International Journal of Engineering
Volume:28 Issue: 6, Jun 2015

Reliable estimation of the porous membranes neck-pore size distribution (NPSD) is the key element in the design and operation of all membrane separation processes. In this paper, a new approach is presented for reliable determination of NPSD of porous membranes using wet flow-state bubble point test data. For this purpose, a robust method based on the linear regularization theory is developed to extract NPSD of membranes from bubble point test data. The performance of the proposed method is tested using various experimental data. The predicted results clearly demonstrate that the proposed method can successfully predict the proper NPSD from a set of bubble point test data.

The purpose of this research was to study the effect of microwave power in pretreatment of fresh water hyacinth on biogas production. The variations of microwave power levels were 240; 400; 560 and 800 Watt (W). The variations of microwave heating time were 5; 7; and 9 min. The unpretreated fresh water hyacinth were used as control. The research results showed that the microwave pretreatment of fresh water hyacinth improved biogas production. Microwave pretreatment had a positive impact on anaerobic biodegradability of fresh water hyacinth. Almost all pretreated fresh water hyacinth produced biogas higher than unpretreated fresh water hyacinth. The maximum of biogas production from fresh water hyacinth was obtained at 560 W for 7 minof microwave pretreatment. In this condition, pretreated fresh water hyacinth resulted biogas production of 75.12 mililiter per gram of Total Solid (mL/g-TS). The unpretreated fresh water hyacinth produced biogas of 37.56 mL/(g-TS). The highest value of biogas production kinetic constants of biogas yield potential (A), the maximum biogas production rate (U) and the duration of lag phase (λ) were 78.23 mL/(g-TS); 2.2 mL/(g- TS.day); 4.60 days, recpectively.

The aim of this study was the use of fish waste hydrolysate (FWH) as a substrate for alkaline protease production and the enzyme production kinetics using isolated Bacillus sp. in a batch system. The results show that with the addition of FWH to the fermentation medium with a final concentration of 4% (optimal concentration), alkaline protease value reached a maximum value (89 U/ml), which is 63% higher than that of the control medium. Several kinetic models were evaluated; the combination of the Moser and Boulton kinetic model gave the best prediction. The results show that a good agreement between the model solutions and the experimental data for cell, substrate concentrations and enzyme activity was obtained, and this nonlinear mathematical model performed satisfactorily on biomass, substrate, and enzyme predictions. Also, the quadratic correlation coefficients obtained were higher than 0.98.Therefore, the kinetic model then may be used to simulate the fermentation variables.

Carbon dioxide (CO2) adsorption on unfunctionalized and amino-functionalized SBA-3 materials are investigated and compared in this study. The synthesized materials are characterized by various techniques such as X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET) method, Fourier transform infrared (FT-IR) and Scanning electron microscopy (SEM).The isotherms of these materials have been measured using volumetric method at 298 K up to 5 bar. The adsorption capacity of CO2 by mesoporous silica was enhanced through functionalization with amine groups. It is observed that the pentaethylene hexamine functionalized SBA-3 (SBA-3/PEHA) possessed a higher adsorption capacity towards CO2 than that of the other adsorbents.

The mechanistic force models were introduced in high accuracy force predictions for most applications. Experiment was made for the milling of titanium alloy by coated cemented carbide cutting tool. Based on the cutting force theory, test results and finite element method, we can get the expression of resultant cutting force accurately, which can be developed to a big cutting database. According to the analysis, the maximum deformation and effective stress showed an increasing trend for the machining with end-milling cutting tool. A reasonable set of milling parameters for the machining of titanium alloy by coated cemented carbide cutting tool were obtained by analyzing the cutting efficiency in relation to cutting force of the tools. It is expected that this study would provide a fundamental basis for the optimization of the cutting parameters for titanium alloy.

In this research for the purpose of the improvements, the effects of increasing the number of accordion tube layers of the Accordion metallic dampers (AMD) was studied. Damping behavior of AMD was investigated by the experimental, analytical and parametric studies. Experimental studies were conducted on single layer and two layer specimens under axial loading. Analytical studies have been carried out on series of single and multi-layer AMD models; then, those have been verified by the experimental results. Also, the effect of changing the geometrical parameters on the damping behavior with increasing the number of layer was evaluated and ideal geometric model was suggested. The results show increasing the number of layers influences the amount of dissipated energy that is due to a greater stable behavior.

In this study, the progressive collapse potential of seismically designed steel plate shear wall (SPSW) systems is investigated using the alternate path method, and their performances are compared with those of the conventional special moment frame (SMF) systems. Nonlinear static and dynamic analyses are conducted to follow the progressive collapse of the structures, and their ability of absorbing the destructive effects of member loss is investigated. The obtained results show that when a corner or a middle column in the first story of the SPSWs is removed, the rest of the structure is not able to provide an appropriate alternative path for redistributing the generated loads caused by member loss, and therefore the structure presents a high potential for progressive collapse. However, by changing the lateral load resisting system of these buildings with the SMFs, the progressive collapse resisting capacity of the buildings increases significantly.

This paper proposes an improved dark channel prior for removing haze from images. Dark channel prior is an effective method for removing haze. Dark channel is an image in the same size as the hazy image which is obtained by dividing the RGB images into windows and for each window, the minimum of each R, G and B channels are calculated. Then again the minimum of these three values is calculated and is replaced on all pixels in that window. For removing haze from images by dark channel prior, it is necessary to find transmission coefficient of haze and for this, airlight must be estimated. By having these factors, haze-free images can be restored. The dark channel prior method does not yield favorable results for some images, especially for those containing smooth regions. To overcome on this deficiency of the dark channel prior approach, the hazy image is initially segmented into smooth and non-smooth regions in this paper. Then for removing haze from smooth regions, the Gamma correction approach is used for contrast enhancement. Finally, for non-smooth regions, depending to the severity of haze, dark channel prior might be applied several times. The subjective and objective image quality assessments attest superiority of the proposed method compared to dark channel prior in haze removing.

In this paper, a model for MEMS capacitive microphone is presented for integrated circuits. The microphone has a diaphragm thickness of 1 μm, 0.5 × 0.5 mm2 dimension, and an air gap of 1.0 μm. Using the analytical and simulation results, the important features of MEMS capacitive microphone such as pull-in voltage and sensitivity are obtained 3.8V and 6.916 mV/Pa, respectively while there is no pressure on the diaphragm. The microphone also has a capacitance of 2.3 pF. Using the relation between the capacitance and pressure signal, a 3 ports model for the MEMS microphone is proposed. To bias the microphone, a 2.3 V DC and a 1 GΩ resistor is used. The voltage and current signal of the microphone is proportional to the applied pressure of the acoustic wave. A RC filter is added to circuit to eliminate the low band frequency (≤ 20 Hz) noises. The microphone shows good response to amplitude and frequency changes versus applied pressure signal.

Resource constrained project scheduling problem (RCPSP) is mainly investigated with the objective of either minimizing project makespan or maximizing project net present value. However, when material planning plays a key role in a project, the existing models cannot help determining material ordering plans to minimize material costs. In this paper, the RCPSP incorporated with the material ordering problem is first formulated into a NP-hard optimization model. Then, two hybridized meta heuristic algorithms are proposed to solve the integrated problem. In addition, statistical methods are employed to tune the parameters of both algorithms. Finally, computational results for a set of test problems taken from the project scheduling problem library (PSPLIB) are presented.

In this study, we consider the production environment of no-wait reentrant flow shop with the objective of minimizing makespan of the jobs. In a reentrant flow shop, at least one job should visit at least one of the machines more than once. In a no-wait flowshop scheduling problem, when the process of a specific job begins on the first machine, it should constantly be processed without waiting in the line of any machine until its processing is completed on the last one. Integration of the properties of both of these environments, which is applied in many industries such as robotic industries, is not investigated separately. First, we develop a mathematical model for the problem and then we present three methods to solve it. Therefore, we construct simulated annealing (SA), genetic algorithm (GA) and a bottleneck based heuristic (BB) algorithms that solve the problem. Finally, the efficiency of the proposed methods is numerically analyzed.

Material selection is one of the major challenges in the manufacturing systems. The improper selection may lead to fail in the production processes and result in customer dissatisfaction and cost inefficiency. Every material has different properties which should be considered as major criteria during the material selection. Selection criteria could be quantitative or qualitative. Quantifying the performance of qualitative criteria is an inevitable issue in the multi criteria decision making (MCDM) problems. In this paper, a common weight data envelopment analysis (CWDEA) model is applied for the material selection problem which accounts for both quantitative and qualitative criteria in an effective manner. Through a numerical example borrowed from the literature, it is shown that CWDEA is not able to produce a full ranking vector in this case. Accordingly, the problem is solved under different normalization methods and the resulting ranking vectors are then aggregated by the linear assignment method to generate a final full ranking vector.

In the last two decades, product recovery systems have received increasing attention due to several reasons such as new governmental regulations and economic advantages. One of the most important activities of these systems is to assign returned products to suitable reverse manufacturing alternatives. In this study, a new approach based on the Evidential Reasoning Approach (ERA) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) is proposed to deal with alternative (recovery system) selectionvia considering a comprehensive model in reverse logistics. This studycontributes to the literature with not only a novel reverse logistics decision modeling framework, but also a pragmatic data transformation technique which can comfort the combination of quantitative data and qualitative opinions using the evidential reasoning approach and TOPSIS. Finally, a case studyin the automotive industry is used to demonstrate the efficiency of the proposed method in selecting suitable reverse manufacturing alternatives. The company has to deal with the return products and make appropriate decision with respect to various criteria such cost, quality, and available resource. Uncertainty of returned products in terms of quantity, quality, and time complicates the decision making process. The obtained results indicate a good compliance with experts’ opinions and efficiency of the proposed hybrid decision making method (i.e., ER-TOPSIS) to offer a complete ranking.

Effect of different fillers on natural rubber compounds was investigated through curing, mechanical properties and morphology studies for improving mechanical performance of rubber articles. In this work, natural rubber blends with Silica as Single-filler compounds, and blends with Silica and Carbon black as Bi-filler compounds. Then, natural rubber blended with Silica, Carbon black, and Waste Tyre Rubber (WTR) particles as Tri-filler compounds were synthesized by a two - roll mill in specified operating conditions. In addition, natural rubber vulcanizate was prepared by using the same process. The different proportions were presented in Bi and Tri-filler compounds (10, 20, 25, 30, 40 phr) on CB and CB-WTR, respectively, whereas Silica was fixed at 20 phr. Curing characteristics showed that scorch time and optimum cure time significantly decreased with compared to natural rubber (NR) vulcanizate in all filler ranges. Whereas, minimum and maximum torque showed increased trend in all filler ranges. Cure rate index (CRI) also was presented and it showed significant good variation with the NR vulcanizate. Mechanical properties showed that tensile strength increased up to 30phr of CB in Bi-filler and it increased up to 10 phr with the addition of CB-WTR in Tri-filler compounds. Elongation at break decreased trend in Bi-filler and Tri-filler compounds, whereas maximum value was observed in single-filler compound. Hardness showed increased trend with addition of CB WTR in Tri-filler, and it increased up to 25phr in Bi filler compounds. Tensile Modulus increased up to 25phr in Tri-filler and it increased trend in Bi-filler compounds. Tear strength increased up to 2 phr and 25phr in Bi and Tri-fillers, respectively. Morphological study showed that better filler dispersion and good interfacial adhesion by the natural rubber matrix increased the tensile strength and opposite in tear strength. Among the rubber materials tested, Bi-filler compounds were found to be more suitable for improving the mechanical performance in the rubber applications.

Recently, increase in the cost of fossil fuels and taking into consideration the environmental effects of exploiting them, caused many researchers and governments to find some ways to make use of renewable energies more cost-effectively. Solar energy is a category of renewable energies which could be harvested via several technologies. One of the most practical methods is using parabolic troughs. In solar power plants, many parabolic troughs are set in parallel rows in order to concentrate the solar power onto a tube absorber. In designing and manufacturing parabolic troughs and their structures, it is essential to take into account the wind force. Any negligence in considering the wind force could be concluded in losing the accuracy and efficiency. In this article, the aerodynamic coefficients of parabolic solar troughs have been investigated using CFD methods. The variations of aerodynamic coefficients considering terrain effects, the angle of collectors and the gap between mirrors have been studied. Also, it will be demonstrated that in order to properly align trough collector in solar farms, it is essential to study the vortices shed created at the behind of parabolic troughs and its effects on collectors’ structures in the result of wind interaction. At the end and as an illustration, the drag and lift coefficients of collectors have been calculated in Yazd power plant.

This study investigated pollutants emissions of filling stations and the impact they cause to the air quality. Gas monitors were employed to identify the different pollutants present in the ambient air of the study areas. The results shows that the most prominent pollutants present in the ambient air are the volatile organic compounds followed by methane, then carbon monoxide. Measurements were taken at the controls at distances between 20 to 200m. The pollutants concentration recorded at the study areas shows that the level of pollutants exceeded the Federal Environmental Protection Agency (FEPA) air quality guidelines. There are few exceptions in pollutants like the particulate matter which was found to be at concentrations within the FEPA limits. Regression analysis of the pollutants at the controls shows that only the volatile organic compounds and methane are the only significant pollutants present in the ambient air, primarily because of the presence of the filling stations. These two pollutants show a strong negative correlation with distance from the study area. Specifically, the regression curve for the volatile organic compounds (VOCs) shows a nearly perfect curve with exponential functions as its regression model trend line, while that of methane has linear model trend line. Both VOCs and methane have a correlation coefficient (R) that is above 0.9 for the study areas. Hence, a conclusion was drawn from the findings that the primary pollutants to consider when building filling station are the VOCs and methane. Similarly, the minimum safe distance to site a filling station is 80m away from residential areas.

The purpose of this study is to investigate the performance and three-dimensional behavior of the flow in a mixed flow pump and the way cavitation phenomenon is affected by different parameters such as fluid temperature, pump speed and flow rate. Computational fluid dynamic software FLUENT was utilized to simulate the whole flow field of the pump. RNG k-ε model combined with standard wall functions is chosen to deal with the turbulent feature of the problem. The studied pump has four blades mounted on a conical hub which form the rotary part and nine static vanes afterward as the stationary part. So the rotor-stator interaction was treated with a Multiple Reference Frame (MRF) technique. The flow rates and pump speed were the key parameters for investigation. While the flow rates variation and the pump revolution change cavitation occurrence widely, the temperature variations caused by weather changes during a year has little effect on cavitation. The cavitation region which is defined by the saturation pressure in that temperature was shown for various cases on a blade.