A Study on Sloped Pulse Position Modulation Method in Underwater Laser Wireless Communication

수중에서는 매질의 특성 때문에 주로 음향통신기술을 사용한다. 하지만 음향통신기술은 여러 단점을 가지고 있다. 이러한 단점을 보안 할 수 있는 방법으로 광을 이용한 무선 통신 의 연구가 각광받고 있다. 무선 광 통신을 할 때의 채널 특성으로 흡수와 산란이 중요한 요소이다. 흡수와 산란을 최소화하는 것이 중요하다. 흡수의 영향을 최소화하기 위해 전자기 스펙트럼의 청록색 부분의 낮은 흡수 창을 활용한다. 산란 현상은 물 자체 보다 물속에 용해되어 있는 여러 물질과 입자에 의해 일어난다. 이때 산란에 많은 영향을 미치는 요소는 탁도이다. 지금까지 많은 연구들은 탁도를 고려하지 않은 환경에서 실험이 이루어졌지만 본 논문에서는 수조실험 시 물의 탁도를 고려하여 실험을 진행하였다. 또한 흡수와 산란에 따른 수중 감쇠 특성을 설명한다. 무선 광 통신을 할 때, 주로 쓰이는 방식은 펄스 위치 변조 방식과 온-오프 키잉 방식이다. 펄스 위치 변조 방식은 다양하게 변형하여 각각의 장점을 가진 변형된 펄스 위치 변조 방식이 있다. 본 논문에서는 기존의 사각 펄스을 이용한 방식이 아닌 기울어진 펄스를 이용한 새로운 방식을 제안하였다. 모의실험을 통해 기존의 방식과 제안된 방식을 비트 오류율 관점과 대역폭 효율 관점에서 성능을 비교 분석하였다. 비트 오류율 관점에서는 기존의 방식이 우수했지만 대역폭 효율 관점에서는 제안된 방식이 우수하였다.목 차 List of Tables ⅲ List of Figures ⅳ Abstract ⅴ 1. 서 론 1 2. 수중 광 채널특성과 광 소자 4 2.1 수중 광 채널 전달 특성 4 2.2 광원 및 광 검출기 7 3. 레이저 기반 수중 통신을 위한 신호전송 10 3.1 기존의 신호전송 방법 10 3.1.1 온-오프 키잉 방식 10 3.1.2 펄스 위치 변조 방식 11 3.1.3 변형된 펄스 위치 변조 방식 12 3.2 기울어진 펄스 위치 변조 방식 제안 15 4. 모의 및 수조실험 결과 20 4.1 모의실험 20 4.1.1 실험 설계 20 4.1.2 실험결과 21 4.2 수조실험 26 4.2.1 실험 설계 26 4.2.2 실험결과 28 5. 결론 33 참고문헌 35 감사의 글 38Maste

Effect of the Decarburized Area on Bendability in 1500-grade Hot-press-forming Steels

MasterThe hot-press-forming (HPF) steels, mostly used in the automotive industry, have bendability issues due to safety of passengers. Weight reduction of automotive parts is important in the upcoming years to reduce the fuel consumption with respect to minimize the CO_2 air pollution. Hot press forming has therefore received much attention recently as an alternative technology to produce advanced high strength steels (AHSS) automotive parts. Due to the advantages of the overcoming the manufactural limit of high-strength steels, HPF process is essential in automotive industry. HPF Steels are mostly used in the production part directly connected to the passenger safety such as A pillar, B pillar, bumper beam, and roof reinforce etc. HPF is the process forming steels in high temperature and afterward quenching them to room temperature. The process enables to form products with a complex geometry without shape deviations. Therefore, in this study, we investigate the effect of the decarburized area on bendability in 1500MPa-grade full martensitic HPF steels. The decarburized area of Zn coating HPF steels is formed at the galvannealing process in an oxidizing atmosphere unlike typical HPF steels which annealed in a reducing atmosphere. Because Al-Si coating and Zn coating are commonly used in HPF steels, three sheets, Al-Si coated, Zn coated, and Zn coated accompanying the decarburized area, are used in this study. Bendability is one of the properties representing the car crash performance. Bending test can therefore be used to evaluate and improve HPF steels parts abilities. HPF steels, however, should secure high strength because they are used as automotive parts. Therefore, the most important thing is to have good bending properties while ensuring a certain level of strengths. Investigating the crack initiation of bending test is essential because bending properties are defined as bend angles at the maximum load point. Microstructure appearance before the crack initiation would be observed, dividing into small intervals of bend angles. Existence of the decarburized area in HPF steels improves the bending characteristics while maintaining strengths, so it will be addressed through the microstructure analysis in this study

고강도 HPF강의 Bending 특성에 MnS가 미치는 영향 분석

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Microstructure Characterization of Adiabatic Shear Band Formed During High Strain Rate Deformation of Armor Steel

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수소 취성 저항성이 우수한 2.0GPa급 Nb-Mo 첨가 핫스탬핑강 개발

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Immunosuppressive Drug Measurement by Liquid Chromatography Coupled to Tandem Mass Spectrometry: Interlaboratory Comparison in the Korean Clinical Laboratories

Background: Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) is increasingly used for immunosuppressive drug tests. However, most LC-MS/MS tests are laboratory-developed and their agreement is unknown in different Korean laboratories. This interlaboratory comparison study evaluated test reproducibility and identified potential error sources. Methods: Test samples containing three concentrations of tacrolimus, sirolimus, everolimus, cyclosporine, and mycophenolic acid were prepared by pooling surplus samples from patients undergoing routine therapeutic drug monitoring and tested in duplicate in the participating 10 clinical laboratories. Reconstitution and storage experiments were conducted for the commonly used commercial calibrator set. The robust estimators of reproducibility parameters were calculated. Spearman's rank correlation coefficient (rho, rho) was used to evaluate the correlation between drugs. Multiple linear regression was used to determine whether the experimental conditions alter the calibration curves. Results: The reproducibility coefficient of variation exceeded 10% only for sirolimus concentrations 1 and 2 (10.8% and 12.5%, respectively) and everolimus concentrations 1 and 2 (12.3% and 11.4%, respectively). The percent difference values showed weak correlations between sirolimus and everolimus (rho=0.334, P=0.175). The everolimus calibration curve slope was significantly altered after reconstitution following prolonged 5 degrees C storage (P=0.015 for 14 days; P=0.025 for 28 days); the expected differences at 6 ng/mL were 0.598% for 14 days and 0.384% for 28 days. Conclusions: LC-MS/MS test reproducibility for immunosuppressive drugs seems to be good in the Korean clinical laboratories. Continuous efforts are required to achieve test standardization and harmonization, especially for sirolimus and everolimus