• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.410-415
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• 2007

The optimization of back pressure chamber is one of the most important factors in designing scroll compressors, because it has a great influence on the efficiencies and other design parameters. The design process can be divided into 2 parts. One is obtaining the optimum pressure of the chamber and keeping it in constant value. And the other is finding out the minimum inflow rate of medium with which back pressure chamber is filled. In this study we are focused on the first step. At first we added a simple structure that could change back pressure without reassembling compressor. It makes the optimum back pressure be obtained. And then we devised an equipment that the back pressure control valve assembly could be independently tested with. A spring was redesigned to decrease stiffness variation. And sealing mechanism of back pressure control valve was improved to more effective way. As a result it was verified in a real mode test that back pressure variation could be stabilized within 2.3% when discharge pressure and operating frequency varied. And the integrated structure of back pressure control valve is expected to contribute to an effective manufacturing process.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.275-280
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• 2008

The effects of the surfactant type, i.e., CTAB(cationic), SDS(anionic), and GA(polymeric), on the stability of 0.1 vol.% $Al_2O_3$ nanofluids were investigated. The changes in size and zeta potential of nanoparticles in nanofluids with pH, surfactant concentration, and time were experimentally observed. The nanofluids adding CTAB, which ionizes of the same charge with the bare particle surface, was found to have the best stability regardless of the surfactant concentration, whereas those with SDS became unstable under low surfactant concentration conditions, i.e. lower than the critical micellel concentration(CMC), before the charge reversal occurred. With higher SDS concentration over CMC, they became stable. Gum Arabic, which had been used often to stabilize the nanofluids, was also tested. In result, it was found that the type and concentration of surfactants to add should be selected considering pH and the sign of the bare particle surface charge.

• Proceedings of the Safety Management and Science Conference
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• 2004.11a
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• pp.415-438
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• 2004

This dissertation is assumed to continuously occur adjustment cost on present investment. So, I derived from time-nonseparable production-based CAPM and tested the performance of model through data. I also compared time-nonseparable production-based CAPM with time-separable production-based CAPM and CCAPM, CAPM through testifying the performance of model. At the part of applied application, I estimated time-nonseparable PCAPM-betas. The data of Korea consists of 320 listed companies on Korea Stock Exchange (KOSPI) from first quarter 1987 to first quarter 2002. This data also is categorized by scale and industries. Additionally, I estimated time-nonseparable PCAPM-betas through 500 listed companies of New York Stock Exchange (NYSE) from first quarter 1973 to first quarter 2002. I observed the statistical significance of 230 firms by 320 companies in Korea. After that, I compared time-nonseparable PCAPM-betas by firms with time-separable production-based CAPM-betas and CCAPM-betas, CAPM-betas through individual firms. At empirical test, I found that estimated parameter of adjustment cost on time-nonseparable production-based CAPM by scale and industries in Korea had positive value and statistical significance, Moreover, this approach proved to resolve the underestimation of adjustment cost on time-separable production-based CAPM by scale and industries. I also found that the time-nonseparable PCAPM performed better than time-separable production-based CAPM and CCAPM, CAPM. The result from U.S data proved to have similarity to that of Korea. Specifically, I found that time-nonseparable PCAPM-betas by firms performed better than CAPM-betas on individual firms in Korea.

• Journal of Magnetics
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• v.16 no.3
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• pp.312-317
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• 2011

NMR over 1 GHz (23.5 T) level has difficulties in design and fabrication with only low temperature superconducting (LTS) wire because of its material characteristics such as the decay of critical current under the magnetic field. Because High temperature superconducting (HTS) tape has a good performance under the extremely high magnetic field, it has been developed for high-field magnet over 23.5 T. In this paper, the LTS magnet was made for applying magnetic fields externally and the HTS coil was designed and fabricated. The electromagnetic field analysis has been done with respect to the structure and the operating current of the LTS and HTS coil. Considering to the field homogeneity and the center field, the design parameters which is suitable for the HTS coil were found. The HTS insert coil was impregnated with epoxy resin in order to prevent the movement of winding during energizing the magnet. The hybrid magnet (LTS/HTS) magnet was fabricated and tested based on the design parameters. The experimental result shows that the LTS background magnet and the HTS insert coil can be operated stable beyond 220 A and 210 A. The final value 4.32 T at the center was acquired.

• Journal of the Korea Society of Computer and Information
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• v.23 no.2
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• pp.27-34
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• 2018

In this paper, we propose a new method to read the hand of analog gauges to prepare for the smart factory. In addition, we suggest a new and improved method that can apply, in general, diverse analog gauges even if their scale types and ranges are various. Many companies are making great efforts to build smart factories that increase energy efficiency and automation. Managers use a variety of equipment and tools to manage the production process at the factory. In this kind of factory, analog gauges have been often used with many equipment and tools. Analog gauges are mostly circular in shape, and most papers use circular hough transform to find the center and radius of a circle. However, when the object to be found is not of the correct circle type, it takes a long time to recognize the circle using the circular hough transform, and the center and radius of the circle can not be calculated accurately. The proposed method was tested on various circular analog gauges. As a result, we confirmed that our method is outstanding.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.1
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• pp.34-41
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• 2014

When a ship sails in shallow water, it is well known that an additional sinkage and trim of the ship(squat) is caused by change of hydrodynamic force between the seabed and the bottom of a ship. In this paper, to examine this phenomenon by model tests, the squat of KCS model ship at a low speed is measured by the vision based ship motion measurement system during HPMM tests. Various combinations of a ship speed, a rudder angle and a drift angle were tested at three depth conditions(H/T = 1.2, 1.5 & 2.0). As a result, increase of the ship's speed and ship's drift angle caused an increase in ship squat, but the ship's rudder angle did not. The rate of increase in ship squat was the most at H/T = 1.2 condition. Lastly these experimental results are compared to the results by three empirical formulas and two CFD methods. The tendency of ship squat measured by experiment is similar to those of empirical formulas.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1993.05a
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• pp.87-87
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• 1993

Polymerase chain reaction is widely used as a powerful tool in modern molecular biology. As there is agreement that the HPV is an important factor in the head and neck cancers, the detection of HPV DNA sequence in the head and neck cancer tissue has been tried in several ways. We used the PCR to detect the E1 open reading frames of the HPV in paraffin-embedded tissue of the patients with the head neck cancers. Eleven of the fifty-four tested samples (30%) showed positive result. We have analysed the clinical courses and characteristics related with Human Papillomavirus in those patients.

• Journal of the Semiconductor & Display Technology
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• v.11 no.2
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• pp.1-6
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• 2012

In this study, a high performance rotary magnet type magnetron source for roll-to-roll sputter system has been developed. We analyzed the density of magnetic field as a function of size variation of the magnet which are in the center and edge of the target. The target efficiency showed the best result when the width of center magnet, the width of edge magnet, the angle of edge magnet, and the rotation angle of Yoke are 20mm, 10mm, $56^{\circ}$, and $16^{\circ}$, respectively. On the basis of the results of magnet array, Roll-to Roll magnetron source was fabricated and tested. The uniformity of the film thickness and that of the sheet resistance was ${\pm}1.62%$ and ${\pm}4.13%$, and the resistivity was $2.79{\times}10^{-3}W{\cdot}cm$.

• Journal of the Semiconductor & Display Technology
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• v.12 no.2
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• pp.27-32
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• 2013

Shape From Focus (SFF) is a passive optical technique to recover 3D structure of an object that utilizes focus information from 2D images of the object taken at different focus levels. Mostly, SFF methods use a single focus measure to compute image focus quality of each pixel in the image sequence. However, it is difficult to recover accurate 3D shape using a single focus measure, as different focus measures perform differently in diverse conditions. In this paper, a nonlinear Total Variation (TV) based approach is proposed for 3D shape recovery. To improve the result of surface reconstruction, several initial depth maps are obtained using different focus measures and the resultant 3D shape is obtained by diffusing them through TV. The proposed method is tested and evaluated by using image sequences of synthetic and real objects. The results and comparative analysis demonstrate the effectiveness of our method.

• The Journal of Information Systems
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• v.16 no.3
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• pp.45-68
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• 2007

This study aims to explore factors of Assimilation Gap(AG) which is proposed and illustrated by Fichman and Kemerer(1997). AG is defined as the time delay between adoption and deployment and mainly studied at the organizational level. This study derives the factor affecting AG through a review of technology acceptance models and agency theory. The research model consists of three groups of independent variables(IT knowledge burden, Individual characteristics, and organization characteristics) and a moderator, which is goal incongruence. Using multiple regression analyses, four groups of hypotheses are tested with data of 221 knowledge workers from various organizations through e-mail survey. The result shows that radicalness(a dimension of knowledge burden), personal innovativeness, self-efficacy, and organizational support are statistically significant factors while complexity, experience, and perceived critical mass are not supported. The moderator effects of goal incongruence are found in personal innovativeness and organizational support. The results of this study demonstrate that agency theory is a useful perspective to deal with AG, especially in radical innovation. In addition, IT practitioners should consider not only user training but also incentives and possible organizational controls in implementing a new information technology.