INTERNATIONAL JOURNAL OF ENGINEERING
Year:2011 | Volume:24 | Issue:2 (TRANSACTIONS A: BASICS)|Papers Count:9

A prismatic beam made of a behaviorally nonlinear material is analyzed under a harmonic load moving with a known velocity. The vibration equation of motion is derived using Hamilton principle and Euler-Lagrange Equation. The amplitude of vibration, circular frequency, bending moment, stress and deflection of the beam can be calculated by the presented solution. Considering the response of the beam, in the sense of its resonance, it is found that there is no critical velocity when the behavior of the beam material is assumed to be physically nonlinear.

This paper considers the single machine scheduling problem with precedence constraints and deteriorating jobs and a mathematical model based on binary integer programming (BIP) is developed. Since the precedence constraints exist, a job cannot start before completion of its all predecessors. The proposed model consists of two steps: in the first step, the earliest starting time of each job is computed, then the results are used in the second step in which an optimal sequence between jobs is determined with the aim of minimizing the total completion time. Finally, a numerical example is presented and solved using optimization software LINGO 8.0.

In this work, mechanical alloying was employed to produce Ti-50Al and Ti-45Al-5Cr (at %) alloys. Alloying was performed in a planetary mill and the alloying time varying from 5 to 70 h. Characterization of the powder mixture was performed by X-ray diffraction (XRD) technique, Scanning Electron Microscopy (SEM) and Differential Thermal Analysis (DTA), during mechanical alloying and after annealing treatment at 1100oC in vacuum furnace. The results showed, only a complete amorphous phase was detected after 50h of milling of Ti-50Al powder blends but with 5 at % addition of Cr, the Cr (Ti, Al) solid solution phase within the amorphous matrix were formed. While annealing of the mechanically alloyed Ti-50Al powders at 1100oC for 10min leads to the nanocrystalline phase of TiAl (g), nanocrystalline phases of mainly Ti Al (g) together with Ti3Al (a2) were formed in Cr containing powders. Cr accelerated the production of duplex structure (g+a2) and It seemed that the Cr (Ti, Al) solid solution was dissolved in TiAl (g) and Ti3Al (a2).

Laminar two dimensional forced convective heat transfer of Al2O3-water nanofluid in a horizontal microchannel has been studied numerically, considering axial conduction, viscous dissipation and variable properties effects. The existing criteria in the literature for considering viscous dissipation in energy equation are compared for different cases and the most proper one is applied for the rest of the paper. The results showed that nanoparticles enhance heat transfer characteristics of the channel and on contrast, viscous dissipation causes the Nusselt number and friction factor to decrease. The viscous dissipation effect may be emphasized by increasing Reynolds number and decreased by raising the exerted heat flux. Also, it was found that there is a critical Reynolds number below which the average Nusselt number of the nanofluid changes unusually with Reynolds number as a result of variable properties effect.

A truly Meshless Local Petrov-Galerkin (MLPG) method is developed for solving 3D elasto-static problems. Using the general MLPG concept, this method is derived through the local weak forms of the equilibrium equations, by using a test function, namely, the Heaviside step function. The Moving Least Squares (MLS) are chosen to construct the shape functions. The penalty approach is used to impose essential boundary conditions. The complete study of the effects of radius of support domain on the accuracy and efficiency of the solution is performed. The values of this parameter leave a great effect on runtime and accuracy. The Genetic Algorithm (GA) is used to determine the optimum values of this MLPG parameter to minimize the runtime and maximize the accuracy. Several numerical examples are included to demonstrate that the present method is very promising for solving the elasto-elastic problems.

This paper presents a modeling study of a CNG Homogenous Charge Compression Ignition (HCCI) engine using a single-zone and a multi-zone combustion model. Authors’ developed code is able to predict engine combustion and performance parameters in closed part of the engine cycle. As detailed chemical kinetics is necessary to investigate combustion process in HCCI engines, therefore, GRI-mech 3.0 mechanism was used which includes 53 chemical species and 325 reactions for natural gas combustion. Although, single-zone model is useful to parametric study on variation of some engine combustion parameters such as start of combustion (SOC), But, it could neither be able to accurately predict other engine combustion related parameters nor engine performance and emission parameters. Hence, a multi- zone combustion model was developed to predict those parameters accurately. GRI-mech 3.0 combustion mechanism was developed for natural gas combustion without considering Exhaust Gas Recirculation (EGR). To consider the effect of EGR on HCCI combustion, the mechanism's rate coefficients should be optimized. These coefficients were optimized using a developed genetic algorithm code. Predicted values show good agreement with corresponding experimental values for whole ranges of engine operating conditions.

Statistical analysis of non-normal data is usually more complicated than that for normal distribution. In this paper, a simple root/power transformation technique developed by Niaki, et al [1] is extended to transform right and left skewed distributions to nearly normal. The value of the root/power is explored such that the skewness of the transformed data becomes almost zero with an acceptable error. The proposed method is then compared to the well-known and complicated Box, et al [2] transformation method for different left and right skewed distributions using Monte Carlo simulation. While the proposed procedure is easy to understand and to implement, the results of the simulation study show that it works as good as the Box-Cox method.

In the present work a two fluid model for blood flow through abnormally constricted human artery (stenosed artery) has been developed. The model consists of a core region of suspension of all erythrocytes assumed to be micro-polar fluid so as to include the micro-structural effects in addition to the peripheral-layer viscosity effects, and a peripheral plasma layer free from cells of any kind of Newtonian fluid. This model is used to predict the effects on physiological characteristics of blood flow in normal and stenosed condition. The significance of the present model over the existing models has been pointed out by comparing the results with other theories both analytically and numerically.

In this paper, European option pricing with stochastic volatility forecasted by well known GARCH model is discussed in context of Indian financial market. The data of Reliance Ltd. stock price from 3/01/2000 to 30/03/2009 is used and resulting partial differential equation is solved by Crank-Nicolson finite difference method for various interest rates and maturity in time. The sensitivity measures “Greeks” are also determined to validate the model. It is observed that the value of European put option increases with maturity time and decreases with interest rate.