Advanced Materials Research Vols. 268-270

Abstract: Air-jet pump as the pneumatic source of a vehicle-mounted vacuum toilet provides the vacuum to pump the fecal sewage out of toilet bowl via the compressed air passing through the pump under certain pressure. In this study, Computational Fluid Dynamics (CFD) technique is employed to investigate the effects of three important air-jet pump geometry parameters: the primary Nozzle Exit Position (NXP), the constant-area section length (L₁) and the diffuser diverging angle (θ), on its performance. A CFD model is firstly established according to 1D analytical method, and then used to create 135 different air-jet pump geometries and tested under different operating conditions. The significance of this study is that these findings can be used to guide the adjustment of NXP, L₁ and θ to obtain the best air-jet pump performance when the operating conditions are different.

Abstract: In the field of electric appliances’ reliability, the constant-stress accelerated-life-test is commonly used to test the reliability of electric appliances. A new analysis method based on constructed data is introduced to analyze the constant-stress accelerated-life-test data of electric appliances under Weibull distribution. The correlation between shape parameter and characteristic life is took into account and the estimated value of characteristic life is modified, which increase the model fitting optimization and improve the analysis precision. Moreover, the method avoids table lookup and is easy to be realized by computer software in the application of reliability engineering for electric appliances.

Abstract: Micro machining by wire electrical discharge machining (WEDM) has become prosperous owing to its ability to machine conductive, exotic and high strength and temperature resistive (HSTR) materials with the scope of generating intricate shapes and profiles. In order to achieve the very high accuracy micro machining, one of the key factors is the preparation before actual machining. According to the authors' experiences and studies in micro machining by WEDM, for the first time, this paper introduces the preparation process for WEDM in micro machining. From the gauge setup, wire alignment adjustment, working coordinate setup to calibration method for rotational axis, the preparation process has been studied and introduced in detail, which forms the solid basis for high accuracy micro machining by WEDM. Experimental results show the accurate geometrical features can be fabricated based on the proposed preparation process.

Abstract: The wind is the main driving force of wind turbine, which directly affects the dynamic responses of generator. Due to its randomness and intermittence, wind energy has great impact on the quality and security of the operation of power system. The aim of this paper is to study the influence of wind speed fluctuation on the dynamic responses of the doubly fed induction generator (DFIG) connected to a power system. The mathematical models of a 3.6 MW DFIG and different wind speed patterns are first derived. The MATLAB/Simulink software is then utilized to model the DFIG, grid-side converter, rotor-side converter, and the wind speed patterns. Simulation results obtained from these models are used to analyze the effects of wind speed fluctuation on the system dynamic responses.

Abstract: Three-point bending tests of nanowires with Contact atomic force microscopy reveal that the Young’s modulus of a nanowire is size-dependent. The modulus changes with the diameter of a nanowire. This size dependency can be explained within the framework of classical continuum mechanics by including the effects of surface stress. In this study, an analytical solution has been derived for the elastic strain energy of a nanowire with both ends clamped and contacted by an AFM tip at its midpoint. Different from previous theoretical models, the present model can handle the case of large deflection, where the displacement of the nanowire is in the same order of the diameter. Based on the equivalence of elastic strain energy, the apparent Young’s modulus of a nanowire is expressed as a function of the elastic modulus of the bulk and that of the surface, and the dimensions of a nanowire.

Abstract: The problem of a semi-infinite crack in anisotropic medium interacting with a near-tip inclusion is analyzed by the Eshelby equivalent inclusion method. The change of mode I stress intensity factor due to crack-inclusion interaction is evaluated using a novel analytical solution for the model I stress intensity factor at the tip of a semi-infinite crack due to near-tip eigenstrains. Numerical results of the mode I stress intensity factor due to the presence of a near-tip circular inclusion are presented to show the influence of the elastic stiffness of an inclusion on the near-tip elastic field. The present scheme can be applied to calculate the stress intensity at a crack-tip in anisotropic media due to the interaction of inclusions with arbitrary shapes.

Abstract: In this paper, a workflow model based on N-tree for process management in PDM system is presented. It streamlines circuits in process management to sequence, branch, parallel, and loop patterns. It also offers this workflow model’s mechanisms of construction, executing, and state transition by definitions of workflow’s node properties, node constraints and state set. Last it exhibits an instance of applying this workflow model to process management of a simple PDM system.

Abstract: In this paper, we proposed a new noise speech recognition method based on the compressive sensing theory. Through compressive sensing, our method increases the anti-noise ability of speech recognition system greatly, which leads to the improvement of the recognition accuracy. According to the experiments, our proposed method achieved better recognition performance compared with the traditional isolated word recognition method based on DTW algorithm.

Abstract: Influence diagram is a kind of graphical model that can represent both the probabilistic relationship between variables and can easy to make decisions. Extension model of Influence Diagrams is reviewed in this paper and the construction method of this new model is investigated.

Abstract: According to free configuration space, the skeleton graph of working environment of mobile robots was constructed. The length of link of skeleton graph was quantified according the actual length of pathway and presented with quantitative length matrix. The width of link of skeleton graph was quantified by the width rate of pathway and robot body, and presented with quantitative width matrix. For a pathway with width changing, the width was quantified according to the minimum width of the pathway. For multiply pathways between two vertexes, the pathways were merged into one pathway. In dynamic environment, the matrix value of link was set to -1 for a pathway with obstacles. In Dijkstra algorithm, the coordination path planning of multiply robots was implemented by comparing the remaining capacity of pathway width and the robot body.