International Journal of Engineering
Volume:29 Issue: 10, Oct 2016

The kinetics and isotherm studies of the immobilized lipase and the mechanism of immobilization on chitosan beads and activated chitosan beads with glutaraldehyde were investigated. The validity of experimental data fitted to Langmuir, Freundlich, Hill, Sips, Temkin, Redlich-Paterson and Dubinin-Radushkevich isotherm models for both immobilization methods were examined. The isotherm models were compatible and confirmed immobilization techniques. In comparing of the isotherm models, the best fit of experimental data was obtained by Langmuir isotherm model for chitosan beads; which is consistent with the heterogeneous behavior of the adsorption sites on the chitosan structure. However, Freundlich isotherm model have corresponded immobilization of lipase on chitosan beads activated by glutaraldehyde so that it can reveal the multilayer adsorption. Also, pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion were studied by experimental results in different concentration of lipase. Pseudo-first order kinetic model were described immobilization of lipase on chitosan beads and corresponds to physical adsorption of enzyme on the carrier. In fact, activated beads have followed pseudo-second order kinetic model which is indicated that chemical adsorption of enzyme occurred in the carrier. In addition, intra-particle diffusion equation for chitosan beads and activated chitosan beads is properly fitted by experimental data with high regression coefficient. In addition, FESEM analysis of chitosan beads and activated chitosan beads demonstrated that glutaraldehyde has significantly enhanced the surface porosity of chitosan beads. Maximum capacity of immobilization was enhanced by 2 folds, when the porosity of chitosan beads were improved by glutaraldehyde. These results were confirmed with adsorption isotherm models and kinetic equations.

Transformer insulating oil nanofluid is made to improve dielectric and thermal properties of oil by employing nanoparticles with proper properties. In the current work, nanofluids based on transformer mineral oil were prepared by three procedures using diamond nanoparticles with high thermal conductivity, as well as high dielectric properties. It was tried to consider the impacts of use of surfactants and ball milling process in the preparation procedures. The effects of a variety of stabilizers (the amount and type) and also the ultrasonic time on diamond nanoparticles’ stability in the oil were investigated and optimized experimentally. Using the optimized nanofluids, thermal conductivity and viscosity of the oil nanofluids were compared and discussed. In addition, the consistency of the thermal conductivity results with Maxwell and also Hamilton and Crosser theoretical models was examined. It was revealed that, the nanofluid preparation procedure, temperature and nanoparticles’ concentration had effects on thermal conductivity of the transformer oil nanofluid, while the presence of nanoparticles had a slight impact on the viscosity of the fluid. Also the effect of presence of diamond nanoparticles on the electrical properties of transformer oil was studied. Based on the experimental results, adding diamond nanoparticles could lead to an increase in the transformer oil breakdown voltage, while it had nearly no effect on dielectric loss at low concentrations.

Amine-modified mesoporous Santa Barbara Amorphous (SBA)-15 adsorbent has been prepared by impregnation method using tetraethylenepentamine. The samples of this modified SBA-15 have been characterized by small angle X-ray scattering (SAXS), Scanning electron microscopy (SEM), Nitrogen adsorption-desorption isotherm and FT-IR. The adsorption capacity of CO2 on unmodified and modified samples were measured at high pressure (up to 20 bar) and room temperature and were 2.69, 4.02 and 3.62 mmol CO2/g for SBA-15, TEPA (55%)-SBA-15 and TEPA (65%)-SBA-15, respectively. The increment in the CO2 adsorption capacity of amine modified mesoporous material (TEPA (55%)-SBA-15) is attributed to the increased amine mass interaction with CO2. Further increase of amine content clogs the pores of the sorbent which results in slight reduction of CO2 adsorption in TEPA (65%)-SBA-15).

Fungal volatile organic compounds (VOCs) have the potential of being used as biocontrol agents for biotechnological applications in agriculture, industry and medicine. In this research, different VOCs from secondary metabolites of biocontrol fungus Trichoderma virens (6011) were separated using n-hexane, n-butanol and methanol solvents and identified by gas chromatography–mass spectrometry (GC-MS) device. According to mass spectra library searching, more than 200 volatile compounds (with spectral match factor higher than 80%) such as alkanes, alkenes, alcohols, organic acids, aromatic compounds, aldehyde, etheric, esteric, phenolic, kenotic derivatives and, sulfur and nitrogen compounds, have been detected. Some of the VOCs such as dibutyl phthalate (DBP) had antifungal activity. The antifungal effect of DBP as a case study was checked and confirmed in in-vitro
conditions. DBP as a bioactive compound was separated from secondary metabolites using Molecularly Imprinted Polymers (MIPs) as a solid sorbent. Two kinds of the MIPs were synthesized via bulk polymerization and precipitation polymerization. Nanoporous MIPs for DBP, with binding capacity ca.462 mg.g-1 and the specific surface area 479m2.g-1 were synthesized via bulk polymerization method while the synthesized MIPs via precipitation technique had the binding capacity ca.830 mg.g-1 with specific surface area 690 m2.g-1. The synthesized MIPs were evaluated by scan electron microscopy (SEM) device and Brunner Emmett-Teller (BET) analysis. Results showed that, the MIPs nanotechnology can be suggested as a suitable alternative method for separation of the chemical toxins. This study introduces a simple method under laboratory conditions to separate the bioactive compounds from fungal secondary metabolites.

The newly built residential house basically had undergone a period where any defects toward the house will be rectified by the particular developer. Defect Liability Period (DLP) which is commenced from the day of Vacant Possession (VP) by house owners generally in effect between eighteen (18) months and twenty-four (24) months. During DLP, new house owner has the right to issue any complaints regarding the quality of the said building. Unfortunately, complaints were believed to widespread in the recent era where profitability is the main concern to most of the developers. Since the quality of the finished product is of minor consideration, added with less knowledgeable new house owners on issues of house defect, the situation is going from bad to almost heedless. To add salt to the wound, scarcity on research and dissemination of knowledge were deemed to shut the issue until almost to no existence. Therefore, the research is taking a leap by focusing on sense perceptions of house components that received recurring complaints and providing corresponding practical ways to check for defects on behalf of new house owners. A mixed method of methodology has been imposed, starting with literature analysis, questionnaire survey, and structured interview, respectively. Questionnaire surveys were conducted using online distribution towards developers and contractors within southern states of Malaysia, namely; Johor, Melaka, and Negeri Sembilan. Meanwhile, the latter method was accomplished by interviewing several senior construction practitioners. In order to ease the analysis processes, SPSS, and NVivo were used as the main software. The findings suggest that, in terms of sense perceptions, house components consist of several important parts such as roof, walls, and floors, along with their sub-components. However, not all components received similar trend of complaints from the house buyers. Interestingly, most of the senior construction practitioners proposed several unique and unaware practical ways for defect identification, such as by using torch light, water, and other simple testing methods. This research contributes in that it embarks on application-based software as knowledge management and distribution effort, which is anchored on Android by Google Incorporation.

At present, reducing subgrade settlement of soft soil foundation is a key problem in high-speed railway construction. Pile-slab structure is a widely-utilized form of foundation structure to reduce the subgrade settlement in China. In order to save the engineering cost for high-speed railway construction in developing countries, the author developed a pile-slab structure and named it as the new Cement Fly-ash Grave (CFG) pile-slab structure. This work analyzed the settlement controlling effect of new CFG pile-slab structure and summarized two calculation methods on its subgrade settlement which are further formulated into an analytic method. Three methods were used to calculate the subgrade settlement of CFG pile-slab structure for a soft soil foundation in Chinese Shanghai-chengdu high-speed railway. The research showed that: (1) The settlement controlling effect of CFG pile-slab structure can satisfy the requirement of high-speed railway construction. (2) The new analytic method is proved to be more accurate and can reflect the mechanism of load transferring． Furthermore， the new analytic method can provide theoretical guidance for engineering designs and constructions of the CFG pile-slab structure．

The maximum power point tracking (MPPT) control in a Photovoltaic system is the key control technology, however present controllers have the disadvantages of long development cycle, high cost and complex verification, and there are some disadvantages carrying out totally physical simulation or totally digital simulation of different control algorithms. This paper carried out design of hardware controller by researching different kinds of MPPT algorithms together with the improved MPPT algorithm, then digital-analog hybrid real-time simulation was carried out based on the digital main circuit using RT-LAB developed by Opal-RT company. Effectiveness and superiority of the improved MPPT algorithm were verified in comparison with control effects of the improved MPPT algorithm and control effects of traditional MPPT algorithms.

This paper presents a novel Radio Frequency-Micro Electromechanical System (RF-MEMS) fixed-fixed switch for very fast switching. Using the obtained equations, the switching time depends on the stiffness and effective mass of the switch beam so that the switching time will be decreased by higher stiffness (spring constant) and lower effective mass. In the new design, the suspension bridge is a three-layer beam so that the middle layer is aluminum and outer layers are alumina. The reduced dimensions and three layers of beam cause to increase stiffness and reduce the mass of the beam. This led to increase the resonant frequency and as a result, the switching time is reduced. The results show that, the switching time is 127 ns for the applied voltage of 27V and also the pull-in voltage is 18V. The return loss is 12 dB at the frequency of 60 GHz that is desirable and the achieved results is better than previous works. Therefore, this switch is suitable for high frequency applications.

In this paper, a general framework for image contrast enhancement algorithm based on an optimization problem is presented. Through this optimization, the intensities can be better distributed. The algorithm is based on the facts that the histogram of the enhanced image is close to the input image histogram and uniform distribution, simultaneously. Based on this fact, we obtain a closed form optimal solution for the histogram of the enhanced image. Experimental results in a wide range of images demonstrate the high-performance of the proposed method.

This paper presents a nonlinear controller for a Distribution Static Compensator (DSTATCOM) of a microgrid incorporating the Distributed Generation (DG) units. The nonlinear control has been designed based on partial feedback linearization theory and Proportional-Integral-Derivative (PID) controllers try to adjust the voltage and trace the output. This paper has proposed a combination of a fuzzy system and Galaxy-based Search Algorithm (GbSA) to optimize the parameters of the PID controllers. The results confirm that the characteristics of the response of the proposed controller (i.e. settling and rise times, the maximum overshoot and the steady-state error of the voltage step response of the DSTATCOM) is significantly improved by finding a high-quality solution. The proposed hybrid tuning method for the Partial Feedback Linearizing (PFL) controller concluded a better DC voltage regulation for the capacitor within the DSTATCOM. Furthermore, in the event of fault the proposed controller tuned by the fuzzy-GbSA method has shown a better performance in comparison with the conventional controller or controllers tuned by Genetic Algorithm (GA) or Particle Swarm Optimization (PSO) methods on both fault duration and after clearing times.

This paper presents a novel reliable hierarchical location-allocation model where facilities are subject to the risk of disruptions. Based on the relationship between various levels of system, a multi-level multi-flow hierarchy is considered. The heterogeneous probabilistic disruptions are investigated in which the constructed facilities have different site-dependent and independent failure rates. In the occurrence of facility disruptions, to achieve system reliability, the mitigation operation is considered in such a way as to reassign the demand nodes to other operational facilities that can provide services. The problem is modeled from both cost and risk perspectives such that the fixed installation cost as well as the expected costs in normal disruption-free and disruptive conditions are minimized. A Benders decomposition algorithm is developed which seeks to find exact solution of the proposed model. Two efficient accelerating techniques including valid inequalities and knapsack inequalities are also proposed to expedite the convergence of solution procedure. The numerical results illustrate the applicability of the proposed model as well as the efficiency of the designed solution procedure.

Inventory routing problems arise as simultaneous decisions in inventory and routing optimization. In the present study, vendor managed inventory is proposed as a collaborative model for reverse supply chains and the optimization problem is modeled in terms of an inventory routing problem. The studied reverse supply chains include several return generators and recovery centers and one collection center. Since the mathematical model is an NP-hard one, finding the exact solution is time consuming and complex. A hybrid heuristic model combining dynamic programming, ant colony optimization and tabu search has been proposed to solve the problem. To confirm the performance of proposed model, solutions are compared with three previous researches. The comparison reveals that the method can significantly decrease costs and solution times. To determine the ant colony parameters, four factors and three levels are selected and the optimized values of parameters are defined by design of experiments.

In the present investigation, we propose a numerical simulation of two plane parallel turbulent jets. Several turbulence models were tested in the present work: the standard k - Ɛ, the standard k - ω and the RSM models. A parametric study was also presented to pick up the nozzle spacing and the velocity ratio effect on the merge and combined point’s axial and transverse positions. An investigation on the velocity ratio effect on the strong and weak jet spreading was also performed. It has been shown through the present investigation that the velocity ratio significantly affects the position of merge and combined points. Correlations between the merge and combined points position with respect to the nozzle spacing and the velocity ratio are also provided. Results show that the increase in the velocity ratio moves the merge and combined points further upstream in the longitudinal direction while deflecting toward the strong jet in the transverse direction. The present numerical investigation allows us to conclude that when increasing the velocity ratio, the weak jet exercises some braking on the strong jet which decelerates its spread. On the other hand, the strong jet produces some acceleration on the weak jet, which enhances its spread.

The characteristic study of heat dissipation rate is done with by numerically evaluating the radial distribution of Nusselt magnitudes over a flat plate. These profiles are reported for various injection and geometric parameters in the present research. A very contagious look towards these profiles shows the occurrence of secondary and localized rise. However these local rises are observed provided the Nusselt profiles are accurately predicted. To achieve this, the present research takes an effort in numerically simulating a computational domain, analogous to actual experimental conditions. The computational simulations at lower nozzle-target spacing and higher impinging velocity revels the occurrence of secondary rise in Nusselt profiles. A very less light is observed in determining the exact cause and the intervening range for the occurrence of such peaks in the profiles. Looking into this, the current research focuses on the determination of the critical constant and its magnitude within which these peaks exist in the profile. The non-dimensional constant representing the critical magnitude is defined as a ratio of diameter based Reynolds number with nozzle - target spacing (Z/d). A very judicious look towards the velocity contour conveys the occurrence of turbulence flow in near wall region to be responsible for the secondary rise in heat transfer rate.

Ductile fracture process usually occurs due to the accumulation, growth, and combination of defects or cracks of material and is called ductile damage. Failure in materials can be predicted, using damage mechanics and damage criteria. On the other hand, most of the materials depended on the manufacturing process, are formed in warm or hot conditions so that; the temperature affects on the probable damage initiation. In this study first, a number of conventional hot forming processes of aluminum alloys such as forming process by tail gas, hydroforming, and blank forming with punch are simulated by finite element method and employing different damage criteria, and damage initiation in them is predicted. Then, the obtained numerical results are compared with the experimental results achieved from empirical experiments and validated. Finally, the damage criteria are classified based on the accuracy of the predicted results and the most appropriate criteria for predicting the damage in hot forming processes are introduced. It is concluded that Brozzo and Ayada damage criteria are the most proper criteria for predicting the damage initiation in the hot forming processes.

Experimental investigations have been done to find out the heat transfer characteristics and friction factor of water based Al2O3 nanofluids as a coolant in brazed plate heat exchangers. In most of the studies plate heat exchangers are used in horizontal or vertical conditions. The base plate of the plate heat exchanger was kept inclined at (0o, 30o, 60o, 90o). The experimentation has been carried out with two different concentration of the nanofluids (0.1 and 0.2 v/v%). It was observed that the heat transfer characteristics improves with an increase in Reynolds number. It has been shown that nanofluids in a plate heat exchanger have a maximum of 34% heat transfer rate over the base fluid. It has been observed that from horizontal to vertical orientation heat transfer rate decreases with increase in Reynolds number. The average heat transfer coefficient has been found to reduce by 10 15% when the angle of inclination of base plate of heat exchanger i from horizontal is 30o.

This study investigated the effects of deposition techniques on the microstructural and tribological properties of Ti/TiN/TiCN/TiAlN multilayer coatings onto a Custom 450 steel substrate. The coatings were produced using cathodic arc physical vapor deposition (CAPVD) and plasma-assisted chemical vapor deposition (PACVD). The microstructure of the coatings was evaluated using (SEM), and phase formation was analyzed by (XRD). The mechanical properties of the coatings were examined by nano-indentation testing machine. Erosion behavior was studied using an erosion tester and the electrochemical behavior of the deposited films in 3.5% (wt) NaCl solution was investigated using potentiodynamic polarization. XRD analysis indicated that TiN, TiCN, and TiAlN featured different chemical compositions in each coating. Nano-indentation showed that the hardness of the CAPVD and PACVD coating was 23.35 and 12.92 GPa, respectively. The coefficient of friction was 0.22 for the CAPVD and 0.17 for the PACVD coatings. Erosion testing was conducted using two abrasive powders at impact angles of 30° and 90°. The results showed that erosion rate at an impingement angle of 90° was greater than that of 30° and the CAPVD coating showed better performance. The potentiodynamic polarization curves showed that the CAPVD coating provided better corrosion resistance than the PACVD coating.

The two-fluid flow is produced by the combined effects of electroosmotic force in a conducting liquid and pressure gradient force in a non-conducting liquid. The Poisson-Boltzmann and Navier Stokes equations are solved analytically; and the effects of governing parameters are examined. Poiseuille number increases with increasing the parameters involved. In the absence of pressure gradient, the two fluids demonstrate plug-like velocity profiles. The results reveal that the two-fluid electroosmotic pumping flow rate is feasible for a relatively small interface zeta potential; or large wall zeta potential and electrokinetic radius. For particular values of the governing parameters, the flow rate approaches a specific value as the electrokinetic radius tends to infinity. A back flow (a negative value of the resultant flow rate) occurs for sufficiently small values of the wall zeta potential or sufficiently large values of the interface zeta potential (even in the case of pressure-assisted flow). Zero value flow rates may also be attained.