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Geometric Dimensions (geometric + dimension)

Distribution by Scientific Domains

Chemistry	60%

Selected Abstracts

A counterfort versus a cantilever retaining wall,a seismic equivalence,

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2005
Ashok K. Chugh
Abstract A procedure is presented to develop geometric dimensions and material property values for a model cantilever wall from those of a prototype counterfort wall such that the model wall will simulate the response of the prototype wall for seismic loads. The equivalency criteria are given. A sample problem is included to illustrate the use of the proposed procedure. Accuracy of results is discussed. Published in 2005 by John Wiley & Sons, Ltd. [source]

Adaptive geometry and process optimization for injection molding using the kriging surrogate model trained by numerical simulation

ADVANCES IN POLYMER TECHNOLOGY, Issue 1 2008
Yuehua Gao
Abstract An adaptive optimization method based on the kriging surrogate model has been developed to intelligently determine the optimal geometric dimensions and processing parameters for minimizing warpage in injection-molded components. The kriging surrogate model is a statistics-based interpolated technique that provides the approximate functional relationship between warpage and factors that influence warpage. In this study, it is used to be first trained by,and later replaced,the full-fledged, time-consuming numerical simulation in the optimization process. Based on this surrogate model, an adaptive iteration scheme that takes into account the predicted uncertainty is performed to improve the accuracy of the surrogate model while finding the optimum solution. The optimization process starts with a small number of initial training sample points and then adds additional key points during iterations by evaluating the correlations among the candidate points. As an example of validation and application, optimization of geometric dimensions and processing parameters for a box-shape part with different and stepwise wall thicknesses has been performed. The results demonstrate the feasibility and effectiveness of the proposed optimization method. © 2008 Wiley Periodicals, Inc. Adv Polym Techn 27:1,16, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20116 [source]

Predicting deflagration to detonation transition in hydrogen explosions

PROCESS SAFETY PROGRESS, Issue 3 2008
Prankul Middha
Abstract Because of the development in computational resources, Computational Fluid Dynamics (CFD) has assumed increasing importance in recent years as a tool for predicting the consequences of accidents in petrochemical and process industries. CFD has also been used more and more for explosion predictions for input to risk assessments and design load specifications. The CFD software FLACS has been developed and experimentally validated continuously for more than 25 years. As a result, it is established as a tool for simulating hydrocarbon gas deflagrations with reasonable precision and is widely used in petrochemical industry and elsewhere. In recent years the focus on predicting hydrogen explosions has increased, and with the latest release the validation status for hydrogen deflagrations is considered good. However, in many of these scenarios, especially involving reactive gases such as hydrogen, deflagration to detonation transition (DDT) may be a significant threat. In previous work, FLACS was extended to identify whether DDT is likely in a given scenario and indicate the regions where it might occur. The likelihood of DDT has been expressed in terms of spatial pressure gradients across the flame front. This parameter is able to visualize when the flame front captures the pressure front, which is the case in situations when fast deflagrations transition to detonation. Reasonable agreement was obtained with experimental observations in terms of explosion pressures, transition times, and flame speeds. The DDT model has now been extended to develop a more meaningful criterion for estimating the likelihood of DDT by comparison of the geometric dimensions with the detonation cell size. This article discusses the new models to predict DDT, and compare predictions with relevant experiments. © 2007 American Institute of Chemical Engineers Process Saf Prog 2008 [source]

Design of a Small Centrifugal Blood Pump With Magnetic Bearings

ARTIFICIAL ORGANS, Issue 9 2009
Said Jahanmir
Abstract Design of a blood pump with a magnetically levitated rotor requires rigorous evaluation of the magnetic bearing and motor requirements and analysis of rotor dynamics and hydraulic performance with attention to hemolysis and thrombosis potential. Given the desired geometric dimensions, the required operating speed, flow in both the main and wash flow regions, and magnetic bearing performance, one of several design approaches was selected for a new prototype. Based on the estimated operating speed and clearance between the rotor and stator, the motor characteristics and dimensions were estimated. The motor stiffness values were calculated and used along with the hydraulic loading due to the fluid motion to determine the best design for the axial and radial magnetic bearings. Radial and axial stability of the left ventricular assist device prototype was verified using finite element rotor dynamic analysis. The analysis indicated that the rotor could be completely levitated and spun to the desired operating speed with low power loss and no mechanical contact. In vitro experiments with a mock loop test setup were performed to evaluate the performance of the new blood pump prototype. [source]