International Journal of Engineering
Volume:22 Issue: 1, Apr 2009

The effect of Solid State Fermentation (SSF) on Chitosan production by A. niger was investigated. A. niger BBRC 20004 from Biochemical and Bioenvironmental Research Centre of Sharif University of Technology (Tehran, Iran) was grown on corn residue. Chitosan was extracted from the fungal mycelia using hot alkaline and acid treatment. A. niger was incubated for 12 days on corn residue with moisture content of 35 % and 1.12 % of nitrogen. The Chitosan was obtained and 10.9 g/kg of Urea dry residue was added in various amounts to the medium in order to evaluate the effect of the nitrogen concentration in the production of Chitosan. The highest amount of Chitosan obtained by 6.5 g of urea after 12 days of incubation was 16.15 g/kg.

In this paper, a reinforced concrete(RC) bridge built in an interchange, in the city of Kerman (a city located in south of Iran) is examined by the Structural Health Monitoring (SHM) system. During the construction of this bridge such as; the main beams, slab, and retaining walls, some Electrical Strain Gauges were mounted on the main reinforcements at different locations within the body of this bridge. After the completion, the bridge was loaded with different load arrangements and the strain readings were collected by a powerful Data Logger for field analysis. The considered loading cases were, 1) twelve trucks carrying sand with an average weight of 28t each, the trucks were lined up in regular pattern and also in a certain preprogrammed arrangement, 2) the daily traffic loads, the bridge behavior was examined and data were recorded during the peak points of the daily traffic, 3) the bridge weight, to find this, the traffic was not allowed to pass over the bridge for a few days, in order to record the bridges’ behavior under its own weight. All loadings and unloading cases were recorded for field analysis. The theoretical analysis of the bridge was performed according to the classical method. To achieve the best findings, also the Finite Element program- ANSYS -was used, for all loading cases. This program is able to model concrete reinforcement by its own library elements. Concrete could also be studied as a nonlinear element. Finally, the field analysis and theoretical findings were compared and the results are presented.

Flexible structures (such as long-span suspension bridges which undergo wind or earthquake excitations) exhibit complex dynamic behavior. Due to high cost of strengthening such structures, as well as the technological advances in recent years, much attention has been given to using innovative means of enhancing structural functionality and safety against natural hazards. Among the methods used to mitigate the excessive vibration of structures, the energy absorber systems are more promising. The present paper discusses parametric studies of the TMD system to find the optimal values of its parameters, to suppress the vertical responses of suspension bridges subjected to earthquakes’ vertical accelerations. Thomas Suspension Bridge located in Los Angles, U.S.A., is chosen as a case study, and the vertical acceleration records of 18 major worldwide earthquakes are used in numerical studies. The analysis is performed in time domain. The results of the numerical studies show that the proposed system is capable of reducing the maximum vertical displacement of the bridge to a considerably low value

Extracting and tracking active objects are two major issues in surveillance and monitoring applications such as nuclear reactors, mine security, and traffic controllers. In this paper, a block-based similarity algorithm is proposed in order to detect and track objects in the successive frames. We define similarity and cost functions based on the features of the blocks, leading to less computational complexity of the algorithm. Therefore, this method is suitable for real-time tracking. According to the experimental results, this method has a good performance and works well for occluded objects, cluttered environments and noisy sequences.

This paper uses a method for shape reconstruction of a 2-D homogeneous object with arbitrary geometry and known electrical properties. In this method, the object is illuminated by a Gaussian pulse, modulated with sinusoidal carrier plane wave and the time domains’ footprint signal due to object presence is used for the shape reconstruction. A nonlinear feedback loop is used to minimize the difference between the measured and calculated signals obtained, by using FDTD at consecutive time windows. The layers of the objects’ shape are reconstructed while the incident plane wave moves over the objects’ surface. Based on the above method, some results are presented for an object with typical geometry. The effect of modulating carrier frequency was investigated for conductivity and dielectric objects.

Due to the properties of tumor cell, the tumor establishes itself in the organ and grows there, so there is a competition between the tumor cells and host cell (normal cells) for nutrients. Evidences show that high dietary phosphorus increases the rate of protein synthesis and thus the cell number. So, other than oxygen, sulfur, the important element that both tumor cells and normal cells need is phosphorus. Hence, the proliferation and growth rate of both tumor cells and healthy cells depends on the content of phosphorus available to them. So, the mathematical model with time delay is prepared in which the growth rate of tumor cells and normal cells are function of phosphorus with their restrictions. And by applying suitable implications on the model and studying the simulations we will come to know its effects on tumor growth.

Many systems can be modeled with hard and various size spheres, therefore packing and geometrical structures of such sets are of great importance. In this paper, rigid spherical particles distributed in different sizes are randomly packed in confined spaces, using a parallel algorithm. Mersenne Twister algorithm was used to generate pseudorandom numbers for initial coordination of particles. Distribution of packing densities and reproducibility of particles packing factor, with log-normal size distribution and also mono-sized particles have been compared. In addition, the effects of container size on regional particle packing density, the effect of wall on packing density and symmetry of packed structure have been investigated. The results confirm that particles in log-normal size distribution have higher packing densities, but the obtained results have less reproducibility than mono-sized particles. Also, in comparison, particles in log-normal size distribution have uniform density and regions with higher local density.

Desiccant wheels are widely used in buildings to control humidity and reduce energy consumption. A model is presented based on transient coupled heat and mass transfer, to model, design and analyze the effects of geometrical characteristics of a honeycombed rotary desiccant wheel and its performance. Governing equations are solved numerically using finite volume method and the model is validated using experimental measurements. It is shown that increasing desiccant wheel length will increase the latent and sensible effectiveness. Also, there is an optimum value for the ratio of dehumidification to regeneration area, which maximizes the latent heat effectiveness. Also the optimum hydraulic diameters of desiccant wheel channels depend on air mass flow rate.

It is a well known fact that, dual fuel engines at part loads, inevitably suffer lower thermal efficiency, higher carbon monoxide and unburned fuel emission. The work in this paper is to investigate combustion characteristics of a dual fuel (diesel-gas) engine at part loads, using a single zone combustion model with detailed chemical kinetics for combustion of natural gas fuel. The authors developed software in which the pilot fuel is considered as a subsidiary zone, and a heat source which is derived from two superposed Wiebe’s combustion functions is to account for its contribution to ignite gaseous fuel and the remainder of total released energy. Chemical kinetics mechanism consists of 112 reactions with 34 species. This quasi-two zone combustion model is able to establish the development of the combustion process with time, and the associated important operating parameters such as; pressure, temperature, heat release rate (H.R.R) and species concentration. Therefore this work is an attempt to investigate the combustion phenomenon at part loads, using techniques such as increasing the quantity of pilot fuel and exhaust gas recirculation (EGR) to solve the above mentioned problems. By employing these techniques, it is found that, both these methods have positive effect on the performance and emission parameters, except for NOx of dual fuel engines at part loads. Predicted values show good agreement with corresponding experimental values in a special engine with operating condition of (1/4 load, 1400 rpm). Implications will be discussed in details.

The objective of this paper is to investigate the effect of fuel injection pressure on power performance and fuel consumption of diesel engine. In a diesel engine, fuel injection pressure is an important aspect of the engines’ power performance in order to obtain combustion treatment. The experiments in this paper are performed on a four-cylinder two-stroke direct injection diesel engine. The diesel engine power performance and fuel consumption values are investigated based on load variation, engine speed and fuel injection pressure. The power performance values such as; indicated pressure, indicated horse power, shaft horse power, brake horse power and break mean effective pressure, is investigated both for various engine speed-fixed load and fixed engine speed-various loads. The fuel injection pressure changed from 180 to 220 bar. According to the experiment results, the best pressure injection performance has been obtained at 220 bar, specific fuel consumption has been obtained at 200 bar for fixed load-various speed and at 180 bar for various loads-fixed speed. The results of the experiment are shown as graphs in this paper. The experiment results show, that the increasing injection pressures increases the engine power and fuel consumption.

In this paper we examine the effect of mild stenosis on blood flow, in an irregular axisymmetric artery with oscillating pressure gradient. The Herschel-Bulkley fluid model has been utilized for this study. The combined influence of an asymmetric shape and surface irregularities of constriction has been explored in this computational study. An extensive quantitative analysis has been performed for narrowing of vessels through numerical computations on the flow velocity, plug flow rate and the apparent fluidity. The graphical representations have been made to validate the analytical findings with a view of its applicability to stenotic diseases. Velocity profiles, plug flow rate, and apparent fluidity along the radius of the obstructed tube are determined to give the flow characteristics, for diagnostic point of view. The effects of viscosity on the flow field are examined numerically and are shown graphically.