Key Engineering Materials Vols. 474-476

Abstract: In fluid hydrostatic closed-type slideways systems, restrictor will take an important role of improving the performance of machine tools. Generally there are four types of restrictors to be utilized, capillary type, orifice type, slot type, and dynamic feedback type. The general oil film stiffness model of different types of restrictors was constructed and the characteristics of different types of restrictors are analyzed and compared. The analysis results demonstrated that the stiffness of restrictors depend on the geometry and structure parameters, and according to the analysis results the all types of restrictors can be designed optimally.

Abstract: A new meta-heuristic optimization algorithm–harmony search is conceptualized using the musical improvisation process of searching for a perfect state of harmony. Although several variants and an increasing number of applications have appeared, one of its main difficulties is how to select suitable parameter values. In this paper, we proposed a novel algorithm to dynamically adapt the harmony memory consideration rate (HMCR) and pitch adjustment rate (PAR) and distance bandwidth (BW). The experimental results revealed the superiority of the proposed method to the original HS, improved harmony search (IHS) and global-best harmony search (GHS).

Abstract: TiO₂ nanoparticles with excellent photocatalytic and degradation property were prepared in the solvothermal method. They were characterized by the means of the transmission electron microscopy (TEM), the X-ray powder diffraction (XRD), the thermogravimetric analysis and differential thermal analysis (TG-DTA), the Fourier transform infrared spectroscopy (FT-IR) and nitrogen adsorption. The photocatalytic and degradation property for the methyl orange aqueous solution was researched. The results showed that as-prepared TiO₂ nanoparticles were spherical crystals, and the particle size was about 10 nm. They had integrated crystal form, high crystallinity and thermal stability. The adsorption-desorption isotherms of TiO₂ particles corresponded to the typical type IV isotherm, which is a clear N₂ hysteresis loops of type H₄ in the desorption branch. The average pore size was 3.572 nm, the specific surface areas was 203.245 m²/g. Moreover, the obtained TiO₂ particles had perfect photocatalytic and degradation property for the methyl orange aqueous solution. When reacted for 150 min, the degradation rate of the methyl orange aqueous solution was at the peak, up to 99.1%.

Abstract: It is an expedient and efficient method to simulate the output power characteristics of a laser diode through the numerical analysis. In this paper, firstly, based on the rate equations of the electrons transition in the active layer, the functions of some key parameters, such as internal quantum efficiency, threshold current and leakage current, etc., are defined with the variance of working temperature. And an accurate numerical analytical model is built by adopting the low-complexity difference method. Then, the simulated results are compared with the results from testing and Optiwave3.0 software. The results show that, by using the proposed analytical model, the simulation on the output power characteristics of a laser diode can be realized in all input current fields, which overcomes the drawbacks within the Optiwave3.0 software. At the same time, the mean deviation between the simulated results and testing results is reduced obviously, and the average error is only 3.88%.

Abstract: With the development of next generation network which used Ipv6 technology, recent routers architecture meet many questions in performance, complexity and power consumption. With the expanding of network scale, how to implement a low power and MSF for IP lookup is a challenge in green high-powered router design. This paper represents a FIB multi-level mapping routing lookup architecture FMML, the dynamic routing table mapping algorithm is designed to determine the optimal strides for building tree bitmap tries so that the worst-case power consumption of the IP lookup engine is minimized. Experiments using real-life routing tables demonstrate that careful design of the data structure can reduce the power consumption dramatically.

Abstract: The dam safety assessment is related with the national economy and the people’s livelihood all the world, so it is important and meaningful to research methods of protecting the safety of dam. The dam failure disaster risk is regarded as main researching object in this thesis. The theories and methods, such as knowledge of dam engineering, risk analysis, analytic hierarchy processing, grey theory and so on, are introduced into the thesis. This research performs relatively detailed study on methods of comprehensive risk assessment, synthesis assessment structure system, and method of measuring assessment index of the dam.

Abstract: A rotary ultrasonic motor using longitudinal and bending vibration modes is proposed in this study. The proposed motor contains two exponential shape horns located on two ends, and the end tips of the horns are used as the driving feet. Two groups of PZT elements (Longitudinal PZT and Bending PZT) are clamped in the middle of the motor by a double head flange bolt to excite the longitudinal vibration mode and bending vibration mode of the motor, respectively. By the composing of the longitudinal and bending vibration modes, elliptical trajectory vibrations can be generated on the end tips of the horns, which have the same rotation directions and can driving the rotor together by frictional force. After the introducing of the working principle, modal analysis is developed to tune the resonant frequencies of the longitudinal and bending vibration modes to be close with each other. At last, transient analysis is developed to gain the vibration characteristics of the motor, and the gained elliptical trajectory motions of particles on the driving parts verify the feasibility of the proposed design.

Abstract: Based on multi-resolution analysis of wavelet, this article is aimed at building a new soft threshold function for wavelet de-noising, to overcome the discontinuous disadvantage of the hard threshold function. In the area adjacent to the threshold, continuously adjustable nonlinear functions are introduced in piecewise to process the wavelet coefficients more carefully in this area. Consequently, large deviation caused by super-compression of wavelet coefficients when using traditional soft threshold could be avoided, and the nonlinearity of the system is able to be effectively kept. Using both signal to noise ratio (SNR) and mean square error (MSE) as the evaluation indicators, simulation results show that the improved method is more effective than the method based on traditional hard and soft threshold.

Abstract: Aiming at the actual requirement of hauling hydraulic support along coalface, this paper presents a novel hydraulic winch powered by emulsion and detailedly designs mechanical transmission system and hydraulic control system. Based on virtual prototype, the 3-D model of the designed emulsion winch is built by Pro/E software, and interference simulation is carried out. In order to prove strength requirement of key component, the drum is analyzed by means of finite element analysis method and ANSYS software, and the maximum stress is obtained which less than the allowable stress. All this provides theoretical basis for the optimal design of emulsion winch.

Abstract: This study investigated the influence of excess Bi₂O₃ and Na₂CO₃ on the crystal structure, microstructure and dielectric properties of (Bi_0.5Na_0.5)TiO₃ (BNT) ceramics. The BNT ceramics were synthesized using the solid-state reaction method with various excess Bi₂O₃ and Na₂CO₃ levels (0, 1, 2, 3 and 4 mol%). The X-ray characterization revealed that all samples had a rhombohedral structure. A pure perovskite phase was obtained in all samples. The lattice parameter a tended to increase with increased excess Bi₂O₃ and Na₂CO₃ content in the calcined powders and sintered ceramics. The average particle size increased while, the average grain size tended to decreased with increased of excess Bi₂O₃ and Na₂CO₃ content. The depolarization temperature (T_d) and the Curie temperature (T_c) were slightly decreased with the increase of excess Bi₂O₃ and Na₂CO₃ content. The dielectric properties were related to the density.