• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.04b
• /
• pp.56-59
• /
• 2004

The stochiometric composition of $AgGaS_2$ polycrystal source materials for the $AgGaS_2/GaAs$ epilayer was prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns it was found that the polycrystal $AgGaS_2$ has tetragonal structure of which lattice constant $a_0$ and $c_0$ were 5.756 ${\AA}$ and 10.305 ${\AA}$, respectively. $AgGaS_2/GaAs$ epilayer was deposited on throughly etched GaAs (100) substrate from mixed crystal $AgGaS_2$ by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $590^{\circ}C$ and $440^{\circ}C$ respectively. The crystallinity of the grown $AgGaS_2/GaAs$ epilayer was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for $AgGaS_2/GaAs$ epilayer at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by ${\alpha}=8.695{\times}10^{-4}eV/K$, and $\beta$=332 K. From the photocurrent spectra by illumination of polarized light of the $AgGaS_2/GaAs$ epilayer, we have found that crystal field splitting $\Delta$ Cr was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pairs are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

• Progress in Superconductivity
• /
• v.3 no.2
• /
• pp.135-139
• /
• 2002

We have fabricated high-quality c-axis-oriented $MgB_2$ thin films by using a pulsed laser deposition technique. The thin films grown on (1 1 0 2) $Al_2$$O_3$ substrates show an onset transition temperature of 39.2 K with a sharp transition width of ~0.15 K. X-ray diffraction patterns indicate a c-axis-oriented crystal structure perpendicular to the substrate surface. We observed high critical current densities ($J_{c}$) of ~ 16 $MA/\textrm{cm}^2$ at 15 K and under self-field, which is comparable to or exceeds those of cuprate high-temperature superconductors. The extrapolation $J_{c}$ at 5 K was estimated to be ~ 40 MA/$\textrm{cm}^2$, which is the highest record for $MgB_2$ compounds. At a magnetic field of 5 T, the $J_{c}$ of~ 0.1 $MA/\textrm{cm}^2$ was detected at 15 K, suggesting that this compound is very promising candidate for the practical applications at high temperature with lower power consumption. As a possible explanation for the high current-carving capability, the vortex-glass phase will be discussed.d.d.d.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2016.05a
• /
• pp.330-330
• /
• 2016

The quantification of dry season evaporation in regions, where the magnitude of dry season flows is key to the regional water supply, is essential for good water management. Also, tree transpiration has a significant role in the water balance of a catchment whenever it is tree populated, especially in water limited environments. Such is the case in the Middle Mountains of Nepal where dry season flows play a significant role in downstream water provisioning and their proper functioning is key to the welfare of millions of people. This research seeks to study the transpiration of a pine forest stand in the Jikhu Khola Watershed in the Middle Mountains of Nepal. To the author's knowledge, no single study has been made so far to estimate the dry season evaporation from the planted forest stand in the Middle Mountains of Nepal. The study was carried out in planted pine forest embedded within the Jikhu Khola Catchment. Field campaigns of sap flow measurements were carried out from September, 2010 to February, 2011 in the selected plot of 15*15m dimension, to characterize dry season evaporation. This was done by measuring sap fluxes and sapwood areas over the six trees of different Diameter at Breast Height (DBH) classes. The sap flux was assessed using Granier's thermal dissipation probe (TDP) technique while sapwood area was determined using several incremental core(s) taken with a Pressler borer and immediately dyeing with methyl orange for estimating the actual depth of sapwood area. Transpiration of the plot was estimated by considering the contribution of each tree class. For this purpose, sap flux density, sapwood area and the proportion of total canopy area were determined for each tree class of the selected plot. From these data, hourly and diurnal transpiration rates for the plot were calculated for experimental period. Finally, Cienciala model was parameterized using the data recorded by the ADAS and other terrain data collected in the field. The calibrated model allowed the extrapolation of Sap flux density (v) over a six month period, from September 2010 to February 2011. The model given sap flux density was validated with the measured sap flux density from Grainier method.

• Publications of The Korean Astronomical Society
• /
• v.27 no.4
• /
• pp.347-352
• /
• 2012

Understanding infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and AGN evolution, since their most intense stages are often obscured by dust. Japanese infrared satellite, AKARI, provided unique data sets to probe this both at low and high redshifts. The AKARI performed an all sky survey in 6 IR bands (9, 18, 65, 90, 140, and $160{\mu}m$) with 3-10 times better sensitivity than IRAS, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can measure the total infrared luminosity ($L_{TIR}$) of individual galaxies much more precisely, and thus, the total infrared luminosity density of the local Universe. In the AKARI NEP deep field, we construct restframe $8{\mu}m$, $12{\mu}m$, and total infrared (TIR) luminosity functions (LFs) at 0.15 < z < 2.2 using 4,128 infrared sources. A continuous filter coverage in the mid-IR wavelength (2.4, 3.2, 4.1, 7, 9, 11, 15, 18, and $24{\mu}m$) by the AKARI satellite allows us to estimate restframe $8{\mu}m$ and $12{\mu}m$ luminosities without using a large extrapolation based on a SED fit, which was the largest uncertainty in previous work. By combining these two results, we reveal dust-hidden cosmic star formation history and AGN evolution from z = 0 to z = 2.2, all probed by the AKARI satellite.

• Progress in Medical Physics
• /
• v.28 no.4
• /
• pp.171-180
• /
• 2017

The purpose of this study is to install a system that compensated for the respiration motion using an articulated robotic manipulator couch which enables a wide range of motions that a Stewart platform cannot provide and to evaluate the performance of various prediction algorithms including proposed algorithm. For that purpose, we built a miniature couch tracking system comprising an articulated robotic manipulator, 3D optical tracking system, a phantom that mimicked respiratory motion, and control software. We performed simulations and experiments using respiratory data of 12 patients to investigate the feasibility of the system and various prediction algorithms, namely linear extrapolation (LE) and double exponential smoothing (ES2) with averaging methods. We confirmed that prediction algorithms worked well during simulation and experiment, with the ES2-averaging algorithm showing the best results. The simulation study showed 43% average and 49% maximum improvement ratios with the ES2-averaging algorithm, and the experimental study with the $QUASAR^{TM}$ phantom showed 51% average and 56% maximum improvement ratios with this algorithm. Our results suggest that the articulated robotic manipulator couch system with the ES2-averaging prediction algorithm can be widely used in the field of radiation therapy, providing a highly efficient and utilizable technology that can enhance the therapeutic effect and improve safety through a noninvasive approach.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.273-280
• /
• 2002

The stochiometric mix of evaporating materials for the CuGaTe$_2$ single crystal thin films was prepared from horizontal furnance. For extrapolation method of X-ray diffraction patterns for the CuGaTe$_2$ polycrystal, it was found tetragonal structure whose lattice constant a$\_$0/ and c$\_$0/ were 6.025 ${\AA}$ and 11.931 ${\AA}$, respectively. To obtain the single crystal thin films, CuGaTe$_2$ mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were 670 $^{\circ}C$ and 410 $^{\circ}C$ respective1y, and the thickness of the single crystal thin films is 2.1 $\mu\textrm{m}$. The crystalline structure of single crystalthin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of van der Pauw and studied on carrier density and mobility dependence on temperature. The carrier density and mobility of CuGaTe$_2$ single crystal thin films deduced from Hall data are 8.72${\times}$10$\^$23/㎥, 3.42${\times}$10$\^$-2/㎡/V$.$s at 293K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the CuGaTe$_2$ single crystal thin film, we have found that the values of spin orbit coupling Δs.o and the crystal field splitting Δcr were 0.0791 eV and 0/2463eV at 10K, respectively. From the PL spectra at 10K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be 0.0470eV and the dissipation energy of the donor -bound exciton and acceptor-bound exciton to be 0.0490eV, 0.00558eV, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.281-287
• /
• 2002

The stochiometric composition of AgGaS$_2$ polycrystal source materials for the AgGaS$_2$/GaAs epilayer was prepared from horizontal furnace. From the extrapolation method of X-ray diffraction patterns it was found that the polycrystal AgGaS$_2$ has tetragonal structure of which lattice constant a$\sub$0/ and c$\sub$0/ were 5.756 ${\AA}$ and 10.305 ${\AA}$, respectively. AgGaS$_2$/GaAs epilayer was deposited on throughly etched GaAs(100) substrate from mixed crystal AgGaS$_2$ by the Hot Wall Epitaxy (100) system. The source and substrate temperature were 590$^{\circ}C$ and 440$^{\circ}C$ respectively. The crystallinity of the grown AgGaS$_2$/GaAs epilayer was investigated by the DCRC (double crystal X-ray diffraction rocking curve). The optical energy gaps were found to be 2.61 eV for AgGaS$_2$/GaAs epilayer at room temperature. The temperature dependence of the photocurrent peak energy is well explained by the Varshni equation, then the constants in the Varshni equation are given by ${\alpha}$ : 8.695${\times}$10$\^$-4/ eV/K, and ${\beta}$ = 332 K. From the photocurrent spectra by illumination of polarized light of the AgGaS$_2$/GaAs epilayer, we have found that crystal field splitting ΔCr was 0.28 eV at 20 K. From the PL spectra at 20 K, the peaks corresponding to free and bound excitons and a broad emission band due to D-A pain are identified. The binding energy of the free excitons are determined to be 0.2676 eV and 0.2430 eV and the dissociation energy of the bound excitons to be 0.4695 eV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.230-233
• /
• 2004

The stochiometric mix of evaporating materials for the $CuInS_2$ single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuInS_2$ polycrystal, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.524\;{\AA}$ and $11.142\;{\AA}$, respectively. To obtain the single crystal thin films, $CuInS_2$ mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperature were 640 t and 430 t, respectively and the thickness of the single crystal thin films was $2{\mu}m$. Hall effect on this sample was measured by the method of van dot Pauw and studied on carrier density and temperature dependence of mobility. The carrier density and mobility deduced from Hall data are $9.64{\times}10^{22}/m^3,\;2.95{\times}10^{-2}\;m^2/V{\cdot}s$ at 293 K, respectively The optical energy gaps were found to be 1.53 eV at room temperature. From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the thin film, we have found that the values of spin orbit coupling splitting ${\Delta}So$ and the crystal field splitting ${\Delta}Cr$ were 0.0211 eV and 0.0045 eV at 10 K, respectively. From PL peaks measured at 10K, 807.7nm (1.5350ev) mean Ex peak of the free exciton emission, also 810.3nm (1.5301eV) expresses $I_2$ peak of donor-bound exciton emission and 815.6nm (1.5201eV) emerges $I_1$ peak of acceptor-bound exciton emission. In addition, the peak observed at 862.0nm (1.4383eV) was analyzed to be PL peak due to donor-acceptor pair(DAP).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.167-170
• /
• 2004

The stochiometric mix of evaporating materials for the $CuGaT_2$ single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuGaTe_2$ polycrystal, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were 6.025 ${\AA}$ and 11.931 ${\AA}$, respectively. To obtain the single crystal thin films, $CuGaTe_2$ mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $670^{\circ}C$ and $410^{\circ}C$ respectively, and the thickness of the single crystal thin films is $2.1{\mu}m$. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the $CuGaTe_2$ single crystal thin film, we have found that the values of spin orbit coupling ${\Delta}s.o$ and the crystal field splitting ${\Delta}cr$ were $0.079\underline{1}eV$ and $0.246\underline{3}eV$ at 10 K, respectively. From the PL spectra at 10K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be $0.047\underline{0}eV$ and the dissipation energy of the donor-bound exciton and acceptor-bound exciton to be $0.049\underline{0}eV$, $0.055\underline{8}eV$, respectively.

• Korean Journal of Ecology and Environment
• /
• v.52 no.2
• /
• pp.151-160
• /
• 2019

The study of spiders that function as predators in agroecosystem can broaden the understanding of agroecosystems. This study investigated the effect of heterogeneity at different spatial scales on richness and abundance of spiders in upland and paddy fields. We collected 48 samples using pitfall traps at upland and paddy fields, respectively. The total species richness of spiders estimated by sample- and coverage-based rarefaction and extrapolation curves. The total species richness was high in the upland fields at the total study sites, whereas the average species richness per study site was high in the paddy fields. We confirmed that the diversity enhancement of spiders was influenced by the structural complexity of habitat at field-scale, and crop diversity at broader scale.