分布事务监控器集群框架研究

介绍了在分布事务监控器OnceTX中采用的服务器/集群管理器/应用域管理器的三层集群结构,并给出了两级负载平衡策略和自适应的域间拓扑结构管理算法。它们已在OnceTX中实现,并达到了预期的目的。

pessimistic predicate/transform model for long running business processes

Many business processes in enterprise applications are both long running and transactional in nature. However, no current transaction model can provide full transaction support for such long running business processes. This paper proposes a new transaction model, the pessimistic predicate/transform (PP/T) model, which can provide full transaction support for long running business processes. A framework was proposed on the enterprise JavaBeans platform to implement the PP/T model. The framework enables application developers to focus on the business logic, with the underlying platform providing the required transactional semantics. The development and maintenance effort are therefore greatly reduced. Simulations show that the model has a sound concurrency management ability for long running business processes.

事务处理技术综述

事务处理技术是保证信息可靠性和一致性的重要技术。事务是具有ACID(atomicity, consistency, isolationanddurability)特性的原子操作序列，它的概念最早来湖泊于数据库管理系统，用来保证应用程序对数据库访问的一致性和可靠性。在早期应用中，商用DBMS系统内部集成的事务管理器提供应用所需的事务处理功能。随着网络技术的发展以及应用需求的变化，以往集中式应用演化发展为网络分布应用，数据和处理分布在不同的计算机上。此时事务管理功能由专门的中间件（例如事务监控器）提供，事务处理技术也发展为分布式事务处理。

高性能可扩展分布事务服务的研究和实现

分布事务服务是应用服务器的关键服务之一，其处理效率直接影响应用服务器的性能．本文主要讨论J2EE框架下分布事务管理器ISTX的设计，介绍了为获得良好的可扩展性和可移植性而采用的技术；同时讨论了ISTX的性能优化策略及其实现．实验数据表明，ISTX的高性能设计在保证可靠性的前提下，较大程度地提高了分布事务服务的性能．

分布事务服务的一致性测试

作为J2EE应用服务器重要组成部分的分布事务管理器主要用于提供分布环境下的事务处理能力。文章拓宽了协议一致性测试的理论和技术的应用范围，探讨了分布事务服务的一致性测试，也给出了分布事务服务的形式化描述和非荃于经验的测试序列的生成方案。

分布事务管理器的性能优化

作为应用服务器重要组成部分的分布管理器主要用于提供分布环境下的事务处理能力,它的性能是制约应用服务器上分布事务吞吐能力的重要因素.讨论了在J2EE应用服务器框架下如何进行分布事务管理器的性能优化,同时给出了分布事务管理器ISTX的性能优化实现.实验数据表明,对ISTX的性能优化能在保证分布事务可靠性的前提下,较大幅度地提高了分布事务处理的性能.

移动数据库系统乐观事务处理策略

在移动数据库系统中 ,计算平台的移动性、频繁的断接性以及长事务等特性使得传统的事务处理模式不再适用 .为了解决移动数据库中的事务处理问题 ,提出了一种新的移动事务处理模型——乐观两阶段提交移动事务模型 ( O2 PC-MT) .该模型采用乐观并发控制与两阶段提交协议相结合的方法 ,对移动事务的长事务特性提供了灵活与有效的支持 ;此外 ,该模型允许移动计算机分多次发送事务操作 ,且在事务执行的过程中可以任意移动 ,从而提供了对交互式事务及随意移动性的支持 .实验结果表明 ,与基于两段锁协议及其变形的其它移动事务处理模型相比 ,O2 PC-MT提高了系统的事务吞吐率并改善了系统的总体性能

Single mode Er-doped pi-phase-shifted distributed feedback fibre grating laser

A novel method incorporating the shielded method and the post-processing method has been proposed to fabricate the pi-phase-shilted fibre grating. Then an Er-doped pi-phase-shifted distributed feedback fibre grating laser has been fabricated using the grating. The laser threshold is 20 mW. When pumped with 90 mW light at 980 nm, the laser gives an output of 1.1 mW. Its signal-to-noise ratio is better than 60 dB. It is demonstrated that the laser is single mode operation by means of a Fabry-Perot scanning interferometer.

Experimental and numerical study on AlGaInAs/AlGaAs distributed feedback lasers with GaInP gratings

Ridge-waveguide AlGaInAs/AlGaAs distributed feedback lasers with lattice-matched GaInP gratings were fabricated and their light-current characteristics, spectrum and far-field characteristics were measured. On the basis of our experimental results we analyze the effect of the electron stopper layer on light-current performance using the commercial laser simulation software PICS3D. The simulator is based on the self-consistent solution of drift diffusion equations, the Schrodinger equation, and the photon rate equation. The simulation results suggest that, with the use of a 80 nm-width p-doped Al0.6GaAs electron stopper layer, the slope efficiency can be increased and the threshold current can be reduced by more than 10 mA.

Interface of wet oxidized AlGaAs/GaAs distributed Bragg reflectors

The interface of wet oxidized Al0.97Ga0.03As/GaAs in a distributed Bragg reflector (DBR) structure has been studied by means of transmission electron microscopy and Raman spectroscopy. With the extension of oxidation time, the oxide/GaAs interfaces are not abrupt any more. There is an amorphous film near the oxide/GaAs interface, which is Ga2O3 related to the prolonged heating. In the samples oxidized for 10 and 20 min, there are some fissures along the oxidized AlGaAs/GaAs interfaces. In the samples oxidized or in situ annealed for long time, no such fissures are present due to the complete removal of the volatile products.