• Journal of the Korean Society for Nondestructive Testing
• /
• v.22 no.2
• /
• pp.193-197
• /
• 2002

The frequency dependency of the Rayleigh surface wave was investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in the abrasion specimens, which was explained in view of the residual stress distribution. The peak intensity of the backward radiation profile decreased and the right half width of the profile increased with an increase of the variational rate of residual stress for the scuffing specimen. The peak intensity was also affected by the surface wave scattering during the propagation around the micro-damages. The peak angle might depend on not only the amount of residual stress but also the micro-structure. The result observed in this study demonstrates the high potential of the backward radiated ultrasound as a tool for the nondestructive evaluation of the subsurface gradients of materials.

• Proceedings of the International Microelectronics And Packaging Society Conference
• /
• 2003.11a
• /
• pp.174-176
• /
• 2003

유기첨가제 첨가법을 통해 개발된 저조도 전해동박을 전자파 차폐용 필터로 적용하기 위해서는 시인성을 확보하기 위한 흑화표면처리가 요구된다. 이를 위해 검토된 흑화표면처리 방법 중 흑화도, 전도성, 치수안정성 공정성에 있어서 전기도금법이 가장 우수한 것으로 나타났다. 개발된 흑화도금액계는 흑색도금조직을 $0,2{\mu}m$이하로 미세하게 노듈화시킴으로 인해 외부 빛을 산란시켜 광택을 줄이고 흑화도를 증가시켰으며 전착된 흑화도금층의 묻어남을 최소화할 수 있는 조성으로 구성되었다.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2001.10a
• /
• pp.367-368
• /
• 2001

해조류 자원은 해양의 1차 생산자로서 어, 패류의 먹이원이 되고 산란장이나 생활공간을 마련해 주게 됨으로 연안생물자원의 생산성을 높일 수 있다. 그러나 근래 갯녹음 현상으로 암초지대에 서식하는 해조숲이 줄어들고 바다가 황폐화되고 있다. 연안어장에 여러 종류의 바다생물이 서식하고 적극적인 자원조성을 하려면 우선 해조밭을 만들어 주어야 한다. 이 연구에서는 해조인공암초에 어떤 표면처리 조건이 바다숲 조성의 효율성을 높이는 것이 될 수 있는가를 검토하고자 하였다. (중략)

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.111.2-111.2
• /
• 2016

주사전자현미경은 시료표면에 전자빔을 주사하여 시료와 전자빔간의 상호작용으로 발생하는 이차전자(SE)와 후방산란전자(BSE)를 이용하여 시료표면을 관찰하는 장비이다. 일반적으로 텅스텐필라멘트를 사용하며, 10E-5 mbar이하 압력의 고진공에서 시료관찰이 이루어진다. 고진공 시료관찰시 도체 시료는 표면 코팅 없이 관찰이 가능하지만, 부도체 시료의 경우 전자빔에 의한 대전(Charging)현상이 발생하여 이미지가 왜곡되며, 이를 방지하기 위해 금, 백금 등의 금속을 표면에 코팅하여야 한다. 하지만 10E-1 mbar 이상 압력의 저진공에서는 부도체 시료도 전자빔에 의한 대전(Charging)현상이 발생하지 않아 생물시료 등의 부도체 시료를 표면코팅 없이 관찰할 수 있다. 본 발표에서는 현재 개발 중인 CeB6 필라멘트를 탑재한 저진공 주사전자현미경의 차동배기구조를 보여준다. 차동배기에 의해 가동 압력 10E-1 mbar이상의 저진공을 유지하는 시료실과 CeB6 필라멘트를 사용하기 위한 10E-6 mbar이하의 고진공을 유지하는 전자총실의 진공 배기특성을 보고한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.989-992
• /
• 2004

PEMBE(plasma enhanced molecular beam epitaxy)방법으로 성장된 GaN 박막의 초기 거동현상을 실시간 X-선 산란을 이용하여 관찰하였다. 표면이 원자 계단(atomic step)을 이루고 있는 사파이어 기판 위에 성장하는 GaN 박막은 layer-by-layer 모드로 성장 후 3D 모드로 성장을 하였다. 거친 표면을 가진 사파이어 기판 위에 성장하는 GaN 박막은 성장 초기는 표면을 평평하게 만든 후, 3D 모드로 성장하였다. 플라즈마로 생성된 이온화된 질소는 표면의 에너지를 변화시켜 GaN 박막의 증착을 증진시키고, 표면의 coverage를 증가시킨다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.8 no.3
• /
• pp.273-288
• /
• 1997

In this work, the electromagnetic waves scattered from 2-dimensional random rough surfaces are characterized by the $4\times4$ Mueller matrix elements. The full wave solutions are used to compute these elements. The results of the full wave solutions for 1-dimensional random rough surfaces were shown to agree well with those of the experiment and the method of moments. The Mueller matrix elements are related to the like and cross polarized radar cross sections as well as to the relative phase of the vertically and horizontally polarized waves. The $4\times4$ Mueller matrix elements completely characterize electromagnetic scattering from target. The computed results of this paper can be useful to the field of active remote sensing or RCS.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.5
• /
• pp.763-772
• /
• 2000

The Radiative Transfer Model(RTM) for computation of microwave polarimetric backscattering coefficients of a various types of vegitation canopies has been examined in this paper. Leaves in the vegitation canopy are modeled by rectangular resistive sheets, which sizes and orientations are randomly distributed. Surface roughness and soil moisture of soil surface are considered in this computation. The backscattering coefficients of grasslands are computed for various values of radar parameters and canopy parameters. A polarimetric scatterometer radar system at 15 GHz has been used for measurement of the scattering coefficient from a grass canopy and a cabbage canopy. The computation results obtained by the RTM for the canopies are compared with the measurement for examination of the RTM.

• Korean Journal of Remote Sensing
• /
• v.26 no.5
• /
• pp.497-510
• /
• 2010

In this study, comparisons of the backscattering coefficients and the coherence values which had been extracted from SAR (Synthetic Aperture Radar) images such as JERS-1, ENVISAT and ALOS satellites with surface roughness, surface geometric and soil moisture content were carried out. As the results of analysis using the backscattering coefficient and coherence values from SAR images, the coherence was shown high in the region containing more of mud fraction due to higher viscosity of fine grain-size. A lot of tidal channels were well developed in the Ganghwa tidal flat, affecting the drainage of seawater and subsequent soil moisture content by exposure time of tidal flat. The backscattering coefficient. consequently, appeared to be lower in sand flat and mix flat with decrease of soil moisture. In contrast, most mud flats were distributed at high elevation so that soil moisture was not much influenced by seawater. The backscattering coefficient in mud flat seemed to have a relationship with the density of tidal channel. In addition, lowering backscattering coefficients in the all Ganghwa tidal flat was observed when surface remnant water increased according to the amount of rainfall. The correlation between backscattering coefficient, coherence and sediment environment factors in the Ganghwa tidal flat was investigated. In the future, more quantitative spatial analysis will be helpful to well understand the sedimentary influence of various sediment environment factors.

• Korean journal of applied entomology
• /
• v.51 no.3
• /
• pp.235-243
• /
• 2012

Population dynamics of the American serpentine leafminer, Liriomyza trifolii (Burgess), were observed and modeled in order to compare the effects of air and tomato leaf temperatures inside a greenhouse using DYMEX model builder and simulator (pre-programed module based simulation programs developed by CSIRO, Australia). The DYMEX model simulator consisted of a series of modules with the parameters of temperature dependent development and oviposition models of L. trifolii were incorporated from pre-published data. Leaf surface temperatures of cherry tomato leaves (cv. 'Koko') were monitored according to three tomato plant positions (top, > 1.8 m above the ground level; middle, 0.9 - 1.2 m; bottom, 0.3 - 0.5 m) using an infrared temperature gun. Air temperature was monitored at the same three positions using a self-contained temperature logger. Data sets for the observed air temperature and average leaf surface temperatures were collected (top and bottom surfaces), and incorporated into the DYMEX simulator in order to compare the effects of air and leaf surface temperature on the population dynamics of L. trifolii. The initial population consisted of 50 eggs, which were laid by five female L. trifolii in early June. The number of L. trifolii larvae was counted by visual inspection of the tomato plants in order to verify the performance of DYMEX simulation. The egg, pupa, and adult stage of L. trifolii could not be counted due to its infeasible of visual inspection. A significant positive correlation between the observed and the predicted numbers of larvae was found when the leaf surface temperatures were incorporated into the DYMEX simulation (r = 0.97, p < 0.01), but no significant positive correlation was observed with air temperatures(r = 0.40, p = 0.18). This study demonstrated that the population dynamics of L. trifolii was affected greatly by the leaf temperatures, though to little discernible degree by the air temperatures, and thus the leaf surface temperature should be for a consideration in the management of L. trifolii within cherry tomato greenhouses.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.5
• /
• pp.463-470
• /
• 2016

In this paper, we introduce a method of scattering centers extraction using the polarimetric data. VIRAF software based on the PO (Physical Optics) and PTD(Physical Theory of Diffraction) were used to calculate the surface scattering and the edge or wedge scattering, respectively. In addition, by using the unitary transformation, 4-channel data based on the linear polarization basis were converted to 2-channel data based on the left/vertical-circular polarization basis, leading to data compression coherently. The scattering mechanism was analyzed in terms of the polarization states and different look angles by using the scattering center of a target extracted by the 2D RELAX algorithm.