To solve the defects of bottom concave appearing in the extrusion experiments of complex hollow aluminium profiles,a 3D finite element model for simulating steady-state porthole die extrusion process was established b...To solve the defects of bottom concave appearing in the extrusion experiments of complex hollow aluminium profiles,a 3D finite element model for simulating steady-state porthole die extrusion process was established based on HyperXtrude software using Arbitrary Lagrangian–Eulerian(ALE)algorithm.The velocity distribution on the cross-section of the extrudate at the die exit and pressure distribution at different heights in the welding chamber were quantitatively analyzed.To obtain an uniformity of metal flow velocity at the die exit,the porthole die structure was optimized by adding baffle plates.After optimization,maximum displacement in the Y direction at the bottom of profile decreases from 1.1 to 0.15 mm,and the concave defects are remarkably improved.The research method provides an effective guidance for improving extrusion defects and optimizing the metal flow of complex hollow aluminium profiles during porthole die extrusion.展开更多
Due to coarse quantization, block-based discrete cosine transform(BDCT) compression methods usually suffer from visible blocking artifacts at the block boundaries. A novel efficient de-blocking method in DCT domain is...Due to coarse quantization, block-based discrete cosine transform(BDCT) compression methods usually suffer from visible blocking artifacts at the block boundaries. A novel efficient de-blocking method in DCT domain is proposed. A specific criterion for edge detection is given, one-dimensional DCT is applied on each row of the adjacent blocks and the shifted block in smooth region, and the transform coefficients of the shifted block are modified by weighting the average of three coefficients of the block. Mean square difference of slope criterion is used to judge the efficiency of the proposed algorithm. Simulation results show that the new method not only obtains satisfactory image quality, but also maintains high frequency information.展开更多
The most important objective of blasting in open pit mines is rock fragmentation.Prediction of produced boulders(oversized crushed rocks) is a key parameter in designing blast patterns.In this study,the amount of boul...The most important objective of blasting in open pit mines is rock fragmentation.Prediction of produced boulders(oversized crushed rocks) is a key parameter in designing blast patterns.In this study,the amount of boulder produced in blasting operations of Golegohar iron ore open pit mine,Iran was predicted via multiple regression method and artificial neural networks.Results of 33 blasts in the mine were collected for modeling.Input variables were:joints spacing,density and uniaxial compressive strength of the intact rock,burden,spacing,stemming,bench height to burden ratio,and specific charge.The dependent variable was ratio of boulder volume to pattern volume.Both techniques were successful in predicting the ratio.In this study,the multiple regression method was superior with coefficient of determination and root mean squared error values of 0.89 and 0.19,respectively.展开更多
The regional stress field and seismic dynamics along the border zone between Fujian, Guangdong and Jiangxi Provinces are studied based on the seismo-geological data,GPS measurement, and seismicity. The results show th...The regional stress field and seismic dynamics along the border zone between Fujian, Guangdong and Jiangxi Provinces are studied based on the seismo-geological data,GPS measurement, and seismicity. The results show that: (1) the principal compressional stress of the stress field is oriented in NW-SE direction and the principal extensional stress is in NE-SW direction; (2) the WNW-ward compression and collision of the Philippine Sea Plate to the eastern coast of Taiwan Island are the most direct and most important dynamic source for preparation and occurrence of strong earthquakes in the Taiwan Region and along the border zone between Fujian, Guangdong and Jiangxi Provinces.展开更多
In order to model the hysteresis behavior of a nano piezoelectric actuator(PA)on nano scale in a real time system,a new hysteresis modeling method based on an improved sub-pixel blocking matching algorithm with an opt...In order to model the hysteresis behavior of a nano piezoelectric actuator(PA)on nano scale in a real time system,a new hysteresis modeling method based on an improved sub-pixel blocking matching algorithm with an optimal block size is proposed in this paper.First,Preisach model is introduced to model the hysteresis behavior of a piezoelectric actuator.Then,a real time block matching algorithm is researched and its block size is optimized with a standard object.Finally,experiments are performed with respect to a nanometer movement platform system,and the results show the feasibility and validity of the sub-pixel estimation based block matching algorithm and its application in modeling the hysteresis behavior of PA.展开更多
基金Project(U1664252) supported by the National Natural Science Foundation of ChinaProjects(31665004,31715011) supported by the Open Fund of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body,China
文摘To solve the defects of bottom concave appearing in the extrusion experiments of complex hollow aluminium profiles,a 3D finite element model for simulating steady-state porthole die extrusion process was established based on HyperXtrude software using Arbitrary Lagrangian–Eulerian(ALE)algorithm.The velocity distribution on the cross-section of the extrudate at the die exit and pressure distribution at different heights in the welding chamber were quantitatively analyzed.To obtain an uniformity of metal flow velocity at the die exit,the porthole die structure was optimized by adding baffle plates.After optimization,maximum displacement in the Y direction at the bottom of profile decreases from 1.1 to 0.15 mm,and the concave defects are remarkably improved.The research method provides an effective guidance for improving extrusion defects and optimizing the metal flow of complex hollow aluminium profiles during porthole die extrusion.
基金Science and Technology Project of Guangdong Province(2006A10201003) 2005 Jinan University StartupProject(51205067) Soft Science Project of Guangdong Province(2006B70103011)
文摘Due to coarse quantization, block-based discrete cosine transform(BDCT) compression methods usually suffer from visible blocking artifacts at the block boundaries. A novel efficient de-blocking method in DCT domain is proposed. A specific criterion for edge detection is given, one-dimensional DCT is applied on each row of the adjacent blocks and the shifted block in smooth region, and the transform coefficients of the shifted block are modified by weighting the average of three coefficients of the block. Mean square difference of slope criterion is used to judge the efficiency of the proposed algorithm. Simulation results show that the new method not only obtains satisfactory image quality, but also maintains high frequency information.
文摘The most important objective of blasting in open pit mines is rock fragmentation.Prediction of produced boulders(oversized crushed rocks) is a key parameter in designing blast patterns.In this study,the amount of boulder produced in blasting operations of Golegohar iron ore open pit mine,Iran was predicted via multiple regression method and artificial neural networks.Results of 33 blasts in the mine were collected for modeling.Input variables were:joints spacing,density and uniaxial compressive strength of the intact rock,burden,spacing,stemming,bench height to burden ratio,and specific charge.The dependent variable was ratio of boulder volume to pattern volume.Both techniques were successful in predicting the ratio.In this study,the multiple regression method was superior with coefficient of determination and root mean squared error values of 0.89 and 0.19,respectively.
文摘The regional stress field and seismic dynamics along the border zone between Fujian, Guangdong and Jiangxi Provinces are studied based on the seismo-geological data,GPS measurement, and seismicity. The results show that: (1) the principal compressional stress of the stress field is oriented in NW-SE direction and the principal extensional stress is in NE-SW direction; (2) the WNW-ward compression and collision of the Philippine Sea Plate to the eastern coast of Taiwan Island are the most direct and most important dynamic source for preparation and occurrence of strong earthquakes in the Taiwan Region and along the border zone between Fujian, Guangdong and Jiangxi Provinces.
基金supported by the National Natural Science Foundation of China(Grant No.61305025)
文摘In order to model the hysteresis behavior of a nano piezoelectric actuator(PA)on nano scale in a real time system,a new hysteresis modeling method based on an improved sub-pixel blocking matching algorithm with an optimal block size is proposed in this paper.First,Preisach model is introduced to model the hysteresis behavior of a piezoelectric actuator.Then,a real time block matching algorithm is researched and its block size is optimized with a standard object.Finally,experiments are performed with respect to a nanometer movement platform system,and the results show the feasibility and validity of the sub-pixel estimation based block matching algorithm and its application in modeling the hysteresis behavior of PA.
