• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.12
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• pp.2351-2357
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• 2008

Noninvasive radial artery pulse wave has been widely used not only for the pulse wave analysis(PWA) itself but also for assessment of arterial stiffness with estimated aortic pulse wave from peripheral pulse wave. However, it has been found that the deformation of pulse shape can be caused readily by changing measuring position, indentation pressure, and so on. So, in this study, we have developed a system which can measure radial pulse wave and skin displacement simultaneously while the indentation body goes down to occlude subject's radial artery. This system can be divided into a measuring apparatus part, an indentation control hardware part, a data acquisition part and a control and computation part. And, the measuring apparatus consists of an arm-rest, a step motor, an indentation body, a laser displacement sensor(LK-G30, Keyence Co.) and pulse wave sensor. Under load-free condition and radial artery loaded condition, the evaluation of developed system has been performed. From these results, we can conclude: 1) The developed system can control the indentation body quantitatively and the adopted laser displacement sensor shows linear output characteristic even with skin as a reflector. 2) This system can measure the pulse wave and the displacement of indentation body, that is, skin displacement simultaneously at each specific level of indentation body. 3) This system can provide the number of motor steps used to get down the indentation body, the measured skin displacement, the calculated indentation pressure, the calculated pulse pressure and the pulse waveform as well as the information generated by combining these with each others. 4) This system can reveal the relationship between the morphological changes of pulse wave and the estimated displacement of radial artery wall by indentation. Consequently, the developed system can furnish more abundant information on radial artery than previous diagnosis systems based on tonometric measurement. In further study, we expect to setup the standard measuring process and to concrete the algorithm for the estimation of radial artery's diameter and of displacement of radial artery's wall. Furthermore, with well designed clinical studies, we hope to turn out the usefulness of developed system in the field of cardiovascular system evaluation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.109-117
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• 2009

In this paper, an analytical model using equivalent magnetic circuits for the PMA-SynRG is presented. The lumped parameter model (LPM) is developed from machine geometry, stator winding and machine operating specifications. By the LPM, magnetic saturation of rotor bridges is incorporated into model and it provides effective means of predicting machine performance for a given machine geometry. The LPM is not as accurate as finite element analysis but the equivalent magnetic circuits provide fast means of analyzing electromagnetic characteristics of PMa-SynRG. It is the main advantage to find the initial design and optimum design. The initial design of PMa_RSG is performed by LPM model and FEM analysis, and the final PMA-RSG design is optimized and identified by FEM analysis considering actual machine design. The linear LPM and the nonlinear LPM are programmed using MATLAB and all of machine parameters are calculated very quickly. To verify justification of the proposed design of PMa-RSM, back-EMF is measured.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.771-782
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• 2017

This paper describes the development of a wearable robot to assist ankle power for the elderly. Previously developed wearable robots have generally used motors and gears to assist muscle power during walking. However, the combination of motor and reduction gear is heavy and has limitations on the simultaneous control of stiffness and torque due to the friction of the gear reducer unlike human muscles. Therefore, in this study, Mckibben pneumatic muscle, which is lighter, safer, and more powerful than an electric motor with gear, was used to assist ankle joint. Antagonistic actuation using a pair of pneumatic muscles assisted the power of the soleus muscles and tibialis anterior muscles used for the pitching motion of the ankle joint, and the model parameters of the antagonistic actuator were experimentally derived using a muscle test platform. To recognize the wearer's walking intention, foot load and ankle torque were calculated by measuring the pressure and the center of pressure of the foot using force and linear displacement sensors, and the stiffness and the torque of the pneumatic muscle joint were then controlled by the calculated ankle torque and foot load. Finally, the performance of the developed ankle power assistive robot was experimentally verified by measuring EMG signals during walking experiments on a treadmill.

• The Journal of Korean Society for School & Community Health Education
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• v.4
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• pp.79-95
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• 2003

This dissertation aims to analyze various safety accidents taking place during physical education class according to physical education teacher's value orientation, to identify teacher's value orientation that can minimize safety accidents, and to provide basic materials for safe and smooth class management. For this purpose, data have been collected from 261 physical education teachers at some middle and high schools in G City in Kyung-Ki Province and Busan Metropolitan City. The materials were treated as follows: The variables on demographic characteristics of physical education teachers are determined by t-test ; The analysis of one-way ANOVA and relationship between value orientation and safety accident prevention activities was conducted through Pearson's linear correlation analysis and multiple regression; The analysis of the relationship between value orientation and actual conditions of safety accidents was conducted through logistic regression. First, there is almost no awareness difference of physical education teachers' value orientation according to demographical variables. The value orientation physical education teachers consider to be the most important is, however, mainly 'mastery of disciplinary lesson.' There is a statistically significant difference in safety accident prevention activities according to demographical variables. Teachers' focuses in class contents showed a significant difference according to teaching experience and working area, while the dependency on facility has a significant difference according to teaching experience and school type. Second, there is no correlation between physical education teacher's value orientation and safety accident prevention activities because there is virtually no statistically significant difference between them. It means that safety accident prevention activities are not related with on which teachers place emphasis among mastery of disciplinary lesson, social reconstruction, self-realization, ecological integration and value orientation on learning process. Third, the analysis of safety accident prevention activities according to physical education teachers' value orientation revealed that the lower value orientation in social reconstruction is, the more safety accidents teachers experience. It is also found that crashes among students, ball games and leg injuries are inter-related with social reconstruction in value orientation, over-motivation and unskilled motor function ; athletic sports with value orientation on learning process and safety prevention training ; unskilled motor functions with value orientation in ecological integration and disobedience to teacher's directions ; winter accidents with mastery of disciplinary lesson in value orientation. In conclusion, the research indicates that physical education teacher's value orientation according to demographical variables didn't show any significant difference, while one according to safety accident prevention activities showed significant difference. Besides, physical education teachers' value orientation is not related to safety accident prevention activities, but the relationship between value orientation and actual conditions of safety accidents showed correlations according to each variable. Especially, teachers with lower value orientation in social reconstruction experienced more safety accidents. Therefore, physical education teachers can manage physical education class more safely with more emphasis on value orientation in social reconstruction.

• Journal of Aerospace System Engineering
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• v.16 no.1
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• pp.49-55
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• 2022

The role of drones has been expanded to various fields such as agriculture, construction, and logistics. In particular, agriculture drones are emerging as an effective alternative to solve the problem of labor shortage and reduce the input cost. In this study therefore, we proposed the fruit recognition algorithm and harvesting mechanism for fruit harvesting drone system that can safely harvest fruits at high positions. In the fruit recognition algorithm, we employ "You-Only-Look-Once" which is a deep learning-based object detection algorithm and verify its feasibility by establishing a virtual simulation environment. In addition, we propose the fruit harvesting mechanism which can be operated by a single driving motor. The rotational motion of the motor is converted into a linear motion by the scotch yoke, and the opened gripper moves forward, grips a fruit and rotates it for harvesting. The feasibility of the proposed mechanism is verified by performing Multi-body dynamics analysis.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.4
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• pp.464-476
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• 2019

Objectives: This study aimed to assess the exposure levels of tollbooth workers to diesel particulate matter using black carbon (BC) and to find the correlations among variables associated with BC using the motor vehicle management act regulated by the Ministry of Land, Infrastructure and Transport. Methods: This study was performed over 14 days at a university in Seoul. BC levels were monitored using an aethalometer and were conducted around the breathing zones of the workers. There were three sampling locations: inside the tollbooth (front gate and rear gate) and an office as a control group. T-test, correlation, and multiple linear regression analysis were performed using SPSS. Results: The geometric mean (GM) of BC_30min concentrations in the exposure group was 2.44 ㎍/㎥, approximately 1.4 times higher than the control group (1.75 ㎍/㎥). The GM of BC_30min concentrations was 2.75 ㎍/㎥ during the heavy traffic time (9-10 am) and 2.30 ㎍/㎥ during non-heavy traffic times (p<0.001). The multiple linear regression analysis shows that the number of all types of vehicles and PM_2.5 concentrations in the atmosphere were factors increasing the GM of BC(ln(BC_30min)) concentrations (adjusted R²=0.42, p<0.001). The workers were constantly exposed to low concentrations (GM of BC_30min=2.44 ㎍/㎥), but they were exposed to peak concentrations instantly (BC_10sec=3545.04 ㎍/㎥). When the GM of BC_30min concentrations was momentarily represented as high, it was identified that a vehicle mainly using diesel fuel or an aging vehicle had passed. Conclusions: A ventilation system should be installed in the closed tollbooth or aging vehicles should be controlled so as not to pass tollbooths.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.642-648
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• 2019

This paper presents a fast back-type transfer device for snack food processing that uses the inertia of transferred material. A conventional conveying system is a drive system that uses a belt conveyor and mechanical crank, which generate noise and vibration and cause environmental pollution. Vibration and noise are reduced in the proposed fast back feeding device by using a counterweight. The crank drive unit was replaced with a linear servomotor, and an equilibrium device was designed to balance the force due to acceleration. This makes it is possible to adjust the forward and backward speed and acceleration through PLC control. A vibration damper device offsets the vibration force of the periodic shock form. The main cause of the vibration was identified through vibration analysis, and reduction measures were established. We verified the effectiveness of the vibration by making a prototype and performing about 10 vibration tests. Because no mechanical transducer is needed, energy loss, noise, and vibration do not occur, and the operating speed is not limited.

• Physical Therapy Korea
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• v.8 no.1
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• pp.20-34
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• 2001

This paper presents the relevance between GMFM and the spatiotemporal parameters of gait in children with cerebral palsy. Twenty-one children ($73.11{\pm}30.06$ months) with cerebral palsy participated in this study. GMFM was performed and spatiotemporal parameters of gait were measured by foot print gait analysis. A correlation analysis was used to investigate the correlation between GMFM scores and spatiotemporal parameters of gait. A linear regression analysis was employed to find how much each gait spatiotemporal parameters could be predicted from GMFM scores. The total GMFM scores was significantly correlated with walking speed, cadence, and stride length. Dimensions D (standing) and E (walking, running, and jumping) were more significantly correlated with gait spatiotemporal parameters than dimensions A (lying and rolling), B (sitting), and C (crawling and kneeling). The GMFM scores were useful for predicting spatiotemporal parameters. However, it is difficult to predict the status of gait development using GMFM scores because GMFM scores and gait spatiotemporal parameters are only measured as quantities not qualities. In the field, it is easily found that many children with cerebral palsy are unable to walk in any way. Consequently, gait analysis cannot be performed in many cases. Therefore, it is more reasonable to investigate the influence of GMFM on spatiotemporal parameters, rather than vice versa.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.1
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• pp.40-47
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• 2013

The similarity in internal flow of solid and hybrid rocket suggests that hybrid rocket combustion can be susceptible to instability due to vortex sheddings and their interaction. This study focuses on the evolution of interaction of vortex generated in pre-chamber with other types of vortex in the combustor and the change of combustion characteristics. Baseline and other results tested with disks show that there are five different frequency bands appeared in spectral domain. These include a frequency with thermal lag of solid fuel, vortex shedding due to obstacles such as forward, backward facing step and wall vortices near surface. The comparison of frequency behavior in the cases with disk 1 and 3 reveals that vortex shedding generated in pre-chamber can interact with other types of vortex shedding at a certain condition. The frequency of Helmholtz mode is one of candidates resulting to a resonance when it was excited by other types of oscillation even if this mode was not discernable in baseline test. This selective mechanism of resonance may explain the reason why non-linear combustion instability occurs in hybrid rocket combustion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.1
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• pp.31-39
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• 2013

A Quad Tilt Wing UAV is a new concept hybrid UAV having the advantages of both fixed-wing and rotary-wing aircraft. This paper presents longitudinal flight dynamic characteristics of a Quad Tilt Wing UAV. The designed Quad Tilt Wing UAV is a configuration of a tandem wing type aircraft with an actuating motor and propeller mounted at each wing. Momentum theory is used to calculate the thrust, and nonlinear modeling is performed considering lift and drag generated by slip stream effect of propellers. Also, Force and moment variation at each tilting angle is considered. Static trim on longitudinal axis is analyzed via numerical simulation. Componentwise force contribution was analyzed at each trim mode. Dynamic characteristics were evaluated through eigenvalue analysis for a linear model at each flight mode. It is verified that longitudinal dynamic characteristics are changing from unstable to stable state by continuous transition of dominant poles.