• 대한화학회지
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• 제54권6호
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• pp.829-834
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• 2010

• 한국전자파학회논문지
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• 제20권8호
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• pp.791-796
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• 2009

전기적으로 크면서 동시에 복잡한 구조인 제트 엔진의 산란 해석을 위해 하이브리드 IPO-MoM(Iterative Physical Optics-Method of Moments) 기법을 제시하였다. 이 기법에서 IPO 기법은 전기적으로 부드럽게 변하는 inlet 영역을, MoM 기법은 회전축과 회전날개를 포함한 전기적으로 복잡하게 변하는 영역을 해석하였다. 각 기법의 장점을 융합하여 상대적으로 효율적이고 정확한 해석이 가능하였다. 수치 결과를 제시하고 기존 Mode-FDTD, 측정 결과와 비교하여 제시한 기법을 검증하였다.

• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.101-108
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• 2016

The RCS characteristics of stealth modified three-surface aircraft are analyzed in this paper. Prototype A is built with CATIA software and the three-dimensional digital models of modified stealth three-surface B and C are also designed based on carrier-based aircraft Su-33; the numerical simulation of RCS characteristics of three-surface aircraft is conducted with RCSAnsys software based on physical optics method and the method of equivalent currents; The following results are obtained by comparative analysis and mathematical statistics: (1) by the use of physical optics method and equivalent electromagnetic current method, the scattering intensity for each part of the model and RCS characteristic of the aircraft can be analyzed efficiently and accurately; (2) compared with model A, the mean RCS value of model B is reduced to 14.1% in forward direction and 48.1% in lateral direction; (3) compared with model A, the mean RCS value of model C decreases to 11.4% in forward direction and 21.6% in lateral direction. The results are expected to provide theoretical basis and technical support to the conceptual design of aircraft and stealth technology research.

• 센서학회지
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• 제15권4호
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• pp.269-276
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• 2006

This paper represents development of quartz crystal microbalance (QCM) and usage as a dew point sensor. The temperature of a quartz resonator was controlled precisely from $20^{\circ}C$ to $-30^{\circ}C$ with the ramping rate of $0.1^{\circ}C/s$ by using a custom-made crystal holder housing the quartz resonator associated with a thermoelectric cooler (Peltier cooler), which results in the working range from $15.2^{\circ}C$ to $-24.0^{\circ}C$ based on an accurate holder temperature compensation and temperature effect compensation process. The developed QCM dew point sensor and analysis techniques show very good sensing characteristics at measurement of moist air with the relative humidity from 10 %R.H. to 90 %R.H. generated by a divided-type humidity generator and the dew point temperatures were determined with an accuracy of less than ${\pm}0.18^{\circ}C$, which also showed good agreement with reference values in their error range.

• 대한조선학회논문집
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• 제42권2호
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• pp.159-164
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• 2005

Monostatic RCS analysis of complex structures has been done with a combined method of physical and geometric optics, commonly applied to high frequency electromagnetic backscattering problems. In the analysis, the complex structure is modeled as a number of flat surfaces and the RCS of whole structure is calculated by summing RCS of each surface, which can be obtained from an analytical solution of flat surface phase integral derived from physical optics. The reflected and hidden surfaces are searched by an object precision method based on adaptive triangular beam method, which can take account for effects of multiple reflections and polarizations of electromagnetic wave. The validity of the presented RCS analysis method has been verified by comparing with exact solutions and measured data for various structures.

• 통합자연과학논문집
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• 제8권1호
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• pp.60-66
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• 2015

The physical and optical properties of polymers with 2-fluoroaniline and 4-fluoroaniline added, which can be used for hydrophilic ophthalmic lenses, were investigated in this study. The UV-blocking properties of 2- and 4-fluoroaniline were also investigated by measuring their UV transmissibility. 2- and 4-Fluoroaniline were used as additives for the basic combination of HEMA, 5% AA, and 1% MMA, and the materials were copolymerized with EGDMA as the cross-linking agent and AIBN as the initiator. The refractive index, water content, optical transmittance, tensile strength, and contact angle were measured to evaluate the physical properties of the produced hydrogel lens. The measured physical properties of the hydrogel contact lens produced with the copolymerized polymer showed a refractive index of 1.425-1.436; a water content of 36.95-44.65%; a visual light transmittance of 66.0-81.0%; a tensile strength of 0.138-0.281 kgf; and a contact angle of $55.02-57.87^{\circ}$. The UV transmissibility was significantly reduced, which indicates that 2-fluoroaniline and 4-fluoroaniline have UV-blocking properties. This study showed that 2- and 4-fluoroaniline are expected to be used as UV-blocking materials in hydrogel ophthalmic lenses whose physical properties, such as their refractive index and water content, do not change.

• 한국안광학회지
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• 제11권2호
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• pp.143-149
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• 2006

본 연구의 목적은 콘택트렌즈의 재료로 사용되는 실리콘 고분자를 합성하여 실리콘 재질의 가스 투과성 콘택트렌즈의 함수율과 광 투과성의 문제를 해결하는 데에 있다. 실험에 사용된 monomer들로는 NVP(N-vinly-pyrrolidone), MMA(methyl methacrylate), HEMA(Hydroxyethylmethacrylate)등과 교차결합제로 EGDMA(Ethylene Glycol Dimethacrylate)를 사용하였으며, 또한 콘택트렌즈 제조의 가장 좋은 조건을 위한 많은 조합 공식을 토대로 중합한 후, 중합된 개체를 가지고 함수율 측정과 광투과율 측정을 실시하였다. 본 실험의 연구 결과 재질의 투명성과 함수율을 동시에 추구하는 고분자를 합성하였고 그들의 물성을 측정하였다.

• 한국정밀공학회지
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• 제27권6호
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• pp.7-16
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• 2010

Physical fundamentals of ultrashort femtosecond lasers are addressed along with emerging applications for precision manufacturing and metrology. Femtosecond lasers emit short pulses whose temporal width is in the range of less than a picosecond to a few femtoseconds, thereby enabling extremely high peak-power machining with less thermal damages. Besides, the broad spectral bandwidth of femtosecond lasers constructed in the form of frequency comb permits absolute distance measurements leading to ultraprecision positioning control and dimensional metrology.

• 한국안광학회지
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• 제19권1호
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• pp.43-49
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• 2014

목적: 본 연구는 glycerin과 PVP(polyvinylpyrrolidone)을 각각 첨가제로 사용하였을 때 친수성 콘택트렌즈의 물성 변화를 평가하였다. 방법: Glycerin과 PVP(polyvinylpyrrolidone)를 각각 첨가제로 사용하여 교차결합제인 EGDMA (ethylene glycol dimethacrylate) 기본적인 모노머인 HEMA(2-hydroxyethyl methacrylate)와 그리고 개시제인 AIBN(azobisisobutyronitrile)을 기본 조합으로 하여 공중합하였다. 결과: 생성된 고분자의 물리적 특성을 측정한 결과 PVP(polyvinylpyrrolidone)의 경우, 굴절률은 1.4382~1.4288로, 인장강도는 0.3446~0.2542 kgf로 각각 감소하였으며, 접촉각은 21.44% 감소되고 함수율은 13.49% 증가하였다. 또한 glycerin의 경우, 굴절률 1.4330~1.4328로, 인장강도는 0.2974~0.2854 kgf로, 함수율은 35.58~36.53%로 큰 변화를 보이지 않았으며, 접촉각의 경우 37.64%가 감소되었다. 결론: 본 실험결과로 볼 때, 생성된 공중합체는 고 습윤성 안 의료용 렌즈 재료로 사용이 가능하며, 또한 glycerin을 첨가제로 사용하였을 때, 함수율과 굴절률의 변화를 최소화시킴과 동시에 친수성 렌즈의 습윤성을 증가시켰다.

• Journal of the Optical Society of Korea
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• 제19권6호
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• pp.695-699
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• 2015

A high spectral resolution lidar (HSRL) system based on injection-seeded Nd:YAG laser and iodine absorption filter has been developed for the quantitative measurement of aerosol and cloud. The laser frequency is stabilized at 80 MHz by a frequency locking system and the absorption line of iodine cell is selected at the 1111 line with 2 GHz width. The observations show that the HSRL can provide vertical profiles of particle extinction coefficient, backscattering coefficient and lidar ratio for cloud and aerosol up to 12 km altitude, simultaneously. For the measured cases, the lidar ratios are 10~20 sr for cloud, 28~37 sr for dust, and 58~70 sr for urban pollution aerosol. It reveals the potential of HSRL to distinguish the type of aerosol and cloud. Time series measurements are given and demonstrate that the HSRL has ability to continuously observe the aerosol and cloud for day and night.