In the article, an experiment is aimed at clarifying the transfer efficiency of the database in the cloud infrastructure. The system was added to the control unit, which has guided the database search in the local par...In the article, an experiment is aimed at clarifying the transfer efficiency of the database in the cloud infrastructure. The system was added to the control unit, which has guided the database search in the local part or in the cloud. It is shown that the time data acquisition remains unchanged as a result of modification. Suggestions have been made about the use of the theory of dynamic systems to hybrid cloud database. The present work is aimed at attracting the attention of specialists in the field of cloud database to the apparatus control theory. The experiment presented in this article allows the use of the description of the known methods for solving important practical problems.展开更多
An excellent cardinality estimation can make the query optimiser produce a good execution plan.Although there are some studies on cardinality estimation,the prediction results of existing cardinality estimators are in...An excellent cardinality estimation can make the query optimiser produce a good execution plan.Although there are some studies on cardinality estimation,the prediction results of existing cardinality estimators are inaccurate and the query efficiency cannot be guaranteed as well.In particular,they are difficult to accurately obtain the complex relationships between multiple tables in complex database systems.When dealing with complex queries,the existing cardinality estimators cannot achieve good results.In this study,a novel cardinality estimator is proposed.It uses the core techniques with the BiLSTM network structure and adds the attention mechanism.First,the columns involved in the query statements in the training set are sampled and compressed into bitmaps.Then,the Word2vec model is used to embed the word vectors about the query statements.Finally,the BiLSTM network and attention mechanism are employed to deal with word vectors.The proposed model takes into consideration not only the correlation between tables but also the processing of complex predicates.Extensive experiments and the evaluation of BiLSTM-Attention Cardinality Estimator(BACE)on the IMDB datasets are conducted.The results show that the deep learning model can significantly improve the quality of cardinality estimation,which is a vital role in query optimisation for complex databases.展开更多
A new theory on the construction of optimal truncated Low-Dimensional Dynamical Systems (LDDSs) with different physical meanings has been developed, The physical properties of the optimal bases are reflected in the us...A new theory on the construction of optimal truncated Low-Dimensional Dynamical Systems (LDDSs) with different physical meanings has been developed, The physical properties of the optimal bases are reflected in the user-defined optimal conditions, Through the analysis of linear and nonlinear examples, it is shown that the LDDSs constructed by using the Proper Orthogonal Decomposition (POD) method are not the optimum. After comparing the errors of LDDSs based on the new theory POD and Fourier methods, it is concluded that the LDDSs based on the new theory are optimally truncated and catch the desired physical properties of the systems.展开更多
Most of the proposed concurrency control protocols for real time database systems are based on serializability theorem. Owing to the unique characteristics of real time database applications and the importance of sa...Most of the proposed concurrency control protocols for real time database systems are based on serializability theorem. Owing to the unique characteristics of real time database applications and the importance of satisfying the timing constraints of transactions, serializability is too strong as a correctness criterion and not suitable for real time databases in most cases. On the other hand, relaxed serializability including epsilon serializability and similarity serializability can allow more real time transactions to satisfy their timing constraints, but database consistency may be sacrificed to some extent. We thus propose the use of weak serializability(WSR) that is more relaxed than conflicting serializability while database consistency is maintained. In this paper, we first formally define the new notion of correctness called weak serializability. After the necessary and sufficient conditions for weak serializability are shown, corresponding concurrency control protocol WDHP(weak serializable distributed high priority protocol) is outlined for distributed real time databases, where a new lock mode called mask lock mode is proposed for simplifying the condition of global consistency. Finally, through a series of simulation studies, it is shown that using the new concurrency control protocol the performance of distributed real time databases can be greatly improved.展开更多
In the context of a proliferation of DatabaseManagement Systems(DBMSs),we have envisioned and produced an OWL 2 ontology able to provide a high-level machine-processable description of the DBMSs domain.This conceptual...In the context of a proliferation of DatabaseManagement Systems(DBMSs),we have envisioned and produced an OWL 2 ontology able to provide a high-level machine-processable description of the DBMSs domain.This conceptualization aims to facilitate a proper execution of various software engineering processes and database-focused administration tasks.Also,it can be used to improve the decision-making process for determining/selecting the appropriate DBMS,subject to specific requirements.The proposed model describes the most important features and aspects regarding the DBMS domain,including the support for various paradigms(relational,graph-based,key-value,tree-like,etc.),query languages,platforms(servers),plus running environments(desktop,Web,cloud),specific contexts—i.e.,focusing on optimizing queries,redundancy,security,performance,schema vs.schema-less approaches,programming languages/paradigms,and others.The process of populating the ontology with significant individuals(actual DBMSs)benefits from the existing knowledge exposed by free and open machine-processable knowledge bases,by using structured data fromWikipedia and related sources.The pragmatic use of our ontology is demonstrated by two educational software solutions based on current practices in Web application development,proving support for learning and experimenting key features of the actual semantic Web technologies and tools.This approach is also an example of using multiple knowledge from database systems,semanticWeb technologies,and software engineering areas.展开更多
In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can e...In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can enhance the performance of real-time concurrency control mechanism by reducing the number of transactions that might miss their deadlines, and compare the performance of validation concurrency control protocol with that of HP2PL(High priority two phase locking) protocol and OCC-TI-WAIT-50(Optimistic concurrency control-time interval-wait-50) protocol under shared-disk architecture by simulation. The simulation results reveal that the protocol the author presented can effectively reduce the number of transactions restarting which might miss their deadlines and performs better than HP2PL and OCC-TI-WAIT-50. It works well when arrival rate of transaction is lesser than threshold. However, due to resource contention the percentage of missing deadline increases sharply when arrival rate is greater than the threshold.展开更多
Secretion systems, macromolecules to pass which can mediate the across cellular membranes, are essential for virulent and genetic material exchange among bacterial species[1]. Type IV secretion system (T4SS) is one ...Secretion systems, macromolecules to pass which can mediate the across cellular membranes, are essential for virulent and genetic material exchange among bacterial species[1]. Type IV secretion system (T4SS) is one of the secretion systems and it usually consists of 12 genes: VirB1, VirB2 ...VirB11, and VirD4[2]. The structure and molecular mechanisms of these genes have been well analyzed in Gram-negative strains[3] and Gram-positive strains were once believed to be lack of T4SS. However, some recent studies revealed that one or more virB/D genes also exist in some kinds of Gram-positive bacteria and play similar role, and form a T4SS-like system[3]. The VirBl-like, VirB4, VirB6, and VirD4 genes were identified in the chromosome of Gram-positive bacterium Streptococcus suis in our previous studies and their role as important mobile elements for horizontal transfer to recipients in an 89 K pathogenicity island (PAl) was demonstrated[45]. However, their structure and molecular mechanisms in other strains, especially in Gram-positive strains, are remained unclear.展开更多
A DMVOCC-MVDA(distributed multiversion optimistic concurrency control with multiversion dynamic adjustment)protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments.At...A DMVOCC-MVDA(distributed multiversion optimistic concurrency control with multiversion dynamic adjustment)protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments.At the mobile hosts,all transactions perform local pre-validation.The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle.Transactions that survive in local pre-validation must be submitted to the server for local final validation.The new protocol eliminates conflicts between mobile read-only and mobile update transactions,and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions.Mobile read-only transactions can be committed with no-blocking,and respond time of mobile read-only transactions is greatly shortened.The tolerance of mobile transactions of disconnections from the broadcast channel is increased.In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants.The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate,restart rate,commit rate.Under high work load(think time is 1s)the miss rate of DMVOCC-MVDA is only 14.6%,is significantly lower than that of other protocols.The restart rate of DMVOCC-MVDA is only 32.3%,showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions.And the commit rate of DMVOCC-MVDA is up to 61.2%,which is obviously higher than that of other protocols.展开更多
This paper formally defines and analyses the new notion of correctness called quasi serializability, and then outlines corresponding concurrency control protocol QDHP for distributed real-time databases. Finally, thro...This paper formally defines and analyses the new notion of correctness called quasi serializability, and then outlines corresponding concurrency control protocol QDHP for distributed real-time databases. Finally, through a series of simulation studies, it shows that using the new concurrency control protocol the performance of distributed real-time databases can be much improved.展开更多
Recovery performance in the event of failures is very important for distributed real-time database systems. This paper presents a time-cognizant logging-based crash recovery scheme (TCLCRS) that aims at distributed ...Recovery performance in the event of failures is very important for distributed real-time database systems. This paper presents a time-cognizant logging-based crash recovery scheme (TCLCRS) that aims at distributed real-time databases, which adopts a main memory database as its ground support. In our scheme, each site maintains a real-time log for local transactions and the subtransactions, which execute at the site, and execte local checkpointing independently. Log records are stored in non-volatile high- speed store, which is divided into four different partitions based on transaction classes. During restart recovery after a site crash, partitioned crash recovery strategy is adopted to ensure that the site can be brought up before the entire local secondary database is reloaded in main memory. The partitioned crash recovery strategy not only guarantees the internal consistency to be recovered, but also guarantee the temporal consistency and recovery of the sates of physical world influenced by uncommitted transactions. Combined with two- phase commit protocol, TCLCRS can guarantee failure atomicity of distributed real-time transactions.展开更多
This paper introduces a multi-granularity locking model (MGL) for concurrency control in object-oriented database system briefiy, and presents a MGL model formally. Four lockingscheduling algorithms for MGL are propos...This paper introduces a multi-granularity locking model (MGL) for concurrency control in object-oriented database system briefiy, and presents a MGL model formally. Four lockingscheduling algorithms for MGL are proposed in the paper. The ideas of single queue scheduling(SQS) and dual queue scheduling (DQS) are proposed and the algorithm and the performance evaluation for these two scheduling are presented in some paper. This paper describes a new idea of thescheduling for MGL, compatible requests first (CRF). Combining the new idea with SQS and DQS,we propose two new scheduling algorithms called CRFS and CRFD. After describing the simulationmodel, this paper illustrates the comparisons of the performance among these four algorithms. Asshown in the experiments, DQS has better performance than SQS, CRFD is better than DQS, CRFSperforms better than SQS, and CRFS is the best one of these four scheduling algorithms.展开更多
Computer simulation for materials processing needs a huge database containing a great deal of various physical properties of materials. In order to employ the accumulated large data on materials heat treatment in the ...Computer simulation for materials processing needs a huge database containing a great deal of various physical properties of materials. In order to employ the accumulated large data on materials heat treatment in the past years, it is significant to develop an intelligent database system. Based on the data mining technology for data analysis, an intelligent database web tool system of computer simulation for heat treatment process named as IndBASEweb-HT was built up. The architecture and the arithmetic of this system as well as its application were introduced.展开更多
Oil film forces are usually obtained for dynamic analysis of a journal bearing system by using the approximate analytical formula or solving the Reynolds equation. None of them is suitable for rotor system bifurcation...Oil film forces are usually obtained for dynamic analysis of a journal bearing system by using the approximate analytical formula or solving the Reynolds equation. None of them is suitable for rotor system bifurcation analysis because they are either of poor accuracy or time consuming. Oil film forces database is proposed is to transform the journal speed variation range in radial and circumferential directions from (-∞,+∞) to (-1, +1). The numerical results show the suggested method is much more effective. And sub harmonic, quasi periodic and chaotic vibrations are predicted for a range of speed and unbalance parameters.展开更多
The objective of this paper is to develop a GIS(Geographic Information System) database for Jiuzhaigou National Nature Reserve(Jiuzhaigou,hereafter) in China and demonstrate its application as a research tool.A cost-e...The objective of this paper is to develop a GIS(Geographic Information System) database for Jiuzhaigou National Nature Reserve(Jiuzhaigou,hereafter) in China and demonstrate its application as a research tool.A cost-effective procedure was developed to compile a variety of geographical and biological data of the study area in terms of popular GIS format such as shape files.These files were further calibrated and validated using field surveys data.The developed GIS database was used to quantify the distributions of the wildlife(amphibians,mammals,and birds) using the distances of the wildlife to the centerline of the bus-tour routes.The Pearson correlation coefficient was used to quantify the correlation in space between pairs of different wildlife using the number of habitats for given space contexts.An ArcObject-based macro was developed to perform the analysis.The results showed the majority of the habitats of wildlife are located in the proximity of the tour-bus routes with an average distance ranging from 564 to 894 m depending on types of wildlife.This indicates a possibility of the disturbance to the wildlife by human activities.The correlation coefficient of the wildlife ranged from 0.36 to 0.64 depending on pairs of wildlife,indicating some correlations in space.However,due to the limited sample size,the statistical significances need to be further investigated.This paper has successfully demonstrated the use of the GIS-based database as a research tool for environmental study.展开更多
The selection of titanium alloys has become a complex decision-making task due to the growing number of creation and utilization for titanium alloys,with each having its own characteristics,advantages,and limitations....The selection of titanium alloys has become a complex decision-making task due to the growing number of creation and utilization for titanium alloys,with each having its own characteristics,advantages,and limitations.In choosing the most appropriate titanium alloys,it is very essential to offer a reasonable and intelligent service for technical engineers.One possible solution of this problem is to develop a database system(DS) to help retrieve rational proposals from different databases and information sources and analyze them to provide useful and explicit information.For this purpose,a design strategy of the fuzzy set theory is proposed,and a distributed database system is developed.Through ranking of the candidate titanium alloys,the most suitable material is determined.It is found that the selection results are in good agreement with the practical situation.展开更多
To improve the effectiveness of dam safety monitoring database systems, the development process of a multi-dimensional conceptual data model was analyzed and a logic design wasachieved in multi-dimensional database mo...To improve the effectiveness of dam safety monitoring database systems, the development process of a multi-dimensional conceptual data model was analyzed and a logic design wasachieved in multi-dimensional database mode. The optimal data model was confirmed by identifying data objects, defining relations and reviewing entities. The conversion of relations among entities to external keys and entities and physical attributes to tables and fields was interpreted completely. On this basis, a multi-dimensional database that reflects the management and analysis of a dam safety monitoring system on monitoring data information has been established, for which factual tables and dimensional tables have been designed. Finally, based on service design and user interface design, the dam safety monitoring system has been developed with Delphi as the development tool. This development project shows that the multi-dimensional database can simplify the development process and minimize hidden dangers in the database structure design. It is superior to other dam safety monitoring system development models and can provide a new research direction for system developers.展开更多
Database Security and Protection System (DSPS) is a security platform for fighting malicious DBMS. The security and performance are critical to DSPS. The authors suggested a key management scheme by combining the serv...Database Security and Protection System (DSPS) is a security platform for fighting malicious DBMS. The security and performance are critical to DSPS. The authors suggested a key management scheme by combining the server group structure to improve availability and the key distribution structure needed by proactive security. This paper detailed the implementation of proactive security in DSPS. After thorough performane analysis, the authors concluded that the performance difference between the replicated mechanism and proactive mechanism becomes smaller and smaller with increasing number of concurrent connections ; and that proactive security is very useful and practical for large, critical applications.展开更多
Data-Base Management System (DBMS) is the current standard for storing information. A DBMS organizes and maintains a structure of storage of data. Databases make it possible to store vast amounts of randomly created i...Data-Base Management System (DBMS) is the current standard for storing information. A DBMS organizes and maintains a structure of storage of data. Databases make it possible to store vast amounts of randomly created information and then retrieve items using associative reasoning in search routines. However, design of databases is cumbersome. If one is to use a database primarily to directly input information, each field must be predefined manually, and the fields must be organized to permit coherent data input. This static requirement is problematic and requires that database table(s) be predefined and customized at the outset, a difficult proposition since current DBMS lack a user friendly front end to allow flexible design of the input model. Furthermore, databases are primarily text based, making it difficult to process graphical data. We have developed a general and nonproprietary approach to the problem of input modeling designed to make use of the known informational architecture to map data to a database and then retrieve the original document in freely editable form. We create form templates using ordinary word processing software: Microsoft InfoPath 2007. Each field in the form is given a unique name identifier in order to be distinguished in the database. It is possible to export text based documents created initially in Microsoft Word by placing a colon at the beginning of any desired field location. InfoPath then captures the preceding string and uses it as the label for the field. Each form can be structured in a way to include any combination of both textual and graphical fields. We input data into InfoPath templates. We then submit the data through a web service to populate fields in an SQL database. By appropriate indexing, we can then recall the entire document from the SQL database for editing, with corresponding audit trail. Graphical data is handled no differently than textual data and is embedded in the database itself permitting direct query approaches. This technique makes it possible for general users to benefit from a combined text-graphical database environment with a flexible non-proprietary interface. Consequently, any template can be effortlessly transformed to a database system and easily recovered in a narrative form.展开更多
The Mg-Al-Zn-Y-Ce system is one of the key systems for designing high-strength Mg alloys. The purpose of the present article is to develop a thermodynamic database for the Mg-Al-Zn-Y-Ce multicomponent system to design...The Mg-Al-Zn-Y-Ce system is one of the key systems for designing high-strength Mg alloys. The purpose of the present article is to develop a thermodynamic database for the Mg-Al-Zn-Y-Ce multicomponent system to design Mg alloys using the calculation of phase diagrams (CALPHAD) method, where the Gibbs energies of solution phases such as liquid, fcc, bcc, and hcp phases were described by the subregular solution model, whereas those of all the compounds were described by the sublattice model. The thermodynamic parameters describing Gibbs energies of the different phases in this database were evaluated by fitting the experimental data for phase equilibria and thermodynamic properties. On the basis of this database, a lot of information concerning stable and metastable phase equilibria of isothermal and vertical sections, molar fractions of constituent phases, the liquidus projection, etc., can be predicted. This database is expected to play an important role in the design of Mg alloys.展开更多
文摘In the article, an experiment is aimed at clarifying the transfer efficiency of the database in the cloud infrastructure. The system was added to the control unit, which has guided the database search in the local part or in the cloud. It is shown that the time data acquisition remains unchanged as a result of modification. Suggestions have been made about the use of the theory of dynamic systems to hybrid cloud database. The present work is aimed at attracting the attention of specialists in the field of cloud database to the apparatus control theory. The experiment presented in this article allows the use of the description of the known methods for solving important practical problems.
基金supported by the National Natural Science Foundation of China under grant nos.61772091,61802035,61962006,61962038,U1802271,U2001212,and 62072311the Sichuan Science and Technology Program under grant nos.2021JDJQ0021 and 22ZDYF2680+7 种基金the CCF‐Huawei Database System Innovation Research Plan under grant no.CCF‐HuaweiDBIR2020004ADigital Media Art,Key Laboratory of Sichuan Province,Sichuan Conservatory of Music,Chengdu,China under grant no.21DMAKL02the Chengdu Major Science and Technology Innovation Project under grant no.2021‐YF08‐00156‐GXthe Chengdu Technology Innovation and Research and Development Project under grant no.2021‐YF05‐00491‐SNthe Natural Science Foundation of Guangxi under grant no.2018GXNSFDA138005the Guangdong Basic and Applied Basic Research Foundation under grant no.2020B1515120028the Science and Technology Innovation Seedling Project of Sichuan Province under grant no 2021006the College Student Innovation and Entrepreneurship Training Program of Chengdu University of Information Technology under grant nos.202110621179 and 202110621186.
文摘An excellent cardinality estimation can make the query optimiser produce a good execution plan.Although there are some studies on cardinality estimation,the prediction results of existing cardinality estimators are inaccurate and the query efficiency cannot be guaranteed as well.In particular,they are difficult to accurately obtain the complex relationships between multiple tables in complex database systems.When dealing with complex queries,the existing cardinality estimators cannot achieve good results.In this study,a novel cardinality estimator is proposed.It uses the core techniques with the BiLSTM network structure and adds the attention mechanism.First,the columns involved in the query statements in the training set are sampled and compressed into bitmaps.Then,the Word2vec model is used to embed the word vectors about the query statements.Finally,the BiLSTM network and attention mechanism are employed to deal with word vectors.The proposed model takes into consideration not only the correlation between tables but also the processing of complex predicates.Extensive experiments and the evaluation of BiLSTM-Attention Cardinality Estimator(BACE)on the IMDB datasets are conducted.The results show that the deep learning model can significantly improve the quality of cardinality estimation,which is a vital role in query optimisation for complex databases.
基金The project supported by the National Natural Science Foundation of ChinaLNM,Institute of Mechanics,CAS
文摘A new theory on the construction of optimal truncated Low-Dimensional Dynamical Systems (LDDSs) with different physical meanings has been developed, The physical properties of the optimal bases are reflected in the user-defined optimal conditions, Through the analysis of linear and nonlinear examples, it is shown that the LDDSs constructed by using the Proper Orthogonal Decomposition (POD) method are not the optimum. After comparing the errors of LDDSs based on the new theory POD and Fourier methods, it is concluded that the LDDSs based on the new theory are optimally truncated and catch the desired physical properties of the systems.
文摘Most of the proposed concurrency control protocols for real time database systems are based on serializability theorem. Owing to the unique characteristics of real time database applications and the importance of satisfying the timing constraints of transactions, serializability is too strong as a correctness criterion and not suitable for real time databases in most cases. On the other hand, relaxed serializability including epsilon serializability and similarity serializability can allow more real time transactions to satisfy their timing constraints, but database consistency may be sacrificed to some extent. We thus propose the use of weak serializability(WSR) that is more relaxed than conflicting serializability while database consistency is maintained. In this paper, we first formally define the new notion of correctness called weak serializability. After the necessary and sufficient conditions for weak serializability are shown, corresponding concurrency control protocol WDHP(weak serializable distributed high priority protocol) is outlined for distributed real time databases, where a new lock mode called mask lock mode is proposed for simplifying the condition of global consistency. Finally, through a series of simulation studies, it is shown that using the new concurrency control protocol the performance of distributed real time databases can be greatly improved.
文摘In the context of a proliferation of DatabaseManagement Systems(DBMSs),we have envisioned and produced an OWL 2 ontology able to provide a high-level machine-processable description of the DBMSs domain.This conceptualization aims to facilitate a proper execution of various software engineering processes and database-focused administration tasks.Also,it can be used to improve the decision-making process for determining/selecting the appropriate DBMS,subject to specific requirements.The proposed model describes the most important features and aspects regarding the DBMS domain,including the support for various paradigms(relational,graph-based,key-value,tree-like,etc.),query languages,platforms(servers),plus running environments(desktop,Web,cloud),specific contexts—i.e.,focusing on optimizing queries,redundancy,security,performance,schema vs.schema-less approaches,programming languages/paradigms,and others.The process of populating the ontology with significant individuals(actual DBMSs)benefits from the existing knowledge exposed by free and open machine-processable knowledge bases,by using structured data fromWikipedia and related sources.The pragmatic use of our ontology is demonstrated by two educational software solutions based on current practices in Web application development,proving support for learning and experimenting key features of the actual semantic Web technologies and tools.This approach is also an example of using multiple knowledge from database systems,semanticWeb technologies,and software engineering areas.
文摘In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can enhance the performance of real-time concurrency control mechanism by reducing the number of transactions that might miss their deadlines, and compare the performance of validation concurrency control protocol with that of HP2PL(High priority two phase locking) protocol and OCC-TI-WAIT-50(Optimistic concurrency control-time interval-wait-50) protocol under shared-disk architecture by simulation. The simulation results reveal that the protocol the author presented can effectively reduce the number of transactions restarting which might miss their deadlines and performs better than HP2PL and OCC-TI-WAIT-50. It works well when arrival rate of transaction is lesser than threshold. However, due to resource contention the percentage of missing deadline increases sharply when arrival rate is greater than the threshold.
基金supported by the National Natural Science Foundation of China (No. 81201322)the Priority Project on Infectious Disease Control and Prevention 2011ZX10004-001 and 2013ZX10003006-002 by the Chinese Ministry of Science and Technology and the Chinese Ministry of Healththe Foundation of State Key Laboratory for Infectious Disease Prevention and Control (Grand No. 2011SKLID303)
文摘Secretion systems, macromolecules to pass which can mediate the across cellular membranes, are essential for virulent and genetic material exchange among bacterial species[1]. Type IV secretion system (T4SS) is one of the secretion systems and it usually consists of 12 genes: VirB1, VirB2 ...VirB11, and VirD4[2]. The structure and molecular mechanisms of these genes have been well analyzed in Gram-negative strains[3] and Gram-positive strains were once believed to be lack of T4SS. However, some recent studies revealed that one or more virB/D genes also exist in some kinds of Gram-positive bacteria and play similar role, and form a T4SS-like system[3]. The VirBl-like, VirB4, VirB6, and VirD4 genes were identified in the chromosome of Gram-positive bacterium Streptococcus suis in our previous studies and their role as important mobile elements for horizontal transfer to recipients in an 89 K pathogenicity island (PAl) was demonstrated[45]. However, their structure and molecular mechanisms in other strains, especially in Gram-positive strains, are remained unclear.
基金Project(20030533011)supported by the National Research Foundation for the Doctoral Program of Higher Education of China
文摘A DMVOCC-MVDA(distributed multiversion optimistic concurrency control with multiversion dynamic adjustment)protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments.At the mobile hosts,all transactions perform local pre-validation.The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle.Transactions that survive in local pre-validation must be submitted to the server for local final validation.The new protocol eliminates conflicts between mobile read-only and mobile update transactions,and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions.Mobile read-only transactions can be committed with no-blocking,and respond time of mobile read-only transactions is greatly shortened.The tolerance of mobile transactions of disconnections from the broadcast channel is increased.In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants.The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate,restart rate,commit rate.Under high work load(think time is 1s)the miss rate of DMVOCC-MVDA is only 14.6%,is significantly lower than that of other protocols.The restart rate of DMVOCC-MVDA is only 32.3%,showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions.And the commit rate of DMVOCC-MVDA is up to 61.2%,which is obviously higher than that of other protocols.
基金the National Natural Science Foundation of China and the Commission of Science,Technokgy and Industry for National Defense
文摘This paper formally defines and analyses the new notion of correctness called quasi serializability, and then outlines corresponding concurrency control protocol QDHP for distributed real-time databases. Finally, through a series of simulation studies, it shows that using the new concurrency control protocol the performance of distributed real-time databases can be much improved.
基金Project supported by National Natural Science Foundation ofChina (Grant No .60203017) Defense Pre-research Projectof the"Tenth Five-Year-Plan"of China (Grant No .413150403)
文摘Recovery performance in the event of failures is very important for distributed real-time database systems. This paper presents a time-cognizant logging-based crash recovery scheme (TCLCRS) that aims at distributed real-time databases, which adopts a main memory database as its ground support. In our scheme, each site maintains a real-time log for local transactions and the subtransactions, which execute at the site, and execte local checkpointing independently. Log records are stored in non-volatile high- speed store, which is divided into four different partitions based on transaction classes. During restart recovery after a site crash, partitioned crash recovery strategy is adopted to ensure that the site can be brought up before the entire local secondary database is reloaded in main memory. The partitioned crash recovery strategy not only guarantees the internal consistency to be recovered, but also guarantee the temporal consistency and recovery of the sates of physical world influenced by uncommitted transactions. Combined with two- phase commit protocol, TCLCRS can guarantee failure atomicity of distributed real-time transactions.
文摘This paper introduces a multi-granularity locking model (MGL) for concurrency control in object-oriented database system briefiy, and presents a MGL model formally. Four lockingscheduling algorithms for MGL are proposed in the paper. The ideas of single queue scheduling(SQS) and dual queue scheduling (DQS) are proposed and the algorithm and the performance evaluation for these two scheduling are presented in some paper. This paper describes a new idea of thescheduling for MGL, compatible requests first (CRF). Combining the new idea with SQS and DQS,we propose two new scheduling algorithms called CRFS and CRFD. After describing the simulationmodel, this paper illustrates the comparisons of the performance among these four algorithms. Asshown in the experiments, DQS has better performance than SQS, CRFD is better than DQS, CRFSperforms better than SQS, and CRFS is the best one of these four scheduling algorithms.
文摘Computer simulation for materials processing needs a huge database containing a great deal of various physical properties of materials. In order to employ the accumulated large data on materials heat treatment in the past years, it is significant to develop an intelligent database system. Based on the data mining technology for data analysis, an intelligent database web tool system of computer simulation for heat treatment process named as IndBASEweb-HT was built up. The architecture and the arithmetic of this system as well as its application were introduced.
基金SponsoredbytheNationalNaturalScienceofFoundationofChina (No .19990 5 10 )andNaturalScienceFoundationofHeilongjiangprovince
文摘Oil film forces are usually obtained for dynamic analysis of a journal bearing system by using the approximate analytical formula or solving the Reynolds equation. None of them is suitable for rotor system bifurcation analysis because they are either of poor accuracy or time consuming. Oil film forces database is proposed is to transform the journal speed variation range in radial and circumferential directions from (-∞,+∞) to (-1, +1). The numerical results show the suggested method is much more effective. And sub harmonic, quasi periodic and chaotic vibrations are predicted for a range of speed and unbalance parameters.
基金sponsored by the Natural Science Foundation of China(Grant No.41101514)111 Project+4 种基金New Faculty Start-up Funds of Sichuan University(Grant No.JS20100324507093)the New Century Talent Support Program of the Ministry of Education of China(Grant No.NCET10-0578)International Science & Technology Cooperation Program(Grant No.2012DFG91520)Key Projects of National Science & Technology Pillar Program in the 12th 5 Years(Grant No.2013BAJ11B01)the Jiuzhaigou International Laboratory of Sichuan University,the GIS Center, and the Sustainability Research and Education Center of Sichuan University
文摘The objective of this paper is to develop a GIS(Geographic Information System) database for Jiuzhaigou National Nature Reserve(Jiuzhaigou,hereafter) in China and demonstrate its application as a research tool.A cost-effective procedure was developed to compile a variety of geographical and biological data of the study area in terms of popular GIS format such as shape files.These files were further calibrated and validated using field surveys data.The developed GIS database was used to quantify the distributions of the wildlife(amphibians,mammals,and birds) using the distances of the wildlife to the centerline of the bus-tour routes.The Pearson correlation coefficient was used to quantify the correlation in space between pairs of different wildlife using the number of habitats for given space contexts.An ArcObject-based macro was developed to perform the analysis.The results showed the majority of the habitats of wildlife are located in the proximity of the tour-bus routes with an average distance ranging from 564 to 894 m depending on types of wildlife.This indicates a possibility of the disturbance to the wildlife by human activities.The correlation coefficient of the wildlife ranged from 0.36 to 0.64 depending on pairs of wildlife,indicating some correlations in space.However,due to the limited sample size,the statistical significances need to be further investigated.This paper has successfully demonstrated the use of the GIS-based database as a research tool for environmental study.
基金supported by the Major State Basic Research and Development Program of China (No.2007CB613807)the Doctorate Foundation of Northwestern Polytechnical University (CX201105)+1 种基金the Program for New Century Excellent Talents in Chinese Universities (No.NCET-07-0696)the fund of the State Key Laboratory of Solidification Processing in NWPU (No.35-TP-2009)
文摘The selection of titanium alloys has become a complex decision-making task due to the growing number of creation and utilization for titanium alloys,with each having its own characteristics,advantages,and limitations.In choosing the most appropriate titanium alloys,it is very essential to offer a reasonable and intelligent service for technical engineers.One possible solution of this problem is to develop a database system(DS) to help retrieve rational proposals from different databases and information sources and analyze them to provide useful and explicit information.For this purpose,a design strategy of the fuzzy set theory is proposed,and a distributed database system is developed.Through ranking of the candidate titanium alloys,the most suitable material is determined.It is found that the selection results are in good agreement with the practical situation.
基金supported by the National Natural Science Foundation of China (Grant No. 50539010, 50539110, 50579010, 50539030 and 50809025)
文摘To improve the effectiveness of dam safety monitoring database systems, the development process of a multi-dimensional conceptual data model was analyzed and a logic design wasachieved in multi-dimensional database mode. The optimal data model was confirmed by identifying data objects, defining relations and reviewing entities. The conversion of relations among entities to external keys and entities and physical attributes to tables and fields was interpreted completely. On this basis, a multi-dimensional database that reflects the management and analysis of a dam safety monitoring system on monitoring data information has been established, for which factual tables and dimensional tables have been designed. Finally, based on service design and user interface design, the dam safety monitoring system has been developed with Delphi as the development tool. This development project shows that the multi-dimensional database can simplify the development process and minimize hidden dangers in the database structure design. It is superior to other dam safety monitoring system development models and can provide a new research direction for system developers.
文摘Database Security and Protection System (DSPS) is a security platform for fighting malicious DBMS. The security and performance are critical to DSPS. The authors suggested a key management scheme by combining the server group structure to improve availability and the key distribution structure needed by proactive security. This paper detailed the implementation of proactive security in DSPS. After thorough performane analysis, the authors concluded that the performance difference between the replicated mechanism and proactive mechanism becomes smaller and smaller with increasing number of concurrent connections ; and that proactive security is very useful and practical for large, critical applications.
文摘Data-Base Management System (DBMS) is the current standard for storing information. A DBMS organizes and maintains a structure of storage of data. Databases make it possible to store vast amounts of randomly created information and then retrieve items using associative reasoning in search routines. However, design of databases is cumbersome. If one is to use a database primarily to directly input information, each field must be predefined manually, and the fields must be organized to permit coherent data input. This static requirement is problematic and requires that database table(s) be predefined and customized at the outset, a difficult proposition since current DBMS lack a user friendly front end to allow flexible design of the input model. Furthermore, databases are primarily text based, making it difficult to process graphical data. We have developed a general and nonproprietary approach to the problem of input modeling designed to make use of the known informational architecture to map data to a database and then retrieve the original document in freely editable form. We create form templates using ordinary word processing software: Microsoft InfoPath 2007. Each field in the form is given a unique name identifier in order to be distinguished in the database. It is possible to export text based documents created initially in Microsoft Word by placing a colon at the beginning of any desired field location. InfoPath then captures the preceding string and uses it as the label for the field. Each form can be structured in a way to include any combination of both textual and graphical fields. We input data into InfoPath templates. We then submit the data through a web service to populate fields in an SQL database. By appropriate indexing, we can then recall the entire document from the SQL database for editing, with corresponding audit trail. Graphical data is handled no differently than textual data and is embedded in the database itself permitting direct query approaches. This technique makes it possible for general users to benefit from a combined text-graphical database environment with a flexible non-proprietary interface. Consequently, any template can be effortlessly transformed to a database system and easily recovered in a narrative form.
基金This study was financially supported by the National Natural Science Foundation of China and Chongqing Science and Technology Commission.
文摘The Mg-Al-Zn-Y-Ce system is one of the key systems for designing high-strength Mg alloys. The purpose of the present article is to develop a thermodynamic database for the Mg-Al-Zn-Y-Ce multicomponent system to design Mg alloys using the calculation of phase diagrams (CALPHAD) method, where the Gibbs energies of solution phases such as liquid, fcc, bcc, and hcp phases were described by the subregular solution model, whereas those of all the compounds were described by the sublattice model. The thermodynamic parameters describing Gibbs energies of the different phases in this database were evaluated by fitting the experimental data for phase equilibria and thermodynamic properties. On the basis of this database, a lot of information concerning stable and metastable phase equilibria of isothermal and vertical sections, molar fractions of constituent phases, the liquidus projection, etc., can be predicted. This database is expected to play an important role in the design of Mg alloys.