• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.230-233
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• 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
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• 2008.11a
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• pp.141-142
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• 2008

Single crystal $ZnIn_2S_4$ layers were grown on thoroughly etched semi-insulating GaAs(100) substrate at $450^{\circ}C$ with hot wall epitaxy (HWE) system by evaporating $ZnIn_2S_4$ source at $610^{\circ}C$. The temperature dependence of the energy band gap of the $ZnIn_2S_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T) = 2.9514eV - ($7.24\times10^{-4}$ eV/K)$T^2$/(T + 489 K). After the as-grown $ZnIn_2S_4$ single crystal thin films was annealed in Zn-, S-, and In-atmospheres, the origin of point defects of $ZnIn_2S_4$ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of $V_{Zn}$, $V_s$, $Zn_{int}$, and $S_{int}$, obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the S-atmosphere converted $ZnIn_2S_4$ single crystal thin films to an optical p-type. Also, we confirmed that In in $ZnIn_2S_4$/GaAs did not form the native defects because In in $ZnIn_2S_4$ single crystal thin films existed in the form of stable bonds.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.98-99
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• 2008

To obtain the single crystal thin films, $AgGaSe_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $420^{\circ}C$, respectively. The temperature dependence of the energy band gap of the $AgGaSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T) 1.9501 eV - ($8.79\times10^{-4}$ eV/K)$T^2$/(T + 250 K). After the as-grown $AgGaSe_2$ single crystal thin films was annealed in Ag-, Se-, and Ga-atmospheres, the origin of point defects of $AgGaSe_2$ single crystal thin films has been investigated by the photoluminescence(PL) at 10K. The native defects of $V_{Ag}$, $V_{Se}$, $Ag_{int}$, and $Se_{int}$ obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Ag-atmosphere converted $AgGaSe_2$ single crystal thin films to an optical p-type. Also, we confirmed that Ga in $AgGaSe_2$/GaAs did not form the native defects because Ga in $AgGaSe_2$ single crystal thin films existed in the form of stable bonds.

• Asian Journal of Turfgrass Science
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• v.11 no.1
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• pp.1-7
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• 1997

This study was performed to find out the mineral cycles of manganese and zinc in dynamic grassland ecosystems in a steady state condition at the northwest side on Mt. Kwanak. The experimental results may be summarized on the communities of a Zoysia japonica and a Miscanthus sincnsis as follows. As compared with some properties of the surface soils among two semi-natural grasslands, manganese and zinc was greater quantity in a Miscanthus sincnsis than in a Zoysia japonica on Mt. Kwana For the case of steady procluction and release, the ratio of annual mineral production to the amount accumulated on the top of mineral soil in a steady state provides the estimates of release constant k. The release constants of Mn and Zn of the litter were 0.19 and 0. 14 in the Zoysia japon- ica grassland, and were 0.44 and 0.41 in a Miscanthus sincnsis grassland, respectively. The halftimes of Mn and Zn required for the release or accumulation of the litter on the grassland were 3. 65 and 4.95 years in the Zoysia japonica, and were 1.57 and 1.69 years in the Miscanthus sincnsis, respectively. The amounts of annual cycles for Mn and Zn in the grassland ecosystem under the steady-state conditions were 58.60 and 21.46 mg /$m^2$ in a Zoysia japonica, and were 372.12 and 321.49 ing /m$^2$ in a Miscanthus sincnsis grassland. Key words: Zoysia japonica. Miscanthus sincnsis, Mt. Kwanak, Manganese, Zinc, Mineral cycles.

• Structural Engineering and Mechanics
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• v.45 no.5
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• pp.677-691
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• 2013

A semi-analytical finite strip method is developed for analyzing the post-buckling behavior of rectangular composite laminated plates of arbitrary lay-up subjected to progressive end-shortening in their plane and to normal pressure loading. In this method, all the displacements are postulated by the appropriate harmonic shape functions in the longitudinal direction and polynomial interpolation functions in the transverse direction. Thin or thick plates are assumed and correspondingly the Classical Plate Theory (CPT) or Higher Order Plate Theory (HOPT) is applied. The in-plane transverse deflection is allowed at the loaded ends of the plate, whilst the same deflection at the unloaded edges is either allowed to occur or completely restrained. Geometric non-linearity is introduced in the strain-displacement equations in the manner of the von-Karman assumptions. The formulations of the finite strip methods are based on the concept of the principle of the minimum potential energy. The Newton-Raphson method is used to solve the non-linear equilibrium equations. A number of applications involving isotropic plates, symmetric and unsymmetric cross-ply laminates are described to investigate the through-thickness shearing effects as well as the effect of pressure loading, end-shortening and boundary conditions. The study of the results has revealed that the response of the composite laminated plates is particularly influenced by the application of the Higher Order Plate Theory (HOPT) and normal pressure loading. In the relatively thick plates, the HOPT results have more accuracy than CPT.

• Ocean Systems Engineering
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• v.3 no.1
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• pp.35-53
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• 2013

In this study, a hybrid floating structure with cylinder was introduced to reduce the hydrodynamic motions of the pontoon type. The hybrid floating structure is composed of cylinders and semi-opened side sections to penetrate the wave impact energy. In order to exactly investigate the hydrodynamic motions and structural behavior of the hybrid floating structure under the wave loadings, integrated analysis of hydrodynamic and structural behavior were carried out on the hybrid floating structure. Firstly, the hydrodynamic analyses were performed on the hybrid and pontoon models. Then, the wave-induced hydrodynamic pressures resulting from hydrodynamic analysis were directly mapped to the structural analysis model. And, finally, the structural analyses were carried out on the hybrid and pontoon models. As a result of this study, it was learned that the hybrid model of this study was showed to have more favorable hydrodynamic motions than the pontoon model. The surge motion was indicated even smaller motion at all over wave periods from 4.0 to 10.0 sec, and the heave and pitch motions indicated smaller motions beyond its wave period of 6.5 sec. However, the hybrid model was shown more unfavorable structural behavior than the pontoon model. High concentrated stress occurred at the bottom slab of the bow and stern part where the cylinder wall was connected to the bottom slab. Also, the hybrid model behaved with the elastic body motion due to weak stiffness of floating body and caused a large stress variation at the pure slab section between the cylinder walls. Hence, in order to overcome these problems, some alternatives which could be easily obtained from the simple modification of structural details were proposed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.2
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• pp.145-154
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• 1990

Amounts of total suspended matter(TSM) around the Kori waters have been monitored for two years to understand the dispersal pattern of fine-grained sediment. Average concentration of the TSM is $3\~4\;mg/\iota$ in the surface and $3.5\~5\;mg/\iota$ in the near-bottom water. Semi-quantitative analysis for the four major clay minerals in TSM is also performed. The average relative abundance of each clay mineral such as illite, kaolinite, chlorite, and smectite is $65\%,\;17\%,\;17\%$, and $1\%$, respectively. It seems that the majority of recent fine-grained sediment deposited around the Kori area is derived from the Nakdong River. The texture of surface sediment is also dominated by fine-grained fraction leading up to $90\%$ of silt and clay content. The grain size decreases seaward progressively.

• Journal of the Korea Organic Resources Recycling Association
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• v.12 no.2
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• pp.52-60
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• 2004

The basic approach to sewage sludge is organic waste minimization, promotion of energy recovery; volume and weight reduction by final treatment, and environmentally final disposal of natural circulation. Dry and pyrolysis of maize was experimentally investigated in full-scale rotary kiln in semi-continuous operation. The operational parameters varied are the operating temperature $160{\sim}175^{\circ}C$ of dry and $450{\sim}800^{\circ}C$ of pyrolysis, the solids residence time 9 min for pyrolysis. Important parameters studied include the running time, water content of sewage sludge, solids amount of sewage sludge(TS%) by the varied temperature. Also, with the increasing of temperature, how the yield of oil and char product change was observed, and the distribution of gas production components was observed. The gas of $C_1{\sim}C_3$ yield increased and oil of $C_4{\sim}C_6$ yield decreased along with pyrolysis temperature of $670^{\circ}C$ by the run time of 9 min.

• Journal of Nutrition and Health
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• v.35 no.6
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• pp.650-657
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• 2002

In order to provide basic data for the means to improve food situation and nutritional status of those supported by the National Basic Livelihood Security System (NBLSS), we examined household food insecurity and nutritional status of children under the support of NBLSS. This study included 209 children aged 3-12 years (99 boys and 110 girls) and their caretakers. We measured house food insecurity using Radimer/cornell Scale, children's body sizes and nutrient intake by semi-quantitative food frequency questionnaire, and caretakers' nutritional management skills. Only 9.6％ of the households were in food secured (FS) while 8.1％ were in household food insecured, but without hunger (HFI), 42.1％ were in adult food insecured with hunger (AFI), and 40.2％ were in child hungry (CH). Important predictors of food security were nutritional management skills of the caretakers as well as their education, but neither income nor food expenditure of the households. Mean energy intake of the children was 86.0％ of the Korean Recommended Dietary Allowance (RDA). Intakes of protein, phosphorous, vitamin A and B$_1$ were relatively high ranging from 112.3％ to 124.4％ of the RDAs while those of calcium, iron, niacin, vitamin C were low showing 74.8-83.3％ of the RDAs. Height, weight and weight/height ratio were close to the reference levels. Lower nutrient intakes of children were observed as the households were more food insecured. However, nutrient intakes and body sizes of children did not differ as a function of household socioeconomic status representing by income, food expenditure and caretakers' education. Results of this study suggest the importance of food security and nutritional management skills for the children's nutrient intakes. Concerning this matter, a need for nutrition education in the program for NBLSS was discussed.

• Journal of Power Electronics
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• v.16 no.2
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• pp.464-472
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• 2016

This study applies the selective harmonic elimination (SHE) technique to design and operate a regulated AC/DC/AC power supply suitable for maritime military applications and underground trains. The input is a single 50/60 Hz AC voltage, and the output is a 400 Hz regulated voltage. The switching angles for a multi-level inverter and transformer turns ratio are determined to operate with special connected transformers with equal power ratings and produce an almost sinusoidal current. As a result of its capability of directly controlling harmonics, the SHE technique is applicable to apparatus with congenital immunity to specific harmonics, such as series-connected transformers, which are specially designed to equally share the total load power. In the present work, a single-phase 50/60 Hz input source is rectified via a semi-controlled bridge rectifier to control DC voltage levels and thereby regulate the output load voltage at a constant level. The DC-rectified voltage then supplies six single-phase quazi-square H-bridge inverters, each of which supplies the primary of a single-phase transformer. The secondaries of the six transformers are connected in series. Through off-line calculation, the switching angles of the six inverters and the turns ratios of the six transformers are designed to ensure equal power distribution for the transformers. The SHE technique is also employed to eliminate the higher-order harmonics of the output voltage. A digital implementation is carried out to determine the switching angles. Theoretical results are demonstrated, and a scaled-down experimental 600 VA prototype is built to verify the validity of the proposed system.