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Identification of Flexion Withdrawal Reflex Using Linear Model in Spinal Cord Injury
Yongchul Kim,Youngil Youm 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.8
The aim of this study was to identify the characteristics of the flexion withdrawal reflex modulated by the hip angle and hip movement in spinal cord injury (SCI). The influence of the hip position and passive movement were tested in 6 subjects with chronic SCI. Each subject placed in a supine position and lower leg was fixed with the knee at 5~45 degree flexion and the ankle at 25~40 degree plantar flexion. A train of 10 stimulus pulses were applied at 200 ㎐ to the skin of the medial arch to trigger flexion reflexes. From results of the regression analysis, static properties of normalized muscle activation of flexor muscles have the linear relationship with respect to hip angle (P<0.05). In order to verify the neural contribution of flexion reflex, we compared the static and dynamic gains of estimated muscle activations with measured EMG of ankle flexor muscle. Form this study, we postulate that the torque and muscle response of flexion withdrawal reflex have linear relationship with hip angle and angular velocity.
Effects of taper and set-back on wind force and wind-induced response of tall buildings
Kim, Yongchul,Kanda, Jun Techno-Press 2010 Wind and Structures, An International Journal (WAS Vol.13 No.6
Advances in structural materials and construction methods have resulted in flexible and light tall buildings, making an assessment of structural safety during strong wind and serviceability/habitability during comparable medium/weak wind important design criteria. So far, lots of studies on suppressing the wind-induced responses have been carried out for tall buildings with aerodynamic modification. Most of the studies on aerodynamic modification have forced on the corner modification, while the studies on taper and set-back are limited. Changes of sectional shape through taper and set-back can modify the flow pattern around the models, encouraging more 3-dimensionalities, which results in reducing the wind-induced excitations. This paper discusses the characteristics of overturning moments and wind-induced responses of the tall buildings with height variations. The reduction of mean along-wind and fluctuating across-wind overturning moments are apparent in the suburban area than in urban area. A series of the response analyses, the rms displacement responses of the tall buildings with height variations are reduced greatly, while the rms acceleration responses are not necessarily reduced, showing dependences on wind direction.
Stereoselective Synthesis and Osteogenic Activity of Subglutinols A and B
Kim, Hyoungsu,Baker, Joseph B.,Lee, Su-Ui,Park, Yongho,Bolduc, Kyle L.,Park, Hyung-Bae,Dickens, Marina G.,Lee, Dong-Sup,Kim, Yongchul,Kim, Seong Hwan,Hong, Jiyong American Chemical Society 2009 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.131 No.9
Movement Analysis of Elderly People during Ingress/Egress from Different Seat Heights
Yongchul Kim 대한인간공학회 2011 大韓人間工學會誌 Vol.30 No.5
Objective: The aim of this study was to investigate the influence of seat heights for optimizing the ingress/egress performance in the elderly people. Background: Recently elderly users have been increasing in number and the ease of ingress/egress of the vehicle becomes an important issue. Method: Seven elderly subjects participated in this study(age: 71.7±3.6yr, height: 167.7±5.4㎝, weight: 68.1±11.5㎏). Each subject performed the sitting and rising task from comfortable seated position on the chair under the following conditions: (1) with a lumbar support and (2) without a lumbar support. We measured EMG activities of seven muscles(tibialis anterior, soleus, gastrocnemius, vastus lateralis, rectus femoris, biceps femoris and erector supinae) and ranges of motion in lower limb during sitting and standing from three different heights (400㎜, 500㎜ and 600㎜ from ground) of slide-up seat. Results: Muscle activities and angular movements of hip and knee joints during standing-up and sitting-down with a high seat height(600㎜) were reduced mean 30.4% in extensor muscles, 57.11% in flexor muscle, 18.74% in erector muscle and 31.0% in joints compared with a low seat height(400㎜). Conclusion: Muscle activities and joint movements in hip and knee were reduced when rising/sitting from a high seat height(600㎜) compared with a low seat height(400㎜). Application: This study can be used to design vehicle that are easy to get in and out of by older peoples with or without impairments.
ON THE STUDY OF BAYESIAN RELATIVE ERROR PREDICTION
KIM, Yongchul 용인대학교 대학원 2005 International Symposium on HUMAN & CULTURE Vol.- No.-
A condition often imposed on estimated models is that estimates and predictions have a small relative error. Usually, however, the relative error criterion is not used in the estimation process, but only to evaluate a model estimated by other model. In this paper we suggest Bayes relative error loss which gives better results in prediction.
Yongchul Kim,Younghyun Kim,Youngseon Yang,Woochul Park,KunminRhee 한국재활복지공학회 2008 한국재활복지공학회 학술대회논문집 Vol.2008 No.11
The aim of this study was to examine the influence of seat height on the movement of caregiver for transferring of a disabled person from wheelchair to car seat. Five female volunteers served as caregivers; two persons with disabilities and one health volunteer served as passive disabled person. To analyze the movement of a caregiver, we measured the activities of six muscles with surface electrodes and joint angle responses of the hip and knee with electrical goniometers. The caregivers performed transferring task at three different seat heights (400, 500 and 600mm from the floor) in order to investigate the effects of a car seat on transferring movement of a people with disability. From the experimental results, when caregivers were putting a disabled person down a seat, the hip and knee joint angles were decreased 31.9% and 24.7 % in 600mm seat height than 400mm seat height, respectively. The integrated EMG activity of erector spinae was decreased 16.3% in 600mm seat height, compared with 500mm seat height. However, the integrated EMG activity of rectus femoris for lower limb in 600mm seat height was increased 33.3% than 500mm seat height.
Driving Performance Evaluation Using Bio-signals from the Prefrontal Lobe in the Driving Simulator
Younghyun Kim,Yongchul Kim 대한인간공학회 2012 大韓人間工學會誌 Vol.31 No.2
Objective: The aim of this study was to develop the assistive device for accelerator and brake pedals using bio-signals from the prefrontal lobe in the driving simulator and evaluate its performance. Background: There is lack of assistive devices for the driving in peoples with disabilities in Korea. However, if bio-signals and/or brain waves are used at driving a car, the people with serious physical limitations can improve their community mobility. Method: 15 subjects with driver"s license participated in this study for experiment of driving performance evaluation in the simulator. Each subject drove the simulator the same course 10 times in three separated groups which use different interface controllers to accelerate and brake: (1) conventional pedal group, (2) joystick group and (3) bio-signal group(horizontal quick glance of the eyes and clench teeth). All experiments were recorded and the driving performances were evaluated by three inspectors. Results: Average score of bio-signal group for the driving in the simulator was increased 3% compared with the pedal group and was increased 9% compared with the joystick group(p<0.01). The subjects using bio-signals was decreased 44% in number of deduction compared with others because the device had the built-in modified cruise control. Conclusion: The assistive device for accelerator and brake pedals using bio-signals showed significantly better performance than using general pedal and a joystick interface(p<0.01). Application: This study can be used to design adaptive vehicle for driving in people with disabilities.