Combining HAZOP with dynamic simulation—Applications for safety education

A quantitative variation of the hazard and operability analysis (HAZOP) procedure is demonstrated. The process is divided into sections and dynamic models of the separate sections are prepared. Those models are used in the framework of the HAZOP procedure to determine the magnitude of the deviations from normal operation conditions that may lead to serious accidents and to test design modification to improve the safety characteristic of the process. A process involving an exothermic reaction conducted in a semi-batch reactor is used to demonstrate the advantages of the proposed procedure and its application for safety education and operator training. The programs used for simulating the reactor are available at: ftp://ftp.bgu.ac.il/shacham/OctanoneProd/.

It is shown that the use of those programs can enhance considerably the safety education by providing tools for systematic screening of process deviation associated with possible hazardous events, determining the threshold values that may lead to such events and enabling the examination of a particular design for the adequate safe range of operation.     

Business strategy,work processes and human resource training: are they congruent?

This study examines the extent to which human resource (HR) training (content and context) is contingent on business strategy (i.e. classified according to Miles and Snow (1984) typology—‘Designing strategic human resource systems’, Organizational Dynamics, 13 , 36–52) as well as the characteristics of the work process. Sixty‐five Spanish organizations (i.e. 65 senior executives and 65 senior HR officers) participated in the study. Using primarily factorial and cluster analyses, support was found to the assertion that companies adopting a particular type of training strategy/policy have a high degree of internal consistency amongst the training objectives sought. In terms of work processes and training, results indicate that under work processes where the content of work provides for enrichment and for long‐term results, companies tend to adopt training strategies where emphasis is on enhancement of individual specialized skills aimed at improving direct productivity. By contrast, firms who use work processes that are characterized by repetitive and routine tasks, de‐emphasize this type of training content. Results also indicae that limited level of contingencies exist between training policies and business strategy, especially when time dimension is also accounted for. While the theory suggests that organizations that have their HR training fit (contingent) on their business strategy are more effective, the empirical results portrayed in this study shows a more complex picture. Copyright © 2000 John Wiley & Sons, Ltd.     

A Kinetic Study of Aerobic Propane Uptake and Cometabolic Degradation of Chloroform, cis-Dichloroethylene and Trichloroetylene in Microcosms with Groundwater/Aquifer Solids

The focus of this study was to compare the behavior of different consortiums of aerobic propane-utilizing microorganisms, with respect to both the lag time for growth after exposure to propane, and their ability to transform three chlorinated aliphatic hydrocarbons (CAHs): chloroform (CF), cis-dichloroethylene (c-DCE) and trichloroethylene (TCE). Thirty-three slurry microcosms, representing seven combinations of aquifer solids and groundwater were constructed for this study. The lag time required for establishing propane-utilizing consortiums ranged between 24 and 29 days in 6 of the 7 combinations. Kinetic tests were performed with respect to propane utilization and CAH transformation. After CAH exposure, the ability of the microorganisms to metabolize propane was significantly reduced. CF and TCE were transformed more slowly than c-DCE, the average values of the initial transformation rates being equal to 0.10 ± 0.04, 0.09 ± 0.05 and 0.98 ± 0.18 mol/(L h),respectively. CF caused the greatest reduction in propane uptake rates, whereas c-DCE exhibited an apparently reversible negative effect on propane uptake rates. The estimates of the Monod half-saturation constants relative to CF, TCE and c-DCE resulted in the 2–3 mol/L range, but were characterized by a high degree of uncertainty.     

Vegetation changes along the United States east coast following the great storm of march 1962

Regional-scale vegetation changes on Assateague Island following overwash from the Ash Wednesday Storm of 1962 were investigated using historical aerial photography. Grasses and dunes were more abundant in 1974 in areas that were overwashed, whereas areas that were not overwashed have been more extensively colonized by shrubs. The increase in shrubs on Assateague Island is attributed to the absence of a subsequent storm overwash.     

Portfolio-Based Electricity Generation Planning: Policy Implications For Renewables And Energy Security

Renewable generating technologies offer an effective means for climate change mitigation. Policy makers, however, are wary because of the widespread perception that these technologies cost more than conventional alternatives so that increasing their deployment will raise overall electricity generating costs. Energy planning represents an investment-decision problem. Investors commonly evaluate such problems using portfolio theory to manage risk and maximize portfolio performance under a variety of unpredictable economic outcomes. Energy planners need to similarly abandon their reliance on traditional, “least-cost” stand-alone kWh generating cost measures and instead evaluate conventional and renewable energy sources on the basis of their portfolio cost – their cost contribution relative to their risk contribution to a mix of generating assets. Energy security generally focuses on the threat of abrupt supply disruptions. This paper suggests a more profound aspect: mitigating fossil price volatility. An extensive body of research indicates that fossil volatility significantly disrupts the economies of consuming nations, potentially exacting hundreds of billions of dollars from the US and EU economies alone. Energy security is reduced when countries hold inefficient portfolios that are needlessly exposed to fossil price risks. This paper describes essential portfolio-theory ideas and uses three case studies to illustrate how electricity-generating mixes can benefit from additional shares of wind, geothermal and other renewables. Compared to existing, fossil-dominated mixes, efficient portfolios reduce generating cost while including greater renewables shares in the mix thereby enhancing energy security. Though counter-intuitive, the idea that adding more costly renewables can actually reduce portfolio-generating cost is consistent with basic finance theory. An important implication is that in dynamic and uncertain environments, the relative value of generating technologies must be determined not by evaluating alternative resources, but by evaluating alternative resource portfolios.     

Maternal characteristics and the production and recruitment of sons in the eastern kingbird (<Emphasis Type="BoldItalic">Tyrannus tyrannus</Emphasis>)

Sex allocation theory predicts that if variance in reproductive success differs between the sexes, females who are able to produce high-quality young should bias offspring sex ratio towards the sex with the higher potential reproductive success. We tested the hypothesis that high-quality (i.e., heavy) female eastern kingbirds (Tyrannus tyrannus) that bred early in the breeding season would produce male-biased clutches. A significant opportunity for sexual selection also exists in this socially monogamous but cryptically polygamous species, and we predicted that successful extra-pair (EP) sires would be associated with an excess of male offspring. Although population brood sex ratio did not differ from parity, it increased significantly with female body mass and declined with female breeding date, but was independent of the morphology and display (song) behavior (correlates of reproductive success) of social males and EP sires. Male offspring were significantly heavier than female offspring at fledging. Moreover, the probability that male offspring were resighted in subsequent years declined with breeding date, and was greater in replacement clutches, but lower when clutch size was large. Probability of resighting female offspring varied annually, but was independent of all other variables. Given that variance in reproductive success of male kingbirds is much greater than that of females, and that male offspring are more expensive to produce and have a higher probability of recruitment if fledged early in the season, our results support predictions of sex allocation theory: high-quality (heavy) females breeding when conditions were optimal for male recruitment produced an excess of sons.     

Compound urban crises

The crises that cities face—such as climate change, pandemics, economic downturn, and racism—are tightly interlinked and cannot be addressed in isolation. This paper addresses compound urban crises as a unique type of problem, in which discrete solutions that tackle each crisis independently are insufficient. Few scholarly debates address compound urban crises and there is, to date, a lack of interdisciplinary insights to inform urban governance responses. Combining ideas from complex adaptive systems and critical urban studies, we develop a set of boundary concepts (unsettlement, unevenness, and unbounding) to understand the complexities of compound urban crises from an interdisciplinary perspective. We employ these concepts to set a research agenda on compound urban crises, highlighting multiple interconnections between urban politics and global dynamics. We conclude by suggesting how these entry points provide a theoretical anchor to develop practical insights to inform and reform urban governance.     

Physiological parameters of plants as indicators of water quality in a constructed wetland

Introduction  

Increasing demand for water has stimulated efforts to treat wastewater for reuse in agriculture. Decentralized facilities for wastewater treatment became popular as a solution to remote and small communities. These systems mimic natural wetlands, cleaning wastewater as they flow through a complex of filter media, microbial fauna, and vegetation. The function of plants in constructed wetlands (CWs) has not been fully elucidated yet.