International Journal of Engineering
Volume:22 Issue: 3, Oct 2009

In Saudi Arabia, the Riyadh Sewage Treatment Plant (RSTP) uses the activated sludge technology as the secondary treatment process for sewage. Due to the complex nature of the process, a rather simplified, yet practical, steady state model that captures the most important features of the RSTP was developed. Actual operating and design conditions were obtained from RSTP data bank. The monthly average plant data obtained in 1997 was used to calibrate the model by adjusting four parameters: μmax,H, μmax,A, bH and bA (seasonal variation of temperature are therefore embedded within these values) A computer program was developed to solve the resulting model equations. The predictive nature of the proposed model was verified (without further tuning) using five sets of plant data collected in 2003. Model predictions were found to be in excellent agreement with the plant data (within±5%). Simulation results revealed the sensitivity of model predictions to the values parameters.

The production of protease by Bacillus licheniformis BBRC 100053 was studied. The most appropriate medium for the growth and protease production is composed of: lactose 1%, yeast extract 0.5%, peptone 0.5%, KH2PO4 0.1%, MgSO4.7H2O 0.02%. Enzyme production corresponded with growth and reached a maximums level (589 U/ml) during the stationary phase at 35°C, pH equivalent to 10 and with 150 rpm after 73 hours. Protease activity was highest at pH 8 and 45°C. The best carbon sources are respectively lactose and maltose and the best nitrogen source is peptone. The protease was highly active and stable from pH 7.0 to 11.0 with an optimum at pH 7-8. Thermo stability of the enzyme was considered in the presence and absence of 2mM CaCl2. Enzyme is non stable at temperatures higher than 50°C while the thermal stability was enhanced in the presence of Ca2+. The enzyme retained 15 and 8% of its initial activity after heating for 60min at 60°C in the presence and absence of 2mM CaCl2, respectively and retained 7 and 3% of at 70°C in the presence and absence of 2mM CaCl2..

In this study, first, different mix design of four types of Self-Compacting Concrete (SCC), 1. SCC consisted of only nanosilica, 2. SCC included only microsilica, 3. SCC consisted of both microsilica and nanosilica and 4. SCC without microsilica and nanosilica called as control mix, were casted and tested to find out the values of the Slump Flow, L-Box and 7 and 28 days compressive strength. Then, based on the results obtained and as yet there is no universally accepted standard for characterizing of SCC, the most suitable four concrete mixes were selected for further investigation of fresh and hardened concrete. For selected mixes, the fresh concrete properties such as values of the Slump Flow, L-Box, V-Funnel, J-Ring and hardened engineering properties such as compressive and flexural strength, shrinkage and swelling values were investigated for three curing conditions at short and long term. The results showed that the engineering properties of SCC mixes could not be improved by adding only nanosilica. However, a satisfactory behavior can be achieved using microsilica in the SCC mixes. However, by adding both microsilica and nanosilica to the SCC mixtures, the best effect on the engineering properties was reported while comparing to the control mixes.

Finding the equilibrium path by non-linear structural analysis is one of the most important subjects in structural engineering. In this way, Incremental-Iterative methods are extremely used. This paper introduces several factors in incremental steps. In addition, it suggests some control criteria for the iterative part of the non-linear analysis. These techniques are based on the geometric of equilibrium path. Finally, some examples illustrate the capabilities of suggested approaches.

In many signal processing applications, such as EEG analysis, the non-stationary signal is often required to be segmented into small epochs. This is accomplished by drawing the boundaries of signal at time instances where its statistical characteristics, such as amplitude and/or frequency, change. In the proposed method, the original signal is initially decomposed into signals with different frequency bands using wavelet transform. The fractal dimension of the decomposed signal is calculated in a sliding window and the results are used as a feature for adaptive segmentation. A criterion is introduced in this paper to choose a proper length for the sliding window. Performance of the proposed method is compared with that of three other existing segmentation methods using synthetic and real EEG data. Simulation results show the high efficiency of the proposed method in signal segmentation.

This paper proposes a novel, bi-objective mixed-integer mathematical programming for an open shop scheduling problem (OSSP) that minimizes the mean tardiness and the mean completion time. To obtain the efficient (Pareto-optimal) solutions, a fuzzy multi-objective decision making (fuzzy MODM) approach is applied. By the use of this approach, the related auxiliary single objective formulation can be achieved. Since the OSSP are known as a class of NP-hard problems, a tabu search (TS) method is thus used to solve several medium to large-sized instances in reasonable runtime. The efficiency of the results obtained by the proposed TS for small, medium and large-sized instances is evaluated by considering the corresponding overall satisfactory level of all objectives. Also the adaptability of the yielded solutions of the proposed TS for the small-sized instances is evaluated by comparing the results reported by the Lingo software. Several experiments on differentsized test problems are considered and the related results are indicated the ability of the proposed TS algorithm to converge to the efficient solutions.

Flower-like ZnO nanostructures were synthesized by decomposing Zn(OH)2 in 1,4- butanediol at 105 °C for 36 h. Size of flower-like ZnO nanostructure can be controlled by pH of the aqueous solution. In the preparation of flower-like ZnO nanostructure, zinc nitrate was used as a precursor. The morphology and microstructure of flower-like ZnO nanostructure have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The synthesized flower-like ZnO nanostructures have a hexagonal wurtzite structure. A possible growth mechanism with regard to pH solution has been proposed.

Silica phases were precipitated on aluminum surface by potentiostatic plasma electrolysis technique. Aqueous sodium silicate solutions with different concentrations were used for this purpose. SEM, EDS, XRD, surface profiles and polarization curves were used to study coatings properties. The results showed that the growth of the silica containing phases on aluminum surface was promoted by increasing sodium silicate content of the electrolyte. However, in very high concentration solutions, the morphology of the oxide films changed and the roughness of the coating increased. Moreover, the amorphous compounds were substituted for crystalline phases. Coated specimens showed high corrosion resistance in 3.5 % NaCl media.

The SiO2-CaCl2 hybrid porous materials were prepared by the sol-gel method. This process was conducted by the hydrolysis and condensation of Tetraethyl orthosilicate (TEOS) by replacement of ethanol from alcogel and drying at the ambient temperature to obtain xerogel structure. The alcogel samples were synthesized from TEOS, EtOH, H2O, HCl, NH4OH and CaCl2, while the total molar ratio of the compounds was 1: 9: 4: 8 x 10-4, 8 x 10-3, respectively. Xerogel containing 30 wt % of CaCl2 (dry matter) was prepared and characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Furier Transmittance Infra Red spectrum (FT-IR), Energy Dispersive X-ray (EDX) and Thermal Gravimetric Analysis (TGA) systems. The results obtained from SEM and EDX showed the micrograph of CaCl2 on the silica and chemical elemental analysis, respectively. On the other hand, The TEM micrograph confirmed average particle size of SiO2-CaCl2 about 50 nm and FT-IR spectrum described the functional groups of the nanocomposite. The thermal analysis of SiO2-CaCl2 nanocomposite was performed using TGA system and the results showed that the suitable temperature for initial thermal treatment was about 200°C.

A mathematical model for blood flow in narrow capillaries under the effect of transverse magnetic field has been investigated. It is assumed that there is a lubricating layer between red blood cells and tube wall. The transient flow of the fit red blood cell surrounded by plasma annulus in the narrow capillary is considered. The analysis of fluid flow between red cell and tube wall, when the cell appears to be at rest and the capillary wall moving backwards, is made. The effect of transverse magnetic field on the flow is examined. Computational results are shown through graphs to describe the effect of various parameters on velocity profile, leak-back flow rate and skin friction.