• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.11
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• pp.1105-1110
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• 2012

The spine is one of the most important skeletal joints, and it strongly affects the health of the musculoskeletal system. A normal spine has an S-shape, and it is very important to maintain this shape. Recently, spinal diseases such as low back pain have increased rapidly, especially among the elderly. Some of these diseases are caused by congenital spinal disorders and sporting and accident injuries as well as by bad postures. Improper spinal postures could generate excessive disc pressure, which is related to degeneration and pain. Therefore, in this study, we investigated the three-dimensional kinematic parameters of the thoraco-lumbar joint in several bad postures using a motion capture analysis technique. Different bad postures created a significant amount of flexion/extension, side bending, and axial rotation angle compared with neutral postures. Further study is necessary to investigate the disc pressure and ligament force due to the increase in joint rotation from the bad postures.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.609-618
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• 2015

This paper discusses the attitude determination of the CNUSAIL-1 cube-satellite. The primary mission of the CNUSAIL-1 is sail deployment and operation in low Earth orbit, and the secondary mission is to look into influence of the sail deployment on satellite attitude and orbit. The attitude determination strategy is proposed depending on three mission phases, and its performance and applicability are verified through numerical simulations. This study considers the following sensors: Sun sensors and a three-axis magnetometer as attitude reference sensors, and a three-axis MEMS gyroscope as an inertial attitude sensor. Because sensors used for cube satellites have relatively low performances and worse noise characteristics, an Extended Kalman filter (EKF) is applied to attitude determination. Additionally, it has the merits to deal with the Gaussian noises and to predict the attitude even with no measurements from reference attitude sensors, especially in the eclipse of the cube satellite. The performance of the EKF is compared to a deterministic attitude determination technique, QUEST(QUaternion ESTimation).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.1
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• pp.36-41
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• 2009

In general, accurate attitude information is essential to perform the mission. Two algorithms are well-known to determine the attitude through two or more vector observations. One is deterministic method such as TRIAD algorithm, the other is optimal method such as QUEST algorithm. This Paper suggests the idea to improve performance of the TRIAD algorithm and to determine the attitude by combination of different sensors. First, we change the attitude matrix to Euler angle instead of using orthogonalization method and also use covariance in place of variance, then apply an unbiased minimum variance formula for more accurate solutions. We also suggest the methodology to determine the attitude when more than two measurements are given. The performance of the Averaging TRIAD algorithm upon the combination of different sensors is analyzed by numerical simulation in terms of standard deviation and probability.

• Physical Therapy Korea
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• v.2 no.2
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• pp.1-8
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• 1995

이 논문의 주목적은 정상인을 대상으로 각기 다른 3가지의 (체중의 1.5 %, 3.0 %, 9.0 %) 부하를 통해서 자세의 불균형을 유발시켰을 때 나타나는 postural movement patterns을 기술하기 위한 연구이다. 연구대상의 허리중심에 체중부하를 주어 균형이 뒤로 이동하게 하여, surface EMG(표면 근전도)를 통하여 Tibialis anterior(Ta), Gastrocnernius(Gc), Quadriceps femoris(Qc), Hamstring(Ha), Rectus abdominalis(Ab)와 Paraspinalis(Pa) 근육들의 motor recruitment pattern(운동회집형태)를 측정하였다. 그리고 비디오 촬영은 고관절, 슬관절, 족관절의 움직임을 보기 위해 사용하였다. 특히 근전도 (EMG)는 자세반응 검사에 있어 첫 근반응(근수축) 경과시간(FR)과 분절간격간의 (ID)시간을 조사하는데 사용되었다. 이 연구의 결과는 4가지 중요한 사실을 전해주고 있다. 첫 번째로서, 연구대상자에게 체중의 1.5 %의 부하를 적용하였을 때 Ta가 가장 먼저 수축을 시작하였고(FR:$88{\pm}19.4$ ms) 발목과 대퇴사이의 분절 간격간(ID)의 평균은 +9.3 ms였다. 또한 족관절의 변화가 가장 뚜렷하여 Nashner(1985)의 족기전을 뒷받침하고 있다. 둘째로는 연구대상자에게 체중의 3.0 %의 부하를 주었을 때 Qc와 Ab근육이 원위부에서 근위부 순서로 수축하였고, 첫 번째 근육수축시간은 ($82{\pm}39.2$ ms)였다. 그리고 이때 분절간격의 평균은 +8.3ms 이였고 Ta는 거의 반응하지 않았다. 족관절과 슬관절에 비해 고관절의 변화가 가장 현저하게 나타났고, 이 또한 Nashner의 고관절 기전과 같은 현상을 보였다. 셋째로 연구 대상자에게 체중의 9.0 % 부하를 허리에 적용하였을 때 근수축은 근위부에서 원위부 순서를 이루어졌다. 즉 Ab,Qc, Ta, Ps순으로 근수축 되었다. Ab가 처음으로 수축하여 첫 반응(FR)은 $73{\pm}3.2$ ms 이였고 슬관절과 고관절의 변화가 가장 뚜렷하였다. 넷째로 연구 대상자에게 체중의 9.0 %부하를 적용하였을 때, 균형을 잡기 위해 뒷걸음치는 것이 관찰되었고 이때 근수축 순서는 Ta,Ab.Ps,Qc,Hs였다. 이 결과는 Nasher의 결과와 불일치하였다. 이상과 같은 결과에서 연구대상자의 자세운동형태(postural movement patterns)는 각기 다른 부하 정도와 시간에 따라 합성적으로 이루어지는 것으로 보여졌다. 특히, 자세운동형태는 부하의 적용위치와 연구대상자의 최근의 경험에 영향을 받은 것으로 밝혀졌다. 결론적으로 말하면 자세운동형태는 중앙신경계의 제한적(한정적) 명령 시스템에 의해서 움직임(movement)이 발생하기 전에 조직된다는 Nashner의 가설을 뒷받침하였다.

• Journal of the Korea Society of Computer and Information
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• v.19 no.8
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• pp.119-127
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• 2014

TIn this paper, Hemiplegic patients have gait characteristics different from normal persons. This paper presents a posture measuring and display system reflecting their characteristics. Patients wear 3 sensor modules on thigh, calf and foot. To enhance measuring precision of each sensor module, 3D accelerometer and 3D gyroscope are combined. Gait posture is displayed in 3D by modeling thigh, calf and foot as connected 3D objects based on data of the sensor modules. For convenience in inspecting unusual gait posture of hemiplegic patients, any view angle of the 3D display can be selected. In addition, the current gait phase of RLA(Rancho Los Amigos) gait cycle is determined and displayed in real-time by utilizing the posture information, The phase sequence and duration of each phase can be used in evaluating gait quality of patients.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.2
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• pp.106-113
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• 2017

Attitude determination algorithms for aircraft and land vehicles use earth gravitational vector and geomagnetic vector; hence, magnetometers and accelerometers are employed. In dynamic situation, the output from accelerometers includes not only gravitational vector but also motional acceleration, thus it is hard to determine accurate attitude. The acceleration compensation method treated in this paper solves the problem to compensate the specific force vector for motional acceleration calculated by a GPS receiver. This paper analyzed the error from the corrected vector regarded as a constant by conventional acceleration compensation method, and improve the error by rederivation from measurements. The analyzed error factors and improvements by the proposed algorithm are verified by computer simulations.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.3
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• pp.369-375
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• 2010

Since multi-view images can be utilized for 3D visualization and surveying as well, a system calibration is an essential procedure. The cameras in the system are mounted to the holder and their locations and attitudes are relatively fixed. Therefore, the locations and the attitudes of the perspective centers of the four oblique looking cameras can be calculated using the location and attitude of the nadir looking camera and the boresight values between the cameras. In this regard, this research is focusing on the analysis of the relative location and attitude between the nadir and oblique looking cameras based on the results of the exterior orientation parameters after the aerial triangulation of the real multiview images. We acquired high standard deviations of the relative locations between the nadir and oblique cameras. Standard deviations of the relative attitudes between the cameras were low when only the exterior orientations of the oblique looking cameras were allowed to be adjusted. Moreover, low standard deviations of the relative attitudes came when we considered not all the exterior orientations of the cameras but the attitudes of them only.

• Journal of Digital Convergence
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• v.11 no.10
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• pp.549-556
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• 2013

In this study, we investigated the effects of stretching and movement with mobilization in lunge position on the muscle activity of the lower limb and limited of stability in chronic stroke patients with hemiplegia. Sixteen subjects were randomly selected and classified into the experimental and control groups. The experimental group performed self stretching exercises in the lunge position, and in the control group performed movement with mobilization in the lunge position. The interventions were conducted for 20 min, 5 times a week for 8 weeks. Statistical analyses were performed using repeated ANOVA. The analysis results showed no statistically significant between-group differences with respect to the muscle activity(%MVIC;maximum voluntary isometric contraction) of lower limb and limited of stability(LOS)(p>.05). However, statistically significant within-group differences were observed in the maximum voluntary isometric contraction and limited of stability for both the groups (p<.05). Therefore, self stretching in the lunge position is considered to have positive influences on the muscle strength and balance in stroke patients with hemiplegia.

• Journal of the Korea Society of Computer and Information
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• v.28 no.8
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• pp.87-93
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• 2023

In this paper, we propose a system that accurately and efficiently determines forward head posture based on network learning by analyzing the user's skeletal posture. Forward head posture syndrome is a condition in which the forward head posture is changed by keeping the neck in a bent forward position for a long time, causing pain in the back, shoulders, and lower back, and it is known that daily posture habits are more effective than surgery or drug treatment. Existing methods use convolutional neural networks using webcams, and these approaches are affected by the brightness, lighting, skin color, etc. of the image, so there is a problem that they are only performed for a specific person. To alleviate this problem, this paper extracts the skeleton from the image and learns the data corresponding to the side rather than the frontal view to find the forward head posture more efficiently and accurately than the previous method. The results show that the accuracy is improved in various experimental scenes compared to the previous method.

• Journal of Internet of Things and Convergence
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• v.9 no.6
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• pp.51-56
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• 2023

Hand gesture recognition is an essential technology for the people who have difficulties using spoken language to communicate. Electromyogram (EMG), which is often utilized for hand gesture recognition, is expected to have difficulties in hand gesture recognition because its people's movements varies depending on prior postures, but the study on this subject is rare. In this study, we conducted tests to confirm if the prior postures affect on the accuracy of gesture recognition. Data were recorded from 20 subjects with different prior postures. We achieved average accuracies of 89.6% and 52.65% when the prior states between the training and test data were unique and different, respectively. The accuracy was increased when both prior states were considered, which confirmed the need to consider a variety of prior states in hand gesture recognition with EMG.