International Journal of Engineering
Volume:29 Issue: 8, Aug 2016

Two phenomena can produce chattering: switching of input control signal and the large amplitude of this switching (switching gain). To remove the switching of input control signal, dynamic sliding mode control (DSMC) is used. In DSMC switching is removed due to the integrator which is placed before the plant. However, in DSMC the augmented system (system plus the integrator) is one dimension bigger than the actual system and then, the plant model should be completely known. To overcome this difficulty, a fuzzy system is employed to identify the unknown nonlinear function of the plant model and then, a robust adaptive law is developed to train the parameters of this fuzzy system. The other problem is that the switching gain may be chosen unnecessary large to cope on the unknown uncertainty. To solve this problem, another fuzzy system is proposed which does not need the upper bound of the uncertainty. Moreover, to have a suitable small enough switching gain an adaptive procedure is applied to increase and decrease the switching gain according to the system circumstances. Then, chattering is removed using the DSMC with a small adaptive switching gain (ASG). As a case study, nonlinear chaotic Duffing-Holmes system is selected.

Acceptance Sampling models have been widely applied in companies for evaluation the raw material as well as the final products. Meanwhile, process capability indices (PCIs) have been used in various industrial environments as capability measures that are obtained based on process departure from a target, process yield, process consistency, and process loss. In this research first a repetitive group sampling (RGS) plan based on process capability index is developed for variables inspection. Then the optimal parameters of proposed RGS plan are determined and also a new multiple dependent state (MDS) sampling plan, a double sampling plan (DSP) and a sampling plan for resubmitted lots have been developed and Finally, a comparison study has been carried out between proposed sampling plans and the results are elaborated.

this paper focuses on the turbine-generator shaft models of double-cage Induction Generator (IG) based wind farm and its influence on the sub-synchronous resonance phenomenon. For this purpose, six different shaft models as 6-mass, 4-mass, 3-mass I, 3-mass II, 2-mass and 1-mass models are considered for double-cage IG wind-turbine. By using the linear modal analysis method, the effects of the different multi mass model of double-cage IG wind-turbine on the SSR phenomenon are studied. The results obtained by eigenvalue analysis show that the model of double-cage IG wind-turbine has an important effect on the detecting of Subsynchronous Resonance (SSR) phenomenon. The analytical results are validated by detailed electromagnetic transient simulation using PSCAD/EMTDC software.

Wiener filter suppresses noise efficiently. However, it makes the out image blurred. Curvelet preserves the edges of natural images perfectly, but, it produces visual distortion artifacts and fuzzy edges to the restored image, especially in homogeneous regions of images. In this paper, an efficient image denoising framework based on Curvelet transform and wiener filter is proposed, which can reduce noise better than these methods. The performance of introduced scheme is evaluated in terms of two important denoising criteria, PSNR and SSIM on standard test images in different noise levels. Three famous thresholding ‘soft’, ‘semisoft’ and ‘hard’ are applied to noisy images and results are fused by the wavelet transform to form restore images. Our framework outperforms the curvelet transform denoising by %6.3 in terms of PSNR and %5.9 in terms of SSIM for ‘Lena’ image. The visual outputs show that false artifacts, parasite lines and the blurring degree of output images, are reduced significantly. The obtained results reveal the superiority of our framework over recent reported methods.

In recent years, flexible manufacturing system as a response to market demands has been proposed to increase product diversity, optimum utilization of machines andperiods of short-term products.The development of computer systems has provided the ability to build machines with high functionality and the necessary flexibility to perform various operations. However, due to the complexity and the random nature of these problems, deterministic algorithms are not highly accurate andefficient enough. In this paper, computer simulation models are used to optimize flexible manufacturing system FMS). The objectives of this paper are included:the optimal time served in each unit, the optimal number of servers in each unit, and the optimum number of domestic transportation fleet based on type. At the first step, source-destination traffic matrix is presented for development, including: service time and traffic volume are used. The computational results show the accuracy and efficiency of using simulation tools in these problems.

Knowledge of droplet behavior is one of the most important criteria for determination of mass transfer kinetics for choosing the type of liquid-liquid extraction columns. Mean drop size data of dispersed phase droplets in continuous phase were obtained for various rotary agitated liquid-liquid extraction columns. The effects of operational variables such as rotor speed and dispersed and continuous phase velocities were investigated. In addition, the effect of mass transfer direction was studied on the Sauter mean drop diameter. The Sauter mean drop diameter was influenced mainly by mass transfer direction and agitation speed. In this research work, previous experimental works in agitated extraction columns (RDC, ARDC, PRDC, Scheibel, Oldshue-Rushton and Kühni columns) are reviewed. Calculations with the literature correlations cannot predict experimental data, thus unified correlations considering the physical properties, operating conditions and geometric parameters were provided to predict the mean drop size (d32). The results of the proposed correlation were compared with the experimental data obtained from the literature and the present investigation. This correlation covers several physical systems for various rotary agitated extractors. Findings of this study demonstrated that the proposed correlation leads to an accurate prediction for the Sauter mean drop diameter in rotary extraction columns.

This paper presents a new design of a CPW-Fed multi-bands planar antenna. This antenna can be integrated easily with passive and active elements. The proposed antenna is suitable to operate for GPS, PCS and WiMAX bands. Its entire area is 52.3x52.6mm2 and is employed on an FR-4 epoxy substrate and fed by a 50 Ohm coplanar line. The antenna parameters have been analyzed and optimized by using ADS “Advanced Design System”. Before passing to the fabrication of this antenna structure, we have conducted an study into simulation by using CST Microwave studio and Ansoft’s HFSS solvers in order to verify the ADS results. The fabrication and the test of the final circuit permit to have a good agreement between simulation and measurement results.

Design and manufacturing technology of high pressure multistage pumps which are commonly utilized in oil and gas industries, used to be imported from foreign companies. Due to international sanctions against I. R. Iran, it started to be designed and launched domestically. Nowadays all production lines including design, manufacturing and testing of these pumps have been performed by Iranian experts and they are highly competitive with similar pumps available in international market. This study presents a part of research on first domestic BB3-6×6 multistage pump design and manufacturing as a national project. Pump casing was designed in and structural static analyses performed on it using Ansys. When the casing was approved, a gating system was devised on pump upper half casing and casting simulation was done by NovaCast. The effect of gating system on shrinkage defects was investigated. Results revealed that sprue size and riser location have a noticeable impact on shrinkage of part. This research illustrated that using simulation approach before manufacturing, has a noticeable effect on production cost.

This paper describes third aircraft model with 2 degrees of freedom. The aim of this study is to develop a mathematical model for investigation of adoptable landing gear vibration behavior and to design Proportional Integration Derivative (PID) classical techniques for control of active hydraulic nonlinear actuator. The parameters of controller and suspension system are adjusted according to bees optimization algorithm by minimizing body acceleration objective function. The results of numerical simulation indicates that the active landing gear system based on bees intelligent algorithm increases passengers and ride comfort and structure fatigue life by decreasing displacement, acceleration and load transmitted to airframe and shock absorber system significantly about 70% and 80% averagely compared to passive performance during touchdown phase with sine wave runway disturbance.

An effective wide-band, active control law based on a type of Dynamic Vibration Absorber (DVA) was proposed and investigated in this study. Using the mechanical impedance method, an active DVA control law was formulated based on the passive mechanical model. The resulting electrical DVA was capable of generating multi-mode active damping to its attentive structure. The host structure was an aluminum plate with an acceleration signal fed back through the controller to a collocated piezoelectric actuator. An experimental system was constructed employing the DVA and an open loop analysis showed that the control system had better a roll-off property than the Direct Velocity Feedback (DVF) controller. Furthermore, real time control results demonstrated that the multiple vibration modes can be simultaneously suppressed. In addition, the measured sound isolation performance below 1 kHz was found to be as high as 6 dB. The proposed method is simple and effective and is readily applicable to a variety of structures.

Shell and tube heat exchangers are widely being used in many of industrial and power engineering applications. Different techniques have been employed in order to enhance the performance of the heat exchanger. Air bubble injection is one of the method increase the turbulence of the flowing fluids which in turn enhance the heat transfer performance. Injecting air bubbles is one of the promising technique which doesn’t requires much complex systems. Air can be injected at different points. In this paper, analysis over heat transfer performance and exergy analysis with different air injection points. Four different cases with and without air injection in shell or tube side have been taken into consideration and the results have been compared. Through the study, it has been observed that injecting air bubbles throughout the tube enhances the heat transfer rate by 25-40% at different range of the Reynolds Number. The effect of air injection at different points also affects the overall heat transfer and the dimensionless exergy loss.

A novel multiband multiple-input-multiple-output (MIMO) antenna system is proposed. The MIMO antenna system consists of two antenna elements, each of which comprises of three radiators: a driven monopole, an S-shaped strip and an inverted F-shaped strip and occupies footprint of 15x18.5x0.8 mm3 only. The driven monopole acts as a quarter-wave monopole and stimulates higher mode resonance. The two strips are excited by electromagnetic coupling from the driven monopole and serve as two additional monopoles leading to a wideband performance for the lower band. The bandwidths (VSWR ≤ 2.75) achieved for the antenna element are 1.67 – 2.2 GHz for the lower band and 2.28 –2.95 GHz for the upper band which cover LTE-1, LTE- 2, LTE- 3, LTE- 7, LTE- 40 and WLAN 2.4 GHz bands. A T-shaped slot and another two slots are introduced to reduce the coupling effect between the two multiband antenna elements. The isolation achieved is higher than 18 dB over the whole band, leading to an envelope correlation coefficient of less than 0.01. Furthermore, the diversity characteristics of mean effective gains (MEGs) and diversity gain (DG) are also studied. Both the simulated and measured results are shown to illustrate the performance of the proposed multiband MIMO antenna system, and that confirms the suitability for Long Term Evolution (LTE) and wireless local area network (WLAN) handset applications.

In this study, solid state fermentation (SSF) was carried out to produce single cell protein (SCP) from sugarcane bagasse using Saccharomyces cerevisiae. The SSF experiments were performed in a tray bioreactor. The influence of several parameters including extraction buffer, initial moisture content of substrate, fermentation time, relative humidity in bioreactor, the bioreactor temperature and pretreatment of substrate on SCP production yield was considered. Among the used extraction buffers, carbonate-bicarbonate buffer was the most effective one for protein extraction. The obtained results revealed that the suitable fermentation conditions were initial substrate moisture content of 70%, fermentation time of 72 h, relative humidity of 85%, bioreactor temperature of 35 oC and pretreatment of substrate using 2% NaOH solution; at this optimum condition protein production yield of 13.41% was attained. The amino acid analysis of the produced protein showed that the product contained almost all of the essential amino acids as well as some non-essential ones.

In this paper a dual band and high gain H-plane horn antenna implemented by substrate integrated waveguide (SIW) using a single layer thin substrate is introduced. The proposed antenna consists of five parts of rectangular waveguide with different width arranged in a staircase manner to allow mode combination of fundamental and higher propagating modes of the structure. By adjusting the length and width of different parts, suitable combination of amplitude and phase along radiating aperture is occurred and half power beamwidth at H-plane pattern is improved. A grounded pin is added at the middle of the radiating aperture to improve Side Lobe Level (SLL) and to obtain dual band operating condition. Moreover, by adding a metallic reflector plate around the radiating aperture, the antenna gain is enhanced. The proposed antenna has been successfully simulated, fabricated and its radiation performances including reflection coefficient, radiation patterns are measured in an anechoic chamber. Measured results show that antenna gain is 9.6 dBi and 7.2 dBi at the first and second band respectively.

The purpose of this work was to study the effect of initial pH and yeast Saccharomyces cerevisiae on biogas production from tofu wastewater (TW). The initial pH was varied in ranging of 5 – 9 in substrate without yeast (T5-T9) and with yeast (TY5-TY9). The results showed that optimum initial pH was 8. The maximum biogas was resulted in T8 (275 mL) and TY8 (421 mL). Yeast addition increased total biogas 22.91-81.97% compared with no yeast addition. Kinetic of biogas production was modeled through modified Gompertz and Cone model. The predicted biogas in Cone model was more precise than that in modified Gompertz. The difference between measured and predicted biogas in Cone and modified Gompertz model was 0.193 – 2.809 and 0.316 – 3.115 % respectively. The presence of yeast increased the kinetic constant of ym (biogas potential, mL), increased λ (lag period, days), and decreased khyd (hydrolysis rate, /day).

The facility location problem is a strategic decision-making for a supply chain, which determines the profitability and sustainability of its components. This paper deals with a scenario where two supply chains, consisting of a producer, a number of distribution centers and several retailers provided with similar products, compete to maintain their market shares by opening new distribution centers because of increasingin demand. The competition problem is formulated as a non-linear integer bilevel mathematical model, where the upper level represents thedecisions of the leader producer and the lower level administrates the decisions of the follower producer. It has been shown that even insmallscaleproblems, bilevel mathematical programming problems are strongly NP-hard, so an adapted bilevel ant colony algorithm with inter-level information sharing is developed to solve the problem.To evaluate the performance of the developed ant colony algorithm, the upper bound of the competitive facility location problem is determined by solving the upper-level problem as an integer linear programming model without considering the follower’s decision. Comparing the computational results of the developed ant colony algorithm with those of the determined upper bounds shows the satisfactory capability of the proposed approach of solving even medium- and large-scale problems.

In the present study, an unlooped pulating heat pipe has been considered with two liquid slugs and three neighboirng vapor plugs.The governing equations such as momentum, energy and mass equations are solved explicitly except the energy equation of liquid slugs.The aim of the present study is to calculate the entropy generation through the performance of a pulsating heat pipe. Additionally, the effects of different pipe diameters and evaporator temperatures have been investigated. Besides, Bejan number has been derived for each case study to investigate the share of heat transfer in entropy generation. According to the results, by increasing the pipe diamtere the sensible and latent heat transferred into the pulsating heat pipe enhance and the liquid slugs oscillate in high amplitudes. On the other hand, the entropy generation value increases as the pipe diameter increases. The evaluated Bejan numbers show that the viscous effects share in entropy generation decreases as the pipe diameter increase. Previous studies report that there is a threshold of pulsating heat pipe diameter to operate. However, the results of the present paper demonstrate that the using pulsating heat pipes are not reasonable in small diameters. Moreover, the results show that the heat removing performance of pulsating heat pipe improves as the temperature difference of the evaporator and condenser increases. The calculated results demonstrate increment in total entropy generation in high evaporator temperatures. Moreover, the Bejan number will increase by any increment in the evaporator temperature and this phenomenon reveals the insignificant role of viscous effects in high evaporator temperatures. To validate the calculations, the results have been compared to the previous ones. This comparison shows very good agreement between them.