International Journal of Engineering
Volume:25 Issue: 3, Aug 2012

Among enzymes, lipases have been widely investigated because of the numerous industrial applications. In this study, optimization of lipase production by Aspergillus niger in solid state fermentation from rice bran as solid substrate was investigated. The optimal conditions with the aid of central composite design (CCD) under response surface methodology (RSM) were obtained. In the analysis of 20 experimental runs, effects of three variables such as olive oil concentration, glucose concentration and humidity ratio on lipase activity were evaluated. The interaction between lipase activity and independent paired parameters were illustrated by three-dimensional diagrams while other factors were set at zero level. The optimum values of oil concentration, glucose concentration and humidity ratio were 1.78, 2.54 and 1.95 % (g/gdss), respectively. Also, the effect of temperature and pH on the relative lipase activity in enzyme reaction was evaluated. The lipase produced was highly active at 30.3°C and pH value of 6.87.

Accurate determination of the pull-in, or the collapse voltage is critical in the design process. In this paper an analytical method is presented that provides a more accurate determination of the pull-in voltage for MEMS capacitive devices with clamped square diaphragm. The method incorporates both the linearized modle of the electrostatic force and the nonlinear deflection model of a clamped square diaphragm. The capacitor structure has been designed using a low stress doped poly silicon diaphragm with a proposed thickness of 0.8 μm and an area of 2.4 mm2, an air gap of 3.0 μm, and a 1.0 μm thick back plate. The value of pull-in voltage calculated using equation is about 6.85V and the finite element analysis (FEA) results show that the pull-in occurs at 6.75V. The resulting pull-in voltage and deflection profile of the diaphragm are in close agreement with finite element analysis results.

In this paper a new design of MEMS capacitive fingerprint sensors is presented. The capacitive sensor is made of two parallel plates with air gap. In these sensors, the capacitance changes is very important factor. It is caused by deformation of the upper electrode of sensor. In this study with making slots in upper electrode, using T-shaped protrusion on diaphragm in order to concentrate the force from finger ridges, making holes in lower electrode to reduce the air damping and using low stress material for diaphragm, we have been succeeded to design a novel MEMS fingerprint sensor with high sensitivity compared with the previous one. In the present research, simulations were carried out using FEA method.

Most existing power converters and industrial motor drive systems draw non-sinusoidal currents from the supply. Non-sinusoidal currents contained harm harmonics disturb the power supply which it causes serious concern for reliability. Other equipments that use the same power supply are adversely affected. This paper suggests the operation and performance of a new modified AC/DC converter that allows bi-directional power flow. It also provides improved power factor and reduces harmonic magnitude and disturbance to the supply by system. The bi-directional feature allows recovery of regenerative energy of loads, back to the power supply and the converters. The proposed converter has high potential for industrial applications, such as electronically controlled traction system, lifts and generally industrial motor drive systems which can increase overall efficiency and reliability.

Biodegradation of phenol in the presence of glucose as a supplementary substrate was investigated with mixed microbial consortium isolated from waste effluent of coke-steel factory. Batch experiments were carried out at room temperature and pH value of 7. Initial phenol and glucose concentrations were in the range of 25-1000 mg/l and 500-3000 mg/l, respectively. In a dual substrates system the concentration of supplementary source (glucose) was kept constant. It was obvious to find out that glucose as a simple carbon source was initially utilized in the presence of phenol. The rate of phenol degradation started once glucose concentration was significantly depleted. Phenol was known to be an inhibitory substrate, thus Haldane/Andrews kinetic model was applied to evaluate the growth kinetic parameters. The kinetic parameters, mm, Ks and Ki were 0.01 1/h, 27.04 and 127.55 mg/l, respectively. The specific growth rate of the culture in dual substrates system was expressed by SKIP model (R2> 0.951). The values of interaction parameters showed uncompetitive partially inhibition at high phenol concentration.

The energy conservation potential of the heat pipe based heat exchangers (HPHXs) was studied in this research. To this end, a typical climate chamber as the representative of an air conditioning system was established. The performance characteristic of a typical eight-row HPHX was obtained based on the one week operation (168 h) to determine the performance characteristic curves. The coil face velocity and inside temperature were set at 2 and 24, respectively. Then, the relevant empirical performance equations were used to predict the energy conservation of the HPHX for the years of 2000, 2020, and 2050. The predictions showed that total amounts of 6,794 kWh, 11,278 kWh, and 14,132 kWh energy could be recovered by the fabricated HPHX in the years of 2000, 2020, and 2050, respectively.

In this study, the effect off adding SiO2 nanoparticles on the viscosity of base fluid is investigated experimentally. Base fluids are chosen among common heat transfer fluids such as ethylene glycol, transformer oil and water. In addition different volume percentages of ethylene glycol in water are used as ethylene glycol-water solution. In every base fluid different volume fractions of SiO2 nanoparticles is added. It is shown that the viscosity of solution enhance by adding nanoparticles. The effect of cooling and heating process on the viscosity of nanofluid is also discussed. The presented data show that as the temperature increases the viscosity of base fluid and nanofluid decrease. It is also revealed that there are very little differences between the viscosity of nanofluid in a specific temperature at cooling and heating cycles. According to the experimental results new correlations for predicting the viscosity of nanofluids is presented. These correlations relate the viscosity of nanofluid to the particle volume fraction and temperature.

The paper deals with the performance optimization for skim milk powder unit of a dairy plant at National Dairy Research Institute (N. D. R. I.), Karnal using Genetic Algorithm (G. A.). The skim milk powder unit comprises of six subsystems working in series. The failure and repair rates of the subsystems are taken from maintenance history sheets, which follow the exponential distribution. The mathematical formulation is carried out using probabilistic approach and the Markov birth – death process is used to develop the difference differential equations. The steady state availability expression has been derived using normalizing conditions. The optimal values of failure/repair rates of each subsystem of the skim milk powder unit have been evaluated using Matlab 7.1 G. A. tool. The steady state availability obtained from Markov analysis is also compared with the optimal availability calculated through G. A. tool. So, the findings of the present paper will be highly useful to the plant management for developing proper maintenance strategies which can be implemented in order to enhance system performance.

In this paper, the effect of anisotropy on the free vibration of laminated rectangular plate supporting a localized patch mass is investigated. The two variable refined plate theory is applied to define the third order displacement field of a composite rectangular plate. The plate is considered to have simply supported boundaries. The equations of motion for rectangular plate are obtained by calculus of variation. Parametric study of non-dimensional natural frequencies is carried out and the influences of geometrical parameters such as aspect ratio of the plate, size and location of the patch mass on these frequencies are also studied. First, the results obtained are compared with those reported using several plate theories. In the next step, the effect of anisotropy on free vibration of plates for different types of lamination are studied. The numerical results are found to be in a very good agreement with well known published papers for the case of vibration analysis of loaded and unloaded plates.

Recent studies in multi-agent systems are paying increasingly more attention to the paradigm of designing intelligent agents with human inspired concepts. One of the main cognitive concepts driving the core of many recent approaches in multi agent systems is shared mental models. In this paper, we propose an architecture for sharing mental models based on a new concept called semantic movement. This architecture has been inspired by a variety of mental models in humans and supports agents working in different simultaneous contexts and it uses semantic movement as a conflict resolution mechanism. Semantic movement is a kind of transition from the present mental states to some new states in order to resolve harming conflicts between mental models of participants. We formalized the semantic movement process in order to use it in our proposed architecture. Our test bed to evaluate this architecture is a set of complex scenarios which are likely impossible to be solved by individual agents without sharing. Our architecture exhibits better performance than other alternative methods that have sharing capabilities. We believe that the proposed architecture would be able to provide agents with the ability of generating more consistent behaviors between agents. Moreover, this architecture can become a suitable platform for the negotiation of self interested agents.