An OpenMP approach was proposed to parallelize the sequential molecular dynamics(MD) code on shared memory machines. When a code is converted from the sequential form to the parallel form, data dependence is a main pr...An OpenMP approach was proposed to parallelize the sequential molecular dynamics(MD) code on shared memory machines. When a code is converted from the sequential form to the parallel form, data dependence is a main problem. A traditional sequential molecular dynamics code is anatomized to find the data dependence segments in it, and the two different methods, i.e., recover method and backward mapping method were used to eliminate those data dependencies in order to realize the parallelization of this sequential MD code. The performance of the parallelized MD code was analyzed by using some performance analysis tools. The results of the test show that the computing size of this code increases sharply form 1 million atoms before parallelization to 20 million atoms after parallelization, and the wall clock during computing is reduced largely. Some hot-spots in this code are found and optimized by improved algorithm. The efficiency of parallel computing is 30% higher than that of before, and the calculation time is saved and larger scale calculation problems are solved.展开更多
Automated performance tuning of data management systems offer various benefits such as improved performance, declined administration costs, and reduced workloads to database administrators (DBAs). Currently, DBAs tune...Automated performance tuning of data management systems offer various benefits such as improved performance, declined administration costs, and reduced workloads to database administrators (DBAs). Currently, DBAs tune the performance of database systems with a little help from the database servers. In this paper, we propose a new technique for automated performance tuning of data management systems. Firstly, we show how to use the periods of low workload time for performance improvements in the periods of high workload time. We demonstrate that extensions of a database system with materialised views and indices when a workload is low may contribute to better performance for a successive period of high workload. The paper proposes several online algorithms for continuous processing of estimated database workloads and for the discovery of the best plan for materialised view and index database extensions and of elimination of the extensions that are no longer needed. We present the results of experiments that show how the proposed automated performance tuning technique improves the overall performance of a data management system. 展开更多
In conventional piezoelectric micromachined ultrasonic transducers(PMUTs),the backside acoustic energy is often used inefficiently,resulting in up to half of the energy being wasted.Vacuum encapsulation can improve th...In conventional piezoelectric micromachined ultrasonic transducers(PMUTs),the backside acoustic energy is often used inefficiently,resulting in up to half of the energy being wasted.Vacuum encapsulation can improve the energy utilization efficiency,but this technique is not compatible with state-of-the-art devices such as cantilever-based PMUTs.A closed back cavity provides an alternative method for effectively utilizing the backside acoustic energy.This paper investigates the effects of a closed back cavity on PMUT performance through theoretical analysis,simulations,and experimental verification.Increasing the cavity depth produces a periodic modulation of several key PMUT metrics,such as the relative frequency deviation and quality factor.The optimal cavity depth for PMUTs that ensures a robust resonant frequency and high quality factor is defined as a function of the acoustic wavelength.A closed back cavity also provides an effective method for continuously tuning the quality factor,and thus the bandwidth,of PMUTs.This work paves the way for air-coupled PMUTs with adjustable performance for various applications.展开更多
The non-volatile memory(NVM)is the promising device to store data and accelerate big data analysis due to its excellent I/O performance.However,we find that simply replacing hard disk drive(HDD)with NVM cannot bring t...The non-volatile memory(NVM)is the promising device to store data and accelerate big data analysis due to its excellent I/O performance.However,we find that simply replacing hard disk drive(HDD)with NVM cannot bring the expected performance improvement.In this paper,we take the data recovery issue in Hadoop file system(HDFS)as a case study to investigate how to take advantage of the performance of NVM.We analyze the data recovery mechanism in HDFS and find that the configuration of replication tasks in the DataNode can affect the data recovery significantly.We conduct extensive analysis and experiments tuning the configuration and also get some interesting findings.With the new configuration,we increase the data recovery performance from 17 to 71%.We can also improve the execution performance of MapReduce jobs from 28 to 59%through optimized configuration.We also find that the sudden data recovery brings disordered network resource competition,which reduces the performance of MapReduce jobs.Hence,We present a priority-aware multi-stage data recovery method.This improves the performance by 32.5%in addition for the MapReduce jobs.展开更多
Frequency tunability has become a subject of concern in the field of high-power microwave（HPM） source research.However, little information about the corresponding mode converter is available. A tunable circularly-po...Frequency tunability has become a subject of concern in the field of high-power microwave（HPM） source research.However, little information about the corresponding mode converter is available. A tunable circularly-polarized turnstilejunction mode converter（TCTMC） for high-power microwave applications is presented in this paper. The input coaxial TEM mode is transformed into TE（10） mode with different phase delays in four rectangular waveguides and then converted into a circularly-polarized TE（11） circular waveguide mode. Besides, the rods are added to reduce or even eliminate the reflection. The innovations in this study are as follows. The tunning mechanism is added to the mode converter, which can change the effective length of rectangular waveguide and the distance between the rods installed upstream and the closest edge of the rectangular waveguide, thus improving the conversion efficiency and bandwidth. The conversion efficiency of TCTMC can reach above 98% over the frequency range of 1.42 GHz–2.29 GHz, and the frequency tunning bandwidth is about 47%. Significantly, TCTMC can obtain continuous high conversion efficiency of different frequency points with the change of tuning mechanism.展开更多
Tuning the microporosity of crystalline microporous materials is critical for achieving good application performance.Zeolitic iron molybdate shows both redox properties and microporosity,and a redox-triggered micropor...Tuning the microporosity of crystalline microporous materials is critical for achieving good application performance.Zeolitic iron molybdate shows both redox properties and microporosity,and a redox-triggered microporosity change is investigated.The micropores of the material are adjusted at the sub-atomic scale by redox reactions,enabling tuning of the adsorption and separation performances of the material based on the redox of the material.The adsorption capacities of CO_(2) and CH_(4) increase and decrease with the reduction and oxidation of the material,respectively.The separation performance for CO_(2)/CH_(4) of the material is enhanced and weakened when the material is reduced and oxidized.The robust material is able to separate CO_(2)/CH_(4) at high temperatures and humidities and can be reused without changing the structure.展开更多
The reasonable design of electrode materials is crucial for tuning the electrochemical performances of advanced energy storage systems.Co–Ni–Se nanosheets uniformly growing on a butterfly-wing-derived carbon framewo...The reasonable design of electrode materials is crucial for tuning the electrochemical performances of advanced energy storage systems.Co–Ni–Se nanosheets uniformly growing on a butterfly-wing-derived carbon framework(Co–Ni–Se/BWCF)with strong anchoring are devised and prepared by a microwave treatment–ion exchange–chemical etching–hydrothermal selenization technique.Benefiting from its multi-components and unique structure,Co–Ni–Se/BWCF-160 exhibits excellent supercapacitor and sodium storage performances as self-supporting electrodes.展开更多
With the advent of the Big Data era,the demand for storing,processing,and analyzing this vast and growing amount of data has emerged in the market.Since a single node cannot cope with its complexity requirements,high-...With the advent of the Big Data era,the demand for storing,processing,and analyzing this vast and growing amount of data has emerged in the market.Since a single node cannot cope with its complexity requirements,high-performance systems typically operate in a distributed environment.Today,high-performance distributed computing systems are the foundations of many important infrastructures.However,the diverse development of hardware platforms,the spurt of data growth,and the rapid changes in applications are increasingly challenging resource management,energy efficiency,performance tuning,scalability,and fault tolerance.展开更多
More and more embedded systems now support multimedia networking on the Ethernet or using the Wireless LAN （WLAN） technologies. An embedded system, typically designed with a low-performance microprocessor in order t...More and more embedded systems now support multimedia networking on the Ethernet or using the Wireless LAN （WLAN） technologies. An embedded system, typically designed with a low-performance microprocessor in order to reduce both power usage and cost, often shows poor performance on multimedia networking, This paper describes a case study of improving the TCP/IP networking performance of a real-world embedded uClinux multimedia system, which is configured with both a fast Ethernet and a Wi-Fi connection. This paper analyzes networking overhead of the embedded system, and provides specific methods to improve its networking performance based upon the analysis, Our benchmark results indicate that these methods can improve the multimedia networking throughput on the embedded system by about 1596 .展开更多
It is an important task to improve performance for sparse matrix vector multiplication （SpMV）, and it is a difficult task because of its irregular memory access. Gen- eral purpose GPU （GPGPU） provides high computi...It is an important task to improve performance for sparse matrix vector multiplication （SpMV）, and it is a difficult task because of its irregular memory access. Gen- eral purpose GPU （GPGPU） provides high computing abil- ity and substantial bandwidth that cannot be fully exploited by SpMV due to its irregularity. In this paper, we propose two novel methods to optimize the memory bandwidth for SpMV on GPGPU. First, a new storage format is proposed to exploit memory bandwidth of GPU architecture more effi- ciently. The new storage format can ensure that there are as many non-zeros as possible in the format which is suitable to exploit the memory bandwidth of the GPU. Second, we pro- pose a cache blocking method to improve the performance of SpMV on GPU architecture. The sparse matrix is partitioned into sub-blocks that are stored in CSR format. With the block- ing method, the corresponding part of vector x can be reused in the GPU cache, so the time to access the global memory for vector x is reduced heavily. Experiments are carried out on three GPU platforms, GeForce 9800 GX2, GeForce GTX 480, and Tesla K40. Experimental results show that both new methods can efficiently improve the utilization of GPU mem- ory bandwidth and the performance of the GPU.展开更多
The global water scarcity problem is becoming increasingly acute as a result of population growth and environmental changes.Water collection from air is a promising solution and is gaining popularity because it in-vol...The global water scarcity problem is becoming increasingly acute as a result of population growth and environmental changes.Water collection from air is a promising solution and is gaining popularity because it in-volves the collection of ubiquitous water vapor.The inherent structural properties of biopolymers,including abundant hydrophilic groups,naturally evolved interfaces,and hierarchical structures,provide natural sites for the trapping,transport,and storage of water.Moreover,it is a substantial source of inspiration for scientists,thereby facilitating the design and development of advanced materials for water collection from air.This re-view commences with a concise overview of the adsorption-desorption mechanism,encompassing the processes of adsorption and uptake in addition to isotherms.The subsequent sections of the paper discuss how biopolymer materials,from the macroscopic to the molecular level,can take advantage of their natural structure to establish interactions with water and realize the applications of water collection from air and point out the advantages of biopolymers for this application in terms of structural design and performance tuning.Finally,the current challenges facing biopolymer resources are summarized.The objective of this review is to establish a novel paradigm for the design of renewable biopolymer-based materials and new green water-efficient recycling technologies.展开更多
基金Project (50371026) supported by the National Natural Science Foundation of China
文摘An OpenMP approach was proposed to parallelize the sequential molecular dynamics(MD) code on shared memory machines. When a code is converted from the sequential form to the parallel form, data dependence is a main problem. A traditional sequential molecular dynamics code is anatomized to find the data dependence segments in it, and the two different methods, i.e., recover method and backward mapping method were used to eliminate those data dependencies in order to realize the parallelization of this sequential MD code. The performance of the parallelized MD code was analyzed by using some performance analysis tools. The results of the test show that the computing size of this code increases sharply form 1 million atoms before parallelization to 20 million atoms after parallelization, and the wall clock during computing is reduced largely. Some hot-spots in this code are found and optimized by improved algorithm. The efficiency of parallel computing is 30% higher than that of before, and the calculation time is saved and larger scale calculation problems are solved.
文摘Automated performance tuning of data management systems offer various benefits such as improved performance, declined administration costs, and reduced workloads to database administrators (DBAs). Currently, DBAs tune the performance of database systems with a little help from the database servers. In this paper, we propose a new technique for automated performance tuning of data management systems. Firstly, we show how to use the periods of low workload time for performance improvements in the periods of high workload time. We demonstrate that extensions of a database system with materialised views and indices when a workload is low may contribute to better performance for a successive period of high workload. The paper proposes several online algorithms for continuous processing of estimated database workloads and for the discovery of the best plan for materialised view and index database extensions and of elimination of the extensions that are no longer needed. We present the results of experiments that show how the proposed automated performance tuning technique improves the overall performance of a data management system.
基金supported in part by the National Natural Science Foundation of China(NSFC)(Grant No.62001322)in part by the National Key Research and Development Program(Grant No.2020YFB2008800).
文摘In conventional piezoelectric micromachined ultrasonic transducers(PMUTs),the backside acoustic energy is often used inefficiently,resulting in up to half of the energy being wasted.Vacuum encapsulation can improve the energy utilization efficiency,but this technique is not compatible with state-of-the-art devices such as cantilever-based PMUTs.A closed back cavity provides an alternative method for effectively utilizing the backside acoustic energy.This paper investigates the effects of a closed back cavity on PMUT performance through theoretical analysis,simulations,and experimental verification.Increasing the cavity depth produces a periodic modulation of several key PMUT metrics,such as the relative frequency deviation and quality factor.The optimal cavity depth for PMUTs that ensures a robust resonant frequency and high quality factor is defined as a function of the acoustic wavelength.A closed back cavity also provides an effective method for continuously tuning the quality factor,and thus the bandwidth,of PMUTs.This work paves the way for air-coupled PMUTs with adjustable performance for various applications.
基金supported in part by the National Key R&D Program of China under Grant 2019YFB2102002the National Natural Science Foundation of China under Grant 61802182the Collaborative Innovation Center Kouba of Novel Software Technology and Industrialization。
文摘The non-volatile memory(NVM)is the promising device to store data and accelerate big data analysis due to its excellent I/O performance.However,we find that simply replacing hard disk drive(HDD)with NVM cannot bring the expected performance improvement.In this paper,we take the data recovery issue in Hadoop file system(HDFS)as a case study to investigate how to take advantage of the performance of NVM.We analyze the data recovery mechanism in HDFS and find that the configuration of replication tasks in the DataNode can affect the data recovery significantly.We conduct extensive analysis and experiments tuning the configuration and also get some interesting findings.With the new configuration,we increase the data recovery performance from 17 to 71%.We can also improve the execution performance of MapReduce jobs from 28 to 59%through optimized configuration.We also find that the sudden data recovery brings disordered network resource competition,which reduces the performance of MapReduce jobs.Hence,We present a priority-aware multi-stage data recovery method.This improves the performance by 32.5%in addition for the MapReduce jobs.
基金supported by the National Natural Science Foundation of China(Grant No.61671457)
文摘Frequency tunability has become a subject of concern in the field of high-power microwave（HPM） source research.However, little information about the corresponding mode converter is available. A tunable circularly-polarized turnstilejunction mode converter（TCTMC） for high-power microwave applications is presented in this paper. The input coaxial TEM mode is transformed into TE（10） mode with different phase delays in four rectangular waveguides and then converted into a circularly-polarized TE（11） circular waveguide mode. Besides, the rods are added to reduce or even eliminate the reflection. The innovations in this study are as follows. The tunning mechanism is added to the mode converter, which can change the effective length of rectangular waveguide and the distance between the rods installed upstream and the closest edge of the rectangular waveguide, thus improving the conversion efficiency and bandwidth. The conversion efficiency of TCTMC can reach above 98% over the frequency range of 1.42 GHz–2.29 GHz, and the frequency tunning bandwidth is about 47%. Significantly, TCTMC can obtain continuous high conversion efficiency of different frequency points with the change of tuning mechanism.
基金supported by the National Natural Science Foundation of China(grant nos 22075153,22006077 and 21622607)Major Special Projects of the Plan“Science and Technology Innovation 2025”in Ningbo(no.2018B10016)the K.C.Wong Magna Fund in Ningbo University.
文摘Tuning the microporosity of crystalline microporous materials is critical for achieving good application performance.Zeolitic iron molybdate shows both redox properties and microporosity,and a redox-triggered microporosity change is investigated.The micropores of the material are adjusted at the sub-atomic scale by redox reactions,enabling tuning of the adsorption and separation performances of the material based on the redox of the material.The adsorption capacities of CO_(2) and CH_(4) increase and decrease with the reduction and oxidation of the material,respectively.The separation performance for CO_(2)/CH_(4) of the material is enhanced and weakened when the material is reduced and oxidized.The robust material is able to separate CO_(2)/CH_(4) at high temperatures and humidities and can be reused without changing the structure.
基金financially supported by the National Natural Science Foundation of China(52102100)the Natural Science Foundation of Jiangsu Province(BK20181469).
文摘The reasonable design of electrode materials is crucial for tuning the electrochemical performances of advanced energy storage systems.Co–Ni–Se nanosheets uniformly growing on a butterfly-wing-derived carbon framework(Co–Ni–Se/BWCF)with strong anchoring are devised and prepared by a microwave treatment–ion exchange–chemical etching–hydrothermal selenization technique.Benefiting from its multi-components and unique structure,Co–Ni–Se/BWCF-160 exhibits excellent supercapacitor and sodium storage performances as self-supporting electrodes.
文摘With the advent of the Big Data era,the demand for storing,processing,and analyzing this vast and growing amount of data has emerged in the market.Since a single node cannot cope with its complexity requirements,high-performance systems typically operate in a distributed environment.Today,high-performance distributed computing systems are the foundations of many important infrastructures.However,the diverse development of hardware platforms,the spurt of data growth,and the rapid changes in applications are increasingly challenging resource management,energy efficiency,performance tuning,scalability,and fault tolerance.
文摘More and more embedded systems now support multimedia networking on the Ethernet or using the Wireless LAN （WLAN） technologies. An embedded system, typically designed with a low-performance microprocessor in order to reduce both power usage and cost, often shows poor performance on multimedia networking, This paper describes a case study of improving the TCP/IP networking performance of a real-world embedded uClinux multimedia system, which is configured with both a fast Ethernet and a Wi-Fi connection. This paper analyzes networking overhead of the embedded system, and provides specific methods to improve its networking performance based upon the analysis, Our benchmark results indicate that these methods can improve the multimedia networking throughput on the embedded system by about 1596 .
文摘It is an important task to improve performance for sparse matrix vector multiplication （SpMV）, and it is a difficult task because of its irregular memory access. Gen- eral purpose GPU （GPGPU） provides high computing abil- ity and substantial bandwidth that cannot be fully exploited by SpMV due to its irregularity. In this paper, we propose two novel methods to optimize the memory bandwidth for SpMV on GPGPU. First, a new storage format is proposed to exploit memory bandwidth of GPU architecture more effi- ciently. The new storage format can ensure that there are as many non-zeros as possible in the format which is suitable to exploit the memory bandwidth of the GPU. Second, we pro- pose a cache blocking method to improve the performance of SpMV on GPU architecture. The sparse matrix is partitioned into sub-blocks that are stored in CSR format. With the block- ing method, the corresponding part of vector x can be reused in the GPU cache, so the time to access the global memory for vector x is reduced heavily. Experiments are carried out on three GPU platforms, GeForce 9800 GX2, GeForce GTX 480, and Tesla K40. Experimental results show that both new methods can efficiently improve the utilization of GPU mem- ory bandwidth and the performance of the GPU.
基金support from the National Natural Science Foundation of China(32271814)the Natural Science Foundation of Tianjin(24JCJQJC00030 and 23JCZDJC00630).
文摘The global water scarcity problem is becoming increasingly acute as a result of population growth and environmental changes.Water collection from air is a promising solution and is gaining popularity because it in-volves the collection of ubiquitous water vapor.The inherent structural properties of biopolymers,including abundant hydrophilic groups,naturally evolved interfaces,and hierarchical structures,provide natural sites for the trapping,transport,and storage of water.Moreover,it is a substantial source of inspiration for scientists,thereby facilitating the design and development of advanced materials for water collection from air.This re-view commences with a concise overview of the adsorption-desorption mechanism,encompassing the processes of adsorption and uptake in addition to isotherms.The subsequent sections of the paper discuss how biopolymer materials,from the macroscopic to the molecular level,can take advantage of their natural structure to establish interactions with water and realize the applications of water collection from air and point out the advantages of biopolymers for this application in terms of structural design and performance tuning.Finally,the current challenges facing biopolymer resources are summarized.The objective of this review is to establish a novel paradigm for the design of renewable biopolymer-based materials and new green water-efficient recycling technologies.
