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Li Zhou,Tianqi Zhang,Yanyun Luo 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.9
In terms of the traditional dynamic vibration absorber (DVA), the vibration damping effect improves with the mass ratio of DVA increasing, and the vibration level of target system is effectively controlled in the case that the mass ratio of DVA is large. This characteristic restricts the application of DVA to the track because of the limited available space. This study proposes one type of DVA with negative stiffness (NSDVA) applied to floating slab track to reduce the track vibration under the condition of small mass ratio and presents a design methodology of NSDVA attached on flexible system. Firstly, the mechanical model of floating slab with NSDVA is simplified to a two-degree-of-freedom system, and theoretical expressions of NSDVA’s optimal parameters, i.e., ratio of frequency, damping and stiffness are deduced according to the fixed-point expansion theory and stability condition. Secondly, with the combination of the multi-modal control theory and the finite element method, optimal parameters of NSDVA applied to a multi-degree of freedom (MDOF) system are calculated. 3-D finite element model of floating slab-NSDVA is built in ABAQUS software, and the modal analysis of floating slab is conducted to determine the target modal and equivalent mass. Compared with the traditional Voigt type DVA, the NSDVA adopted in this paper is proved to be more effective to reduce the both floating slab and rail vibration level. The design methodology of NSDVA attached to a MDOF system presented in this paper is feasible.
Yun Deng,Yali Luo,Bingjun Qian,Zhenmin Liu,Yuanrong Zheng,Xiaoyong Song,Shaojuan Lai,Yanyun Zhao 한국식품과학회 2014 Food Science and Biotechnology Vol.23 No.2
The antihypertensive activity of few-flower wildrice was studied in spontaneously hypertensive rats (SHRs)with evaluation of blood pressure lowering effects andtranscriptional levels of the sarcoplasmic reticulum Ca2+-ATPase (SERCA2a) gene that is regulated by AngiotensinII (Ang II). SHRs were randomly divided into 5 groupswith 6 rats each. The systolic blood pressure (SBP) reachedthe lowest point 3 h after administration of a single dose ofpaste made from few-flower wild rice stem powder. TheSBP of SHR in the relatively high amount of RSP (HRSP)administrated group was reduced by approximately 30mmHg, compared to the negative control group, and wasnot significantly different from the positive control IPPcontrol group at a dose of 1.5 mg/kg body weight (p>0.05). RSP administrated SHRs showed a significantly higherSERCA2a transcription level than negative control SHRs(p<0.05). RSP administration had no negative effects onglycometabolism of SHR.