Rapid dewatering and thickening of whole-tailings with ultrafine particles is one of the most important processes for the whole-tailings paste preparation. Deep-cone thickener, a kind of such process for the flocculat...Rapid dewatering and thickening of whole-tailings with ultrafine particles is one of the most important processes for the whole-tailings paste preparation. Deep-cone thickener, a kind of such process for the flocculation and settling of whole-tailings, is particularly necessary to study. However, there exist many problems in observing the flocculation and settling process of whole-tailings, as well as the particle size distribution(PSD) of whole-tailings floccules in deep-cone thickener. Population balance model(PBM) is applied to predict the PSD in deep-cone thickener, and LUO model and GHADIRI model are employed to study the aggregation and fragmentation mechanism of the whole-tailings particles, respectively. Through three-dimensional numerical simulation on the whole-tailings flocculation and settling in deep-cone thickener using computational fluid dynamics(CFD)-PBM, the distribution of density and turbulent kinetic energy in deep-cone thickener were obtained, at the same time the spatio-temporal changes of whole-tailings floccules particle size distribution are analyzed. Finally, the major flocculation position in deep-cone thickener is found and the flocculation settling rules of whole-tailings are achieved.展开更多
Trawl is a main fishing gear in Chinese fishery,capturing large fish and letting small ones at large.However,long-term use of trawl would result in changes of phenotypic traits of the fish stocks,such as smaller size-...Trawl is a main fishing gear in Chinese fishery,capturing large fish and letting small ones at large.However,long-term use of trawl would result in changes of phenotypic traits of the fish stocks,such as smaller size-at-age and earlier age-at-maturation.In this study,we simulated a fish population with size characteristics of trawl fishing and the population produces one generation of offspring and lives for one year,used trawl to exploit the simulated fish population,and captured individuals by body size.We evaluated the impact of the changes on selectivity parameters,such as selective range and the length at 50% retention.Under fishing pressure,we specified the selectivity parameters,and determined that smaller selection rates and greater length at 50% retention were associated with an increased tendency towards miniaturization.展开更多
The purpose of stock assessment is to support managers to provide intelligent decisions regarding removal from fish populations.Errors in assessment models may have devastating impacts on the population fitness and ne...The purpose of stock assessment is to support managers to provide intelligent decisions regarding removal from fish populations.Errors in assessment models may have devastating impacts on the population fitness and negative impacts on the economy of the resource users.Thus,accuracte estimations of population size,growth rates are critical for success.Evaluating and testing the behavior and performance of stock assessment models and assessing the consequences of model mis-specification and the impact of management strategies requires an operating model that accurately describe the dynamics of the target species,and can resolve spatial and seasonal changes.In addition,the most thorough evaluations of assessment models use an operating model that takes a different form than the assessment model.This paper presents an individual-based probabilistic model used to simulate the complex dynamics of populations and their associated fisheries.Various components of population dynamics are expressed as random Bernoulli trials in the model and detailed life and fishery histories of each individual are tracked over their life span.The simulation model is designed to be flexible so it can be used for different species and fisheries.It can simulate mixing among multiple stocks and link stock-recruit relationships to environmental factors.Furthermore,the model allows for flexibility in sub-models(e.g.,growth and recruitment)and model assumptions(e.g.,age-or size-dependent selectivity).This model enables the user to conduct various simulation studies,including testing the performance of assessment models under different assumptions,assessing the impacts of model mis-specification and evaluating management strategies.展开更多
基金Project(51174032)supported by the National Natural Science Foundation of ChinaProject(NCET-10-0225)supported by the Program for New Century Excellent Talents in University,ChinaProject(FRF-TP-09-001A)supported by the Fundamental Research Funds for the Central Universities,China
文摘Rapid dewatering and thickening of whole-tailings with ultrafine particles is one of the most important processes for the whole-tailings paste preparation. Deep-cone thickener, a kind of such process for the flocculation and settling of whole-tailings, is particularly necessary to study. However, there exist many problems in observing the flocculation and settling process of whole-tailings, as well as the particle size distribution(PSD) of whole-tailings floccules in deep-cone thickener. Population balance model(PBM) is applied to predict the PSD in deep-cone thickener, and LUO model and GHADIRI model are employed to study the aggregation and fragmentation mechanism of the whole-tailings particles, respectively. Through three-dimensional numerical simulation on the whole-tailings flocculation and settling in deep-cone thickener using computational fluid dynamics(CFD)-PBM, the distribution of density and turbulent kinetic energy in deep-cone thickener were obtained, at the same time the spatio-temporal changes of whole-tailings floccules particle size distribution are analyzed. Finally, the major flocculation position in deep-cone thickener is found and the flocculation settling rules of whole-tailings are achieved.
基金Supported by the Special Fund for Agro-scientific Research in the Public Interest of China(No.201203018)the National Key Technology Research and Development Program of China(No.2006BAD09A05)
文摘Trawl is a main fishing gear in Chinese fishery,capturing large fish and letting small ones at large.However,long-term use of trawl would result in changes of phenotypic traits of the fish stocks,such as smaller size-at-age and earlier age-at-maturation.In this study,we simulated a fish population with size characteristics of trawl fishing and the population produces one generation of offspring and lives for one year,used trawl to exploit the simulated fish population,and captured individuals by body size.We evaluated the impact of the changes on selectivity parameters,such as selective range and the length at 50% retention.Under fishing pressure,we specified the selectivity parameters,and determined that smaller selection rates and greater length at 50% retention were associated with an increased tendency towards miniaturization.
基金Financial support for this project was provided by Shanghai Ocean University International Center for Marine Sciences.
文摘The purpose of stock assessment is to support managers to provide intelligent decisions regarding removal from fish populations.Errors in assessment models may have devastating impacts on the population fitness and negative impacts on the economy of the resource users.Thus,accuracte estimations of population size,growth rates are critical for success.Evaluating and testing the behavior and performance of stock assessment models and assessing the consequences of model mis-specification and the impact of management strategies requires an operating model that accurately describe the dynamics of the target species,and can resolve spatial and seasonal changes.In addition,the most thorough evaluations of assessment models use an operating model that takes a different form than the assessment model.This paper presents an individual-based probabilistic model used to simulate the complex dynamics of populations and their associated fisheries.Various components of population dynamics are expressed as random Bernoulli trials in the model and detailed life and fishery histories of each individual are tracked over their life span.The simulation model is designed to be flexible so it can be used for different species and fisheries.It can simulate mixing among multiple stocks and link stock-recruit relationships to environmental factors.Furthermore,the model allows for flexibility in sub-models(e.g.,growth and recruitment)and model assumptions(e.g.,age-or size-dependent selectivity).This model enables the user to conduct various simulation studies,including testing the performance of assessment models under different assumptions,assessing the impacts of model mis-specification and evaluating management strategies.
