With the rapid development of manufacturing technology, the traditional simulation of machining can not meet the people’s need. Research on virtual machining environment is one of the key parts of virtual manufacturi...With the rapid development of manufacturing technology, the traditional simulation of machining can not meet the people’s need. Research on virtual machining environment is one of the key parts of virtual manufacturing technology. According to the features of virtual turning, this paper proposes a simplified Whitted lighting model based on analysis of Phong and other local illumination model. This model takes the material and roughness of workpiece into account to calculate the roughness coefficient D, geometric fading coefficient G and Fresenel transmission coefficient F’ so that the light intensity in the scene can be got more realisticly. Moreover, to obtain the natural lighting effects, based on the analysis of motion space of machine tools, local ray tracing algorithm is given to calculate the light intensity of every position during the course of simulation. This method can not only simulate the machining environment accurately, but also reduce the calculating time greatly. For example, if CPU is 1.3 G and internal memory is 128 M, the refresh time using the original algorithm is 0.1 second, while it becomes 0.01 seconds by local refreshing. Besides, to get more realistic machining scene, the paper deduce the transfer matrix from chip coordinate to feeding coordinate so that the chip model can be integrated into the whole machining scene. At last, a example of virtual cutting scene is shown to demonstrate the effects of global illumination model and helical chip simulation. The system can give the user high true sensation. The user can operate the machine tools through the controlling panel and watch the cutting process from different viewing angle. The data needed for construction of scene and chip simulation is obtained form the C616 lathe. This study plays important role in richening virtual manufacturing theory and promoting the development of advanced manufacturing technology.展开更多
A global prognostic model based on MOM4p1,which is a primitive equation nonBoussinesq numerical model,has been integrated with 1 400 years from the state of rest based on the realistic topography to study the long-ter...A global prognostic model based on MOM4p1,which is a primitive equation nonBoussinesq numerical model,has been integrated with 1 400 years from the state of rest based on the realistic topography to study the long-term pattern of combined wind-driven and thermodynamically-driven general circulation.The model is driven by monthly climatological mean forces and includes 192×189 horizontal grids and 31 pressure-based vertical levels.The main objective is to investigate the mass and heat transports at interbasin passages and their compensations and roles in the global ocean circulation under equilibrium state of long-term spin up.The kinetic energy analysis divides the spin up process into three stages：the quasi-stable state of wind driven current,the growing phase of thermodynamical circulation and the equilibrium state of thermohaline circulation.It is essential to spin up over a thousand years in order to reach the thermohaline equilibrium state from a state of rest.The Arctic Throughflow from the Bering Strait to the Greenland Sea and the Indonesian Throughflow（ITF） are captured and examined with their compensations and existing data.Analysis reveals that the slope structures of sea surface height are the dynamical driving mechanism of the Pacific-Arctic-Atlantic throughflow and ITF.The analysis denotes,in spite of O（1.4×106m3/s） of the southward volume transport in the northern Atlantic,that there is still O（1 PW） of heat transported northward since the northward currents in the upper layer carry much higher temperature water than the southward flowing northern Atlantic deep water（NADW）.Meridional volume and heat transports are focused on the contributions to NADW renewals and Atlantic meridional overturning circulation（AMOC）.Quantitative descriptions of the interbasin exchanges are explained by meridional compensations and supported by previous observations and numerical modeling results.Analysis indicates that the volume and heat exchanges on the interbasin passages proposed in this article manifest their hub roles in the Great Ocean Conveyor System.展开更多
基金Sponsoredbynationalscientificfund (No .5 0 1 75 0 81 )
文摘With the rapid development of manufacturing technology, the traditional simulation of machining can not meet the people’s need. Research on virtual machining environment is one of the key parts of virtual manufacturing technology. According to the features of virtual turning, this paper proposes a simplified Whitted lighting model based on analysis of Phong and other local illumination model. This model takes the material and roughness of workpiece into account to calculate the roughness coefficient D, geometric fading coefficient G and Fresenel transmission coefficient F’ so that the light intensity in the scene can be got more realisticly. Moreover, to obtain the natural lighting effects, based on the analysis of motion space of machine tools, local ray tracing algorithm is given to calculate the light intensity of every position during the course of simulation. This method can not only simulate the machining environment accurately, but also reduce the calculating time greatly. For example, if CPU is 1.3 G and internal memory is 128 M, the refresh time using the original algorithm is 0.1 second, while it becomes 0.01 seconds by local refreshing. Besides, to get more realistic machining scene, the paper deduce the transfer matrix from chip coordinate to feeding coordinate so that the chip model can be integrated into the whole machining scene. At last, a example of virtual cutting scene is shown to demonstrate the effects of global illumination model and helical chip simulation. The system can give the user high true sensation. The user can operate the machine tools through the controlling panel and watch the cutting process from different viewing angle. The data needed for construction of scene and chip simulation is obtained form the C616 lathe. This study plays important role in richening virtual manufacturing theory and promoting the development of advanced manufacturing technology.
基金The National Basic Research Program Grant of China under contact No.2011CB403502the International Cooperation Program Grant of China under contact No.2010DFB23580+3 种基金the International Cooperation Program of State Oceanic Administration of China under contract No.QY0213022project supported by the First Institute of Oceanographythe State Oceanic Administration of China under contract No.2010G06author Guan Yuping is supported by The National Natural Science Foundation of China under contact Nos 40976011 and 91228202
文摘A global prognostic model based on MOM4p1,which is a primitive equation nonBoussinesq numerical model,has been integrated with 1 400 years from the state of rest based on the realistic topography to study the long-term pattern of combined wind-driven and thermodynamically-driven general circulation.The model is driven by monthly climatological mean forces and includes 192×189 horizontal grids and 31 pressure-based vertical levels.The main objective is to investigate the mass and heat transports at interbasin passages and their compensations and roles in the global ocean circulation under equilibrium state of long-term spin up.The kinetic energy analysis divides the spin up process into three stages：the quasi-stable state of wind driven current,the growing phase of thermodynamical circulation and the equilibrium state of thermohaline circulation.It is essential to spin up over a thousand years in order to reach the thermohaline equilibrium state from a state of rest.The Arctic Throughflow from the Bering Strait to the Greenland Sea and the Indonesian Throughflow（ITF） are captured and examined with their compensations and existing data.Analysis reveals that the slope structures of sea surface height are the dynamical driving mechanism of the Pacific-Arctic-Atlantic throughflow and ITF.The analysis denotes,in spite of O（1.4×106m3/s） of the southward volume transport in the northern Atlantic,that there is still O（1 PW） of heat transported northward since the northward currents in the upper layer carry much higher temperature water than the southward flowing northern Atlantic deep water（NADW）.Meridional volume and heat transports are focused on the contributions to NADW renewals and Atlantic meridional overturning circulation（AMOC）.Quantitative descriptions of the interbasin exchanges are explained by meridional compensations and supported by previous observations and numerical modeling results.Analysis indicates that the volume and heat exchanges on the interbasin passages proposed in this article manifest their hub roles in the Great Ocean Conveyor System.
