• Journal of Information Management
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• v.39 no.2
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• pp.211-234
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• 2008

Recently, the frequency and scale of natural disasters such as typhoons, flood, earthquakes, and tidal waves from earthquakes has been increasing. Several nations have recognized that earth observation is essential for protecting the Earth's environment. However, as the data format from earth observation varies depending on areas, institutes, and countries, sharing and exchange between data is difficult. Thus, we have a metadata standardization scheme suitable for the domestic situation to allow exchange of data between societal benefit areas with reference to principles of data sharing and exchange that are discussed on GEO (Group on Earth Observation). We have also designed metadata schemes required to identify the metadata situation of earth observation data being used for 9 societal benefit areas of GEOSS(Global Earth Observation System of Systems).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.586-594
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• 2009

This paper is the study on random, sinusoidal and shock vibration responses for the STSAT-3(science and technology satellite-3) proto-model which is the first small size all-composite satellite in Korea. The structure system of the STSAT-3 forms box type structure by joining several hybrid sandwich panels comprised of honeycomb core and carbon fiber reinforced laminated composite skins on both side. Mode shape, stress, displacement and acceleration responses are obtained on both the frequency domain and time domain by means of a commercial FEA software MSC/NASTRAN. From these analysis results, failure, safety factor and design validity are assessed. These results can be successfully applicable as reference data when a new satellite is developed as well as giving out an excellent criteria in satellite vibration treatment design.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.531-537
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• 2018

A novel PLL with a delta-sigma modulator and a spur reduction circuit is proposed. delta-sigma modulator makes the LF remove noise easily by moving the spur noise to a higher frequency band. Therefore, the magnitude of spur can be reduced the reasonable bandwidth. The spur reduction circuit reduces the spur size by reducing the LF voltage change generated during the period of reference signal. The spur reduction circuit is designed as simple as possible not to increase the size of PLL. The proposed PLL with the previous two techniques is designed with a supply voltage of 1.8V in a 0.18um CMOS process. Simulation results show an almost 20dB reduction in the magnitude of spur. The spur reduced PLL can be used in narrow bandwidth communication system.

• Journal of the Korean Institute of Landscape Architecture
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• v.26 no.3
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• pp.78-78
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• 1998

The purpose of this research is to develop a CAD-based program for data analysis of digital elevation model(DEM) on the aspect of landscape assessment. When handling DEM data as a visual simulation of topographic landscape, it is basic interest to analyze visible area and visualize visual sensitivity distributions. In reference with landscape assessment, more intuitive and interactive visualizing tools are needed, specially in area of visual approach. For adaptability to landscape assessment, algorithmic approaches to visibility analysis and concepts for visual sensitivity calculation in this study were based on processing techniques of entity data control functions used in AutoCAD drawing database. Also, for the purpose of quantitative analysis, grid-type 3DFACE entities were adopted as mesh unit of DEM structure. Developed programs are composed of main part named VSI written in AutoLISP and two of interface modules written in dialog control language(DCL0 for user-oriented interactive usage. Definitions of camera points(view points) and target points(or observed area) are available alternatively in combined methods of representing scenic landscape, scenery, and sequential landscape. In the case of scene landscape(single camera to fixed target point), only visibility analysis in available. And total visibility, frequency of cumulative visibility, and visual sensitivity analysis are available in other cases. Visual sensitivity was thought as view angle(3 dimensional observed visual area) and the strengths were classified in user defined level referring to statistical characteristics of distribution. Visibility analysis routine of the VSI was proved to be more effective in the accuracy and time comparing with similar modules of existing AutoCAD third utility.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1483-1489
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• 2015

The purpose of this study is to investigate the changes in citizens' perceiving urban landscape. To this end, the citizens' perceptions of urban landscape of Gimhae were surveyed two times in 2003 and 2011. To examine the statistical significance, the frequency analysis, the chi-square test were applied. There were small changes of opinion between two periods caused by the change of city form, an increase in interest in the living environment, environmental protection and so on. The interest of the citizens of the landscape were high. Citizens showed a negative feedback with respect to economic sacrifice. So, regulation causing citizens' economic loss should be avoided and It is effective to establish policies to support and induction. The results of this study are intended to be used as a reference to the planning urban landscape.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4296-4302
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• 2013

The objective of this study is to examine the motivation for renaming and the self-perception scale attained after renaming. The survey was conducted targeting 161 individuals across the country from April 1 to May 31, 2013. The analyzing methods include frequency analysis, correlation analysis, t-test, one-way ANOVA analysis and stepwise regression analysis, etc. All of the empirical analysis was verified at the 5% level of significance. According to the result of analysis, the renamed individuals scored higher on the success scale, the emotional scale and the personality scale after renaming. The study found that the individuals, who adopted a new name as per their own desire, scored significantly higher on the self perception scale. The study will serve as a reference material for persons who desire a new name, based on its result that the greatest motivation for renaming is the "desire to have a good name" and that the biggest changes accompanying the new name are the self confidence and satisfaction which have helped the renamed individuals score higher on the self-perception scale after renaming.

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.4
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• pp.214-219
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• 2009

This paper proposes a watermarking algorithm considering the frequency characteristics of Haegeum sounds for copyright protection of digital Haegeum sound contents. The harmonics of Haegeum sounds commonly have large magnitude values in 1500Hz~2000Hz and 2800Hz~3500Hz so that those bands are selected to embed a watermark. The proposed method computes the FFT (fast Fourier transform) of the original sound signal and embeds the watermark bits generated by PN (pseudo noise) sequence into the harmonics in the selected bands. Furthermore, the proposed method is robust to lowpass filter, bandpass filter, cropping, noise addition, MP3 compression attacks and the maximum BER (bit error rate) is 1.41% after lowpass filter attack. To measure the quality of the watermarked sound, subjective listening test, MUSHRA (multiple stimuli with hidden reference and anchor), was conducted. The mean value of MUSHRA listening test is bigger than 98 and 96.67 for every Haegeum sounds and Korean classical music with Haeguem, respectively.

• Journal of KIISE:Databases
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• v.30 no.4
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• pp.408-419
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• 2003

Data warehouses are usually dedicated to the processing of quires issued by decision support system(DSS). The response time of DSS queries is typically several orders of magnitude higher than the one of OLTP queries. Since DSS queries are often submitted interactively, techniques for reducing their response time are important. The caching of query results is one such technique particularly well suited to the DSS environment. In this paper, we present a cache manager for such an environment. Specifically, we define a canonical form of query. The cache manager looks up a query based on the exact query match or using a suggested query split process if the query is found is non-canonical form or in canonical form, respectively. It dynamically maintains the cache content by employing a profit function which reflects in an integrated manner the query execution cost, the size of query result, the reference rate, the maintenance cost of each result due to updates of their base tables, and the frequency of such updates. We performed the experimental evaluation and it positively shows the performance benefit of our cache manager.

• Journal of Power Electronics
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• v.11 no.3
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• pp.294-303
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• 2011

In this paper an effective five-phase induction motor (IM) and its drive methods are proposed. Due to the additional degrees of freedom, the five-phase IM drive presents unique characteristics for enhancing the torque producing capability of the motor. Also the five-phase motor drives possess many other advantages when compared to traditional three-phase motor drives. Some of these advantages include, reducing the amplitude and increasing the frequency of the torque pulsation, reducing the amplitude of the current without increasing the voltage per phase and increasing the reliability. In order to maximize the torque per ampere, the proposed motor has concentrated winding, the produced back electromotive force (EMF) is almost trapezoidal, and the motor is supplied with the combined sinusoidal plus the third harmonic of the currents. For demonstrating the superior performance of the proposed five-phase IM, the motors are also analyzed on the synchronously rotating reference frame. To supply trapezoidal current waveform and to exclude the effect of the $3^{rd}$ harmonic current, a new control stratagem is proposed. The proposed control method is based on direct torque control (DTC) and rotor flux oriented control (RFOC) of the five-phase IM drives. It is able to reduce the acoustical noise, the torque, the flux, the current, and the speed pulsations during the steady state. The DTC transient merits are preserved, while a better quality steady-state performance is produced in the five phase motor drive for a wide speed range. Experimental results clearly demonstrated a more dynamic steady state performance with the proposed control system.

• Journal of Power Electronics
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• v.18 no.1
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• pp.171-184
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• 2018

Unbalanced and distorted grid voltages cause the grid side current of a current source PWM rectifier to be heavily distorted. They can also cause the DC-link current to fluctuate with a huge amplitude. In order to enhance the performance of a current-source PWM rectifier under unbalanced and harmonic grid voltage conditions, a mathematical model of a current-source PWM rectifier is established and a flexible multi-objective control strategy is proposed to control the DC-link current and grid-current. The fundamental positive/negative sequence, $5^{th}$ and $7^{th}$ order harmonic components of the grid voltage are first separated with the proposed control strategy. The grid current reference are optimized based on three objectives: 1) sinusoidal and symmetrical grid current, 2) sinusoidal grid current and elimination of the DC-current $2^{nd}$ order fluctuations, and 3) elimination of the DC-current $2^{nd}$ and $6^{th}$ order fluctuations. To avoid separation of the grid current components, a multi-frequency proportional-resonant controller is applied to control the fundamental positive/negative sequence, $5^{th}$ and $7^{th}$ order harmonic current. Finally, experimental results verify the effectiveness of proposed control strategy.