998 resultados para Galton-Watson processes


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Research related to carbon geochemistry and biogeochemistry in the East China Sea is reviewed in this paper. The East China Sea is an annual net sink for atmospheric CO, and a large net source of dissolved inorganic carbon to the ocean. The sea absorbs CO, from the atmosphere in spring and summer and releases it in autumn and winter. The East China Sea is a CO, sink in summer because Changjiang River freshwater flows into it. The net average sea-air interface carbon flux of the East China Sea is estimated to be about 4.3 X 10(6) t/y. Vertical carbon transport is mainly in the form of particulate organic carbon in spring; more than 98% of total carbon is transported in this form in surface water, and the number exceeds 68% in water near the bottom. In the southern East China Sea, the average particulate organic carbon inventory was about one-tenth that of the dissolved organic carbon. Research indicates that the southern Okinawa Trough is an important site for particulate organic carbon export from the shelf. The annual cross-shelf exports are estimated to be 414 and 106 Gmol/y for dissolved organic carbon and particulate organic carbon, respectively. Near-bottom transport could be the key process for shelf-to-deep sea export of biogenic and lithogenic particles.

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The water-heat transfer process between land and atmosphere in Haibei alpine meadow area has been systematically observed. A multi-layer coupling model for land-atmosphere interaction was presented with special attention paid to the moisture transfer in leaf stomata under unsaturated condition. A profound investigation on the physical process of turbulent transfer inside the vegetation has been performed with a revised formula of water absorption for root system. The present model facilitates the study of vertically distributed physical variables in detail. Numerical simulation was conducted according to the transfer process of Kinesia humility meadow in the area of Haibei Alpine Meadow Ecosystem Station, CAS. The calculated results agree well with observation.

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由于缺乏相应的沉积地层,贵州新生代地质、环境演化恢复一直是学术界的难点问题。夷平面研究的兴起,为陆地地壳抬升、地貌演变等反演提供了理论基础,而风化壳正是夷平面研究的重要替代对象,尤其是对各类沉积地层不发育的地区。因而,贵州高原各级台地上发育有较为广泛的红色风化壳自然地、就成了主要研究载体。然而一与其它岩类不同,碳酸盐岩风化成土作用过程研究并没有得到同等重视,其研究范围和程度均很不充分。显然,要想利用碳酸盐岩风化壳进行夷平面等地质、地貌意义研究,就必需详细了解贵州或中国南方碳酸盐岩风化成土的基本过程。也只有如此,才能明确各种对比指标的使用条件和范围,才能明确各种测年结果的具体意义,才能真正地通过贵州碳酸盐岩风化壳获取全省地质、环境演化信息。本论文通过对贵州省岩溶台地碳酸盐岩石灰土、红色风化壳剖面形成地球化学过程的剖析,开展石灰土与红色风化壳之间的关联和差异性综合对比、红色风化壳之间发育程度的比较,以及风化壳剖面尝试性的侧年等方面研究,取得了以下儿点认识:1、石灰土形成地球化学过程及对比通过矿物组成、粒度分布特征、地球化学方法判别,确定了本文所选石灰土剖面物质来源于下伏碳酸盐岩中的酸不溶物,是碳酸盐岩风化后酸不溶物原地残余堆积的结果。石灰土形成的地球化学过程都遵循碳酸盐岩风化成土之两阶段模式:母岩-酸不溶物,大量可溶性物质Ca、Mg、Mn、P、Na淋失,而Si、K·Fe、Al、Ti则相对富集。该过程的矿物组成变化表现为,伴随碳酸盐矿物(方解石、白云石等)的溶解、迁移,硅酸盐相矿物(长石、2:1型粘土矿物等)残余、累积。酸不溶物,土层或土层的演化,K、Si(长石、伊利石)不断淋失,而Al(伊利石、高岭石、三水铝石)、Fe(针铁矿、赤铁矿等)逐渐富集,体现出脱硅、富铝(铁)过程。我们强调碳酸盐岩风化成土分为两个阶段,但也认识到风化作用是综合的、复杂的:在碳酸盐矿物大量淋失过程中,同时也进行着酸不溶物的风化。石灰土分为原生和次生两种成因类型。原生石灰土的风化程度总体较低,剖面中还残留一定量的CaCO3,剖面从下到上矿物组成、地球化学各种指标具有逐渐演化的过渡特征。原生石灰上土层演化过程显示出正风化序列,从下到上风化程度逐渐增大、可溶性物质逐渐减少、稳定和相对稳定组分(Al、Fe.、REE)含量不断增大。另外,主量元素的质量迁移系数在剖面中的变化与风化程度呈明显的相关性。而次生石灰土不但具有很高的风化程度,而且剖面无过渡特征,显示可能是由遭受强烈风化作用的物质直接转变形成的。剖面中也含有一定量后期加入的碳酸盐,但与高CIA值特征不相匹配;SiO2、Al2O3、Fe2O3组分具有不同的变化特征,与)成化程度无明显关联;REE在剖面岩一上界面出现富集层。2、碳酸盐岩红色风化壳形成地球化学过程及其与石灰土的对比红色风化壳形成的地球化学过程也遵循碳酸盐岩风化成土之两阶段模式:母岩一酸不溶物,大量可溶性物质Ca、Mg、Mn、P、Na淋失,而Si、K、Fe、Al、Ti则相对富集。该过程的矿物组成变化表现为,伴随碳酸盐矿物(方解石、白云石等)的溶解、迁移,硅酸盆相矿物(长石、2:1型粘土矿物等)残余、累积。酸不济物一土层或上层的演化,K、Si(长石、伊利石)不断淋失,而Al(伊利石、高岭石、三水铝石)、Fe(针铁矿、赤铁矿等)逐渐富集,体现出脱硅、富铝(铁)过程。石灰土与红色风化壳之间既存在共性,又有一定的差异性。红色风化壳与原生石灰土一样都具有过渡特征,但后者仅在剖面下部出现一定的过渡层位;原生石灰士的城化程度远低于红色风化壳,仅与后者底部土层相当;原生石灰土不具有红色风化壳之岩-土REE(超常)富集层。总体上,原生石灰土可以作为红色风化壳的前身。次生石灰土与红色风化壳在矿物组成、风化程度等各种地球化学指标等都十分接近(略低),显示与红色风化壳之间存在某种关联:由红色风化壳物质直接转变,或由酸不溶物已强烈风化的(白云岩)岩粉、碎裂岩风化形成。3、碳酸盐岩风化成土母岩差异性碳酸盐岩风化成土存在母岩差异性,石灰土母岩差异性较为明显,而红色风化壳的母岩差异性较弱,体现出红色风化壳的均一化特征。石灰土母岩差异性体现为:母岩为灰岩的石灰土剖面主量元素含量变化特征较为一致,而白云岩则具有不同的变化;灰岩石灰土Fe3+、Al具有不同的富集、亏损特征,且具有富集层的补偿亏损层,而白云岩石灰上两组分都呈现无补偿层位的相同富集态势;灰岩石灰土剖面出现负Eu异常和具以Gd为中心的倒“V”型MREE稀土富集特征(母岩标准化),而白云岩石灰土无明显Eu异常和具L既E或HREE稀士.富集特征;灰岩和白云岩石灰土的微量元素富集、亏损特征也有所不同,前者从上到下逐渐富集,而后者无明显变化趋势。红色风化壳形成的基本过程、主量元素地球化学行为无明显的母岩相关性,没有如石灰土剖面灰岩和白云岩之间存在的差异性,显示出红土化作用的均一化过程;微量元素中受重矿物影响的元素与母岩类型有一定的关联,但大多数元素的亏损、富集等与具体剖面的微环境关系密切。4、碳酸盐岩红色风化壳发育程度的对比及意义多利指标对比显示所选红色风化壳的风化程度有一定的强弱差别:平坝剖面>湖潮剖面>天龙剖面、大兴剖面>花溪剖面、新蒲剖面,但这种差异性不足以否定各剖面隶属于贵州山盆期广泛夷平面的基本推测。各剖面之间的微弱差异是红色风化壳形成时纬度分带和垂向分带的体现。低纬度的平坝、湖潮、天龙剖面经历的风化作用强于高纬度的新蒲、大兴剖面;高海拔的新蒲剖面风化程度低于海拔低的大兴剖面。5、红色风化壳次生石英裂变径迹测年红色风化壳次生石英裂变径迹方法测年尝试,得到一定的结果和认识:晶形相对较好的石英,是次生的,与母岩中碎屑及成岩阶段没有关联;各剖面上部与中、下部次生石英的诱发裂变径迹的密度有着明显的区别,可能暗示它们的形成环境不同;名一剖面石英的形成或退火年龄分布较为分散,1.2-25.2Ma,同一剖面的石英年龄也不均一,变化较大;从下到上,年龄值呈现出逐渐减小的规律性,与风化作用的正常序列相反。如果能确切其成因,次生石英裂变径迹年代学研究将是确定风化壳形成时代及揭示主要风化作用信,却钩有利武器。

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The micro-pore configurations on the matrix surface were studied by SEM. The matrix of molten carbonate fuel cell (MCFC) performance was also improved by the better coordination between the reasonable radius of the micro-pores and the higher porosity of the cell matrix. The many and complicated micro-pore configurations in the cell matrix promoted the volatilization of the organic additives and the burn of polyvinyl butyral (PVB). The smooth volatilization of the organic additives and the complete burn of PVB were the significant factors for the improved MCFC performance. Oxygen diffusion controlled-burn mechanism of PVB in the cell matrix was proposed. (C) 2002 Published by Elsevier Science Ltd.

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The Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences has a long history in the R&D of catalysts and catalytic processes for petroleum and natural gas conversions in China. In this paper, results and features of some commercialized petrochemical catalysts and processes as well as newly developed processes for natural gas conversion in the pilot-plant stage are described. (C) 1999 Elsevier Science B.V. All rights reserved.

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In this report, I discuss the use of vision to support concrete, everyday activity. I will argue that a variety of interesting tasks can be solved using simple and inexpensive vision systems. I will provide a number of working examples in the form of a state-of-the-art mobile robot, Polly, which uses vision to give primitive tours of the seventh floor of the MIT AI Laboratory. By current standards, the robot has a broad behavioral repertoire and is both simple and inexpensive (the complete robot was built for less than $20,000 using commercial board-level components). The approach I will use will be to treat the structure of the agent's activity---its task and environment---as positive resources for the vision system designer. By performing a careful analysis of task and environment, the designer can determine a broad space of mechanisms which can perform the desired activity. My principal thesis is that for a broad range of activities, the space of applicable mechanisms will be broad enough to include a number mechanisms which are simple and economical. The simplest mechanisms that solve a given problem will typically be quite specialized to that problem. One thus worries that building simple vision systems will be require a great deal of {it ad-hoc} engineering that cannot be transferred to other problems. My second thesis is that specialized systems can be analyzed and understood in a principled manner, one that allows general lessons to be extracted from specialized systems. I will present a general approach to analyzing specialization through the use of transformations that provably improve performance. By demonstrating a sequence of transformations that derive a specialized system from a more general one, we can summarize the specialization of the former in a compact form that makes explicit the additional assumptions that it makes about its environment. The summary can be used to predict the performance of the system in novel environments. Individual transformations can be recycled in the design of future systems.

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The world is facing environmental changes that are increasingly affecting how we think about manufacturing, the consumption of products and use of resources. Within the HE product design community, thinking and designing sustainability’ has evolved to become a natural part of the curriculum. Paradoxical as the rise in awareness of sustainability increases there is growing concern within HE product design of the loss of workshop facilities and as a consequence a demise in teaching traditional object-making skills and material experimentation. We suggest the loss of workshops and tangible ‘learning by making skills’ also creates a lost opportunity for a rich learning resource to address sustainable thinking, design and manufacture ‘praxis’ within HE design education. Furthermore, as learning spaces are frequently discussed in design research, there seems to be little focus on how the use of an outdoor environment might influence learning outcomes particularly with regard to material teaching and sustainability. This 'case study' of two jewellery workshops, used outdoor learning spaces to explore both its impact on learning outcomes and to introduce some key principles of sustainable working methodologies and practices. Academics and students mainly from Norway and Scotland collaborated on this international research project. Participants made models from disposable packaging materials, which were cast in tin, in the sand on a local beach, using found timber to create a heat source for melting the metal. This approach of using traditional making skills, materials and nature was found to be a relevant contribution to a sustainable discourse.

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Shen, Q., Zhao, R., Tang, W. (2008). Modelling random fuzzy renewal reward processes. IEEE Transactions on Fuzzy Systems, 16 (5),1379-1385

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Poolton, Nigel; Ozanyan, K.B.; Wallinga, J.; Murray, A.S., (2002) 'Electrons in feldspar II: a consideration of the influence of conduction band-tail states on luminescence processes', Physics and Chemistry of Minerals 29(3) pp.217-225 RAE2008