• Journal of Wetlands Research
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• v.16 no.4
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• pp.353-362
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• 2014

The purpose of this study is to investigate the effect of micro-topography to vegetation pattern in Dunchon-dong wetland. To characterize the effect of micro-topography, changes in water level and vegetation pattern were monitored from 2007 to 2008. Depending on the relative elevation, the study site was divided into 4 sectors. The relative areas of sectors in ascending order were 11%, 10%, 18% and 24%, respectively. During investigation period, average water pH was 6.10 (${\pm}0.13$), electron conductivity was $51.5({\pm}6.0){\mu}s/cm$, $PO_4$-P, $NO_3$-N and $NH_4$-N concentration were $0.04({\pm}0.02)mg/L$, $0.14({\pm}0.07)mg/L$, and lower than 0.01mg/L, respectively. Water level was very changeable in low-water season because the area of lowest sector was small. This characteristic increased the effect of difference of accumulated precipitation from March to April in 2007 and 2008 to plant community composition in lower sectors. Different plant guilds dominated respective sectors and annual plants were major dominant species in the study site. This study suggested that the elevation gradients are necessary to create the habitats for various plant guilds in wetland.

• Journal of the Mineralogical Society of Korea
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• v.5 no.1
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• pp.22-31
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• 1992

The Sancheong kaolin was fractionated into 9 size fractions by wet sieving, sedimentation, and centrifugation. The systematic X-ray diffraction combined with electron microscopy shows that the clay mineral composition of each size fraction is related to the original fabric of kaolin. Minerals such as halloysite (10${\AA}$), kaolinite, illite, and goethite which were formed by procipitation from solution are generally concentrated in the finer fractions, whereas verniculite which was formed by pseudomorphic transformation from other primary minerals are concentrated in the coarser factions. Kaolinits of various types which were formed by precipitation or transformation show a wide size range but they are generally concentrated in the coarser fractions. Halloysite or halloysite-kaolinite clusters in coarse fractions are the fragmentation products of the walls of original boxwork clusters in coarse fractions are the fragmentation products of the walls of original boxwork kaolin which escaped the complete dispersion even through the grinding, ultrasonic agitation, and chemical treatment. Separation of fully hydrated halloysite and kaolinite was possible by systematic wet size fractionation. The coarse-grained minerals such as vermiculite and kaolinite are usually removed during the preparation of clay fraction smaller than 2${\mu}m$, whereas the fine-grained minerals such as illite and goethite are overlooked in X-ray diffraction of the bulk samples because of their minor contents. The systematic wet size fractionation is needed for understanding of the exact mineralogy of kaolin of weathering origin.

• Korean Journal of Materials Research
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• v.13 no.6
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• pp.347-351
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• 2003

II-Ⅵ ZnO compound semiconductor thin films were grown on $\alpha$-Al$_2$O$_3$(0001) single crystal substrate by radical beam assisted molecular beam epitaxy and the optical properties were investigated. Zn(6N) was evaporated using Knudsen cell and O radical was assisted at the partial pressure of 1$\times$10$^{4}$ Torr and radical beam source of 250-450 W RF power. In $\theta$-2$\theta$ x-ray diffraction analysis, ZnO thin film with 500 nm thickness showed only ZnO(0002)and ZnO(0004) peaks is believed to be well grown along c-axis orientation. Photoluminescence (PL) measurement using He-Cd ($\lambda$=325 nm) laser is obtained in the temperature range of 9 K-300 K. At 9 K and 300 K, only near band edge (NBE) is observed and the FWHM's of PL peak of the ZnO deposited at 450 RF power are 45 meV and 145 meV respectively. From no observation of any weak deep level peak even at room temperature PL, the ZnO grains are regarded to contain very low defect density and impurity to cause the deep-level defects. The peak position of free exciton showed slightly red-shift as temperature was increased, and from this result the binding energy of free exciton can be experimentally determined as much as $58\pm$0.5 meV, which is very closed to that of ZnO bulk. By van der Pauw 4-point probe measurement, the grown ZnO is proved to be n-type with the electron concentration($n_{e}$ ) $1.69$\times$10^{18}$$cm^3$, mobility($\mu$) $-12.3\textrm{cm}^2$/Vㆍs, and resistivity($\rho$) 0.30 $\Omega$$\cdot$cm.

• Korean Journal of Food Science and Technology
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• v.20 no.4
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• pp.504-510
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• 1988

The physicochemical properties of rice flours which were obtained by dry milling(blade, hammer, test and micro mill) and wet & dry milling (roller & micro mill) were investigated. The resulting flour particle sizes were reduced in the order that of blade, hammer, test, micro and roller & micro mill. Scanning electron microscopic examination showed that the starch granules were freed from the imbedding matrix as the particles became finer. The test-milled flour had the hightest levels of starch damage, maltose value and hot-water soluble amylose content, and the blade-milled flour showed the lowest levels. Amylograph viscosity and gelatinization temperature of the flours decreased as the particles became finer, and the addition of $Hg^{+2}$ increased the peak viscosity of the dry-milled flour pastes, whereas the wet & dry-milled flour did not show any changes. The blue values and ${\lambda}$max values of the iodine complex of the cold-water extractable ${\alpha}-D-glucan$ from flours were in the range of 0.023-0.029 and 518-522nm, respectively, indicating these materials were shown to be mainly composed of amylopectin-like polymer.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.582-590
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• 1987

Plasteins were synthesized from a peptic filefish protein hydrolysate by papain, $\alpha-chymotrypsin$ and protease(from Streptomyces griceus) under the optimum conditions of previous paper. L-glutamic acid diethylester and L-leucine ethylester were incorporated into plastein during the plastein reaction by papain. The structural changes of freeze-dried filefish meat, peptic hydrolysate, FPC and plasteins were observed by Scanning Electron Microscopy(SEM). The functional properties of plasteins also were measured. The solubility of plasteins was higher than that of FPC and the Glu-plastein had $95\%$ solubility in the range of pH 3-10. The dispersibility of Glu-plastein and protease plastein was similar to that of egg albumin, but those of the other plasteins were lower. The water holding capacity of plasteins was lower than that of egg albumin and C. Lipid absorption of Leu-plastein was tile highest, holding 1.80 ml/g, and that of the other plasteins was similar to that of egg albumin. The emulsifying activity of Leu-plastein was the highest, holding $61.2\%$, and that of Glu-plastein was the lowest, holding $50.7\%$. The emulsifying stability of plasteins was similar to that of the emulsifying activity. The emulsifying capacity of Leu-plastein was 384 ml/g(the highest), but that of Glu-plastein and $\alpha-chymotrypsin$ plastein was 248 ml/g(the lowest). The Leu-plastein shelved the highest foaming capacity, $373\%$. The foaming capacity of other plasteins was higher than that of egg albumin. The foaming stability of plasteins was superior to that of egg albumin. The viscosity of plasteins was lower than that of egg albumin. The microstructure of $\alpha-chymotrypsin$ plastein by SEM wassimilar to that of papain plastein, but other plasteins showed differences in their microstructure. The microstructure of Glu-plastein had a smooth shape.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.1
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• pp.76-79
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• 2016

This paper describes the successful development and the performance of X-band 50 W pulsed power amplifier using a 50 W GaN-on-SiC high electron mobility transistor. The GaN HEMT with a gate length of $0.25{\mu}m$ and a total gate width of 12 mm were fabricated. The X-band pulsed power amplifier exhibited an output power of 50 W with a power gain of 6 dB in a frequency range of 9.2~9.5 GHz. It also shows a maximum output power density of 4.16 W/mm. This 50 W GaN HEMT and X-band 50 W pulsed power amplifier are suitable for the radar systems and related applications in X-band.

• Korean journal of applied entomology
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• v.23 no.1 s.58
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• pp.15-21
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• 1984

The virus infecting French bean (Phaseolus vulgaris L.) was identified as Bean Common Mosaic Virus(BCMV) based on the host range, symptomatology, serology, morphology of virus particles and inclusion bodies. Isolates of BCMV were obtained from seeds of P. vulgaris collected at Suweon, Jangsu and Jinju in Korea. French bean produced vein clearing, mosaic, stunting and leaf curling. Symptom of Chenopodium quinoa was local lesions on the inoculated leaves, not on the upper leaves. The electron micrograph of the virus from French bean was flexuous approximately 750nm in length. Cylindrical and pinwheel cytoplasmic inclusion bodies were observed in French bean leaf infected by BCMV. BCMV from the French bean was transmitted through seed and green peach aphid, Myzus persicae. The thermal inactivation point was $55\~60^{\circ}C$, dilution end point was $10^{-3}\~10^{-5}$ and longevity in vitro was $2\~3$ days for BCMV from French bean. The isolates of BCMV reacted positively against BCMV antiserum. The extract of BCMV infected bean leaves, Azukibean mosaic virus (AZMV) and Cowpea aphid borne mosaic virus(CaMV) also reacted with BCMV antiserum, however, BCMV and CaMV showed the spur in agar gel diffusion test.

• Applied Microscopy
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• v.34 no.1
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• pp.61-69
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• 2004

The microwave dielectric properties and microstructures of the Complex Perovskite (1-x)$(Li_{1/2}Sm_{1/2})TiO_3-x (Na_{1/2}Sm_{1/2})TiO_3$(LNST) system were investigated using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). LNST had not only the antiphase tilting of oxygen octahedron but also the inphase tilting of oxygen octahedron and the antiparallel shift of cations. Also, when $0.0{\leq}x{\leq}0.4$, LNST had the vacancy ordering of A-sites because of the evaporation of Li ions. From the observation of the microstructure, abnormal grain growth phenomena were observed over the whole range of x. The temperature coefficient of resonant frequency ($T_{cf}$) of the $({Li_{1/2}}^{+1}{Sm_{1/2}}^{+3})TiO_3$(LST) system has a large negative value ($-220ppm/^{\circ}C$) but the $({Na_{1/2}}^{+1}{Sm_{1/2}}^{+3})TiO_3$(NST) system which substituted $Na^{+1}$ has a large positive value ($+173ppm/^{\circ}C$). The dielectric properties of ${\varepsilon}_r=103,\;Q*f_{0}=3,700GHz$ and $T_{cf}=+50ppm/^{\circ}C$ at 4GHz were obtained when x =0.4.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.81-84
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• 2005

The origin for the charge disproportionation (CD) transition in polycrystalline $La_{1/3}Sr_{2/3}FeO_{2.96}$ was examined using X-ray diffraction and the external field $M\ddot{o}ssbauer$ssbauer spectroscopy. In order to see how the external magnetic field affects the CD state above its transition temperature, an external magnetic field of up to 6 T was applied either parallel or perpendicular to the $\gamma-ray$ direction with the sample temperature fixed at 225 K, which was above the CD transition temperature. Without an external magnetic field, a completely paramagnetic singlet was obtained in the temperature range of the averaged valence state above the transition temperature, which was interpreted as coming from the average valence $Fe^{3.6+}$. In the longitudinal geometry, a magnetic Zeeman with its intensity ratio 3:0:1:1:0:3 is superimposed to the central singlet. In the transverse geometry, however, the central singlet disappears and only a magnetic component with its intensity ratio 3:4:1:1:4:3 emerges. The existence of a singlet is understood as an evidence of the fast electron-transfer among Fe ions. Since the singlet still exists under the magnetic field, the application of an external field has little effect on the conduction mechanism of hopping electrons.

• Journal of the Korean Magnetics Society
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• v.19 no.6
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• pp.209-215
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• 2009

M-type barium ferrite (BaFe12O19) powders were synthesized through the co-precipitation method. Starting material composition $Fe^{3+}:\;Ba^{2+}$ mole ratio was fixed as 8 and the relative amount of $Fe^{3+}$ and $Ba^{2+}$ was controlled. Structure and magnetic properties and powder morphology were investigated using XRD, SEM, VSM. Powder showing high coercivity and small magnetization was obtained at pH8 and $Fe_{3+}:\;Ba_{2+}$ of 12 : 1.5. Small magnetization value was originated from the existence of ${\alpha}-Fe_2O_3$. Single-phase Mtype barium ferrite were obtained regardless of the heat treatment condition and the amount of $Fe_{3+}\;and\;Ba_{2+}$ at pH$\approx$10. The largest value of magnetization (55.7 emu/g) under investigation were obtained when $Fe_{3+}:\;Ba_{2+}$ of 13.6 : 1.7 and furnace cooled powder in $O_2$. Particle size of powder was in the range of 50~200 nm.