏土地资源特点及其合理开发

西藏土地辽阔，但其宜农土地少而分布集中；宜牧土地数量大，但质量差异大；宜林土地质高量大；高寒干旱及难利用土地较广。这些特点决定了西藏农林牧生产的结构、规模和布局。目前土地开发水平低、商品性生产落后，部分土地有所退化，经济与生态效益均不高。因此，今后应加强科学管理、增加投入，深度开发与保护农林牧各类土地资源。提高现有耕地的单产水平；改良草地与建设人工草地，采育结合；保护森林等乃是促进西藏农业经济发展、改善农业生产条件与生态环境的战略方针和有效对策。