• 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.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.6
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• pp.17-21
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• 2000

Typical image features such as color, shape, and texture are used in content based image retrieved. Retrieval which uses only one image feature has little performance in case that the content of image is complex or database contains many images. So, many approaches for integrating these features have been studied. However, the problem of these approaches is how to appropriately weight the image features at query time. In this paper, we propose a new retrieval method using automatically weighted image features. We perform computer simulations in test database which consists of various kinds of images. The experimental results show that the proposed method has better performance than previous works, which use fixed weight for each feature mostly, in respect to several performance cvaluations such as precision vs recall, retrieval efficiency, and ranking measure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1749-1755
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• 2010

The performance of power window system was decided by driving characteristics of the window regulator part and reaction by the glass run. The performance of power window system usually has been predicted by experimental methods. In this paper, an analytical method using the explicit code was suggested to overcome the limit of the experimental methods. The friction coefficient of glass run was obtained by the friction test at various conditions and the Mooney-Rivlin model was used. Also, a mechanism of window regulator consisted of the fast belt system and the slip ring elements. And, we conducted the analysis considering characteristic of a motor and obtained the lifting speed of automotive glass with high reliability

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.38-51
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• 2018

This study was carried out to improve the performance characteristics of nozzleless boosters that are used in ramjet boosters. A propellant using Zr as the metal fuel was developed, which provided a higher density than the propellant using Al as the metal fuel. The developed propellant was cast using the nozzleless booster and a ground test was carried out by varying the length-to-diameter ratio (L/D ratio) of the propellant. From a comparison between the performance characteristics of propellants using Zr and Al, it was proved that the performance of the propellant using Zr is higher than that of propellant using Al, except for the specific impulse, under all tested conditions. As the length-to-diameter ratio was increased, the specific impulse of the propellant using Zr was decreased by 88% compared with that of the propellant with Al. However, because of the density difference between the propellants, the impulse density of the propellant with Zr was higher than that of the propellant with Al under all tested conditions.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.401-414
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• 2018

Planing hull type ships are often equipped with interceptor or trim tab to improve the excessive trim angle which leads to poor resistance and sea keeping performances. The purpose of this study is to design a controller to control the attitude of the ship by controllable stern interceptor and validate the effectiveness of the attitude control by the towing tank test. Embedded controller, servo motor and controllable stern interceptor system were equipped with planing hull type model ship. Prior to designing the control algorithm, a model test was performed to identify the system dynamic model of the planing hull type ship including the stern interceptor. The matrix components of model were optimized by Genetic Algorithm. Using the identified model, PID controller which is a classical controller and sliding mode controller which is a nonlinear robust controller were designed. Gain tuning of the controllers and running simulation was conducted before the towing tank test. Inserting the designed control algorithm into the embedded controller of the model ship, the effectiveness of the active control of the stern interceptor was validated by towing tank test. In still water test with small disturbance, the sliding mode controller showed better performance of canceling the disturbance and the steady-state control performance than the PID controller.

• Journal of Digital Convergence
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• v.12 no.8
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• pp.229-234
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• 2014

Vehicular electronic communication system has continued to develop in favor of high performance and user convenience with the evolution of auto industry. Yet, due to the nature of communication system, concerns over intruder attacks in transmission sections have been raised with a need for safe and secure communication being valued. Any successful intruder attacks on vehicular operation and control systems as well as on visual equipment could result in serious safety and privacy problems. Thus, research has focused on hardware-based security and secure communication protocols. This paper proposed a safe and secure vehicular communication protocol, used the formal verification tool, Casper/FDR to test the security of the proposed protocol against different types of intruder attacks, and verified that the proposed protocol was secure and ended without problems.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.4
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• pp.238-246
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• 2015

A stepping motor is widely used to operate the elevation and azimuth stage of the X-band antenna with 2-axis gimbal system for effective image data transmission from a satellite to a ground station. However, such stepping motor also generates an undesirable micro-vibration which is one of the main disturbance sources affecting image quality of the high-resolution observation satellite. In order to improve the image quality, the micro-vibration isolation of the X-band antenna system is essential. In this study, the low rotational stiffness isolator has been proposed to reduce the micro-vibration disturbance induced by elevation direction operation of the X-band antenna. In addition, its structural safety was confirmed by the structure analysis based on the derived torque budget. The effectiveness of the design was also verified through the micro-vibration measurement test.

• Journal of Power Electronics
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• v.17 no.2
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• pp.490-500
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• 2017

Fuel cell (FC) is a promising power supply in electric vehicles (EV); however, it has poor dynamic performance and short service life. To address these shortcomings, a super capacitor (SC) is adopted as an auxiliary power supply. In this study, the frequency decoupling control method is used in electric vehicle energy system. High-frequency and low-frequency demand power is provided by SC and FC, respectively, which makes full use of two power supplies. Simultaneously, the energy system still has rapidity and reliability. The distributed power system (DPS) of EV requires DC-DC converters to achieve the desired voltage. The stability of cascaded converters must be assessed. Impedance-based methods are effective in the stability analysis of DPS. In this study, closed-loop impedances of interleaved half-bridge DC-DC converter and phase-shifted full-bridge DC-DC converter based on the frequency decoupling control method are derived. The closed-loop impedance of an inverter for permanent magnet synchronous motor based on space vector modulation control method is also derived. An improved Middlebrook criterion is used to assess and adjust the stability of the energy system. A theoretical analysis and simulation test are provided to demonstrate the feasibility of the energy management system and the control method.

• The Journal of Korean Physical Therapy
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• v.24 no.5
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• pp.291-299
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• 2012

Purpose: This study examined the improved sensory, hand function, postural balance and activities of daily living (ADL) through somatosensory stimulation, such as the facilitation of functional reaching and tactile, proprioceptive stimulus of the upper limb (UL) and hand. Methods: Seventeen stroke patients having problems with motor and somatosensory deficits were selected in Bobath Memorial Hospital adult rehabilitation center. The patients were divided into two groups; the sensorimotor deficit group (SMDG) and motor deficit group (MDG). Somatosensory stimulation on the UL, physical therapy and occupational therapy were carried out three times a week over a six week these treatments were performed in both group period. To compare each group, the following assessment tools were used: such as tactile detection thresholds (TDT), two point discrimination on the affected side (TPDas), unaffected side (TPDus) stereognosis (ST) manual function test, hand function on the affected side (HFas) and unaffected side (HFus), Postural Assessment Scale for Stroke (PASS) and Korean version Modified Barthel Index (K-MBI). Results: In the SMDG, somatosensory stimulation on the UL was statistically important for TDT, TPDas, TPDus (except for the thener), ST, hand function on HFas, on HFus, PASS length of displacement with foam (LDFSEO), and K-MBI. In the MDG, somatosensory stimulation on the UL was important for TDT, TPDas, TPDus (except index finger) length of displacement with the eyes open, LDFSEO, HFas, HFus, PASS and K-MBI. In addition, there was a significant difference in the PASS between SMDG and MDG. Conclusion: Somatosensory stimulation on the UL affects the sensory, hand function, postural control and ADLs performance.

• Journal of the Korean Society of Physical Medicine
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• v.5 no.4
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• pp.655-666
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• 2010

Purpose : The examine the reliability and validity of the modified Emory Functional Ambulation Profile(mEFAP) for assessing gait function in chronic stroke patients. Methods : A total of 45 stroke patients, who had a stroke more than 6 months, participated in the study. Reliability was determined by Intra-class Correlation Coefficient($ICC_{3,1}$), including Bland and Altman method (Standard Error of Measurement: SEM, Small Real Differences: SRD). Validity was examined by correlating results to the gait ability(mEFAP, Modified Motor Assessment Scale-Gait(MMAS-G), Scandinavian Stroke Scale-Gait(SSS-G), Functional Ambulation Category(FAC), 10m Waking Test(10m WT)), and Fugl Meyer-Lower/Extremity(FM-L/E), Berg Balance Scale(BBS). Results : Inter-rater reliability for the total mEFAP was High($ICC_{2,1}$=.998), and absolute reliability were excellent (SEM: 1.75, SRD: 4.85). Subjects without assistance factor performed better on all tests than did subjects who had stroke. There were significant correlations between the mEFAP and MMAS-G, SSS-G, FAC(r=-.66~-.79), 10 m WT(r=-.86), and FM-L/E, BBS(r=-.72~-.78), indicating good validity. Increased times on the mEFAP correlated with poor performance on the gait ability, motor function of lower extremity, BBS and slow gait speeds on the 10 m WT in stroke patients. Conclusion : The mEFAP can be administered easily and comprehensively. It is a reliable gait assessment tool for patients with stroke and correlated with known of function, the mEFAP may be a clinically useful measure of ambulation.