A distributed turbo codes（ DTC） scheme with log likelihood ratio（ LLR）-based threshold at the relay for a two-hop relay networks is proposed. Different from traditional DTC schemes,the retransmission scheme at the...A distributed turbo codes（ DTC） scheme with log likelihood ratio（ LLR）-based threshold at the relay for a two-hop relay networks is proposed. Different from traditional DTC schemes,the retransmission scheme at the relay,where imperfect decoding occurs,is considered in the proposed scheme. By employing a LLR-based threshold at the relay in the proposed scheme,the reliability of decoder-LLRs can be measured. As a result,only reliable symbols will be forwarded to the destination and a maximum ratio combiner（ MRC） is used to combine signals received from both the source and the relay. In order to obtain the optimal threshold at the relay,an equivalent model of decoderLLRs is investigated,so as to derive the expression of the bit error probability（ BEP） of the proposed scheme under binary phase shift keying（ BPSK） modulation. Simulation results demonstrate that the proposed scheme can effectively mitigate error propagation at the relay and also outperforms other existing methods.展开更多
This paper presents an efficient recovery scheme suitable for real-time mainmemory database. In the recovery scheme, log records are stored in non-volatile RAM which is dividedinto four different partitions based on t...This paper presents an efficient recovery scheme suitable for real-time mainmemory database. In the recovery scheme, log records are stored in non-volatile RAM which is dividedinto four different partitions based on transaction types. Similarly, a main memory database isdivided into four partitions based data types. When the using ratio of log store area exceeds thethreshold value, checkpoint procedure is triggered. During executing checkpoint procedure, someuseless log records are deleted. During restart recovery after a crash, partition reloading policyis adopted to assure that critical data are reloaded and restored in advance, so that the databasesystem can be brought up before the entire database is reloaded into main memory. Therefore downtime is obvionsly reduced. Simulation experiments show our recovery scheme obviously improves thesystem performance, and does a favor to meet the dtadlints of real-time transactions.展开更多
成像测井系统中的主控模块主要包括刻度、测井、回放、重测井等子模块．系统的测井主控采用双进程、多线程的设计方案，一个进程是采集管理器，它主要负责和前端机进行通讯．另一个进程就是主控软件，其中多个线程共享同一个内存空间，...成像测井系统中的主控模块主要包括刻度、测井、回放、重测井等子模块．系统的测井主控采用双进程、多线程的设计方案，一个进程是采集管理器，它主要负责和前端机进行通讯．另一个进程就是主控软件，其中多个线程共享同一个内存空间，线程之间的通讯方便．系统采用实时抢占式调度控制方式，可及时处理在测并过程中的紧急事例和数据采集．根据 Windows NT 中的 DLL 技术和面向对象中的动态联编技术，采用动态添加新仪器的设计思想，设计了测井仪器类及动态添加机制，可以将各种测井仪器的动态链接库动态安装到测井系统中，达到动态添加新仪器的目的．展开更多
文摘A distributed turbo codes（ DTC） scheme with log likelihood ratio（ LLR）-based threshold at the relay for a two-hop relay networks is proposed. Different from traditional DTC schemes,the retransmission scheme at the relay,where imperfect decoding occurs,is considered in the proposed scheme. By employing a LLR-based threshold at the relay in the proposed scheme,the reliability of decoder-LLRs can be measured. As a result,only reliable symbols will be forwarded to the destination and a maximum ratio combiner（ MRC） is used to combine signals received from both the source and the relay. In order to obtain the optimal threshold at the relay,an equivalent model of decoderLLRs is investigated,so as to derive the expression of the bit error probability（ BEP） of the proposed scheme under binary phase shift keying（ BPSK） modulation. Simulation results demonstrate that the proposed scheme can effectively mitigate error propagation at the relay and also outperforms other existing methods.
文摘This paper presents an efficient recovery scheme suitable for real-time mainmemory database. In the recovery scheme, log records are stored in non-volatile RAM which is dividedinto four different partitions based on transaction types. Similarly, a main memory database isdivided into four partitions based data types. When the using ratio of log store area exceeds thethreshold value, checkpoint procedure is triggered. During executing checkpoint procedure, someuseless log records are deleted. During restart recovery after a crash, partition reloading policyis adopted to assure that critical data are reloaded and restored in advance, so that the databasesystem can be brought up before the entire database is reloaded into main memory. Therefore downtime is obvionsly reduced. Simulation experiments show our recovery scheme obviously improves thesystem performance, and does a favor to meet the dtadlints of real-time transactions.
文摘成像测井系统中的主控模块主要包括刻度、测井、回放、重测井等子模块．系统的测井主控采用双进程、多线程的设计方案，一个进程是采集管理器，它主要负责和前端机进行通讯．另一个进程就是主控软件，其中多个线程共享同一个内存空间，线程之间的通讯方便．系统采用实时抢占式调度控制方式，可及时处理在测并过程中的紧急事例和数据采集．根据 Windows NT 中的 DLL 技术和面向对象中的动态联编技术，采用动态添加新仪器的设计思想，设计了测井仪器类及动态添加机制，可以将各种测井仪器的动态链接库动态安装到测井系统中，达到动态添加新仪器的目的．
