• 대한기계학회논문집
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• 제16권9호
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• pp.1711-1721
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• 1992

본 연구에서는 Nayfeh등과 이원경과 소강영은 조화가진하의 핀과 꺽쇠로 고정 된 보(hinged-clamped beam)의 강제 진동 해석을 통하여 점근적으로 안정한 정상상태 응답이 둘 이상 존재할 수 있음을 알게 되었다. 본 연구에서는 이 경우에 접근적으 로 안정한두 정상상태 응답을 구하고 이들 안정한 해로 각각 흡인되는 초기조건들의 집합인 흡인영역을 보간사상법(interpolated mapping method)과 직접 수치적분에 의해 구한 후 서로 비교하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제20권4호
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• pp.50-58
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• 1996

The torsional vibration of the propulsion shafting system equipped with viscous damper is investigated. The equivalent system is modeled by a two mass softening system with Duffing's oscillator and the vibratory motion is described by non-linear differential equations of second order. The damper casing is fixed at the front-end of crankshaft and the damper's inertia ring floats in viscous silicon fluid inside of the camper casing. The excitation frenquency is proportional to the rotational speed of engine. The steady state response of the equivalent system is analyzed by the computer and for this analyzing, the harmonic balance method is adopted as a non-linear vibration analysis technique. Frequency response curves are obtained for 1st order resonance only. Jump phenomena are explained. The discriminant for the solutions of the steady state response is derived. Both theoretical and measured results of the propulsion shafting system are compared with and evaluated. As a result of comparisions with both data, it was confirmed that Duffing's oscillator can be used in the modeling of the propulsion shafting system attached with viscous damper with non-linear stiffness.

• Journal of Advanced Marine Engineering and Technology
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• 제20권4호
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• pp.372-372
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• 1996

The torsional vibration of the propulsion shafting system equipped with viscous damper is investigated. The equivalent system is modeled by a two mass softening system with Duffing's oscillator and the vibratory motion is described by non-linear differential equations of second order. The damper casing is fixed at the front-end of crankshaft and the damper's inertia ring floats in viscous silicon fluid inside of the camper casing. The excitation frenquency is proportional to the rotational speed of engine. The steady state response of the equivalent system is analyzed by the computer and for this analyzing, the harmonic balance method is adopted as a non-linear vibration analysis technique. Frequency response curves are obtained for 1st order resonance only. Jump phenomena are explained. The discriminant for the solutions of the steady state response is derived. Both theoretical and measured results of the propulsion shafting system are compared with and evaluated. As a result of comparisions with both data, it was confirmed that Duffing's oscillator can be used in the modeling of the propulsion shafting system attached with viscous damper with non-linear stiffness.

• Wind and Structures
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• 제27권5호
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• pp.293-309
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• 2018

The prediction of multimode flutter relies, to a larger extent than bimodal flutter, on accurate modeling of the self-excited forces since it is challenging to perform experimental validation by using aeroelastic tests for a multimode case. This paper sheds some light on the accuracy of predicted self-excited forces by comparing numerical predictions of self-excited forces with measured forces from wind tunnel tests considering the flutter vibration mode. The critical velocity and the corresponding flutter vibration mode of the Hardanger Bridge are first determined using the classical multimode approach. Then, a section model of the bridge is forced to undergo a motion corresponding to the flutter vibration mode at selected points along the bridge, during which the forces that act upon it are measured. The measured self-excited forces are compared with numerical predictions to assess the uncertainty involved in the modeling. The self-excited lift and pitching moment are captured in an excellent manner by the aerodynamic derivatives. The self-excited drag force is, on the other hand, not well represented since second-order effects dominate. However, the self-excited drag force is very small for the cross-section considered, making its influence on the critical velocity marginal. The self-excited drag force can, however, be of higher importance for other cross-sections.

• Steel and Composite Structures
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• 제26권6호
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• pp.673-691
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• 2018

The main goal of this research is to examine the in-plane and out-of-plane forced vibration of a curved nanocomposite microbeam. The in-plane and out-of-plane displacements of the structure are considered based on the first order shear deformation theory (FSDT). The curved microbeam is reinforced by functionally graded carbon nanotubes (FG-CNTs) and thus the extended rule of mixture is employed to estimate the effective material properties of the structure. Also, the small scale effect is captured using the strain gradient theory. The structure is rested on a nonlinear orthotropic viscoelastic foundation and is subjected to concentrated transverse harmonic external force, thermal and magnetic loads. The derivation of the governing equations is performed using energy method and Hamilton's principle. Differential quadrature (DQ) method along with integral quadrature (IQ) and Newmark methods are employed to solve the problem. The effect of various parameters such as volume fraction and distribution type of CNTs, boundary conditions, elastic foundation, temperature changes, material length scale parameters, magnetic field, central angle and width to thickness ratio are studied on the frequency and force responses of the structure. The results indicate that the highest frequency and lowest vibration amplitude belongs to FGX distribution type while the inverse condition is observed for FGO distribution type. In addition, the hardening-type response of the structure with FGX distribution type is more intense with respect to the other distribution types.

• 항공우주기술
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• 제5권2호
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• pp.149-158
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• 2006

분리된 페어링의 동안정 미계수 예측을 위해 기술 및 비용적 측면을 고려하여 어떤 방 법이 가장 적합할지에 대한 검토가 수행되었으며, 탑재물 페어링의 형상적 특성, 계산 조 건, 그리고 요구되는 정확도 등을 고려한 최적의 예측 방법을 선정하였다. 관성 좌표계에 대해 기술된 Euler 방정식을 해석하여 강제조화운동이 가해진 분리 PLF의 비정상 공력계수를 구하였으며, 이를 한 주기 동안 적분하여 동안정 미계수를 산출하였다. 이와 같은 기 법을 적용함으로써 분리된 3차원 PLF 형상에 대해 마하수 0.60~2.00, 받음각 $-180^{\circ}$~$180^{\circ}$ 및 옆미끄럼각 $-90^{\circ}$~$90^{\circ}$에 대하여 동안정 미계수를 얻을 수 있었다.

• The Journal of Korean Physical Therapy
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• 제31권2호
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• pp.122-128
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• 2019

Purpose: This study examined the effects of sagittal spinopelvic alignment on the clinical parameters, motor symptoms, and respiratory function in patients with mild to moderate Parkinson's disease (PD). Methods: This study was a prospective assessment of treated patients (n=28, Hoehn and Yahr (H&Y) stage 2-3) in a PD center. Twenty-eight subjects ($68.5{\pm}5.7yrs$) participated in this study. The clinical and demographic parameters, including age, sex, symptoms duration, treatment duration, and H&Y stage, were collected. Kinematic analysis was conducted in the upright standing posture with a motion capture system. A pulmonary function test (PFT) was performed in the sitting position using a spirometer. The motor symptoms were assessed on part III of the movement disorder society sponsored version of the unified Parkinson's disease rating scale (MDS-UPDRS). SPSS 18.0 was used to analyze the collected data. Results: The exceeding 12 degrees group of the lower trunk showed significantly higher on the clinical parameters than the below 12 degrees group. In addition, the exceeding 12 degrees group of the lower trunk showed a significantly lower forced expiratory volume at one second (FEV1) / forced vital capacity (FVC) (%) and 25-75% forced mid-expiratory flow (FEF) (L/s) than in the below group. On the other hand, there was no difference in the upper trunk and the cervical pelvis between the groups. Conclusion: These findings suggest that the sagittal balance in the lower trunk is related to the clinical parameters and respiratory function, but not the motor symptoms in patients with mild to moderate PD.

• 대한통합의학회지
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• 제8권4호
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• pp.155-161
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• 2020

Purpose : This study was conducted to investigate the effect of positive active pressure technique and active breathing technique on lung function in healthy adults. Methods : In this study, the passive lung expansion technique and active respiration enhancement technique using an air mask bag unit were conducted in 30 normal adults to observe changes in pulmonary function with forced vital capacity (FVC), Forced expiratory volume at one second (FEV1). In order to observe the change in the level of respiratory function, we would like to investigate the peak expiratory flow (PEF) and the forced expiratory flow (FEF 25-75 %). Results : As a result of this study, there was no significant difference in comparison between the passive lung expansion technique and the active breathing enhancement technique (p>.05). The passive lung expansion technique effectively increased the effortful expiratory volume and the median expiratory flow rate of 1 second (p<.05). And the passive lung expansion technique effectively increased the effortless lung capacity and the maximum expiration flow rate (p<.05). Conclusion : The passive lung expansion technique effectively increases the range of motion of the lungs and chest cages, intrathoracic pressure, and elasticity of the lungs, and the active breathing technique increases the muscle functions such as the diaphragm and the biceps muscles. It is expected that it will be able to selectively improve the respiratory function of patients with respiratory diseases or functional limitations as it is found to be effective.

• 인터넷정보학회논문지
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• 제15권3호
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• pp.11-19
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• 2014

내츄럴 유저 인터페이스는 마우스, 키보드, 펜과 마커를 이용하지 않는 신체를 이용한 자연스런 모션 인터페이스이다. 지금까지 대표적인 동작 인식 방법은 마커를 이용하는 방식이었고 그 인식 방법은 각 마커의 좌표를 상대적인 데이터로 입력 받아 데이터베이스에 각 좌표 값을 저장하는 것이었다. 그러나 정확한 동작을 인식하기 위해서는 더 많은 마커들이 필요하고 그 마커들을 붙이는 것과 데이터들을 처리하는 데에 상당한 시간이 걸린다. 또, NUI/NUX 프레임워크를 개발하면서, 가장 중요한 직관성을 배제한 개발로 사용상에 문제가 생겼고 계속해서 사용자에게 암기만을 강요하고 있다. 이 문제를 보완하기 위해, 본 논문에서는 마커를 이용하지 않았고 남녀노소 누구나 다룰 수 있도록 구현했다. 또, 목소리, 신체 동작, 얼굴 표정 등을 동시에 인식하는 멀티모달 NUI/NUX 프레임 워크를 설계했고, 직관적인 손동작을 인식하는 것과 모니터에 그것을 매핑하기 위해 새로운 마우스 이벤트 알고리즘을 제안했다. 우리는 사용자들이 쉽고 직관적으로 핸드마우스 이벤트를 다루도록 구현했다.

• 대한물리의학회지
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• 제11권4호
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• pp.93-103
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• 2016

PURPOSE: The purpose of this study is to determine the effect of therapeutic exercise on pain, range of motion and strength, and balance ability in a patient with an anterior ankle impingement (AAI). METHODS: A-32-year-old male presented limited ankle motion and pain with forced dorsiflexion at both ankle joints. In response, a therapeutic exercise program consisted of ankle joint mobilization, strength exercises using an elastic band, and proprioceptive exercises including semi-squats and a one-legged standing exercise with open and closed eyes. The program was performed for 40 min/day, twice per week, for 8 weeks. Pain, range of motion (ROM), and muscle strength (ankle dorsiflexion, plantarflexion, inversion, and eversion), as well as a one-legged standing test of both ankles, were measured before and after 4 and 8 weeks of therapeutic exercise. RESULTS: VAS decreased in both ankles after 8 weeks of exercise, respectively, compared to baseline levels. Range of motion and strength increased in both ankles for dorsiflexion, plantarflexion, inversion, and eversion after 8 weeks of exercise compared to baseline levels. In addition, the ability to perform a one-legged standing test with eyes opened and closed improved in both legs after 8 week of exercise compared to baseline levels. CONCLUSION: These results suggest that therapeutic exercise improves pain, ROM, muscle strength, and balancing ability in patients with AAI.