• The Journal of Korean Physical Therapy
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• 제33권5호
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• pp.217-223
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• 2021

Purpose: This study sought to identify the effects of coordinative locomotor training (CLT) using elastic bands on the flexibility and body alignment of right-handed baseball players in elementary school. Methods: The subjects were 20 instructed right-handed baseball players in elementary school. They were classified into the experimental group with 10 players (n=10) to be given coordinative locomotor training using elastic bands and the control group with 10 players (n=10). Flexibility was measured by the sit and reach exercise. Body alignment was measured using formetric 4D method to measure the trunk imbalance angle (TI), trunk torsion angle (TT), pelvic tilt angle (PTi), pelvic torsion angle (PTo), pelvic rotation angle (PR), kyphotic angle (Ky), and lordotic angle (Lo). Results: There was a significant increase in the flexibility within the experimental group (p<0.05). after the intervention. There was also a significant increase in the difference between the experimental group and the control group (p<0.05). There was a significant decrease in PR during body alignment in the experimental group after intervention (p<0.05). An analysis of the differences between groups showed a significant decrease in the PR of the experimental group compared to the control group (p<0.05). Conclusion: These findings show that coordinative locomotor training using elastic bands would be effective for enhancing the flexibility and pelvic rotation of elementary school right-handed baseball players.

• Wind and Structures
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• 제33권6호
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• pp.447-462
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• 2021

High spatial and temporal surface pressure measurements were carried out in the state-of-the-art tornado simulator, the Wind Engineering, Energy and Environment (WindEEE) Dome, to explore the characteristics of stationary and translating tornado-like vortices (TLV) for a wide range of swirl ratios (S=0.21 to 1.03). The translational speed of the TLV and the surface roughness were varied to examine their effects on tornado ground pressures, wandering, and vortex structure. It was found that wandering is more pronounced at low swirl ratios and has a substantial effect on the peak pressure magnitude for stationary TLV (error percentage ≤ 35%). A new method for removing wandering was proposed which is applicable for a wide range of swirl ratios. For translating TLV, the near-surface part lagged behind the top of the vortex, resulting in a tilt of the tornado vertical axis at higher translating speeds. Also, a veering motion of the tornado base towards the left of the direction of the translation was observed. Wandering was less pronounced for higher translation speeds. Increasing the surface roughness caused an analogous effect as lowering the swirl ratio.

• 센서학회지
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• 제31권2호
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• pp.96-101
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• 2022

As the elderly population gradually increases, the risk of fatal fall accidents among the elderly is increasing. One way to cope with a fall accident is to determine the fall direction before impact using a wearable inertial measurement unit (IMU). In this context, a previous study proposed a method of classifying fall directions using a support vector machine with sensor velocity, acceleration, and tilt angle as input parameters. However, in this method, the IMU signals are processed through several processes, including a Kalman filter and the integration of acceleration, which involves a large amount of computation and error factors. Therefore, this paper proposes a machine learning-based method that classifies the fall direction before impact using IMU raw signals rather than processed data. In this study, we investigated the effects of the following two factors on the classification performance: (1) the usage of processed/raw signals and (2) the selection of machine learning techniques. First, as a result of comparing the processed/raw signals, the difference in sensitivities between the two methods was within 5%, indicating an equivalent level of classification performance. Second, as a result of comparing six machine learning techniques, K-nearest neighbor and naive Bayes exhibited excellent performance with a sensitivity of 86.0% and 84.1%, respectively.

• The Journal of Korean Physical Therapy
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• 제36권1호
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• pp.1-8
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• 2024

Purpose: The purpose of this study was to determine the effect of proprioceptive neuromuscular facilitation (PNF) abdominal muscle strengthening exercise on the activity, posture, and body function of clients with abdominal muscle weakness after cesarean section. Methods: PNF abdominal muscle strengthening exercise was applied to one patient with abdominal muscle weakness after cesarean section. PNF abdominal muscle strengthening exercise was applied five times a week for four weeks. The 5-time supine-to-long sitting test (5-TSLST) and supine-to-stand test (SST) were used to measure activity, and the pelvis tilt angle test (PTAT) and anterior head translation test (AHTT) were used to measure posture. Body function was assessed using the transverse abdominis muscle strength test (TAMST), the internal oblique and external oblique muscle strength test (IOEOMST), and the rectus abdominis muscle strength test (RAMST). Results: Activity, posture, and body function were improved post-intervention. Conclusion: The study verified that PNF abdominal muscle strengthening exercises are effective when applied to patients with abdominal muscle weakness after cesarean section. The findings of this study provide useful data for future interventions in patients with abdominal muscle weakness after cesarean section.

• Journal of Advanced Marine Engineering and Technology
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• 제37권4호
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• pp.368-377
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• 2013

대형디젤기관 배기가스 저감용 Urea-SCR 시스템은 높은 NOx 저감율을 보이는 반면, 높은 관통도를 갖는 요소수가 벽면 충돌 후 증발하지 못하고 벽면에 머물게 되어 우레아염을 형성한다. 우레아염 생성 방지를 위한 방안으로 벽면유동 형성을 촉진하기위한 믹서-하우징 조립체의 형상 최적화와 관련된 실험적 연구가 수행되었다. 하우징 경사각 변화 및 믹서 설치위치에 따라 벽면유동의 증가 가능성이 hot-wire 시스템을 이용하여 조사되었다. 벽면 유동은 하우징 경사각 및 믹서 설치 위치에 큰 영향을 받으며, 하우징 경사각이 있고 믹서가 하우징 후단에 설치될 때 벽면유동이 향상되는 것을 알 수 있었다.

• 한국광학회지
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• 제21권4호
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• pp.151-160
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• 2010

줌렌즈에서 특정 렌즈군을 이동하여 손떨림 보정을 하는 광학적 방법에서는 광학계 설계단계에서 디센터(decenter)를 고려하여 설계한다. 이 때 여러 가지 광학설계 소프트웨어들은 디센터를 포함한 비대칭 오차요인이 있는 경우에 여러 가지 광학 성능들을 쉽게 계산할 수 있지만, 편심 광학계에 대한 정확한 분석이 부족하여 종수차 계산시에는 일부 계산오차가 생긴다. 특히 왜곡의 경우에는 비정상적으로 계산되는데, 이는 비대칭 오차요인이 있는 편심 광학계에서는 근축광선 추적이 제대로 되지 않기 때문이다. 본 논문에서는 이러한 손떨림으로 인한 디센터나 틸트(tilt)와 같은 비대칭 요인이 발생하는 줌렌즈에서 편심 광학계에 대한 근축광선 추적식을 새로이 유도하고, 이를 이용하여 비대칭 요인을 갖는 결상계의 종수차를 정확히 계산하는 방법을 제안한다. 이러한 편심 광학계에 대한 종수차 계산 방법은 줌렌즈의 손떨림 보정에 실제로 사용할 수 있다.

• 한국항공우주학회지
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• 제49권2호
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• pp.107-120
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• 2021

전기동력 분산추진 비행체는 다수의 프로펠러로 인하여 복잡한 프로펠러 후류 유동 및 기체와의 상호간섭이 발생한다. 이에 따라 초기설계 단계에서는 다양한 형상과 비행 조건에 대하여 프로펠러 구동 효과를 반영한 신속 공력 및 하중 해석이 요구된다. 본 연구에서는 프로펠러 효과를 고려할 수 있는 패널 기반의 효율적인 공력해석 기법을 개발, 검증하였다. Actuator Disk Theory(ADT)에 기반하여 프로펠러 후류 영역의 유도 속도장을 계산하고, 이를 3차원 정상 용출-중첩 패널기법의 비행체 표면 경계조건에 반영하였다. 한국항공우주연구원의 Quad Tilt Propeller(QTP) 비행체 단독 프로펠러와 선행 실험 연구의 프로펠러-날개 형상을 벤치마크 문제로 선정하여 해석을 수행하였다. Actuator 기법 기반의 전산유체역학(CFD) 결과와의 비교를 통해 프로펠러의 후류 속도장과 프로펠러 구동에 따른 날개의 공력하중 분포 변화를 검증하였다. 자율비행 개인용 항공기(Optional Piloted PAV, OPPAV)와 QTP 공력해석에 기법을 적용하고, CFD와의 해석 소요 시간 및 결과 비교, 분석을 통해 기법의 실용성과 타당성을 확인하였다.

• 한국엔터테인먼트산업학회논문지
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• 제14권3호
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• pp.383-392
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• 2020

이 연구는 엉치엉덩관절 통증환자에게 관절가동술, 깔창착용 보행훈련, 그리고 관절가동술과 깔창착용 보행훈련 중재를 실시하고 환자의 통증, 골반 각 및 족저압에 대한 효과를 비교하였다. 무작위로 24명의 대상자를 관절가동술군(n=8), 깔창착용보행훈련군(n=8) 또는 관절가동술과 깔창착용보행훈련군(n=8)으로 배정하여, 하루에 30분씩, 일주일에 2번씩 4주 동안 중재하였다. VAS를 사용하여 통증을 평가하고 골반 각도를 Palpation Meter 사용하여 측정하였고, 족저압 (전 / 후비)을 Gateview AFA-50을 사용하여 측정하였다. 모든 측정은 중전·중재 4주 후에 실시하였다. 모든 그룹은 그룹 내 전·후 비교에서 유의한 통증 감소를 보였다(p<.01). 골반 각도에서 관절가동술군은 전방 기울기에서만 통계적으로 개선되었고, 관절가동술과 깔창착용 보해훈련군은 앞쪽 및 뒷쪽기울임 모두에서 통계적으로 유의미한 개선을 보였으며(p<.01), 깔창착용 보행훈련군은 통계적으로 유의한 변화가 없었다(p>.05). 또한 관절가동술과 깔창착용 보행훈련군은 족저압에서 유의한 차이를 나타냈다(p<.01). 모든 중재는 엉치엉덩관절 통증환자의 통증개선에 효과가 있었으며, 관절가동술과함께 깔창착용 보행훈련을 한 군이 골반각도와 족저압에 가장 효과적이었다. 이 연구는 엉치엉덩관절통증이 있는 환자뿐만 아니라 만성 허리통증 및 족저압 입력 문제가 있는 환자의 부상 예방, 자세교정, 그리고 보행훈련을 위한 기초자료가 될 것으로 사료된다.

• 대한통합의학회지
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• 제11권4호
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• pp.269-279
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• 2023

Purpose : The most effective intervention for flat foot is strengthening exercises for the intrinsic and extrinsic of the foot. Additionally, visual feedback is necessary for movement accuracy. However, the effectiveness of the intervention when combined with visual feedback was not revealed. To confirm this, the research was to investigate the effect of visual feedback and a complex exercise program on navicular bone height, plantar pressure, and lower extremity alignment. Methods : The twenty eight adult men and women with flat foot were randomly assigned to group 1 (n=14) and group2 (n=14), group1 performed complex exercises with visual feedback, and group 2 performed only complex exercises. Both groups performed a 40 minute compound exercise program three times a week. Navicular drop test, plantar pressure test, and lower extremity alignment test were performed equally in both group. Results : As a result of comparing the change in navicular height within the group according to the intervention, both groups showed a significant difference before and after the exercise (p>.05). There was not significant difference comparing the difference between the groups in the navicular height (p>.05). Comparing the change in plantar pressure within groups, there was not significant difference in the change in plantar pressure in both groups (p>.05). Coparing the difference before and after exercise between groups, there was not significant plantar pressure (p>.05). Comparing the change in leg alignment within the group, there was a significant difference in the change in ankle before and after exercise in group 1 (p<.05), but there was not significant difference in group 2. There was not significant difference in pelvic tilt and knee tilt before and after exercise in both groups (p>.05). Comparing the before and after exercise difference between groups, there were not significant in all variables of leg alignment (p>.05). Conclusion : The results of this study showed that complex exercise applied to patients with flat foot were effective in increasing the height of the navicular bone and ankle angle, but there was no effect due to visual feedback.

• International Journal of Precision Engineering and Manufacturing
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• 제1권1호
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• pp.98-105
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• 2000

The projectors using liquid crystal display(LCD) have faults such as low optical efficiency, low brightness and even heat generation. To solve these problems reflective-type spatial light modulators based on MEMS (Microelectromechanical Systems) technology have emerged. Digital Micromirror DeviceTM(DMDTM), which was already developed by Texas Instruments Inc., and Thin-film Micromirror ArrayTM(TMATM), which has been recently developed by Daewoo Electronics Co., are the representative examples. The display using TMATM has particularly much higher optical efficiency than other projectors. But the micromirrors manufactured by semiconductor processes have inevitable distortion because of the limitations of the manufacturing processes, so that the distortions of their surfaces have great influence on the optical efficiency of the projector. This study investigated the effects of mirror flatness on the optical performance, including the optical efficiency, of the TMATM projector. That is to say, as a part of the efforts to enhance the performance of the TMATM projector, how much influence the form errors of a micromirror surface exert on the optical efficiency and the modulation of gray scale of the projector were analyzed through a pertinent modeling and simulations.