1.Products of the basic rawmaterials industry Products of the basic raw materialsindustry should improve product quality,make great efforts to realize diversification,serialization and specialization in productvariety...1.Products of the basic rawmaterials industry Products of the basic raw materialsindustry should improve product quality,make great efforts to realize diversification,serialization and specialization in productvariety,develop new varieties,and expandproduction so as to adapt to the demands forthe development of the food industry. Cereals:Develop high quality riceand wheat flour on a grade and class basis;develop special rice and wheat flour suitablefor the needs of processing various kinds offood;actively utilize coarse cereals such ascorn to open up various kinds of展开更多
China’s auto industry is at a rapid developing stage. In order to solve the problems of "dispersion" and "disorder", realize the scale economy, promote the rationalization of the industry structur...China’s auto industry is at a rapid developing stage. In order to solve the problems of "dispersion" and "disorder", realize the scale economy, promote the rationalization of the industry structure and further enhance the development展开更多
In this paper we derive sufficient conditions for strict convexity of subsets in a complete simply connected smooth Riemanian manifold without focal points in terms of local and global exposed points.
The performance of engineered wood products is highly associated with proper bonding and an efficient cutting method.This paper investigates the influence of CO_(2) laser cutting on the wetting properties,the modified ch...The performance of engineered wood products is highly associated with proper bonding and an efficient cutting method.This paper investigates the influence of CO_(2) laser cutting on the wetting properties,the modified che-mical component of the laser-cut surface,and the strength and adhesive penetration near the bondline.Beech-wood is cut by the laser with varying processing parameters,cutting speeds,gas pressures,and focal point positions.The laser-cut samples were divided into two groups,sanded and non-sanded samples.Polyvinyl acetate adhesive(PVAc)was used to bond the groups of laser-cut samples.After assembly with cold pressing,the tensile shear test was carried out.Numerical modelling was carried out to determine the partial elongation and shear strain of the glue line.Based on this,the shear modulus and linear elasticity of the glue line were estimated.Scan-ning electron microscopy was used to assess the adhesive penetration into the porosity structure of the laser-cut samples,and the depth of the heat-affected zone.The laser-cut surface was analysed by Fourier transform infrared spectroscopy.The wetting properties of the laser-cut surface were investigated by using a contact angle goni-ometer.The numerical model of the strain-stress curve confirmed the experimental model.The highest modulus of the linear elasticity of the glue in the numerical calculation belongs to the joint containing laser-cut samples at a gas pressure of 21(bar).The penetration depth of PVAc adhesive into the porosity structure of the laser-cut sam-ples was similar to that of sawn samples.The deepest heat-affected zone in the laser-cut samples was 150µm.A PVAc drop disappeared immediately on the laser-cut surface without sanding,but gradually on the sanded surface.In contrast,the drop on the sawn surface remained with an angle of 32°–48°.The degradation of hemi-cellulose and lignin was proven by the lower intensity of the C=O and C-O Bonds,compared to the sawn surface.展开更多
Transmission matrix(TM)is an important tool for controlling light focusing,imaging,and communication through turbid media.It can be measured by 3-step(TM3)or 4-step(TM4)phase-shifting interference,but the similarities...Transmission matrix(TM)is an important tool for controlling light focusing,imaging,and communication through turbid media.It can be measured by 3-step(TM3)or 4-step(TM4)phase-shifting interference,but the similarities and differences of the transmission matrices obtained by the two methods are rarely reported.Therefore,we make a quantitative comparison of the peak light intensity,signal-to-noise ratio,and average background of 24×24=576 focal points between paired samples(TM3-TM4)through the Wilcoxon rank sum test,and discuss the singular value of the transmission matrix and the focal peak.The comparative results of peak light intensity and signal-to-noise ratio show that there is a significant difference between the 3-step phase shift and the 4-step phase shift transmission matrixes.The focusing effect of the former is significantly better than that of the latter;interest concentrates on the focal intensity and singular value.The reciprocal of the singular value is proportional to the squared intensity,which is in accordance with singular value theory.The results of comparison of peak light intensity and signal-to-noise ratio strongly suggest that 3-step phase shift should be selected and used in applying the phase shift method to the measurement of the transmission matrix;and the singular value is of great significance in quantifying the focusing,imaging,and communication quality of the transmission matrix.展开更多
A dish/stifling solar thermal electricity system consists of two parts： a dish solar concentrator and a Stifling engine. For optimizing the system, in this paper, the mathematical model for concentrator design was es...A dish/stifling solar thermal electricity system consists of two parts： a dish solar concentrator and a Stifling engine. For optimizing the system, in this paper, the mathematical model for concentrator design was established and the effects of those design parameters of concentrator, such as the size and intensity of the focal point, the receiver temperature, on the efficiency of the Stifling engine and output power were numerically simulated. The results of the simulation revealed a close relationship between power and efficiency because of power losses, and there was a maximum for the engine efficiency and power with increasing solar radiation because there was a peak value of system efficiency with increasing receiver temperature. So, in view of our Stifling engine, the 450 rim angle and 6m focal length are optimal design for concentrator and the 800℃receiver temperature is best.展开更多
We prove that there are only finitely many diffeomorphism types of curvature-adapted equifocal hypersurfaces in a simply connected compact symmetric space.Moreover,if the symmetric space is of rank one,the result can ...We prove that there are only finitely many diffeomorphism types of curvature-adapted equifocal hypersurfaces in a simply connected compact symmetric space.Moreover,if the symmetric space is of rank one,the result can be strengthened by dropping the condition curvature-adapted.展开更多
Theoretical analysis of the electromagnetic field distribution in the focal region of a long metallic parabolic reflector that has its surface covered with a magnetized plasma layer is derived. The incident wave is co...Theoretical analysis of the electromagnetic field distribution in the focal region of a long metallic parabolic reflector that has its surface covered with a magnetized plasma layer is derived. The incident wave is considered to be with a general oblique incidence for both parallel and perpendicular polarizations. The electromagnetic field intensity expressions along the focal region are obtained accurately using Maslov＇s method. The effects of plasma thickness on the reflected and transmitted field distributions are investigated. The effects of other physi- cal parameters such as the angle of incidence and the plasma and cyclotron frequencies on the transmitted field- intensity distribution along the focal region are also studied. The results obtained by Maslov＇s method and Kirchhoff＇s approximation are found to be in a good agreement.展开更多
Metasurfaces,which are the two-dimensional counterparts of metamaterials,have demonstrated unprecedented capabilities to manipulate the wavefront of electromagnetic waves in a single flat device.Despite various advanc...Metasurfaces,which are the two-dimensional counterparts of metamaterials,have demonstrated unprecedented capabilities to manipulate the wavefront of electromagnetic waves in a single flat device.Despite various advances in this field,the unique functionalities achieved by metasurfaces have come at the cost of the structural complexity,resulting in a time-consuming parameter sweep for the conventional metasurface design.Although artificial neural networks provide a flexible platform for significantly improving the design process,the current metasurface designs are restricted to generating qualitative field distributions.In this study,we demonstrate that by combining a tandem neural network and an iterative algorithm,the previous restriction of the design of metasurfaces can be overcome with quantitative field distributions.As proof-of-principle examples,metalenses predicted via the designed network architecture that possess multiple focal points with identical/orthogonal polarisation states,as well as accurate intensity ratios(quantitative field distributions),were numerically calculated and experimentally demonstrated.The unique and robust approach for the metasurface design will enable the acceleration of the development of devices with high-accuracy functionalities,which can be applied in imaging,detecting,and sensing.展开更多
文摘1.Products of the basic rawmaterials industry Products of the basic raw materialsindustry should improve product quality,make great efforts to realize diversification,serialization and specialization in productvariety,develop new varieties,and expandproduction so as to adapt to the demands forthe development of the food industry. Cereals:Develop high quality riceand wheat flour on a grade and class basis;develop special rice and wheat flour suitablefor the needs of processing various kinds offood;actively utilize coarse cereals such ascorn to open up various kinds of
文摘China’s auto industry is at a rapid developing stage. In order to solve the problems of "dispersion" and "disorder", realize the scale economy, promote the rationalization of the industry structure and further enhance the development
文摘In this paper we derive sufficient conditions for strict convexity of subsets in a complete simply connected smooth Riemanian manifold without focal points in terms of local and global exposed points.
文摘The performance of engineered wood products is highly associated with proper bonding and an efficient cutting method.This paper investigates the influence of CO_(2) laser cutting on the wetting properties,the modified che-mical component of the laser-cut surface,and the strength and adhesive penetration near the bondline.Beech-wood is cut by the laser with varying processing parameters,cutting speeds,gas pressures,and focal point positions.The laser-cut samples were divided into two groups,sanded and non-sanded samples.Polyvinyl acetate adhesive(PVAc)was used to bond the groups of laser-cut samples.After assembly with cold pressing,the tensile shear test was carried out.Numerical modelling was carried out to determine the partial elongation and shear strain of the glue line.Based on this,the shear modulus and linear elasticity of the glue line were estimated.Scan-ning electron microscopy was used to assess the adhesive penetration into the porosity structure of the laser-cut samples,and the depth of the heat-affected zone.The laser-cut surface was analysed by Fourier transform infrared spectroscopy.The wetting properties of the laser-cut surface were investigated by using a contact angle goni-ometer.The numerical model of the strain-stress curve confirmed the experimental model.The highest modulus of the linear elasticity of the glue in the numerical calculation belongs to the joint containing laser-cut samples at a gas pressure of 21(bar).The penetration depth of PVAc adhesive into the porosity structure of the laser-cut sam-ples was similar to that of sawn samples.The deepest heat-affected zone in the laser-cut samples was 150µm.A PVAc drop disappeared immediately on the laser-cut surface without sanding,but gradually on the sanded surface.In contrast,the drop on the sawn surface remained with an angle of 32°–48°.The degradation of hemi-cellulose and lignin was proven by the lower intensity of the C=O and C-O Bonds,compared to the sawn surface.
文摘Transmission matrix(TM)is an important tool for controlling light focusing,imaging,and communication through turbid media.It can be measured by 3-step(TM3)or 4-step(TM4)phase-shifting interference,but the similarities and differences of the transmission matrices obtained by the two methods are rarely reported.Therefore,we make a quantitative comparison of the peak light intensity,signal-to-noise ratio,and average background of 24×24=576 focal points between paired samples(TM3-TM4)through the Wilcoxon rank sum test,and discuss the singular value of the transmission matrix and the focal peak.The comparative results of peak light intensity and signal-to-noise ratio show that there is a significant difference between the 3-step phase shift and the 4-step phase shift transmission matrixes.The focusing effect of the former is significantly better than that of the latter;interest concentrates on the focal intensity and singular value.The reciprocal of the singular value is proportional to the squared intensity,which is in accordance with singular value theory.The results of comparison of peak light intensity and signal-to-noise ratio strongly suggest that 3-step phase shift should be selected and used in applying the phase shift method to the measurement of the transmission matrix;and the singular value is of great significance in quantifying the focusing,imaging,and communication quality of the transmission matrix.
文摘A dish/stifling solar thermal electricity system consists of two parts： a dish solar concentrator and a Stifling engine. For optimizing the system, in this paper, the mathematical model for concentrator design was established and the effects of those design parameters of concentrator, such as the size and intensity of the focal point, the receiver temperature, on the efficiency of the Stifling engine and output power were numerically simulated. The results of the simulation revealed a close relationship between power and efficiency because of power losses, and there was a maximum for the engine efficiency and power with increasing solar radiation because there was a peak value of system efficiency with increasing receiver temperature. So, in view of our Stifling engine, the 450 rim angle and 6m focal length are optimal design for concentrator and the 800℃receiver temperature is best.
基金supported by National Natural Science Foundation of China(Grant Nos.11071018 and 11001016)the Specialized Research Fund for Doctoral Program of Higher Education(Grant No.20100003120003)the Program for Changjiang Scholars and Innovative Research Team in University
文摘We prove that there are only finitely many diffeomorphism types of curvature-adapted equifocal hypersurfaces in a simply connected compact symmetric space.Moreover,if the symmetric space is of rank one,the result can be strengthened by dropping the condition curvature-adapted.
基金the Deanship of Scientific Research at King Saud University for its funding of this work through the Research Group Project No. RG-1436-001
文摘Theoretical analysis of the electromagnetic field distribution in the focal region of a long metallic parabolic reflector that has its surface covered with a magnetized plasma layer is derived. The incident wave is considered to be with a general oblique incidence for both parallel and perpendicular polarizations. The electromagnetic field intensity expressions along the focal region are obtained accurately using Maslov＇s method. The effects of plasma thickness on the reflected and transmitted field distributions are investigated. The effects of other physi- cal parameters such as the angle of incidence and the plasma and cyclotron frequencies on the transmitted field- intensity distribution along the focal region are also studied. The results obtained by Maslov＇s method and Kirchhoff＇s approximation are found to be in a good agreement.
基金the National Key Research and Development Program of China(2017YFA0701005)National Natural Science Foundation of China(62271320,61871268)+1 种基金“Shuguang”Program of Shanghai Education Commission(19SG44)the 111 Project(D18014).
文摘Metasurfaces,which are the two-dimensional counterparts of metamaterials,have demonstrated unprecedented capabilities to manipulate the wavefront of electromagnetic waves in a single flat device.Despite various advances in this field,the unique functionalities achieved by metasurfaces have come at the cost of the structural complexity,resulting in a time-consuming parameter sweep for the conventional metasurface design.Although artificial neural networks provide a flexible platform for significantly improving the design process,the current metasurface designs are restricted to generating qualitative field distributions.In this study,we demonstrate that by combining a tandem neural network and an iterative algorithm,the previous restriction of the design of metasurfaces can be overcome with quantitative field distributions.As proof-of-principle examples,metalenses predicted via the designed network architecture that possess multiple focal points with identical/orthogonal polarisation states,as well as accurate intensity ratios(quantitative field distributions),were numerically calculated and experimentally demonstrated.The unique and robust approach for the metasurface design will enable the acceleration of the development of devices with high-accuracy functionalities,which can be applied in imaging,detecting,and sensing.
