数字环境下高校用户信息检索行为初探

高校用户信息行为是用户信息行为研究的一个热点,高校的信息用户群体在信息需求、信息检索和信息利用方面有其自身的规律和特点。根据网络环境的特点对此进行深入的探讨和研究。     

基于用户需求的分布式供能系统方案设计与分析

针对某医院全年冷热电负荷的变化,考虑蓄能装置及不同热源的溴化锂吸收式制冷机的影响,设计了4种分布式供能系统方案,并对各种方案进行了热经济性指标分析.提出基于用户需求设计分布式供能系统时需要考虑基本负荷、烟气补燃、蓄能设备、评价指标.     

A systems theoretic approach to second moment modelling of probabilistic engineering systems∗

A new approach to modelling probabilistic and stochastic engineering systems using graph theory is outlined. This approach emphasizes the introduction of probabilistic and stochastic concepts at the very beginning of the model building process. This is in marked contrast to past tendencies to add probabilistic concepts to the end of an otherwise deterministic model building process. The development of topological models founded on oriented probabilistic measurements is given. which leads to the identification of some useful statistical properties of the’ random interconnection equations’. The development of probabilistic component models is given, where a component can be characterized independently of other components. Methods for automatically building the second moment representation of the Mixed Nodal Tableau are discussed. The application of the above theory to the probabilistic analysis of a pipe network problem is briefly described.     

A multi-objective model for seasonal personnel reassignment

The focus of this research was the development of a model to address the problem of reassigning summer construction workers to winter snow and ice removal teams in an efficient and cost-effective manner. The model is a multi-objective integer program that can generate the complete and precise trade-off curve between the objectives of minimizing total distance that the reassigned workforce must travel from their respective homes to one of many site locations, and minimizing the maximum distance that any one worker must travel. System constraints include demand requirements for workers at each site and the limited availability of state-owned vehicles that may be issued to workers assigned to remote sites. Details of the model structure and solution procedure are presented together with the results of an actual application.     

Approximations for heterogeneous finite source queues

The exact solution for heterogeneous finite source queues involves a definition of state which is unmanageable for large customer numbers. Accordingly various approximations are considered in an attempt to obtain a simple but reasonably accurate solution. The approximations examine simplified definitions of state with a consequent reduction in the number of states and associated balance equations; one such approximation converts the heterogeneous problem to an equivalent homogeneous problem through either time or rate averaging the problem components. Applications include earthmoving, quarrying and open-cut mining operations where the plant frequently have different characteristics. The exponential solution in such cases is anticipated to provide a hower bound estimate on operation productivity, by analogy with the homogeneous case.     

Investigation of the impact of global warming on precipitation pattern of Saudi Arabia

This study has been carried out to forecast the impact of global warming on the precipitation pattern of Saudi Arabia by the end of year 2100. Simulation has been done using EdGCM model software (with available 8×10 resolution) developed at Columbia University on which there have been produced global precipitation maps for the seasonal and annual averages for the last 5 years (2096–2100). For each map, EdGCM grid values surrounding Saudi Arabia are used as input to one of the tools of Eagle point software called surface modelling (SM). SM is a new approach for downscaling global climate model results. SM software modelled out isohyets at 0.2 mm/day interval. The results indicate that the present pattern of precipitation (more in winter and less in summer) is going to change by almost equal occurrence of precipitation in all seasons for double_CO₂ (2CO₂) experiment. The 2CO₂ experiment indicates an increase of about 16.05% over the annual average precipitation across the country.     

Heterogeneous households and firms in an urban model with open space and agglomeration economies*

This paper develops a model with heterogeneous households and firms that can locate anywhere in the city. The main features of the model are household preferences for open space which depend on distance to the greenbelts at the city periphery, and agglomeration economies for firms. Numerical results show equilibrium location patterns, rents, and wages under different model specifications. Under most conditions, monocentric location patterns (where there is a higher concentration of firms in the centre zones compared to surrounding zones) are observed, but duocentric location patterns for firms can emerge if both open space values and travel costs are high.     

Application of hydraulic modelling to control intrusion into potable water pipelines

A key objective of water supply systems is to provide potable water to consumers at an appropriate quality, however, through distribution networks, water quality can be compromised. One of the avenues through which this can happen is contaminant intrusion into the network. Through hydraulic modelling, this paper examines how potential intrusion into water distribution networks can be established and also predicts the magnitude of intrusion that is expected to occur, given particular conditions. The paper further suggests possible preventive measures that can be taken in order to avert the occurrence of this phenomenon. Results indicate that for potable water pipelines flowing through high pressure areas, if the pressure of the surrounding environment can be established then by ensuring that network pressures are above the surrounding pressures in those sections of the network, intrusion can be overcome.     

Life-cycle social analysis of motorway bridges

User costs of a bridge are the costs incurred by the users of the bridge, which result from any construction and/or maintenance activity being performed in the bridge. Typically, these costs encompass the additional time lost due to incurred congestion, the additional costs of vehicle operation and the costs of additional accidents. Usually, such costs are not considered in the procedures leading to the formulation of strategies for bridge construction, maintenance and repair, despite their relevance in comparison with the costs incurred by the agency or owner of the bridge. Moreover, in a life-cycle perspective of a bridge, with a time span over 100 years, the quantification of user costs is affected by a large number of uncertainties. Therefore, it is the purpose of this paper to introduce a life-cycle analysis for the quantification of typical user costs, in a probabilistic approach. For this purpose, the analysis of a motorway bridge in Portugal is performed. The results of the case study demonstrate that user costs can be much more important than costs supported by the concessionaire, in a life-cycle perspective, and thus, a much higher importance should be given to these costs apart from the scientific community.     

Water exchange effect on eutrophication in landscape water body supplemented by treated wastewater

Artificial landscape water bodies filled by treated wastewater pose a risk of developing algal blooms due to high nutrient levels of treated wastewater. In this study, water exchange experiments were conducted using treated wastewater in an artificial landscape pond, and a eutrophication model was calibrated and applied to evaluate the effects of water exchange on algae growth in the pond. The results indicate that the joint dilution process and nutrient supply process of water exchange initially cause the algae level to rise and then rapidly decline as the hydraulic resident time (HRT) decreases, and HRT has a critical point at which the pond faces the highest risk of algal bloom. The study also indicates that phosphorus (instead of nitrogen) is the primary limiting factor of algae growth. Therefore, the critical HRT should be avoided and phosphorus is the target pollutant to be controlled in landscape pond water management.