123 research outputs found
Anopheles aquasalis Eggs from Two Venezuelan Localities Compared by Scanning Electron Microscopy
A tool for predicting the thermal performance of a diesel engine
This paper presents a thermal network model for the simulation of the transient response of diesel engines. The model was
adjusted by using experimental data from a completely instrumented engine run under steady-state and transient conditions.
Comparisons between measured and predicted material temperatures over a wide range of engine running conditions show
a mean error of 7◦C. The model was then used to predict the thermal behavior of a different engine. Model results were
checked against oil and coolant temperatures measured during engine warm-up at constant speed and load, and on a New
European Driving Cycle. Results show that the model predicts these temperatures with a maximum error of 3◦C.Torregrosa, AJ.; Olmeda González, PC.; Martín Díaz, J.; Romero Piedrahita, CA. (2011). A tool for predicting the thermal performance of a diesel engine. Heat Transfer Engineering. 32(10):891-904. doi:10.1080/01457632.2011.548639S891904321
Alterations in regional vascular geometry produced by theoretical stent implantation influence distributions of wall shear stress: analysis of a curved coronary artery using 3D computational fluid dynamics modeling
BACKGROUND: The success of stent implantation in the restoration of blood flow through areas of vascular narrowing is limited by restenosis. Several recent studies have suggested that the local geometric environment created by a deployed stent may influence regional blood flow characteristics and alter distributions of wall shear stress (WSS) after implantation, thereby rendering specific areas of the vessel wall more susceptible to neointimal hyperplasia and restenosis. Stents are most frequently implanted in curved vessels such as the coronary arteries, but most computational studies examining blood flow patterns through stented vessels conducted to date use linear, cylindrical geometric models. It appears highly probable that restenosis occurring after stent implantation in curved arteries also occurs as a consequence of changes in fluid dynamics that are established immediately after stent implantation. METHODS: In the current investigation, we tested the hypothesis that acute changes in stent-induced regional geometry influence distributions of WSS using 3D coronary artery CFD models implanted with stents that either conformed to or caused straightening of the primary curvature of the left anterior descending coronary artery. WSS obtained at several intervals during the cardiac cycle, time averaged WSS, and WSS gradients were calculated using conventional techniques. RESULTS: Implantation of a stent that causes straightening, rather than conforms to the natural curvature of the artery causes a reduction in the radius of curvature and subsequent increase in the Dean number within the stented region. This straightening leads to modest skewing of the velocity profile at the inlet and outlet of the stented region where alterations in indices of WSS are most pronounced. For example, time-averaged WSS in the proximal portion of the stent ranged from 8.91 to 11.7 dynes/cm(2 )along the pericardial luminal surface and 4.26 to 4.88 dynes/cm(2 )along the myocardial luminal surface of curved coronary arteries as compared to 8.31 dynes/cm(2 )observed throughout the stented region of a straight vessel implanted with an equivalent stent. CONCLUSION: The current results predicting large spatial and temporal variations in WSS at specific locations in curved arterial 3D CFD simulations are consistent with clinically observed sites of restenosis. If the findings of this idealized study translate to the clinical situation, the regional geometry established immediately after stent implantation may predispose portions of the stented vessel to a higher risk of neointimal hyperplasia and subsequent restenosis
Análise da estrutura e do estoque de fitomassa de uma floresta secundária da região de Manaus AM, dez anos após corte raso seguido de fogo
Caracterização e estoques de carbono de sistemas agroflorestaisno Cerrado de Minas Gerais
Regeneração natural de espécies arbóreas em diferentes comunidades de um remanescente de floresta ombrófila mista
COMPARAÇÃO FLORÍSTICO-ESTRUTURAL DOS ESTRATOS ADULTOS E REGENERANTES EM ÁREA MINERADA DE CAMPO RUPESTRE, DIAMANTINA, MG
Efeito de duas intensidades de colheita de madeira na estrutura de uma floresta natural na região de Paragominas, Pará
- …