• 대한기계학회논문집A
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• 제38권7호
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• pp.699-709
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• 2014

본 논문에서는 단일윤축 탈선이론을 적용하여 측풍 조건에서 주행 중인 철도차량의 탈선을 예측하는 방법을 제시하였다. 기존 연구에서는 측풍에 의한 탈선은 모두 전복탈선이라고 가정하여 탈선 예측 이론을 개발하였다. 그러나 이러한 가정은 특수한 주행조건하에서 차륜 타고오름 탈선의 가능성을 무시하고 있다. 또 기존의 측풍 탈선 이론은 주행 중 발생하는 차륜-궤도 사이의 마찰력, 동적상호작용과 같은 주행조건이 탈선에 미치는 영향을 고려할 수 없었다. 본 논문의 방법은 차륜-궤도 사이의 동적 영향, 횡가속도 및 켄트 영향, 측풍 영향 등을 동시에 고려할 수 있었다. 본 이론의 결과를 기존 이론 및 시뮬레이션 결과와 비교하여 타당성을 검증하였다.

• 대한물리의학회지
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• 제12권4호
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• pp.147-158
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• 2017

PURPOSE: Balance exercise as well as lower extremity strengthening exercise (LESE) is known to be effective in patients with knee osteoarthritis (KOA). The purpose of this study was to investigate the effectiveness of performing LESE in conjunction with balance exercise on lower extremity function, range of motion, muscle strength, and balance in patients with KOA. METHODS: The subjects of this study were 25 patients with KOA who were recruited and randomly divided into two groups: 1) those who performed LESE with balance exercise; and 2) those who performed only LESE. Both the groups also received general physical therapy and performed aerobic exercise. The interventions were performed 3 times a week for 4 weeks. To determine the effectiveness of the interventions, we measured Western Ontario and MacMaster Universities Arthritis Index (WOMAC) score, numerical rating scale (NRS) score, passive range of motion (PROM), chair stand test (CST), and Berg Balance Scale (BBS) score at the initiation of the interventions and again after 4 weeks, at the time of completion of the interventions. RESULTS: After 4 weeks of the interventions, both the groups showed significantly improved WOMAC (p<.01), NRS (p<.01), PROM (p<.05), CST (p<.05), and BBS (p<.01) scores. However, there was no significant difference between the groups in terms of the clinical outcomes observed. CONCLUSION: These results suggest that the addition of balance exercise to a LESE regimen in patients with KOA did not provide any additional benefit.

• 한국소음진동공학회논문집
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• 제17권7호
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• pp.596-604
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• 2007

이 논문은 후판 환형 디스크의 기하학적인 형상이 래디얼 방향 진동에 의해 방사되는 소음에 미치는 영향을 연구하였다. 디스크의 내경을 고정한 상태에서 두께와 외경을 주어진 범위내에서 변경하면서 이론적인 해를 이용하여 래디얼 모드의 고유진동수와 진동모드의 변화를 검토하였다. 이 결과를 이용하여, 해당 형상을 가진 디스크의 래디얼 방향 고유진동에 의해 발생되는 원격음장, 음향파워 및 방사효율을 계산하였다. 이 결과로부터 고유진동에 의한 음향파워와 방사효율을 최소화할 수 있는 기하학적인 형상을 선택하였다. 마지막으로, 최적화된 디스크의 임의 위치에 단위 하모닉 가진을 가했을 경우에 발생되는 음향파워 및 방사효율 스펙트럼을 구하였으며, 전산해석을 통해 그 정확성을 검증하였다. 이 논문에 소개된 방법을 적용하면 주어진 제한 조건을 만족하면서 목표 주파수 범위내에서 래디얼 진동에 의해 발생되는 소음을 최소화할 수 있는 기하학적인 형상을 간편하고 논리적으로 구할 수 있다.

• 대한한방내과학회지
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• 제22권4호
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• pp.589-599
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• 2001

Objective: This study was carried out to investigate the effects of Hyangsayukgunja-tang extract on indomethacin-induced gastric mucosal lesions of mice. Methods: To evaluate the effects of Hyangsayukgunja-tang extract and Misoprostol, the morphology of gastric mucosa, and the distribution of mucose cells, PNA(Peanut Agglutinin), ICAM(intercellular adhesion molecule), and apoptotic cells were observed. Hyangsayukgunja-tang extract and Misoprostol were intragastric injected to the test groups at hour 72 before and just before indomethacin treatment(HYT-J, HYT-72, M-J, M-72), while the INDO group was injected only with indomethacin and the control group was subcutaneously injected only with saline. Results: The gastric mucosal lesions incresed in the fundus and body of INDO group, but softened in HYT group and M group, the effects were more excellent in the HYT-72, M-72 groups than the HYT-J, M-J groups and in the HYT group than M group. The disappearance of surface and neck mucose cells were shown in INDO group, but softened in HYT group and M group. The mucosal configuration of HYT-72 group was the same as control group. The numerical increase of PNA positive reaction in cytoplasm of perietal cells were appeared in INDO group. The PNA positive reaction in HYT group and Miso-group were shown in surface mucous cells and microvilli of apical surface in chief cells as control group, and were the same as control group in all mucosa of HYT-72 group. The distribution of ICAM positive cells, increased in INDO group, but decreased in M-72 group, and were the same as control group in HYT-72 group. The apoptotic cells, increased noticeably in gastric mucosa of INDO group, decreased in HYT group and M group, and decreased noticeably in HYT-72 group. Conclusions: Hyangsayukgunja-tang extract had excellent effects on indomethacin-induced gastric mucosal lesions.

• 대한한방내과학회지
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• 제38권6호
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• pp.1085-1095
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• 2017

Objectives: The purpose of this study was to investigate the efficacy of Lijin-tang-gamibang on refractory gastroesophageal reflux disease (GERD). Methods: This before-and-after study compared the first medical examination and examination at the end of medical treatment. Twelve refractory GERD patients who visited the Department of Digestive Diseases of Kyung Hee University Korean Medicine Hospital from August 14th, 2017 to October 14th, 2017, were treated with Lijin-tang-gamibang for four consecutive weeks. The clinical characteristics of refractory GERD and the efficacy of herbal medical treatment was assessed by questionnaires, the Nepean Dyspepsia Index-Korean version (NDI-K), the Korean Gastrointestinal Symptom Rating Scale (KGSRS), the Numerical Rating Scale (NRS), the Korean version of the Perceived Stress Scale (KPSS-10), the Qi Stagnation Questionnaire (QSQ), the Spleen Qi Deficiency Questionnaire (SQDQ), and the Patient Global Impression of Change (PGIC). Prolonged effects were reported upon the follow-up telephone survey two weeks after treatment. Results: After treatment with the herbal medicine Lijin-tang-gamibang, the clinical characteristics of 12 refractory GERD patients were improved, especially in terms of the most common symptoms of acid regurgitation and heartburn. Each symptom score of NDI-K, KGSRS, NRS, SQDQ, and PGIC showed significant advances. Prolonged effects were reported in NDI-K, NRS and PGIC questionnaires two weeks after treatment. Conclusions: These results suggest that Lijin-tang-gamibang is an effective treatment for refractory GERD.

• International Journal of Vascular Biomedical Engineering
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• 제1권1호
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• pp.13-23
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• 2003

Backgrounds: The present study in angulated coronary stenosis was to evaluate the influence of velocity and wall shear stress (WSS) on coronary atherosclerosis, the changes of hemodynamic indices following coronary stenting, as well as their effect of evolving in-stent restenosis using human in vivo hemodynamic parameters and computed simulation quantitatively and qualitatively. Methods: Initial and follow-up coronary angiographies in the patients with angulated coronary stenosis were performed (n=80). Optimal coronary stenting in angulated coronary stenosis had two models: < 50 % angle changed(model 1, n=43), > 50% angle changed group (model 2, n=37) according to percent change of vascular angle between pre- and post-intracoronary stenting. Flow-velocity wave obtained from in vivo intracoronary Doppler study data was used for in vitro numerical simulation. Spatial and temporal patterns of velocity vector and recirculation area were drawn throughout the selected segment of coronary models. WSS of pre/post-intracoronary stenting were calculated from three-dimensional computer simulation. Results: Follow-up coronary angiogram demonstrated significant difference in the percent of diameter stenosis between two groups (group 1: $40.3{\pm}30.2$ vs. group 2: $25.5{\pm}22.5%$, p<0.05). Negative WSS area on 3D simulation, which is consistent with re-circulation area of velocity vector, was noted on the inner wall of post-stenotic area before stenting. The negative WSS was disappeared after stenting. High spatial and temporal WSS before stenting fell into within physiologic WSS after stenting. This finding was prominent in Model 2 (p<0.01) Conclusions: The present study suggests that hemodynamic forces exerted by pulsatile coronary circulation termed as WSS might affect on the evolution of atherosclerosis within the angulated vascular curvature. Moreover, geometric change, such as angular difference between pre / post-intracoronary stenting might give proper information of optimal hemodynamic charateristics for vascular repair after stenting.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.8-16
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• 2007

Finite element analysis (FEA) is an effective means for the analysis of bioelectromagnetism. It has been successfully applied to various problems over conventional methods such as boundary element analysis and finite difference analysis. However, its utilization has been limited due to the overwhelming computational load despite of its analytical power. We have previously developed a novel mesh generation scheme that produces FE meshes that are content-adaptive to given MR images. MRI content-adaptive FE meshes (cMeshes) represent the electrically conducting domain more effectively with far less number of nodes and elements, thus lessen the computational load. In general, the cMesh generation is affected by the quality of feature maps derived from MRI. In this study, we have tested various feature maps created based on the improved differential geometry measures for more effective cMesh head models. As performance indices, correlation coefficient (CC), root mean squared error (RMSE), relative error (RE), and the quality of cMesh triangle elements are used. The results show that there is a significant variation according to the characteristics of specific feature maps on cMesh generation, and offer additional choices of feature maps to yield more effective and efficient generation of cMeshes. We believe that cMeshes with specific and improved feature map generation schemes should be useful in the FEA of bioelectromagnetic problems.

• Smart Structures and Systems
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• 제4권3호
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• pp.343-365
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• 2008

In this study, the frequency domain method which utilizes the evaluation of changes in the structural mode shape is adopted to identify regions which contain localized damages. Frequency response function (FRF) values corresponding to the modal frequency, analogous to the mode shape coefficients, are used since change in natural frequency of the system is usually insignificant for localized damage. This method requires only few sensors to obtain the dynamic response of the structure at specific locations to determine the FRF via fast-Fourier transform (FFT). Numerical examples of an aluminum plate, which includes damages of varying severity, locations and combinations of multiple locations, are presented to demonstrate the feasibility of the method. An experimental verification of the method is also done using an aluminum plate with two different degrees of damage, namely a half-through notch and a through notch. The inconsistency in attaining the FRF values for practical applications due to varying impact load may be overcome via statistical averaging, although large variations in the loading in terms of the contact duration should still be avoided. Nonetheless, this method needs special attention when the damages induce notable changes in the modal frequency, such as when the damages are of high severity or cover more extensive area or near the boundary where the support condition is modified. This is largely due to the significant decrease in the frequency term compared to the increase in the vibration amplitude. For practical reasons such as the use of limited number of sensors and to facilitate automation, extending the resolution of this method of identification may not be efficient. Hence, methods based on wave propagation can be employed as a complement on the isolated region to provide an accurate localization as well as to trace the geometry of the damage.

• 한국터널지하공간학회 논문집
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• 제6권3호
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• pp.183-197
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• 2004

최근 3차원 절대 계측 기술의 발달을 통해 터널에서의 3차원 계측 기술의 도입 및 결과의 활용에 대한 연구가 다양하게 시도되고 있다. 이러한 계측분석을 통하여 이방성 암반에서 터널 굴착 시 암반의 구조적 거동 및 영향이 파악될 수 있으며, 그에 따른 적절한 지보도 결정되어 질 수 있다. 터널 축에 대하여 서로 다른 연약대 특성, 두께, 방향성을 가지는 암반에서의 굴착에 영향을 확인하기 위해 3차원 해석이 수행되었으며, 내공변위의 function parameter가 계산되었다. 수치해석 결과는 오스트리아 알프스 산악터널의 비균질한 암반에서의 계측 결과와 비교분석 되었다. 현장의 계측결과와 수치해석 결과의 상관도가 높게 나타났으며, 이를 토대로 function parameter의 변화를 통해 막장 전방의 지반을 예측하는 것이 가능한 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.415-424
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• 2020

Recently, many structural damage detection (SDD) methods have been proposed to monitor the safety of structures. As an important modal parameter, mode shape has been widely used in SDD, and the difference of vectors was adopted based on sensitivity analysis and mode shapes in the existing studies. However, amplitudes of mode shapes in different measured points are relative values. Therefore, the difference of mode shapes will be influenced by their amplitudes, and the SDD results may be inaccurate. Focus on this deficiency, a multi-strategy SDD method is proposed based on the included angle of vectors and sparse regularization in this study. Firstly, inspired by modal assurance criterion (MAC), a relationship between mode shapes and changes in damage coefficients is established based on the included angle of vectors. Then, frequencies are introduced for multi-strategy SDD by a weighted coefficient. Meanwhile, sparse regularization is applied to improve the ill-posedness of the SDD problem. As a result, a novel convex optimization problem is proposed for effective SDD. To evaluate the effectiveness of the proposed method, numerical simulations in a planar truss and experimental studies in a six-story aluminum alloy frame in laboratory are conducted. The identified results indicate that the proposed method can effectively reduce the influence of noises, and it has good ability in locating structural damages and quantifying damage degrees.