• Journal of information and communication convergence engineering
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• 제14권3호
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• pp.200-206
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• 2016

Images can be obtained by collecting rays from objects. The characteristics of electromagnetic wave propagation depend on the medium. In particular, in an underwater imaging system, the interface between air and water must be considered. Further, reflection and transmission coefficients can be found by using electromagnetic theory. Because of the fact that the values of these coefficients differ according to the media, the recorded light intensities will change. A color image sensor has three different color channels. Therefore, the reflection and transmission coefficients have to be calculated individually. Thereafter, by using these coefficients, we can compensate for the color information of underwater objects. In this paper, we present a method to compensate for the color information of underwater objects by using electromagnetic wave propagation theory. To prove our method, we conducted optical experiments and evaluated the quality of the compensated image by a metric known as mean square error.

• 한국가시화정보학회지
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• 제3권1호
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• pp.3-19
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• 2005

Novel optical techniques are presented for three-dimensional tracking of nanoparticles; Optical Serial Sectioning Microscopy (OSSM) and Ratiometric Total Internal Reflection Fluorescent Microscopy (R-TIRFM). OSSM measures optically diffracted particle images, the so-called Point Spread Function (PSF), and dotermines the defocusing or line-of-sight location of the imaged particle measured from the focal plane. The line-of-sight Brownian motion detection using the OSSM technique is proposed in lieu of the more cumbersome two-dimensional Brownian motion tracking on the imaging plane as a potentially more effective tool to nonintrusively map the temperature fields for nanoparticle suspension fluids. On the other hand, R-TIRFM is presented to experimentally examine the classic theory on the near-wall hindered Brownian diffusive motion. An evanescent wave field from the total internal reflection of a 488-nm bandwidth of an argon-ion laser is used to provide a thin illumination field of an order of a few hundred nanometers from the wall. The experimental results show good agreement with the lateral hindrance theory, but show discrepancies from the normal hindrance theory. It is conjectured that the discrepancies can be attributed to the additional hindering effects, including electrostatic and electro-osmotic interactions between the negatively charged tracer particles and the glass surface.

• 한국해양공학회지
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• 제19권2호
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• pp.34-39
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• 2005

All of the design criterion are not only formulated by an internal study, concerning the design of maritime structures, but also by the guarantee that internal design technology is essential, at least according to theoretical and experimental studies. Furthermore, the basic data, which is necessary for the development of a more stable design of breakwater structures, should be ensured, according to current research and analysis of damage created by water waves. According to the necessity to solve the problems that occur in the design and construction of ocean structures, until now, it is recognized that the hydraulic experiments are important. This paper provides the design of structures to decrease the energy created by waves. Suggestions to make contributions to the development of ocean/fisheries technology are also discussed. It is better to use S-type coastal structures/breakwaters than to use uniform type breakwaters, concerning stability, reflection, and overtopping.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.203-207
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• 2008

Prestack depth migration is used to image for complex geological structure such as faults, folds, and subsalt. In this case, it is widely used the surface reflection data as a input data. However, the surface reflection data have intrinsic problems to image the subsalt and the salt flank due to the complex wavefields and multiples which come from overburden. For overcoming the structural defect of the surface reflection data in the imaging, I used the virtual sources in terms of seismic interferometry to image the subsurface and suppress the multiples using the velocity model of the lower part of the virtual sources. The results of the prestack depth migration using virtual source gathers and velocity model below receivers are similar geological interfaces to the results from shot gathers of the conventional ocean bottom seismic survey. And especially artificial interfaces by multiples were suppressed without applying any other data processing to eliminate multiples. This study results by numerical modeling can make a valuable imaging tool when it is applied to satisfied field data for specific condition.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.377-381
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• 2006

A seismic survey for gas hydrate have performed over the East sea by the KIGAM since 1997. General indicator of gas hydrate in seismic data is commonly inferred from the BSR(Bottom Simulating Reflector) that occurred parallel to the sea floor, amplitude decrease at the top of the BSR, amplitude blanking at the bottom of the BSR, decrease of the interval velocity and the reflection phase reversal at the BSR. In this paper we had analyzed optimum parameters of the field data to detect the 9as hydrate. Shot delay correction is applied 95ms, spherical divergence correction is applied velocity library 3, bandpass filter is applied 25-30-115-120Hz deconvolution operator length is applied 60ms, lag is 6ms and accurate velocity analysis NMO correction, stack is performed. Geobit 2.11.0 developed by the KIGAM was used for all data processing. Processing results say that the BSR occurred parallel to the sea floor were shown at 3,150m/s of two way travel time from the sea floor through shot point 5,000-5,610, and identified the interval velocity decrease around BSR and the reflection phase reversal corresponding to the reflection at the sea floor.

• 센서학회지
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• 제31권4호
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• pp.255-259
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• 2022

In this study, we fabricated ZnS substrates with excellent transmittance in the mid-infrared region (3-5 ㎛) using hot pressing instead of conventional chemical vapor deposition (CVD). Diamond-like carbon (DLC) was coated on either one or both sides of the ZnS substrates to improve their mechanical properties and transmittance efficiency. To reduce the reflectance and further improve transmittance in the mid-infrared region, anti-reflection (AR) coating was designed for DLC/ZnS /AR and AR/ ZnS /AR structures. The coating structure, microstructure, and optical properties of the AR-coated ZnS substrates were subsequently investigated by employing energy dispersive X-ray spectroscopy, scanning electron microscopy, and Fourier-transform infrared (FTIR) spectroscopy. The FTIR spectroscopy results demonstrated that, in the mid-infrared region, the average transmittance of the samples with AR coating on one and both sides increased by approximately 18% and 27%, respectively. Thus, AR coating improved the transmittance of the ZnS substrates.

• 열처리공학회지
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• 제29권3호
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• pp.124-131
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• 2016

GaN and InN epilayers with nucleation layer (LT-buffer) were grown on (0001) sapphire substrates by radio-frequency plasma-assisted molecular beam epitaxy (RF-MBE). As-grown and annealed GaN and InN nucleation layers grown at various growth condition were observed by reflection high-energy electron diffraction (RHEED). When temperature of effusion cell for III source was very low, diffraction pattern with cubic symmetry was observed and zincblende nucleation layer was flattened easily by annealing. As cell temperature increased, LT-GaN and LT-InN showed typical diffraction pattern from wurtzite structure, and FWHM of (10-12) plane decreased remarkably which means much improved crystalline quality. Diffraction pattern was changed to be from streaky to spotty when plasma power was raised from 160 to 220 W because higher plasma power makes more nitrogen adatoms on the surface and suppressed surface mobility of III species. Therefore, though wurtzite nucleation layer was a little hard to be flattened compared to zincblende, higher cell temperature led to easier movement of III surface adatoms and resulted in better crystalline quality of GaN and InN epilayers.

• 신재생에너지
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• 제2권2호
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• pp.4-8
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• 2006

Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si AR layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layer were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The surface morphology of porous Si layers were investigated using SEM. The formation of a porous Si layer about $0.1{\mu}m$ thick on the textured silicon wafer result in an effective reflectance coefficient Reff lower than 5% in the wavelength region from 400 to 1000nm. Such a surface modification allows improving the Si solar cell characteristics.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.53-53
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• 2003

최근 높은 유전상수와 잔류 분극, 비선형 등의 다양한 유전적인 특성으로 인해 산화물 박막이 많은 관심을 가지고 연구되어지고 있다. 많은 산화물 박막중에서도 BaTiO3/SiTiO3 (BTO/STO) 인 공격자는 STO나 BTO 또는 (Ba$_{0.5}$ Sr$_{0.5}$)TiO$_3$ (BST)등의 고용체들과 비교했을 때 아주 뛰어난 유전적인 성질을 나타내고 있다. 특히 1000 $\AA$ 이하의 낮은 두께에서도 높은 유전상수와 비선형도를 가진다는 사실이 선행된 실험에서 밝혀졌는데 BTO와 STO를 각각 2 unit cell (8 $\AA$)로 고정 시킨 후 다층 박막으로 제작했을 때 가장 큰 유전 특성을 얻을 수 있었다. 이런 뛰어난 유전적인 성질은 BTO와 STO 각 층의 두께와 주기 변화에 따른 박막 내부의 인위적인 stress와 그에 따른 격자 변형과 아주 밀접한 관계가 있음으로 생각되어진다. 따라서 이런 두 계면에서의 stress와 격자 변형을 더욱 정착하게 분석하기 위해서는 각 층을 원자 단위로 정확하게 두께 제어를 하고 증착되어지는 과정중에서의 growth mode를 확인하는 것이 무엇보다 중요한 일이다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.493-496
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• 2007

Korean Institute of Geosciences and Mineral Resources (KIGAM) has studied on gas hydrate in the Ulleung Basin, East sea of Korea since 1997. Most of all, a evidence for existence of gas hydrate, possible new energy resources, in seismic reflection data is bottom simulating reflection (BSR) which parallel to the sea bottom. Here we conducted the conventional data processing for gas hydrate data and Kirchhoff prestack depth migration. Kirchhoff migration is widely used for pre- and post-stack migration might be helpful to better image as well as to get the geological information. The processed stack image by GEOBIT showed some geological structures such as faults and shallow gas hydrate seeping area indicated by strong BSR. The BSR in the stack image showed at TWT 3.07s between shot gather No 3940 to No 4120. The estimated gas seeping area occurred at the shot point No 4187 to No 4203 and it seems to have some minor faults at shot point No 3735, 3791, 3947 and 4120. According to the result of depth migration, the BSR showed as 2.3km below the sea bottom.