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부분적으로 유체가 채워진 원통형 관내의 외팔보 진동특성에 관한 실험적 연구
권대규,유계형,소순선,이성철 전북대학교 공학연구원 ( 구 전북대학교 공업기술연구소 ) 2003 工學硏究 Vol.34 No.-
This paper presents the vibration characteristics of an intelligent cantilever beam in contact with fluid using PZT actuator and PVDF film. The effect of liquid level on free vibration of composite beam in a partially liquid-filled circular cylinder is investigated. The dynamic behaviors of a flexible beam-water interaction system are examined. The coupled system is subject to an undisturbed boundary condition in the fluid domain. In the vibration analysis of wetted beam, the decoupled analyses between beam and fluid have been conventionally employed by considering firstly the composite beam vibration in air and secondly performing the correction taking account for surrounding fluid effects. That is, this investigation was to look at how natural frequencies, mode shapes, and damping are affected by liquid level variations. Using the coupled modal reanalysis method employing the governing equations and the clamped-free and free-free boundary conditions, the vibration analysis of beam in contact with fluid is performed. We also carried out the experimental verification about reliability of theoretical methods to inclusive vibration analysis of the fluid-structure system with PZT actuator and PVDF film. It was found that the coupled natural frequencies decrease with the fluid level for the identical composite beam due to added mass effect.
Revisit of Broden’s View for Intraarticular Calcaneal Fracture
권대규,정진엽,Kyoung Min Lee,Tae Won Kim,성기혁,Dae-Ha Kim,박문석 대한정형외과학회 2012 Clinics in Orthopedic Surgery Vol.4 No.3
Background: This study was performed to investigate the relationship between coronal computed tomography (CT) and Broden’s view in terms of location of the fracture line and fracture pattern. Methods: Forty-five feet of 45 patients with intraarticular calcaneal fractures were evaluated. The mean age of the patients was 46.3 years (standard deviation, 18.1; range, 15 to 80 years), and there were 34 men and 11 women. The Broden’s views were acquired using the ray sum projection, reviewed, and correlated with the coronal CT image to determine the location of the fracture on the posterior facet and fracture pattern described by the Sanders classification. The quantified location of the fracture line was defined as the distance between the medial margin of posterior facet and the fracture line divided by the whole length of the posterior facet, which was expressed as a percentage. Results: The fracture line on the Broden’s view was positioned at 22.3% (standard deviation, 29.6) laterally compared to that on coronal CT (p < 0.01). Although all cases showed posterior facet involvement on the CT scan, the fracture line was positioned lateral to the posterior facet in 6 cases (13.3%) in the Broden’s view. The coronal CT and Broden’s view showed a low level of agreement in the fracture pattern according to the Sanders classification, with kappa values of 0.23. Conclusions: Surgeons should consider that the fracture line on the Broden’s view shows positioning laterally compared to coronal CT and they should consider that the fracture line at the lateral to posterior facet on the Broden’s view might be an intraarticular fracture line. There are some limitations when applying the Sanders classification with the Broden’s view.
가상 자전거 시스템을 이용한 노인의 자세균형 증진에 관한 연구
권대규,윤영일,박용군,김남균,Kwon, Tea-Kyu,Yoon, Young-Il,Piao, Yong-Jun,Kim, Nam-Gyun 대한의용생체공학회 2007 의공학회지 Vol.28 No.5
In this paper, a new rehabilitation training system was developed to improve equilibrium sense of the elderly by combining virtual reality technology with a fixed exercise bicycle. In order to evaluate the effectiveness of the training system, the elderly participated as test subject in the investigation of the influence of different the parameters on postural balance control. We measured three different running modes of virtual bicycle system with two successive sets. The parameters measured were running time, velocity, the weight movement, the degree of the deviation from the road, and the variables about the center of pressure. The repeated training, our results showed that the running capability of the elderly improve compared. In addition, it was found out that the ability of postural control and the equilibrium sense was improved with the presentation of the visual feedback information of the distribution of weight. From the results of this experiment, we showed that our newly developed system might be useful in the diagnosis of equilibrium sense or in the improvement of the sense of sight and, somatic, and vestibular sense of the elderly in the field of rehabilitation training.
권대규,최병용,임숙정,방두열,이성철 전북대학교 공업기술연구소 2001 工學硏究 Vol.32 No.-
This paper presents the active control of a flexible intelligent beam with added mass. The two types of different materials which are the glass fiber reinforced(GFR) thermoplastic composite and the carbon fabric/epoxy(CFE) theromosetting composite, are employed to achieve vibration characteristics according to added mass induced end of composite beam with a distributed PVDF sensor and piezo-ceramic actuator. The PID controllers are employed to achieve vibration suppression in tranisent vibration situations. Simulations and experiments were carried out with the designed controllers in order to demonstrate the suppression efficiency of each controller.