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Processes that utilize multistage compression systems (olefins plant compression systems, gas processing, integrated refrigeration systems, etc.) have the potential for overpressure due to single or multiple check-valve failure. Catastrophic equipment failure resulting from overpressure can potentially occur due to compression system discharge, interstage, and/or suction check-valve failure, coincident with compressor shutdown. Depending on system design and application, overpressure values approaching or exceeding 300% of equipment design are possible, while for some equipment, even limited overpressure can result in catastrophic vessel failure due to brittle fracture. Additional hazards associated with compression system fail-to-check scenarios include risks associated with excessive flare loading and compressor rotor reverse rotation. In the case of an ethylene refrigeration compressor at a typical ethylene plant, rotor reverse rotation can potentially exceed overspeed limits.This paper provides risk assessment results based on analyses performed on the three primary compression systems in six ethylene plants. The methodologies used for risk identification screening, detailed risk assessment and evaluation of system dynamics are all presented. Alternative methods for mitigating risks are also discussed, along with check-valve reliability data. An overview of applicable overpressure protection requirements defined in the ASME Boiler and Pressure Vessel Code is provided. This paper will be of interest to anyone who designs or operates multistage compression systems in the chemical, petrochemical or refining industries. 相似文献
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In mark-recapture studies, various techniques can be used to uniquely identify individual animals, such as ringing, tagging
or photo-identification using natural markings. In some long-term studies more than one type of marking procedure may be implemented
during the study period. In these circumstances, ignoring the different mark types can produce biased survival estimates since
the assumption that the different mark types are equally catchable (homogeneous capture probability across mark types) may
be incorrect. We implement an integrated approach where we simultaneously analyse data obtained using three different marking
techniques, assuming that animals can be cross-classified across the different mark types. We discriminate between competing
models using the AIC statistic. This technique also allows us to estimate both relative mark-loss probabilities and relative
recapture efficiency rates for the different marking methods. We initially perform a simulation study to explore the different
biases that can be introduced if we assume a homogeneous recapture probability over mark type, before applying the method
to a real dataset. We make use of data obtained from an intensive long-term observational study of UK female grey seals (Halichoerus grypus) at a single breeding colony, where three different methods are used to identify individuals within a single study: branding,
tagging and photo-identification based on seal coat pattern or pelage. 相似文献
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Hamed Haddadi Andrew J. King Alison P. Wills Damien Fay John Lowe A. Jennifer Morton Stephen Hailes Alan M. Wilson 《Behavioral ecology and sociobiology》2011,65(8):1659-1668
Social Network Analysis has become an important methodological tool for advancing our understanding of human and animal group
behaviour. However, researchers tend to rely on arbitrary distance and time measures when defining ‘contacts’ or ‘associations’
between individuals based on preliminary observation. Otherwise, criteria are chosen on the basis of the communication range
of sensor devices (e.g. bluetooth communication ranges) or the sampling frequencies of collection devices (e.g. Global Positioning
System devices). Thus, researchers lack an established protocol for determining both relevant association distances and minimum
sampling rates required to accurately represent the network structure under investigation. In this paper, we demonstrate how
researchers can use experimental and statistical methods to establish spatial and temporal association patterns and thus correctly
characterise social networks in both time and space. To do this, we first perform a mixing experiment with Merino sheep (Ovis aries) and use a community detection algorithm that allows us to identify the spatial and temporal distance at which we can best
identify clusters of previously familiar sheep. This turns out to be within 2–3 m of each other for at least 3 min. We then
calculate the network graph entropy rate—a measure of ease of spreading of information (e.g. a disease) in a network—to determine
the minimum sampling rate required to capture the variability observed in our sheep networks during distinct activity phases.
Our results indicate the need for sampling intervals of less than a minute apart. The tools that we employ are versatile and
could be applied to a wide range of species and social network datasets, thus allowing an increase in both the accuracy and
efficiency of data collection when exploring spatial association patterns in gregarious species. 相似文献
96.
Deep-water shrimps, distributed on the steep outer reef slopes of tropical Pacific Islands, were obtained by setting baited traps in depths down to 850 m in the vicinity of Laucala Bay, Fiji, over the period 1979 to 1983. Life-history variables were estimated and interspecific comparisons made between Parapandalus serratifrons, Plesionika longirostris, Heterocarpus ensifer, H. gibbosus, H. sibogae, H. laevigatus (Pandalidae) and Saron marmoratus (Hippolytidae) which have different depth distributions. Results suggested that, interspecifically, reproductive lifespan tended to increase with increasing depth of distribution and that mean egg sizes of each species increased with increasing depth. Brood sizes tended to increase inconsistently with depth, although relative brood size (number of eggs per “standar” 15 g individual) appeared unrelated to depth. Although annual reproductive effort varied inconsistently with depth, reproductive effort totalled over the lifespan of the Heterocarpus species tended to increase with increasing depth. Some of the findings are counter to competition-based ecological theory, and it is proposed that adult predation decreases with increasing depth, allowing deeper-water species to have an extended lifespan, an increased degree of iteroparity, and a corresponding increase in lifetime reproductive effort. Further, we suggest that the probabilities of larval survival, which appear to decrease with increasing depth, are offset by the production of larger eggs by deeper-water species. 相似文献
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Philip G. King Aaron R. McGregor Justin D. Whittet 《Journal of Environmental Planning and Management》2016,59(1):98-119
This paper examines five representative sites on the California coast to illustrate a cost-effective methodology using tools and data that local decision makers can apply to analyse the economics of sea level rise (SLR) adaptation. We estimate the costs/benefits of selected responses (e.g. no action, nourishment, seawalls) to future flooding and erosion risks exacerbated by SLR. We estimate the economic value of changes to public/private property, recreational and habitat value, and beach related spending/tax revenues. Our findings indicate that the costs of SLR are significant but uneven across communities, and there is no single best strategy for adaptation. For example, Los Angeles's Venice Beach could lose $450 million in tourism revenue by 2100 with a 1.4 m SLR scenario while San Francisco's Ocean Beach would lose $80 million, but the impacts to structures could total nearly $560 million at Ocean Beach compared to $50 million at Venice Beach. 相似文献
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