• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.8
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• pp.529-535
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• 2000

In this paper, a current control system of a single phase PWM AC/DC converter using a reduced-order Luenberger observer without source voltage sensors is proposed. The sinusoidal input current and unity input power factor are realised based on the estimated source voltage performed by the reduced-order Luenberger observer using actual currents and DC link voltage. The poles of the reduced-order Luenberger observer are placed in the left half plane of s-plane by the pole-placement method in order to acquire the stability of the observer. The magnitude and the phase of the estimated source voltage are used to accomplish the unity power factor. The proposed method is implemented by DSP(Digital Signal Processor). Experimental Results verify that the reduced-order observer estimates the source voltage without the estimation error and the control system accomplishes the unity power factor, and constant DC link voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.53-53
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• 2008

Piezoelectric transformers have been widely used such as DC-DC convertor, invertor, Ballast, etc. Because, the y have some merits compared with electro-magnetic transformers such as step-up ratio, high efficiency, small size and lg hit weight, etc. Piezoelectric transformer require high electromechanical coupling factor kp in order to induce a large out put power in proportional to applied electric field. And also, high mechanical quality factor Qm is required to prevent mechanical loss and heat generation. In general, PZT system ceramics should be sintered at high temperatures between 1200 and $1300^{\circ}C$ in order to obtain complete densification. Accordingly, environmental pollution due to its PbO evaporation. Hence, to reduce its sintering temperature, various kinds of material processing methods such as hot pressing, high energy mill, liquid phase sintering, and using ultra fine powder have been performed. Among these methods, liquid phase sintering is basically an effective method for aiding densification at low temperature. In this study, In order to comparis on low temperature sintering and solid state sintering piezoelectric transformers, rosen type transformers were fabricated u sing two PZT ceramics compositions and their electrical properties were investigated.

• Environmental Analysis Health and Toxicology
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• v.14 no.1_2
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• pp.45-54
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• 1999

Quantitative strucrure-activity relationships between the toxicity (LD$\_$50/) and molecular properties of amine and nitro compounds were tested. The all 19 compounds showed low correlations below 0.500 to their LD$\_$50/ values. When amine or nitro compounds were taken separately, the correlation between the calculated chemphysico parameters and LD$\_$50/ were also poor (r$^2$=0.4911, 3967 repectively). The overall relationships among the QSAR parameters were investigated. Molecular weight shows a high correlation with total surface area (r$^2$=0.9287); 0.9090 for zero-order connectivity and second-order connectivity : 0.8784 for bioconcentration factor and second-order connectivity. When amine compounds were taken to perform the statistical treatment, the relationships between parameters were as follows: 0.8436 for volume-negentropy; 0.8925 for volume-bioconcentration factor; 0.9929 for zero-order connectivity-Kow; zero-order connectivity-bioconcentration factor; 0.9141 for zero-order connectivity-solubility; 0.9718 for solubility-bioconcentration factor; 0.9894 for solubility-bioconcentration factor and 0.9319 for Kow-bioconcentration factor. On the other hand, nitro compounds showed different relationships as follows: 0.8952 for volume-I/O character; 0.9520 for volume-total surface area: 0.9351 for volume-molecular weight; 0.9351 for volume-MW; 0.9961 for Kow-Koc; 0.8455 for Kow-bioconcentration factor; 0.8879 for Koc-bioconcentration factor; 0.9987 for MW-total surface area respectively.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.259-261
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• 1996

In this paper, active input filter for power factor correction(PFC) circuit employing ripple arrent and voltage cancellation is proposed to reduce filter's size and cost, and to make filter design easy. Switching ripple current and voltage can be sensed through the secondary windings of filter inductor. Single stage passive filter can achieve high order filter characteristics by using active ripple current and voltage cancellation technique. Conventional high order passive filter and its problems are suggested. Analysis of active filter and design procedure are detailed. Simulation result is presented to verify high order filter characteristics of proposed scheme.

• Journal of the Korean Institute of Landscape Architecture
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• v.13 no.2
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• pp.37-70
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• 1985

The purpose of this study is to present objective basic data for environmental design by the quantitative analysis of visual quality emboded in physical environment. For this, as for the front garden of high schools, the spatial image was measured by the S.D. Scale Method, Factor Analysis was proceeded by the principal component analysis and the visual preference was investigated by the Paired Comparision Method. The scale values of plain and unpleasant road surface and external appearance of buildings, which are related to emotions of simpleness fell from straightness and stability, were found to be high. But, except for the road surface of Kyunggi High School, scale values of variables explaining the variation of the quality of materials, level of floor and rythm were generally low. For all green spaces, scale values of variables explaining the degree of pleasantness was found to be generally high. And, those explaining tidiness and characteristics of green spaces were not in the same tendency. But, the green spaces of Youngdong High school can be considered to the space with plenty of visual absorption uniqueness were high. As for the correlation between variables, variables for green spaces(12 and 26) and those for overall view of front garden( 1 and 4) revealed high positive correlation. Also, "order - disorder" and "convenient- incovenient" included in road surface variable can be regarded to have the same meaning since the correlation coefficient between them is very high, 0.7045. Image variables including road surface, external appearance of buildings, green spaces and overall view of front garden showed 91.21~61.08% of total variance. Thus, the remains can be considered to be the error valiance or specific variance. In Fctor I, II and III, main components explaining the road surface image of front gardens are order, hardness, texture, color, gradient and rythm. As for the external appearance of b wilding, variables of color, hardness, stability, peculiality and shape revealed high values of factor load. For all variables, communality was drastically high and ellen values and common variance were found to be very high in Factor I. As for the front gardens, variables explaining volume and peculiarity were found to be the main components of Factor I. In Factor II and III, variables of factor load were tidiness, pleasantness.

• Journal of Digital Convergence
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• v.11 no.3
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• pp.101-113
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• 2013

Although the methodological literature is replete with advice regarding the development and validation of multi-item scales based on reflective measures, the issue of index construction using formative measures has received little attention. The aim of this paper is to enhance researchers' understanding of formative measures of high-order factor and assist them in their index construction efforts. This article is also to provide some insights into the nature of formative indicators for researchers to reach an informed choice as to the appropriate high order formative measurement model for their needs. We first provide a brief background on formative indicators, drawing from the limited and fragmented literature on the topic. Next we give an example of constructing an index based on actual survey data and highlight the procedures used to assess its quality. We conclude the article with some thoughts about the use of indexes in empirical studies.

• 전기의세계
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• v.31 no.5
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• pp.383-390
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• 1982

The high power glass laser system was designed and constracted which consisted of a TEM$\_$00/ mode Q-switching oscillator, a pulse shaping, system, two-stage pre-amplifiers, five-stage main amplifiers, a Faraday rotator, and a uni-guide slit. The laser output of 3OGW with the pulsewidth of 2 nsec was obtained by performing the amplifiing experiment in this system. When the laser light with the pulsewidth of 10 nsec was amplified, the large factor of amplification was obtained in the beginning of pulse, but the factor of amplification decreased gradually in the later part of pulse. Therefore, the laser light which has short pulsewidth of-2nsec must be amplified in order to obtain the larger factor of amplification. When the laser beam from the high power glass laser system was irradiated to plasma, the reflected laser light from plasma which occured inevitably could be attenuated to the order of 10$\^$-4/ by using the Faraday rotator and the uni-guide slit.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.263-266
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• 2003

The high power factor converters are classified step-up, step-up-down and step-down converter, The power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. And the power system brings on a high efficiency and high power factor. When a switch of the step down converter is operated with a commercial frequency(60Hz), a reactor using the converter is gone with a great number of harmonics waveforms of low grade. As results of this, the converter is decreased input power factor and is increased system size. To improved these, this paper proposes a PSM(Pulse Size Modulation) control strategy operated with high power factor.

• Proceedings of the KIPE Conference
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• 1998.11a
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• pp.78-82
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• 1998

In this paper, the authors propose a current control system of single phase PWM AC/DC converter without the source voltage sensors. The sinusoidal input current and unity effective power factor are realised based on the estimated source voltage in the controller. The estimations of source voltage are performed based on the reduced-order Luenberger observer using actual currents. The estimated source voltage is used to accomplish unity power factor. The proposed method is proved by simulations

• Journal of Environmental Science International
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• v.17 no.4
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• pp.405-412
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• 2008

Statistical analysis technique was applied to operating parameters and removal efficiency data sets obtained from advanced wastewater treatment plant during 1 year. Through factor analysis three factors derived varimax rotation were selected each plant. Three components explained 96%, 87% of the total variance of the process, respectively. The components on $A_2O$ Plant were identified in the following order : 1) Shortening the SRT during high-flow period, 2) Keeping biomass high on winter 3) factor was related to DO. On DNR plant, we defined them as follows: factor 1, Prolonged the SRT during high-flow period; factor 2 was related to sludge return; factor 3, Influent BOD during low-DO period. This technique was believed to assist operators in identifying priorities to improve operation efficiency.