993 resultados para Carnot, Lazare, 1753-1823.


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Analyses of rare earth and trace element concentrations of native sulfur samples from the Kueishantao hydrothermal field were performed at the Seafloor Hydrothermal Activity Laboratory of the Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences. Using an Elan DRC II ICP-MS, and combining the sulfur isotopic compositions of native sulfur samples, we studied the sources and formation of a native sulfur chimney. The results show, when comparing them with native sulfur from crater lakes and other volcanic areas, that the native sulfur content of this chimney is very high (99.96%), the rare earth element (REE) and trace element constituents of the chimney are very low (Sigma REE < 21x10(-9)), and the chondrite-normalized REE patterns of the native sulfur samples are similar to those of the Kueishantao andesite, implying that the interaction of subseafloor fluid-andesite at the Kueishantao hydrothermal field was of short duration. The sulfur isotopic compositions of the native sulfur samples reveal that the sulfur of the chimney, from H2S and SO2, originated by magmatic degassing and that the REEs and trace elements are mostly from the Kueishantao andesite and partly from seawater. Combining these results with an analysis of the thermodynamics, it is clear that from the relatively low temperature (< 116 degrees C), the oxygenated and acidic environment is favorable for formation of this native sulfur chimney in the Kueishantao hydrothermal field.

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企业管理信息系统 (EMIS) 是 CIMS 的重要组成部分.随着企业环境的演变,不仅应研究各种批量生产方式的管理方法,更应注意一样一件 (OKP) 生产方式.企业对 CIMS 环境中 EMIS 的需求不断增长,它比普通的 EMIS 更复杂.本文首先对 MRPⅡ的应用开发进行分析,认为应吸取 MRPⅡ的核心部分开发适合国情的 EMIS 产品;然后提出了 EMIS 的通用概念结构及子系统的划分.这一通用概念结构已用于沈阳鼓风机厂的 CIMS 初步设计中.

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尽管西南岩溶地区石漠化趋势严重,但真正做到生态、经济、社会三效益统一的岩溶石漠化生态重建模式的实践工作却做得很少。且对于这些实践活动还缺乏理论的总结和思考。花江峡谷顶坛片区,充分利用当地的适生植物资源和干热资源优势在石漠化土地上种植花椒、砂仁等喜热耐旱的经济作物,在恢复和治理生态的前提下成功调整了农业内部结构,形成以花椒规模种植为核心心的特色产业,利用雨水、坡面水、岩溶裂隙水,实行参与式社区管理,使环境、经济与社区文化得以可持续发展。“顶坛”模式是充分利用岩溶环境资源优势,高山地保护于特色农业开发之中的一个成功例子。它启示我们,岩溶石漠化土地恢复重建必须重新认识岩溶环境优势。因地制宜,对过去侧重于水土保持的传统治理模式进行创新。

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对安徽省冬瓜山层控夕卡岩型铜(金)矿床中穿层方向上不同蚀变程度的大理岩,顺层方向上距岩体远近不同但垂向深度的块状石榴子石夕卡岩及其主矿物石榴子石,不同演化阶段的石英及矿石等到的REE特征进行了系统研究,结果显示,在穿层方向上,大理岩被交代的程度愈深其稀土总量(∑REE)愈高,Eu负异常愈显著,尽管,夕卡岩全岩的RE分布模式与原岩(大理岩)相似,但前者的稀土总量(∑REE)远高于后者,且Eu异常更为显著,显然不是继续承原岩的REE特征所致,而是受控于其主矿物石榴子石的REE特征,后者又由参与交代作用的岩浆热液REE所决定,热液中的REE具有缓和右倾型分布模式,LREE富集,较显著的Eu负异常等基本特征,石榴子石晶体基本承袭了热液的REE特征,REE的空间变化特征结果地层的构造特征可以揭示夕卡岩及相关矿体形成过程中流体的输运径及输运方式,REE的研究有助于深化对层控夕卡岩及其相关矿床形成过程的认识。

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Marnet, Oliver, 'Behaviour and rationality in corporate governance', Journal of Economic Issues (2005) 39(3) pp.613-632 RAE2008

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Relatório apresentado à Universidade Fernando Pessoa como parte dos requisitos para cumprimento do programa de pós-doutoramento em Ciências da Comunicação, vertente Jornalismo

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NetSketch is a tool for the specification of constrained-flow applications and the certification of desirable safety properties imposed thereon. NetSketch is conceived to assist system integrators in two types of activities: modeling and design. As a modeling tool, it enables the abstraction of an existing system while retaining sufficient information about it to carry out future analysis of safety properties. As a design tool, NetSketch enables the exploration of alternative safe designs as well as the identification of minimal requirements for outsourced subsystems. NetSketch embodies a lightweight formal verification philosophy, whereby the power (but not the heavy machinery) of a rigorous formalism is made accessible to users via a friendly interface. NetSketch does so by exposing tradeoffs between exactness of analysis and scalability, and by combining traditional whole-system analysis with a more flexible compositional analysis. The compositional analysis is based on a strongly-typed Domain-Specific Language (DSL) for describing and reasoning about constrained-flow networks at various levels of sketchiness along with invariants that need to be enforced thereupon. In this paper, we define the formal system underlying the operation of NetSketch, in particular the DSL behind NetSketch's user-interface when used in "sketch mode", and prove its soundness relative to appropriately-defined notions of validity. In a companion paper [6], we overview NetSketch, highlight its salient features, and illustrate how it could be used in two applications: the management/shaping of traffic flows in a vehicular network (as a proxy for CPS applications) and in a streaming media network (as a proxy for Internet applications).

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The increasing practicality of large-scale flow capture makes it possible to conceive of traffic analysis methods that detect and identify a large and diverse set of anomalies. However the challenge of effectively analyzing this massive data source for anomaly diagnosis is as yet unmet. We argue that the distributions of packet features (IP addresses and ports) observed in flow traces reveals both the presence and the structure of a wide range of anomalies. Using entropy as a summarization tool, we show that the analysis of feature distributions leads to significant advances on two fronts: (1) it enables highly sensitive detection of a wide range of anomalies, augmenting detections by volume-based methods, and (2) it enables automatic classification of anomalies via unsupervised learning. We show that using feature distributions, anomalies naturally fall into distinct and meaningful clusters. These clusters can be used to automatically classify anomalies and to uncover new anomaly types. We validate our claims on data from two backbone networks (Abilene and Geant) and conclude that feature distributions show promise as a key element of a fairly general network anomaly diagnosis framework.