This paper presents an application of the simulation of discrete events (SED) using ARENATM in the management of large-scale breeding farms. The main objective of the simulation model is to find a policy of replacemen...This paper presents an application of the simulation of discrete events (SED) using ARENATM in the management of large-scale breeding farms. The main objective of the simulation model is to find a policy of replacement, to ensure the best economic performance of a farm. The only variant analyzed of replacement policy was the number of cycles set in permanency for a sow in the herd. Considered incomes come from the sale of piglets and unproductive sows, and costs are due to the feeding of animals, replacement sows purchases, and the operation expenses of the farm. For this analysis, the production process was divided into three major stages called: mating, pregnancy or gestation and lactation. The sow’s movement from one stage to other was modeled by cycle-dependent transition probabilities. Considering the daily utility, as response variable, the model shows the best number of cycles to maintain the sows.展开更多
A biomimetic hip joint simulator that can be used to evaluate the outcome of the cemented total hip replacement has been designed, manufactured and evaluated. The simulator produces motion in the extension/flexion pla...A biomimetic hip joint simulator that can be used to evaluate the outcome of the cemented total hip replacement has been designed, manufactured and evaluated. The simulator produces motion in the extension/flexion plane, with a socket to rotate internal/externally. At the same time a dynamic loading cycle is applied. A validation test was performed on a cemented femoral stem within a novel composite femur. The hone quality has a strong effect on the stem migration and on the integrity of the interfaces. The migration of the stem is a combination of 3-D translation and rotation of the stem. Under the same loading conditions, weak bone allows more stem migration than strong bone. There is a great decrease in the strength of the stem-cement interface after the dynamic test, and the weak bone composite exhibited a greater reduction in interfacial strength than the strong bone composite. The decrease of the interfacial strength indicates that the primary bonding between the stem and the cement mantle had deteriorated and the integrity of stem-cement interface was damaged. The study demonstrates the value of using a hip joint simulator to investigate stem migration and interface integrity within the cemented hip replacement, suggesting that method can be used for in vitro evaluation of the biomaterials used in the cemented hip replacements.展开更多
Covalent organic framework （COF） is a porous material with low density and large BET （Brtmauer-Emmett-Teller） surface area. They have great potential in gas adsorption and separation. In this work, the adsorption ...Covalent organic framework （COF） is a porous material with low density and large BET （Brtmauer-Emmett-Teller） surface area. They have great potential in gas adsorption and separation. In this work, the adsorption of pure CO2 and CO2/CH4 mixture on modified COF-102 was simulated by using GCMC （grand canonical Monte Carlo）. Metal Li was incorporated into COF-102 through three doping methods, including charge exchange, O^--Li6＋ dipolar interaction and O^--Li^＋ chemical bonding. The influence of Li doping on the adsorption of CO2 was studied. The results showed that among the three methods, the dipole doping is the best way to improve CO2 adsorption performance. Further, the ligands of COF-102 were replaced by extended aromatic moieties, such as diphenyl and pyrene. The adsorption capacity of CO2 and CH4, and the selectivity of CO2/CH4 on the ligand-replaced COF-102 were studied. The capacity of CO2 and CH4 on the ligand-replaced COF-102 had obvious changes; hence the selectivity of CO2/CH4 can be adjusted accordingly.展开更多
To gain a competitive edge within the international and compet让ive setting of coal markets, coal producers must find new ways of reducing costs. Increasing bench drilling efficiency and performance in open-cast coal ...To gain a competitive edge within the international and compet让ive setting of coal markets, coal producers must find new ways of reducing costs. Increasing bench drilling efficiency and performance in open-cast coal mines has the potential to generate savings. Specifically, monitoring, analyzing, and optimizing the drilling operation can reduce drilling costs. For example, determining the optimal drill bit replacement time will help to achieve the desirable penetration rate. This paper presents a life data analysis of drill bits to fit a statistical distribution using failure records. These results are then used to formulate a cost minimization problem to estimate the drill bit replacement time using the evolutionary algorithm. The effect of cost on the uncertainty associated with replacement time is assessed through Monte-Carlo simulation. The relationship between the total expected replacement cost and replacement time is also presented. A case study shows that the proposed approach can be used to assist with designing a drill bit replacement schedule and minimize costs in open-cast coal mines.展开更多
It is a safe and environmentally-friendly method to exploit natural gas hydrates(“hydrate”)by using flue gas(mainly including CO_(2)and N_(2))from electric power plants.So far,however,its energy consumption and ener...It is a safe and environmentally-friendly method to exploit natural gas hydrates(“hydrate”)by using flue gas(mainly including CO_(2)and N_(2))from electric power plants.So far,however,its energy consumption and energy efficiency has not been investigated thoroughly.In this paper,the process to exploit hydrates from flue gas was established.Firstly,flue gas is injected into hydrate reservoirs after it is pressurized.The hydrates in reservoirs partially experience thermal decomposition while the rest is replaced with flue gas,so CH_(4)-CO_(2)-N_(2)mixture is formed.Secondly,the concentrated CH_(4)-CO_(2)mixture is got after N_(2)is separated and removed by using membrane component.And thirdly,the CH_(4)eCO_(2)mixture is delivered to the original electric power plant.This process was simulated by using the software Aspen Plus to analyze the production/injection ratio in the process of flue gas replacement under different injection pressures,the methane replacement ratio,and the energy consumption and energy efficiency in the whole process.It is indicated that the energy in the process of hydrate exploitation from flue gas is mainly consumed at the pressurized injection stage,and the injection pressure increase correspondingly results in the increase of energy consumption at pressurization and membrane separation stages,and to some extent improves the recovery ratio of pressure energy.Besides,when the injection pressure is 5e16 MPa,the production/injection ratio in the process of flue gas replacement is 0.03-0.26,the methane replacement ratio is 19.9-56.2%,the unit energy consumption in the whole process is 2.15-1.05(kW$h)/kgCH_(4),and the energy return on investment(EROI)is 7.2-14.7.It is concluded that the energy efficiency of hydrate exploitation from flue gas can be effectively improved by increasing the injection pressure in the range of 5e10 MPa.展开更多
The West Development Policy being implemented in China causes significant land use and land cover (LULC) changes in West China, of which the two most important types of LULC change are replacing farmland and re-greeni...The West Development Policy being implemented in China causes significant land use and land cover (LULC) changes in West China, of which the two most important types of LULC change are replacing farmland and re-greening the desertification land with forest or grass. This paper modifies the prevailing regional climate model (RCM) by updating its lower boundary conditions with the up-to-date satellite database of the Global Land Cover Characteristics Database (GLCCD) created by the United States Geological Survey and the University of Nebraska-Lincoln. The modified RCM is used to simulate the possible regional climate changes due to the LULC variations. The preliminary results can be summarized as that the two main types of LULC variation, replacing farmland and greening the desertification lands with forest or grass in west China, will affect the regional climate mostly in northwest and north China, where the surface temperature will decrease and the precipitation will increase. The regional climate adjustments in South, Southwest China and on the Tibet Plateau are uncertain.展开更多
针对命名数据网络(named data networking,NDN)中,路由节点缓存利用的不合理、无法区分内容请求频率的高低,导致路由节点缓存命中率过低的问题,提出了一种基于新鲜因子的缓存替换策略(FRESH)。FRESH策略通过在包结构中新增内容类型、跳...针对命名数据网络(named data networking,NDN)中,路由节点缓存利用的不合理、无法区分内容请求频率的高低,导致路由节点缓存命中率过低的问题,提出了一种基于新鲜因子的缓存替换策略(FRESH)。FRESH策略通过在包结构中新增内容类型、跳数、动态时间3个Tag字段,引入信息熵衡量数据类型的优先级,利用新增Tag字段构建新的替换参量——“新鲜因子”,设计新的缓存替换策略。实验结果表明,在缓存容量比为0.03、Zipf分布参数为0.8的环境下,FRESH策略与DCVRP、CPCA相比较,缓存命中率分别增长了3.5%和6%,明显的提高了缓存命中率,优化了网络中的缓存效率。展开更多
基金Instituto Tecnologico y de Estudios Superiores de Monterrey(Scholarship)Universidad Autonoma del Estado de Hidalgo,Secretaria de Educacion Publica(Complement scholarship)University of Lleida(Scholarship).
文摘This paper presents an application of the simulation of discrete events (SED) using ARENATM in the management of large-scale breeding farms. The main objective of the simulation model is to find a policy of replacement, to ensure the best economic performance of a farm. The only variant analyzed of replacement policy was the number of cycles set in permanency for a sow in the herd. Considered incomes come from the sale of piglets and unproductive sows, and costs are due to the feeding of animals, replacement sows purchases, and the operation expenses of the farm. For this analysis, the production process was divided into three major stages called: mating, pregnancy or gestation and lactation. The sow’s movement from one stage to other was modeled by cycle-dependent transition probabilities. Considering the daily utility, as response variable, the model shows the best number of cycles to maintain the sows.
文摘A biomimetic hip joint simulator that can be used to evaluate the outcome of the cemented total hip replacement has been designed, manufactured and evaluated. The simulator produces motion in the extension/flexion plane, with a socket to rotate internal/externally. At the same time a dynamic loading cycle is applied. A validation test was performed on a cemented femoral stem within a novel composite femur. The hone quality has a strong effect on the stem migration and on the integrity of the interfaces. The migration of the stem is a combination of 3-D translation and rotation of the stem. Under the same loading conditions, weak bone allows more stem migration than strong bone. There is a great decrease in the strength of the stem-cement interface after the dynamic test, and the weak bone composite exhibited a greater reduction in interfacial strength than the strong bone composite. The decrease of the interfacial strength indicates that the primary bonding between the stem and the cement mantle had deteriorated and the integrity of stem-cement interface was damaged. The study demonstrates the value of using a hip joint simulator to investigate stem migration and interface integrity within the cemented hip replacement, suggesting that method can be used for in vitro evaluation of the biomaterials used in the cemented hip replacements.
基金Supported by the National Natural Science Foundation of China （20736002）, the National High Technology Research and Development Program of China （2008AA062302） and Program for Changjiang Scholars and Innovative Research Team in University of China （IRT0721）.
文摘Covalent organic framework （COF） is a porous material with low density and large BET （Brtmauer-Emmett-Teller） surface area. They have great potential in gas adsorption and separation. In this work, the adsorption of pure CO2 and CO2/CH4 mixture on modified COF-102 was simulated by using GCMC （grand canonical Monte Carlo）. Metal Li was incorporated into COF-102 through three doping methods, including charge exchange, O^--Li6＋ dipolar interaction and O^--Li^＋ chemical bonding. The influence of Li doping on the adsorption of CO2 was studied. The results showed that among the three methods, the dipole doping is the best way to improve CO2 adsorption performance. Further, the ligands of COF-102 were replaced by extended aromatic moieties, such as diphenyl and pyrene. The adsorption capacity of CO2 and CH4, and the selectivity of CO2/CH4 on the ligand-replaced COF-102 were studied. The capacity of CO2 and CH4 on the ligand-replaced COF-102 had obvious changes; hence the selectivity of CO2/CH4 can be adjusted accordingly.
文摘To gain a competitive edge within the international and compet让ive setting of coal markets, coal producers must find new ways of reducing costs. Increasing bench drilling efficiency and performance in open-cast coal mines has the potential to generate savings. Specifically, monitoring, analyzing, and optimizing the drilling operation can reduce drilling costs. For example, determining the optimal drill bit replacement time will help to achieve the desirable penetration rate. This paper presents a life data analysis of drill bits to fit a statistical distribution using failure records. These results are then used to formulate a cost minimization problem to estimate the drill bit replacement time using the evolutionary algorithm. The effect of cost on the uncertainty associated with replacement time is assessed through Monte-Carlo simulation. The relationship between the total expected replacement cost and replacement time is also presented. A case study shows that the proposed approach can be used to assist with designing a drill bit replacement schedule and minimize costs in open-cast coal mines.
文摘It is a safe and environmentally-friendly method to exploit natural gas hydrates(“hydrate”)by using flue gas(mainly including CO_(2)and N_(2))from electric power plants.So far,however,its energy consumption and energy efficiency has not been investigated thoroughly.In this paper,the process to exploit hydrates from flue gas was established.Firstly,flue gas is injected into hydrate reservoirs after it is pressurized.The hydrates in reservoirs partially experience thermal decomposition while the rest is replaced with flue gas,so CH_(4)-CO_(2)-N_(2)mixture is formed.Secondly,the concentrated CH_(4)-CO_(2)mixture is got after N_(2)is separated and removed by using membrane component.And thirdly,the CH_(4)eCO_(2)mixture is delivered to the original electric power plant.This process was simulated by using the software Aspen Plus to analyze the production/injection ratio in the process of flue gas replacement under different injection pressures,the methane replacement ratio,and the energy consumption and energy efficiency in the whole process.It is indicated that the energy in the process of hydrate exploitation from flue gas is mainly consumed at the pressurized injection stage,and the injection pressure increase correspondingly results in the increase of energy consumption at pressurization and membrane separation stages,and to some extent improves the recovery ratio of pressure energy.Besides,when the injection pressure is 5e16 MPa,the production/injection ratio in the process of flue gas replacement is 0.03-0.26,the methane replacement ratio is 19.9-56.2%,the unit energy consumption in the whole process is 2.15-1.05(kW$h)/kgCH_(4),and the energy return on investment(EROI)is 7.2-14.7.It is concluded that the energy efficiency of hydrate exploitation from flue gas can be effectively improved by increasing the injection pressure in the range of 5e10 MPa.
基金This study was supported bythe National Key Basic Research Development Programgranted by the Ministry of Science and Technology ofChina (MSTC) with project number G1999043500. Itwas also partly supported by the Innovation Program ofthe Chinese
文摘The West Development Policy being implemented in China causes significant land use and land cover (LULC) changes in West China, of which the two most important types of LULC change are replacing farmland and re-greening the desertification land with forest or grass. This paper modifies the prevailing regional climate model (RCM) by updating its lower boundary conditions with the up-to-date satellite database of the Global Land Cover Characteristics Database (GLCCD) created by the United States Geological Survey and the University of Nebraska-Lincoln. The modified RCM is used to simulate the possible regional climate changes due to the LULC variations. The preliminary results can be summarized as that the two main types of LULC variation, replacing farmland and greening the desertification lands with forest or grass in west China, will affect the regional climate mostly in northwest and north China, where the surface temperature will decrease and the precipitation will increase. The regional climate adjustments in South, Southwest China and on the Tibet Plateau are uncertain.
文摘针对命名数据网络(named data networking,NDN)中,路由节点缓存利用的不合理、无法区分内容请求频率的高低,导致路由节点缓存命中率过低的问题,提出了一种基于新鲜因子的缓存替换策略(FRESH)。FRESH策略通过在包结构中新增内容类型、跳数、动态时间3个Tag字段,引入信息熵衡量数据类型的优先级,利用新增Tag字段构建新的替换参量——“新鲜因子”,设计新的缓存替换策略。实验结果表明,在缓存容量比为0.03、Zipf分布参数为0.8的环境下,FRESH策略与DCVRP、CPCA相比较,缓存命中率分别增长了3.5%和6%,明显的提高了缓存命中率,优化了网络中的缓存效率。
