• Journal of Positioning, Navigation, and Timing
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• v.3 no.3
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• pp.117-122
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• 2014

In CDGPS, ambiguity resolution is determined by the performance of a floating solution, and thus, the performance needs to be improved. In the case of precise positioning at a stationary position, the batch method using multiple measurements is used for the accuracy improvement of a position. The position accuracy performance of a floating solution is outstanding, but it has a problem of high computation cost because all measurements are used. In this study, to improve the floating solution performance of the initial static user in CDGPS, a floating solution method using a recursive filter was implemented. A recursive filter estimates the position solution of the current epoch using the position solution of up to the previous epoch and the pseudorange measurement of the current epoch. The computation cost of the floating solution method using a recursive filter was found to be similar to that of the epoch-by-epoch method. Also, based on actual GPS signals, the floating solution performance was found to be similar to that of the batch method. The floating solution using a recursive filter could significantly improve the performance of the prompt initial position and ambiguity resolution of the initial static user.

• The Journal of Korea Robotics Society
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• v.1 no.1
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• pp.81-88
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• 2006

Control of a robot manipulator in contact with the environment is usually conducted by the direct feedback control using a force-torque sensor or the indirect impedance control. In these methods, however, the control algorithms become complicated and the performance of position and force control cannot be improved because of the mechanical properties of the passive components. To cope with such problems, redundant actuation has been used to enhance the performance of position control and force control. In this research, a Double Actuator Unit (DAU) is proposed, with which the force control algorithm can be simplified and can make the robot ensure the safety during the external collision. The DAU is composed of two actuators; one controls the position and the other modulates the joint stiffness. Using this unit, it is possible to independently control the position and stiffness. The DAU based on the planetary gears is investigated in this paper. Performance using the DAU is also verified by various experiments. It is shown that the manipulator using this mechanism provides better safety during the impact with the environment by reducing the joint stiffness appropriately on detecting the collision of a manipulator.

• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.226-234
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• 2006

Aids to Navigation is one of the most important facility for safety at sea. However, in terms of position there always exists discrepancy in inventory by media and/or organizational body who maintains the facility which may result in incredibility for navigator's position fixing or hazard avoidance. This paper suggests two major factors as the causes of the position error when they design, install and survey the aids to navigation. One is the function of direction of tide and water depth which makes swinging circle. The other is a variable value by time resulting from multiple coordination of satellites in contact. This paper aims to minimize inaccuracy by verifying its reason through numerical analysis over inherent position error.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3431-3437
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• 2021

In this study, one-dimensional gamma ray source positions are estimated using a plastic scintillating optical fiber, two photon counters and via data processing with a machine learning algorithm. A nonlinear regression algorithm is used to construct a machine learning model for the position estimation of radioactive sources. The position estimation results of radioactive sources using machine learning are compared with the theoretical position estimation results based on the same measured data. Various tests at the source positions are conducted to determine the improvement in the accuracy of source position estimation. In addition, an evaluation is performed to compare the change in accuracy when varying the number of training datasets. The proposed one-dimensional gamma ray source position estimation system with plastic scintillating fiber using machine learning algorithm can be used as radioactive leakage scanners at disposal sites.

• Journal of Korea Water Resources Association
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• v.44 no.2
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• pp.85-96
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• 2011

Probability plotting position is generally used for the graphical analysis of the annual maximum quantile and the estimation of exceedance probability to display the fitness between sample and an appropriate probability distribution. In addition, it is used to apply a specific goodness of fit test. Plotting position formula to define the probability plotting position has been studied in many researches. Especially, the GEV distribution which is an important probability distribution to analyze the frequency of hydrologic data was popular. In this study, the theoretical reduced variates are derived using the mean value of order statistics to derived an appropriate plotting position formula for the GEV distribution. In addition, various forms of plotting position formula considering various sample sizes and coefficients of skewness related with shape parameters are applied. The parameters of plotting position formulas are estimated using the genetic algorithm. The accuracy of derived plotting position formula is estimated by the errors between the theoretical reduced variates and those by various plotting position formulas including the derived ones in this study. As a result, the errors by derived plotting position formula is the smallest at the range of shape parameter with -0.25~0.10.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.2
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• pp.242-254
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• 2016

This paper is the forth investigation on the evaluation methods of flow characteristics in a steady flow bench. In the previous works, it was concluded that the assumption of the solid rotation might cause serious problems and both of the eccentricity and the velocity profile distort the flow characteristics when using the ISM at 1.75B plane. Also particle image velocimetry (PIV) measurement at this position showed that the real velocity profile was far from the assumption of ISM evaluation. In this paper, the planar velocity profiles were measure from 1.75B to 6.00B position by PIV and the characteristics were examined according to the valve angles and lifts for further investigations about the effect of the position on the velocity profile. The results show that $26^{\circ}$ valve angle is always an unique exceptional case in all aspects. If the valve angle is $21^{\circ}$ and below, the planar velocity profiles according to the lift and the position are similar to each other, however, the tangential velocity curves along with the radial direction have common tendencies up to $16^{\circ}$ angle. Also the well arranged swirl behaviors are generally observed at the position above 3.00B and the velocity contour lines come closer to the concentric circle as the valve lift increases. In addition, the gradient of tangential velocity along with the radial direction from the swirl center becomes stable and constant as the position goes downstream. Concurrently the velocity gradient is larger to the eccentric direction of the center. In the meantime the tangential velocity curves along with the radial direction are irregular and various at 1.75B, however, they become regular and reach higher level as the evaluation position goes downstream. At this time the curves of 4.50B are the best fitted to the ideal one. On the other hand in an exceptional case, $26^{\circ}$, the velocity contours are very complicated over 6mm valve lift regardless the position and the gradient increases to the opposite direction of the eccentric center. Also, 6.00B is a best fitting position in the geometrical cylinder center base. With respect to the swirl center, the distribution range of centers for 1.75B is different to that for the other positions and the eccentricities of this plane are larger regardless the valve angle. After 1.75B, there is no certain tendency in the center position change according to the valve angle and lift. Additionally, the eccentricities are not sufficiently small to neglecting the effect on ISM measurement.

• Physical Therapy Korea
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• v.10 no.3
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• pp.63-70
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• 2003

The purpose of this study was to compare the difference of joint position sense between measurements. Fourteen healthy male subjects were recruited for this study. The elbow joint position senses were measured using angle reproduction test. The elbow joint position sense was assessed with three experimental conditions: ipsilateral reproduction test in open-chain condition, contralateral reproduction test in open-chain condition, ipsilateral reproduction test with weight in open-chain condition and ipsilateral reproduction test in closed-chain condition. The angular difference between stimulus position and the reproduced position (angular error) was calculated in all testing conditions to examine the accuracy of the joint position sense. One way ANOVA was used to compare the error angles in all experimental conditions. The error angles between measurements were significantly different in elbow joint. The error angles was smallest in ipsilateral reproduction test with weight in open-chain condition and was greatest in the contralateral reproduction test in open-chain condition. Findings of this study indicate that testing methods, types of task, existence of resistance should be considered in clinical assessment for the joint position sense.

• Physical Therapy Rehabilitation Science
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• v.3 no.2
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• pp.101-106
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• 2014

Objective: To investigate the appropriate position for abdominal drawing-in maneuver (ADIM) exercise by rehabilitative ultrasound image. Design: Cross-sectional study. Methods: Twenty-eight young adults with no history of low back pain participated in the study. Three positions compared were crook lying position with hip $60^{\circ}$ flexion, standing position with the feet hip width apart and knees straight, and saddle standing positionunsupported with the knees $20^{\circ}$ flexed. Once in the appropriate position, the subjects were verbally cued to draw in their abdominal wall, with the intention of pulling their navel inward toward their lower back. The thickness of each transversus abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles were measured via ultrasound and recorded at the end of inspiration. Results: When compared to the TrA thickness of rest, the TrA thickness was significantly increased in all three positions (crook lying, standing, and saddle standing) during the ADIM (p<0.05). IO thickness was significantly greater in standing and saddle standing than in crook lying (p<0.05). EO thickness was constant in all the three positions. Conclusions: The present study suggests that standing and saddle standing positions could be recommended for the ADIM to maximize recruitment of the TrA and IO activation. Specifically, the saddle standing position with knees flexed to $20^{\circ}$ was observed to increase the TrA activation more than the standing position. These findings should be considered when core stability exercises such as the ADIM are conducted.

• Physical Therapy Korea
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• v.29 no.1
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• pp.64-69
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• 2022

Background: Gluteus medius muscle is important for the stability of hip joint. The sufficient core stability can be contributed to the performance of gluteus medius muscle in standing position. In addition, the external support may affect core stability in standing position. Objects: The purpose of this study was to investigated the effectiveness of the external support on the strength and muscle activity of hip abductor muscle during hip abduction in standing position in subjects without core stability. Methods: Fifteen subjects participated in this study. The subjects were evaluated by using the double-leg lowering with bent knees to measure the core stability. The strength and muscle activity of hip abductors was measured in standing position with the condition with and without external support using the tensiometer sensor and the surface electromyography. The paired t-test was used to investigate the difference between hip abductor strength and activity according to external support. The level of statistical significance was set at α = 0.05. Results: The hip abductor strength and muscle activity of gluteus medius muscle with external support were significantly greater than those without external support during hip abduction in standing position (p < 0.05). Conclusion: During hip abduction in standing position, the external support may be contributed to the improvement of the hip abductor strength and muscle activity of gluteus medius especially in the subjects without core stability.

• Journal of Biosystems Engineering
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• v.35 no.4
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• pp.224-230
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• 2010

The purpose of this study was to develop position control system of an electric actuator for automatic shuttle shifting of a tractor. The electric actuator was installed at the link of the forward-reverse gearshift of the tractor transmission, and controlled in the ranges of forward, neutral, and reverse positions. The position control system of the electric actuator was developed based on PID (Proportional Integral Derivative) controller and transfer function of the electric actuator. The coefficients of the PID controller were determined by Ziegler-Nichols (Z-N) method and optimized using simulation program. The prototype AMT (Automated Manual Transmission) test unit of the tractor was installed and used to evaluate the performance of the position control. The evaluation system for the control performance consisted of forward-reverse actuator, motor driver, and controller. The tests were conducted as the controlled positions of the actuator were changed from neutral position to forward, neutral, and reverse positions in sequence. The sequential tests were repeated 20 times. The operations of changing the gearshift were considered as the step response of the control system. Maximum overshoot, settling time, and steady-state error were analyzed. The results showed that performance of the position control system was reasonable and qualified. The maximum overshoots, the steady-state errors, and the settling times of the position control system were 10~20%, 1~5%, and 0.92~1.49 sec, respectively. The modifications of the electric actuator will be required to enhance the performance of position control during field operation.