3D Motion Analysis and Musculoskeletal Modeling on Changes in Muscle Length of Lower Limbs for Hemiplegic Walking

Sungjae Hwang,Jongsang Son,Yujin Shin,Jungmi Park,Youngho Kim 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7

Many studies have been unsuccessful to classify biomechanical characteristics of pathological gaits in hemiplegic patients using joint motions of the lower extremity. In this paper, we analyzed changes in muscle length of lower limbs for hemiplegic walking by using the 3D motion analysis and the musculoskeletal modeling to determine gait patterns. Twenty young healthy volunteers and three hemiplegic patients participated in this study. 3D motion analyses were performed by using six infra-red cameras and four force plates. The musculoskeletal model was made based on subjects' anthropometric data and 3D motion capture data. The musculoskeletal model included twelve major lower extremity muscles based on the modified Hill-type muscle model in each lower limb. Results showed that insufficient push-off was found during pre-swing in hemiplegic walking, without showing enough contraction of gastrocnemius and soleus. Excessive ankle dorsiflexion was also found due the contracture of tibialis anterior. Semimembranosus was shown to be tighter and thus knee flexion was larger during loading response than those in the normal subjects. Changes in muscle length of extensor muscles were also very similar to joint motions in the sagittal plane. These results could be very useful to classify and to characterize various abnormal gait patterns.

The Motion Analysis about the Balance Recovery Mechanisms against the Forward Perturbation

Sungjae Hwang,Hueseok Choi,Kisik Tae,Youngho Kim 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7

In this paper, biomechanical aspects of dynamic postural responses against forward perturbations were experimentally determined by simultaneous measurements of joint angles, linear accelerations, EMG activations, CoP movements and ground reaction forces(GRF). The sequence of joint motions due to the forward perturabation was in the order of ankle dorsiflexion, knee flexion and then hip flexion during the second half of the acceleration phase. Forward accerlerations were found both at the heel and the sacrum during the second half of the acceleration phase and the early, constant speed phase. Tibialis anterior(TA) for ankle dorsiflexion and biceps femoris(BF) for knee flexion, the primary muscle to recover balances against the forward perturbation, was activated during the half of acceleration phase. Ankle strategy was used for slow-speed perturbation, but mixed strategy of both ankle and hip used for the fast-speed perturbation. In addition, speed and magnitude of the perturbation influenced the postural response.

Biomechanical Effects of Heel Wedges on the Knee Varus Torque during Walking

Sungjae Hwang,Imsook Jeong,Sunwoo Park,Ohyoun Kwon,Youngho Kim 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7

In the present study, knee varus torque and mediolateral accelerations were compared using the threedimensional motion analysis system and a linear accelerometer in order to determine biomechanical effects of heel wedges during walking. Wedges were inclined with 10° and 15° in medial and lateral directions respectively. Both knee varus torques and mediolateral accelerations showed two distinct positive peaks in loading response and pre-swing. Medial wedges resulted in significantly increased both knee varus torque and lateral acceleration in loading response, compared with barefoot walking (p<0.05). On the other hand, lateral wedges decreased them in loading response (p<0.05). This became more significant in more inclined wedges. However, no significant correlations were found between knee varus torque and lateral acceleration in preswing with respect to the wedge angle. From this study, it was found that a lateral wedge would be helpful to treat osteoarthritis, decreasing knee varus torque in loading response. In addition, lateral acceleration of the knee joint might be an alternative to determine the effect of wedges during walking, instead of measuring knee torque by the three-dimensional motion analysis.

The balance recovery mechanisms against unexpected forward perturbation.

Hwang, Sungjae,Tae, Kisik,Sohn, Ryanghee,Kim, Jungyoon,Son, Jongsang,Kim, Youngho Pergamon Press [etc.] 2009 Annals of biomedical engineering Vol.37 No.8

<P>Falls are one of the main concerns of the elderly. Proper postural adjustments to maintain balance involve the activation of appropriate muscles to produce force and to relocate the center of body mass (CoM). In this study, biomechanical aspects of dynamic postural responses against forward perturbations were experimentally determined by simultaneous measurements of joint angles and EMG activations. Thirteen young and healthy volunteers took turns standing on a flat platform, and were directed to move in the forward direction by an AC servo-motor set at two different speeds (0.1 and 0.2 m/s). Joint motions were recorded, and they followed the sequence of ankle dorsiflexion, knee flexion, and then hip flexion during the later acceleration phase (AP) in order to maintain postural balance against forward perturbation. Tibialis anterior for the ankle dorsiflexion and biceps femoris for the knee flexion were activated during the second half of the AP as the primary muscles to recover balance. In addition, gastrocnemius, which was related to ankle plantarflexion, and rectus femoris, which was related to knee extension, were activated to maintain balance. Movements of the center of plantar pressure and ground reaction forces in fast-speed perturbation were significantly larger than those in slow-speed perturbation. As a result, the ankle strategy was used for slow-speed perturbation, but the mixed strategy consisting of both ankles and hip were used for fast-speed perturbation.</P>

멀티터치를 활용한 한글 입력 시스템의 개발 및 평가

황성재(Sungjae Hwang),김상태(Sangtae Kim),박영우(Youngwoo Park),임창영(Lim Changyoung) 한국HCI학회 2010 한국HCI학회 학술대회 Vol.2010 No.1

모바일 기기에 내장된 자기센서를 이용한 텐져블 컨트롤러의 인식방법

황성재(Sungjae Hwang),안명욱(Myung-wook Ahn),원광연(Kwang-yun Wohn) 한국HCI학회 2013 한국HCI학회 학술대회 Vol.2013 No.1

동적 분석을 위한 펌웨어 리호스팅 기술 소개

황성재(Sungjae Hwang) Korean Institute of Information Scientists and Eng 2024 정보과학회지 Vol.42 No.5

학생간 거리두기를 고려한 교실공간 면적현황 연구

황성재 ( Hwang Sungjae ) 한국공간디자인학회 2021 한국공간디자인학회논문집 Vol.16 No.3

(연구배경 및 목적) 2019년 말부터 COVID-19와 같은 감염병의 세계적 유행과 함께 비대면 소통이 국민들의 주요한 교류·생활 방식으로 부상되었고, 청소년들의 감염 방지를 위해 학교에는 유례없는 큰 변화가 발생하였다. 갑자기 밀려든 새로운 방식의 위기에도 불구하고 교육현장의 교사들은 현시점에 보유한 시설과 장비를 이용하여, 대면·비대면 수업을 진행하였고 교육의 질 향상을 위해 전념하였다. 질병관리청에서는 지역별 감염병의 발병과 확산 추이에 따라 종합적으로 판단하여 5단계의 거리두기 기준 및 조치를 세부적으로 정하고, 교육기관에서는 이에 따라 대면·비대면 수업을 선택적으로 운영하고 있으며, 교실 내에서는 학생들 간의 접촉을 줄이고자 투명 차단막을 설치하거나, 학년별 등교 시점을 주별로 교차시켜 교실 건물과 체육시설의 이용 밀도를 낮게 조정하였다. 하지만 기존의 직접 대면 방식의 교육 효율에 비하여 분명한 한계점이 제기되고 있다. 따라서, 교육품질 향상을 꾀하면서도 방역을 고려한 시설 공간 마련과 운영 방법에 관한 연구와 고찰이 필요하며, 이를 실제 공간에 적용하기 위한 구체적인 근거와 기준이 필요한 것으로 생각한다. 이에 본 연구에서는 교실과 학교의 공간면적을 산정하는데 지표가 될 수 있는 학생 1인당 공간면적의 현황을 고찰하고, 시각화 분석을 통해 개인간 거리 및 면적에 관한 분석을 수행하였다. (연구방법) 교실의 면적은 교육부와 한국교육개발원에서 통계하는 1인당 교사·교지·교수학습공간·학습지원공간 크기와 밀접한 관계를 가지고 있다. 이에 1. 통계자료를 이용한 교수학습 공간 크기와 1인당 공간면적을 분석하였다. 2. 거리두기의 기본이 되는 사람 간의 거리를 방역지침에 따라 적용하기 위한 시각화 분석을 수행하고, 개인 간 거리을 유지하기 위한 최소한의 공간면적을 산출하였다. 이 결과를 토대로 4. 현재 각급 학교 교수학습공간 크기에 대한 개괄적 분석을 실시하였다. (결과) 분석된 결과로서 1인당 교수학습공간면적의 크기가 가장 작은 학제는 유치원으로 3.2㎡이고, 개인간의 거리는 2미터로 나타났다. 유치원의 경우 밀집도 1/3을 유지해도 특목고와 특성화고의 현황 수준보다 작게 나타났다. 전국 초중고등학교의 경우 밀집도 2/3을 유지하면 개인간 거리가 평균 3.1미터로 나타났고, 1/3을 유지하면 4.4미터 가량으로 나타났다. (결론) 같은 반이 동시에 등교하여 하나의 교실을 이용하는 경우 교수학습공간면적의 학생 1인당 점유 공간면적의 크기와 개인간의 거리를 산술적으로 도출하였다. 결론적으로, 학제별 교수학습 공간의 1인당 면적과 거리 현황을 밀집도의 관점에서 분석하여 시설 준비·운영의 근거가 될 수 있도록 하였다. (Background and Purpose) Since the end of 2019, non-face-to-face communication has emerged as a major lifestyle change with the global burst of infectious diseases such as COVID-19, and there has been an unprecedented change in schools to prevent infections of teenagers. The Korea Centers for Disease Control and Prevention set five levels of distance criteria and measures in detail according to the outbreak and spread of infectious diseases by region, educational institutions select face-to-face and non-face classes. However, certain limitations are being raised compared to the existing face-to-face training efficiency. Therefore, it is necessary to research and consider how to prepare and operate a facility space considering quarantine while improving the quality of education, and specific grounds and standards are needed to apply it to the actual space. In this study, the current status of space area per student, which can be an indicator for calculating the space area of classrooms and schools, was reviewed and the analysis of distance and area between individuals was carried out through visualization analysis. (Method) The area of the classroom is closely related to the size of teachers, school grounds, teaching spaces, and learning support spaces per person, which are statistics by the Ministry of Education and the Korea Educational Development Institute. Accordingly, the size of the teaching space and the space area per person were analyzed using statistical data. 2. Visualization analysis was performed to apply distance between persons underlying distance keeping in accordance with quarantine guidelines, and the minimum space area was calculated to maintain distance between individuals. Based on these results, a comprehensive analysis was conducted on the size of the current teaching space at various levels. (Results) As a result of the analysis, the school system with the smallest size of the teaching space per person is kindergarten(3.2㎡), and the distance between individuals is 2m. In the case of kindergartens, even when the running density were one-third, it was smaller than the current level of special purpose high school and specialized high schools. In the case of elementary, middle, and high schools nationwide, the average distance between individuals was 3.1m when the density was maintained at two-thirds, and 4.4m if the density was maintained at one-third. (Conclusions) If the same class goes to school at the same time and uses a single classroom, the size of the occupied space area per student of the teaching space area and the distance between individuals were derived arithmetically. In conclusion, the current status of the area and distance per person of the teaching space for each school system was analyzed from the perspective of density, so that it could be the basis for the preparation and operation of facilities.

클릭 가능한 터치스크린 : 모바일 터치 스크린 인터페이스에서의 클릭 피드백

황성재(Sungjae Hwang),류중희(Jung-hee Ryu) 한국HCI학회 2011 한국HCI학회 학술대회 Vol.2011 No.1

Joint Moments and Lumbar Lordosis during Symmetric Lifting

Seonhong Hwang,Sungjae Hwang,Youngeun Kim,Youngho Kim 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7

In this study, contributions of lower extremity joints and lumbar lordotic angles were investigated for two different symmetrical lifting techniques using the three-dimensional motion analysis: squat and stoop. Joint angles and moments were determined when the lumbar curvature changed from kyphosis to lordosis. Thirteen male volunteers lifted boxes weighing 5, 10 and 15㎏ by both squat and stoop lifting techniques. Results showed that extension moments of hip and ankle joints contributed the most to support the body in squat lifting, and the knee flexion moment played an important role in stoop lifting. There were individual differences in lower extremity joint moments when the lumbar lordotic curve appeared. However, the correlations about angles and moments between lumbar and lower extremity joints could confirmed the results from the support moment analysis. In conclusion, there might be some strategy to minimize mechanical stress on the waist by the change of lordotic curvature in the lumbar spine for the safe lifting technique.