• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.11
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• pp.860-867
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• 2003

This paper presents a systematic method measuring a velocity disturbance to design the robust seek loop system of optical disk drives. The velocity disturbance caused by the rotation of a disk has a greater influence on the performance of the seek control loop as the rotational speed increases. Thus, it needs to measure the extent of the velocity disturbance and design the seek control loop based on the measured data. The measurement method of the velocity disturbance is a real-time . method using a measurable velocity and a velocity controller output and is a robust method considering actuator uncertainties. The loop gain adjustment algorithm is introduced to compensate for the actuator uncertainties. The proposed method is implemented by an experimental digital system and is evaluated through an experiment.

• Transactions of the Society of Information Storage Systems
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• v.3 no.1
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• pp.13-16
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• 2007

The purpose of this paper is real time tilt servo control of the holographic data storage system. Holographic data storage device is a next generation data storage device with high storage density, high transfer rate and short access time. This device is very sensitive to a disturbance due to the enormous storage density. As to the recording material changed disc type, the media continuously vibrates as the disc rotates. When disc rotates, deviation, eccentricity and unbalance disturbance are occurred. This disturbances cause disc tilt, finally reference beam does not illuminates to correct incidence angle. Therefore real time tilt servo control is essential. In this paper, the algorithm is proposed to make real time tilt detection in angle multiplexing of the holographic data storage system with an additional servo beam and the experiments are performed.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.5
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• pp.402-410
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• 2004

To obtain a good tracking performance in an optical disk drive servo system, it is essential to attenuate periodic disturbances caused by eccentric rotation of the disk. As an effective control scheme for enhancing disturbance attenuation performance, disturbance observers (DOBs) have been successfully applied to the track-following servo system of optical disk drives. In disk drive systems, the improvement of data transfer rate has been achieved mainly by the increase of disk rotational speed, which leads to the increase of the disturbance frequency. Conventional DOBs are no longer effective in disk drive systems with a high-speed rotation mechanism because the performance of conventional DOBs is severely degraded as the disk rotational frequency increases. This paper proposes a new DOB structure for effective rejection of the disturbance in optical disk drives with a very high rotation speed. Asymptotic disturbance rejection is achieved by adopting a band-pass filter in the DOB structure, which is tuned based on the information on the disturbance frequency. In addition, performance sensitivity of the proposed DOB to changes in disk rotational frequency is analyzed. The effectiveness of the proposed DOB is verified through simulations and experiments using a DVD-ROM drive.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.9
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• pp.413-422
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• 2002

In a power plant, disturbance detection and diagnosis are massive and complex problems. Once a disturbance occurs, it can be either persistent, self cleared, cleared by the automatic controllers or propagated into another disturbance until it subsides in a new equilibrium or a stable state. In addition to the Physical complexity of the power plant structure itself, these dynamic behaviors of the disturbances further complicate the fault monitoring and diagnosis tasks. A data structure called a disturbance interrelation analysis graph(DIAG) is proposed in this paper, trying to capture, organize and better utilize the vast and interrelated knowledge required for power plant disturbance detection and diagnosis. The DIAG is a multi-layer directed AND/OR graph composed of 4 layers. Each layer includes vertices that represent components, disturbances, conditions and sensors respectively With the implementation of the DIAG, disturbances and their relationships can be conveniently represented and traced with modularized operations. All the cascaded disturbances following an initial triggering disturbance can be diagnosed in the context of that initial disturbance instead of diagnosing each of them as an individual disturbance. DIAG is applied to a typical cooling water system of a thermal power plant and its effectiveness is also demonstrated.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.18 no.2
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• pp.186-194
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• 2011

Purpose: The purpose of this study was to investigate factors of sleep disturbance and sleep patterns of elderly hospitalized women patients between young-old (65-74 years), old (76-84 years) and old-old (85 years and above). Methods: The questionnaire included the environmental disturbance factors (Paik, 2000), degree of pain (Wang & Kim,1995), disease symptoms (Paik, 2000), depression (Kee, 1996) and sleep patterns (Oh, Song, & Kim, 1998). Data were analyzed using frequencies, means, ${\chi}^2$-test, t-test, ANOVA, Scheffe, Pearson correlation coefficients and multiple regression (SPSS 14.0). Results: The middle, and oldest group's environmental disturbance factors of degree of pain, disease symptoms, depression and sleep patterns were higher than those of the younger group. The younger, middle, and oldest group's sleep pattern had a significant negative correlation with environmental disturbance factors, degree of pain, disease symptoms and depression. The model including variables related to environmental, physical and psychological disturbance factors, explained the following variances in sleep pattern: 26.8% for the youngest group, 27.6% for the middle group and 40.7% for the oldest group. Conclusion: The result of this study offer basic data for the development of nursing intervention programs to improve sleep patterns for hospitalized women patients according to age differences.

• Asian Oncology Nursing
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• v.12 no.4
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• pp.274-279
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• 2012

Purpose: This study was conducted to test whether sleep disturbance mediates the effect of pain on fatigue, whether fatigue mediates the effect of pain on depression, and whether fatigue mediates the effect of sleep disturbance on depression. Methods: This study was conducted from September 12th to December 20th, 2011. One hundred eighty-eight breast cancer patients were recruited from D city and S city in Korea. The instruments used in this study were the pain, sleep disturbance, fatigue, and depression scales. Data were analyzed using descriptive statistics, Pearson correlation coefficients, and mediation pathway with the SPSS 12.0 and AMOS 20.0 programs. Results: There was correlation among pain, fatigue, sleep disturbance, and depression. Mediation analyses indicated that pain influences fatigue. sleep disturbance, and depression directly as well as indirectly. Sleep disturbance influences fatigue and depression directly, also fatigue influences depression directly. But sleep disturbance had no direct effect on depression. Conclusion: Significant correlations among the four symptoms supported the existence of the symptom cluster. Effects of pain on fatigue was partially mediated by sleep disturbance, also effects of pain on depression was partially mediated by fatigue. However, the effects of sleep disturbance on depression was fully mediated by fatigue.

• The Korean Journal of Rehabilitation Nursing
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• v.13 no.2
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• pp.105-113
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• 2010

Purpose: The purpose of this study was to examine symptoms, mood and sleep disturbance in patients with hemodialysis. Method: A sample of 96 hemodialysis patients participated. Data were collected using symptom scale of hemodialysis patients, profile of mood state and the sleep scale. Statistical analytic methods included t-tes, ANOVA and Pearson correlation analyses. Results: Patients with spouse/partners experienced significantly less symptoms than those with no spouse (F=6.29, p=.003). Mood disturbance was not significantly correlated with age; but older patients experienced higher sleep disturbance (F=4.88, p=.010). Symptoms, mood and sleep disturbance are significantly related with each other. Conclusion: It is important to assess symptoms, mood and sleep disturbance in older hemodialysis patients with no spouse. It is needed to repeat extensive study and comparative study with other population in order to define clearly.

• International Journal of Advanced Culture Technology
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• v.10 no.4
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• pp.470-477
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• 2022

EOTS for drones is showing another aspect of market expansion in detection and recognition areas previously occupied by artificial satellites. The two-axis EOTS for drones controls the vibration or disturbance caused by the drone during the mission so that EOTS can accurately recognize the goal. Vibration generated by drones is transmitted to EOTS. Therefore, it is essential to develop a stabilization controller that attenuates vibrations transmitted from drones so that EOTS can maintain the viewing angle. Therefore, it is necessary to standardize drone disturbance and secure the performance of EOTS disturbance attenuation controller optimized for disturbance level through this. In this paper, a method of standardizing drone disturbance applied to EOTS is studied, through which EOTS controller simulation is performed and stabilization controller shape is selected and designed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.1
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• pp.160-167
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• 2009

In this paper, we apply the robust disturbance observer (DOB) to a SPM-based data storage (SDS) system. In the SDS system, coupling dynamics and parameter uncertainties are obstacles to the precision tracking control. Although the DOB is known to be an effective method to reject disturbances, there has been no systematic design approach to how to design DOB parameters. In this paper, the robust DOB is formulated based on the robust stabilization of normalized coprime factor plant description and the $H{\infty}$ loop shaping method. From the simulation and experimental results. the improved robustness and performance are obtained by the proposed robust DOB.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.340-340
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• 2000

This paper aims at deriving an equivalent finite dimensional discrete-time system for H$_{\infty}$ type problem for sampled-data control systems. A widely used ph is based on the lifting technique, but it needs somewhat complicate computation. Instead this paper derives an equivalent finite-dimensional discrete-time system directly from a description of the sampled-data system which is achieved via a closed-loop expression of the worst-case intersample disturbance.