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Determination of optimal laser cutting parameter settings for obtaining high cut quality in CO2 laser cutting process is of great importance. In this paper an attempt has been made to apply different optimization methods for determining of optimal values of laser power, cutting speed, assist gas pressure and focus position with the purpose of improving the cut quality characteristics obtained in the...
The aim of this study was to analyze the effect of nanostructured surfaces on the nucleate boiling of distilled water at saturation temperature and atmospheric pressure. The nanostructures studied consisted of nanoparticles of molybdenum (obtained by the sputtering method) and of maghemite, deposited on a substrate of very thin Constantan tape. The results obtained with the nanostructures were compared...
Aluminium alloy (Al 63400) is burnished using different burnishing parameters. It deals with the modelling of nonlinear characteristics of ball burnishing using Sugeno fuzzy neural system. A fuzzy neural network or neuro-fuzzy system is a learning machine that finds the parameters of the fuzzy systems (i.e. fuzzy sets, fuzzy rules) by exploiting approximation techniques from neural networks. Input...
In the present work, the 1D flow and transport equations for open channels are numerically solved and coupled to a recently developed global search optimization, the particle collision algorithm (PCA), to estimate two essential parameters present in flow and transport equations, respectively, the bed roughness and the dispersion coefficient. The PCA is inspired in the scattering and absorption phenomena...
This work describes a numerical model for calculation of carbon monoxide (CO) emissions from spark ignition engines. The model calculates CO concentration from a kinetic mechanism and from the equilibrium combustion equation. A computer program that simulates the cycle of spark ignition engines performs the CO model calculations. The model was validated against experimental data from a single-cylinder...
This work aims to establish an estimation of the blood perfusion coefficient in cancerous tissues, using inverse problem techniques. The blood perfusion coefficient is modeled as a constant parameter or as a function of the position. Several optimization methods are studied for the constant parameter model. The function estimation approach is performed by the conjugate gradient method with adjoint...
In this paper, theoretical analysis of combined effects of micropolarity and surface roughness on the performance characteristics of hydrodynamic lubrication of slider bearings with various film shapes such as plane slider bearing, exponential slider bearing, secant-shaped slider bearing and hyperbolic slider bearing is presented. A stochastic random variable with non-zero mean, variance and skewness...
This work shows the influence of intake pipe length and diameter on the performance of a spark ignition engine. A production four-stroke, four-cylinder, eight-valve, 1.0-l engine was tested in a bench dynamometer, fuelled by a blend of 78 % gasoline and 22 % ethanol. Experiments were carried out in the engine speed range from 1,500 to 6,500 rev/min. Three intake pipe lengths—0.3, 0.6 and 0.9 m—and...
This work presents a numerical model to simulate refrigerant flow through capillary tubes, commonly used as expansion devices in refrigeration systems. The flow is divided in a single-phase region, where the refrigerant is in the subcooled liquid state, and a region of two-phase flow. The capillary tube is considered straight and horizontal. The flow is taken as one-dimensional and adiabatic. Steady-state...
In this paper, a new axisymmetric shell element is devised to limit and shakedown analysis. The element is based on a Hellinger–Reissner-type variational formulation with velocity and stress fields independently interpolated. We also employ the continuum-based approach which allows the definition of the shakedown problem at the continuum level without any approximation in terms of generalized stresses...
In this paper, we address the problem of scheduling jobs in a no-wait flowshop with sequence-dependent setup times with the objective of minimizing the makespan and the total flowtime. As this problem is well known for being NP hard, we present two new constructive heuristics to obtain good approximate solutions for the problem in a short CPU time, named GAPH and QUARTS. GAPH is based on a structural...
This paper presents a computational fluid dynamics (CFD) application about the axial fan design used in an agricultural spraying system with a theoretical and experimental analysis of comparative results between the characteristic curves of a fan for several rotations and numerical results for the influence of blade attack angle variation and optimization of the spraying system, both for a same rotation...
Residual stresses (RS) can reach significant values in a welded joint, committing the quality of the parts since they affect their resistance to fatigue causing cracks and corrosion under stress. The use of strain gauges positioned in specific zones of welded parts, as a way of mapping the RS values from the welding processes, has a great technological interest. The method proposed in this paper defines...
This paper presents theoretical and experimental investigations in dynamic modeling and optimal path planning of a non-holonomic mobile robot in cluttered environments. A mobile robot in the presence of multiple obstacles was considered. Nonlinear dynamic model of the system was derived with respect to non-holonomic constraints of robot’s platform. Motion planning of the system was formulated as an...
In the present paper, the axially symmetric rarefied gas flow inside a high-speed rotating cylinder has been investigated numerically using a new algorithm, a DSMC code modified with the consistent Boltzmann algorithm (CBA), and the Direct Simulation Monte Carlo (DSMC) method. The Argon rarefied gas is supposed to be contained in a rotating cylinder which rotates with angular velocity of 15,000 Rad/s...
Shot peening is a mechanical process in which a component surface is subjected to the collision of thousands of small steel shots so inducing a compressive residual stress field that improves its fatigue resistance. Conventional numerical techniques, such as finite element method, are prohibitive to model the entire behavior of the media stream over the entire treated component because of the high...
The performance and emissions behavior of a Rover 1S/60 turboshaft engine when operated with several blends of aviation kerosene and ox tallow ethyl-ester are shown in this article. The tests were performed with a compressor shaft coupled to an hydraulic dynamometer where data of power and mass fuel flow were collected to determine the brake specific fuel consumption. A flue gas analyzer was positioned...
Code verification is mainly concerned with programming errors. Once a code is free of such errors, the verification of results can characterize the code accuracy, in particular the truncation error is of interest. Accuracy is an important feature of any code and the verification results provide some measure that can be used to compare code performance. Code verification requires an exact solution...
The effects of operational and geometrical parameters on pressure distribution and flow pattern in Y-jet atomizers were studied using an experimental apparatus working with air and water. The results show that the mixing point pressure is very dependent on the diameter ratio of the mixing duct and the air port and the water supply pressure ratio. A correlation to predict the mixing point pressure...
This work presents a numerical study of turbulent channel flows with combined convective and radiative heat transfer in participating media by means of large Eddy simulation and Reynolds averaged Navier–Stokes (RANS) with k–ε model. The main purpose is to evaluate the employment of the traditional modeling (RANS without TRI) for the prediction of time-averaged parameters of turbulent non-reactive...
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