加氢站风险评价研究现状与进展

伴随着世界各国氢燃料电池车示范项目的实施,与之配套的氢能基础设施--加氢站也在全球范围内迅速发展.作为一种新兴的能源基础设施,能否为公众提供足够的安全,一直是政府和公众非常关心的问题.而目前国际上关于加氢站风险评价方面存在的主要争议,即是损害限和风险接受标准确定的问题.本文通过回顾国外加氢站风险评价的研究现状和进展,从危险辨识、概率分析、后果评价以及风险度量等方面总结了加氢站风险评价的方法,对氢能设施风险评价开展的基础--氢气行为及其后果等氢能安全进行了分析,在此基础上,进一步综述了近几年国际上在该领域研究取得的进展.     

容错粗糙主成分分析的属性约简方法

在分析大肠早癌荧光数据属性约简方法的基础上,提出一种基于容错关系信息熵的粗糙主成分属性约简方法.该方法首先针对数据的不完整特性,建立容错关系粗糙集模型.然后,引入随信息量减小而单调下降的信息熵,建立基于信息熵的容错关系粗糙集模型,并进行初步数据属性处理.最后,结合主成分分析方法,形成基于容错关系信息熵的粗糙主成分分析方法,在进行数据降维处理的同时提取数据特征.以大肠早癌荧光光谱为实验数据的分析处理结果表明,该方法可以有效地降低荧光光谱数据的处理维数,提取影响医疗诊断的特征数据,减少后续数据处理的复杂度.     

基于邻域空间模式的运动相关电位特征提取方法

为解决脑-机接口(BCI)研究中所采集的脑电图(EEG)信号数据分布复杂和训练样本不足的问题,文中提出了一种新的特征提取方法--邻域空间模式(NSP)算法,用于提取BCI想象肢体运动分类算法中使用的重要分类特征--运动相关电位(MRPs).NSP算法不需要对样本的数据分布进行假设,主要利用样本的邻域关系和类别信息寻找最佳投影方向,使得映射后邻域内异类样本距离之和与同类样本距离之和的比值最大化.采用BCI竞赛2003和2001的其中两组数据进行实验,结果表明NSP算法能更有效地提取MRPs特征.     

有机醇介质中盐酸对马铃薯淀粉性质的影响

以无水甲醇、无水乙醇、异丙醇及正丁醇作溶剂,用盐酸对马铃薯淀粉进行改性.研究了马铃薯淀粉在有机醇溶液中酸改性前后的物化性质.结果表明:经酸处理的马铃薯淀粉随有机醇介质(从甲醇到正丁醇)碳原子数量的增加,颗粒表面逐步出现裂纹直到产生碎片,冻融稳定性依次减弱,透明度依次增强,黏度依次减小,溶解度逐渐增加,膨胀度逐渐降低.以上结果表明酸在不同有机醇介质中对淀粉的作用程度从甲醇到丁醇依次增强.     

具有两类修复设备可修系统解的最优控制问题

用Banach空间理论,以泛数指标函数作为衡量系统可控的标准,讨论了可修复系统最优控制问题．     

Superconductivity in Ba1−xSmxFFeAs and Eu1−xSmxFFeAs systems

We synthesized the samples Ba1-xSmxFFeAs and Eu1-xSmxFFeAs with ZrCuSiAs-type structure. These samples were characterized by resistivity and susceptibility. It is found that the substitution of rare earth metal for alkaline earth metal in the two systems suppresses the anomaly in resistivity and induces superconductivity. Superconductivity at 54 K in nominal composition Ba0.5Sm0.5FFeAs and at 51 K for Eu0.5Sm0.5FFeAs is realized, indicating that the superconducting transition temperatures in the iron arsenide fluorides is the same as that in oxypnictides with the same structure.     

Methane emissions from terrestrial plants over China and their effects on methane concentrations in lower troposphere

Methane (CH₄) is the most important greenhouse gas and reactive trace gas in the atmosphere. Recently, it has been reported that terrestrial plants can emit CH₄ under aerobic conditions, which may call for reevaluation of the inventory of CH₄ emissions in China. In this paper, those emissions over China and their effects on CH₄ concentrations in lower troposphere were investigated. Firstly, based on the work of Keppler et al., the aerobic plant CH₄ emission model (PLANTCH4) for China was established. And by using the database of normalized difference vegetation index (NDVI) derived from NOAA/AVHRR, the distribution of net primary productivity (NPP) over China was simulated, and thereby, for the first time, the amount and distribution of the newly identified source in China were estimated. Secondly, with the aid of the three-dimensional atmospheric chemistry model system (MM5-CALGRID), the effects of the emissions were studied. The results show that the annual aerobic plant CH4 emissions over China amount to 11.83 Tg, i.e. nearly 24% of Chinese total CH₄ emissions. And the major fraction (about 43%) comes from forests. When those emissions are considered in modeling, computed countrywide mean surface concentration of CH₄ is 29.9% higher than without them, with a maximum increase of 69.61 μg·m⁻³ in the south of Yunnan Province. In conclusion, to study CH₄ emissions from terrestrial plants over China may have important implications for correctly estimating the contribution of China to global CH₄ budget, and may call for a reconsideration of the role of CH₄ in global and regional environment and climate change. Supported by National High-Tech Research & Development Program of China (Grant No. 2006AA06A307), National Basic Research Program of China (Grant Nos. 2006CB403706 and 2006CB403703), and the Program for New Century Excellent Talents in University, and Nanjing University Talent Development Foundation     

Harmonic hexagonal superlattice pattern in a dielectric barrier discharge at atmospheric pressure

We report a harmonic hexagonal superlattice pattern in a dielectric barrier discharge in air/argon mixture at atmospheric pressure. The bifurcation scenario of harmonic hexagonal superlattice pattern with the applied voltage increasing is given. The phase diagram of the pattern types as a function of the applied voltage and the air-concentration is obtained. The hysteresis of pattern transitions at the upward and downward stage of the applied voltage is observed. The correlation measurements indicate that harmonic hexagonal superlattice pattern is an interleaving of two different transient sublattices. The spatial power spectrum demonstrates that harmonic hexagonal superlattice pattern has two separate wave vectors. Both small wave vector qh and big wave vector Kh, belong to the harmonic mode, and they obey a triad resonant interaction qh^1 ＋ qh^2 = Kh.     

灌注桩后注浆技术分析

注浆是岩土工程中一门专业性很强的学术分支,用注浆处理各种岩土工程问题,已成为常用的方法。桩基后注浆技术能够提高桩承载力,减少桩沉降量以及提高桩顶回弹量,文章针对汾河地区进行桩基在注浆与未注浆的条件下,对比静载试验和桩侧摩阻力测试结果,并总结出桩基后注浆技术相关结论与经验。     

第三代蜜网在园区网中的应用

蜜网（Honeynet）是信息安全领域相对较新的一个概念,主要作用是收集黑客的攻击信息。随着蜜网技术的引入,可以将安全防护从被动方式变为主动方式。阐述了第三代蜜网体系结构,分析了数据控制、数据捕获、数据采集和数据分析模块在蜜网中的实现,并介绍了蜜网在校园网中的应用。