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‣ Study of the decomposition of phase stabilized ammonium nitrate (PSAN) by simultaneous thermal analysis: determination of kinetic parameters

Simões, P. N.; Pedroso, L. M.; Portugal, A. A.; Campos, J. L.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
Português
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Ammonium nitrate (AN) has been extensively used both in explosive and propellant formulations. Unlike AN, there is a lack of information about the thermal decomposition and related kinetic analysis of phase stabilized ammonium nitrate (PSAN). Simultaneous thermal analysis (DSC-TG) has been used in the thermal characterisation of a specific type of PSAN containing 1.0% of NiO (stabilizing agent) and 0.5% of Petro (anti-caking agent) as additives. Repeated runs covering the nominal heating rates range from 2.5 to 20 K min-1 allowed to conclude on the good reproducibility of the main features of the thermal behavior of PSAN, i.e., two phase transitions, melting and decomposition. Non-isothermal kinetic analysis has been used to estimated the Arrhenius parameters of the decomposition process by applying both a single curve method and two isoconversion methods to the TG data. The results are discussed considering the range of applicability of the methods as well as the influence of the experimental conditions and/or techniques in the kinetic analysis results in a broader sense. A systematic approach based on the isoconversion methods results and statistical tools has been adopted to obtain reliable estimates of the Arrhenius parameters for the thermal decomposition of PSAN. Under the condition of study...

‣ The importance of mesofauna and decomposition environment on leaf decomposition in three forests in southeastern Brazil

Castanho, Camila de Toledo; Lorenzo, Leda; Oliveira, Alexandre Adalardo de
Fonte: SPRINGER; DORDRECHT Publicador: SPRINGER; DORDRECHT
Tipo: Artigo de Revista Científica
Português
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We examined the effects of soil mesofauna and the litter decomposition environment (above and belowground) on leaf decomposition rates in three forest types in southeastern Brazil. To estimate decomposition experimentally, we used litterbags with a standard substrate in a full-factorial experimental design. We used model selection to compare three decomposition models and also to infer the importance of forest type, decomposition environment, mesofauna, and their interactions on the decomposition process. Rather than the frequently used simple and double-exponential models, the best model to describe our dataset was the exponential deceleration model, which assumed a single organic compartment with an exponential decrease of the decomposition rate. Decomposition was higher in the wet than in the seasonal forest, and the differences between forest types were stronger aboveground. Regarding litter decomposition environment, decomposition was predominantly higher below than aboveground, but the magnitude of this effect was higher in the seasonal than in wet forests. Mesofauna exclusion treatments had slower decomposition, except aboveground into the Semi-deciduous Forest, where the mesofauna presence did not affect decomposition. Furthermore...

‣ "Fatores determinantes no processo de decomposição em florestas do Estado de São Paulo". ; Determinant factors of decomposition process in São Paulo State forests

Castanho, Camila de Toledo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/08/2005 Português
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A atividade de decomposição constitui-se em importante indicador do padrão funcional dos ecossistemas, pois controla processos básicos relacionados à disponibilidade de nutrientes e produtividade. Salienta-se a importância das características climáticas, edáficas, da qualidade da serapilheira e da fauna do solo como determinantes no processo de decomposição. No entanto, a importância de cada um destes fatores varia em escalas de tempo e espaço. O objetivo deste trabalho foi avaliar a importância de alguns fatores determinantes na decomposição em trechos representativos dos principais ecossistemas florestais do Estado de São Paulo. Para tanto foram conduzidos dois experimentos independentes. O primeiro, aqui denominado Experimento Exóticas, examinou os efeitos do tipo florestal e da fauna do solo sobre a decomposição de folhas de uma espécie exótica (Laurus nobilis L.) em duas florestas úmidas (Floresta de Restinga do Parque Estadual da Ilha do Cardoso e Floresta Atlântica de Encosta do Parque Estadual Carlos Botelho) e uma floresta estacional (Floresta Estacional Semidecidual da Estação Ecológica de Caetetus). Os efeitos destes fatores foram testados em duas situações: acima e abaixo da superfície simulando então o ambiente de decomposição de folhas e raízes respectivamente. O tipo florestal apresenta efeito superior à fauna acima da superfície...

‣ Estudo dos mecanismos de quimi-excitação na decomposição induzida de peróxidos: uma comparação entre sistemas inter e intramoleculares; Studies on the chemiexcitation mechanisms in induced peroxide decomposition: a comparison of inter and intramolecular systems

Oliveira, Marcelo Almeida de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/05/2007 Português
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Foram sintetizados, purificados e caracterizados os peróxidos cíclicos: peróxido de difenoíla (1), dimetil-1,2-dioxetanona (2), e spiro-adamantil α-peróxi lactona (3), e determinados seus parâmetros de quimiluminescência. Foram redeterminados os rendimentos quânticos singlete na decomposição catalisada de 1 e 2 em condições análogas as utilizadas anteriormente na literatura, obtendo-se valores várias ordens de grandeza menores que os inicialmente relatados para estes sistemas padrão para a formulação do mecanismo Luminescência Iniciada Quimicamente por Troca de Elétron (Chemically Initiated Electron Exchange Luminescence - CIEEL). O efeito de gaiola de solvente, utilizando-se o sistema binário tolueno/difenilmetano, sobre o rendimento quântico na decomposição de 1 catalisada por rubreno, mostrou-se consideravelmente menor para este sistema intermolecular do que o observado no sistema intramolecular da decomposição induzida de 1,2-dioxetanos fenóxi-substituidos. Foram determinados pela primeira vez os parâmetros de quimiluminescência na decomposição unimolecular e catalisada da spiro-adamantil α-peróxi lactona (3), mostrando que esta é a α-peróxi lactona mais estável sintetizada e estudada até o momento. Este peróxido é sujeito à decomposição catalisada por ativadores adequados...

‣ Effects of zinc on leaf decomposition by fungi in streams : studies in microcosms

Duarte, Sofia; Pascoal, Cláudia; Cássio, Fernanda
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /07/2004 Português
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Resumo da comunicação apresentada no XII Congresso da Association Española de Limnología - IV Congresso Ibérico de Limnologia. CIMAR, Universidade do Porto, 5-9 Julho 2004.; The ubiquitous presence of aquatic fungi in metal polluted streams have increased interest on the effect of heavy metals on fungi during decomposition of organic matter. In this work, microcosm experiments were used to assess the effects of zinc on leaf decomposition by aquatic fungi. In parallel, leaf decomposition was followed in the stream to validate microcosm results. Stream experiments were carried out at the source of the Este River (Northwest Portugal). This river flows through the city of Braga and its Industrial Park where heavy metals, including zinc, become a problem in both stream water and sediments. Leaves colonized for 15 days in the stream were collected and exposed to zinc concentrations within the range occurring in either pristine or impacted streams. To evaluate zinc effects on the natural fungal assemblages, leaf mass loss, fungal biomass (from ergosterol concentration) and production (rates of [1-14C]acetate incorporation into ergosterol), sporulation rates and diversity of aquatic hyphomycetes were determined. At the source of the Este River the decomposition rate of alder leaves was 0.0741 d-1 and a total of 18 aquatic hyphomycete species were recorded during leaf immersion in the stream. Articulospora tetracladia was the dominant species...

‣ Kinetic analysis for non-isothermal decomposition of unirradiated and γ-irradiated indium acetyl acetonate

Mahfouz,Refaat Mohammed; Al-Ahmari,Sharifa; Al-Fawaz,Amaal; Al-Othman,Zaid; Warad,Ismail Khaleel; Siddiqui,Mohammed Rafiq Hussain
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2011 Português
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Kinetic studies for the non-isothermal decomposition of un-irradiated and γ-irradiated indium acetyl acetonate In(acac)3 with 10² kGy total γ-ray dose were carried out in static air. The results showed that the decomposition proceeds in one major step in the temperature range of 150-250 °C with the formation of In2O3 as solid residue. The non-isothermal data for un-irradiated and γ-irradiated In(acac)3 were analysed using linear Flynn-Wall-Ozawa (FWO) and nonlinear Vyazovkin (VYZ) iso-conversional methods. The results of application of these free models on the investigated data showed a systematic dependence of Ea on α indicating a simple decomposition process. No significant changes were observed in both decomposition behaviour and (Eα-α) dependency between unirradiated and γ-irradiated In(acac)3. Calcination of In(acac)3 at 400 °C for 5 hours led to the formation of In2O3 monodispersed nanoparticles. X-ray diffraction, FTIR and SEM techniques were employed for characterization of the synthesised nanoparticles. This is the first attempt to prepare In2O3 nanoparticles by solid state thermal decomposition of In(acac)3.

‣ L’utilisation de la polarimétrie radar et de la décomposition de Touzi pour la caractérisation et la classification des physionomies végétales des milieux humides : le cas du Lac Saint-Pierre.

Gosselin, Gabriel
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
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Les milieux humides remplissent plusieurs fonctions écologiques d’importance et contribuent à la biodiversité de la faune et de la flore. Même s’il existe une reconnaissance croissante sur l’importante de protéger ces milieux, il n’en demeure pas moins que leur intégrité est encore menacée par la pression des activités humaines. L’inventaire et le suivi systématique des milieux humides constituent une nécessité et la télédétection est le seul moyen réaliste d’atteindre ce but. L’objectif de cette thèse consiste à contribuer et à améliorer la caractérisation des milieux humides en utilisant des données satellites acquises par des radars polarimétriques en bande L (ALOS-PALSAR) et C (RADARSAT-2). Cette thèse se fonde sur deux hypothèses (chap. 1). La première hypothèse stipule que les classes de physionomies végétales, basées sur la structure des végétaux, sont plus appropriées que les classes d’espèces végétales car mieux adaptées au contenu informationnel des images radar polarimétriques. La seconde hypothèse stipule que les algorithmes de décompositions polarimétriques permettent une extraction optimale de l’information polarimétrique comparativement à une approche multipolarisée basée sur les canaux de polarisation HH...

‣ The kinetics and induced decomposition on the thermal decomposition of hydroperoxides /

Tse, K. M.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
Português
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This project is focussed on the thermsLl decomposition of t-butyl hydroperoxide and sec-butyl hydroperoxide at 120°C to 160°C in three alcohol solvents. These are methanol, ethajiol and isopropyl alcohol. The aim of the project was to examine the process of induced decomposition. Thermal decomposition of t-hutyl hydroperoxide and sec-butyl hydroperoxide indicate that these reactions have first-order kinetics with activation energies on the order of 20 to 28 K cal/mole, Styrene was used as a free radical trap to inhibit the induced decomposition. The results permitted calculation of how much induced decomposition occurred in its absence. The experimental resvilts indicate that the induced decomposition is important for t-butyl hydroperoxide in alcohol solvents, as shown by both the reaction rate suid product studies. But sec-butyl hydroperoxide results show that the concerted mechanism for the interaction of two sec-butylperoxy radicals occurs in addition to the induced decomposition. Di-sodium E.D,T.A. was added to reduce possible effects of trace transition metal ion .impurities. The result of this experiment were not as expected. The rate of hydroperoxide decomposition was about the same but was zero-order in hydroperoxide concentration.

‣ Accounting for Mexican Income Inequality during the 1990s

De Hoyos, Rafael E.
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Português
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The author implements several inequality decomposition methods to measure the extent to which total household income disparities can be attributable to sectoral asymmetries and differences in skill endowments. The results show that at least half of total household inequality in Mexico is attributable to incomes derived from entrepreneurial activities, an income source rarely scrutinized in the inequality literature. He shows that education (skills) endowments are unevenly distributed among the Mexican population, with positive shifts in the market returns to schooling associated with increases in inequality. Asymmetries in the allocation of education explain around 20 percent of overall household income disparities in Mexico during the 1990s. Moreover, the proportion of inequality attributable to education endowments increases during stable periods and reduces during the crisis. This pattern is explained by shifts in returns to schooling rather than changes in the distribution of skills. Applying the same techniques to decompose within-sector income differences...

‣ Dynamics of plant residue decomposition and nutrient release.

Duong, Tra Thi Thanh
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2009 Português
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Proper management of soil organic matter (SOM) contributes to increasing plant productivity and reducing dependency on mineral fertilizers. Organic matter is widely regarded as a vital component of a healthy soil as it plays an important role in soil physical, chemical and biological fertility. Plant residues are the primary source of SOM. Therefore, proper SOM management requires a better understanding of plant residue decomposition kinetics in order to synchronize nutrient release during decomposition and plant uptake and prevent nutrient losses. In natural and managed ecosystems, residues are added frequently to soil, in the form of dead roots and litter fall of plant species with different C/N ratios. However, in most studies on residue decomposition, residues with different C/N ratios are added once and the effect of the presence of plants on residue decomposition is rarely investigated. In this project, four experiments were carried out with different objectives in order to close these knowledge gaps. The aim of the first experiment was to investigate the effect of frequent wheat residue addition on C mineralization and N dynamics. The experiment consisted of five treatments with different frequency of residue addition (2% w/w of wheat residues in total): once (100%W)...

‣ Effect of clay on plant residue decomposition.

Umar, Shariah
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010 Português
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Plant residues added to soil are a source of nutrients for plants and soil organisms and increase soil organic matter which has an important role in improving soil structure and fertility, hence maintaining soil quality for sustainable agriculture. In order to utilize plant residues for increasing soil organic matter more effectively, it is necessary to understand the mechanisms of plant residue decomposition. Soil organic matter decomposition is influenced by several factors such as plant residue quality, temperature, water availability, soil structure and soil texture, particularly clay content. The interaction of clay and decomposition of organic matter has been studied in the past. Nevertheless, many studies investigated this interaction in natural soil or under field conditions over long periods of time. Variation in environmental factors may influence the interaction of clay and decomposition of organic matter, thus in most previous studies their effect cannot be separated from the direct effect of clay on decomposition. To study the direct effect of clay on organic matter decomposition, four experiments with different objectives were carried out using isolated natural clay, under controlled conditions (e.g. temperature and organic matter input) and a short incubation period (approximately one month). All experiments were carried out using a sand matrix to which different clay types...

‣ Decomposition and disarticulation of kangaroo carcasses in caves at Naracoorte, South Australia

Reed, E.H.
Fonte: Prometheus Press Publicador: Prometheus Press
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
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This paper presents the results of a study of decomposition and disarticulation of kangaroo carcasses in caves at Naracoorte, South Australia. Carcasses were placed in two caves and observed over a period of nearly three years. Decomposition progressed rapidly within the caves with almost immediate infestation by blowflies and fungi. Invertebrate activity had ceased by 28 months; however, fungal colonisation continued for the course of the study period. Decomposition, skeletonisation and disarticulation were complete by 600 days. The results suggest that temperature and humidity play an important role in decomposition as this directly affects the activity of invertebrate and fungal decomposers. The position of the carcass within the cave influences the degree of dispersal of remains in pitfall caves. Disarticulation sequences for the experimental carcasses compare with those for kangaroo skeletons on the land surface in semi-arid South Australia, suggesting that regardless of environment, anatomy is a key factor in determining disarticulation sequence. The results of this study have applications for the assessment of stratigraphic integrity and reworking of fossil deposits in caves at Naracoorte and elsewhere.; Elizabeth Reed

‣ 基于奇异值分解的动态光散射反演算法; An inversion algorithm of dynamic light scattering based on singular value decomposition

Yu, X.F.; Yang, H.; Yang, H.M.; Zheng, G.; Li, J.; Hu, H.Q.; Biggs, M.
Fonte: Kexue Chubanshe Publicador: Kexue Chubanshe
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
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针对动态光散射颗粒测量法在反演多分散系粒径分布时,算法需要先验信息或者解的约束条件的问题,提出了一种基于奇异值分解的动态光散射反演算法.首先利用多分散颗粒系光强自相关函数构造Hankel矩阵;其次对矩阵进行奇异值分解;再次根据奇异值的大小分布,确定噪音级别,重建矩阵的秩;最后对新的矩阵进行特征值分解,得到颗粒的粒径分布.采样两种和三种不同粒径的颗粒系进行了实验,结果显示:在没有任何先验信息和对解的约束条件下,该方法对两种粒径的颗粒系测量取得了较好的效果.但对于三种粒径的颗粒系测量效果并不理想,虽然能分辨出不同的三种粒径,但测量结果偏差较大,特别是小颗粒的粒径.通过分析认为主要原因是小颗粒的散射光容易被大颗粒阻挡.; YU Xiang-fei, YANG Hui, YANG Hai-ma, ZHENG Gang, LI Jun, HU Heng-qing, Mark BIGGS; English Title: An inversion algorithm of dynamic light scattering based on singular value decomposition. English Abstract: To solve the problem that the traditional inversion of dispersion particle size distribution with the method of dynamic light scattering requires prior knowledge or constraints for the solution...

‣ Climate change may reduce litter decomposition while enhancing the contribution of photodegradation in dry perennial Mediterranean grasslands

ALMAGRO María; MAESTRE Fernando T.; MARTINEZ LOPEZ JAVIER; VALENCIA Enrique; REY Ana
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Articles in periodicals and books Formato: Printed
Português
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Plant litter decomposition plays a key role in ecosystem function: it is the main source for the formation of soil organic matter as well as the primary source of soil nutrients, and a key component of the carbon balance of terrestrial ecosystems. Understanding how solar UV radiation will affect leaf litter decomposition and how it will interact with climate change drivers is fundamental to predict how soil and ecosystem biogeochemical cycles will respond to a warmer drier world. We carried out a litter decomposition experiment in the field to investigate the role of UV radiation and its interaction with increased temperature and decreased precipitation using standing litter and litter on the ground of Stipa tenacissima, a dominant species in semiarid Mediterranean perennial grasslands. Experimental plots (n = 8) consisted of: increased air temperature (3 oC on average), decreased precipitation (35% average decreased), and increased air temperature plus decreased precipitation. UV radiation was manipulated using specially designed screens made by acrylic or polycarbonate that either passed or blocked 90% of the UV radiation, respectively. In addition, two positions simulating “standing dead litter” and “litter on the ground” were used. All climate change manipulation treatments decreased litter decomposition. In particular...

‣ A novel method for EMG decomposition based on matched filters

Siqueira Júnior,Ailton Luiz Dias; Soares,Alcimar Barbosa
Fonte: Sociedade Brasileira de Engenharia Biomédica Publicador: Sociedade Brasileira de Engenharia Biomédica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2015 Português
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Introduction Decomposition of electromyography (EMG) signals into the constituent motor unit action potentials (MUAPs) can allow for deeper insights into the underlying processes associated with the neuromuscular system. The vast majority of the methods for EMG decomposition found in the literature depend on complex algorithms and specific instrumentation. As an attempt to contribute to solving these issues, we propose a method based on a bank of matched filters for the decomposition of EMG signals. Methods Four main units comprise our method: a bank of matched filters, a peak detector, a motor unit classifier and an overlapping resolution module. The system’s performance was evaluated with simulated and real EMG data. Classification accuracy was measured by comparing the responses of the system with known data from the simulator and with the annotations of a human expert. Results The results show that decomposition of non-overlapping MUAPs can be achieved with up to 99% accuracy for signals with up to 10 active motor units and a signal-to-noise ratio (SNR) of 10 dB. For overlapping MUAPs with up to 10 motor units per signal and a SNR of 20 dB, the technique allows for correct classification of approximately 71% of the MUAPs. The method is capable of processing...

‣ Applications of the Strong Splitter Theorem: decomposition results

Kingan, S. R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/08/2014 Português
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We use the Strong Splitter Theorem to decompose the excluded minor class of binary matroids with no $E_4$-minor. Using this theorem we can get the 3-decomposers and the extremal internally 4-connected matroids as well as any other important matroids in the class. The matroid $E_4$ is a self-dual 10-element binary 3-connected matroid that plays a useful role in structural results. It is a single-element coextension of $P_9$, which is a single-element extension of the 4-wheel. We show that the extremal matroids in this class are the binary rank-$r$ spikes $Z_r$, the rank 3 and 4 projective geometries $F_7$ and $PG(3,2)$, respectively, the 17-element internally 4-connected matroid $R_{17}$, and one 12-element rank-6 matroid. All the other 3-connected members have $P_9$ or $P_9^*$ as 3-decomposers. As immediate corollaries we get decomposition results for $EX[P_9^*]$ and $EX[P_9]$ as well as the internally 4-connected members of these classes.

‣ Decomposition results for stochastic storage processes and queues with alternating L\'evy inputs

Boxma, Onno; Kella, Offer
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/10/2012 Português
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In this paper we generalize known workload decomposition results for L\'{e}vy queues with secondary jump inputs and queues with server vacations or service interruptions. Special cases are polling systems with either compound Poisson or more general L\'{e}vy inputs. Our main tools are new martingale results, which have been derived in a companion paper.; Comment: 16 pages. arXiv admin note: substantial text overlap with arXiv:1112.4756

‣ Drought-resistant fungi control soil organic matter decomposition and its response to temperature

Yuste, J.C.; Peñuelas, Josep; Sardans, Jordi
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2011 Português
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Microbial-mediated decomposition of soil organic matter (SOM) ultimately makes a considerable contribution to soil respiration, which is typically the main source of CO2 arising from terrestrial ecosystems. Despite this central role in the decomposition of SOM, few studies have been conducted on how climate change may affect the soil microbial community and, furthermore, on how possible climate-change induced alterations in the ecology of microbial communities may affect soil CO2 emissions. Here we present the results of a seasonal study on soil microbial community structure, SOM decomposition and its temperature sensitivity in two representative Mediterranean ecosystems where precipitation/throughfall exclusion has taken place during the last 10 years. Bacterial and fungal diversity was estimated using the terminal restriction fragment length polymorphism technique. Our results show that fungal diversity was less sensitive to seasonal changes in moisture, temperature and plant activity than bacterial diversity. On the other hand, fungal communities showed the ability to dynamically adapt throughout the seasons. Fungi also coped better with the 10 years of precipitation/throughfall exclusion compared with bacteria. The high resistance of fungal diversity to changes with respect to bacteria may open the controversy as to whether future ‘drier conditions’ for Mediterranean regions might favor fungal dominated microbial communities. Finally...

‣ Ammonia decomposition on NiPt supported on ??-alumina : a study of stability of real catalysts

Weiner, Jacob
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Chen, Jingguan G; Vlachos, Dionisios G.; Ammonia decomposition is an important reaction due to its impact that it will have on the hydrogen economy. Hydrogen has been found to be a possible source of alternative energy with the application of hydrogen fuel cells. However, the major difficulty with hydrogen, as an alternative energy source, is its low energy density. Hydrogen is a low-density gas, and in order for its use in automobiles to be economically plausible, large tanks under high pressure would have to be employed. The result would limit space available in automobiles for other purposes and pose significant safety issues. As an alternative ammonia has been proposed as a means to store hydrogen chemically, due to its increased energy density. At moderate pressures (~9 atm) ammonia is a liquid, and could be adapted into the current liquid fuel infrastructure. In addition, the decomposition of ammonia would not produce carbon monoxide, a known poison of fuel cell electrodes. Thus, the ammonia decomposition reaction is one piece of the mechanism that could make hydrogen a viable alternative energy source. The work of Hansgen et al. examined ammonia decomposition through computational studies and surface science experiments on monolayer bimetallic surfaces. The Ni-Pt-Pt(111) configuration of NiPt was found to show favorable results for ammonia decomposition. In a reducing environment...

‣ Structural and decomposition results for binet matrices, bidirected graphs and signed-graphic matroids.

Papalamprou, Konstantinos
Fonte: London School of Economics and Political Science Thesis Publicador: London School of Economics and Political Science Thesis
Tipo: Thesis; NonPeerReviewed Formato: application/pdf
Publicado em //2009 Português
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In this thesis we deal with binet matrices and the class of signed-graphic matroids which is the class of matroids represented over R by binet matrices. The thesis is divided in three parts. In the first part, we provide the vast majority of the notions used throughout the thesis and some results regarding the class of binet matrices. In this part, we focus on the class of linear and integer programming problems in which the constraint matrix is binet and provide methods and algorithms which solve these problems efficiently. The main new result is that the existing combinatorial methods can not solve the {lcub}0, 1/2{rcub}-separation problem (special case of the well known separation problem) with integral binet matrices. The main new results of the whole thesis are provided in the next two parts. In the second part, we present a polynomial time algorithm to construct a bidirected graph for any totally unimodular matrix B by finding node-edge incidence matrices Q and S such that QB = S. Seymour's famous decomposition theorem for regular matroids states that any totally unimodular matrix can be constructed through a series of composition operations called k-sums starting from network matrices and their transposes and two compact representation matrices B1 and B2 of a certain ten element matroid. Given that B1 and B2 are binet matrices...