994 resultados para Poisson processes
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Abstract The karsrt erosion engineering geology became a highlight problem in recent years, in particularly, the karst erosion of marlite of Badong formation made the rock mechanics weaken in Three Gorges Reservoir area, which reduces the safety of slope. During the immigrant construction, many high slopes have been formed, whose instabilities problems pose serious threats to the safety of the people and properties. The accidents of the slope failure take place now and then. By testing, it has been found that the karst erosion pattern and dissolution rate of marlite are not weaker than that of the pure limestone. Furthermore, owning to the weathering and unloading, the karst erosion of the marlite will reach certain depth of the slope, which is named infiltrated karst erosion. The karst erosion made the rock mass quality of slope or foundation worse in a large scale. The karst erosion geological disasters, taken place or not, has become the main restrictive factors to the social stability and economic development. Thus the karst erosion process and mechanism of marlite of Badong formation are studied as the main content of this dissertation. The weakening characteristic of rock mass mechanics parameters are studied along with the rock mass structure deformation and failure processes in the course of the karst erosion. At first, the conditions and influencing factors of the karst erosion are analyzed in the investigative region, on the basis of different karst erosion phenomenon of the marlite and different failure modes of slope. Then via indoor the karst erosion tests, it is analyzed that the karst erosion will change the rock mass composition and its structure. Through test, the different karst erosion phenomena between micro and macro have been observed, and the karst erosion mechanism of the marlite has been summarized. Damage theory is introduced to explain the feature of dissolution pore and the law of crack propagation in the marlite. By microscope and the references data, it can be concluded that the karst erosion process can be divided into rock minerals damage and rock structural damage. And the percent of karst erosion volume is named damage factor, which can be used to describe the quantify karst erosion degree of marlite. Through test, the rock mechanical properties in the different period of karst erosion are studied. Based on the damage mechanics theory and the test result, the relation between the karst erosion degree of marlite and weakening degree of mechanical properties is summarized. By numerical simulations, the karst erosive rock mass mechanics is verified. The conclusion is drawn as below: to the rock mass of marlite, the karst erosion damage made mechanics parameters variation, the deformation modulus, cohesion, and inter friction angle reduce as the negative exponent with the increasing of the karst erosion volume, however, the Poisson ratio increases as the positive exponent with the karst erosion volume increasing. It should be noticed that the deduced formulations are limited to the test data and certain conditions. It is suitable to the rock mass parametric weakening process after the karst erosion of marlite in Three Gorges Reservoir area. Based on the failure types of marlite slope in the field, the karst erosion and weathering process of rock mass are analyzed. And the evolution law of deformation and failure of the marlite mass is studied. The main failure feature of the marlite slope is the karst erosive structure subsidence mode in Three Gorges Reservoir area. The karst erosive structure subsidence mode is explained as follows: the rock mass undergoes the synthetic influence, such as weathering, unloading, corrosion, and so on, many pores and cavities have been formed in the rock mass interior, the rock mass quality is worsen and the rock mass structure is changed, and then the inherent structure of rock mass is collapsed under its gravity, therefore, the failure mode of compaction and subsidence take place. Finally, two examples are used to verify the rock mass parameters in Three Gorges Reservoir area, and the relationship between the marlite slope stability and the time of karst erosion is proposed.
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Intense tectonic renovation has occurred in the eastern continent of china since Mesozoic, as evidenced by the high heat flow, widespread magma extrusion and volcanic activities, and development of large sedimentary basins. To explain the cause and mechanism for the tectonic process in this period, some researchers have put forward various models, such as mantle plume, subduction of the Pacific slab, Yangtze Block-North China Block collision, etc. Their seismological evidence, however, is still scarce..During the period from 2000 to 2003, large temporary seismic arrays were established in North China by the Institute of the Geology and Geophysics, Chinese Academy of Sciences. Total 129 portable seismic stations were linearly emplaced across the western and eastern boundaries of the Bohai Bay Basin, and accumulated a large amount of high-quality data. Moreover, abundant data were also collected at the capital digital seismic network established in the ninth five-year period of national economic and social development. These provide an unprecedented opportunity for us to study the deep structure and associated geodynamic mechanism of lithospheric processes in North China using seismological techniques.Seismology is a kind of observation-based science. The development of seismic observations greatly promotes the improvement of seismologic theory and methodology. At the beginning of this thesis, I review the history of seismic observation progress, and present some routine processing techniques used in the array seismology. I also introduce two popular seismic imaging methods (receiver function method and seismic tomography).Receiver function method has been widely used to study the crustal and upper mantle structures, and many relevant research results have been published. In this thesis I elaborate the theory of this method, including the basic concept of receiver functions and the methodology for data pre-processing, stacking and migration. I also address some problems often encountered in practical applications of receiver function imaging.By using the teleseismic data collected at the temporary seismic arrays in North China, in particular, the traveltime information of P-to-S conversion and multiple reverberations of the Moho discontinuity, I obtain the distributions of the crustal thickness and the poisson ratio at the northwest boundary area of the Bohai Bay Basin and discuss the geological implications of the results.Through detailed intestigations on the crustal structural feature around the middle part of the Tanlu fault, considerable disparity in poisson ratios is found in the western and eastern sides of the Tanlu fault. Moreover, an obvious Moho offset is coincidently observed at the same surface location. A reasonable density model for the Tanlu fault area is also derived by simulating the observed gravity variations. Both receiver function study and gravity anomaly modeling suggest that the crustal difference between the western and eastern sides of the Tanlu fault is mainly resulted from their different compositions.With common conversion point imaging of receiver functions, I estimate the depths of the upper and lower boundaries of the mantle transition zone, i.e., the 410 and 660 km discontinuities, beneath most part of the North China continent The thickness of the transition zone (TTZ) in the study area is calculated by subtracting the depth of .410 km discontinuity from that of the 660km discontinuity. The resultant TTZ is 10-15 km larger in the east than in the west of the study area. Phase transitions at the 410 km and the 660 km discontinuities are known to have different Clapeyron slopes. Therefore, the TTZ is sensitive to the temperature changes in the transition zone. Previous studies have shown that the TTZ would be smaller in the mantle plume areas and become larger when the remnants of subducted slabs are present The hypothesis of mantle plume cannot give a reasonable interpretation to the observed TTZ beneath North China, Instead, the receiver function imaging results favor a dynamic model that correlates the thermal structure of the mantle transition zone and associated upper mantle dynamics of North China to the Pacific plate subduction process.
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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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O objetivo deste documento é mostrar o potencial da integração de um sistema de informações geográficas (SIG) com um modelo de probabilidade, usando a distribuição de Poisson, para espacializar variáveis discretas. Modelos estatísticos são ferramentas importantes no estudo de variáveis ambientais, principalmente com a crescente importância da valoração do capital ambiental. A distribuição do Poisson é um bom modelo estatístico para manejo de variáveis discretas, pois mostra seu comportamento. Um passo posterior seria saber como essas variáveis se comportam no espaço, mostrando sua distribuição espacial. Nesse caso, os sistemas de informações geográficas (SIG) são bastante eficientes (Miranda, 2005). Para testar o uso de ambas as ferramentas e mostrar sua eficiência, este trabalho traz uma implementação específica usando uma variável ambiental discreta, secas mensais.
Using an Outdoor Learning Space to Teach Sustainability and Material Processes in HE product Design.
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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