Abstract: As the single ground environment and correction circuits of current pressure measurement and control system are too complicated to increase its test precision, the distributed ground - tunnel pressure measurement and control method is proposed.The paper focused on analyzing the idea of control strategy, describing the algorithm, principle, and other methods. Then main to deduce the relevant operations formula, give a detailed control block diagram. Finally, in order to detect the effect, the experimental test and simulation were carried out and then analyzing the results. Simulation is done to show the efficiency and feasibility of proposed approach.
Abstract: The effects of dye coating duration on the performance of inverted bulk heterojunction organic solar cells based on a blend of poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV) as donor and (6,6)-phenyl-C61 butyric acid methyl ester (PCBM) as acceptor with a structure of FTO/Eosin-Y coated ZnO nanorod arrays/MEHPPV:PCBM/Au utilizing ZnO nanorod arrays as electron collecting layer and gold as a hole collecting electrode were investigated. ZnO nanorod arrays were grown on fluorine-doped tin oxide (FTO) glass substrates which were pre-coated with ZnO nanoparticles using a low temperature chemical solution method. The ZnO nanorods-coated FTO substrates were immersed in the Eosin-Y dye solution at 60 oC for 15, 60 and 120 min. The power conversion efficiency of the solar cell increased with dye coating duration and reached an optimum value at dye coating duration of 60 min. The device with dye coating duration of 60 min exhibited the highest power conversion efficiency of 5.05 x 10-4 % with short circuit current density of 9.95 μA/cm2, open circuit voltage of 0.18 V and fill factor of 28%.
Abstract: Experimental investigation of sound absorption characteristics of aluminium foam is carried out under laboratory test conditions. The studies revealed that the developed aluminium foam have excellent sound absorption properties and is comparable with other sound absorbing materials. Excellent sound absorption property coupled with good mechanical properties makes this material ideal for sound absorption under difficult situations. Experimental results revealed that the thickness of the specimen affects the sound absorption properties of the material, and there exists an optimal thickness, at which sound absorption coefficient is maximum. Experimental evidence showed that presence of damaged cell edges, open and/or semi-open cells in the specimen surface, enhances the sound absorption capability of the material.
Abstract: Self-excited combustion oscillations are caused by a coupling between acoustic waves and unsteady heat release. A premixed laminar flame in a Rijke tube, anchored to a metal gauze, is considered in this work. The flame response to flow disturbances is investigated by developing a nonlinear kinematic model based on the classical-equation, with the assumption of a time-invariant laminar flame speed. Unsteady heat release from the flame is assumed to be caused by its surface variations, which results from the fluctuations of the oncoming flow velocity. The flame is acoustically compact, and its presence causes the mean temperature undergoing a jump, whose effect on the dynamics of the thermo-acoustic system is discussed. Coupling the flame model with a Galerkin series expansion of the acoustic waves present enables the time evolution of the flow disturbances to be calculated. It was found that the model can predict the mode shape and the frequencies of the excited combustion oscillations very well. Moreover, the fundamental mode is found to be the easiest one to be triggered among all acoustic modes. To gain insight about the mode selection and triggering, further numerical investigation is conducted by linearizing the flame model and recasting into the popular formulation.
Abstract: Composite materials are now a day most frequently used materials in aerospace structures. Mechanically fastened joints are usually used there for joining process due to number of advantages over other conventional joints. These joints are easy to assemble and dissemble and are cheaper. However, they create stress concentration near the hole, leading to source of nucleation and subsequent propagation of cracks under cyclic loading. They also increase weight of the system tat may nullify the advantages we get from composite materials. The present work intent to find fatigue life of two composite laminates usually employed in spacecraft structures. The composites studies are fiberglass reinforced Plastic (FRP) and Carbon Reinforced Plastic (CRP). After preparing the composites, moisture, tension and fatigue tests were conducted on both composites. To know the behavior under damped condition, absorption tests were conducted. Fatigue tests were done both under as plate and butt joint conditions. It was found that in bolted joint condition, both CRP and FRP plates fails in net tension at minimum load but for maximum load they fail in shear.
Abstract: This paper aims at developing the numerical of delamination in laminated composite structures. Formation of initial delamination and growth of existing delamination in HAT-Section laminated made of plies of unidirectional carbon fiber reinforced epoxy resin is investigated computationally. Tsai-Hill failure method is employed to predict delamination initiation while delamination propagation is analyzed using linear elastic fracture mechanics (LEFM).The techniques based on LEFM that have been utilized successfully within the framework of the finite element method (FEM) for the simulation of delamination growth, the virtual crack closer technique (VCCT). Finally this paper proposes future work for precise prediction of delamination of unidirectional carbon fiber reinforced epoxy resin HAT-Section specimens.
Abstract: The micromechanical approach of Simplified Unit Cell Method (SUCM) in closed-form three dimensional solutions is used for predicting creep response of unidirectional fiber reinforced composites. The composite consist of elastic fibers reinforcing nonlinear viscoelastic resin. The nonlinear viscoelastic matrix behavior is modeled by using Schapery single integral viscoelastic constitutive equation. Off-axis specimens of graphite/epoxy with 45 and 90 fiber orientations were subjected to 480 minutes creep tests and the results is compared with experimental data and MOC results available in the literature. There is good agreement with experimental results due to using SUCM.
Abstract: The interface instability of the co-extrusion flow of polyethylene and polypropylene is studied experimentally in a slit geometry. This is done by introducing disturbances of controlled wave length and amplitude on three-layer symmetric (A-B-A) polymer melts and performing a series of extrudate mechanical testing. In this study variations of the mechanical properties as well as wave interlocking have been related to the conformation of the interfacial waves (IW). By investigating the growing (IW) and tensile stress of extrudate samples a relationship between interfacial instability (II) and mechanical properties of polypropylene (PP) and high density polyethylene (HDPE) has been established. It has been shown that instabilities are associated with IW, and it turns out that IW amplitude is known as a mechanism for controlling the strength of three layer polymer products. It is shown that the mechanism of interfacial strength is related to interfacial instabilities and the interfacial wave interlocking.
Abstract: Gallium or sulphur additions in CuInSe2 were prepared using RF magnetron sputtering and pulsed laser deposition respectively. All of the observed thin films show a chalcopyrite structure with the S addition increases the favourable (112) peak. The optical absorption coefficients were slightly decreased. The films energy band gap could be shifted from 1.04 to 1.68eV by adjusting the mole ratio of S/(S+Se) and In/(In+Ga). It is possible to obtain the optimum energy band gap by adding S solute or Ga at a certain ratio in favour of Se and In respectively. It is also necessary to control the ratio of Ga and S additions and to retain a certain portion of In to provide better properties of CIS films.
Abstract: 20% Ytterbium (III)-doped perovskite structured barium zirconate, BaZrO3, was prepared by two different synthesis routes: solid state and sol-gel routes. 2 % Zinc (II) was added as an acceptor dopant at the Zr (IV) site according to stoichiometry. It was also added as 2 % excess of the formula. The purpose of this study is to see how zinc (II) acts as a sintering aid in view of synthesis route, densification and conductivity of the material. A dense ceramic (90% of theoretical density) was achieved by the sol-gel method when stoichiometry was adjusted. Phase purity of the samples was checked by X-ray powder diffraction (XRD). Thermogravimetric analysis (TGA) and Impedance spectroscopy (IS) was used to characterize hydration and electrical conductivity respectively.The data shows that the addition of stoichiometric amounts of Zn2+ via sol-gel synthesis route promotes not only densification but also water incorporation and conductivity in comparison with the solid state route, keeping the same final sintering temperature of 1500°C. For example, pre-hydrated BaZr0.78Zn0.02Yb0.2O3-δ, prepared via the sol-gel method shows total conductivity (σtot) value of 3.14*10-5 and 3.8*10-3 Scm-1, whereas for the solid state route, σtot values are 1.74*10-5 and 8.87*10-4 Scm-1 under dry Ar (heating cycle) at 300° C and 600° C, respectively.