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The effects of total carbohydrate, total protein, carbohydrate/protein ratio, amino acid contents, initial pH and aeration on biomass yield product of Bacillus thuringiensis subsp. kurstaki was investigated. The bacteria were cultured in economical media comprising agricultural products and by-products including fishmeal, cottonseed meal, defatted soybean meal, cornsteep liquor, yeast extract, scotafeme, sorghum and peptone as protein sources and glucose and beet molasses as carbohydrate sources. The results indicated the presence of a direct correlation between yield biomass and carbohydrate/protein (C/N) ratio as well as the glutamic acid content of the media. The highest biomass was produced in the media providing 0.4 – 0.5 C/N ratio and 13.9% glutamic acid. A pH range of 7.0 to 8.0 was needed for high yield production. The optimal ratio for culture volume to flask size and shaking speed were 1/5 and 250 rpm, respectively. The biochemical factors described can be considered as the minimal criteria to evaluate culture media for biomass production from Bacillus thuringiensis subsp. kurstaki.

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Aims: The increasing development of microalgae applications has led to the concentration of new multidisciplinary studies to facilitate commercial cultivation of these organisms due to cost reduction and productivity enhancement. The aim of this study was the growth and quality optimization of Spirulina biomass by changing the dilution of medium and using the aeration cycle.
Materials and Methods: In this experimental study, the effect of concentration of Zarrouk medium (0 to 100% dilution) and aeration cycle on specific growth rate and dry weight, as well as the content of chlorophyll and carotenoids of Spirulina were investigated, using response surface method, central design. A total duration of 16 hours was aerated in any 24-hour period; the interval time between these aerated periods varied between 1 to 8 hours. The data were analyzed by SPSS 16 software, using multiple regression test.
Findings: The highest biomass (0.659mg/ml) was obtained at 80% concentration of culture media and aeration cycle of 2.75 hours and the highest specific growth rate (0.230 daily) was obtained at 60% concentration and aeration cycle of 4.5 hours. The highest aeration cycle (8 hours) resulted in a significant and simultaneous increase in the content of chlorophyll and carotenoids (11.65 and 2.67 mg/g, respectively).
Conclusion: The growth and quality optimization of Spirulina biomass can be accomplished by changing the dilution of the medium and using the aeration cycle.

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One of the important parts of many large dams is flood release chute spillway. Aerators are installed on chute spillways to prevent cavitation phenomenon under very high speed water flow. An aerator consists of a ramp providing a sudden slope change that separates water from the bed and permits air to mix with water. For the study of flow condition in aeration zone and for having an insight knowledge about the aeration, the study of flow condition on the ramp is a prerequisite. The change in the slope of the bed is common in spillways due to the change in the topographical slope and at the connection of the spillway and the stilling basin. In the present study, the flow condition at the place of sudden slope change was numerically simulated by FLUENT software. FLUENT is powerful software in simulation of water flow, in which the effects of turbulent are well considered. In this software, the Navier-Stokes equations are numerically solved. Volume of fluid method is applied to simulate the free surface water accurately. The results of the model in terms of pressure distribution at bed, pressure distribution in depth, velocity profile and water surface profile were compared with the results of an analytical model of streamline method as well as with the available experimental data. The analytical model is a streamline method based on conformal mapping with the basic assumption of ideal flow. The results of the model were compared in various slopes and water velocities. The study showed that numerical model can predict water surface profile and dynamic pressure properly and the results of numerical model are more accurate as compared to analytical model for the two important parameters of pressure distribution at the bed and the velocity profile. The pressure distribution was reasonably predicted by the numerical model at the bed of channel before the ramp for all the studied degrees and at the bed on the ramp for smaller degrees. The maximum error was nearly 5-10 percent. The velocity profile calculated by the numerical model was very close to the experimental data and the maximum error was nearly 5 percent. The analytical method was found quite capable in prediction of dynamic pressure and water surface profile, and less accurate in predicting the velocity profile. The study also showed that before and after the slope change, the influence length, where the dynamic pressures are significant, is dependent on the degree of sudden slope change and also on the amount of normal depth. Furthermore, the water surface profiles calculated by the numerical model and the analytical model were quite coincident, showing that the effects of gravity, viscosity and turbulence parameters on the water surface profile are insignificant.

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The nitrogen oxide emission is known as a potentially hazardous pollutant in reacting flows. To improve this process, it is of fundamental importance to take into consideration environment protection through reduction of fuel consumption in addition to increasing combustion efficiency. The control of NO emission from the combustion process is an important design criterion in modern gas turbine technology. In the present work a two-dimensional combustion simulation is developed for a model gas turbine combustion chamber. The k−ε turbulence model and the eddy dissipation concept model are applied for flow predictions and reaction rate simulation respectively. The flow field pressure linked equations are solved using the SIMPLE algorithm. In the present work, the thermal and prompt NO formations are estimated and calculated for three different methane, propane and pentane fuels. Also the effects of equivalence ratio and primary aeration on nitrogen oxide emission are considered. Results of numerical simulation show that the nitrogen oxide emission significantly affected by the equivalence ratio for all three type of fuels. Also by applying primary aeration the averaged nitrogen oxide production can be significantly reduced.

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Outlet conduits are one of the important parts of dams. Due to the high flow rate and pressure drop, problems such as cavitation can affect these structures. Considering these problems, detailed design is necessary. Laboratory studies are usually carried out which are expensive, thus, numerical models for determining complex flow characteristics have attracted the attention of the designers. In this study, the numerical simulation of Jegin dam outlet conduit in south of Iran with the scale of 1:10 is provided and the results are verified by experimental information taken from physical model built and tested at Water Research Institute. Gate opening in this research is always 70% and the water head is the constant value of 38.6m. The research is focused on the intake gate and not the service one, so the service gate is always fully opened. FLUENT computer code is considered for the numerical model studies. In the numerical simulation the Finite volume mixture two phase flow scheme is used together with k–e turbulence model. The flow discharge and air supply from the air vent downstream of the gate is then computed by 3D numerical model for different channel geometries. Reasonable agreement between the numerical model and experimental results shows reliable performance of the numerical model. This study showed the ability of the numerical model to simulate the complex air water flow in high speed gated tunnels. This study also includes the effect of the height to width ratio of the conduit on flow discharge and aeration downstream of the gate. To do this, different numerical models are simulated among which the difference is the height to width ratio of the conduit. Height and width of the conduit are measured at the gate section and changes are applied in two cases of constant height (depth) and variable width, and constant width and variable height. Results show more aeration and more flow discharge while heightening and widening of the outlet. Flow discharge has also been determined as function of the height to width ratio of the conduit at gate section of the channels. One of the important results is that in comparison with the width changes, height changes of the channel affect hydraulic characteristics of flow more and the diagram rates vary more sharply. Researches show that 1.5 to 2 ranges for height to width ratio is the best range hydraulically and other ranges have effect on reducing aeration and Air demand ratio β (β in this research agrees more with the relation Kalinske and Robertson presented), so the pressure in a conduit may fall considerably below atmospheric pressure which results in cavitation and vibration. To avoid these problems, suggests not to heightening the conduit more than a specific value.

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A spillway is a hydraulic structure that is provided at storage and detention dams to release surplus or flood water that cannot be safely stored in the reservoir. In this paper, two-dimensional simulation of gas-liquid two-phase flow on stepped spillway in different discharge rate is studied. The VOF model and the two-fluid model are used in order to simulate numerically and then the results of the two models are compared. In order to study the influence of aeration in stepped spillway, two different physics are proposed. In the first geometry it is assumed that there is no air intake via stairs and in second geometry air intake and its effect on the flow over the spillway is studied by embedding hole in the top edge of stair. The air pressure is assumed to be atmospheric. The results showed that VOF model provide more accurate result than that of two-fluid model in low discharge rate. However, in cases where aeration is studied, because of mixing phases, this model is not able to simulate fluid flow as well as two-fluid model. The two-fluid model is more accurate due to solving equations for both phases (air and water). For verification, numerical results have been compared with experimental values and determined that numerical models are able to predict the total energy loss within an error range of %10 compared with the measured experimental data.

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A greenhouse study was carried out to determine the effect of nitrogen forms and different O₂ levels on growth and mineral nutrient concentrations of eggplant. The experimental design was a completely randomized factorial experiment with two factors, namely: (i) Two nitrogen forms (Ca(NO₃)₂ and (NH₄)₂SO₄) and (ii) Three O₂ levels of the nutrient solutions (1±0.3, 2±0.3, 3±0.3, and 4±0.3 mg L^-1 O₂). The results showed that ammonium application reduced all measured parameters of vegetative growth, whereas high oxygen levels increased the vegetative growth. Comparing with nitrate-N, ammonium application increased the concentrations of NPK and Zn in leaves and Zn and Cu in roots, while it decreased the concentration of Mg, Ca, Cu, Mn, and Na in leaves and Ca, Mg, Mn, and Na in roots. High levels of O₂ increased N, Mg, Ca, Cu, and Mn content of leaves, as well as Mn and Na content in roots, while it decreased the concentration of K in leaves and P and Zn in roots. According to the results, the increase in O₂ amount of the nutrient solutions partly alleviated ammonium toxicity in eggplant. Therefore, in floating hydroponic cultures, O₂ level and its distribution should be controlled and must not be lower than 4 mg L^-1.

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