With the linear interpolation method, an improved absorbing boundary condition（ABC）is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain （ADI-FDTD） meth...With the linear interpolation method, an improved absorbing boundary condition（ABC）is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain （ADI-FDTD） method. The reflection of the ABC caused by both the truncated error and the phase velocity error is analyzed. Based on the phase velocity estimation and the nonuniform cell, two methods are studied and then adopted to improve the performance of the ABC. A calculation case of a rectangular waveguide which is a typical dispersive transmission line is carried out using the ADI-FDTD method with the improved ABC for evaluation. According to the calculated case, the comparison is given between the reflection coefficients of the ABC with and without the velocity estimation and also the comparison between the reflection coefficients of the ABC with and without the nonuniform processing. The reflection variation of the ABC under different time steps is also analyzed and the acceptable worsening will not obscure the improvement on the absorption. Numerical results obviously show that efficient improvement on the absorbing performance of the ABC is achieved based on these methods for the ADI-FDTD.展开更多
In this paper, Finite Difference Time Domain (FDTD) is utilized to simulate metamaterials of Double Negative (DNG) origin that refers to those materials having simultaneous negative permittivity and permeability. The ...In this paper, Finite Difference Time Domain (FDTD) is utilized to simulate metamaterials of Double Negative (DNG) origin that refers to those materials having simultaneous negative permittivity and permeability. The problem regarding space formulation is achieved by means of auxiliary differential equation method (ADE), which is easy, reliable and also causal process in nature thus making it proficient. It uses fair approximations to explicate the model. Mur’s boundary condition is used for 1-D problem space and convolution perfectly matched layer boundary is implemented for 2-D problem space. The properties of metamaterial conform their speculations of energy absorption, enhancement and backward propagation property with the aid of graphs engineered by Matlab simulation both in 1-D and 2-D. Also, the interaction of fields on DNG and Double Positive (DPS) layers is contrasted. The results achieved elucidate the validity and effectiveness of the ADE method and the Convolution Perfectly Match Layer (CPML) in designing DNG metamaterials.展开更多
Road transport is a flexible mode of transport and its importance in era of globalization increases. Management of road transport companies is, in this turbulent environment, exposed to many technical, legislative, an...Road transport is a flexible mode of transport and its importance in era of globalization increases. Management of road transport companies is, in this turbulent environment, exposed to many technical, legislative, and economic problems. Especially, the growing economic pressure leads to an urgent requirement of the manager and control system improvement. Activity-based costing （ABC） method is a very powerful tool to improve products, services, processes, and market strategies. ABC allows company management to understand what causes costs and how to manage them. Company under this scheme may get a glimpse of how efficiently a company converts the source value. The main objective of our research was to assess the possibility of application of the ABC method in a transport undertaking. ABC method as a fundamentally different view on the cost in the transport business helps to find the reasons of cost and thereby influences their levels to make better use of resources.. New managerial accounting methods aim to show management what information is needed, how and where this information can be obtained, and how they can be useful for the management of the company＇s proper planning, decision-making, and control. Information provided by management accounting is often a key factor in the analysis of alternative ways of solving problems. This article focuses on the transport enterprise management and helps to decide on the use of this method in business practice.展开更多
基金The National Natural Science Foundation of China(No.60702027)the Free Research Fund of the National Mobile Communications Research Laboratory of Southeast University (No.2008B07)the National Basic Research Program of China(973 Program)(No.2007CB310603)
文摘With the linear interpolation method, an improved absorbing boundary condition（ABC）is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain （ADI-FDTD） method. The reflection of the ABC caused by both the truncated error and the phase velocity error is analyzed. Based on the phase velocity estimation and the nonuniform cell, two methods are studied and then adopted to improve the performance of the ABC. A calculation case of a rectangular waveguide which is a typical dispersive transmission line is carried out using the ADI-FDTD method with the improved ABC for evaluation. According to the calculated case, the comparison is given between the reflection coefficients of the ABC with and without the velocity estimation and also the comparison between the reflection coefficients of the ABC with and without the nonuniform processing. The reflection variation of the ABC under different time steps is also analyzed and the acceptable worsening will not obscure the improvement on the absorption. Numerical results obviously show that efficient improvement on the absorbing performance of the ABC is achieved based on these methods for the ADI-FDTD.
文摘In this paper, Finite Difference Time Domain (FDTD) is utilized to simulate metamaterials of Double Negative (DNG) origin that refers to those materials having simultaneous negative permittivity and permeability. The problem regarding space formulation is achieved by means of auxiliary differential equation method (ADE), which is easy, reliable and also causal process in nature thus making it proficient. It uses fair approximations to explicate the model. Mur’s boundary condition is used for 1-D problem space and convolution perfectly matched layer boundary is implemented for 2-D problem space. The properties of metamaterial conform their speculations of energy absorption, enhancement and backward propagation property with the aid of graphs engineered by Matlab simulation both in 1-D and 2-D. Also, the interaction of fields on DNG and Double Positive (DPS) layers is contrasted. The results achieved elucidate the validity and effectiveness of the ADE method and the Convolution Perfectly Match Layer (CPML) in designing DNG metamaterials.
文摘Road transport is a flexible mode of transport and its importance in era of globalization increases. Management of road transport companies is, in this turbulent environment, exposed to many technical, legislative, and economic problems. Especially, the growing economic pressure leads to an urgent requirement of the manager and control system improvement. Activity-based costing （ABC） method is a very powerful tool to improve products, services, processes, and market strategies. ABC allows company management to understand what causes costs and how to manage them. Company under this scheme may get a glimpse of how efficiently a company converts the source value. The main objective of our research was to assess the possibility of application of the ABC method in a transport undertaking. ABC method as a fundamentally different view on the cost in the transport business helps to find the reasons of cost and thereby influences their levels to make better use of resources.. New managerial accounting methods aim to show management what information is needed, how and where this information can be obtained, and how they can be useful for the management of the company＇s proper planning, decision-making, and control. Information provided by management accounting is often a key factor in the analysis of alternative ways of solving problems. This article focuses on the transport enterprise management and helps to decide on the use of this method in business practice.
