International Journal of Engineering
Volume:28 Issue: 4, Apr 2015

The nonlinear solvers in numerical solution of water flow in variably saturated soils are prone to convergence difficulties. Many aspects can give rise to such difficulties, like very dry initial conditions, a steep pressure gradient and great variation of hydraulic conductivity occur across the wetting front during the infiltration of water. So, the averaging method applied to compute hydraulic conductivity between two adjacent nodes of the computational grid is one of the most important issues influencing the accuracy of the numerical solution of one-dimensional unsaturated flow equation i.e., Richards’ equation. A number of averaging schemes such as arithmetic, geometric, harmonic and arithmetic mean saturation have been proposed in the literature for homogeneous soil. The resulting numerical schemes are evaluated in terms of accuracy and computational time. It can be seen that the averaging scheme in the framework of arithmetic approach favorably to other methods for a range of test cases.

In this work, Fe/TiO2 nanostructured catalyst was prepared using sol-gel method developed by Yoldas and tested in degradation of phenol in water under UV radiation. The synthesized catalyst was characterized by XRF, XRD, specific surface area and porosimetry, and SEM methods. The porosimetry revealed the mesopore structure of the catalyst. Results of SEM confirmed the nano dispersion of iron oxides on titania support. Effects of Fe load of the catalyst, dosage of the catalyst, pH, H2O2 amount, and time were investigated. Results of phenol photodegradation over Fe/TiO2 showed that the reaction followed an apparent first order kinetics at low phenol concentration and the apparent rate constant was 0.0017 min-1. Also, there was an optimum for Fe load of the catalyst.

The influence of carbon content in three organic dyes, blue21, yellow20, and green40 on the adsorption behavior using organo-bagasse as a biosorbent was investigated. The organo-bagasse was prepared by adsolubilisation using tetradecyltrimethyl ammonium bromide as a chemical modifying agent. The precursor and organo-bagasse were characterized by elemental analysis, Brunauer-Emmett-Teller method, Fourier transform infrared spectroscopy spectra, and scanning electron microscopy images. A number of batch tests were carried out as functions of contact time, initial pH solution, and initial dye concentration. The results showed that the adsorption capacity of green40 was the highest, followed by yellow20 and then blue21. Adsorption of the organic dyes increased as the carbon content in the organic dyes increased. The adsorption of the three dyes reached equilibrium within 3.0 h and at this condition the adsorption capacities of blue21, yellow20, and green40 were 130.50, 166.55 and 174.81 mg/g respectively. The maximum adsorption was obtained at pH 2.0. The kinetic data followed the pseudo-second order model indicating rate of interacting formation on the biosorbent surface was the rate of limiting step. The results showed that the carbon content in the organic dyes had a significant effect on the adsorption behavior of organic dyes by the organo-bagasse.

A generation method for the rail random irregularity with arbitrary wavelength interval (WI) is developed, and its accuracy and efficiency are demonstrated. Then a moving wheel-rail-bridge interaction element is derived to establish the finite element equations of motion for the train-rail-bridge interaction system, and the flow chart of assembly and calculation for the system equations is given. According to the sub-interval principle, the influences of the irregularities with the large WI and the sub-intervals on the dynamic responses are analyzed by a numerical example, and the sensitive WI of each response is discussed. The results indicate that the bridge acceleration and the contact force are both more sensitive to the irregularity with WI (1~5 m). The irregularity with WI (0.1~1 m) has less influence on the car body acceleration but mainly contributes to the rail acceleration. However, all the irregularities with wavelengths in interval (1~150 m) can have significant influences on the car body acceleration. Meanwhile, the transient jump of wheel can be simulated and should be taken into account for the derailment risk assessment.

Need for high speed internet connectivity has lead to a substantial research in switching systems. Buffered crossbar switches have received a lot of attention from both research and industrial communities due of its flexibility and scalability. Designing a scheduling algorithm for buffered crossbar switches without starvation is a major challenge as of now. In this paper, we proposed a Delay based Prioritized Queue with Round-robin Scheduler (D-PQRS) which uses no speedup. Simulation result shows that D-PQRS reduces the starvation considerably with maximum throughput and minimum delay comparable to PQRS and LQF-RR.

A bunch of factors including the limited fossil resources and rising of fossil fuel price have been causes moving to create the new structure that is based on providing energy security, and protect the environment. One of the alternatives is the fuel cell (FC). Maximum power point tracker has an important role to increase the efficiency of the FC systems. One of the difficulties in maximum power point tracking methods is rapid changes in operating conditions which affects the maximum power point (MPP) of FC. The main contribution of this paper is presentation of a robust and reliable maximum power point tracking (MPPT) method for tracking of MPP of FC under fast variation of operating conditions. The proposed method is based on eagle strategy. In order to verify the accuracy of the proposed method, simulations are performed in MATLAB/SIMULINK. The proposed method is compared with perturb and observe (P&O) and fuzzy MPPT methods. The results show that eagle strategy based MPPT approach can track the MPP of fuel cell better than P&O and fuzzy MPPT. The main features of the proposed approach are high speed for duty cycle determining and high accuracy in MPP tracking of FC in the any contingency.

In this paper, the path following controller of an omnidirectional mobile robot (OMR) has been extended in such a way that the forward velocity has been optimized and the actuator velocity constraints have been taken into account. Both have been attained through the proposed model predictive control (MPC) framework. The forward velocity has been included into the objective function, while the actuator saturation has been considered as hard constraints. As shown in the simulation results, the OMR can converge to and follow a reference path successfully and safely. The forward velocity of the robot was close to the desired one and the desired orientation angle was achieved at a given point on the path, while the actuator constraints were not violated. Furthermore, to show the effectiveness of our proposed framework, a comparison with conventional approaches used to bound actuator constraints has been conducted. Mean squared error (MSE), integral squared error (ISE), and traveling distance were used as performance indices. As seen in the results, the proposed control strategy outperforms the conventional approaches. The proportion between translational and rotational velocities was optimized, although the limitation of the rotational and translational velocities was coupled via the OMR’s orientation angle.

In this paper an analytic approach to estimate the nonlinearity of radix-4 pipelined analog-to-digital converters due to the circuit non-idealities is presented. Output voltage of each stage is modeled as sum of the ideal output voltage and non-ideal output voltage (error voltage), in which non-ideal output voltage is created by capacitor mismatch, comparator offset, input offset, and finite gain of amplifier. The integral nonlinearity (INL) can be obtained as the expected value of total input error due to the errors in all stages of radix-4 pipelined ADC.

Recently, a new data driven controller synthesis is presented for calculating the family of stabilizing first, second and fixed order controller using frequency respons. However, this method is applicable just for plants that can guarantee some smoothness at the boundary of the resulted high dimension LMI. This paper solve that issue and extends the approach to fixed order controllers guaranteeing some performance criteria which are applicable for the more general types of plants. It is shown that knowing the frequency response of plant is sufficient to calculate the stabilizing fixed order controllers from a set of convex linear inequalities. The norm on sensitivity and complementary sensitivity functions are satisfied from some frequency domain inequalities (FDI) that could be examined from frequency response data. The usefulness of the proposed approach is illustrated by an academic example.

The rheological and tape casting behavior of ethanol-based Bi0.5(Na0.80K0.20)0.5TiO3-7 mol% BiFeO3 (BNKT-BF) slurries was investigated. The effect of sintering temperature profile on texture development with a preferred <001> orientation was also studied. A 50 MPa pressure assisted three step sintering profile promoted extensive texture development together with densification. The role of BF as a sintering promoter has been discussed.

In this work, Poly(ethyleneterephthalate) (PET) substrate was treated using KOH solution and was modified using hybrid O-I coating containing PCL)polycaprolactone(as organic phase and TEOS)tetraethoxysilane(as inorganic phase. The coating was prepared through a sol-gel process and applied on the surface by dip coater. Then, electrically conducting polythiophene (PTh) nanoparticles were deposited on the surfaces using chemical deposition method. A facile and rapid chemical oxidative deposition method using a binary organic solvent system during 12 min of reaction time was used and the effect of surface modification by hybrid coating on morphology of PTh nanoparticles were studied. The optical transparency of PTh nanoparticles coated on PET films characterized by UV-Vis spectroscopy. Field-emission scanning electron microscopy (SEM) and laser particle-size analysis were used to study surface morphology, average size and size distribution of PTh nanoparticles. Electrical conductivity of PET substrate deposited by PTh nanoparticles was measured using four probe to be 1.7×10-5 S/cm.

Slewing bearing, which is widely applied in tank, excavator and wind turbine, is a critical component of rotational machine. Standard procedure for bearing life calculation and condition assessment was established in general rolling bearings, nevertheless, relatively less literatures, in regard to the health condition assessment of slewing bearing, were published in past. Real time health condition assessment for slewing bearing is used for the purpose of avoiding catastrophic failures by detectable and preventative measurement. In this paper, a new strategy was present for health evaluation of slewing bearing based on multiple characteristic parameters, and ANN (Artificial Neural Network) and ANFIS(Adaptive Neuro-Fuzzy Inference System) models were demonstrated to predicted the health condition of slewing bearings. The prediction capabilities offered by ANN and ANFIS were shown by using data obtained from full life test of slewing bearings in NJUT test System. Various statistical performance indexes were utilized to compare the performance of two predicted models. The results suggest that ANFIS-based prediction model outperforms ANN models.

In design and fabricate drive shafts with high value of fundamental natural frequency that represented high value of critical speed; using composite materials instead of typical metallic materials could provide longer length shafts with lighter weight. In this paper, multi-objective optimization (MOP) of a composite drive shaft is performed considering three conflicting fundamental natural frequency, critical buckling torque and weight of the shaft. Fiber orientation angle, ply thickness and stacking sequence are also considered as the design variables in this MOP. To solve this MOP, Modified Non-Dominated Sorting Genetic Algorithm (modified NSGA II) is employed. To calculate fundamental natural frequency and critical buckling torque, finite element model of a truck composite drive shaft has been carried out using commercial software ABAQUS/Standard. Finally optimum design points are obtained and from all non-dominated optimum design points, some trade-off points are picked using multi-criteria decision analysis methods and the points are discussed.

The significant costs insert on mineral processes due to mill liner wear including the labor costs, price of material and shut down periods. Therefore, the study of this phenomenon is economically important to optimize the mill operating conditions and liner profile design to decrease the wear rate. There is no appropriate and applicable research on impact wear evaluation of mill liners. In the present work, a procedure is presented for evaluation of impact wear of mill liners. A test machine is used to do impact wear experiments in different conditions of ball size, velocity and impact angle. A single relation of wear evaluation can be extracted of the experimental data. This relation is used to evaluate the liner wear due to impacts. The procedure is validated by measured liner wear of a laboratory mill. A plate is positioned in front of the cataract regime to eliminate it and enable us to measure the abrasion and impact wear separately. The comparisons show the acceptable accordance of evaluated and measured data so the liner wear of an operating mill can be evaluated by the procedure. The operating mill is in Sarcheshmeh copper complex in Iran. These studies helps us to have appropriate liner designs in order to postpone the liner wear and shut down periods as long as maintaining the mill performance.

The combined effects of nanoparticle and magnetic field on the nonlinear Jeffery-Hamel flow are analyzed in the present study. The basic governing equations are solved analytically to nonlinear ordinary differential equation using perturbation method together with a semi-numerical analytical technique called Hermite- Padé approximation. The obtained results are well agreed with that of the Adomian decomposition method (ADM). The velocity profiles are presented in divergent channel for various values of nanoparticle solid volume fraction, Hartmann number, Reynolds number and channel angle. The relations between velocity field with Reynolds number and channel angle with the effect of nanoparticle solid volume fraction and Hartmann number are also performed qualitatively.

This paper presents exergy and exergoeconomic analysis and parametric study of a Diesel engine based Combined Heat and Power (CHP) system that produces 277 kW of electricity and 282 kW of heat. For this purpose, the CHP system is first thermodynamically analyzed through energy and exergy. Then cost balances and auxiliary equations are applied to subsystems. The exergoeconomic analysis is based on specific exergy costing (SPECO) method. Finally a parametric study is used to show effect of ambient temperature on important energy, exergy and exergoeconomic parameters of the CHP system. Also effects of change in compressor pressure ratio and turbine inlet temperature on these parameters are investigated in different environment temperatures. The results show that increasing ambient temperature increases the work output, heating power and exergoeconomic factor and decreases the exergetic efficiency and cost of exergy destruction. Increasing compressor pressure ratio leads to increase in the work output, heating power, exergetic efficiency, and exergy destruction cost and exergoeconomic factor of the CHP system in all environment temperatures. Also increasing turbine inlet temperature decreases the work output, exergetic efficiency and exergoeconomic factor while increases the heating power as well as exergy destruction cost in all environment temperatures.

In this work, single-stage and two-stage tubular solid oxide fuel cell (SOFC)/gas turbine hybrid cycles are comparatively examined from the energy and exergy viewpoints. For this purpose, mass, energy and exergy balances are applied to all components of the cycles. The behavior of tubular solid oxide fuel cell modeled in this study is validated with the experimental test data of tubular SOFC developed by Siemens Westinghouse. The results of simulation show that two-stage SOFC-GT hybrid cycle not only generate more power,but also it has high efficiency in comparison to single-stage SOFC-GT. The values of first law efficiency and Exergetic Performance Coefficient (EPC) are increased from 60.69% and 1.405 in single-stage SOFC-GT to 63.93% and 1.725 in two-stage SOFC-GT respectively. This means that for equivalent generated power of single and two-stage SOFC-GT hybrid cycles, the amount of exergy destruction for two-stage SOFC-GT cycle is less than single-stage SOFC-GT. Also exergy destruction of all components of the hybrid cycles is calculated separately and results are compared. Finally a parametric study is performed to find out optimal values for solid oxide fuel cell design parameters. Effects of these parameters are evaluated on efficiency, generated power and total exergy destruction of the hybrid cycles.

The Performance of electric vehicle IGPT Pin fin heat sink can be measured by the temperature field and the fluid pressure and other parameters. In order to improve the cooling effect of Pin fin heat sink, diameter, length and distance of the fin was optimized combination. The relationship between pressure drop of the water inlet, outlet and pin fin parameters was analyzed and calculated. It was respectively analyzed that pressure drop effect on different parameters of 9 groups pin fin heat sink structure project respectively by using the orthogonal design thought. Among the pressure drop curves of 9 schemes, results in scheme 1、5、6、9 were moderate and were in favor of improvement of comprehensive property of heat sink. It was obtained that optimum structure parameters combined of pin fin heat sink of the pressure drop of moderate through the study of the influence of the main parameters of pressure drop. According to the optimum structure parameters, experimental cooling system platform was set up and experiment had been carried on. The optimum structure product of electric vehicle IGPT Pin fin heat sink was produced

In this paper a novel method is proposed for construction of an exponential observer for nonlinear system. The presented method is based on direct solution of dynamic error without any linearzing of nonlinear terms. Necessary and sufficient conditions for construction of direct observer are presented. Stability of the observer is checked using Lyapunov theorem. Also the ability of this observer is checked with implementing of observer for fault detection of micro tunable capacitor subjected to nonlinear electrostatic force.

The heat pipe applications have been coupled with the renewable energy such as solar energy, waste heat and geothermal energy. Thermosyphon Rankine Cycle (TRC) is a vertical wickless heat pipe engine. In this engine, the turbine is installed between the insulated section and a condenser section of thermosyphon. The mechanical energy developed by the turbine can be converted to electricity, by direct coupling to an electrical generator. Present work simulation results showed that the enhanced TRC model is able to increase the efficiency of the TRC system. This paper introduces the miscellanies new ways in order to improve the performance of a TRC system for supplying the sustainable electricity. For example, the increasing percent of the turbine useful efficiency due to the superheating process was obtained as 0.78%.