云平台下基于截止时间的自适应调度策略

针对在共享集群中进行任务调度时,无法兼顾任务的响应速度与任务完成时间的问题,提出一种基于截止时间的自适应调度算法。该算法以用户提交的截止时间为依据,根据任务的执行进度自适应地分配适当的计算资源。不同于传统调度方式里由用户提交固定资源参数,该算法在资源约束的情况下会对优先级高的任务进行抢占式调度以保证服务质量（QoS）,并在抢占过程结束后额外分配资源补偿被抢占的任务。在Spark平台进行的任务调度实验结果显示,与另一种资源协调者（YARN）框架下的调度算法相比,所提算法能严格地控制短任务的响应速度,并使长作业的任务完成时间缩短35%。     

场站飞行保障数据可视化平台设计与应用

为提升航空兵场站信息化建设过程中的数据应用与管理能力,提出了一种基于Spark的场站飞行保障大数据可视化平台.以场站信息化系统和物联网络数据采集数据为基础,利用Spark计算引擎集成Kafka消息队列,使用Hive完成数据列表库的建立和存储,基于Spark RDD和Spark SQL完成数据预处理与交互,并选择Vue框架嵌入ECharts组件完成前端数据可视化呈现,并最终对设计方案进行了实现与应用.相较于当前业务隔离的信息系统建设模式,平台具备更高的数据融合与处理分析能力,能够更好地实现场站飞行保障数据价值.     

基于 Spark 平台的网络游戏用户流失预测方法

随着移动互联网的广泛普及,国内网络游戏市场日趋饱和,游戏公司获得新用户的成本不断增加,如何预防存量用户的流失已经成为市场营销的重心。提出了一种基于Spark平台的网络游戏用户流失预测方法,基于一个真实游戏日志数据对用户进行了流失预测。首先,从日志数据中抽取和计算了用户特征;随后,按权重选取了一组重要特征;最后,以特征为输入、流失与否为输出进行了二分类建模。综合比较了随机森林、支持向量机、多层感知机、梯度提升决策树和逻辑回归等6种常见分类算法。实验结果表明,随机森林算法表现最优,模型预测精度达到91%。     

智能电网环境下电能计量大数据智能多维分析

针对目前现有的电能计量数据分析系统处理效率低下、计算周期过长和性能差等问题,设计出一套基于大数据技术的计量装置智能多维分析系统。该系统SQL分析通过Spark SQL实现,来弥补复杂HQL转换成Map Reduce任务后计算时间长的问题;数据采集预处理方面采用基于合区聚合法ETL技术,解决了传统ETL技术处理效率差的问题;多维分析方面则采用基于关联规则的What-if分析方法,解决了传统多维分析性能差的问题。实验表明,该方案具有效率高、编程简单、易操作、性能好等优点,保证了电能计量数据分析系统稳定性。     

Reaction mechanism of methane activation using non-equilibrium pulsed discharge at room temperature

The reaction mechanism of methane activation using non-equilibrium pulsed discharge was largely clarified from the emission spectroscopic study and experiments with higher hydrocarbons and some kinds of isotopes. The strong emission of atomic carbon and C₂ swan band system was observed as well as H Balmer series emission. This indicates that methane was highly dissociated into C and H by electron impact, which is consistent with the result of high C₂D₂ composition in produced acetylene when the mixture of CH₄ and D₂ was fed into discharge region. High electron energy contributed to produce atomic carbon directly from methane, and high electron density promoted the dehydrogenation from CH₃, CH₂ and CH to produce atomic carbon consecutively. The reason for the high selectivity to C₂H₂ was the high concentration of CH or C₂ formed from atomic carbon, and the repetition mechanism of decomposition and recombination among C, CH, C₂ and C₂H₂.     

放电等离子烧结工艺制备Ti_2AlC材料的研究

以元素粉钛、铝、碳为原料 ,采用放电等离子烧结工艺在 1 1 0 0℃的温度下成功地制备了高纯、致密Ti2 AlC材料。合成材料的X -射线衍射 (XRD)和扫描电镜 (SEM)分析的结果表明 :多晶体Ti2 AlC形貌为板状结晶 ,晶粒大小平均约为 2 0 μm ,厚度在 3～ 5 μm。     

机械合金化Ti/Al合金的制备

采用多维摆动式球磨机机械合金化Ti/Al二元粉末,研究了机械合金化过程中粉末结构的变化。Ti/Al混合粉末经高能球磨后,颗粒尺寸下降,Ti、Al晶粒各自逐渐细化至纳米级尺寸,且部分形成非晶,球磨15h后发现了TiAl和Ti3Al金属间化合物。将机械合金化后的粉末进行放电等离子烧结,烧结试样的组成相主要为TiAl和Ti3Al。     

Stratification of fuel for better engine performance

The concept of fuel stratification has been proposed and applied to a four-valve port injection spark ignition engine. In this engine, two different fuels or fuel components are admitted through two separate inlet ports and stratified into two regions laterally by strong tumble flows. Each stratified region has a spark plug to control the ignition. This engine can operate in the stratified lean-burn mode at part loads when fuel is supplied only to one of the inlet ports. While at high load operation, an improved fuel economy and higher power output are also expected through increased anti-knock features by taking advantage of the superior characteristics of different fuel or fuel components. This is achieved by igniting the lower RON (research octane number) fuel first and leaving the higher RON fuel in the end gas region. In this paper, knock limits of homogenous and different fuel stratification combustion modes at high loads were investigated experimentally. Primary reference fuels (PRF), iso-octane and n-heptane, were used to simulate three fuels of different RON: RON90, RON95 and RON100. The research results show that with stratified fuel components of low and high octane numbers, the knock limit, as defined by the minimum spark advance for knocking combustion, was extended apparently when the lower RON fuel was ignited first. In addition, the knock limit could also be extended by increasing the amount of higher RON fuel. However, igniting first the lower RON fuel in the fuel stratification combustion mode produced little improvement in anti-knock behaviour over the homogeneous combustion of the mixture of those two stratified fuels with an average RON.     

Ultra-high-temperature tantalum-hafnium carbonitride ceramics fabricated by combustion synthesis and spark plasma sintering

We report the fabrication of dense single-phase (Ta,Hf)CN carbonitride ceramics using a combination of combustion synthesis (CS) and spark plasma sintering (SPS). The ceramic powder was produced by high-energy ball milling of the reactants (Ta, Hf, C) in different atomic ratios followed by CS of the obtained nanostructured composites in a nitrogen atmosphere. X-ray diffraction analysis of the combustion products revealed the formation of (Ta,Hf)CN with cubic B1 structures as the dominant phases for all investigated compositions. The SPS of the as-synthesized powders allowed both homogenization of the composition and consolidation of the bulk single-phase carbonitride ceramics with a relative density of 98 ± 1 %. Ta₂₅Hf₇₅CN showed the highest hardness (19.4 ± 0.2 GPa) and fracture toughness (5.4 ± 0.4 MPa m^1/2) among the investigated composites and excellent oxidation resistance in air.