The key-value store can provide flexibility of data types because it does not need to specify the data types to be stored in advance and can store any types of data as the value of the key-value pair.Various types of ...The key-value store can provide flexibility of data types because it does not need to specify the data types to be stored in advance and can store any types of data as the value of the key-value pair.Various types of studies have been conducted to improve the performance of the key-value store while maintaining its flexibility.However,the research efforts storing the large-scale values such as multimedia data files(e.g.,images or videos)in the key-value store were limited.In this study,we propose a new key-value store,WR-Store++aiming to store the large-scale values stably.Specifically,it provides a new design of separating data and index by working with the built-in data structure of the Windows operating system and the file system.The utilization of the built-in data structure of the Windows operating system achieves the efficiency of the key-value store and that of the file system extends the limited space of the storage significantly.We also present chunk-based memory management and parallel processing of WR-Store++to further improve its performance in the GET operation.Through the experiments,we show that WR-Store++can store at least 32.74 times larger datasets than the existing baseline key-value store,WR-Store,which has the limitation in storing large-scale data sets.Furthermore,in terms of processing efficiency,we show that WR-Store++outperforms not only WR-Store but also the other state-ofthe-art key-value stores,LevelDB,RocksDB,and BerkeleyDB,for individual key-value operations and mixed workloads.展开更多
We propose a novel high performance carrier stored trench bipolar transistor(CSTBT)with dual shielding structure(DSS-CSTBT).The proposed DSS-CSTBT features a double trench structure with different trench profiles in t...We propose a novel high performance carrier stored trench bipolar transistor(CSTBT)with dual shielding structure(DSS-CSTBT).The proposed DSS-CSTBT features a double trench structure with different trench profiles in the surface,in which a shallow gate trench is shielded by a deep emitter trench and a thick oxide layer under it.Compared with the conventional CSTBT(con-CSTBT),the proposed DSS-CSTBT not only alleviates the negative impact of the shallow gate trench and highly doped CS layer on the breakdown voltage(BV),but also well reduces the gate-collector capacitance CGC,gate charge Q_(G),and turn-off loss E_(OFF)of the device.Furthermore,lower turn-on loss E_(ON)and gate drive loss E_(DR)are also obtained.Simulation results show that with the same CS layer doping concentration N_(CS)=1.5×10^(16)cm^(-3),the BV increases from 1312 V of the con-CSTBT to 1423 V of the proposed DSS-CSTBT with oxide layer thickness under gate(T_(og2))of 1μm.Moreover,compared with the con-CSTBT,the C_(GC)at V_(CE)of 25 V and miller plateau charge(Q_(GC))for the proposed DSS-CSTBT with T_(og2)of 1μm are reduced by 79.4%and 74.3%,respectively.With the VGEincreases from 0 V to 15 V,the total QGfor the proposed DSS-CSTBT with T_(og2)of 1μm is reduced by 49.5%.As a result,at the same on-state voltage drop(V_(CEON))of 1.55 V,the E_(ON)and E_(OFF)are reduced from 20.3 mJ/cm^(2)and 19.3 mJ/cm^(2)for the con-CSTBT to8.2 mJ/cm^(2)and 9.7 mJ/cm^(2)for the proposed DSS-CSTBT with T_(og2)of 1μm,respectively.The proposed DSS-CSTBT not only significantly improves the trade-off relationship between the V_(CEON)and E_(OFF)but also greatly reduces the E_(ON).展开更多
The urban grass-roots library is an important part of the public cultural service system,and also a place to carry out national reading and lifelong learning,which is of great significance to the construction of a lea...The urban grass-roots library is an important part of the public cultural service system,and also a place to carry out national reading and lifelong learning,which is of great significance to the construction of a learning society.In this paper,the development and evolution of urban grassroots libraries in China are reviewed,and the current situation and usage issues of grassroots libraries in Beijing are analyzed.Moreover,the development strategy of idea stores in London,UK is studied,and characteristics are summarized,and possible references are sought.In the new era,urban grassroots libraries should integrate into communities with multiple functions and play a more sufficient role in public education,learning and training,and other aspects.展开更多
To understand the influence of the initial release conditions on the separation characteristics of the store and improve it under high Mach number(Ma=4)flight conditions,the overset grid method and the Realizable k−ε...To understand the influence of the initial release conditions on the separation characteristics of the store and improve it under high Mach number(Ma=4)flight conditions,the overset grid method and the Realizable k−εturbulence model coupled with an equation with six degrees of freedom are used to simulate the store released from the internal bay.The motion trajectory and the attitude angle of the store separation under the conditions of different centroid,velocity,height and control measures are given by the calculated result.Through analysis,the position of the centroid will affect the separation of the store,which needs to be considered in the design.Increasing the launching height is conducive to the separation of the store.If the store has an initial velocity,it can leave the internal bay more quickly and reduce the probability of collision with the wall.Cylindrical rod and slanted aft wall control measures can improve the attitude of the store and make the store fall more smoothly.展开更多
文摘The key-value store can provide flexibility of data types because it does not need to specify the data types to be stored in advance and can store any types of data as the value of the key-value pair.Various types of studies have been conducted to improve the performance of the key-value store while maintaining its flexibility.However,the research efforts storing the large-scale values such as multimedia data files(e.g.,images or videos)in the key-value store were limited.In this study,we propose a new key-value store,WR-Store++aiming to store the large-scale values stably.Specifically,it provides a new design of separating data and index by working with the built-in data structure of the Windows operating system and the file system.The utilization of the built-in data structure of the Windows operating system achieves the efficiency of the key-value store and that of the file system extends the limited space of the storage significantly.We also present chunk-based memory management and parallel processing of WR-Store++to further improve its performance in the GET operation.Through the experiments,we show that WR-Store++can store at least 32.74 times larger datasets than the existing baseline key-value store,WR-Store,which has the limitation in storing large-scale data sets.Furthermore,in terms of processing efficiency,we show that WR-Store++outperforms not only WR-Store but also the other state-ofthe-art key-value stores,LevelDB,RocksDB,and BerkeleyDB,for individual key-value operations and mixed workloads.
基金the National Key Research and Development Program of China(Grant No.2018YFB1201802)the Key Realm R&D Program of Guangdong Province,China(Grant No.2018B010142001)the Guangdong Basic and Applied Basic Research Foundation,China(Grant No.2020A1515010128).
文摘We propose a novel high performance carrier stored trench bipolar transistor(CSTBT)with dual shielding structure(DSS-CSTBT).The proposed DSS-CSTBT features a double trench structure with different trench profiles in the surface,in which a shallow gate trench is shielded by a deep emitter trench and a thick oxide layer under it.Compared with the conventional CSTBT(con-CSTBT),the proposed DSS-CSTBT not only alleviates the negative impact of the shallow gate trench and highly doped CS layer on the breakdown voltage(BV),but also well reduces the gate-collector capacitance CGC,gate charge Q_(G),and turn-off loss E_(OFF)of the device.Furthermore,lower turn-on loss E_(ON)and gate drive loss E_(DR)are also obtained.Simulation results show that with the same CS layer doping concentration N_(CS)=1.5×10^(16)cm^(-3),the BV increases from 1312 V of the con-CSTBT to 1423 V of the proposed DSS-CSTBT with oxide layer thickness under gate(T_(og2))of 1μm.Moreover,compared with the con-CSTBT,the C_(GC)at V_(CE)of 25 V and miller plateau charge(Q_(GC))for the proposed DSS-CSTBT with T_(og2)of 1μm are reduced by 79.4%and 74.3%,respectively.With the VGEincreases from 0 V to 15 V,the total QGfor the proposed DSS-CSTBT with T_(og2)of 1μm is reduced by 49.5%.As a result,at the same on-state voltage drop(V_(CEON))of 1.55 V,the E_(ON)and E_(OFF)are reduced from 20.3 mJ/cm^(2)and 19.3 mJ/cm^(2)for the con-CSTBT to8.2 mJ/cm^(2)and 9.7 mJ/cm^(2)for the proposed DSS-CSTBT with T_(og2)of 1μm,respectively.The proposed DSS-CSTBT not only significantly improves the trade-off relationship between the V_(CEON)and E_(OFF)but also greatly reduces the E_(ON).
基金the National Natural Science Foundation of China(51708001).
文摘The urban grass-roots library is an important part of the public cultural service system,and also a place to carry out national reading and lifelong learning,which is of great significance to the construction of a learning society.In this paper,the development and evolution of urban grassroots libraries in China are reviewed,and the current situation and usage issues of grassroots libraries in Beijing are analyzed.Moreover,the development strategy of idea stores in London,UK is studied,and characteristics are summarized,and possible references are sought.In the new era,urban grassroots libraries should integrate into communities with multiple functions and play a more sufficient role in public education,learning and training,and other aspects.
文摘To understand the influence of the initial release conditions on the separation characteristics of the store and improve it under high Mach number(Ma=4)flight conditions,the overset grid method and the Realizable k−εturbulence model coupled with an equation with six degrees of freedom are used to simulate the store released from the internal bay.The motion trajectory and the attitude angle of the store separation under the conditions of different centroid,velocity,height and control measures are given by the calculated result.Through analysis,the position of the centroid will affect the separation of the store,which needs to be considered in the design.Increasing the launching height is conducive to the separation of the store.If the store has an initial velocity,it can leave the internal bay more quickly and reduce the probability of collision with the wall.Cylindrical rod and slanted aft wall control measures can improve the attitude of the store and make the store fall more smoothly.
