HNIW与ニ甲基甲酰胺、ニ甲基亚砜分子加合物的研究

在二甲基甲酰胺( DMF)／水、二甲基亚砜(DMSO)／水体系中制备了六硝基六氮杂异伍兹烷( HNIW)与DMF、DMSO的加合物;由红外光谱分析得出,HNIW与DMF分子加合物中的HNIW为α型,HNIW与DMSO分子加合物中的HNIW为ε型;由加合物的1HNMR图可以得出,HNIW与DMF、DMSO分子组成比均为1:2;对HNIW、HNIW与DMF加合物、HNIW与DMSO加合物进行热重一差热分析发现,HNIW和DMF、DMSO形成加合物后,热稳定性降低,DMSO明显加速HNIW的热分解。     

基于ANUGA和SWMM耦合模型的车陂涌流域内涝模拟分析

为探究设计暴雨雨峰位置对城市内涝的响应规律,以广州车陂涌流域某片区为研究区,基于ANUGA和SWMM构建耦合模型AGSWM,采用实测降雨的流量和内涝数据对AGSWM进行验证,并对不同雨峰位置的设计暴雨情景进行了内涝模拟与分析。结果表明：耦合模型AGSWM具有良好的模拟精度,能够较好地反映车陂涌内涝时空演进过程;在低重现期后峰情景和高重现期中峰情景下,内涝积水总量、总淹没面积、重度内涝等级的淹没面积和重度内涝等级的易涝点最大水深较大;在低重现期前峰情景、高重现期后峰情景下,积水峰现延迟时间较长。     

并行实时数据库系统多版本两阶段封锁并发控制协议

提出了适用于无共享结构并行数据库实时多版本两阶段封锁并发控制协议．该协议具有多版本并发控制机制与两阶段封锁机制的优点，使用如下策略以减少延误截止时间事务数量:若冲突集中有比持锁事务Ti优先级高的事务，且Ti重启动不会延误截止时间，则Ti重启动，冲突集中优先级最高的事务获得锁；否则，冲突集中其他事务等待．通过仿真模拟，与HP2PL和OCC-TI-WAIT-50协议进行比较，结果表明：在正常负载、长短事务混合的情况下，并发控制协议能有效地降低事务延误截止时间率、事务重启动率，减少同步开销，该协议比HP2PL和OCC-TI-WAIT-50协议性能更好，同时具有较强的扩展性．     

多版本两阶段封锁并发控制协议性能研究

在并行实时数据库中，并发控制协议不仅要满足数据库一致性约束，而且要满足时间约束。本文提出了实时多版本两阶段封锁并发控制协议，它能有效地减少延误截止时间事务数量。作者通过仿真模拟，在共享磁盘体系结构下与HP2PL和OCC-TI-WAIT-50协议进行了比较。实验结果表明，该协议比HP2PL和OCC-TI-WAIT-50协议性能更好。     

Validation concurrency control protocol in parallel real-time database systems

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.     

Scheduling transactions in mobile distributed real-time database systems

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 ls） 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.     

移动计算环境中实时嵌套事务并发控制协议的研究

提出了移动计算环境中多版本乐观并发控制协议(MultiversionOptimisticConcurrencyControl,MVOCC)处理移动实时嵌套事务.协议消除了只读事务和更新事务之间冲突,通过动态调整事务串行次序,避免不必要的事务重启动.只读事务在移动主机处理,只读事务的响应时间大大改善.事务有效性检查分两级局部有效性检查和全局有效性检查.局部有效性检查在移动主机进行.通过局部有效性检查的事务提交到服务器进行全局有效性检查.如此早地检测数据冲突,节省了处理和通信资源.通过模拟仿真,对协议进行了性能测试,并与OCC-TI-WAIT50和HP2PL协议进行了比较.实验结果表明该协议要优于其它协议.协议不但能有效地降低事务的重启动率和延误截止时间率,而且改善只读事物的响应时间.     

移动自组网中高效层次化一致性协议

提出移动自组网中高效的层次化一致性协议,其移动自组网系统模型中最多有f(f相似文献   

移动广播环境中实时事务处理性能研究

提出了移动广播环境中MVOCC-DA-2PV(Multiversion Optimistic Concurrency Control with Dynamic Adjustment of serialization order using Two-Phase Validation)并发控制协议。移动实时事务处理分两阶段进行。第一阶段在移动主机(MobileHosts,MHs)上处理,第二阶段在服务器上处理。移动主机(MHs)上所有移动事务执行部分向后有效性确认,与在服务器提交事务进行有效性确认。如果移动事务通过MH上部分有效性确认,提交到服务器进行最终有效性确认。如此早地检测数据冲突,节省了处理和通信资源。协议消除了移动只读事务和移动更新事务的冲突,使用多版本动态调整串行次序技术,避免了不必要的事务重启动。降低了移动只读事务的响应时间。通过模拟仿真,对MVOCC-DA-2PV协议进行了性能测试,并与PVTO和HP2PL进行了比较。实验结果表明MVOCC-DA-2PV并发控制协议要优于其它协议。