Spelling suggestions: "subject:"enclosure"" "subject:"inclosure""
121 |
Link Strength in Lake Littoral Food Webs: Net Effects of Small Sunfish and Larval DragonfliesJohnson, Dan M., Martin, Thomas H., Crowley, Philip H., Crowder, Larry B. 01 January 1996 (has links)
To show how predaceous fish and dragonflies affect benthic community structure, we conducted enclosure experiments in the littoral zone of Bays Mountain Lake, Tennessee. A 'natural' benthic assemblage was subjected to all combinations of 2 densities of 3 predator treatments - small sunfish, 0 or 4/m2; large dragonfly larvae, 0 or 15/m2; and dragonfly eggs at 2 densities, 90 or 900/m2. Treatments were assigned randomly in each of 6 spatiotemporal blocks. Net effects of predation over 4 mo show that small sunfish had 'strong' effects (>50% reduction of densities) on triclads, large daphnid cladocerans, and snails, and 'moderate' effects (50% > reduction > 25%) on small dragonflies and ostracods; all these effects were statistically significant, except the one on ostracods. Large dragonflies had moderate non-significant effects on triclads and ostracods. There were no significant increases in prey density associated with fish predation; but chydorid cladocerans and midge larvae showed 'weak' non-significant increases that might be caused by 'indirect effects' of fish predation on invertebrate predators or grazers. There were only 2 significant interaction terms indicative of 'higher-order interactions': Fish X Dragonfly on the large daphnid Simocephalus, and Fish X Egg Density on snails, which were associated with relatively low probabilities. In both cases, the net effect of dragonflies was to reduce prey densities more when fish were present.
|
122 |
Modélisation électromagnétique et homogénéisation de composites tissés pour applications en compatibilité électromagnétique. / Electromagnetic modeling and homogenization of woven composite materials for electromagnetic compatibility applications.Al achkar, Ghida 14 December 2018 (has links)
Les matériaux composites sont largement utilisés dans l'industrie automobile comme pièces de structure. Alliant légèreté et bonnes propriétés mécaniques, ils ont remplacé les métaux classiquement adoptés dans la fabrication de moyens de transport. Toutefois, l'emploi des matériaux composites doit tenir compte de leur comportement électromagnétique. En effet, les composites à fibres conductrices, généralement moins conducteurs que les métaux, engendrent une interaction avec les ondes électromagnétiques, différente de celle introduite par les alliages métalliques. Il s'avère donc important de développer des outils de modélisation permettant de mieux appréhender le comportement électromagnétique de matériaux composites, et d'éclairer les changements qu'apportent ces matériaux sur la distribution des champs, provenant d'une multitude de sources externes, au voisinage des systèmes mécatroniques. Par ailleurs, l'étude du comportement électromagnétique de matériaux composites permet de tirer parti de leurs propriétés mécaniques attractives afin d'alléger les boîtiers de blindage en gardant un niveau d'atténuation conforme aux normes de l'industrie. Cependant, la modélisation numérique de structures composites de grande taille, telles que les boîtiers de blindage, bien que classiquement adoptée pour les structures métalliques, est rendue complexe par le fait que les composites présentent des hétérogénéités à l'échelle microscopique, et que leurs mécanismes de blindage diffèrent de ceux des conducteurs homogènes. Le calcul numérique s'avère envisageable une fois le composite remplacé par un matériau homogène ayant une réponse identique face à une sollicitation électromagnétique. Ainsi, au travers de ce travail de thèse, nous proposons une technique d'homogénéisation permettant d'estimer les propriétés électriques équivalentes que nous appliquons aux composites à fibres conductrices unidirectionnelles et tissées. Les résultats obtenus sont utilisés pour la simulation numérique d'un boîtier de blindage. / Composite materials are widely used in the automotive industry as structural components. By combining lightness and robust mechanical properties, they are increasigly replacing the conventionnally used metallic alloys, for the manufacturing of vehicle parts. However, the use of composite materials is not without consequences on the electromagnetic behavior of these parts. Since carbon fiber reinforced composites are generally worse conductors of electricity than metals, they interact differently with the electromagnetic waves which surround them. It is therefore important to develop modeling tools to better understand the electromagnetic behavior of composite materials. This is to explain the changes that these materials bring to the distribution of waves, generated by a multitude of external sources, in the vicinity of mechatronic systems. On the other hand, the study of the electromagnetic behavior of composite materials makes it possible to determine the possibility of taking advantage of their attractive mechanical properties in order to further reduce the weight of electromagnetic shielding enclosures while maintaining a level of attenuation in accordance with the standards of the industry. However, numerical modeling of large composite structures, such as shielding enclosures, although conventionally adopted for metal structures, is hindered by the fact that composites exhibit heterogeneities at the microscopic scale. The numerical calculation becomes possible once the composite is replaced by a homogeneous material that exhibits an identical response to an identical electromagnetic solicitation. In this work, we present a homogenization technique, based on finite element simulation and an optimisation method, that computes an estimate of the equivalent electrical properties of unidirectional and woven fiber reinforced composites. The results are then used to simulate the shielding effectiveness of an enclosure constructed by combining composite materials and metallic alloys.
|
123 |
A Gentlemen's Benevolence: Symptoms of Class, Gender, and Social Change in Emma, Nicholas Nickleby, and The Mill on the FlossHammer, Aubrey Lea 10 July 2007 (has links) (PDF)
Austen, Dickens, and Eliot each responded to discussions of their time concerning class, gender, and social change. One of the ways they addressed these issues, and sought to find solutions to the problems facing their culture, was through benevolence. Knightley, in Emma, uses benevolence as a means of mediating self-interest and sympathy. By acting out of sympathy, through benevolence, he achieves the self-interested benefits of reinforcing the class system and achieving his romantic conquests. Likewise, Dickens' Nicholas Nickleby learns how to use benevolence as a means of social mobility from his mentors, the Cheerybles. Throughout Nicholas Nickleby the hero learns how to engage in benevolence out of sympathy, and by doing so he establishes himself as a gentleman and reaps social, economic, and romantic advantages. Eliot's Bob Jakin in The Mill on the Floss engages in benevolence out of true sympathy unhindered by self-interest. His freedom from social constraint and self-interest allows him to truly help Maggie Tulliver when no one else can. These authors' depictions of benevolence all illuminate ways that nineteenth-century literary authors sought to navigate the “Adam Smith Problem" of sympathy vs. self-interest. Benevolence, in these novels, is not disinterested (regardless of their motivation) but is influenced by the character's and author's perception of class, gender, and social change in the nineteenth century.
|
124 |
Heat Transfer Characteristics of Natural Convection within an Enclosure Using Liquid Cooling System.Gdhaidh, Farouq A.S. January 2015 (has links)
In this investigation, a single phase fluid is used to study the coupling between natural convection heat transfer within an enclosure and forced convection through computer covering case to cool the electronic chip. Two working fluids are used (water and air) within a rectangular enclosure and the air flow through the computer case is created by an exhaust fan installed at the back of the computer case. The optimum enclosure size configuration that keeps a maximum temperature of the heat source at a safe temperature level (85℃) is determined. The cooling system is tested for varying values of applied power in the range of 15−40𝑊.
The study is based on both numerical models and experimental observations. The numerical work was developed using the commercial software (ANSYS-Icepak) to simulate the flow and temperature fields for the desktop computer and the cooling system. The numerical simulation has the same physical geometry as those used in the experimental investigations. The experimental work was aimed to gather the details for temperature field and use them in the validation of the numerical prediction.
The results showed that, the cavity size variations influence both the heat transfer process and the maximum temperature. Furthermore, the experimental results
ii
compared favourably with those obtained numerically, where the maximum deviation in terms of the maximum system temperature, is within 3.5%. Moreover, it is seen that using water as the working fluid within the enclosure is capable of keeping the maximum temperature under 77℃ for a heat source of 40𝑊, which is below the recommended electronic chips temperature of not exceeding 85℃. As a result, the noise and vibration level is reduced. In addition, the proposed cooling system saved about 65% of the CPU fan power.
|
125 |
[pt] O MURO DA CASA COM TRÊS PÁTIOS: POR UMA CHAVE DE AUTONOMIA / [en] THE MASONRY-WALL FROM THREE COURTYARD HOUSE: BY AN AUTONOMY KEYNICOLLE ALVES CAETANO R DO PRADO 06 February 2023 (has links)
[pt] A Casa com Três Pátios é um projeto residencial não construído do
arquiteto Mies van der Rohe da década de 1930 e faz parte de um processo de
investigação tipológica de casas-pátio, de duração de quase dez anos da atividade
docente e profissional do arquiteto. O presente trabalho observa o desenho do muro
de alvenaria da casa sob a compreensão de um protagonismoprogressivo deste
elemento, desde seus primeiros estudos até sua última versão,associado ao
conceito de autonomia disciplinar. A partir da comparação entre as obras da série
investigativa e das executadas de Mies, é possível observar que omuro aos
poucos deixa de mediar a arquitetura com o terreno e passa a disputar o
protagonismo com o espaço interno da casa. / [en] The Three Courtyards House is an unbuilt residential project by architect
Mies van der Rohe from the 1930s. The house is also part of a process of
typological investigation of courtyard houses, lasting almost ten years of the
architect s teaching and professional activity. The present work observes the
design of the masonry wall of the house under the understanding of a progressive
protagonism of this element, from its first studies to its last version, associated with
the concept of architectural autonomy. Based on the comparison between the
works of the investigative series and Mies s executed works, it is possible to notice
that the masonry wall gradually ceases to mediate the architecture with the land
and starts to dispute the protagonism with the house s internal space.
|
126 |
La conservation autologue de sang de cordon ombilical : une ouverture sur une forme émergente de «citoyenneté biologique»Alary, Anouck 10 1900 (has links)
La transformation du sang de cordon ombilical en une précieuse source de cellules souches a, dès le début des années 1990, donné naissance à une industrie commerciale globale de conservation faisant désormais concurrence à un large réseau de conservation public. Ce mémoire cherche à comprendre et à expliquer les soubassements socio-culturels liés à l’émergence de cette industrie, ainsi qu’à mieux cerner les enjeux éthiques et politiques qu’elle pose. En exposant en premier lieu la manière dont les institutions publiques de conservation de sang de cordon se définissent, et sont généralement définies par les comités bioéthiques, comme étant porteuses des valeurs d’altruisme et de solidarité nationale traditionnellement liées au modèle « redistributif » d’échange de sang et d’organes né au lendemain de la Seconde Guerre mondiale, nous problématisons la manière innovatrice par laquelle les banques privées structurent le rapport entre les mères et leurs propres produits biologiques comme l’expression d’une reconfiguration du lien social et politique caractérisée par l’émergence de nouvelles socialisés. L’hypothèse au coeur de ce mémoire est que celles-ci peuvent être comprises comme l’aboutissant de l‘espoir collectivement partagé par les consommatrices d’améliorer leur propre condition biologique familiale, étant lui-même le fruit d’une financiarisation croissante des sciences du vivant. En analysant le discours « promissif » que représente le matériel promotionnel des banques autologues, notre objectif est alors d’identifier la manière par laquelle les multiples potentialités attribuées au sang de cordon définissent des subjectivités maternelles caractérisées par des obligations morales spécifiques. / The recent transformation of cord blood to a precious source of stem cells has given rise to a global commercial industry of conservation, which is now competing with a large network of public cord blood banks. This dissertation explores the socio-cultural context surrounding the emergence of that industry and aims at elucidating the ethical and political concerns that it generates. It begins by examining how public cord blood banks define themselves (and are defined by ethical commitees) as purveyors of values such as altruism and national solidarity -that is, values which were traditionally linked to the « redistributive » model of human blood and organs exchanges that emerged after World War II. It next argues that private banks are bringing about a radical transformation of the relationship between mothers and their biological “products”. This dissertation suggests that this innovative model of exchange is an expression of contemporary reconfigurations of the very notion of community, which is now characterized by what we call new forms of “biosociality”. Our hypothesis is that these new socialities can be understood as the consequence of a collective hope to improve familial biological conditions, which is itself the product of the growing financiarization of life sciences. By way of a foray into the « promissive » discourse employed by private banks for their promotional material, the dissertation attemps to identify how these potentialities attributed to cord blood define new maternal subjectivities characterized by specific moral duties and obligations.
|
127 |
Att fånga det flyktiga : Om existentiell mening och objektivitetEdlund, Lena January 2008 (has links)
<p>This work attempts an answer to two questions. Firstly, is it possible to experience meaning when everything is transient? And secondly, in what way is objectivity possible when it comes to such phenomena as existential meaning? The questions originate from our insideperspective, and it is from what we have experienced ourselves that we try to make intelligible existential meaning. We are to a great extent part of the context in which we live. Our ability to contemplate our situation and our own contemplation is taking place in interplay with others. To make room for the small things meaningful in life, the expression existential meaning is used. In this expression both the meaningless and the meaningful are included, since both are needed for our understanding of meaning. Without the Other and that which is different, the individual person’s formation of existential meaning becomes just more of the same, it becomes an enclosure in the present. The encounter with the Other makes room for that which is different to break through.</p><p>Objectivity is possible when it comes to existential meaning, if one views objectivity as a process between people. It is performed in conversation. Those who converse, refer to their bodily experiences of the Time that remains and help each other, using language as the tool, to formulate their experiences. They compare each others’ manifestations of existential meaning,</p><p>and with the help of language they go further in the formation of what is meaningless and meaningful. Their conversations imply a normative presupposition that they can justify the claims that they make. Because it is actually not possible to make intelligible existential meaning in words other than by doing it as a mix of descriptions of that which is manifesting itself and linguistic rewritings in the form of stories. This expression of objectivity has a normative aspect, namely in relation to the possibility that we can be wrong. Therefore, we need each other in the act of judging, and together we are guided by the fact that it later on can emerge things that show that our judgment has not been fully correct. </p>
|
128 |
Computer-Assisted Proofs and Other Methods for Problems Regarding Nonlinear Differential EquationsFogelklou, Oswald January 2012 (has links)
This PhD thesis treats some problems concerning nonlinear differential equations. In the first two papers computer-assisted proofs are used. The differential equations there are rewritten as fixed point problems, and the existence of solutions are proved. The problem in the first paper is one-dimensional; with one boundary condition given by an integral. The problem in the second paper is three-dimensional, and Dirichlet boundary conditions are used. Both problems have their origins in fluid dynamics. Paper III describes an inverse problem for the heat equation. Given the solution, a solution dependent diffusion coefficient is estimated by intervals at a finite set of points. The method includes the construction of set-valued level curves and two-dimensional splines. In paper IV we prove that there exists a unique, globally attracting fixed point for a differential equation system. The differential equation system arises as the number of peers in a peer-to-peer network, which is described by a suitably scaled Markov chain, goes to infinity. In the proof linearization and Dulac's criterion are used.
|
129 |
Advances in Thermal Insulation : Vacuum Insulation Panels and Thermal Efficiency to Reduce Energy Usage in BuildingsThorsell, Thomas January 2012 (has links)
We are coming to realize that there is an urgent need to reduce energy usage in buildings and it has to be done in a sustainable way. This thesis focuses on the performance of the building envelope; more precisely thermal performance of walls and super insulation material in the form of vacuum insulation. However, the building envelope is just one part of the whole building system, and super insulators have one major flaw: they are easily adversely affected by other problems in the built environment. Vacuum Insulation Panels are one fresh addition to the arsenal of insulation materials available to the building industry. They are composite material with a core and an enclosure which, as a composite, can reach thermal conductivities as low as 0.004 W/(mK). However, the exceptional performance relies on the barrier material preventing gas permeation, maintaining a near vacuum into the core and a minimized thermal bridge effect from the wrapping of barrier material round the edge of a panel. A serpentine edge is proposed to decrease the heat loss at the edge. Modeling and testing shows a reduction of 60% if a reasonable serpentine edge is used. A diffusion model of permeation through multilayered barrier films with metallization coatings was developed to predict ultimate service life. The model combines numerical calculations with analytical field theory allowing for more precise determination than current models. The results using the proposed model indicate that it is possible to manufacture panels with lifetimes exceeding 50 years with existing manufacturing. Switching from the component scale to the building scale; an approach of integrated testing and modeling is proposed. Four wall types have been tested in a large range of environments with the aim to assess the hygrothermal nature and significance of thermal bridges and air leakages. The test procedure was also examined as a means for a more representative performance indicator than R-value (in USA). The procedure incorporates specific steps exposing the wall to different climate conditions, ranging from cold and dry to hot and humid, with and without a pressure gradient. This study showed that air infiltration alone might decrease the thermal resistance of a residential wall by 15%, more for industrial walls. Results from the research underpin a discussion concerning the importance of a holistic approach to building design if we are to meet the challenge of energy savings and sustainability. Thermal insulation efficiency is a main concept used throughout, and since it measures utilization it is a partial measure of sustainability. It is therefore proposed as a necessary design parameter in addition to a performance indicator when designing building envelopes. The thermal insulation efficiency ranges from below 50% for a wood stud wall poorly designed with incorporated VIP, while an optimized design with VIP placed in an uninterrupted external layer shows an efficiency of 99%, almost perfect. Thermal insulation efficiency reflects the measured wall performance full scale test, thus indicating efficiency under varied environmental loads: heat, moisture and pressure. The building design must be as a system, integrating all the subsystems together to function in concert. New design methodologies must be created along with new, more reliable and comprehensive measuring, testing and integrating procedures. New super insulators are capable of reducing energy usage below zero energy in buildings. It would be a shame to waste them by not taking care of the rest of the system. This thesis details the steps that went into this study and shows how this can be done. / QC 20120228
|
130 |
Att fånga det flyktiga : Om existentiell mening och objektivitetEdlund, Lena January 2008 (has links)
This work attempts an answer to two questions. Firstly, is it possible to experience meaning when everything is transient? And secondly, in what way is objectivity possible when it comes to such phenomena as existential meaning? The questions originate from our insideperspective, and it is from what we have experienced ourselves that we try to make intelligible existential meaning. We are to a great extent part of the context in which we live. Our ability to contemplate our situation and our own contemplation is taking place in interplay with others. To make room for the small things meaningful in life, the expression existential meaning is used. In this expression both the meaningless and the meaningful are included, since both are needed for our understanding of meaning. Without the Other and that which is different, the individual person’s formation of existential meaning becomes just more of the same, it becomes an enclosure in the present. The encounter with the Other makes room for that which is different to break through. Objectivity is possible when it comes to existential meaning, if one views objectivity as a process between people. It is performed in conversation. Those who converse, refer to their bodily experiences of the Time that remains and help each other, using language as the tool, to formulate their experiences. They compare each others’ manifestations of existential meaning, and with the help of language they go further in the formation of what is meaningless and meaningful. Their conversations imply a normative presupposition that they can justify the claims that they make. Because it is actually not possible to make intelligible existential meaning in words other than by doing it as a mix of descriptions of that which is manifesting itself and linguistic rewritings in the form of stories. This expression of objectivity has a normative aspect, namely in relation to the possibility that we can be wrong. Therefore, we need each other in the act of judging, and together we are guided by the fact that it later on can emerge things that show that our judgment has not been fully correct.
|
Page generated in 0.0652 seconds