International Journal of Engineering
Volume:19 Issue: 1, Dec 2006

An up-flow anaerobic sludge fixed film (UASFF) bioreactor was used to treat the pretreated palm oil mill effluent (POME). In physical pretreatment, POME was pre-settled for 2 h and the supernatant was fed into the reactor. In chemical pretreatment, optimum dosages of cationic and anionic polymers were used. Experiments of pretreated POME digestion were conducted based on a central composite face-centered design (CCFD) with two independent operating variables, feed flow rate (QF) and up-flow velocity (Vup). The operating variables were varied to cover a wide range of organic loading rate (OLR) from 3.8 to 29 g COD/l.d. A stable TCOD removal efficiency of 83.5% was achieved at the highest QF (3.31 l/d, corresponding to OLR of 26 g COD/l.d) for pre-settled POME whereas only 62.2% TCOD removal was achieved with chemically pretreated POME at QF of 7.63 l/d (corresponding to OLR of 29 g COD/l.d) and that too was coupled with process instability. At comparable OLRs i.e. 16.95 g COD/l.d (QF=2.16 l/d) for pre-settled POME and 16.42 g COD/l.d (QF=4.32 l/d) for chemically pretreated POME, the VFA concentrations for the two cases were also similar.

This paper presents a new approach for large-deflection analysis of truss structures employing the Dynamic Relaxation method (DR). The typical formulation for DR has been established utilizing the finite difference technique which is categorized as an explicit method. The special characteristic of the explicit method is its simple algebraic relationships in comparison with complicated matrix operations in a finite element method. In this paper, a new procedure is developed using the Taylor series in order to reduce the number of iterations needed for convergence and consequently time and effort. Moreover, the validity of the proposed technique has been demonstrated by solving some truss structures with nonlinear behavior.

In the present work, the motion of metallic and plastic particles of 5 mm diameter falling in a quiescent fluid is investigated experimentally. The goal of this investigation is to examine the effect of history force acting on a particle in a range of Reynolds numbers between 1000 and 5000. The instantaneous position of the particle was recorded using a high - speed camera (500 to 1000 frames per second). The comparison is made by solving the equation of motion of particle with and without history force based on the Lagrangian approach. The results showed that the combination of gravity, drag and added mass forces are important for simulation of particle motion from the starting point of motion to the wall impact in the range of aforementioned Reynolds numbers. Nevertheless, the predicted trajectories underestimate the experimental observations. In this case, excellent agreement between the measured and predicted particle trajectory was obtained when the history force was included in the governing equation. Analysis of the results showed, however, the history force in comparison with the other hydrodynamic forces in prediction of the particle motion, from the starting point of motion to the wall impact has a small effect which is about 1 to 4.3 % and can be ignored. But it has a considerable effect on the bouncing motion of the particle after the first collision, even for the Reynolds numbers up to 5000.

Various problems of combinatorial optimization and permutation can be solved with neural network optimization. The problem of estimating the software reliability can be solved with the optimization of failed components to its minimum value. Various solutions of the problem of estimating the software reliability have been given. These solutions are exact and heuristic, but all the exact approaches are of considerable theoretical interest. In this paper, we propose the simulated annealing technique of mean field approximation for finding the possible minimum number of failed components in the sequential testing. These minimum numbers of failed components are depending upon the selection of time intervals or slots. The selection of time intervals or slots satisfies all the necessary constraints of the problem. The new energy function with the mean field approximation is also proposed. The constraint parameter for the annealing schedule is also dynamically defined that is changed with the selection of a time interval or slot on each iteration of the processing. The algorithm of the whole process shows that this approach can generate the optimal solution.

In this paper, the metal matrix composites containing 22 wt % Cr, 2.5 wt % C and 2 to 16 volume percent TiC were processed by solidifying Fe-Cr-Ti-C in which precipitation of titaniumcarbide and chromium carbide occurred. The microstructure and abrasion resistance of in-situ synthesized composites were compared with the unreinforced high chromium white cast iron (HCWCI) containing 22 w. t. % Cr and 2.5 w. t. % C. SEM, OM as well as abrasion machine test methods which were used for microstructure and wear evaluation of the matrix and reinforcement. As a result, an increase in Ti content, increased the hard TiC volume percent besides the coarse(Fe,Cr)7C3 in the ferrous matrix. The increase of the TiC content led to an increase in wear resistance,without any considerable increase in macro hardness.

The silica xerogel is prepared using copper source; 0.02 mol of Cu(NO3)2.3H2O that has been added to 1 mol TEOS (tetraethyl orthosilicate). The Copper ions are doped to silica matrix by the sol gel method and determination of total molar ratio of components with a reported molar ratio of H2O /TEOS(R) = 6.2. In this method, the acidity the of reaction (pH) depends on the catalyst type in the hydrolysis step and the molar ratio of H2O /TEOS (R) that is studied with gelation time (tg). In this reaction, acidity varies between 2.4 and 3.5. Average size and molecular structure of this nanocomposite were analyzed using TEM, FTIR and XRD. Copper oxide can be produced from the decomposition of copper nitrate and is doped on the silica matrix by thermal treatment.

A semi-analytical solution is presented for three dimensional elastic analysis of finitelylong, simply supported, orthotropic, laminated cylindrical panels with piezoelectric layers subjected to outer pressure and electrostatic excitation. Both the direct and inverse piezoelectric effects are investigated. The solution is obtained through reducing the highly coupled partial differential equations (PDE''s) of equilibrium to ordinary differential equations (ODE''s) with variable coefficients by means of trigonometric function expansion in longitudinal and circumferential directions. The resulting ODE''s are solved by dividing the radial domain into some finite subdivisions and imposing necessary continuity conditions between the adjacent sub-layers. Some numerical examples are presented for the stress distribution and electric responses due to outer pressure in both sensorial and actuating states. Also, the effect of geometric properties on the sensitivity and actuating power of the structure are investigated.

The flow behavior around a cam shaped tube in cross flow has been investigated experimentally using flow visualization and pressure distribution measurement. The range of attack angle and Reynolds number based on an equivalent circular diameter are within 0 ≤ α ≤ 360˚ and 2 x 104 < Reeq < 3.4 x 104, respectively. The pressure drag features are clarified in relation to the flow behavior around the tube. It is found that the highest pressure drag coefficient occurs at α = 90˚ and 270˚ over the whole range of Reynolds number. Results show that the pressure drag coefficient of the cam shaped tube is lower than that of a circular tube with the same surface area for more of the angles of attack.

This work is carried out to investigate combustion characteristics of a dual fuel (diesel-gas) engine at part loads, using a quasi-dimensional multi zone combustion model (MZCM) for the combustion of diesel fuel and a single zone model with detailed chemical kinetics for the combustion of natural gas fuel. Chemical kinetic mechanisms consist of 184 reactions with 50 species. This combustion model is able to establish the development of the combustion process with time and the associated important operating parameters, such as pressure, temperature and heat release rate (H.R.R). The dual fuel engines at part loads inevitably suffer from lower thermal efficiency and higher carbon monoxide and unburned hydrocarbons. Therefore this paper is an attempt to investigate the combustion phenomena at part loads and using methods such as injection timing advance, increasing pilot fuel quantity, and intake air throttling to improve the mentioned problems. It was found that the advancing of diesel injection timing gave little improvement in combustion parameters but other proposed methods promoted better combustion. Predicted values show good agreement with corresponding experimental values over a whole range of engine operating conditions. Implications will be discussed in details.

In this study fuzzy arithmetic is presented as a tool to tackle the prediction of the amount of barium, strontium and calcium sulfates scales in oilfield operations. Since the shape of fuzzy numbers’ membership functions is a spread representative of the whole possible values for a special model parameter, fuzzy numbers are able to consider the uncertainties in parameter determinations and thus give more real results than crisp values. Solubility product models and other required Equations for scale prediction contain uncertain parameters and therefore application of fuzzy numbers can be useful. LR fuzzy numbers and related primary arithmetical operations based on Zadeh''s extension principle have been introduced and their use in predicting scale depositions has been investigated. Parameters such as solubility products, free sulfate concentration and scale mass have been determined as fuzzy numbers. As a case study, scale depositions of barium and strontium sulfate resulted from mixing two incompatible waters have been obtained and compared with none fuzzy approach. Fuzzy computations are able to predict the maximum scale mass with respect to existing information.