Advanced Materials Research Vols. 424-425

Abstract: In order to measure the high-voltage transmission line voltage harmonic signal directly and timely, a new approach based on field intensity method is put forward, solving the problems of getting the high-voltage transmission line voltage harmonic signal indirectly by using the traditional methods. Through the establishment of the field intensity method to get voltage signal mathematical model so as to prove its correctness in theory, besides, the actual measurement circuit of harmonic detector is designed to verify the correctness of the theory. High-voltage transmission line harmonic detector can easily detect voltage harmonic content of the high-voltage line

Abstract: It is difficult to decide when the speed of a ship reaches to stability only by the experience of a test personnel in a speed and power trial. In this paper, a speed prediction method based on AR model is proposed to obtain the maximum speed automatically during the speed and power trial. In order to get high prediction accuracy, a detailed analysis is made on prediction process parameters. The results show that the related error between the prediction maximum speed and the actual value is low enough to meet the engineering requirements

Abstract: Based on the structure features of reticulated domes, a method for node generation and element connection of six typical reticulated domes is established in spherical coordinate system. A macro program is designed by using ANSYS Parametric Design Language (APDL). This six typical reticulated dome modeling are realized under given parameters such as span, rise high, grid number in circular and radial direction. It is proved by several examples that this method is simple, efficient and possible. It can be easily used to analysis the internal force and optimize design in shell structures

Abstract: Gas turbine is sensitive to ambient temperature. Different ambient temperature could change the state of the inlet air of compressor and make the gas turbine work in off design conditions. Research the effect of ambient temperature on gas turbine performance is valuable to the long-term safe operation of gas turbine. In this paper, a thermodynamic model of a simple cycle gas turbine which has three shafts was established, and steady-state performance simulation under different ambient temperature was carried out. In the two conditions of 1.0 and 0.35 work states, the effect of ambient temperature on thermodynamic parameters, specific power and thermal efficiency of gas turbine were analyzed. The result shows that: effect of ambient temperature on three-shaft gas turbine is different under different work state, and relevant factors must be considered to select the appropriate control strategy

Abstract: An analytical model based on the slip line field theory and a finite element simulation model based on Deform 3D are set up for mechanical ruling of 79g/mm echelle grating. The theory depth of the diamond tool falling in the grating aluminum got from the analytical model can provide a reference for the simulation model, and the compared groove results of the two models are both acceptable. The dynamic grating ruling simulation and its analysis make it known that the aluminum springback on the groove surface and the bump on the groove top is the main factors of grating groove indexes deviated from theoretical values, which reveals the aluminum nature of elastic-plastic deformation regularity during grating mechanical ruling

Abstract: Basing on the theory of power flow, frequency response analysis was acted on in a hydropower house under dominant frequency with measured data of Three Gorges Station in spiral case and draft tube. Power flow in walls was calculated by APDL procedure and the properties were analyzed. The conclusion is that longitudinal wave is the main method in walls of the powerhouse, energy is reflected and stacked at the top of the walls. Displacement along the river changes and power flow in walls decays obviously. Intensity of vibration origin and distance between the vibration and the wall are both the influencing factors，increasing the stiffness of buttressed walls takes the role of limiting flexural wave and shear wave effect

Abstract: The failure of rotating machine is often occurred by the rotor rubbing and the acoustic emission will be created by the rotor rubbing. The acoustic emission (AE) signal is the transient and non-stationary signal. Wavelet Transform has outstanding advantage revealing the character of this signal in time-frequency. With the increasing of the rotor speed, the noise increases a lot and the wavelet coefficients of AE signal change to high-scale. The db10 was applied in AE signal processing, and the modulus maxima method was applied to reconstruct of the signal. The result shows that the AE signal of rotor rubbing could be separated from noise by Daubechies Wavelet

Abstract: A numerical calculation code FLAC3D is used to simulate excavation of a deep foundation pit of railway station nearby pile group foundations. The horizontal deformations of pile group foundations are then calculated under different operation conditions of excavation, supporting and loading. The influence of foundation excavation to adjacent building is analyzed, which can give some reference to design and construction

Abstract: Considering the increasingly wider applications of flexible hinge in the fields of micro-electromechanical and micro-positioning etc., the optimal design method of a parabolic flexible hinge is presented. According to the structure feature and force exerted on the flexible hinge, the closed-form flexibility expressions in the working and non-working plane can be derived by using the Castigliano’s second theorem. Meanwhile, the accuracy analysis of the parabolic flexure hinge is performed. The rotation angle of flexure hinge in the working plane is treated as objective function, and the constraints of optimization model are displacements in the non-working plane and one described the accuracy of hinge, such that the optimization model expressed performance requirements of flexure hinge can be established. Based on the optimization model, the optimization designs of parabolic flexure hinge are accomplished to acquire the optimized structural parameters. In conclusion, the study on the optimization design of the parabolic flexure hinge can provide a theoretical basis for its engineering applications

Abstract: A wavelet based multiresolution watermarking method using the human visual system (HVS) is proposed. The watermark is added to the large coefficients at the middle frequency bands and low frequency band of the DWT of an image. The experimental results show that the proposed method is robust for some common image distortions, such as cutting, filtering and the JPEG compression