• Transactions of the Society of Information Storage Systems
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• v.7 no.1
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• pp.19-24
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• 2011

Holographic Data Storage System, one of the next generation data storage devices, is a 2-dimensional page oriented memory system using volume holograms in writing and retrieving process. Recently photopolymer with disc type substrate was selected as a media for the Holographic Data Storage System. The disc tilt occurs when the media rotates and the external disturbance applies. The disc tilt causes the change of the angle between the reference beam and the media, the data cannot be retrieved with the right angle or other data page is retrieved. The tilt is generated in a 2-axis direction (tangential, radial). The tangential tilt direction is the same with the multiplexing plane, while the radial tilt direction is a perpendicular to the multiplexing plane. In this research we propose 2-axis tilt angle servo system. The tilt errors are measured by using external photo detector and the additional red laser. Then the tangential direction tilt is compensated by using the galvano mirror. Also the radial direction tilt is compensated by the rotating prism between the relay lens in the reference field. Finally we confirm the compensation results through the Signal to Noise Ratio(SNR) and Bit Error Rate(BER).

• Journal of Environmental Impact Assessment
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• v.17 no.5
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• pp.279-288
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• 2008

Vertical forest distribution is one of the important factors to understand various ecological mechanism such as succession, disturbance and environmental effects. LiDAR data provide information, both the horizontal and vertical distribution of forest structure. The laser scanner survey provided a point cloud, in which the x, y, and z coordinates of the points are known. The objectives of this study were 1) to analyze factors of forest structure such as individual tree isolation, tree height, canopy closure and tree density using LiDAR data and 2) to compare the forest structure between outer and interior forest. The paper conducted to extract the individual tree using watershed algorithm and to interpolate using the first return of LiDAR data for yielding digital surface model (DSM). The results of the study show characters of edge such as more isolated individual trees, higher density, lower canopy closure, and lower tree height than those of interior forest. LiDAR data is to be useful for analyzing of forest structure. Further study should be undertaken with species for more accurate results.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.781-792
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• 2016

This paper presents a new approach to enhance the data retention of logic-compatible embedded DRAMs. The memory bit-cell in this work consists of two logic transistors implemented in generic triple-well CMOS process. The key idea is to use the parasitic junction capacitance built between the common cell-body and the data storage node. For each write access, a voltage transition on the cell-body couples up the data storage levels. This technique enhances the data retention and the read performance without using additional cell devices. The technique also provides much strong immunity from the write disturbance in the nature. Measurement results from a 64-kbit eDRAM test chip implemented in a 130 nm logic CMOS technology demonstrate the effectiveness of the proposed circuit technique. The refresh period for 99.9% bit yield measures $600{\mu}s$ at 1.1 V and $85^{\circ}C$, enhancing by % over the conventional design approach.

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.161-169
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• 2006

Load representation has a significant impact on power system analysis and control results. In this paper, composite load models are developed based on on-line measurement data from a practical power system. Three types of static-dynamic load models are derived: general ZIP-induction motor model, Exponential-induction motor model and Z-induction motor model. For the dynamic induction motor model, two different third-order induction motor models are studied. The performances in modeling real and reactive power behaviors by composite load models are compared with other dynamic load models in terms of relative mismatch error. In addition, numerical consideration of ill-conditioned parameters is addressed based on trajectory sensitivity. Numerical studies indicate that the developed composite load models can accurately capture the dynamic behaviors of loads during disturbance.

• Korean Journal of Adult Nursing
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• v.20 no.3
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• pp.365-374
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• 2008

Purpose: This study was conducted to evaluate quality of sleep and to assess the factors that influence quality of sleep in surgical ICU. Methods: The subject of the study were consisted 109 adult patients who admitted to surgical ICU. The data were collected from May 20 to December 10, 2007 by structured questionnaires. The data were analyzed with descriptive analysis, paired t-test, Pearson correlation coefficient and stepwise multiple regression. Results: The score of quality of sleep was 4.57 point. The main sleep disturbance factors related to quality of sleep in surgical ICU inpatient were sleep time, machinery alarm and noise(adjusted $R^2$=33.2). Conclusion: Based on the finding of this study, it is needed to develop a nursing intervention program that including to promote quality of sleep and to decrease machinery alarm and noise in surgical ICU.

• Journal of Information Technology Applications and Management
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• v.15 no.4
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• pp.21-36
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• 2008

As the great disturbance from abusing credit cards in Korea becomes stabilized, credit card companies need to interpret credit-card delinquents classification models from the viewpoint of profit. However, hit ratio which has been used as a measure of goodness of classification models just tells us how much correctly they classified rather than how much profits can be obtained as a result of using classification models. In this research, we tried to develop a new utility-based measure from the viewpoint of profit and then used this new measure to analyze two classification models(Neural Networks and Decision Tree models). We found that the hit ratio of neural model is higher than that of decision tree model, but the utility value of decision tree model is higher than that of neural model. This experiment shows the importance of utility based measure for credit-card delinquents classification models. We expect this new measure will contribute to increasing profits of credit card companies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.763-766
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• 2006

The principal of a Maglev train is that floats on a magnetic field and is propelled by a linear induction motor. One of advantages is that it generates less noise compared to the wheel-on-rail train, because there are no wheels running along the rail. However, noises due to aero-dynamic disturbance and electrical system such as VVVF inverter and SLIM still occur. In this study, the Maglev cabin noises are measured during running and zero speed conditions. Pass-by noise measurements are performed to obtain outside noise during the operation of the train on the test tract. Data include a single microphone measurement as well as microphone array measurements. The array data are useful for sound source localization and more detailed noise reduction planning.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.2
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• pp.112-119
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• 2007

In order to predict vibration trends occurred during vehicle drive, acceleration data was processed by using data processing algorithm with moving average and Hilbert transform. Specific mode constants of acceleration were obtained under various disturbance. Vehicle velocity, road condition, property of pointing structure were considered as factors which make change of vibration trend in vehicle dynamics. Results of signal processing were compared and analysed. Advanced performance of the timing selection algorithm from this study was verified by using simple equipment comparing with the deflection measurement laser system(Muzzle Reference System).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.9
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• pp.1121-1128
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• 1999

A single blow, transient testing method for determining the heat transfer characteristics of heat exchanger surfaces are presented. The exponential inlet temperature variations were made using screen mesh with small time constant and frontal velocities of the test section. The system is used to investigate the usefulness of a model with exponential inlet temperature variations. A data reduction program is developed to calculate the temporally and spatially averaged heat transfer coefficient using the measured disturbance and response of the fluid temperature. The results are compared with the existing theoretical and experimental data for parallel plate stacks. It was recommended to take an average for the time greater than the 99% of the final temperature had reached in order to obtain fairly good results.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.173-174
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• 2006

The power infrastructure defense system monitor and control a power system with parameters of a power system such as voltage, phasor angle, frequency and power flow which are measured at the same instance. For this, synchronized phasor measurement based on the GPS(Global Positioning System) is necessary. PMU(Phasor Measurement Unit) measures synchrophasor and transmits it to the power infrastructure defense system. For this communication, IEEE H37.118 defines a communication message format and measurement concept and we extend the protocol to transmit disturbance data. The synchrophasor data can be sent at various rates and there are several options for phasor information sent in the synchrophasor message. In this paper, we develop software that simulate communication between the power infrastructure defense system and PMU to annalize the traffic.