Coordinated Recovery of Middleware Services:A Framework and Experiments

Being the most popular runtime infrastructure for distributed systems, middleware can be viewed as a collection of common services. Since the development, deployment and maintenance of distributed systems rely largely on middleware services, the failure of middleware services puts a significant impact on the reliability and availability of the whole system. Though recovery-based fault tolerance is an effective way to improve the reliability of middleware services, it is far away from practice mainly because of the high complexity and cost of the recovery of correlated failures between interdependent services. In this paper,a framework for detecting and recovering the correlated failures of middleware services in an automated way is presented. First, the problem is investigated from two perspectives, i.e.,analyzing the role and impact of middleware services and illustrating a set of correlated failures in J2EE standard services as motivating examples. Then, a general coordinated recovery model is constructed with the elements necessary and su±cient for detecting and recovering correlated failures in middleware services. The supporting framework is demonstrated on three J2EE application servers, i.e., PKUAS, JBoss and JOnAS, one by one without fundamental modifications. Finally, based on the three enhanced application servers, many cases on J2EE common services, including the transaction service, database service, naming and directory service, security service and messaging service, are studied. The experiment results show the effectiveness and applicability of the framework presented in this paper.     

金钢石膜表面抛光与平整技术进展

综述了金刚石膜抛光与平整技术，例如研磨、热化学抛光、离子束抛光、化学机械抛光、等离子抛光、激光抛光等方法的优点与不足，重点分析厚度较小（约几微米）的金刚石薄膜抛光与平整的可行途径。     

多天线智能分集接收系统的设计

通过对多天线分集接收技术的分析,针对多径传输引起的衰落,提出一种多天线分集接收方法。本文将智能控制处理技术与空间分集接收天线技术相结合,通过智能控制选择合并算法。通过无线遥控接收机进行实验,取得良好接收效果。     

Influencing mechanism and interaction of muscovite on thermal decomposition of ammonium polyphosphate

The interaction mechanism and phase evolution of ammonium polyphosphate(APP)mixed with muscovite(APP/muscovite)were studied by TG,XRD and SEM,respectively,during heating.When the temperature is not higher than 300 ℃,muscovite has no effect on the thermaldecomposition of APP,and the initialdecomposition temperature of APP/muscovite at 283 ℃ is basically the same as the APP at 295 ℃,and the main thermaldecomposition products are polyphosphoric acid and NH_4H_2PO_4 at 300 ℃.The polyphosphoric acid,the decomposition products of APP,can enable K and Siout of muscovite and interact with muscovite chemically to generate Al_2O_3·2SiO_2,α-SiO_2 and phosphates(AlPO_4 and K_5P_3O_(10))compounds during 400 ℃-800 ℃,which own obvious adhesive phenomenon and porous structure with the apparent porosity of 58.4%.Further reactions between phosphates other than reactions among Al_2O_3·2SiO_2 and α-SiO_2 can generate KAlP_2O_7 at 1 000 ℃ and the density of residualproduct is improved by low melting point phosphate filling pore to form relatively dense structure and decrease the apparent porosity to 44.4%.The flame resistant and self-supported ceramic materials are expected to enhance the fire-retarding synergistic effect between APP and muscovite.     

PAC投加对絮体破碎后再絮凝特性和颗粒去除的影响

为改善絮体破碎后的再絮凝能力,提高颗粒的去除效率,以西宁地区低温低浊水为研究对象,通过光学检测仪器及数学拟合方式,分析补投聚合氯化铝(PAC)对破碎后絮体粒径与分布、生长速率变化的影响,描述颗粒及浊度的去除效果.结果表明:随PAC补投量的升高,絮体粒径和生长速率均先增大后减小,各自达到峰值所需补投药量分别为4和6 mg/L;剩余浊度和颗粒数先降低后升高,最低时可分别降至0.79 NTU、90个·m L-1.补投2 mg/L药剂后,280~630μm絮体颗粒体积分数由22.85%增大到46.36%,4~35μm絮体颗粒体积分数由1.21%减小至0.19%,再絮凝后絮体平均粒径为400μm,大于未破碎前的370μm,粒径增长率为8.11%,絮体生长速率为77.26μm/min.补投PAC可促进絮体破碎后的再絮凝,提高浊度及颗粒数的去除效果,可有效改善实际工程絮凝工艺效果.     

Effects of COD to Phosphorus Ratios on the Metabolism of PAOs in Enhanced Biological Phosphorus Removal with Different Carbon Sources

To elucidate the phosphorus removal and metabolism under various COD / P ratio,a sludge highly enriched in PAOs was used to investigate the impacts of COD / P in batch tests under different carbon supply conditions. Acetate,propionate and a mixture of acetate and propionate at a ratio of 3 ∶ 1( COD basis) was used as carbon sources with the COD / P of 20,15,10 and 5. 0 g COD /gP,respectively. The minimum COD / P ratios for complete P removal were found to be 8. 24 g COD /gP for acetate,11. 40 g COD /gP for propionate and9. 10 g COD /gP for the 3 ∶ 1 mixture of acetate and propionate. Converted to a mass basis,all three cases had a very similar ratio of 7. 7 g VFA /gP,which represented a useful guide for operation of EBPR plants to identify possible shortages in VFAs. The trend in PHV accumulation during the anaerobic period along with the decrease of COD / P ratios suggested that,PAOs may use the TCA pathway for anaerobic VFA uptake to maintain the required NADH production with reduced glycogen degradation. During the aerobic phase,the glycogen pool was reduced but remained enough compared to the requirement for anaerobic VFA uptake,and the synthesis and degradation of glycogen was not the inhibition factor of PAOs.     

分数阶区间系统的鲁棒稳定性分析

由于实际的物理系统常会存在各种不确定结构,这些不确定结构给系统的稳定性分析带来了困难和一定的影响,因此对这类带有不确定结构的分数阶系统控制问题的研究,具有广泛的实际应用意义。本文主要针对带有区间不确定性的分数阶控制系统,分析了该系统的鲁棒稳定性问题,首先将区间矩阵用分式线性变换(LFT)表示,然后基于分析得出了此类系统鲁棒稳定的充分必要条件。并给出两个数值算例阐释该方法,仿真结果表明了该方法的有效性。     

Reservoir Operation Incorporating Hedging Rules and Operational Inflow Forecasts

Reservoir operation incorporating a naïve hedging strategy and operational inflow forecasting is studied in this paper. Gridded precipitation forecasts from climate model, ECHAM4.5, are used as potential predictors for reservoir inflow forecasting. In building a statistical predicting model, principal component analysis (PCA) is used to reduce the dimension of the regression model. Performance evaluation indices, including water supply satisfaction ratio, environmental flow satisfaction ratio, end-of-month storage satisfaction ratio and flood prevention capacity index, are defined. Three scenarios where a naïve hedging operation rule under different set of reservoir inflow are investigated. These are evaluated for a water supply reservoir, Falls Lake Reservoir, at Neuse River in the southeast United State. Reservoir simulation with monthly average inflow serves as a benchmark. The utility of operational inflow forecasts is quantified by the improvements of performance indices. Results show that reservoir operation under perfect inflow forecasting has the highest values for most indices. Compared to climatology, operational inflow forecasts result in higher index values. Among all the performance indices, end-of-month storage satisfaction ratio is the most sensitive index to inflow information. Limitation of this study and further work is also discussed.     

基于FPGA和瞬时无功功率理论的谐波检测方法

在本文中讨论了瞬时无功功率理论对电网的三相对称电流的变换,当电网电压为正弦波时,有功电流iP(无功电流iq)只含有6n次谐波(n为正整数),并由此设计出积分算法低通数字滤波器。该滤波器能有效的滤除6n次谐波。将该方案用FPGA器件加以实现,设计中采用了流水线结构的滤波器,大大的提高了FPGA的运算速度并节省了面积。实验仿真证明:这种检测算法可以灵活的处理综合的面积和速度的约束关系,使最后设计达到最优,具有较高的实用价值。     

热处理对铁素体不锈钢组织和性能的影响

研究了不同热处理工艺对铁素体不锈钢的组织与性能的影响.结果表明 铁素体不锈钢固溶处理时,温度在900 ℃以下组织无明显变化,其硬度随着温度的上升变化缓慢;900 ℃左右发生再结晶,硬度显著降低;在475 ℃热处理后析出物增多,硬度增加,耐腐蚀性能严重下降,即有明显475 ℃脆性现象.