International Journal of Engineering
Volume:25 Issue: 1, Feb 2012

In this study, Glucoamylase production by Aspergillus Niger was investigated under solid state conditions with low cost by-products of agricultural processes as substrate. Highest enzyme production was observed when a combination of wheat bran (WB) and corn flour (CF) was used as compared to WB+ rice bran, WB+ rice flour and WB alone. Different additions of (CF) were tested and WB+ 10% CF showed to be the best combination. Study of the fermentations in flasks revealed 373.3 IU/gds and 41.4 g/l for the enzyme activity and protein concentration respectively under conditions of 301oC, pH4.7 and time 96 h. Optimum conditions provided by flask experiments were applied to produce the enzyme in a fermenter. A tray type sterilizable fermenter was designed (7-lit volume, 2 trays of 450x230x35 mm, and 2 l/min aeration). The fermentations were performed under aseptic conditions and resulted in enzyme activity and protein concentration of 400 IU/gds, 33.3 mg/gds respectively (under 302oC, pH=4.5 ~ 4.7, aeration 2 l/min, 90% relative humidity and time 72 h). The adequate amounts of enzyme activity, protein concentration and CO2 evolution revealed the efficiency of the bioreactor in comparison with flasks.

Pulsatile motion of blood in a circular tube of varying cross-section has been developed by considering slip flow at the tube wall and the blood to be a non- Newtonian biviscous incompressible fluid. The tube wall is supposed to be permeable and the fluid exchange across the wall is accounted for by prescribing the normal velocity of the fluid at the tube wall. The tangential velocity of the fluid at the tube wall is also accounted in the present investigation. A perturbation technique has been carried out for low Reynolds number flow and for small amplitude of oscillation. The effects of slip parameter, leakage parameter, Reynolds number and apparent viscosity coefficient on the streamlines, wall shear stress and pressure drop have been discussed and shown graphically for suction and injection respectively.

Expansive and collapsible soils are some of the most widely distributed and costly of geologic hazards. These soils are subject to changes in volume and settlement in response to wetting and drying, often resulting in severe damage to structures. Collapsing soils are generally characterized by sudden and large volume decrease at constant stress when inundated with water. A geotechnical engineer needs to be able to identify readily the soils that could collapse and to determine the amount of collapse that may occur. Various methods of predicting collapse from simple and rapidly-performed index have therefore been suggested by several workers in the field. In this investigation, most of the well known collapses identifying criteria are reviewed and evaluated. New interpretations and a new method that permits rapid and safe prediction of collapse have been put forward.

Silos are structures that are used for storing different types of granular material. Dynamic behavior of silos under seismic loads is very complex. In this paper seismic behavior of steel silos with different height to diameter ratios is investigated by considering granular material-structure interaction using ABAQUS finite element package. Silo wall is modeled by shell elements and its behavior is considered elastic, seismic behavior of granular material inside silo is highly nonlinear and requires a complex nonlinear description of the granular material. The hypoplasticity theory describes the stress rate as a function of stress, strain rate and void ratio. The granular material is modeled by solid elements and its behavior is considered with a hypoplastic constitutive model, for modeling of interaction between silo wall and granular material, surface to surface contact with coulomb friction law is considered between silo wall and granular material. The results show that the seismic behavior of silos is completely related to the silo stiffness and height to diameter ratio.

The main objective of this paper is to present a wavelet-based procedure to characterize principle features of a special class of motions called pulse-like ground motions. Initially, continues wavelet transform (CWT) which has been known as a powerful technique both in earthquake engineering and seismology field is applied easily in automated detecting of strong pulse of earthquakes. In this procedure, BiorSpline (bior1.3) basis from biorthognal wavelet families is applied for extracting of the largest velocity pulse from normal-fault component of selected records. The selected wavelet decomposition process aids quantification of the effect of extracted pulses on acceleration and displacement response spectra. The results on elastic spectra show that, these pulses cause a significant amplification in the region of pulse period which should be appropriately incorporated in design procedure of structures in near field area. The results also have been presented for inelastic response spectra in different ductility level.

The SiO2-LiBr hybrid porous materials were prepared by the sol-gel method. This process was obtained by the hydrolysis and condensation Tetraethyl orthosilicate (TEOS) with replacement of ethanol from alcogel by the drying at ambient temperature to obtain xerogel structure. The alcogel samples were synthesized from TEOS, EtOH, H2O, HCl, NH4OH and LiBr. The total molar ratio of the compounds was 1: 9: 4: 8 x 10‾4, 8 x 10‾³. Xerogel contain 30 % wt of LiBr (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 Gravimetry Analysis (TGA) systems. The results obtained from SEM and EDX were shown the micrograph of LiBr on the silica and chemical elemental analysis, respectively. On the other hand, the TEM have confirmed average particle size of SiO2-LiBr about 50 nm and FT IR spectrum describes functional groups of nanocomposite. The thermal analysis of SiO2-LiBr nanocomposite was performed using TGA system and the results show that the suitable temperature for initial thermal treatment is about 200°C.

Presently there is a little information that relates to heat shield systems. Also this information is not certain in so many cases. The main reason is that accurate calculations for measuring the sacrificing rate of various materials have not been obtained yet. Additionally, the real scale test has two disadvantages: high cost and low flexibility, and for each case we must perform a new test. So having a reliable numerical program that calculates the surface recession rate and interior temperature history is necessary. In this study numerical solution of governing equations for charring material ablation are presented in order to anticipate the recession rate and the heat response of charring heat shields. Thermodynamic properties, ,k changes relative to the temperature accompany the nonlinear nature of the governing equations and the Newton-Rafson method along with TDMA algorithm is used to solve this nonlinear equation system. Using Newton- Rafson method is one of the advantages of the solving method because it is relatively simple and it can be easily generalized to more difficult problems. In Newton-Rafson method the nonlinear equations complexity is not a dominating effect because by differentiation relative to every independent variable the structural coefficients of the governing equations system are obtained. Moreover the most important feature of the obtained equation system is that we can obtain the value of every independent variable in each iteration and by adding this amount of change in every variable to the previous one, the new variable value appears in governing equation structural coefficients and it continues up to complete convergence. The obtained results are compared with reliable sources in order to examine the accuracy of compiling code.

Behavior of blast wave in underwater explosion is of interest to metal forming community and ship designers. Underwater detonation is, also a potential hazard to the water intakes or a plant spent fuel pool. In this paper, some techniques for calculating free-field blast parameters such as pressure and impulse in underwater explosion and prediction of bubble pulsation parameters are presented and they will be compared by experimental results of underwater detonation of Hexogen explosive charge. The details of pressure pulse curves generated by detonation of Hexogen in several standoff distances are obtained, that by using scaling laws, they can be used in analysis of practical underwater detonations. Finally, the equivalent mass of Hexogen charge relative to TNT in underwater explosion is calculated.

The annular foam breaker is one which uses the vacuum and shear force generated by the Coanda effect to break foam. Its effectiveness in destroying drilling foam has been test in wellbore flow simulation loop experimental stand. Experimental results showed that the operating pressure of the annular foam breaker should be larger than 0.6MPa and the stabilizers concentration of the foam drilling fluid should be as low as possible so as to obtain higher foam-breaking efficiency. Moreover, the annular foam breaker was more effective to destroy wet foam system. When the gas to liquid ratio of the foam was lower than 100, the foam-breaking efficiency was up to 85%. From the results obtained in Yuanba-10 well located in Sichuan province of China, it can be drawn that the annular foam breaker had a high efficiency that only 400 m3 foaming solutions was consumed with total 672m of foam drilling footage in 26 in. section. The consumption of ingredient additives and water were decreased drastically with using the annular foam breaker, which reduced the foam drilling cost sharply.