Targeted genome editing is a continually evolving technology employing programmable nucleases to specifically change,insert,or remove a genomic sequence of interest.These advanced molecular tools include meganucleases...Targeted genome editing is a continually evolving technology employing programmable nucleases to specifically change,insert,or remove a genomic sequence of interest.These advanced molecular tools include meganucleases,zinc finger nucleases,transcription activator-like effector nucleases and RNA-guided engineered nucleases(RGENs),which create double-strand breaks at specific target sites in the genome,and repair DNA either by homologous recombination in the presence of donor DNA or via the error-prone non-homologous end-joining mechanism.A recently discovered group of RGENs known as CRISPR/Cas9 gene-editing systems allowed precise genome manipulation revealing a causal association between disease genotype and phenotype,without the need for the reengineering of the specific enzyme when targeting different sequences.CRISPR/Cas9 has been successfully employed as an ex vivo gene-editing tool in embryonic stem cells and patient-derived stem cells to understand pancreatic beta-cell development and function.RNA-guided nucleases also open the way for the generation of novel animal models for diabetes and allow testing the efficiency of various therapeutic approaches in diabetes,as summarized and exemplified in this manuscript.展开更多
The Qilian mountain area was examined for using the Logistic-CA-Markov coupling model combined with GIS spatial analyst technology to research the transformation of LUCC, driving force system and simulate future tende...The Qilian mountain area was examined for using the Logistic-CA-Markov coupling model combined with GIS spatial analyst technology to research the transformation of LUCC, driving force system and simulate future tendency of variation. Results show that： （1） Woodland area decreased by 12.55%, while grassland, cultivated land, and settlement areas increased by 0.22%, 7.92%, and 0.03%, respectively, from 1986 to 2014. During the period of 1986 to 2000, forest degradation in the middle section of the mountain area decreased by 1,501.69 km2. Vegetation cover area improved, with a net increase of grassland area of 38.12 km2 from 2000 to 2014. （2） For constructing the system driving force, the best simulation scale was 210m×210m. Based on logistic regression analysis, the contribution （weight） of composite driving forces to land use and cover change was obtained, and the weight value was more objectively compared with AHP and MCE method. （3） In the natural scenarios, it is predicted that land use and cover distribution maps of Qilian mountain area in 2028 and 2042, and the Lee-Sallee index test was adopted. Over the next 27 years （2015-2042）, farmland, woodland, grassland, settlement areas show an increasing trend, especially settlements with an obvious change of 0.56%. The area of bare land will decrease by 0.89%. Without environmental degradation, tremendous structural change of LUCC will not occur, and typical characteristic of the vertical zone of the mountain would remain. Farmland and settlement areas will increase, but only in the vicinity of Qilian and Sunan counties.展开更多
Associative memory, one of the major cognitive functions in the hippocampal CA3 region, includes auto-associative memory and hetero-associative memory. Many previous studies have shown that Alzheimer＇s disease （AD）...Associative memory, one of the major cognitive functions in the hippocampal CA3 region, includes auto-associative memory and hetero-associative memory. Many previous studies have shown that Alzheimer＇s disease （AD） can lead to loss of functional synapses in the central nervous system, and associative memory functions in patients with AD are often impaired, but few studies have addressed the effect of AD on hetero-associative memory in the hippocampal CA3 region. In this study, based on a simplified anatomical structure and synaptic connections in the hippocampal CA3 region, a three-layered Hopfield-like neural network model of hippocampal CA3 was proposed and then used to simulate associative memory functions in three circumstances： normal, synaptic deletion and synaptic compensation, according to Ruppin＇s synaptic deletion and compensation theory. The influences of AD on hetero-associative memory were further analyzed. The simulated results showed that the established three-layered Hopfield-like neural network model of hippocampal CA3 has both auto-associative and hetero-associative memory functions. With increasing synaptic deletion level, both associative memory functions were gradually impaired and the mean firing rates of the neurons within the network model were decreased. With gradual increasing synaptic compensation, the associative memory functions of the network were improved and the mean firing rates were increased. The simulated results suggest that the Hopfield-like neural network model can effectively simulate both associative memory functions of the hippocampal CA3 region. Synaptic deletion affects both auto-associative and hetero-associative memory functions in the hippocampal CA3 region, and can also result in memory dysfunction. To some extent, synaptic compensation measures can offset two kinds of associative memory dysfunction caused by synaptic deletion in the hippocampal CA3 area.展开更多
High-accuracy geoid determination is an essential goal that many groups of scientists and countries are striving to achieve. Techniques for determining geoid models have evolved over time. Unfortunately, this all-impo...High-accuracy geoid determination is an essential goal that many groups of scientists and countries are striving to achieve. Techniques for determining geoid models have evolved over time. Unfortunately, this all-important determination requires relatively substantial technical and financial resources, depending on the type of geoid to be determined. This situation justifies the inadequacy, and sometimes absence, of accurate geoid models in many countries, despite the new challenges of altimetric positioning using space or satellite positioning techniques. This study focuses on the establishment of a geometric geoid model using simplistic techniques that are accessible and applicable in restricted or wide areas, with or without gravimetric data. The study was applied to the Dakar-Thiès-Mbour triangle, the two regions in the extreme west of Senegal that are home to the most infrastructure projects with the highest socio-economic stakes, as well as mines currently being exploited, and therefore the highest stakes in terms of positioning. This study also enabled us to assess the accuracy of a number of global field models in Senegal, which are used by some professionals for altimetric positioning using Global Positioning Satellite Systems (GNSS) in the absence of a local geoid model. The estimated geoid model is based on the determination of undulation at various sample points in the study area. To this end, a campaign of GNSS observations and direct levelling was carried out on the various points spread across the study area. These measurements were then used to determine the undulation at each point. Bilinear interpolation was used to deduce the undulations throughout the study area, based on the altimeter conversion grid. This grid was evaluated using GPS/level control points.展开更多
In consideration of the mechanism for shear-stress-induced Ca^2＋ influx via ATP（adenosine triphosphate）-gated ion channel P2X4 in vascular endothelial cells, a modified model is proposed to describe the shear-stres...In consideration of the mechanism for shear-stress-induced Ca^2＋ influx via ATP（adenosine triphosphate）-gated ion channel P2X4 in vascular endothelial cells, a modified model is proposed to describe the shear-stress-induced Ca^2＋ influx. It is affected both by the Ca^2＋ gradient across the cell membrane and extracellular ATP concentration on the cell surface. Meanwhile, a new static ATP release model is constructed by using published experimental data. Combining the modified intracellular calcium dynamics model with the new ATP release model, we establish a nonlinear Ca^2＋ dynamic system in vascular endothelial cells. The ATP-mediated calcium response in vascular endothelial cells subjected to shear stresses is analyzed by solving the governing equations of the integrated dynamic system. Numerical results show that the shear-stress-induced calcium response predicted by the proposed model is more consistent with the experimental observations than that predicted by existing models.展开更多
本刊讯5月22日，CA宣布推出新版本的AllFusion Modeling Suite建模工具，在功能强大的AllFusion Erwin Data Modeler内嵌具有专利的通用的数据建模引擎。通过简化复杂数据库应用的设计、实施和分析，AllFusion Modeling Suite r7将帮助I...本刊讯5月22日，CA宣布推出新版本的AllFusion Modeling Suite建模工具，在功能强大的AllFusion Erwin Data Modeler内嵌具有专利的通用的数据建模引擎。通过简化复杂数据库应用的设计、实施和分析，AllFusion Modeling Suite r7将帮助IT部门加快应用交付、提升员工生产力及控制数据库的拥有成本。同时，它还可提供全面的数据库及数据仓库变化的审计记录，促进公司遵从法规并迅速发现问题。展开更多
Portable X-ray fluorescence(pXRF) spectrometers can be used to determine the elemental composition easily, rapidly, and without using chemical reagents, which is very important for tropical regions due to the lack of ...Portable X-ray fluorescence(pXRF) spectrometers can be used to determine the elemental composition easily, rapidly, and without using chemical reagents, which is very important for tropical regions due to the lack of detailed soil characterization data. Moreover,pXRF data can be used to predict the results of more expensive, time-consuming, and conventional laboratory analyses. This study sought to determine the elemental composition of various soil profiles using pXRF. Two operational modes(Trace Mode and General Mode) and two scanning time(30 and 60 s) were assessed to determine their effects on the correlation of pXRF dataset with respect to conventional inductively coupled plasma(ICP)-optical emission spectrometry analysis. This relationship has been reported in previous studies, however, few studies were performed on tropical soils, which are unique. Furthermore, such relationships establish the viability of developing prediction models directly from pXRF data. Linear regression was applied to develop calibration models for the prediction of ICP analysis results and exchangeable and available elemental contents based on pXRF data. High coefficients of determination(R^2) were obtained for Ca(0.87), Cu(0.90), Fe(0.95), Mn(0.85), Cr(0.95), V(0.72), and Ni(0.90), with adequate validation. Statistically significant results were not found for Al, K, Zn, Ti, and Zr. The models predicting the exchangeable Ca based on the total Ca from p XRF reached an R^2 of up to 0.85. Operational modes influenced the pXRF results. Our results illustrate that pXRF holds great promise for tropical soil characterization and the development of prediction models, justifying the need for larger-scale studies in tropical countries worldwide.展开更多
Walking in groups is very common in a realistic walking environment. An extended floor field cellular automaton （CA） model is therefore proposed to describe the walking behavior of pedestrian groups, This model repr...Walking in groups is very common in a realistic walking environment. An extended floor field cellular automaton （CA） model is therefore proposed to describe the walking behavior of pedestrian groups, This model represents the motion of pedestrian groups in a realistic way. The simulation results reveal that the walking behavior of groups has an important but negative influence on pedestrian flow dynamics, especially when the density is at a high level. The presence of pedestrian groups retards the emergence of lane formation and increases the instability of operation of pedestrian flow. Moreover, the average velocity and volume of pedestrian flow are significantly reduced due to the group motion. Meanwhile, the parameter-sensitive analysis suggests that pedestrian groups should make a compromise between efficient movement and staying coherent with a certain spatial structure when walking in a dense crowd.展开更多
Targeted genome editing technology has been widely used in biomedical studies. The CRISPR- associated RNA-guided endonuclease Cas9 has become a versatile genome editing tool. The CRISPR/Cas9 system is useful for study...Targeted genome editing technology has been widely used in biomedical studies. The CRISPR- associated RNA-guided endonuclease Cas9 has become a versatile genome editing tool. The CRISPR/Cas9 system is useful for studying gene function through efficient knock-out, knock-in or chromatin modification of the targeted gene loci in various cell types and organisms. It can be applied in a number of fields, such as genetic breeding, disease treatment and gene functional investigation In this review, we introduce the most recent developments and applications, the challenges, and future directions of Cas9 in generating disease animal model. Derived from the CRISPR adaptive immune system of bacteria, the development trend of Cas9 will inevitably fuel the vital applications from basic research to biotechnology and bio- medicine.展开更多
Animal models are extensively used in all aspects of biomedical research,with substantial contributions to our understanding of diseases,the development of pharmaceuticals,and the exploration of gene functions.The fie...Animal models are extensively used in all aspects of biomedical research,with substantial contributions to our understanding of diseases,the development of pharmaceuticals,and the exploration of gene functions.The field of genome modification in rabbits has progressed slowly.However,recent advancements,particularly in CRISPR/Cas9-related technologies,have catalyzed the successful development of various genome-edited rabbit models to mimic diverse diseases,including cardiovascular disorders,immunodeficiencies,agingrelated ailments,neurological diseases,and ophthalmic pathologies.These models hold great promise in advancing biomedical research due to their closer physiological and biochemical resemblance to humans compared to mice.This review aims to summarize the novel gene-editing approaches currently available for rabbits and present the applications and prospects of such models in biomedicine,underscoring their impact and future potential in translational medicine.展开更多
A model combined both macroscopic transport and microstructural evolution is applied to describe the influence of thermosolutal convection on microstructural evolution during the solidification process. Firstly, the v...A model combined both macroscopic transport and microstructural evolution is applied to describe the influence of thermosolutal convection on microstructural evolution during the solidification process. Firstly, the volume average method and Simpler algorithm are used to solve the macroscopic transport equation. Then the calculated results are incorporated into the cellular automaton (CA) model to simulate the microstructural evolution. Using this model, a simple casting ingot is applied to simulate microstructural evolution. Through the simulation, it is found that the thermosolutal convection has a strong influence on the redistribution of temperature field and solute field, which influence the solidification microstructural evolution.展开更多
In this study,the transmission capacity of VANETs in a highway scenario is analysed on the basis of a 1D line model and the carrier sense multiple access with collision avoidance(CSMA/CA)protocol.We describe the CSMA/...In this study,the transmission capacity of VANETs in a highway scenario is analysed on the basis of a 1D line model and the carrier sense multiple access with collision avoidance(CSMA/CA)protocol.We describe the CSMA/CA protocol used in IEEE802.11 p from the perspective of the geometric relationship amongst simultaneous transmitters.The desired channel and interfering channels are assumed to experience the same amount of path-loss and Rayleigh fading.On the basis of the proposed model,we analyse the attempted transmission probability of each road segment and the maximum intensity of active transmitters,including their theoretical values.Then,we employ the physical model to obtain the outage probability and derive the upper bound of the transmission capacity of a VANET,which is defined as the average spatial density of successful transmissions in the network.Simulation results indicate that the theoretical value offers a good bound on network capacity.展开更多
基金the Akdeniz University Scientific Research Commission and the Scientific and Technological Research Council of Turkey,No.TUBITAK-215S820.
文摘Targeted genome editing is a continually evolving technology employing programmable nucleases to specifically change,insert,or remove a genomic sequence of interest.These advanced molecular tools include meganucleases,zinc finger nucleases,transcription activator-like effector nucleases and RNA-guided engineered nucleases(RGENs),which create double-strand breaks at specific target sites in the genome,and repair DNA either by homologous recombination in the presence of donor DNA or via the error-prone non-homologous end-joining mechanism.A recently discovered group of RGENs known as CRISPR/Cas9 gene-editing systems allowed precise genome manipulation revealing a causal association between disease genotype and phenotype,without the need for the reengineering of the specific enzyme when targeting different sequences.CRISPR/Cas9 has been successfully employed as an ex vivo gene-editing tool in embryonic stem cells and patient-derived stem cells to understand pancreatic beta-cell development and function.RNA-guided nucleases also open the way for the generation of novel animal models for diabetes and allow testing the efficiency of various therapeutic approaches in diabetes,as summarized and exemplified in this manuscript.
基金supported by National Natural Science Foundation of China (No. 4961038)Natural Science Foundation of Sichuan Province Education Department (No. 16ZB0402)+1 种基金Engineering and Technical College of Chengdu University of Technology Foundation (No. C122014014)the key research projects of Science and Technology Bureau of Leshan Town
文摘The Qilian mountain area was examined for using the Logistic-CA-Markov coupling model combined with GIS spatial analyst technology to research the transformation of LUCC, driving force system and simulate future tendency of variation. Results show that： （1） Woodland area decreased by 12.55%, while grassland, cultivated land, and settlement areas increased by 0.22%, 7.92%, and 0.03%, respectively, from 1986 to 2014. During the period of 1986 to 2000, forest degradation in the middle section of the mountain area decreased by 1,501.69 km2. Vegetation cover area improved, with a net increase of grassland area of 38.12 km2 from 2000 to 2014. （2） For constructing the system driving force, the best simulation scale was 210m×210m. Based on logistic regression analysis, the contribution （weight） of composite driving forces to land use and cover change was obtained, and the weight value was more objectively compared with AHP and MCE method. （3） In the natural scenarios, it is predicted that land use and cover distribution maps of Qilian mountain area in 2028 and 2042, and the Lee-Sallee index test was adopted. Over the next 27 years （2015-2042）, farmland, woodland, grassland, settlement areas show an increasing trend, especially settlements with an obvious change of 0.56%. The area of bare land will decrease by 0.89%. Without environmental degradation, tremendous structural change of LUCC will not occur, and typical characteristic of the vertical zone of the mountain would remain. Farmland and settlement areas will increase, but only in the vicinity of Qilian and Sunan counties.
基金the National Natural Science Foundation of China,No.30870649the Natural Science Foundation of Tianjin,No.08JCYBJC03300
文摘Associative memory, one of the major cognitive functions in the hippocampal CA3 region, includes auto-associative memory and hetero-associative memory. Many previous studies have shown that Alzheimer＇s disease （AD） can lead to loss of functional synapses in the central nervous system, and associative memory functions in patients with AD are often impaired, but few studies have addressed the effect of AD on hetero-associative memory in the hippocampal CA3 region. In this study, based on a simplified anatomical structure and synaptic connections in the hippocampal CA3 region, a three-layered Hopfield-like neural network model of hippocampal CA3 was proposed and then used to simulate associative memory functions in three circumstances： normal, synaptic deletion and synaptic compensation, according to Ruppin＇s synaptic deletion and compensation theory. The influences of AD on hetero-associative memory were further analyzed. The simulated results showed that the established three-layered Hopfield-like neural network model of hippocampal CA3 has both auto-associative and hetero-associative memory functions. With increasing synaptic deletion level, both associative memory functions were gradually impaired and the mean firing rates of the neurons within the network model were decreased. With gradual increasing synaptic compensation, the associative memory functions of the network were improved and the mean firing rates were increased. The simulated results suggest that the Hopfield-like neural network model can effectively simulate both associative memory functions of the hippocampal CA3 region. Synaptic deletion affects both auto-associative and hetero-associative memory functions in the hippocampal CA3 region, and can also result in memory dysfunction. To some extent, synaptic compensation measures can offset two kinds of associative memory dysfunction caused by synaptic deletion in the hippocampal CA3 area.
文摘High-accuracy geoid determination is an essential goal that many groups of scientists and countries are striving to achieve. Techniques for determining geoid models have evolved over time. Unfortunately, this all-important determination requires relatively substantial technical and financial resources, depending on the type of geoid to be determined. This situation justifies the inadequacy, and sometimes absence, of accurate geoid models in many countries, despite the new challenges of altimetric positioning using space or satellite positioning techniques. This study focuses on the establishment of a geometric geoid model using simplistic techniques that are accessible and applicable in restricted or wide areas, with or without gravimetric data. The study was applied to the Dakar-Thiès-Mbour triangle, the two regions in the extreme west of Senegal that are home to the most infrastructure projects with the highest socio-economic stakes, as well as mines currently being exploited, and therefore the highest stakes in terms of positioning. This study also enabled us to assess the accuracy of a number of global field models in Senegal, which are used by some professionals for altimetric positioning using Global Positioning Satellite Systems (GNSS) in the absence of a local geoid model. The estimated geoid model is based on the determination of undulation at various sample points in the study area. To this end, a campaign of GNSS observations and direct levelling was carried out on the various points spread across the study area. These measurements were then used to determine the undulation at each point. Bilinear interpolation was used to deduce the undulations throughout the study area, based on the altimeter conversion grid. This grid was evaluated using GPS/level control points.
基金the National Natural Science Foundation of China(No.10472027) the NUS Academic Research Fund(No.R-263-000-483-112)
文摘In consideration of the mechanism for shear-stress-induced Ca^2＋ influx via ATP（adenosine triphosphate）-gated ion channel P2X4 in vascular endothelial cells, a modified model is proposed to describe the shear-stress-induced Ca^2＋ influx. It is affected both by the Ca^2＋ gradient across the cell membrane and extracellular ATP concentration on the cell surface. Meanwhile, a new static ATP release model is constructed by using published experimental data. Combining the modified intracellular calcium dynamics model with the new ATP release model, we establish a nonlinear Ca^2＋ dynamic system in vascular endothelial cells. The ATP-mediated calcium response in vascular endothelial cells subjected to shear stresses is analyzed by solving the governing equations of the integrated dynamic system. Numerical results show that the shear-stress-induced calcium response predicted by the proposed model is more consistent with the experimental observations than that predicted by existing models.
文摘本刊讯5月22日，CA宣布推出新版本的AllFusion Modeling Suite建模工具，在功能强大的AllFusion Erwin Data Modeler内嵌具有专利的通用的数据建模引擎。通过简化复杂数据库应用的设计、实施和分析，AllFusion Modeling Suite r7将帮助IT部门加快应用交付、提升员工生产力及控制数据库的拥有成本。同时，它还可提供全面的数据库及数据仓库变化的审计记录，促进公司遵从法规并迅速发现问题。
基金the Brazilian funding agenciesNational Council for Scientific and Technological Development(CNPq)+1 种基金Coordination of Superior Level Staff Improvement(CAPES)Foundation for Research of the State of Minas Gerais(FAPEMIG)
文摘Portable X-ray fluorescence(pXRF) spectrometers can be used to determine the elemental composition easily, rapidly, and without using chemical reagents, which is very important for tropical regions due to the lack of detailed soil characterization data. Moreover,pXRF data can be used to predict the results of more expensive, time-consuming, and conventional laboratory analyses. This study sought to determine the elemental composition of various soil profiles using pXRF. Two operational modes(Trace Mode and General Mode) and two scanning time(30 and 60 s) were assessed to determine their effects on the correlation of pXRF dataset with respect to conventional inductively coupled plasma(ICP)-optical emission spectrometry analysis. This relationship has been reported in previous studies, however, few studies were performed on tropical soils, which are unique. Furthermore, such relationships establish the viability of developing prediction models directly from pXRF data. Linear regression was applied to develop calibration models for the prediction of ICP analysis results and exchangeable and available elemental contents based on pXRF data. High coefficients of determination(R^2) were obtained for Ca(0.87), Cu(0.90), Fe(0.95), Mn(0.85), Cr(0.95), V(0.72), and Ni(0.90), with adequate validation. Statistically significant results were not found for Al, K, Zn, Ti, and Zr. The models predicting the exchangeable Ca based on the total Ca from p XRF reached an R^2 of up to 0.85. Operational modes influenced the pXRF results. Our results illustrate that pXRF holds great promise for tropical soil characterization and the development of prediction models, justifying the need for larger-scale studies in tropical countries worldwide.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51278101 and 51338003)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20120092110043)the Scientific Innovation Research Project of College Graduate in Jiangsu Province,China(Grant No.CXZZ13 0117)
文摘Walking in groups is very common in a realistic walking environment. An extended floor field cellular automaton （CA） model is therefore proposed to describe the walking behavior of pedestrian groups, This model represents the motion of pedestrian groups in a realistic way. The simulation results reveal that the walking behavior of groups has an important but negative influence on pedestrian flow dynamics, especially when the density is at a high level. The presence of pedestrian groups retards the emergence of lane formation and increases the instability of operation of pedestrian flow. Moreover, the average velocity and volume of pedestrian flow are significantly reduced due to the group motion. Meanwhile, the parameter-sensitive analysis suggests that pedestrian groups should make a compromise between efficient movement and staying coherent with a certain spatial structure when walking in a dense crowd.
基金partially supported by the National Natural Science Foundation of China(81202110,81120108019,U1132605 and 81325016)
文摘Targeted genome editing technology has been widely used in biomedical studies. The CRISPR- associated RNA-guided endonuclease Cas9 has become a versatile genome editing tool. The CRISPR/Cas9 system is useful for studying gene function through efficient knock-out, knock-in or chromatin modification of the targeted gene loci in various cell types and organisms. It can be applied in a number of fields, such as genetic breeding, disease treatment and gene functional investigation In this review, we introduce the most recent developments and applications, the challenges, and future directions of Cas9 in generating disease animal model. Derived from the CRISPR adaptive immune system of bacteria, the development trend of Cas9 will inevitably fuel the vital applications from basic research to biotechnology and bio- medicine.
基金supported by the National Natural Science Foundation of China (31970574)。
文摘Animal models are extensively used in all aspects of biomedical research,with substantial contributions to our understanding of diseases,the development of pharmaceuticals,and the exploration of gene functions.The field of genome modification in rabbits has progressed slowly.However,recent advancements,particularly in CRISPR/Cas9-related technologies,have catalyzed the successful development of various genome-edited rabbit models to mimic diverse diseases,including cardiovascular disorders,immunodeficiencies,agingrelated ailments,neurological diseases,and ophthalmic pathologies.These models hold great promise in advancing biomedical research due to their closer physiological and biochemical resemblance to humans compared to mice.This review aims to summarize the novel gene-editing approaches currently available for rabbits and present the applications and prospects of such models in biomedicine,underscoring their impact and future potential in translational medicine.
文摘A model combined both macroscopic transport and microstructural evolution is applied to describe the influence of thermosolutal convection on microstructural evolution during the solidification process. Firstly, the volume average method and Simpler algorithm are used to solve the macroscopic transport equation. Then the calculated results are incorporated into the cellular automaton (CA) model to simulate the microstructural evolution. Using this model, a simple casting ingot is applied to simulate microstructural evolution. Through the simulation, it is found that the thermosolutal convection has a strong influence on the redistribution of temperature field and solute field, which influence the solidification microstructural evolution.
基金supported in part by the National Natural Science Foundation of China under Grant No.61271184 and 61571065
文摘In this study,the transmission capacity of VANETs in a highway scenario is analysed on the basis of a 1D line model and the carrier sense multiple access with collision avoidance(CSMA/CA)protocol.We describe the CSMA/CA protocol used in IEEE802.11 p from the perspective of the geometric relationship amongst simultaneous transmitters.The desired channel and interfering channels are assumed to experience the same amount of path-loss and Rayleigh fading.On the basis of the proposed model,we analyse the attempted transmission probability of each road segment and the maximum intensity of active transmitters,including their theoretical values.Then,we employ the physical model to obtain the outage probability and derive the upper bound of the transmission capacity of a VANET,which is defined as the average spatial density of successful transmissions in the network.Simulation results indicate that the theoretical value offers a good bound on network capacity.
