Modeling of stratosphere airship
The dynamics and kinematics model is very important for the analysis of stability, manipulation and control of stratosphere airship. A full modeling approach that includes the computation of aerodynamics of airship and the added mass for the nonlinear dynamics simulation of stratosphere airships is proposed in this paper. In this approach, the aerodynamics of airship is calculated based on a panel method, an engineering estimation and theory approach. A new numerical method for calculating added masses of airship is developed by using the CFD method. This model can simulate the motion of stratosphere airships quickly and accurately.
Modelling and control of airship for low altitude surveillances application
Aerial perspective provide great viewing window especially for surveillance and exploration activities. In responding to the need of green technology, airship is the best alternative for environmental friendly technology. In addition, airship is safer for low altitudes flying and able to maneuver at low speed in confined area. In order to drive the airship to the desired position, the airship’s rudder must generate a yaw angle. Therefore, this paper presents the techniques to control the navigation path of an airship through the yawing state response. To provide good airship heading, optimal control and feedback control technique were proposed. The main goal is to produce an appropriate output signal by controlling the rudder deflection while reducing the excessive movements of the vehicles. The simulation demonstrate that the proposed controller effectively reduced the excessive movement for yaw rate and roll angle of the airship. It is shown that closed loop system has an error less than 1.6% with minimum overshoot of 2.04%. Comparatively, better results were obtained by introducing higher gain to the optimal controller thus contribute to low control response.
Production of xylanase by Aspergillus awamori on complex medium in stirred tank and airlift tower loop reactors
Abstract Aspergillus awamori was cultivated on complex medium containing wheat bran as sole carbon source in the precultures as well as in the main cultures in stirred tank and airlift tower loop reactors. The decomposition of the wheat bran particles by α -amylase and xylanase produced by the fungus was investigated by monitoring the enzyme activities, the CO 2 production rate, the concentrations of reducing sugars, glucose, xylose, phosphate and ammonium as well as by applying transmission electron microscopy. By applying synthetic medium in the preculture, the time lag was longer, the growth faster, the xylanase activity higher in the main culture, than by using wheat bran in the preculture. With increasing the stirrer speed the intimate contact between the pellets and the wheat bran was reduced, which caused a decrease of the growth and the xylanase production. By applying ground wheat bran, filamentous mycelium was formed, the growth and the substrate uptake rates increased, but the xylanase production decreased due to the less intimate contact between the fungus and the wheat bran. In the airlift tower loop reactor filamentous mycelium was formed due to the low specific power input. In spite of the high medium viscosity, high xylanase productivity was obtained. With ground wheat bran the particles were completely covered by filamentous mycelium, medium viscosity strongly increased and as consequence the growth and xylanase production decreased.