• 한국세라믹학회지
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• 제53권2호
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• pp.253-257
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• 2016

We added 0 ~ 5 wt% $YBO_3:Eu^{3+}$ nano powders in a scattering layer of a working electrode to improve the energy conversion efficiency (ECE) of a dye sensitized solar cell (DSSC). FESEM and XRD were used to characterize the microstructure and phase. PL and micro Raman were used to determine the fluorescence and the composition of $YBO_3:Eu^{3+}$ phosphor. A solar simulator and a potentiostat were used to confirm the photovoltaic properties of the DSSC with $YBO_3:Eu^{3+}$. From the results of the microstructure and phase of the fabricated $YBO_3:Eu^{3+}$ nano powders, we identified $YBO_3:Eu^{3+}$ having particle size less than 100 nm. Based on the microstructure and micro Raman results, we confirmed the existence of $YBO_3:Eu^{3+}$ in the scattering layer and found that it was dispersed uniformly. Through photovoltaic properties results, the maximum ECE was shown to be 5.20%, which can be compared to the value of 5.00% without $YBO_3:Eu^{3+}$. As these results are derived from conversion of light in the UV range into visible light by employing $YBO_3:Eu^{3+}$ in the scattering layer, these indicate that the ECE of a DSSC can be enhanced by employing an appropriate amount of $YBO_3:Eu^{3+}$.

• 수산해양기술연구
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• 제30권4호
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• pp.251-262
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• 1994

The speed of vertical migration and the volume backscattering strength of the scattering layers during the evening and morning transitions between day and night were measured in November 1990-1992 in thermally stratified waters of the East China Sea. Acoustical measurements were carried out using a scientific echo-sounder operating at t재 frequencies of 25 and 100kHz, and using an echo-integration system connected with a micro-computer. Biological sampling was accomplished by bottom trawling to identify fish species recorded on the echo sounder, and the species and length compositions were determined. The values of scattering strength were allocated to group of fishes according to the fish traces on the echo recording paper and the species composition of trawl catches. The vertical velocities of migration derived from the changes in the depths and the values of peak scattering strength of the dense layer vertically migrating toward the bottom or toward the surface. The trawl data suggest that snailfish and fishing frog were the most abundant fishes in all research stations. As sunrise approached, the fish formed a strong concentration just above the thermocline. The the highest values of scattering strength in the entire water column appeared in the depth strata above the thermocline just before the begining of downward migration. As soon as the fish began to migrate downwards across the thermocline, the values of the scattering strength in the depth strata above the thermocline rapidly decreased, while the values for the scattering layer moving slowly toward the bottom gradually increased. During the 1992 surveys, the speed of the vertical migration was estimated to be 0.38m/min in the upward migration and 0.32m/min in the downward migration, respectively. That is the rate of vertical migration was slightly higher at dusk than at dawn. Similar migration patterns were observed on different stations and under different weather conditions during the surveys in 1990.

• 한국세라믹학회지
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• 제39권5호
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• pp.433-437
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• 2002

Impact-collision ion scattering spectroscopy was applied to study the geometrical structure of epitaxially grown TiO layers on the MgO(100) surface. Hetero-epitaxial TiO layer was formed by thermal evaporation of titanium onto the MgO(100) surface followed by the exposure to oxygen at $400{\circ}$. The well-ordered TiO structure was confirmed by the impact-collision ion scattering spectroscopy and reflection high energy electron diffraction patterns. It is revealed that the Ti and O atoms are located on the on-top site of the MgO(100) surface and the TiO overlayers are composed of little three dimensional islands.

• 한국표면공학회지
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• 제37권3호
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• pp.175-178
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• 2004

The size and number of nano-size defects of thin trivalent chrome layers were determined by small angle neutron scattering (SANS) without breaking the thin chrome layers. Most of defect size of the trivalent chromium prepared in this test conditions is in the range of about 40nm. The number of nano-size defects less than about 40nm of the trivalent chromium layer increases with plating voltage at constant current density From this study, SANS is proved as one of useful techniques to evaluate nano-size defects of thin film layer.

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 하계학술발표회 논문집
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• pp.187-188
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• 2007

Four kinds of mirror substrates with same surface roughness were fabricated. On those substrates, a dielectric multi-layer coating with high reflectivity was deposited by ion beam sputtering technique. Most of the fused silica mirrors showed lower scattering than the ZERODUR mirrors one, which deposited on substrates similar in surface roughness. The ZERODUR mirrors scattering strongly depend on the micro-structure of $Ta_2O_5/SiO_2$ thin films wear deposited on ZERODUR substrates.

• 대한원격탐사학회지
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• 제33권1호
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• pp.47-60
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• 2017

The permafrost active layer plays an important role in permafrost dynamics. Ecological patterns, processes, and water and ice contents in the active layer are spatially and temporally complex depending on landscape heterogeneity and local-scale variations in hydrological processes. Although there has been emerging interest in the application of optical remote sensing techniques to permafrost environments, optical sensors are significantly limited in accessing information on near surface geo-cryological conditions. The primary objective of this study was to investigate capability of L-band SAR data for monitoring spatio-temporal variability of permafrost ecosystems and underlying soil conditions. This study exploits information from different polarimetric SAR observables in relation to permafrost environmental conditions. Experimental results show that each polarimetric radar observable conveys different information on permafrost environments. In the case of the dual-pol mode, the radar observables consist of two backscattering powers and one correlation coefficient between polarimetric channels. Among them, the dual-pol scattering powers are highly sensitive to freeze/thaw transition and can discriminate grasslands or ponds in thermokarst area from other permafrost ecosystems. However, it is difficult to identify the ground conditions with dual-pol observables. Additional backscattering powers and correlation coefficients obtained from quad-pol mode help understanding seasonal variations ofradar scattering and assessing geo-cryological information on soil layers. In particular, co-pol coherences atHV-basis and circular-basis were found to be very usefultools for mapping and monitoring near surface soil properties.

• 대한전자공학회논문지
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• 제27권4호
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• pp.534-540
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• 1990

In this paper the characteristics of submicron gate GaAs MESFET's have been studied using a particle model which takes into account the hot-electron transport phenomena, i.e., the velocity overshoot. \ulcornervalley(<000> direction), L valley (<111>direction), X valley (<100>direction) as the GaAs conduction energy band and optical phonon, acoustic phonon, equivalent intervalley, nonequivalent intervalley scattering as the scattering models, have been considered in this simulation. And the GaAs material and the device simulation have been done by determination of the free flight time, scattering mechanism and scattering angle according to Monte-Carlo algorithm which makes use of a particle model. As a result of the particle simulation, firstly the electron distribution, the potential energy distribution and the situation of electron displacement in 0.6 \ulcorner gate length device have been obtained. Secondly, the cutoff frequency, obtained by this method, is k47GHz which is in good agreement with the calculated result of theory. And the current-voltage characteristics curve which takes account of the buffer layer effect has been obtained. Lastly it has been verified that parasitic current at the buffer layer can be analyzed using channel depth modulation.

• 공업화학
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• 제22권2호
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• pp.190-195
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• 2011

다중층을 형성하여 광자를 가두는 효과와 산란층의 효과를 보고, $TiCl_4$ 처리를 통해 전극에서의 전자의 재결합이 줄어드는 정도와 그에 따른 효과를 알아보기 위하여 여러 가지 방법으로 $TiO_2$ 전극을 형성하고, 가장 최적의 전극 조건을 알아보았다. 각 전극의 특성을 알기 위해서 I-V 곡선, UV-VIS 분광기, EIS, IPCE를 측정하였다. 그 결과, I-V 곡선을 통해 한 층 보다는 다중층이 효율이 더 높은 것을 확인할 수 있었고, 기판 표면과 전극표면에 $TiCl_4$ 처리를 함으로써 EIS분석을 통해 반응저항이 감소하여 효율이 증가함을 확인할 수 있었다. 여러 전극 조건 중 산란층을 지닌 전극이 기본 한 층을 사용한 전극의 효율보다 약 19% 정도 높아짐을 확인하였다. 이러한 효율의 증가는 장파장을 투과하는 빛이 산란층을 통과할 때 전자 이동 경로가 길어지게 되어 단락전류의 값을 증가시키기 때문이다. 이에 따라, $J_{SC}$는 약 10% 정도 증가하였으며, IPCE는 최대 피크에서 약 12%가 향상되는 특성을 보였다.

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.443-457
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• 2018

In this article, a comparative study has been made to investigate the scattering behaviour of three layered structure model on torsional surface wave. For such model intermediate layer is taken as fiber reinforced composite, resting over a dry sandy Gibson substratum and underlying by different anelastic media. We consider two distinct mediums for topmost layer. In the first case, topmost layer has been taken as fluid saturated homogeneous porous layer, while in the second case the fluid saturated porous layer has been replaced by a transversely isotropic layer. Simple form expression for the secular equation of torsional surface wave has been worked out in both the cases by executing specific boundary conditions, which comprises Whittaker's function and its derivative, for imminent result that have been elaborated asymptotically. Some special cases have been constituted which are in excellent compliance with recorded literatures. For the sake of comparative study, numerical estimation and graphical illustration have been accomplished to identify the effects of the width ratio of the layers, Biot's gravity parameter, sandy parameter, porosity parameter and other heterogeneity parameters corresponding to the layers and half spaces, horizontal compressive and tensile initial stress on the phase velocity of torsional surface wave.

• 대한원격탐사학회지
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• 제25권3호
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• pp.255-261
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• 2009

A new polarimetric SAR image classification technique based on the degree of polarization (DoP) and the co-polarized phase-difference (CPD) is presented in this paper. Since the DoP and the CPD of a scattered wave provide information on the randomness of the scattering and the type of scattering mechanisms, at first, the statistics of the DoP and CPD are examined with measured polarimetric SAR image data. Then, a DoP-CPD diagram with appropriate boundaries between six different classes is developed based on the SAR image. The classification technique is verified using the JPL AirSAR and ALOS PALSAR polarimetric data. The technique may have capability to classify an SAR image into six major classes; a bare surface, a village, a crown-layer short vegetation canopy, a trunk-layer short vegetation canopy, a crown-layer forest, and a trunk-dominated forest.