• Macromolecular Research
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• 제9권6호
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• pp.313-318
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• 2001

The present study relates to a method of manufacturing 100$\mu\textrm{m}$ thick cover layer for the high density digital versatile disc system (HD-DVD), which uses a high numerical aperture of 0.85 at 405 nm wavelength. Spin coating technique was investigated as means for manufacturing the cover layer within sufficient margins of thickness variation and with good mechanical properties including small radial and tangential tilts. The influence of processing variables such as spinning speed, spinning time, and dispensing position was investigated. The effect of viscosity of UV-curable resin was also investigated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.1938-1939
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• 2001

시스템을 입력과 출력간의 함수관계로 볼 때 출력에 대한 상대차수가 정의되지 않는 점을 특이점이라고 정의할 수 있다. 본 논문에서는 적절한 기하학적 조건을 만족하는 해석적인 시스템(analytic system)에 대하여 그러한 특이점의 성질을 살펴본다. 특이점을 지나는 궤적은 특이점의 특이도와 그에 관련된 함수 값의 부호에 의해서 특이점의 주변에서는 특이 매니폴드를 기준으로 한 영역에서 나머지 다른 영역으로 통과하거나 혹은 그를 기준으로 어느 한 쪽의 영역에만 머물러 있게 됨을 보임으로써 특이점과 이를 지나는 궤적의 상관관계를 명확히 규명하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2008-2010
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• 2001

최근에 광 디스크 기기의 고배속화에 따라서 디스크의 재생 속도는 점차로 증가하고 있다. 이러한 경향에 따라 트랙킹 제어 루프에서 나타나는 디스크의 편심에 의한 외란의 영향은 더욱 커지게 되므로 기존의 선형 제어기만으로는 디스크의 편심량이 큰 경우에 고배속에서 원하는 트랙 추종 성능을 얻을 수가 없다. 본 논문에서는 이러한 문제점을 해결하기 위해서 반복 학습 제어 알고리즘과 드라이브 시스템의 액츄에이터의 주파수 응답 특성을 이용한 새로운 트랙 추종 제어 방법을 제안한다. 또한, 제안된 트랙 추종 제어 시스템의 제어 성능을 실험을 통하여 검증하여 본다.

• Smart Structures and Systems
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• 제3권2호
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• pp.173-188
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• 2007

The general solution for two-dimensional magneto-electro-elastic media in terms of four harmonic displacement functions is proposed analytically. The expressions of specific solutions of magneto-electro-elastic plane problems with specific body forces are derived. Finally, based on the general solution in the case of distinct eigenvalues and the specific solution for density functionally gradient media, two kinds of beam problems with body forces depending only on the z or x coordinate are solved by the trial-and-error method.

• 한국자기학회지
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• 제5권5호
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• pp.690-694
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• 1995

Reducing media noise is a key to realizing high areal recording density. However, perpendicularly oriented Co-Cr films, stong candidates for high density recording media, have received little attention in terms of recording noise. We studied the noise characteristics of Co-Cr based alloy films by varying the compositionally separated structure. Co-Cr films with fine compositionally separated microstructure were observed to have low noise, which recording density dependence were negative or week. Studies on control of the microstructure and magnetic properties in combination with noise analysis are important to realize high density recording media.

• Clinical and Experimental Reproductive Medicine
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• 제46권1호
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• pp.8-13
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• 2019

Objective: Density gradient centrifugation (DGC) is frequently used to isolate high-motility fractions of spermatozoa. We compared the efficacy of four DGC media in terms of the percentage of morphologically normal spermatozoa, DNA fragmentation level, and hyaluronic acid (HA) binding ability. Methods: Thirty men with a total motile spermatozoa count > 80 million participated. Semen samples were divided into four aliquots, which were processed using PureSperm, PureCeption, Sidney, and SpermGrad media, respectively. The DNA fragmentation level was measured using the Halosperm assay kit and HA binding ability was measured using the HBA assay kit. Results: The mean percentage of morphologically normal spermatozoa was significantly enhanced after DGC using all four media (10.3%, 9.9%, 9.8%, and 10.7%, respectively; p< 0.05 for each when compared with 6.9% in raw semen). The DNA fragmentation level was significantly reduced after DGC using PureSperm, PureCeption, and SpermGrad media (6.0%, 6.5%, and 4.9%, respectively; p< 0.05 for each when compared with 11.2% in raw semen), but not after DGC using Sidney media (8.5%, p> 0.05). HA binding ability did not change after DGC using any of the four media. Conclusion: The four media were equally effective for obtaining a sperm fraction with highly motile, morphologically normal sperm. PureSperm, PureCeption, and SpermGrad media were equally effective for acquiring a sperm fraction with less DNA fragmentation.

• 한국자기학회지
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• 제5권5호
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• pp.650-654
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• 1995

In digital video recording, higher areal density is strongly required for realizing digital VCRs. In order to accomplish higher areal density. we have implemented a system that has a narrow track pitch and can record data of about 30 Mbps(15 Mbps per channel) with the conventional S-VHS tapes. After computer simulation using the characteristics of the experimental system, we have selected appropriate equalizer and detection method by taking into account performance and cost (including hardware complexity). As a result, the selected equalizer and detection schemes are cosine equalizer and integrated de tection, respectively. The implemented system confirms reliable operation with a symbol error rate of less than $1{\times}10^{-4}$. In this paper, We will show the performance of the implemented system together with simulation results.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.825-827
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• 2002

The polymer encapsulation of white inorganic $TiO_2$ pigment particles was prepared by a two stage dispersion polymerization technique for applications in electrophoretic displays (EPDs). In order to give functionality for inorganic pigment particles in the EPD, we have investigated the density of the polymer encapsulated $TiO_2$ particles. The average density of the polymer encapsulated $TiO_2$ particles was 2.2 at 25$^{\circ}C$. The average density of the polymer encapsulated $TiO_2$ particles is suitable to 1.7, due to density matching with suspending media. Therefore, we will attempt density compatibility of dispersion polymerization technique for encapsulation of $TiO_2$ particles in suspending media.

• 한국융합학회논문지
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• 제9권9호
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• pp.41-46
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• 2018

식스 시그마 기법은 제품과 서비스의 품질관리와 원가 절감을 통한 생산성 향상 뿐만 아니라, 연구개발을 비롯한 기업 경영의 다양한 영역에 적용할 수 있는 관리 기법이다. 또한 정보 융합 시대의 실현을 위하여 고밀도 정보저장 매체 및 장치의 개발은 필수적 요건이다. 본 논문에서는 고밀도 정보저장 매체 개발 과제에 식스 시그마 방법론과 기법을 적용한 사례에 대하여 보고하고자 한다. 식스 시그마 프로세스는 표준적으로 사용되는 DMAIC 프로세스를 적용하였으며 각 단계별로 달성하고자 하는 목표와 적용한 도구 및 결과에 대하여 상세히 설명하였다. 본 기법을 활용함으로써 $250Gb/in^2$ 이상의 높은 기록밀도를 갖는 정보저장 매체를 균일하고 재현성 있게 형성할 수 있는 제조 방법을 확립하였으며, 제조된 매체의 자기적 특성과 성능을 자기이력곡선을 통하여 확인하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권2호
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• pp.244-251
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• 2009

Porous media have especially large surface area per volume, which contain complex fluid passage. If porous media can be applied to cool a CPU or an electronic device with large heat dissipation, it could result in heat transfer enhancement due to the enlargement of the heat transfer area and the flow disturbance. This study is aimed to identify the heat transfer and pressure drop characteristics of high-porosity metal foams in a horizontal channel. Experiment is performed with the various heat flux, velocity and pore density conditions. Permeabilities, which is deduced from Non-Darcy flow model, become lower with increasing pore density. Nusselt number also decreases with higher pore density. High pore density with same porosity case shows higher pressure loss due to the increase of surface area per unit volume. The fiction factor decreases rapidly with increase of Reynolds number in Darcy flow region. However, it converges to a constant value of the Ergun coefficient in Non-Darcy flow region.