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‣ Neural network model for designing automotive devices using SMD LED

ORTEGA, A. V.; SILVA, I. N.
Fonte: KOREAN SOC AUTOMOTIVE ENGINEERS Publicador: KOREAN SOC AUTOMOTIVE ENGINEERS
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
37.927974%
The advantages offered by the electronic component LED (Light Emitting Diode) have resulted in a quick and extensive application of this device in the replacement of incandescent lights. In this combined application, however, the relationship between the design variables and the desired effect or result is very complex and renders it difficult to model using conventional techniques. This paper consists of the development of a technique using artificial neural networks that makes it possible to obtain the luminous intensity values of brake lights using SMD (Surface Mounted Device) LEDs from design data. This technique can be utilized to design any automotive device that uses groups of SMD LEDs. The results of industrial applications using SMD LED are presented to validate the proposed technique.

‣ Medição de desempenho do gerenciamento de processos de negócio - BPM no PNAFE: uma proposta de modelo; BPM performance measurement within PNAFE: a proposed model

Sobreira Netto, Francisco
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 17/05/2006 Português
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Nas últimas décadas pôde-se constatar uma preocupação constante de gestores, tanto da iniciativa privada quanto da administração pública, com a evolução do conhecimento e a busca de soluções para os problemas relacionados às áreas de gestão de organizações e de tecnologia. O conceito de gerenciamento de processos, conhecido desde o início do século passado com o movimento da administração científica, tem ecoado com mais intensidade na consciência do mundo dos negócios nas duas últimas décadas. A busca pelo direcionamento das organizações aos processos de negócio motivou como o da gestão pela qualidade total (TQM), a reengenharia dos processos de negócio (BPR), o desenvolvimento de sistemas integrados de gestão empresarial (ERP) e, mais recentemente, o gerenciamento de processos de negócio ou BPM - Business Process Management. Contudo, existe na literatura acadêmica uma lacuna de relatos sobre mecanismos de medição de desempenho de BPMs que considerem o processo como um todo, de ponta a ponta, e que contribuam para o cumprimento das metas estratégicas das organizações. A existência de um significativo atraso tanto no aspecto tecnológico quanto no controle de processos de negócio na administração pública fazendária brasileira foi um dos motivos que provocaram a criação do PNAFE - Programa Nacional de Apoio aos Fiscos Estaduais no Brasil. Documentos do programa apontam a necessidade de que o gerenciamento de processos de negócio das organizações fazendárias seja mensurado considerando atributos gerenciais...

‣ Elementos estruturais para gestão de desempenho em ambientes de produção enxuta; Framework elements for performance management in lean manufacturing environments

Esposto, Kleber Francisco
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 01/12/2008 Português
Relevância na Pesquisa
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Os impactos causados na manufatura das empresas que buscam a implementação das técnicas e ferramentas guiadas pelos conceitos da produção enxuta não se limitam às questões técnicas. Para que se atenda ao dinamismo nas operações requerido por essa filosofia, é dado empowerment aos operadores do chão-de-fábrica para que executem ações corretivas e de melhoria por si próprios, mudando os papéis desses funcionários de simples cumpridores de ordens para tomadores de decisão. Para isso, é necessário que, além da autoridade, esses operadores tenham disponíveis as informações requeridas para fomentar adequadamente suas decisões, e que essas informações sejam atuais e alinhadas às diretrizes definidas para a empresa. Este trabalho propõe um modelo de sistema de medição de desempenho e elementos estruturais que têm por objetivo eliminar a lacuna identificada entre outras propostas de sistemas desse tipo e as necessidades identificadas em ambientes de produção enxuta reais. O modelo é baseado no levantamento bibliográfico da literatura técnica sobre o tema e na realização de estudos de casos de duas empresas reconhecidamente bem-sucedidas na implantação da produção enxuta em suas operações. Propõe-se uma estrutura que internaliza as melhorias desenvolvidas pela empresa em políticas que servirão de base para análises e tomada de decisões futuras...

‣ Análise das perdas de carga em escoamentos de fluídos pseudoplásticos e viscoplásticos; Pressure losses analysis for pseudoplastic and viscoplastic fluid flows

Silveira, Filipe de Santis
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Trabalho de Conclusão de Curso Formato: application/pdf
Português
Relevância na Pesquisa
27.38135%
Este trabalho compreendeu simulações numéricas de escoamentos de fluidos pseudoplásticos e viscoplásticos através de um duto reto bem como de uma expansão abrupta, ambos axissimétricos, com o objetivo de analisar as perdas de carga, tanto distribuída, no primeiro caso, quanto localizada, por ocasião da expansão, no segundo caso. As simulações foram desenvolvidas por meio da metodologia de Elementos Finitos de Galerkin Mínimos-Quadrados (GLS), com base na modelagem que contou com as equações da continuidade e balanço de quantidade de movimento, acopladas ao modelo constitutivo, para fluidos com propriedades pseudoplásticas e viscoplásticas, de SMD. As perdas de carga distribuídas foram analisadas por meio do coeficiente de atrito de Darcy, f, e as localizadas em função da chamada correção de entrada, C. Ambas apresentaram redução juntamente com a diminuição do expoente de power-law n, de 1 (fluido Newtoniano) até 0,2, caso de maior pseudoplasticidade. No caso de escoamentos viscoplásticos, tanto f quanto C apresentaram aumento com o incremento no número de Bingham, Bn, o qual representa o nível de viscoplasticidade no fluido, ou seja, a quantidade de regiões que não apresentarão escoamento, comportando-se como corpos rígidos. No caso da expansão abrupta...

‣ Sistema imune e FMNL1 em síndrome mielodisplásica; Immune system and FMNL1 in myelodysplastic syndrome

Matheus Rodrigues Lopes
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/10/2012 Português
Relevância na Pesquisa
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As síndromes mielodisplásicas (SMD) são um grupo heterogêneo de doenças caracterizadas por hematopoese ineficaz e risco de progressão para leucemia mieloide aguda (LMA). SMD de baixo de risco é caracterizada por um aumento de apoptose na medula óssea e alterações clínicas com perfil autoimune, enquanto que na SMD de alto risco há uma evasão imune, baixa apoptose e danos secundários ao DNA, contribuindo para a progressão para LMA. Essas evidências, junto com os dados de terapia imunossupressora em pacientes com SMD, sugerem o papel do sistema imune na progressão desta doença. Entretanto, o papel do sistema imune não é claro, e estudos que abordem o perfil das células T são importantes para o melhor entendimento da patogênese da SMD. Formin-like 1 (FMNL1) pertence à família de proteínas formina, indispensáveis para muitos processos fundamentais actina-dependentes. FMNL1 é restritamente expressa em células derivadas de linhagem hematopoética e superexpressa em células neoplásicas hematopoéticas malignas. Recentemente, foi descrito que FMNL1 está envolvida no processo de citotoxicidade de células CD8+. Desse modo, estudar a expressão de FMNL1 tanto nos linfócitos como nas células da MO dos pacientes com SMD...

‣ The p47phox−/− Mouse Model of Chronic Granulomatous Disease Has Normal Granuloma Formation and Cytokine Responses to Mycobacterium avium and Schistosoma mansoni Eggs

Segal, Brahm H.; Doherty, T. Mark; Wynn, Thomas A.; Cheever, Allen W.; Sher, Alan; Holland, Steven M.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/1999 Português
Relevância na Pesquisa
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Chronic granulomatous disease (CGD) is a genetic disorder of NADPH oxidase in which phagocytes are defective in generating reactive oxidants. CGD patients suffer from recurrent infections and exuberant and persistent tissue granuloma formation. We hypothesized that abnormal granulomata in CGD may result from aberrant T-cell-mediated cytokine responses. To assess Th-1-type cytokine responses and granulomata, we challenged p47phox−/− and wild-type mice with avirulent (SmD) or virulent (SmT) variants of Mycobacterium avium 2-151. To assess Th-2-type cytokine responses and granulomata, we used Schistosoma mansoni eggs (SME). Mononuclear cells were harvested, and cytokine responses were determined by enzyme-linked immunosorbent assay or reverse transcriptase PCR. Following SmD or SmT challenge, splenocytes from p47phox−/− and wild-type mice generated similar polar Th-1 responses (increased levels of gamma interferon and basal levels of interleukin 4 [IL-4] and IL-5). By 8 weeks after SmT challenge, exuberant splenic granulomata developed in p47phox−/− and wild-type mice. After SME challenge, thoracic lymph node mononuclear cells from p47phox−/− and wild-type mice generated similar mixed Th-1 and Th-2 cytokine responses to SME antigen and concanavalin A. Peak lung granuloma sizes and rates of regression were similar in p47phox−/− and wild-type mice. These results suggest that exuberant granulomatous inflammation in CGD is probably not the result of skewing of T-cell responses toward the Th-1 or Th-2 pole. Appropriate regression of established tissue granulomata in p47phox−/− mice challenged with SME suggests that abnormal granuloma formation in CGD is stimulus dependent and is not an invariant feature of the disease.

‣ Renormalizing SMD: The Renormalization Approach and Its Use in Long Time Simulations and Accelerated PMF Calculations of Macromolecules

Dryga, Anatoly; Warshel, Arieh
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 07/10/2010 Português
Relevância na Pesquisa
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Simulations of long time process in condensed phases in general and in biomolecules in particular, presents a major challenge that cannot be overcome at present by brute force molecular dynamics (MD) approaches. This work takes the renormalization method, intruded by us sometime ago, and establishes its reliability and potential in extending the time scale of molecular simulations. The validation involves a truncated gramicidin system in the gas phase that is small enough to allow very long explicit simulation and sufficiently complex to present the physics of realistic ion channels. The renormalization approach is found to be reliable and arguably presents the first approach that allows one to exploit the otherwise problematic steered molecular dynamics (SMD) treatments in quantitative and meaningful studies. It is established that we can reproduce the long time behavior of large systems by using Langevin dynamics (LD) simulations of a renormalized implicit model. This is done without spending the enormous time needed to obtain such trajectories in the explicit system. The present study also provides a promising advance in accelerated evaluation of free energy barriers. This is done by adjusting the effective potential in the implicit model to reproduce the same passage time as that obtained in the explicit model...

‣ Equivalent Moving Dipole Localization of Cardiac Ectopic Activity in a Swine Model during Pacing

Lai, Dakun; Liu, Chenguang; Eggen, Michael D.; Iaizzo, Paul. A.; He, Bin
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Localization of the initial site of cardiac ectopic activity has direct clinical benefits for treating focal cardiac arrhythmias. The aim of the present study is to experimentally evaluate the performance of the equivalent moving dipole technique on non-invasively localizing the origin of the cardiac ectopic activity from body surface potential maps (BSPMs) in a well-controlled experimental setting. The cardiac ectopic activities were induced in 4 well-controlled intact pigs by either single-site pacing or dual-site pacing within the ventricles. In each pacing study, the initiation sites (ISs) of cardiac ectopic activity were localized by estimating the locations of a single moving dipole (SMD) or two moving dipoles (TMDs) from the measured BSPMs, and compared with the precise pacing sites (PSs). For the single-site pacing, the averaged SMD localization error was 18.6 ± 3.8 mm over 16 sites, while the averaged distance between the TMD locations and the two corresponding pacing sites was slightly larger (24.9 ± 6.2 mm over 5 pairs of sites), both occurring at the onset of the QRS complex (10–25 ms following the pacing spike). The obtained SMD trajectories originated near the stimulus site and then traversed across the heart during the ventricular depolarization. The present experimental results show that the initial location of the moving dipole can provide the approximate site of origin of a cardiac ectopic activity in vivo...

‣ Modelagem mecânica e investigação numérica de escoamentos de fluidos SMD empregando um método multi-campos de galerkin mínimos-quadrados

Santos, Daniel Dall'Onder dos
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
Português
Relevância na Pesquisa
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A maioria dos líquidos encontrados na natureza são não-Newtonianos e o estudo do seu comportamento tem uma importância significante em diferentes áreas da engenharia. Entre eles, uma larga classe de materiais que exibem pequena ou nenhuma deformação quando sujeitos a um nível de tensões inferiores a uma tensão limite de escoamento – chamado de comportamento viscoplástico. A presente Dissertação tem como objetivo o estudo numérico de escoamentos bidimensionais em regime permanente de fluidos viscoplásticos não-lineares em uma cavidade forçada. O modelo mecânico é definido pelas equações de conservação de massa e de balanço de momentum acopladas ao modelo viscoplástico recentemente introduzido por Souza Mendes e Dutra – SMD – e é aproximado por um método de elementos finitos multi-campos estabilizado baseado na metodologia de Galerkin mínimos-quadrados que possui como variáveis primais os campos de tensão-extra, velocidade e pressão. As condições de compatibilidade entre os subespaços de elementos finitos para tensão-extra-velocidade e velocidade-pressão são violadas, permitindo assim a utilização de interpolações de igual ordem. O método estabilizado foi implementado no código de elementos finitos para fluidos não-Newtonianos em desenvolvimento no Laboratório de Mecânica dos Fluidos Aplicada e Computacional (LAMAC) da UFRGS. Em diversos trabalhos encontrados na literatura...

‣ How Force Might Activate Talin's Vinculin Binding Sites: SMD Reveals a Structural Mechanism

Hytönen, Vesa P; Vogel, Viola
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.73189%
Upon cell adhesion, talin physically couples the cytoskeleton via integrins to the extracellular matrix, and subsequent vinculin recruitment is enhanced by locally applied tensile force. Since the vinculin binding (VB) sites are buried in the talin rod under equilibrium conditions, the structural mechanism of how vinculin binding to talin is force-activated remains unknown. Taken together with experimental data, a biphasic vinculin binding model, as derived from steered molecular dynamics, provides high resolution structural insights how tensile mechanical force applied to the talin rod fragment (residues 486–889 constituting helices H1–H12) might activate the VB sites. Fragmentation of the rod into three helix subbundles is prerequisite to the sequential exposure of VB helices to water. Finally, unfolding of a VB helix into a completely stretched polypeptide might inhibit further binding of vinculin. The first events in fracturing the H1–H12 rods of talin1 and talin2 in subbundles are similar. The proposed force-activated α-helix swapping mechanism by which vinculin binding sites in talin rods are exposed works distinctly different from that of other force-activated bonds, including catch bonds.

‣ Fast stochastic optimization for articulated structure tracking

Bray, Matthieu; Koller-Meier, Esther; Schraudolph, Nicol; Van Gool, L
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
27.38135%
Recently, an optimization approach for fast visual tracking of articulated structures based on stochastic meta-descent (SMD) [7] has been presented. SMD is a gradient descent with local step size adaptation that combines rapid convergence with excellent s

‣ Global Distribution of Fe K alpha Lines in the Galactic Center Region Observed with the Suzaku Satellite

Uchiyama, Hideki; Nobukawa, Masayoshi; Tsuru, Takeshi Go; Koyama, Katsuji; Matsumoto, Hironori
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/07/2011 Português
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We have surveyed spatial profiles of the Fe K$\alpha$ lines in the Galactic center diffuse X-rays (GCDX), including the transient region from the GCDX to the Galactic ridge X-ray emission (GRXE), with the Suzaku satellite. We resolved Fe K$\alpha$ line complex into three lines of Fe \emissiontype{I}, Fe \emissiontype{XXV} and Fe \emissiontype{XXVI} K$\alpha$, and obtained their spatial intensity profiles with the resolution of $\sim \timeform{0D.1}$. We compared the Fe \emissiontype{XXV} K$\alpha$ profile with a stellar mass distribution (SMD) model made from near infrared observations. The intensity profile of Fe \emissiontype{XXV} K$\alpha$ is nicely fitted with the SMD model in the GRXE region, while that in the GCDX region shows $3.8\pm0.3$ $(\timeform{0D.2}<|l|<\timeform{1D.5})$ or $19\pm6$ $(|l|<\timeform{0D.2})$ times excess over the best-fit SMD model in the GRXE region. Thus Fe \emissiontype{XXV} K$\alpha$ in the GCDX is hardly explained by the same origin of the GRXE. In the case of point source origin, a new population with the extremely strong Fe \emissiontype{XXV} K$\alpha$ line is required. An alternative possibility is that the majority of the GCDX is truly diffuse optically thin thermal plasma.; Comment: Accepted by PASJ

‣ Active Model Aggregation via Stochastic Mirror Descent

Ganti, Ravi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/03/2015 Português
Relevância na Pesquisa
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We consider the problem of learning convex aggregation of models, that is as good as the best convex aggregation, for the binary classification problem. Working in the stream based active learning setting, where the active learner has to make a decision on-the-fly, if it wants to query for the label of the point currently seen in the stream, we propose a stochastic-mirror descent algorithm, called SMD-AMA, with entropy regularization. We establish an excess risk bounds for the loss of the convex aggregate returned by SMD-AMA to be of the order of $O\left(\sqrt{\frac{\log(M)}{{T^{1-\mu}}}}\right)$, where $\mu\in [0,1)$ is an algorithm dependent parameter, that trades-off the number of labels queried, and excess risk.; Comment: 12 pages, 20 figures, 3 tables

‣ Chemical evolution of local galaxies in a hierarchical model

Calura, Francesco; Menci, Nicola
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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We investigate the chemical properties of local galaxies within a cosmological framework in the hierarchical picture of galaxy formation. To this aim, we use a hierarchical semi-analytic model which includes the contribution from (i) low and intermediate mass stars, (ii) type Ia Supernovae (SNe) and (iii) massive stars. - Abridged - We compare our predictions with available observations in the Milky Way (MW), in local dwarf galaxies and in local ellipticals. For Milky-Way-like galaxies, we can successfully reproduce the [O-Fe] vs [Fe/H] relation observed in disc stars and the stellar metallicity distribution (SMD). For dwarf galaxies, the stellar metallicity vs mass relation is reproduced by assuming that a substantial fraction of the heavy elements is lost through metal-enhanced outflows and a type Ia SN realization probability lower than the one of MW-like galaxies. - Abridged - In ellipticals, the observations indicate higher [alpha/Fe] values in larger galaxies. - Abridged - Our results computed with a standard Salpeter initial mass function (IMF) indicate a flat [alpha/Fe]-sigma relation. However, we suggest a possible solution to this problem and show how, by assuming a star formation-dependent IMF with a slope x=1.35 in systems with star formation rates < 100 M_sun/yr and slightly flatter (i.e. with x=1) in object with stronger star formation...

‣ Dominance of eclipsed ferrocene conformer in solutions revealed by the IR fingerprint spectral splitting

Mohammadi, Narges; Wang, Feng; Best, Stephen; Appadoo, Dominique; Chantler, Christopher T.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/06/2013 Português
Relevância na Pesquisa
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A combined high-resolution Fourier transform infrared (FTIR) spectra of ferrocene (Fc) and density functional theory (DFT) based quantum mechanical calculations confirmed the dominance of the eclipsed Fc conformer in the fingerprint region of 400-500 cm-1. The IR spectra of Fc were measured in solutions with a number of non-polar solvents such as acetonitrile, dichloromethane, tetrahydrofuran and dioxane. The measurements agree well with the earlier IR spectra of Lippincott and Nelson (1958) as well as the most recent IR spectral measurement in dichloromethane solution of Duhovic and Diaconescu (2013). All experimental measurements in the solutions unambiguously exhibit an IR spectral splitting of ca. 15 cm-1 in the 480-500 cm-1 region. The DFT based B3LYP/m6-31G(d) quantum mechanical calculations using implicit solvent models in this study indicates that only the ground electronic state of the eclipsed (D5h) Fc splits in the IR fingerprint region of ca. 500 cm-1. The IR spectral splitting characterises the centre Fe metal related vibrations of the eclipsed Fc, in agreement with our previous finding in gas phase [Mohammadi et al, 2012]. The present study further suggests that the effects of solvents on the IR spectra of Fc in this region are small and the solvent model effects are also small but the solute molecular density (SMD) model seems to produce the most accurate IR spectrum in the region of 400-600 cm-1 of Fc without scaling the calculated results.; Comment: 22 pages...

‣ Detailed characteristics of drop-laden mixing layers: Large eddy simulation predictions compared to direct numerical simulation

Okong'o, Nora; Leboissetier, Anthony; Bellan, Josette
Fonte: American Institute of Physics Publicador: American Institute of Physics
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /10/2008 Português
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Results are compared from direct numerical simulation (DNS) and large eddy simulation (LES) of a temporal mixing layer laden with evaporating drops to assess the ability of LES to reproduce detailed characteristics of DNS. The LES used computational drops, each of which represented eight physical drops, and a reduced flow field resolution using a grid spacing four times larger than that of the DNS. The LES also used models for the filtered source terms, which express the coupling of the drops with the flow, and for the unresolved subgrid-scale (SGS) fluxes of species mass, momentum, and enthalpy. The LESs were conducted using one of three different SGS-flux models: dynamic-coefficient gradient (GRD), dynamic-coefficient Smagorinsky (SMD), and constant-coefficient scale similarity (SSC). The comparison of the LES with the filtered-and-coarsened (FC) DNS considered detailed aspects of the flow that are of interest in ignition or full combustion. All LESs captured the largest-scale vortex, the global amount of vapor emanating from the drops, and the overall size distribution of the drops. All LESs tended to underpredict the global amount of irreversible entropy production (dissipation). The SMD model was found unable to capture either the global or local vorticity variation and had minimal small-scale activity in dynamic and thermodynamic variables compared to the FC-DNS. The SMD model was also deficient in predicting the spatial distribution of drops and of the dissipation. In contrast...

‣ A posteriori study using a DNS database describing fluid disintegration and binary-species mixing under supercritical pressure: heptane and nitrogen

Taskinoglu, Ezgi S.; Bellan, Josette
Fonte: Cambridge University Press Publicador: Cambridge University Press
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 25/02/2010 Português
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A large eddy simulation (LES) a posteriori study is conducted for a temporal mixing layer which initially contains different species in the lower and upper streams and in which the initial pressure is larger than the critical pressure of either species. A vorticity perturbation, initially imposed, promotes roll-up and a double pairing of four initial spanwise vortices to reach a transitional state. The LES equations consist of the differential conservation equations coupled with a real-gas equation of state, and the equations utilize transport properties depending on the thermodynamic variables. Unlike all LES models to date, the differential equations contain, additional to the subgrid-scale (SGS) fluxes, a new SGS term denoted a ‘pressure correction’ (p correction) in the momentum equation. This additional term results from filtering the Navier–Stokes equations and represents the gradient of the difference between the filtered p and p computed from the filtered flow field. A previous a priori analysis, using a direct numerical simulation (DNS) database for the same configuration, found this term to be of leading order in the momentum equation, a fact traced to the existence of regions of high density-gradient magnitude that populated the entire flow; in that study...

‣ Accuracy of computational solvation free energies for neutral and ionic compounds: Dependence on level of theory and solvent model

Sierra Rayne; Kaya Forest
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
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Gas to aqueous phase standard state (1 atm to 1 mol/L; 298.15 K) free energies of solvation ([DELTA]G^o^~solv~) were calculated for a range of neutral and ionic inorganic and organic compounds using various levels and combinations of Hartree-Fock and density functional theory (DFT) and composite methods (CBS-Q//B3, G4MP2, and G4) with the IEFPCM-UFF, CPCM, and SMD solvation models in Gaussian 09 (G09). For a subset of highly polar and generally polyfunctional neutral organic compounds previously identified as problematic for prior solvation models, we find significantly reduced [DELTA]G^o^~solv~ errors using the revised solvent models in G09. The use of composite methods for these compounds also substantially reduces their apparent [DELTA]G^o^~solv~ errors. In contrast, no general level of theory effects between the B3LYP/6-31+G** and G4 methods were observed on a suite of simpler neutral, anionic, and cationic molecules commonly used to benchmark solvation models. Further investigations on mono- and polyhalogenated short chain alkanes and alkenes and other possibly difficult functional groups also revealed significant [DELTA]G^o^~solv~ error reductions by increasing the level of theory from DFT to G4. Future solvent model benchmarking efforts should include high level composite method calculations to allow better discrimination of potential error sources between the levels of theory and the solvation models.

‣ Octanol/water distribution coefficients of the C~1~ through C~7~ perfluoro-n-alkyl sulfonates: Comparison of the IEFPCM-UFF, CPCM, and SMD solvation models

Sierra Rayne; Kaya Forest
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
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The octanol/water distribution coefficients (log D~ow~) of the C~1~ through C~7~ perfluoro-n-alkyl sulfonates (PFSAs) were calculated using the M062X/6-311++G(d,p) and MP2/6-311++G(d,p)//M062X/6-311++G(d,p) levels of theory and the IEFPCM-UFF, CPCM, and SMD solvation models. At both levels of theory with all solvation models, absolute log D~ow~ calculated for the straight chain C~1~ through C~7~ PFSAs display a substantial negative bias against available experimental data and expected trends by several log units. However, the SMD solvation model achieves accurate relative log D~ow~ accuracy, yielding fragmental contributions of a -CF~2~- group towards the log D~ow~ of 0.51+/-0.02 to 0.54+/-0.01 units (-3.0+/-0.1 to -3.1+/-0.1 kJ/mol), in good agreement with the experimental value of 0.61 units (-3.4+/-0.1 kJ/mol). In contrast, the IEFPCM-UFF and CPCM solvation models exhibit either invariant log D~ow~ with increasing perfluoro-n-alkyl chain length (CPCM) or a modestly decreasing trend (IEFPCM-UFF).

‣ Comparative study on the gas to solution phase solvation free energies of model combustion flue gas compounds (N~2~, O~2~, CO~2~, H~2~O, SO~2~, and CO) in 178 organic solvents using the IEFPCM-UFF, CPCM, and SMD implicit solvent models at the Gaussian-4 (G4) level of theory

Sierra Rayne; Kaya Forest
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Português
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Gas to solution phase Gibbs free energies of solvation at 298.15 K for transfer of six representative combustion flue gas compounds (N~2~, O~2~, CO~2~, H~2~O, SO~2~, and CO) were calculated at the Gaussian-4 (G4) level of theory using the IEFPCM-UFF, CPCM, and SMD implicit solvent models for 178 organic solvents. The IEFPCM-UFF and CPCM models yield similar free energies of solvation for all six compounds in each of the solvents considered, having maximum absolute intra-solvent deviations <1.6 kJ mol^-1^. Substantial free energy of solvation differences were observed between the IEFPCM-UFF/CPCM and SMD models, with maximum absolute intra-solvent deviations up to 45.5 kJ mol^-1^. The IEFPCM-UFF and CPCM models displayed strong free energy of solvation correlations with the solvent dielectric constant for each compound, whereas the SMD model exhibits a significantly more variable free energy of solvation relationship with the solvent dielectric constant.