International Journal of Engineering
Volume:27 Issue: 6, June 2014

A new approach based on a Generalized Regression Neural Network (GRNN) has been proposed to predict the planform surface pressure field on a wing-tail combination in low subsonic flow. Extensive wind tunnel results were used for training the network and verification of the values predicted by this approach. GRNN has been trained by the aforementioned experimental data and subsequently was used as a prediction tool to determine the surface pressure. Most of the previous applications of the GRNN in prediction problems were restricted to single or limited outputs, while in the present method the entire planform surface pressure was predicted at once. This highly decreases the calculation time while preserving a remarkable degree of accuracy. The wind tunnel results verify the accuracy of the data offered by the GRNN, which indicates that the present prediction and optimization tool provides sufficient accuracy with modest amount of experimental data.

The experimental investigation of material flow in non-flight rotary drums is studied in a pilot scale apparatus. Contrary to the other published references that have used granular materials, the novelty of this work is that fine particles were used in the experiments. The objective of the paper is to declare the errors of steady-state model of material flow in such devices. The operating conditions during experiments were conducted in the range of slumping, rolling and cascading regimes of material flow inside rotary drums. To keep with such conditions the rotation speed, axis inclination and feeding flow rate were considered within the range of 3.33 to 7.00 (rpm), 0.00 to 3.00 (deg.) and 6.80 to 13.60 (g/s), respectively in a drum of 14 cm diameter.The obtained experimental data reveals that the model does not describe well the material flow in feeding zone as well as in the discharge zone. However, it is reasonably well for application in the intermediate sections.

The adsorption of malachite green from aqueous solution using a local low cost adsorbent, acid activated Ntezi clay, was investigated. The low cost adsorbent was activated with different concentrations of sulphuric acid and the physicochemical properties of the adsorbent were determined. The structural properties were also analyzed using XRF and XRD. The adsorption process was studied as a function of different process parameters such as temperature, adsorbent dosage, contact time, particle size and stirring speed. These process parameters were optimized using response surface methodology (RSM). The significance of the different process parameters and their combined effect on the adsorption efficiency has been established through a full factorial central composite design. The equilibrium modeling was analyzed using Langmuir, Freundlich, Dubini-Radushkevich and Temkin isotherm equations. The experimental results follow the Langmuir adsorption isotherm. Adsorption kinetics follows the pseudo-second order equation with intra-particle diffusion as the rate determining step. This investigation has shown that local mineral clay can be modified and used as a good adsorbent for removal of impurities from contaminated water.

In this study, wavelet support vector machine (WSWM) model is proposed for daily suspended sediment (SS) prediction. The WSVM model is achieved through combination of two methods; discrete wavelet analysis and support vector machine (SVM). The developed model was compared with single SVM. Daily discharge (Q) and SS data from YadkinRiver at Yadkin College, NC station in the USA were used. In order to evaluate the model, the root mean square error (RMSE), mean absolute erro (MAE) and coefficient of determination (R2) were used.Results demonstrated that WSVM with RMSE =3294.6 ton/day, MAE=795.22 ton/day and R2 =0.838 were more desired than the other model with RMSE =6719.7 ton/day, ton/day and R2=0.327. Comparisons of these models revealed that, MAE and error standard deviation for WSVM model were about 40% and 50% less than SVM model in test period.

Accurate modeling of masonry has been a major concern of the researchers in the past decades. Besides reinforced and unreinforced masonry buildings, masonry elements can be found in frame structures as infill panels which function as partitions and/or external walls.During an earthquake these elements act as structural elements and impose a large degree of nonlinearity on the behavior of framing system. In this study, a micro-modeling procedure is proposed utilizing finite element analysis to model masonry infilled reinforced concrete moment resisting frames (RCMRFs). After calibration using material tests and standard masonry components, the model will be used to predict the behavioral parameters and failure mode of this type of structures. It will be shown that the proposed procedure is substantially successful in estimation of the stiffness and strength and can simulate the failure mode of the infilled RCMRFs tested under semi dynamic lateral loading. Finally, the process of formation and arrangement of compressive struts in different stages of lateral loading in the infill wall will be discussed. As a result, it will be concluded that the proposed modeling strategy can be used as a means to better recognize the seismic behavior of such structures. The developed strategy can also be used to propose new simplified models or precise existing ones such as equivalent diagonal strut model.

Due to extensive utilization of sensitive devices, power quality issue has become more important than before. So, accurate recognition and classification of Power Quality Distorted Signals (PQDSs) is an essential task in the power systems. In this paper two well-known timefrequency analyzers i.e. Multi Resolution Analysis (MRA) and Generalized S-Transfrm (GST) are applied simultaneously for extracting of some potential features. In order to choose the best subset features, Orthogonal Forward Selection (OFS) is used. OFS can rank features based on their severability. Probabilistic Neural Network (PNN) is considered as a powerful classifier core for discrimination of dominant selected features. Extensive samples of PQDSs are simulated to evaluate the performance of the suggested detection scheme. Also, sensitivity of the proposed method has been investigated under different noisy conditions. At last the obtained results are compared with the accuracies of some reported methods of previous researches.

Multiple output DC-DC converters are widely used in many applications such as aerospace, industrial and medical equipments. The purpose of this paper is to present an intelligent control system for the multiple output DC-DC converters. In order to perform this purpose, a double ended forward DC-DC converter with three output voltages (+5 V/ 50W, +15 V/ 45W and -15 V/ 15W) is considered and analyzed. The voltage mode weighting factor control system with Genetic Algorithm (GA) is performed on the considered DC-DC converter. Furthermore, a PID controller is utilized to minimize the total steady state error. The stability proofs of the system in presence of PID Controller have been analyzed.The results show that the GA weighting factors estimator improves the cross and output regulations in multiple output DC-DC converters. Simulation results verify and confirm the truth and accuracy of the proposed method.

In this paper the problem of serial batch scheduling in a two-stage hybrid flow shop environment with minimizing Makesapn is studied. In serial batching, it is assumed that jobs in a batch are processed serially, and their completion time is defined to be equal to the finishing time of the last job in the batch. The analysis and implementation of the prohibited transference of jobs among machines of stage one in serial batch is the main contribution of this study. Machine set-up and ready time for all jobs are assumed to be zero and no Preemption is allowed. Machines may not breakdown, but at times they may be idle. As the problem is NP-hard, a simulated annealing and genetic algorithm are proposed to provide near-optimal solutions. Since this problem has not been studied previously, therefore, a lower bound is developed for evaluating the performance of the proposed SA and GA solutions. Many test problems have been solved using SA and GA; results show both solving procedures provide near-optimum solutions regarding the lower bound solution. In the case of large scale problems, solutions provided by GA overcome those from SA algorithm.

In this paper, we study the location routing problem with intermediate replenishment facilities (LRPIRF), an extension of the location routing problem (LRP), where the vehicles can replenish at some intermediate facilities. Vehicles leave the depot with load on-board, serve customers until out of load, may return to an intermediate facility to replenish, and finally return to the depot, completing their route. In this paper, we initiate a mathematical mixed integer programming model with new kind of subtour elimination constraints for this problem. Moreover, the facility location phase is consideredbesides vehicle routing phase in our problem. The objective of the problem is to find routes for vehicles to serve all customers at a minimal cost in terms of total travel cost and total facility location cost, without violating the capacity constraint of the vehicles. The solution to the LRPIRF is obtained through CPLEX solver in commercial software GAMS 23.5.1, Genetic Algorithm and Tabu Search algorithm. Computational results are obtained on a set of randomly generated instances and indicate the effectiveness of the proposed algorithms in terms of solution time and quality.

A Bayesian analysis is used to detect a change-point in a sequence of independent random variables from exponential distributions. The Bayes estimators are derived for change point, the rate of exponential distribution before shift and the rate of exponential distribution after shift. Likelihood, Prior, Posterior and Marginal distribution of the change point is derived. Also, maximum likelihood estimation (MLE) method is used for determining change point. The sensitivity analysis of Bayes estimators are performed by simulation. Also, we suggest a new approach to achieve more precise results by determining correct choice for parameters of prior distribution and compared the approach with existing methods. The result of simulation shows good performance of proposed approach in comparison with existing methods. Also, a sensitivity analysis on the location of the shift is performed.

In order to obtain the bulk brick-like samples, the mixture of steel slag, and sintering aid additive (like dolomite, glass, perlite borax and phosphate sodium) were sintered at 1100°C for 2 minutes. The flat and bloated surface appearances were obtained. The bulk densities of final sintered composites ranged from 1.3 to 2.41 g/cm3 and total porosities were from 15 to 40%. The bending strengths varied from 5.5 to 15.9 MPa. The final phase as detected by XRD according was calcium magnesium silicate.

In this research, porous magnesium-zinc scaffolds were prepared by powder metallurgical process and nano hydroxyapatite (HAP) coating on the Mg-3Zn (wt.%) scaffold was prepared by pulse electrodeposition and alkali treatment processes to improve the corrosion resistance of the scaffold. The results indicated the as-deposited coating consists of HAP, DCPD and OCP with needle like and plate-like structures and the post-treated coating was composed of needle-like particles of nano HAP that developed almost perpendicularly to the substrate. Electrochemical tests showed that the corrosion potential of scaffold significantly increased from -1.475 to -1.365 V and the corrosion current density reduced 1.5-fold in comparison to the scaffold modified by nano hydroxyapatite coating.

Ceramic materials due to their high compressive strength and hardness have been one of prime candidates in armor design in particular when high level threats (impact velocity above 6 m/s) are involved. The aim of this work is to investigate ballistic impact performance for a target plate containing novel ceramic inserts and compare it to ceramic tiles embedded in polyurethane based matrix. Two size 98% alumina (Al2O3) base ceramic inserts with 10 mm diameter and 6 and 10mm in length were used in the specimen’s preparation. In addition, 6 and 10mm thick ceramic tiles were used to compare the ballistic performance. Smooth bore gas gun was used to carry out high velocity ballistic impact tests in velocity range of 530- 830m/s on both target plates. Results showed outstanding ballistic performance by the target plate with ceramic inserts in term of lower residual velocity for the specimens which experienced perforation and lower damage area compared to totally disintegrated plates containing ceramic tiles. Specimens containing ceramic inserts also showed good ballistic resistance in case of multiple impacts whereas the specimens with ceramic tiles almost totally lost its ballistic potentials. Ability to repair on site (debris removal and new ceramic insert replacement) is among unique advantages of this novel design in the armor application.

In this paper, a size-dependent formulation for the Bernoulli-Euler beam is developed based on a new model of couple stress theory presented by Hadjesfandiari and Dargush. The constitutive equation obtained in this new model, consists of only one length scale parameter that is capable of capturing the micro-structural size effect in predicting the mechanical behavior of the structure. Having one length scale parameter is claimed to be an advantage of the model in comparison with the classical couple stress theory. The governing equations and boundary conditions of the Bernoulli-Euler beam are developed using the variational formulation and the Hamilton principle. The static bending and free vibration problems of a Bernoulli-Euler beam with various boundary conditions are solved. Numerical results demonstrate that the value of deflection predicted by the new model is lower than that of the classical theory. It is also found that natural frequencies obtained by the present couple stress model are higher than those predicted by the classical theory. The differences between results obtained by the present model and the classical theory become significant as the thickness of the beam gets close to the length scale parameter of the beam material.

The aim of this study is to optimize the performance functions of turbofan engines. In this way, the multi-objective genetic algorithm is employed to optimal design of turbofan with considering the offdesign model of engine. The design variables are high-pressure compressor pressure ratio, lowpressure compressor pressure ratio, fan pressure ratio and bypass ratio. They are calculated in such a way that the performance functions are at their best conditions simultaneously. The performance functions are specific thrust at take-off, and thrust specific fuel consumption, propulsive, thermal, and overall efficiencies at cruise. The optimization is carried out using the modified NSGA II which is among the best multi-objective genetic algorithm methods. The results of this optimization will be a set of vectors which the designer may choose one of those according to the problem conditions.

This work uses the dual-phase-lag (DPL) model of heat conduction to demonstrate the effect of temperature gradient relaxation time on the result of non-Fourier hyperbolic conduction in a finite slabsubjected to a periodic thermal disturbance. DPL model combines the wave features of hyperbolic conduction with a diffusion-like feature of the evidence not captured by the hyperbolic case. For the firsttime, the analytical solution of DPL model of heat conduction equation is obtained adopting Laplacetransform method and inversion theorem. The temperature profiles at the front and rear surfaces of the slab are calculated for various temperature gradient relaxation times. The phase and amplitude difference between the front and the rear surface are calculated numerically as a function of the temperature gradient relaxation time, which have been reported previously as a function of heat flux relaxation time. The results demonstrate that increasing the temperature gradient relaxation time leads to the lower phase difference and upper amplitude difference between the temperature responses of the front and rear surfaces.

A complete investigation on the free vibration and stability analysis of beams made of functionally graded materials (FGMs) containing open edge cracks utilizing four beam theories, Euler-Bernoulli, Rayleigh, shear and Timoshenko, is performed here. It is assumed that the material properties vary along the beam thickness exponentially and the cracked beam is modeled as two segments connected by two mass-less springs, extensional and rotational spring. Afterward the equations of motion for the free vibrations and buckling analysis are established and solved analytically for clamped-free boundary conditions. A detailed parametric study is also performed to examine the influences of the location and depth of the crack, material properties and slenderness ratio of the beam on the free vibration and buckling characteristics of cracked FGM beams for each of the four engineering beam theories.

In this paper a new method to determine the fracture properties and strain energy release rate for carbon-polyester composite has been introduced. Fracture characteristics such as: critical stress intensity factor and critical strain energy release rate for mode I, mode II and mixed mode loading were determined using Arcan type specimen. 130 layers of carbon fiber polyester woven composite with each of 0.2mm thickness were put on each other. Theoretical studies to determine strain energy release rate were done using three Corrected Beam Theory (CBT), Compliance Calibration Method (CCM), Virtual Crack Closure Technique (VCCT), and results were recorded and compared with the results from experimental and numerical attempts. Critical loads were recorded through experimental attempts then applied to the finite element software. Results were recorded and compared with each other to determine the best method. Results show that CCM and VCCT determine strain energy release rate value closer to J-integral in comparison with corrected beam theory. Finally, the fracture surfaces were examined by scanning electron microscope to gain insight intothe failure responses that shows the fracture surface for mode II is rougher than the fracture surface for mode I and mixed mode.