Generally, FD coefficients can be obtained by using Taylor series expansion （TE） or optimization methods to minimize the dispersion error. However, the TE-based FD method only achieves high modeling precision over a...Generally, FD coefficients can be obtained by using Taylor series expansion （TE） or optimization methods to minimize the dispersion error. However, the TE-based FD method only achieves high modeling precision over a limited range of wavenumbers, and produces large numerical dispersion beyond this range. The optimal FD scheme based on least squares （LS） can guarantee high precision over a larger range of wavenumbers and obtain the best optimization solution at small computational cost. We extend the LS-based optimal FD scheme from two-dimensional （2D） forward modeling to three-dimensional （3D） and develop a 3D acoustic optimal FD method with high efficiency, wide range of high accuracy and adaptability to parallel computing. Dispersion analysis and forward modeling demonstrate that the developed FD method suppresses numerical dispersion. Finally, we use the developed FD method to source wavefield extrapolation and receiver wavefield extrapolation in 3D RTM. To decrease the computation time and storage requirements, the 3D RTM is implemented by combining the efficient boundary storage with checkpointing strategies on GPU. 3D RTM imaging results suggest that the 3D optimal FD method has higher precision than conventional methods.展开更多
The general layout of 6th generation semi-submersible drilling platforms is the main factor impacting the efficiency of their drilling operations. This paper provides a compound/integrated algorithm based on process f...The general layout of 6th generation semi-submersible drilling platforms is the main factor impacting the efficiency of their drilling operations. This paper provides a compound/integrated algorithm based on process flow that is aimed at improving efficiency, while giving attention to stability and safety at the same time. The paper describes the process flow of dual drilling centers and a hierarchical division of rigs based on the different modes of transportation of various drilling support systems. The general layout-centripetal overall arrangement spatially was determined based on drilling efficiency. We derived our modules according to drilling functionality; the modules became our basic layout units. We applied different layout algorithm to mark out the upper and lower decks. That is, the upper deck was designed based on the lowest transportation cost while the lower deck＇s calculations were based on the best-fit scope. Storage configurations in columns and pontoons were also considered for the layout design. Finally the center of gravity was taken into consideration and the general layout was adjusted accordingly, to result in an optimal center of gravity. The methodology of the general layout can provide a reference for implementation of domestic designs of semi-submersible rigs.展开更多
The tidal current duration （TCD） and velocity （TCV） and suspended sediment concentration （SSC） were measured in the dry season in December, 2011 and in the flood season in June, 2012 at the upper part of the Nor...The tidal current duration （TCD） and velocity （TCV） and suspended sediment concentration （SSC） were measured in the dry season in December, 2011 and in the flood season in June, 2012 at the upper part of the North Channel of Changjiang Estuary. They were assimilated with the measured data in 2003, 2004, 2006 and 2007, using the tidal range＇s proportion conversion. Variations in TCD and TCV, preferential flow and SSC have been calculated. Influences of typical engineering projects such as Qingcaosha fresh water reservoir, Yangtze River Bridge, and land reclamation on the ebb and flood TCD, TCV and SSC in the North Channel for the last 10 years are discussed. The results show that： （1） currently, in the upper part of North Channel, the ebb tide dominates; after the construction of the typical projects, ebb TCD and TCV tends to be larger and the vertical average ebb and flood SSC decrease during the flood season while SSC increases during the dry season; （2） changes in the vertical average TCV are mainly contributed by seasonal runoff variation during the flood season, which is larger in the flood season than that in the dry season; the controlling parameters of increasing ebb TCD and TCV are those large-scale engineering projects in the North Channel; variation in SSC may result mainly from the reduction of basin annual sediment loads, large-scale nearshore projects and so on.展开更多
To simplify the complicated design process of deployable/retractable structures, a new design process is developed. The process is divided into three phases： the concept design phase, the model phase and the optimiza...To simplify the complicated design process of deployable/retractable structures, a new design process is developed. The process is divided into three phases： the concept design phase, the model phase and the optimization phase. In each phase, different parameter targets have to be fulfilled. According to three phases, a deployable/retractable mast composed of four right triangle prism modules in the longitudinal direction is designed. It can be deployed and folded simultaneously by the linear movements of sleeve-joints. The deployable and retractable movement of the mast is analyzed and key joint forms are designed. Then bar diameters and joint forms are modified based on mast structural mechanics characteristics in the optimization phase. Finally a 1：1 scaled model mast is built to verify the design and the optimization. Analytical results show that the model mast has the advantages of simple locking mechanism, fewer types of joints and bars, so it can be easily manufactured.展开更多
[Objective] This study aimed to optimize the chromatographic conditions for detecting ellagic acid in pomegranate peels using HPLC method. [Method] By using 0.2 mg/ml ellagic acid standard solution, on the basis of si...[Objective] This study aimed to optimize the chromatographic conditions for detecting ellagic acid in pomegranate peels using HPLC method. [Method] By using 0.2 mg/ml ellagic acid standard solution, on the basis of single-factor experiment and orthogonal experiment, chromatographic conditions （mobile phase ratio, flow rate, col- umn temperature） for detecting ellagic acid using HPLC were optimized. Based on the optimal chromatographic conditions, the ellagic acid content in experimental pomegranate peels was determined. [Resull] The optimal chromatographic conditions for detecting ellagic acid in pomegranate peels using HPLC method are： 1.2% phos- phoric acid：acetonitrile=85：15, column temperature of 35 ℃, and flow rate of 1.0 ml/min. The linear regression equation of ellagic acid is： y=2.9e＋0.6x＋4.4e＋5 （FF=9 999）. Ac- cording to the standard addition recovery test, the average recovery rate of ellagic acid is 98.20%, and RSD is 0.60%. Under above optimized chromatographic condi- tions, ellagic acid can be well separated from other interfering components in pomegranate peels, with shorter peak time and ideal effect, which is convenient for the detection in production practices. [Conclusion] This study laid the foundation for detecting ellagic acid in pomegranate peels using HPLC method.展开更多
Step channel direct injection(SCDI)flash memory device which had been developed changes the hot carrier injection method by making a shallow step in the middle of channel .Therefore high speed for programming,hig...Step channel direct injection(SCDI)flash memory device which had been developed changes the hot carrier injection method by making a shallow step in the middle of channel .Therefore high speed for programming,high efficiency for injection,and lower working voltage are obtained.Simulation and analysis for the proposed SCDI structure device are done and an optimization scheme to improve the utmost performance of SCDI device is given...展开更多
Step channel direct injection(SCDI) flash memory device is successfully achieved by 1 2μm CMOS technology,moreover good performance is obtained.At the bias condition of V g=6V, V d=5V,the programming speed ...Step channel direct injection(SCDI) flash memory device is successfully achieved by 1 2μm CMOS technology,moreover good performance is obtained.At the bias condition of V g=6V, V d=5V,the programming speed of SCDI device is 42μs.Under the condition of V g=-8V, V s=8V,the erasing speed is 24ms.Compared with the same size of conventional flash memory device whose corresponding parameters are 500μs and 24ms,respectively,the performance of SCDI device is remarkably improved.During manufacturing of SCDI device,the key technologies are to make the shallow step with appropriate depth and angle,along with eliminating the etch damage during the process of Si 3N 4 spacer.展开更多
基金supported by the National Natural Science Foundation of China(No.41474110)Shell Ph.D. Scholarship to support excellence in geophysical research
文摘Generally, FD coefficients can be obtained by using Taylor series expansion （TE） or optimization methods to minimize the dispersion error. However, the TE-based FD method only achieves high modeling precision over a limited range of wavenumbers, and produces large numerical dispersion beyond this range. The optimal FD scheme based on least squares （LS） can guarantee high precision over a larger range of wavenumbers and obtain the best optimization solution at small computational cost. We extend the LS-based optimal FD scheme from two-dimensional （2D） forward modeling to three-dimensional （3D） and develop a 3D acoustic optimal FD method with high efficiency, wide range of high accuracy and adaptability to parallel computing. Dispersion analysis and forward modeling demonstrate that the developed FD method suppresses numerical dispersion. Finally, we use the developed FD method to source wavefield extrapolation and receiver wavefield extrapolation in 3D RTM. To decrease the computation time and storage requirements, the 3D RTM is implemented by combining the efficient boundary storage with checkpointing strategies on GPU. 3D RTM imaging results suggest that the 3D optimal FD method has higher precision than conventional methods.
基金Supported by the National High Technology Research and Development Program of China (863 Program) under Grant No.2006AA09A104
文摘The general layout of 6th generation semi-submersible drilling platforms is the main factor impacting the efficiency of their drilling operations. This paper provides a compound/integrated algorithm based on process flow that is aimed at improving efficiency, while giving attention to stability and safety at the same time. The paper describes the process flow of dual drilling centers and a hierarchical division of rigs based on the different modes of transportation of various drilling support systems. The general layout-centripetal overall arrangement spatially was determined based on drilling efficiency. We derived our modules according to drilling functionality; the modules became our basic layout units. We applied different layout algorithm to mark out the upper and lower decks. That is, the upper deck was designed based on the lowest transportation cost while the lower deck＇s calculations were based on the best-fit scope. Storage configurations in columns and pontoons were also considered for the layout design. Finally the center of gravity was taken into consideration and the general layout was adjusted accordingly, to result in an optimal center of gravity. The methodology of the general layout can provide a reference for implementation of domestic designs of semi-submersible rigs.
文摘The tidal current duration （TCD） and velocity （TCV） and suspended sediment concentration （SSC） were measured in the dry season in December, 2011 and in the flood season in June, 2012 at the upper part of the North Channel of Changjiang Estuary. They were assimilated with the measured data in 2003, 2004, 2006 and 2007, using the tidal range＇s proportion conversion. Variations in TCD and TCV, preferential flow and SSC have been calculated. Influences of typical engineering projects such as Qingcaosha fresh water reservoir, Yangtze River Bridge, and land reclamation on the ebb and flood TCD, TCV and SSC in the North Channel for the last 10 years are discussed. The results show that： （1） currently, in the upper part of North Channel, the ebb tide dominates; after the construction of the typical projects, ebb TCD and TCV tends to be larger and the vertical average ebb and flood SSC decrease during the flood season while SSC increases during the dry season; （2） changes in the vertical average TCV are mainly contributed by seasonal runoff variation during the flood season, which is larger in the flood season than that in the dry season; the controlling parameters of increasing ebb TCD and TCV are those large-scale engineering projects in the North Channel; variation in SSC may result mainly from the reduction of basin annual sediment loads, large-scale nearshore projects and so on.
文摘To simplify the complicated design process of deployable/retractable structures, a new design process is developed. The process is divided into three phases： the concept design phase, the model phase and the optimization phase. In each phase, different parameter targets have to be fulfilled. According to three phases, a deployable/retractable mast composed of four right triangle prism modules in the longitudinal direction is designed. It can be deployed and folded simultaneously by the linear movements of sleeve-joints. The deployable and retractable movement of the mast is analyzed and key joint forms are designed. Then bar diameters and joint forms are modified based on mast structural mechanics characteristics in the optimization phase. Finally a 1：1 scaled model mast is built to verify the design and the optimization. Analytical results show that the model mast has the advantages of simple locking mechanism, fewer types of joints and bars, so it can be easily manufactured.
文摘[Objective] This study aimed to optimize the chromatographic conditions for detecting ellagic acid in pomegranate peels using HPLC method. [Method] By using 0.2 mg/ml ellagic acid standard solution, on the basis of single-factor experiment and orthogonal experiment, chromatographic conditions （mobile phase ratio, flow rate, col- umn temperature） for detecting ellagic acid using HPLC were optimized. Based on the optimal chromatographic conditions, the ellagic acid content in experimental pomegranate peels was determined. [Resull] The optimal chromatographic conditions for detecting ellagic acid in pomegranate peels using HPLC method are： 1.2% phos- phoric acid：acetonitrile=85：15, column temperature of 35 ℃, and flow rate of 1.0 ml/min. The linear regression equation of ellagic acid is： y=2.9e＋0.6x＋4.4e＋5 （FF=9 999）. Ac- cording to the standard addition recovery test, the average recovery rate of ellagic acid is 98.20%, and RSD is 0.60%. Under above optimized chromatographic condi- tions, ellagic acid can be well separated from other interfering components in pomegranate peels, with shorter peak time and ideal effect, which is convenient for the detection in production practices. [Conclusion] This study laid the foundation for detecting ellagic acid in pomegranate peels using HPLC method.
文摘Step channel direct injection(SCDI)flash memory device which had been developed changes the hot carrier injection method by making a shallow step in the middle of channel .Therefore high speed for programming,high efficiency for injection,and lower working voltage are obtained.Simulation and analysis for the proposed SCDI structure device are done and an optimization scheme to improve the utmost performance of SCDI device is given...
文摘Step channel direct injection(SCDI) flash memory device is successfully achieved by 1 2μm CMOS technology,moreover good performance is obtained.At the bias condition of V g=6V, V d=5V,the programming speed of SCDI device is 42μs.Under the condition of V g=-8V, V s=8V,the erasing speed is 24ms.Compared with the same size of conventional flash memory device whose corresponding parameters are 500μs and 24ms,respectively,the performance of SCDI device is remarkably improved.During manufacturing of SCDI device,the key technologies are to make the shallow step with appropriate depth and angle,along with eliminating the etch damage during the process of Si 3N 4 spacer.
