• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.281-281
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• 2010

Very low refractive index (<1.4) materials have been proved to be the key factor improving the performance of various optical components, such as reflectors, filters, photonic crystals, LEDs, and solar cell. Highly porous SiO2 are logically designed for ultralow refractive index materials because of the direct relation between porosity and index of refraction. Among them, ordered macroporous SiO2 is of potential material since their theoretically low refractive index ~1.10. However, in the conventional synthesis of ordered macroporous SiO2, the time required for the crystallization of organic nanoparticles, such as polystyrene (PS), from colloidal solution into well ordered template is typical long (several days for 1 cm substrate) due to the low interaction between particles and particle - substrate. In this study, polystyrene - polyacrylic acid (PS-AA) nanoparticles synthesized by miniemulsion polymerization method have hydrophilic polyacrylic acid tails on the surface of particles which increase the interaction between particle and with substrate giving rise to the formation of PS-AA film by simply spin - coating method. Less ordered with controlled thickness films of PS-AA on silicon wafer were successfully fabricated by changing the spinning speed or concentration of colloidal solution, as confirmed by FE-SEM. Based on these template films, a series of macroporous SiO2 films whose thicknesses varied from 300nm to ~1000nm were fabricated either by conventional sol - gel infiltration or gas phase deposition followed by thermal removal of organic template. Formations of SiO2 films consist of interconnected air balls with size ~100 nm were confirmed by FE-SEM and TEM. These highly porous SiO2 show very low refractive indices (<1.18) over a wide range of wavelength (from 200 to 1000nm) as shown by SE measurement. Refraction indices of SiO2 films at 633nm reported here are of ~1.10 which, to our best knowledge, are among the lowest values having been announced.

• 한국음향학회지
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• 제41권2호
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• pp.131-142
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• 2022

본 연구에서는 동해 수심변화가 큰 해양환경 하에서 음파의 수평굴절 모의 가능성을 고찰하고자 포물선방정식 기반의 3차원 모델을 도입한다. 이 모델은 상관항과 비상관항을 분리함으로써 근사적 해를 제공한다. 가상 수심분포(25 km × 4 km)에 대해 주파수 75 Hz인 음원을 가정하여 모의한 결과는 전달손실의 수평분포 상 분명한 수평굴절을 보인다. 이 굴절 정도는 전파 거리에 비선형적으로 증가하고 횡방향 수심 경사도에 비례하여 증가한다. 실제 수심분포(25 km × 8 km)에 대한 모의 결과도 이러한 수평굴절을 잘 보인다. 수평굴절은 동일 자료 내에서는 해상도별로 수평음장분포가 크게 변하지 않는데, 이는 모델이 모의 전 수심자료에 대해 내삽을 하기 때문이다. 반면, 수심자료 종류가 다를 경우 수평음장 분포는 크게 달라진다.

• 한국학교보건학회지
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• 제1권1호
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• pp.114-132
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• 1988

Aiming to appraise student's health status and recommend improvement and strengthening of the school health services, statistical analysis of the results of health examination were done with summarized data which were collected nation-wide through the Ministry of Education. After analysis of data obtained, the results of the study summarized as follows; 1) Requested Adequate care Requested Adequate care showed from 5 % to 3% in 1962 and 1984 respectively. In sexes, Requested Adequate in girls (2.8%) more apparent than in boys (2.5%) 2) Eyes i) Weak vision, abnormal refraction of eyes (myopia, hypermetropia and astigmatism), eye diseases (trachoma, others) were found as shown in the Table 2, Figure 3. Weak vision and abnormal refraction of eyes showed from 2 % (Elementary), 5 % ( Secondary) to 4 % (Elementary), 14 % (Secondary) in 1962 and 1984 respectively. In both sexes, the older the age of students the more weak vision and abnormal refraction of eyes had rapidly increased especially in over 15-year old. ii) Eye diseases (trachoma, others) showed from 2% to age of students the more diseases had students. 3) Ear, nose and pharynx Hearing disturbance, ear diseases (otitis mediae, others), nose (empyema, hypertrophy) and pharynx diseases were found as following 1) Hearing disturbance was found from 0.3%(Elementary), 1 %(Secondary) to 0.05 % (Elementary), 0.4 % (Secondary) in 1962 and 1984 respectively, however, recently the older the age of students the more had students. ii) Ear diseases showed from 1.7 % (Elementary) 1.0 % (Secondary) to 0.3 %(Elementary), 0.5%(Secondary) in 1962 and 1984 respectively. iii) In diseases of the nose and pharynx, tonsilitis showed from 2.5% (Elementary), 3.5 % (Secondary) to 1.8 % ( Elementary). 2.5% (Secondary) in 1962 and 1984 respectively. 4) Skin Infectious skin diseases and other skin diseases were found from 1.5% to 0.6% in 1962 am 1984 respectively. 5) Teeth Dental caries (in milk and permanent teeth) and otner oral diseases are shown from 12 % (Elementary), 8%(Secondary) to 75%( Elementary), 25% (Secondary) in 1962 and 1984 respectively. 6) Other defects and diseases A relatively higher morbidity was shown in the tubercular diseases, in anemia, and in heart diseases among the tuberculous diseases, nodular diseases, Pleurisy, heart diseases, anemia, beriberi, hernia, neurasthenia, speech difficulty, mental disorders, bone dysformity, motion difficulty of extremities. In both sexes, tuberculous diseases were found almost equally in both sexes and anemia in girls was more apparent than in boys. Trying to provide more effective health services in schools : i) A better and more effective physical examination should be carried out in each school and prior to the physical examination, the qualified daily observation of children by teacher should be keenly practiced. ii) According to the results of the required annual physical examination the leading cause of morbidity were dental caries, myopia, angina and otitis mediae and fore these diseases follow up should be carried out. iii) For prevention and treatment of diseases and defects health education for students in the classroom as well as to parents is urgently requested.

• 한국안광학회지
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• 제4권2호
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• pp.129-133
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• 1999

굴절이상인 근시안의 종류별 분포는 전체 대상자 100명 중 단순근시 50%, 근시성 복난시 16%, 근시성 단난시 15%, 혼합난시 19%의 순으로 나타났다. 양안 굴절이상인 근시의 분포는 -0.50~-2.00Dptr가 전체 대상자중 35%, -2.00~-6.00Dptr가 54%, -6.00Dptr이상이 11%로 나타났다. 연령별 근시성 굴절이상의 분포는 15세~20세가 54%, 21세~40세가 22%, 41~60세다. 16%, 61 세 이상이 10%였다. 근시성 굴절이상도의 직업분포는 학생(중, 고, 대학)이 61.5%, 사무직 13.5%, 주부 및 상업이 15%로 분포되어 나타났다. 하루중 굴절이상에 영향을 많이 미치는 시각때는 저녁인 오후 7시 이후가 45%로 가장 높게 나타났다. 그 이유는 오전에는 각막이 평평해져서 근시도가 줄어들고 오후에는 그 반대가 되어 Sph -0.50D의 차이가 나기 때문이며, 어두워질수록 동공이 확대되면서 각막이 주변부에서 굴절되는 빛의 굴절도가 큰 것이 이유가 된다. 계절별로는 땀의 배출로 인한 인체에서의 영양섭취와 배출의 부족함으로 인한 여름이 근시도수를 증가시켜 68%로 나타났다. 혈액형 별로는 A형과 B형이 34%로 비슷하게 분포되었으며, 남성은 활동적인 O형이 여성에 비해 근시도수가 높게 측정되었다.

• 대한화학회지
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• 제56권1호
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• pp.20-27
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• 2012

Complex permittivity spectra of Allyl Chloride (AC), 2-Butanone (2-BU) and their binary mixtures over the entire range of concentration were obtained using the Time Domain Reflectometry (TDR) technique in microwave frequency range at various temperatures. Static dielectric constant and relaxation time are obtained from complex permittivity spectra. Density ($\rho$) and refractive index ($n_D$) are also measured. These parameters are used to determine excess dielectric constant, excess inverse relaxation time, excess molar volume, excess molar refraction, polarity, Bruggeman factor and thermodynamic parameters viz. enthalpy of activation and entropy of activation. The values of static dielectric constant and relaxation time increases while density and refractive index decreases with the percentage of 2-Butanone in Allyl Chloride increases. Excess parameters were fitted to a Redlich-Kister equation.

• 천문학회지
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• 제36권spc1호
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• pp.101-107
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• 2003

The magnetosphere is often perturbed by impulsive input such as interplanetary shocks and solar wind discontinuities. We study how these initial perturbations are propagating within the magnetosphere over various latitude regions by adopting a three-dimensional numerical dipole model. We examine the wave propagation on a meridional plane in a time-dependent manner and compare the numerical results with multi-satellite and ground observations. The dipole model is used to represent the plasmasphere and magnetosphere with a realistic Alfven speed profile. It is found that the effects of refraction, which result from magnetic field curvature and inhomogeneous Alfven speed, are' found to become important near the plasmapause. Our results show that, when the disturbances are assumed at the subsolar point of the dayside magnetosphere, the travel time becomes smaller to the polar ionosphere compared to the equatorial ionosphere.

• 한국해안해양공학회지
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• 제8권3호
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• pp.246-255
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• 1996

2차 미분항을 보정하는 포물선형 완경사 방정식을 유도하여 광역에 적용할 수 있는 새로운 접근 방법을 제시한다. 즉, 어느 주기의 파에 대해서도 충분히 큰 파의 주기로 대체되도록 하여 격자의 제약으로 인한 어려움이 제거되었다. 큰 주기의 파로 변형시키되 파속이 유지되도록 파장을 늘리고 또한 파의 군속도도 유지시켜 큰 격자에 대해서도 파의 천수 및 굴절 현상이 제대로 반영되도록 하였고 파의 회절현상은 실제 입력조건에 의한 결과와 근사한 결과를 낳도록 시도되었다. 개발된 본 수치 모형은 파랑에너지의 집중(focus)을 유발하는 Ito and Tanimoto(1972)의 천퇴구조에 적용되어 만족할 만한 결과를 얻었다.

• 한국해안해양공학회:학술대회논문집
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• 한국해안해양공학회 1996년도 정기학술강연회 발표논문 초록집
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• pp.109-114
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• 1996

In a linear dispersive system, the combined effect of water wave frnnsformations such as refraction, diffraction, shoaling, and reflection can be predicted by the mild-slope equation which was developed by Berkhoff (1972) using the Galerkin-eigenfunction method. In the derivation of the equation, he assumed a mild slope of the bottom $\nabla$h/kh << 1 (where $\nabla$ is the horizontal gradient operator, k is the wavenumber, and h is the water depth) and thus neglected second-order bottom effect terms proportional to O($\nabla$h)$^2$ and O($\nabla$$^2$h). (omitted)

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2000년도 춘계학술대회논문집
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• pp.75-81
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• 2000

Water waves propagate over irregular bottom bathymetry are transformed by refraction, diffraction, shoaling, reflection etc. Principal factor of wave transform is bottom bathymetry, but in case of current field, current is another important factor which effect wave transformation. The governing equation of this study is develop as wave-current equation type to investigate the effect of wave-current interaction. This wave-current model was applied to the Kwangan beach which is located at Pusan. The numerical simulation results of this model show the characteristics of wave transformation and flow pattern around the Kwangan beach fairly well.

• Journal of Mechanical Science and Technology
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• 제18권6호
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• pp.1036-1041
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• 2004

A newly designed pressure-scanning slit viscometer is developed to combine an optical device without refraction while measuring blood viscosity over a range of shear rates. The capillary tube in a previously designed capillary viscometer was replaced with a transparent slit, which is affordable to mount optical measurement of flowing blood cells. Using a pressure transducer, we measured the change of pressure in a collecting chamber with respect to the time, p(t), from which the viscosity and shear rate were mathematically calculated. For water, standard oil and whole blood, excellent agreement was found between the results from the pressure-scanning slit viscometer and those from a commercially available rotating viscometer. This new viscometer overcomes the drawbacks of the previously designed capillary viscometer in the measuring whole blood viscosity. First, the pressure-scanning slit viscometer can combine an optical instrument such as a microscope. Second, this design is low cost and simple (i.e., ease of operation, no moving parts, and disposable).