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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
ENG
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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...

Pozzolanic behavior of bamboo leaf ash: Characterization and determination of the kinetic parameters

VILLAR-COCINA, Ernesto; MORALES, Eduardo Valencia; SANTOS, Sergio F.; SAVASTANO JR., Holmer; FRIAS, Moises
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
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The paper presents a characterization and study of the pozzolanic behavior between calcium hydroxide (CH) and bamboo leaf ash (BLAsh), which was obtained by calcining bamboo leaves at 600 degrees C for 2 h in a laboratory electric furnace. To evaluate the pozzolanic behavior the conductometric method was used, which is based on the measurement of the electrical conductivity in a BLAsh/CH solution with the reaction time. Later, the kinetic parameters are quantified by applying a kinetic-diffusive model. The kinetic parameters that characterize the process (in particular, the reaction rate constant and free energy of activation) were determined with relative accuracy in the fitting process of the model. The pozzolanic activity is quantitatively evaluated according to the values obtained of the kinetic parameters. Other experimental techniques, such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), were also employed. The results show that this kind of ash is formed by silica with a completely amorphous nature and a high pozzolanic activity. The correlation between the values of free energy of activation (Delta G(#)) and the reaction rate constants (K) are in correspondence with the theoretical studies about the rate processes reported in the literature. (C) 2010 Elsevier Ltd. All rights reserved.; CAPES (Brazil)[031/07]

Caracterização cinética da (Na, K)-ATPase da fração microsomal do tecido branquial do ermitão intertidal Clibanarius vittatus; Kinetic characterization of gill microsomal (Na+,K+)- ATPase from intertidal hermit crab Clibanarius vittatus

Sivieri, Rubia Regina Gonçalves
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 23/03/2007 PT
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A (Na+,K+)-ATPase presente no tecido branquial dos crustáceos osmorreguladores é um componente essencial do sistema de regulação iônica e osmótica e de excreção ativa de NH4 +. Dessa forma, a caracterização cinética da (Na+,K+)-ATPase branquial de Clibanarius vittatus pode fornecer dados importantes para a compreensão dos mecanismos bioquímicos desses processos. Nesse sentido, foram realizados ensaios cinéticos com a fração microsomal obtida do tecido branquial de C. vittatus. Os dados obtidos revelaram a presença de um único pico com atividade ATPase. Os dados obtidos a partir da hidrólise do substrato ATP revelaram a presença de dois sítios, um de alta afinidade que apresenta interação sítio-sítio (nH=1,9; K0,5= 63,8 ± 2,9 nM e V= 19,1 ± 0,8 U/mg) e outro de baixa afinidade, com características Michaelianas (nH=1,0; KM= 44,1 ± 2,6 mM e VM= 123,5 ± 6,1 U/mg). Além disso, foi observada interação do tipo sítio-sítio (nH= 1,8) para estimulação dos íons magnésio (V= 132,0 ± 5,3 U/mg e K0,5= 0,36 ± 0,02 mM). Por outro lado, as interações dos íons sódio (K0,5= 7,4 ± 0,4 mM), potássio (K0,5= 1,51 ± 0,05 mM) e amônio (K0,5= 4,5 ± 0,2 mM) obedeceram a uma cinética Michaeliana. Os dados obtidos mostraram que em condições saturantes de íons potássio...

Imobilização da lipase de Burkholderia cepacia em nanopartículas magnéticas e sua applicação em resolução cinética de alcoóis secundários quirais; Immobilization of Burkholderia cepacia lipase on magnetic nanoparticles and its application in enzymatic kinetic resolution of chiral secondary alcohols

Rebelo, Lya Pantoja
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 11/05/2009 PT
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Esta dissertação apresenta um estudo de diferentes metodologias de imobilização (fisissorção, quimissorção com carboxibenzaldeído e quimissorção com glutaraldeído) da lipase de Burkholderia cepacia em nanopartículas magnéticas e sua aplicação na resolução cinética de alcoóis secundários racêmicos. O método de imobilização por fisissorção resultou na imobilização de 0,21 mg de proteína em 20 mg de nanopartículas magnéticas. Para a mesma quantidade de nanopartículas magnéticas, o método de quimissorção com carboxibenzaldeído imobilizou 0,26 mg de proteína contra 0,28 mg de proteína pelo método de quimissorção com glutaraldeído, a melhor relação encontrada neste trabalho. A atividade enzimática foi avaliada na resolução cinética de alcoóis secundários racêmicos [(RS)-2-bromo-1-(fenil)etanol, (RS)-2-bromo-1-(4-nitrofenil)etanol, (RS)-1-(4-nitrofenil)etanol e (RS)-1-(fenil)-1,2-etanodiol] via reação de transesterificação enantiosseletiva. O efeito de diferentes parâmetros reacionais para a resolução cinética foi estudado, como agente acilante, quantidade de substrato, solvente, quantidade de nanopartículas magnéticas (suporte), velocidade de agitação, tempo e temperatura reacionais. Os melhores parâmetros encontrados foram acetato de vinila como agente acilante...

Estudo de resolução cinética de álcoois secundários utilizando reação de oxidação enantiosseletiva mediada por bactérias; Study of kinetic resolution of secondary alcohols by enantioselective oxidation mediated by bacteria

Silva, Camila Rodrigues da
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 03/02/2010 PT
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36.37%
Nesta dissertação de mestrado foram estudadas duas bactérias, Sphingobacterium sp e Arthrobacter atrocyaneus, produtoras de enzimas álcool desidrogenases que se mostraram capazes de catalisar reações de oxidação enantiosseletiva de alcoóis secundários racêmicos. Inicialmente foram avaliados alguns parâmetros para a realização da resolução cinética do (RS)-1-feniletanol, assim como quantidade de substrato, biomassa das bactérias (Sphingobacterium sp e Arthrobacter atrocyaneus) e tempo reacional necessário para a oxidação completa de um dos enantiômeros do substrato. Nas reações com a bactéria Sphingobacterium sp (R1AC23) observou-se a presença de álcool desidrogenase com alta atividade catalítica, porém com moderada enantiosseletividade, pois em alguns casos observou-se a oxidação completa dos alcoóis para-substituídos derivados do (RS)-1- feniletanol a suas correspondentes cetonas. Com o estudo das reações do (RS)-1-feniletanol e a bactéria Arthrobacter atrocyaneus (R1AF57) determinou-se os principais parâmetros reacionais para alcançar uma excelente resolução cinética. Sendo assim, aplicou-se essa metodologia para diferentes alcoóis secundários em dois meios reacionais diferentes: com células em crescimento e com células ressuspensas em tampão fosfato. A atividade catalítica foi mais eficiente com as células em crescimento com conversões próximas de 50% e excesso enantiomérico >99% na maioria dos casos...

Doseamento microbiológico de vancomicina - desenvolvimento e validação de método empregando leitura cinética em microplacas; Microbiological assay of vancomycin - development and validation method using kinetic reading microplate

Botelho, Túlia de Souza
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 28/01/2011 PT
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O ensaio turbidimétrico tem como princípio a redução da densidade óptica em suspensões microbianas, decorrente o incremento na concentração do antibiótico. No ensaio convencional trabalha-se com tubos de ensaio que demandam longo tempo para visualização da resposta. Assim, o método empregando microplacas com leitura cinética para a dosagem de antibióticos é de interesse considerável, uma vez que possibilita reduzir quantidade de material e tempo de análise necessários e permite o ensaio de grande número de amostras simultaneamente, com leitura e cálculo automatizado. O objetivo deste trabalho é desenvolver o método de doseamento microbiológico de vancomicina empregando microplacas e modo de leitura cinético, assim como validar o método desenvolvido, através da avaliação dos parâmetros de especificidade e seletividade, linearidade, faixa ou intervalo linear, exatidão e precisão. Adicionalmente foi contemplado desenvolvimento paralelo entre o método convencional e o cinético, de forma a permitir respaldo positivo quanto à validação. Sendo assim, através do estudo dos parâmetros de validação do método cinético, trabalhou-se em condições estabelecidas abrangendo curva-padrão de vancomicina com concentrações entre 0...

Implicações da prática de exercícios em cadeia cinética aberta e fechada na reabilitação do joelho; Effects of open and closed kinetic chain exercises

Lima, Claudia Silveira
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
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Exercícios em cadeia cinética aberta e cadeia cinética fechada tem sido propostos para a reabilitação no pós operatório de reconstrução do ligamento cruzado anterior. Não há consenso na literatura de qual o tipo de exercício é mais apropriado e ao mesmo tempo seguro, não pondo em risco o procedimento cirúrgico. O propósito deste estudo foi verificar os efeitos de programas de exercícios em cadeia cinética aberta e fechada em relação ao deslocamento tibial anterior, perimetria da coxa e torque muscular dos extensores e flexores do joelho de indivíduos em pós operatório de reconstrução do ligamento cruzado anterior e de indivíduos normais. Vinte e seis sujeitos (idade: 18-50 anos; sexo: masculino e feminino) foram divididos em quatro grupos. Dez indivíduos submetidos à cirurgia de reconstrução do ligamento cruzado anterior foram divididos em dois grupos (n=5): um para programa de reabilitação em cadeia cinética aberta e o outro em cadeia cinética fechada. Os outros dezesseis indivíduos sem lesão de ligamento cruzado anterior foram divididos (n=8) da mesma forma que os grupos anteriores. Para a análise do deslocamento tibial anterior foi realizado o teste de Lachman, através do Stryker Knee Laxity Tester. A medida da perimetria da coxa foi realizada a 5cm...

Kinetic model of poly(3-hydroxybutyrate) thermal degradation from experimental non-isothermal data

Santos, A. F.; Polese, L.; Crespi, M. S.; Ribeiro, C. A.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 287-291
ENG
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The non-isothermal data given by TG curves for poly(3-hydroxybutyrate) (PHB) were studied in order to obtain a consistent kinetic model that better represents the PHB thermal decomposition. Thus, data obtained from the dynamic TG curves were suitably managed in order to obtain the Arrhenius kinetic parameter E according to the isoconversional F-W-O method. Once the E parameters is found, a suitable logA and kinetic model (f(alpha)) could be calculated. Hence, the kinetic triplet (E +/- SD, logA +/- SD and f(alpha)) obtained for the thermal decomposition of PHB under non-isothermal conditions was E=152 +/- 4 kJ mol(-1), logA=14.1 +/- 0.2 s(-1) for the kinetic model, and the autocatalytic model function was: f(alpha)=alpha(m)(1-alpha)(n)=alpha(0.42)(1-alpha)(0.56).

Tin(II)-EDTA complex: kinetic of thermal decomposition by non-isothermal procedures

Guinesi, L. S.; Ribeiro, C. A.; Crespi, M. S.; Veronezi, A. M.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 35-42
ENG
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Tin on the oxide form, alone or doped with others metals, has been extensively used as gas sensor, thus, this work reports on the preparation and kinetic parameters regarding the thermal decomposition of Sn(II)-ethylenediaminetetraacetate as precursor to SnO2. Thus, the acquaintance with the kinetic model regarding the thermal decomposition of the tin complex may leave the door open to foresee, whether it is possible to get thin film of SnO2 using Sn(II)-EDTA as precursor besides the influence of dopants added.The Sn(II)-EDTA soluble complex was prepared in aqueous medium by adding of tin(II) chloride acid solution to equimolar amount of ammonium salt from EDTA under N-2 atmosphere and temperature of 50degreesC arising the pH similar to 4. The compound was crystallized in ethanol at low-temperature and filtered to eliminate the chloride ions, obtaining the heptacoordinated chelate with the composition H2SnH2O(CH2N(CH2COO)(2))(2).0.5H(2)O.Results from TG, DTG and DSC curves under inert and oxidizing atmospheres indicate the presence of water coordinated to the metal and that the ethylenediamine fraction is thermally more stable than carboxylate groups. The final residue from thermal decomposition was the SnO2 characterized by X-ray as a tetragonal rutile phase.Applying the isoconversional Wall-Flynn-Ozawa method on the DSC curves...

Kinetic parameters for thermal decomposition of hydrazine

Santos, L. B.; Ribeiro, C. A.; Capela, J. M V; Crespi, M. S.; Pimentel, M. A S; De Julio, M.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 1209-1216
ENG
Relevância na Pesquisa
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The propulsion of most of the operating satellites comprises monopropellant (hydrazine - N2H4) or bipropellant (monometilydrazine - MMH and nitrogen tetroxide) chemical systems. When some sample of the propellant tested fails, the entire sample lot shall be rejected, and this action has turned into a health problem due to the high toxicity of N2H 4. Thus, it is interesting to know hydrazine thermal behavior in several storage conditions. The kinetic parameters for thermal decomposition of hydrazine in oxygen and nitrogen atmospheres were determined by Capela-Ribeiro nonlinear isoconversional method. From TG data at heating rates of 5, 10, and 20 C min-1, kinetic parameters could be determined in nitrogen (E = 47.3 ± 3.1 kJ mol-1, lnA = 14.2 ± 0.9 and T b = 69 C) and oxygen (E = 64.9 ± 8.6 kJ mol-1, lnA = 20.7 ± 3.1 and T b = 75 C) atmospheres. It was not possible to identify a specific kinetic model for hydrazine thermal decomposition due to high heterogeneity in reaction; however, experimental f(α)g(α) master-plot curves were closed to F 1/3 model. © 2013 Akadémiai Kiadó, Budapest, Hungary.

Kinetic parameters of soil β-glucosidase response to environmental temperature and moisture regimes

Zhang,Yulan; Chen,Lijun; Wu,Zhijie; Sun,Caixia
Fonte: Sociedade Brasileira de Ciência do Solo Publicador: Sociedade Brasileira de Ciência do Solo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2011 EN
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Soil β-glucosidase participates in the final step of cellulose biodegradation. It is significant in the soil C cycle and is used as an indicator of the biological fertility of soil. However, the response of its kinetic parameters to environmental temperature and moisture regimes is not well understood. This study tested the β-glucosidase response in the main agricultural soils (black soil, albic soil, brown soil, and cinnamon soil) of Northeast China. Incubation tests were conducted to measure the kinetic parameters Km, Vmax or Vmax/Km of soil β-glucosidase at environmental temperatures of 10, 20 and 30 ºC and at 10, 20 and 30 % soil moisture content. The insensitive response of the kinetic parameters to temperature changes indicates that soil β-glucosidase was present primarily in immobilized form. The significant response of the kinetic parameters of soil β-glucosidase to soil moisture rather than to environmental temperatures suggests that the catalytic ability of soil β-glucosidase was sensitive to changing soil moisture regimes.

Development of sequential injection methodologies for the spectrophotometric direct and kinetic determination of aluminium in natural and waste waters

Mesquita,Raquel B. R.; Rangel,António O. S. S.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
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Two sequential injection methodologies for the spectrophotometric determination of reactive aluminium in water samples are proposed, based on the reaction between chrome azurol S (CAS) and aluminium. The two methods involve a direct and a kinetic methodology (for its application to coloured waste waters), both accommodated within the same manifold. The working ranges obtained were: 0.040-0.500 mg Al L-1 for direct method and 0.050-0.300 mg Al L-1 for the kinetic method. The described system has high degree of automation, enabling sampling throughputs of 31 and 57 h-1 for the kinetic method and direct methods, respectively. The reagents consumption per determination is low: 46 µg of CAS, 3.75 mg of sodium acetate and 25 µg of ascorbic acid. The volume of effluent produced per determination is only around 2.8 mL in the direct method and 3.4 mL in the kinetic method.

An investigative study of kinetic resolutions by the Sharpless asymmetric dihydroxylation reaction

Hamon, David P. G.; Tuck, Kellie Louise; Christie, Hamish Saul
Fonte: Pergamon-Elsevier Science Limited Publicador: Pergamon-Elsevier Science Limited
Tipo: Artigo de Revista Científica
Publicado em //2001 EN
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The requirements for a highly selective kinetic resolution with the Sharpless asymmetric dihydroxylation (AD) reaction were investigated with a number of alkene substrates. It was found that with 1-phenyl-4-tert-butylcyclohexene enantioselectivity is very high, yet diastereoselectivity is poor and kinetic resolution is ineffective. With 5-methyl-2-phenylbicyclo[3.2.0]heptan-2-ene both diastereoselectivity and enantioselectivity are high and kinetic resolution is effective. It was discovered that the transition state for the product-determining step in the Sharpless AD reaction is not product-like, and effective kinetic resolution can occur when one face of a chiral alkene is hindered. It was discovered that the transition state for the product-determining step in the Sharpless asymmetric dihydroxylation reaction is not product-like, and effective kinetic resolution can occur when one face of a chiral alkene is hindered.; David P.G Hamon, Kellie L Tuck and Hamish S Christie; Available online 5 November 2001.

A new adaptation of the method of invariant kinetic parameters and its application to a flame retardant system.

Philcox, Anne Patricia
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014
Relevância na Pesquisa
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This thesis treats a particular flame retardant (FR) system with a new kinetic analysis method derived from the method of Invariant Kinetic Parameters (IKP). The IKP method is one of many techniques available that extract a kinetic triplet (activation energy, pre-exponential factor and function of conversion) from non-isothermal, constant heating rate thermogravimetric (TG) data. The principles and advantages of the IKP method are discussed within a broad context, as are its limitations that are shared by most other methods. Such a consolidated and critical literature review is uncommon and is designed to help the novice researcher navigate through the kinetic analysis “minefield”. Each and every step for all solid-state mechanism derivations are explained for the same purpose: To encourage the adoption of an informed and circumspect approach to often complex heterogenous kinetic analysis. The new method improves kinetic analysis outcomes and reliability by, in part, refining the IKP. Its approach is described in such detail that the inherent complexity of this undertaking can be fully appreciated, and if possible, managed in better ways. Subroutines written in Visual Basic for Applications in Excel to realise the method are validated with synthetic data up to a complexity of two overlapped independent models. Output from the method that pertains to water evaporation and the decomposition of calcium carbonate compares favourably with expectation. Statistical analyses are integrated into the method and allow for the proper treatment of uncertainty in all applications. Motivation for this study originated from a desire to characterise the commercial FR system...

Untersucher-unabhängige Bestimmung der lokalen stato-kinetischen Dissoziation (SKD) mittels semi-automatisierter Perimetrie; Examiner independent evaluation of local stato-kinetic dissociation (SKD) with semi-automated perimetry

Schiller, Jan
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Als stato-kinetische Dissoziation (SKD) oder auch RIDDOCH-Phänomen bezeichnet man die Differenz zwischen einem statisch und einem kinetisch erhobenen Gesichtsfeldbefund. Über die Entstehungsursachen dieses Phänomens ist bisher wenig bekannt, sinnes-physiologische und anatomische Forschungen lassen vermuten, dass es mit dem magno- und parvozellulären System der Sehbahn zusammenhängt. In dieser Studie wurden 15 Patienten mit fortgeschrittenen, stabilen Gesichts-feldausfällen unterschiedlicher Genese (Glaukom, Retinitis pigmentosa und Schädigung der hinteren Sehbahn) untersucht. Zunächst wurde manuell-kinetisch und -statisch der ungefähre Verlauf der Skotomgrenze (Stimulus-Größe 26’, Stimulus-Leuchtdichte 110 cd/m2, Hintergrund-Leuchtdichte 10 cd/m2) ermittelt. Hierauf basierend wurde eine individuelle Vektoranordnungen für die automatisiert-kinetische und eine für die automatisiert-statische Untersu-chung erstellt. Jede Vektoranordnung bestand aus 16-24 Vektoren (Länge der Vektoren jeweils 6°), welche 2-3° innerhalb des Gesichtsfeldausfalls startete und die Skotomgrenze möglichst senkrecht schnitt. In der automatisiert-kinetischen Untersuchung wurden zusätzlich 4 bis 8 kinetische Vektoren inner-halb des sicher sehenden Gesichtsfeldbereichs zur Messung der individuellen Reaktionszeit des Patienten platziert. Alle kinetischen Vektoren wurden mit einer Geschwindigkeit von 2 °/s präsentiert und sowohl die kinetischen als auch die statischen Vektoren wurden sechs Mal in randomisierter Reihenfolge dargeboten. Die statische Vektoranordnung bestand aus der gleichen Anzahl an Vektoren wie die kinetische Vektoranordnung und hatte annähernd die gleichen Lokalisationen. An den Stellen...

Kinetic study of the co-firing of bagasse-sludge blends

Torquato, Lilian M.; Braz, Carlos E. M.; Ribeiro, Clovis A.; Capela, Jorge M. V.; Crespi, Marisa S.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 499-507
ENG
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Thermogravimetry was used for the thermal and kinetic characterization of waste biomass as bagasse and sewage sludge and their blends, during the co-firing process for power generation. The kinetic evaluation was performed by a linear integral isoconversional method, applying different conditions of heating. In higher heating rates, kinetic process of combustion of all tested biomasses showed the lower values and the lower changes in activation energy up to 70 % for the conversion of all samples. Above this point, there was a continuous increase in this parameter for bagasse and the bagasse-sludge blends up to the end of the processes. However, in the case of sludge, there was a continuous decrease in energy, which suggests the occurrence of catalytic reactions. The results showed that under low heating rates, the sludge-bagasse blends exhibit profiles of kinetic decomposition very similar to bagasse, regardless the proportion of sludge employed, which may be due the contribution of the high amount of volatile organic materials present in bagasse (30 % higher than the sludge), which increase the reactivity of the sample during the devolatilization process. On the other hand...

Some fundamental questions concerning the kinetic theory of electrons in molecular gases and the e-H 2 vibrational cross section controversy

Robson, Robert; White, Ronald Douglas; Morrison, Michael A
Fonte: Institute of Physics Publishing Publicador: Institute of Physics Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We commence a fundamental re-examination of the kinetic theory of charged particle swarms in molecular gases, focusing on collisional excitation of molecular rotational and ro-vibrational states by electrons. Modern day analysis of electron swarms has been based upon the kinetic equation of Wang-Chang et al, which simply treats all processes as scalar energy excitations, and ignores angular momentum conservation and the vector dynamics associated with rotational excitation. It is pointed out that there is no alternative, more exact kinetic equation readily available for electrons which enables one to directly ascertain the degree of error introduced by this approximation. Thus in this preliminary study, we approach the problem indirectly, from the standpoint of the neutral molecules, using the Waldmann-Snider quantum kinetic equation, and insist that an electron-molecule collision must look the same from the perspective of both electron and molecule. We give a formula for quantitatively assessing the importance of scalar versus vectorial treatments of rotational excitation by looking at the post-collisional 'echo' produced by an electron swarm as it passes through the gas. It is then pointed out that in order to remedy any deficiency...

A study on certain aspects of kinetic energy associated with western disturbances over northwest India

RAJU,P. V. S.; BHATLA,R.; MOHANTY,U. C.
Fonte: Centro de Ciencias de la Atmósfera, UNAM Publicador: Centro de Ciencias de la Atmósfera, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2011 EN
Relevância na Pesquisa
36.41%
The winter precipitation in western Himalayas, particularly over Jammu and Kashmir, Himachal Pradesh, Uttaranchal and neighborhood is important from the point of view of agriculture, horticulture, transport, logistics and glacier basins that feed the rivers of north India. The precipitation is due to the large-scale interaction between the mid latitude and the tropical air masses. The interaction process leads to the formation or intensification of synoptic systems known as western disturbances that move from west to east. In this paper, kinetic energy budget terms for an intense western disturbance that occurred over northwest India have been analyzed. An intense western disturbance, that gave widespread precipitation over the northwestern parts of the country, moved across the region from 19 to 21 January 1997. The data required for the study was extracted from National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis datasets. The results indicate that the strong flux convergence and adiabatic production of kinetic energy takes place during the passage of western disturbance over north India. It is found that the meridional component of kinetic energy contributes for the generation...

Modelling of a fixed bed adsorber based on an isotherm model or an apparent kinetic model

Che-Galicia,G.; Martínez-Vera,C.; Ruiz-Martínez,R.S.; Castillo-Araiza,C.O.
Fonte: UAM, Unidad Iztapalapa, División de Ciencias Básicas e Ingeniería Publicador: UAM, Unidad Iztapalapa, División de Ciencias Básicas e Ingeniería
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
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Isotherm model and apparent kinetic model are simple approaches, which are indistinctly used to predict the kinetic behaviour of the adsorption phenomena. The main objective in this work was to elucidate when these approaches should be coupled to a pseudo-heterogeneous fixed-bed adsorber model to describe reliable breakthrough curves when experimental data at industrial scale are not available. To achieve this, an adsorption column packed with a low-cost natural zeolite was modelled for the removal of Rhodamine B (RhB). To have certainty in the model predictions, equilibrium and kinetic experiments were carried out. Freundlich isotherm model and a pseudo second order apparent kinetic model accounting for diffusion phenomena led to the most adequate fit to experimental data. Experimental and simulations results indicated that the use of an isotherm model (LDF-M) or an apparent kinetic model (AkA-M) in the packed bed adsorbed model predicted similar tendencies regarding the effect on the breakthrough point of the different parameters considered. Nevertheless, the shapes of the breakthrough curves predicted by both models were significantly different, suggesting that an apparent kinetic model is necessary to have reliable prediction of the industrial behaviour of this studied zeolite since intraparticle mass transport resistances are significant.

Neutron emission effects on final fragments mass and kinetic energy distribution from low energy fission of234U

Montoya,M; Rojas,J; Lobato,I
Fonte: Sociedad Mexicana de Física Publicador: Sociedad Mexicana de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2008 EN
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The standard deviation of the final kinetic energy distribution (σe) as a function of mass of final fragments (m) from low energy fission of 234U, measured with the Lohengrin spectrometer by Belhafaf et al., presents a peak around m = 109 and another around m = 122. The authors attribute the first peak to the evaporation of a large number of neutrons around the corresponding mass number, i.e. there is no peak on the standard deviation of the primary kinetic energy distribution (σE) as a function of primary fragment mass (A). The second peak is attributed to a real peak on σE (A). However, theoretical calculations related to primary distributions made by H.R. Faust and Z. Bao do not suggest any peak on σE (A). In order to clarify this apparent controversy, we have made a numerical experiment in which the masses and the kinetic energy of final fragments are calculated, assuming an initial distribution of the kinetic energy without structures on the standard deviation as function of fragment mass. As a result we obtain a pronounced peak on σe (m) curve around m = 109, a depletion from m = 121 to m = 129, and an small peak around m = 122, which is not as great as that measured by Belhafaf et al. Our simulation also reproduces the experimental results on the yield of the final mass Y (m)...