In this paper, a one-dimensional bi-stage phononic band gap (PBG) structure based on double local resonant effects is presented to reduce the torsional vibration for the first time. A unit cell of the bi-stage PBG structure is composed of two harmonic LR oscillators in the radial direction, distributed periodically along the shaft. A new method, combining the transfer matrix method and the lumped-mass method is proposed to study the torsional vibration band gaps of the double PBG-like shaft theoretically and proved by the finite element method. The results show that the mid-gap frequency of the bi-stage PBG structure shaft is lower than that in the one-stage PBG shaft and the relative width of the band gaps reaches 1.3 with the average attenuation of the vibration amplitude about 40dB.
To eliminate the release-delayed phenomenon of macromolecular drug delivery system at the early stage, biodegradable implantable drug delivery system with micro-porous structure was designed by Bio-MEMS technology in this paper. Water absorption and degradation characters of polylactic acid - polyglycolic acid (PLGA) material with different monomer ratio were studied. Drug release model was built by mass transfer equation and the Finite Element Method. Influencing factors about the cumulative amount of release drug were analyzed. And the results suggest that with more ratio of polylactic acid(PLA), PLGA would have more greater amount of water absorbed as well as a longer degradation time. Better linearity of cumulative amount of release drug would be achieved by reducing the diameter and number of micro-porous.
ion Method for Displacement Response in the Sweep-Frequency Testing of Rotating Spindle
Guo Yuzhu1,a*, Chen Tianning1,b, Wang Xiaopeng1,c and Xu Yanfei11 State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, 710049 Xi’an, China
aguoyuzhu@126.com, btnchen@mail.xjtu.edu.cn, cxpwang@mail.xjtu.edu.cn
Keywords: Rotating spindle; Sweep-frequency measurement; Error separation.
Abstract. In the measurement of motorized spindle dynamic performance, the non-contact sweep-frequency excitation is adopted to obtain the displacement response of spindle rotor under high speed rotating. Due to the shape error at measurement section, eccentric error and random vibration, the illusory signals is introduced to the practical measured signal, which makes it difficult to analyze the displacement response. To effectively separate the error, a new method combining template signal and slip filtering is presented. After analyzing the characteristics of displacement response and illusory signals in time-frequency domain, the template signal constructed by the non-superposing portions between response and error is employed to eliminate the error in superposing portions. And a band-pass filter which can slip in time-frequency domain is employed to eliminate the other error. A spindle of CNC milling machine is tested at 7000 r/min, and the analysis result shows that the displacement response can be abstracted successfully from the original signal measured by rotating spindle.
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