A STOCHASTIC DYNAMIC PROGRAMMING MODEL FOR THE OPTIMUM OPERATION OF A MULTI-PURPOSE RESERVOIR1

ABSTRACT: The main objective of this paper is to present a stockastic dynamic programming model useful in determining the optimal operating policy of a single multipurpose surface reservoir. It is the unreliability of forecasting the amount of future streamflow which makes the problem of a reservoir operation a stochastic process. In this paper the stochastic nature of the streamflow is taken into account by considering the correlation between the streamflows of each pair of consecutive time intervals. This interdependence is used to calculate the probability of transition from a given state and stage to its succeeding ones. A dynamic programming model with a physical equation and a stochastic recursive equation is developed to find the optimum operational policy. For illustrative purposes, the model is applied to a real surface water reservoir system.     

A cross-validation of safety climate scale using confirmatory factor analytic approach

PROBLEM: Given the lack of a consistent factor structure of safety climate, this study tested the stability of a factor structure of a safety climate scale developed through an extensive literature review using confirmatory factor analytic approach and cross-validation. METHODS: A cross-sectional sample of 722 U.S. grain industry workers participated in the questionnaire survey. RESULTS: The safety climate scale developed through the generation of an item pool based on a table of specifications, subsequent scientific item reduction procedures, reviews from experts, and pilot test yielded adequate reliabilities for each dimension. Each item showed proper discriminative power based on both internal and external criteria. Criterion validity was manifested by the significant positive correlation of the scale with five criteria. Evidence of construct validity was provided by both exploratory and confirmatory factor analyses. Both calibration and validation samples supported a consistent factor structure. Management commitment and supervisor support were found to influence other dimensions of safety climate. DISCUSSION: This study provides an insight into the primary reason why previous attempts have failed to find a consistent factor structure of safety climate: No specification of the influence of management commitment and supervisor support on other dimensions of safety in their models. IMPACT ON INDUSTRY: The findings of this study provide a framework upon which accident prevention efforts can be effectively organized and underscore the importance of management commitment and supervisor support as they affect employee safety perceptions.     

Safety beliefs and safe behavior among midwestern college students

PROBLEM: This study investigated the impact of safety beliefs on safe behavior and the effect of age, gender, class standing, and geographic region on these beliefs and behaviors. It also compares the level of safety beliefs and safe behavior of Midwestern college students in 1993 to those in 2002. METHOD: A total of 1,059 undergraduate students at four Midwestern universities completed the 33-item questionnaire developed by Crowe (J. Saf. Res. 26 (1995) 187) during the spring semester of 2002. RESULTS: Significant main effects for gender and age on safety beliefs and safe behavior were found as well as a significant interaction between gender and age for both outcome variables. The regression model with the independent variables of personal responsibility and gender yielded a multiple R of.58, which explained 34% of the variance of the self-reported safe behavior. Midwestern college students in 2002 were found less safety-conscious in terms of self-reported safety beliefs and safe behavior than those in 1993. DISCUSSION: The findings indicate that safety education of adolescents and young adults in the United States has not been effective, at least for the last decade, or today's social and school environment is less conducive to the students' safe behavior and beliefs than a decade ago. IMPACT ON INDUSTRY: Proactive multidisciplinary approaches to enhance safe behavior and beliefs of young adults should be made based on critical evaluation of current approaches.     

AN INTEGRATED APPROACH TO WATER RESOURCES DEVELOPMENT OF THE TEHRAN REGION IN IRAN1

ABSTRACT: In this paper, a system approach to water resources development in Tehran Metropolitan Area, with its complex system of water supply and demands, is discussed. Water resources in this region include water storage in the Lar, Latyan, and Karaj reservoirs, the Tehran aquifer, as well as water discharge in local rivers and in drainage channels (mainly supplied by urban runoff and wastewater). This study consists of three phases of long‐term water resources planning and management in the Tehran metropolitan area. In each phase, a different level of details among different components of the system is considered. In the first phase, optimal operating policies for Tehran reservoirs and a decision support system are developed. In the second phase, interactions between surface and ground water resources as well as surface runoffs and wastewater disposal in different subareas are investigated. The water table fluctuations as a result of implementing sewerage collection project was also simulated. In the last phase, long‐term scenarios for water resources and agricultural development in the Southern part of Tehran are defined, and the effects of each scenario on the quality and quantity of surface and ground water resources are studied.     

An ontology-based framework for process monitoring and maintenance in petroleum plant

In production plants, monitoring and maintaining industrial processes and emergency shutdowns are not straightforward tasks due to the large number of events and alarms which are triggered during the plant shutdown process. It is also vitally important to provide decision support to stakeholders for efficient and effective monitoring and maintenance of production process. This paper presents a novel framework and design to enhance maintenance decisions based on the knowledge gathered through the process of monitoring. This monitoring process is based on signals which are triggered during the plant safety shutdown process. We have designed and implemented a framework using an ontology and business rules to define the logical structure and operation of the petroleum plant with the objective of monitoring the cause and effect of the petroleum plant shutdown process. To enhance maintenance decisions, we have extended the ontology and the framework to ensure that decision makers have sufficient information to make the right decision at the right time. The proposed extended framework is designed, implemented and evaluated using an example petroleum production plant as a case study.