In this article a new approach is considered for implementing operator splitting methods for transport problems, influenced by electric fields. Our motivation came to model PE-CVD (plasma-enhanced chemical vapor depos...In this article a new approach is considered for implementing operator splitting methods for transport problems, influenced by electric fields. Our motivation came to model PE-CVD (plasma-enhanced chemical vapor deposition) processes, means the flow of species to a gas-phase, which are influenced by an electric field. Such a field we can model by wave equations. The main contributions are to improve the standard discretization schemes of each part of the coupling equation. So we discuss an improvement with implicit Runge- Kutta methods instead of the Yee’s algorithm. Further we balance the solver method between the Maxwell and Transport equation.展开更多
The Dancoff correction is important in the calculation of the effective cross section of resonant isotopes in a heterogeneous system. Although the neutron current method is a simple and straightforward approach to est...The Dancoff correction is important in the calculation of the effective cross section of resonant isotopes in a heterogeneous system. Although the neutron current method is a simple and straightforward approach to estimate the Dancoff factor, its use is limited to the black Dancoff factor. In this paper, we expand the current method used to determine both the black and gray Dancoff factors. The method developed also relies on a neutron transport solver, where a fixed source on a fuel rod surface has an outward direction, a cosine distribution, and a constant shape. The detector is located on the surface of the rods to measure incoming and outgoing currents;therefore, there is no need to calculate the chord length, and the development, validation, and verification of the code can be omitted. The mathematical foundation of the suggested method is derived using the integral transport equation. The effects of the moderator and lattice configuration are followed by a sensitivity analysis of the Dancoff factor for several problems, including pressurized water reactor and cluster fuel assemblies. The maximum and average relative errors of the calculated results are approximately 0.3% and 0.05%, respectively.展开更多
为了高效准确地模拟水污染事件中污染物输移过程,该文引入了一套基于GPU加速的水动力及污染物输移的GAST(GPU Accelerated Surface Water Flow and Associated Transport)高分辨率数值模型,并对水污染事件中污染物的输移进行了模拟。模...为了高效准确地模拟水污染事件中污染物输移过程,该文引入了一套基于GPU加速的水动力及污染物输移的GAST(GPU Accelerated Surface Water Flow and Associated Transport)高分辨率数值模型,并对水污染事件中污染物的输移进行了模拟。模型采用Godunov格式的有限体积法求解二维浅水方程和污染物输移方程,利用HLLC(Harten-Lax-van Leer-Contact)近似黎曼求解器计算单元网格界面通量,应用MUSCL限坡线性重构和龙格-库塔时间积分法实现了时空二阶精度,有效地解决了输移方程中对流项产生的数值阻尼过大和剧烈的数值振荡等问题,可准确地模拟复杂地形上干湿界面变化。同时模型引入图形处理器GPU(Graphics Processing Unit)加速计算技术。算例结果表明:模型精度高且稳定性好,能有效抑制数值阻尼和数值振荡,大幅提升了计算效率;模型可用于水污染事故的预警和评估,以期为突发水污染事件的决策提供基础数据和科学支撑。展开更多
Cities are undergoing rapid changes continuously due to the high demands of this era, and simultaneously affect several life fields, namely urban transport. High demands are triggering people to travel more frequently...Cities are undergoing rapid changes continuously due to the high demands of this era, and simultaneously affect several life fields, namely urban transport. High demands are triggering people to travel more frequently than ever;thus, they utilize public transportation more and private transportation less as the latter ceased to fulfill all the transportation needs. Thus, public transportation demand has been increasing greatly alongside citizens’ needs. Nonetheless, many cities lack proper urban traffic planning and organization, while some lack an urban transport service. Ferizaj, a city in Kosovo, is one of the cities that lacks an urban traffic designation;hence, this paper presents a designed urban traffic model, precisely suitable to fulfill the urban transportation need for Ferizaj city. This model is designed under the utilization of applied mathematics’ techniques and operational research. Several factors have been considered, following the geographical distribution of the population, existing roads, and residents’ needs. Consequently, the Solver program has been used as an optimization tool to find the shortest path and most economical paths, added in the discussion part. Besides, the likelihood of the designed urban traffic model’s application in Ferizaj is discussed, considering its viability and application conditions. This study presents mathematical constraints to design a model of the bus network in Ferizaj through Solver. We have used mathematical optimization methods, graph theory, the simulation model through the Solver computer program for network minimal distances and presenting the first model of the Urban traffic network in Ferizaj.展开更多
The purpose of this study is to establish a depth-averaged 2-D hydrodynamic and sediment transport model for the dambreak flows with vegetation effect. The generalized shallow water equations are solved using an expli...The purpose of this study is to establish a depth-averaged 2-D hydrodynamic and sediment transport model for the dambreak flows with vegetation effect. The generalized shallow water equations are solved using an explicit finite volume method with unstructured quadtree rectangular grid, and in the hydrodynamic model, a Harten-Lax-Van Leer（HLL） approximate Riemann solver is used to calculate the intercell flux for capturing the dry-to-wet moving boundary. The sediment transport and bed variation equations in a coupled fashion are calculated by including the bed variation and the variable flow density in the flow continuity and momentum equations. The drag force of vegetation is modeled as the sink terms in the momentum equations. The developed model is tested against lab experiments of the dam-break flows over a fix bed and a movable bed in vegetated and non-vegetated channels. The results are compared with experimental data, and good agreement is obtained. It is shown that the reduced velocity under vegetated conditions leads to a decrease of the peak discharge and a rise of the water level of rivers and also an enhancement of the sediment deposition.展开更多
文摘In this article a new approach is considered for implementing operator splitting methods for transport problems, influenced by electric fields. Our motivation came to model PE-CVD (plasma-enhanced chemical vapor deposition) processes, means the flow of species to a gas-phase, which are influenced by an electric field. Such a field we can model by wave equations. The main contributions are to improve the standard discretization schemes of each part of the coupling equation. So we discuss an improvement with implicit Runge- Kutta methods instead of the Yee’s algorithm. Further we balance the solver method between the Maxwell and Transport equation.
文摘The Dancoff correction is important in the calculation of the effective cross section of resonant isotopes in a heterogeneous system. Although the neutron current method is a simple and straightforward approach to estimate the Dancoff factor, its use is limited to the black Dancoff factor. In this paper, we expand the current method used to determine both the black and gray Dancoff factors. The method developed also relies on a neutron transport solver, where a fixed source on a fuel rod surface has an outward direction, a cosine distribution, and a constant shape. The detector is located on the surface of the rods to measure incoming and outgoing currents;therefore, there is no need to calculate the chord length, and the development, validation, and verification of the code can be omitted. The mathematical foundation of the suggested method is derived using the integral transport equation. The effects of the moderator and lattice configuration are followed by a sensitivity analysis of the Dancoff factor for several problems, including pressurized water reactor and cluster fuel assemblies. The maximum and average relative errors of the calculated results are approximately 0.3% and 0.05%, respectively.
文摘Cities are undergoing rapid changes continuously due to the high demands of this era, and simultaneously affect several life fields, namely urban transport. High demands are triggering people to travel more frequently than ever;thus, they utilize public transportation more and private transportation less as the latter ceased to fulfill all the transportation needs. Thus, public transportation demand has been increasing greatly alongside citizens’ needs. Nonetheless, many cities lack proper urban traffic planning and organization, while some lack an urban transport service. Ferizaj, a city in Kosovo, is one of the cities that lacks an urban traffic designation;hence, this paper presents a designed urban traffic model, precisely suitable to fulfill the urban transportation need for Ferizaj city. This model is designed under the utilization of applied mathematics’ techniques and operational research. Several factors have been considered, following the geographical distribution of the population, existing roads, and residents’ needs. Consequently, the Solver program has been used as an optimization tool to find the shortest path and most economical paths, added in the discussion part. Besides, the likelihood of the designed urban traffic model’s application in Ferizaj is discussed, considering its viability and application conditions. This study presents mathematical constraints to design a model of the bus network in Ferizaj through Solver. We have used mathematical optimization methods, graph theory, the simulation model through the Solver computer program for network minimal distances and presenting the first model of the Urban traffic network in Ferizaj.
基金supported by the Public Science and Technology Research Funds Projects of Ocean(Grant No.201205023)the Program for Liaoning Province Excellent Talents in University(Grant No.LJQ2013077)+1 种基金the Science and Technology Founda-tion of Dalian City(Grant No.2013J21DW009)the Natu-ral Science Foundation of Liaoning Province(Grant No.2014020148)
文摘The purpose of this study is to establish a depth-averaged 2-D hydrodynamic and sediment transport model for the dambreak flows with vegetation effect. The generalized shallow water equations are solved using an explicit finite volume method with unstructured quadtree rectangular grid, and in the hydrodynamic model, a Harten-Lax-Van Leer（HLL） approximate Riemann solver is used to calculate the intercell flux for capturing the dry-to-wet moving boundary. The sediment transport and bed variation equations in a coupled fashion are calculated by including the bed variation and the variable flow density in the flow continuity and momentum equations. The drag force of vegetation is modeled as the sink terms in the momentum equations. The developed model is tested against lab experiments of the dam-break flows over a fix bed and a movable bed in vegetated and non-vegetated channels. The results are compared with experimental data, and good agreement is obtained. It is shown that the reduced velocity under vegetated conditions leads to a decrease of the peak discharge and a rise of the water level of rivers and also an enhancement of the sediment deposition.
