Applied Mechanics and Materials Vols. 105-107

Abstract: This paper describes the basic data process of antenna surface geometrical measurement and the quality evaluation indexes, which are surface accuracy and its uncertainty.The peak to peak value of normal deviation is used to characterize the surface accuracy,and its deviation is defined as its uncertainty.The measurement errors are given under repeated measuring conditions.Under repeated measuring conditions,the simulation method is that adding the measurement errors calculated by repeated measurement to theoretical coordinates.Under single measuring conditions, the first step is to convert the measurement data from the measuring coordinate system to the design coordinate system to get the transformation parameters;then use these parameters to convert theoretical coordinates to the measurement coordinate system;and then add measurement errors to transformed coordinates for simulation.The key point is adding measurement errors to the data which do not contain measurement errors.The simulation and actual measurement experiments of a Φ0.7 meter antenna were conducted,which showed that the method is correct.

Abstract: In this paper, Ti(C,N)-Based cermets with addition of nano-carbides were fabricated by conventional powder metallurgy techniques. Then the mechanical properties, microstructure and corresponding formation mechanism have been investigated. According to the results, the microstructures of sintered cermets are composed of three kinds of hard grains: one with black core/grey shell, one with white core , and the other with no core. In addition, with more nano-carbides adding, the number of white core grains increases and that of black core grains decreases. It is also found that sintered cermets with nano-carbide additions exhibit higher transverse rupture strength and higher hardness than the others originated from much finer and more homogeneous microstructure. However, cermets with nano-micro carbide additions show the most poor mechanical properties among all sintered cermets, including conventional cermets, due to the obviously heterogeneous microstructure. And this can be explained by Ostwald ripening theory.

Abstract: Based on the single chip microcomputer (SCM) control theory, the control circuit of magnetic driving system of axial flow blood pump is designed. For the easy damage of TIP 122, which is used as the power switch of control circuit, RC snubber circuit is designed by analysis and experiments. And then an optimal matching of the key parameters is obtained to solve the security problem of the TIP 122. The experimental results show that the RC snubber circuit can improve the reliability and stability of the driving system, and to provide an experimental foundation for the further studies.

Abstract: Concrete beam and slab system is commonly applied in the main plant roof of hydropower station, which is difficult for construction and slow, having a great impact on the construction period. For the main plant roof structure (span of 30 metres)of GuanDi hydropower station in Yalong River, this paper proposes three light steel roof systems, which are arched corrugated steel roof, light gauge-steel and shell roof, and carries detailed analyses and comparisons on the force calculation, appearance, the amount of steel, site construction, anticorrosive performance and other aspects. Regarded that the light gauge-steel roof is the most suitable system for the main plant roof of hydropower station, this paper introduces the layout, arched truss design and purlin of light gauge-steel roof, providing reference for design and application of similar projects.

Abstract: This paper studies and analyses various digital filter and decimation structure. On this basis, by using QUARTUS development system design the decimation device modules, through the waveform simulation validated its correctness. Finally,a program is written into FPGA chip by the hardware platform. In the digital down conversion (DDC), CIC (cascade integral comb) filter plays an important role. It is mainly used for sampling rate, as well as low-pass filter effect. The main characteristics of CIC filter, using only adders, subtractor and register (no multiplier), so fewer resources occupied, implementation is simple and high speed. Based on the analysis of the principle of CIC filter,simulate and synthesize based on the theory of using VHDL language in FPGA. And successful application in the development of DDC chip. Keyword: CIC (cascade integral comb) filter,FPGA,VHDL

Abstract: The seismic ground motions are studied in an infinite half-space with a non-circular alluvial valley under time harmonic incident anti-plane shear waves. Based on the conformal mapping method and Fourier series expansions, the conditions of displacement continuity and stress equilibrium at the interface of alluvial valley are set as semi-circular alluvial valley in conformal plane, then the result is obtained by constructing a set of infinite linear algebraic equations with boundary discretization. The unknown coefficients in the algebraic system can be easily determined. The present method is treated as a semi-analytical solution since error only attributes to the truncation of Fourier series. Earthquake analysis for the site response of alluvial valley or canyon subject to the incident SH-wave is the main concern. Numerical examples for semi-elliptic alluvial valley are given to test our program. The research indicates that great interaction exists between the alluvial valley and the horizontal surface, which will bring on great influence on ground motion. Therefore enough importance must be attached to the existing of subsurface cavity while finishing seismic design.

Abstract: According to the analysis on the present situation and development tendency of the campus spatial form planning of newly-upgraded undergraduate universities as well as its functions and characteristics,15 evaluation indices were ascertained and the comprehensive evaluation model of the planning was established by the method of AHP (Analytic Hierarchy Process). The results showed that AHP can effectively ascertain the evaluation indices system. Through calculating the weight of each index and judging the consistency of matrixes, key factors that can influence the campus spatial form planning were obtained, such as the public green space, landscape node, visual contact axis, landscape axis, central plaza and teaching group space.

Abstract: This paper investigates the typical positioning fixture design under a virtual environment. The modeling and assembling work of the fixture are firstly presented by CATIA V5. Then the static interference analysis and the dynamic interference analysis for the fixture are proceeded in the BUM module. Finally, the simulation is taken in the processing module to check the feasibility of the designed fixture. The presented research in this paper offers an engineering reference for positioning fixture design.

Abstract: With the development of science and technology, the smaller sizes generator, the more attention by people. The main purpose of this article is to manufacture piezoelectric nanogenerator under micro vibration and its working principle is introduced and its performance is studied. The results show that, using the present nanomaterials, piezoelectric materials can be prepared. When its wind in copper laps, under the situation of micro pulse vibration its can turn into electrical energy, thus yield piezoelectric nanogenerators. In ambient vibration condition, piezoelectric materials produce larger rated current and voltage. However, copper laps cutting magnetic line of force produce less rated current and voltage. So the piezoelectric nanogenerators can be separately used to supply power. If multiple piezoelectric nanogenerator in tandem may produce higher voltage, current and power, which possess commercial value.

Abstract: Particulate flow is commonly encountered in industries as well as in many other chemical and mechanical engineering applications. The accurate measurement of particle size distribution is of the utmost importance since it decides the physical and chemical characteristic of the particles. The light extinction method can be used for in-line monitoring of particle systems thus providing real time measurements of both particle size distribution and particle concentration. In light extinction particle sizing, a classification inversion algorithm is proposed for the circular cylinder particles. The measured circular cylinder particle system is inversed with different particle distribution functions and classified according to the inversion errors in the dependent model. The simulation experiments illustrate that it is feasible to use the inversion errors of object functions to inverse the circular cylinder particle size distribution in the light extinction particle sizing technique. This classing inversion algorithm can avoid the defects that the type of the size distribution must be assumed beforehand for the light extinction method.