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Raheem, Shehata E. Abdel Techno-Press 2014 Coupled systems mechanics Vol.3 No.2
The dynamic characterization is important in making accurate predictions of the seismic response of the hybrid structures dominated by different damping mechanisms. Different damping characteristics arise from the construction of hybrid structure with different materials: steel for the upper part; reinforced concrete for the lower main part and interaction with supporting soil. The process of modeling damping matrices and experimental verification is challenging because damping cannot be determined via static tests as can mass and stiffness. The assumption of classical damping is not appropriate if the system to be analyzed consists of two or more parts with significantly different levels of damping. The dynamic response of structures is critically determined by the damping mechanisms, and its value is very important for the design and analysis of vibrating structures. A numerical algorithm capable of evaluating the equivalent modal damping ratio from structural components is desirable for improving seismic design. Two approaches are considered to explore the dynamic response of hybrid tower of cable-stayed bridges: The first approach makes use of a simplified model of 2 coupled lumped masses to investigate the effects of subsystems different damping, mass ratio, frequency ratio on dynamic characteristics and equivalent modal damping; the second approach employs a detailed numerical step-by step integration procedure.
CAVI를 이용한 급성기 중풍환자의 Arteriosclerosis와 한방변증의 관련성 연구
최원우,김미영,김영지,이승엽,임정태,김창현,민인규,박성욱,정우상,문상관,박정미,고창남,조기호,김영석,배형섭,Choi, Won-Woo,Kim, Mi-Young,Kim, Young-Jee,Lee, Seung-Yeop,Leem, Jung-Tae,Kim, Chang-Hyun,Min, In-Kyu,Park, Sung-Wook,Jung, Woo-Sang,Moon, S 대한한방내과학회 2008 大韓韓方內科學會誌 Vol.29 No.4
Objectives : This study aimed to clarify the relationship between the Oriental medical diagnosis and arteriosclerosis by measuring carotid-ankle vascular index(CAVI) in acute cerebral infarction patients. Method : One hundred thirty-one subjects were recruited from the patients admitted to the Internal Medical Department at Kyunghee University Oriental Medical Center from April 2007 to August 2008. We sorted cerebral infarction patients and assessed one hundred fourteen patients' CAVI data. We diagnosed dampness-phlegm by Oriental medical diagnosis and evaluated stroke type by single or multiple infarctions. then, we analyzed their characteristics with type of stroke, risk factor, lifestyle, metabolic syndrome and dampness-phlegm diagnosis. Result : 1. On the demographic variables of the patients, age, hypertension, hyperlipidemia, multiple infarction group and metabolic syndrome and dampness-phlegm group were significantly higher in the high CAVI score group than in the control. 2. According to the significant difference in the dampness-phlegm group, we analyzed dampness-phlegm related index for pattern identifications by CAVI score. As a result, dark circles, insomnia, headache, white coating tongue. slippery pulse, and rough pulse were significantly higher in the high CAVI score group then in the control. 3. In multivariate analysis, age, hypertension, multiple infarction and dampness-phlegm groups showed a close relationship with the high CAVI score group. Conclusions : According to the analysis, significance between dampness-phlegm diagnosed patients group and high CAVI score were clarified. Moreover, multiple location infarctions also have a relationship with high CAVI score in cerebral infarction patients. These results can be utilized in the future as a basis material.
Kim, Moon Young,Baik, Soon Koo,Park, Dong Hun,Lim, Dae Wook,Kim, Jae Woo,Kim, Hyun Soo,Kwon, Sang Ok,Kim, Young Ju,Chang, Sei Jin,Lee, Samuel S. Wiley-Blackwell Publishing 2007 Liver International Vol. No.
<P>Abstract</P><P>Background and Aims</P><P>Alterations in the Doppler hepatic vein (HV) waveform are associated with cirrhosis and portal hypertension. We prospectively evaluated the correlation between the extent of abnormal Doppler HV waveforms expressed as damping index (DI) and the hepatic venous pressure gradient (HVPG) and response to propranolol in patients with cirrhosis.</P><P>Material and Methods</P><P>In 76 patients with cirrhosis (69 men and seven women), both DI of Doppler HV waveform and HVPG were measured, and the relationship between them was analysed. DI was calculated by the minimum velocity/maximum velocity of the HV waveform. An HVPG>12 mmHg was defined as severe portal hypertension. In a subgroup of 19 patients receiving propranolol, changes in both DI and HVPG were evaluated after propranolol administration for 3 months. One author (S. K. B.) performed all DI of Doppler HV waveform studies.</P><P>Results</P><P>Abnormal HV waveforms were seen in 66 of 76 patients (86.8%). DI significantly correlated with the grade of HVPG, i.e. with higher HVPG increased DI was observed (<I>P</I><0.01). By logistic regression analysis, DI>0.6 was significantly more likely to be severe portal hypertension (odds ratio: 14.19, 95% confidence interval: 4.07–49.55). Receiver-operating characteristic curve according to the value of 0.6 of DI showed a sensitivity of 75.9% and a specificity of 81.8% for the presence of severe portal hypertension. In 19 patients of the propranolol subgroup, change of DI following propranolol treatment also significantly correlated with that of HVPG (<I>P</I><0.01).</P><P>Conclusions</P><P>Damping index of the HV waveform by Doppler ultrasonography might be a non-invasive supplementary tool in evaluating the severity of portal hypertension and in responding to propranolol in patients with liver cirrhosis.</P>
Study on Seismic Response and Damping Performance of Tunnels with Double Shock Absorption Layer
Tonglai Zhou,Changsong Dong,Zhipeng Fu,Shuang Li 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.5
Shock absorption layer is an effective measure to decrease damage of tunnels under earthquake. According to previous work, the smaller stiffness of damping material, the better damping effect of the tunnel. In order to meet the actual engineering requirements, the shock absorption layer is applied to the upper part of tunnels (not including the invert), which is called a local shock absorption layer. This study is to analyze the damping effect of different types of local shock absorption layers based on the dynamic nonlinear time-history numerical analysis. Six real ground motions with different dominant frequencies are selected, their peak ground accelerations (PGA) are set to 0.2 g, 0.4 g, 0.6 g, and 0.8 g, respectively. The damage index and total dissipated energy of secondary lining, and equivalent plastic strain of surrounding rock are used as indicators to reflect the damping performance of the local shock absorption layer. Numerical results highlight that the damping performance with double local shock absorption layer is the best, and the damping performance of shock absorption layer under large earthquake is better than that under small earthquake.
The Study of Current Mode Rectifier Control Technology
Luo Min,Liu Bang-tao,Xia Yu Cheng 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.5
The accumulator battery test requests its system converter to output excellent charging/discharging current. According to special request, PWM converter with current mode control is analyzed and designed in this paper. Morever, a loop-locked control strategy is put forward based on dq coordinate conversion to SVPWM converters in the power accumulator battery testing system. low ripple and fast response testing current in a wide adjustable range is achieved, and high power factor is obtained. Considering resonance of LC filter, the passive damping is designed, which is based on the series resistance of capacitor. Simulation results verify the feasibility and validity of this strategy.
Design and experimental characterization of a novel passive magnetic levitating platform
E. Diez-Jimenez,R. Alcover-Sanchez,J.M. Soria,J. Pérez-Aracil,E. Pereira 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.3
This work proposes a novel contactless vibration damping and thermal isolation tripod platform based on Superconducting Magnetic Levitation (SML). This prototype is suitable for cryogenic environments, where classical passive, semi active and active vibration isolation techniques may present tribological problems due to the low temperatures and/or cannot guarantee an enough thermal isolation. The levitating platform consists of a Superconducting Magnetic Levitation (SML) with inherent passive static stabilization. In addition, the use of Operational Modal Analysis (OMA) technique is proposed to characterize the transmissibility function from the baseplate to the platform. The OMA is based on the Stochastic Subspace Identification (SSI) by using the Expectation Maximization (EM) algorithm. This paper contributes to the use of SSI-EM for SML applications by proposing a step-by-step experimental methodology to process the measured data, which are obtained with different unknown excitations: ambient excitation and impulse excitation. Thus, the performance of SSI-EM for SML applications can be improved, providing a good estimation of the natural frequency and damping ratio without any controlled excitation, which is the main obstacle to use an experimental modal analysis in cryogenic environments. The dynamic response of the 510 g levitating platform has been characterized by means of OMA in a cryogenic, 77 K, and high vacuum, 1E-5 mbar, environment. The measured vertical and radial stiffness are 9872.4 N/m and 21329 N/m, respectively, whilst the measured vertical and radial damping values are 0.5278 Nm/s and 0.8938 Nm/s. The first natural frequency in vertical direction has been identified to be 27.39 Hz, whilst a value of 40.26 Hz was identified for the radial direction. The determined damping values for both modes are 0.46% and 0.53%, respectively.