活性炭纤维富集煤低温氧化气体中C2-C3烃的可行性

指标气体预报煤炭自燃在煤矿安全生产中得到广泛的应用,但由于煤低温氧化释放的某些烃类指标气体浓度很低,色谱直接进样有时无法到出。用活性炭纤维作为吸附剂富集煤低温氧化放出的C2-C3烃,用气相色谱定量分析了脱附气中的C2-C3烃。为了保证富集的效果和数据的准确性,对吸附剂的吸附破过体积、最佳脱附温度、脱附气进样的线性规律和实验的重复性进行了考察。提出了用校正函数方法校正吸附-脱附过程中的误差。并用所建立的方法到定了煤温从50℃上升到200℃过程中乙烯与乙烷、丙烷与乙烷浓度比值随煤温的变化关系。     

产品评论挖掘可视化实验平台的开发

针对目前研究人员已经提出多种中文评论挖掘方法,缺乏统一的评论实验数据集的现状,首先从知名网站上随机抽取手机评论,经过垃圾去除、手工标注,最终构造出手机领域的评论挖掘实验数据集.基于实验数据集构造出手机领域的情感词库,并利用模式匹配方法建立了产品特征粒度树,开发出一个可视化平台,研究人员可以直接用其检验挖掘方法的效果,也可以对不同的挖掘方法进行客观比较.     

Increased soil emissions of potent greenhouse gases under increased atmospheric CO2

Increasing concentrations of atmospheric carbon dioxide (CO(2)) can affect biotic and abiotic conditions in soil, such as microbial activity and water content. In turn, these changes might be expected to alter the production and consumption of the important greenhouse gases nitrous oxide (N(2)O) and methane (CH(4)) (refs 2, 3). However, studies on fluxes of N(2)O and CH(4) from soil under increased atmospheric CO(2) have not been quantitatively synthesized. Here we show, using meta-analysis, that increased CO(2) (ranging from 463 to 780 parts per million by volume) stimulates both N(2)O emissions from upland soils and CH(4) emissions from rice paddies and natural wetlands. Because enhanced greenhouse-gas emissions add to the radiative forcing of terrestrial ecosystems, these emissions are expected to negate at least 16.6 per cent of the climate change mitigation potential previously predicted from an increase in the terrestrial carbon sink under increased atmospheric CO(2) concentrations. Our results therefore suggest that the capacity of land ecosystems to slow climate warming has been overestimated.     

Uncertainty in predictions of the climate response to rising levels of greenhouse gases

The range of possibilities for future climate evolution needs to be taken into account when planning climate change mitigation and adaptation strategies. This requires ensembles of multi-decadal simulations to assess both chaotic climate variability and model response uncertainty. Statistical estimates of model response uncertainty, based on observations of recent climate change, admit climate sensitivities--defined as the equilibrium response of global mean temperature to doubling levels of atmospheric carbon dioxide--substantially greater than 5 K. But such strong responses are not used in ranges for future climate change because they have not been seen in general circulation models. Here we present results from the 'climateprediction.net' experiment, the first multi-thousand-member grand ensemble of simulations using a general circulation model and thereby explicitly resolving regional details. We find model versions as realistic as other state-of-the-art climate models but with climate sensitivities ranging from less than 2 K to more than 11 K. Models with such extreme sensitivities are critical for the study of the full range of possible responses of the climate system to rising greenhouse gas levels, and for assessing the risks associated with specific targets for stabilizing these levels.     

A nebula of gases from Io surrounding Jupiter

Several planetary missions have reported the presence of substantial numbers of energetic ions and electrons surrounding Jupiter; relativistic electrons are observable up to several astronomical units (au) from the planet. A population of energetic (>30[?]keV) neutral particles also has been reported, but the instrumentation was not able to determine the mass or charge state of the particles, which were subsequently labelled energetic neutral atoms. Although images showing the presence of the trace element sodium were obtained, the source and identity of the neutral atoms---and their overall significance relative to the loss of charged particles from Jupiter's magnetosphere---were unknown. Here we report the discovery by the Cassini spacecraft of a fast (>103[?]km[?]s-1) and hot magnetospheric neutral wind extending more than 0.5[?]au from Jupiter, and the presence of energetic neutral atoms (both hot and cold) that have been accelerated by the electric field in the solar wind. We suggest that these atoms originate in volcanic gases from Io, undergo significant evolution through various electromagnetic interactions, escape Jupiter's magnetosphere and then populate the environment around the planet. Thus a 'nebula' is created that extends outwards over hundreds of jovian radii.     

温室气体减排与CO2资源化宏观研究与探讨

介绍了近一段时间全球温室气体减排的进展及面临的形势,并预测了未来二氧化碳的排放趋势.着重对CO2的资源化问题进行了分析和探讨,从CO2作为再生资源的角度讨论了CO2的回收、利用和处置技术;同时指出资源化问题存在的挑战和负面影响.证明CO2资源化对温室气体减排作用不明显,应大力提倡"无悔"行动.最后从热力学角度分析了CO2问题的本质.     

基于神经网络的数据挖掘方法评述

简要叙述了数据挖掘的概念及几种主要的基于神经网络的数据挖掘方法,并对这些方法的研究现状进行了评述,指出其存在的问题.展望神经网络在数据挖掘中的发展潜力.     

Greenhouse gases: low methane leakage from gas pipelines

Using natural gas for fuel releases less carbon dioxide per unit of energy produced than burning oil or coal, but its production and transport are accompanied by emissions of methane, which is a much more potent greenhouse gas than carbon dioxide in the short term. This calls into question whether climate forcing could be reduced by switching from coal and oil to natural gas. We have made measurements in Russia along the world's largest gas-transport system and find that methane leakage is in the region of 1.4%, which is considerably less than expected and comparable to that from systems in the United States. Our calculations indicate that using natural gas in preference to other fossil fuels could be useful in the short term for mitigating climate change.     

New proofs of the recent climate warming over the Tibetan Plateau as a result of the increasing greenhouse gases emissions

The Tibetan Plateau (TP, 75-105oE, 27.5-37.5oN) is the highest and largest highland in the world with a variety of climate and ecosystems. The TP exerts pro- found influences not only on the local climate and en- vironment but also on the global atmospher…     

野罂粟生物碱化学成分及生物活性研究进展

1987年卫生部“关于野罂粟、阿朴吗啡和烯炳吗啡不再列入麻醉药品管理范围的通知”,为野罂粟的研究工作带来新的契机.本文利用CNKI、清华同方、万方和ISI数据库,得到1970以来有关野罂粟(Papaver nudicaule L.)的中外文文献共140篇.通过对文献的系统整理与分析,已确定野罂粟生物碱的34个生物碱单体及其药理作用.这些将为野罂粟的药化与药理研究及其种质资源的开发与持续利用提供科学依据.     

一种不确定性数据中最大频繁项集挖掘方法

不确定性数据挖掘已经成为数据挖掘领域的新热点,频繁项集挖掘是重点研究的问题之一.但是目前出现的挖掘算法大多集中在完全频繁项集,而用于最大频繁项集和频繁闭项集的算法尚不多见.文中研究了一种基于UF-Tree的用于不确定性数据中挖掘最大频繁项集的算法,该挖掘过程分为两个步骤,第一步先得到以频繁1-项集为后缀的局部最大频繁项集,第二步得到所有的全局最大频繁项集,实验证明该算法性能良好且特别适用于稠密型、事务长度较小的数据集.     

A Novel Incremental Mining Algorithm of Frequent Patterns for Web Usage Mining

Because data warehouse is frequently changing, incremental data leads to old knowledge which is mined formerly unavailable. In order to maintain the discovered knowledge and patterns dynamically, this study presents a novel algorithm updating for global frequent patterns-IPARUC. A rapid clustering method is introduced to divide database into n parts in IPARUC firstly, where the data are similar in the same part. Then, the nodes in the tree are adjusted dynamically in inserting process by ＂pruning and laying back＂ to keep the frequency descending order so that they can be shared to approaching optimization. Finally local frequent itemsets mined from each local dataset are merged into global frequent itemsets. The results of experimental study are very encouraging. It is obvious from experiment that IPARUC is more effective and efficient than other two contrastive methods. Furthermore, there is significant application potential to a prototype of Web log Analyzer in web usage mining that can help us to discover useful knowledge effectively, even help managers making decision.     

产品评论挖掘研究综述

描述了产品评论挖掘的基本概念,介绍了产品评论挖掘工作的一般框架,将产品评论挖掘划分为4个子任务,介绍了国内外学者对每个子任务的研究成果,并给出了该领域进一步的研究方向。     

生物质热解释氢的实验研究

以密封的管式炉为反应器,以稻壳粉为原料,通过自动控制系统控制热解反应参数,对生物质热解的3种产物(气体、焦油和木炭)单独收集并进行了分析.结果表明,产气中氢气的百分含量随着热解温度的提高明显增加,热解反应在未完成之前,增加反应时间有利于提高氢的百分含量.发现在水蒸气和生物质比率(S/B)小于0.37时,氢的百分含量随S/B的增大而增加,S/B大于0.37后,氢气的百分含量有缓慢变小的趋势.     

一种从Web日志中挖掘访问模式的新算法

提出了一种用于从Web日志中高效挖掘Web访问模式的新算法．设计了一个新的数据结构WAS树(Web Access Sequence树)来记录Web访问序列和它的计数，避免冗长的支持度计算；开发出一个高效的递归算法，从WAS树中枚举出所有的访问模式，最后对算法的性能进行了分析并给出试验数据加以佐证．这个算法的特点是不需要产生候选模式而直接挖掘出所有的访问模式。     

一种高效关联规则挖掘算法

为了提高关联规则挖掘算法处理数据库的效率,在研究AprioriTid算法的基础上提出一种高效的关联规则挖掘算法AprioriTidD,在计算数据库中的频繁项集时依靠有效的裁剪减少无效项集的产生,并且可减少产生候选项集,从而有效地提高算法的效率.选取程序模拟超市购物产生的3个试验数据集,应用AprioriTidD算法对该...     

K—酪蛋白研究进展

对k-酪蛋白(kappa-casein,k-CN）的基本特征,遗传多态性及其与乳成分、凝乳性能的关系,以及k-CN定型技术作了综述,并探讨了k-CN遗传多态性在乳酪生产和牦牛育种中的应用前景。     

WA-IDS： A Distributed Intrusion Detection System Based on Data Mining

Aiming at the shortcomings in intrusion detection systems (IDSs) used in commercial and research fields, we propose the MAIDS system, a distributed intrusion detection system based on data mining. In this model, misuse intrusion detection system (MIDS) and anomaly intrusion detcction system (AIDS) are combined. Data mining is applicd to raise detection performance, and distributed mechanism is employed to increase the scalability and efficiency. Host- and network based mining algorithms employ an improved Bayesian decision theorem that suits for real security environment to minimize the risks incurred by false decisions. We describe the overall architeeture of thc MA-IDS system, and discusss pecific design and implementation issue.