• Journal of the Korean Chemical Society
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• v.34 no.2
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• pp.203-210
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• 1990

As a possible biocompatible and biodegrable polymer skeleton for drug delivery system, block copolymers of L-lactic acid and L-glutamic acid with different composition were synthesized and characterized. Poly (L-lactide) was prepared by polymerization of L-lactide with zine oxide at $130^{\circ}C$ for 72 hrs. 3-Amino-l-propanol was introduced to poly (L-lactide) by an ester linkage in order to initiate polymerization. Polymerization of $\gamma-benzyl-L-glutamate-N-carboxyanhydride(\gamma-BLG-NCA)$ utiliizing the amino group of modified poly (L-lactide) as an initiator gave rise to the block copoly $(L-lactide-\gamma-benzyl-L-glutamate).$ The NMR study of resulting block copolymers showed that the composition of L-lactic acid and $\gamma-benzyl-L-glutamate$ in block copolymers was depended on the weight ratio of poly (L-lactide) and $\gamma-BLG-NCA.$ The thermal properties of the resulting block copolymers were determined by the differential scanning calorimetry and by the thermogravimetry.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.2
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• pp.46-58
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• 1991

The synthesized ZnO powder was prepared by spray pyrolysis method using ultrasonic vibrator. The starting solutons were the aqueous solution of $Zn(NO_3)_2\cdot6H_2O$. The concentration was prepared 1M, O.5M, O.25M, and O.lM. The Nz carrier gas was 2.3cm$\cdot{sec}^{-1}$. The prepared powder from the $Zn(NO_3)_2{\cdot}6H_2O$ aqueous solution was Zine oxide with hexagonal structure. The shape of prepared powder was fine size, narrow size distribution, agglomerate-free, nearly sphere particle. Also, the particle size was about $ 0.28-0.61\mum$.

• Korean Journal of Soil Science and Fertilizer
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• v.24 no.3
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• pp.183-191
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• 1991

A study was conducted to determine the influence of soil chemical properties on the distribution and forms of cadmium (Cd), lead (Pb), copper(Cu) and Zinc(Zn) in paddy soils near zinc mines. A sequential extraction procedure was used to fractionate the heavy metals in soils into the designated from of water soluble, exchangeable, organically bound, oxide/carbonate, and sulfide/residual. The predominant form of Cd, Pb, Cu and Zn in the soils was found to be sulfide/residual form. Oxide/carbonate Cd and Pb and organically bound Cu were high, while exchangeable Pb and Cu were very low. Water soluble Cd, Pb and Cu were not detected in the soils. The percentages of the heavy metals content in exchangeable fractions were inversely correlated with those in sulfide/residual fractions in the soils. Exchangeable Cd and Zn and the oxide/carbonate Pb were shifting to the sulfide/residual form with soil depth and the chemical forms of Cu were not changed. Organically bound Cu was positively correlated with soil organic matter content but Cd, Pb and Zn were not. The percentages of Cd, Pb and Zn content in exchangeable forms decreased with soil pH, while those in oxide/carbonate and sulfide/residual forms increased with soil pH. The amounts of oxide/carbonate and sulfide/residual forms of pb were higher than those of Cd and Zn at same soil pH.

• Journal of the Korean Magnetics Society
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• v.9 no.2
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• pp.78-84
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• 1999

$(Ni, Zn)Fe_2O_4$ powders were prepared through self-propagating high temperature synthesis reaction and the effects of initial zinc oxide powder size and oxygen pressure on the magnetic properties of the final combustion products were studied. The ferrite powders were combustion synthesized with iron, iron oxide, nickel oxide, and zinc oxide powders under various oxygen pressures of 0.5~10 atmosphere after blended in n-hexane solution for 5 minutes with a spex mill, followed by dried at 120 $^{\circ}C$ in vacuum for 24 hours. The maximum combustion temperature and propagating rate were about 1250 $^{\circ}C$ and 9.8 mm/sec under the tap density, which were decreased with decreasing ZnO size and oxygen pressure. The final product had porous microstructure with spinel peaks in X-ray spectra. As the ZnO particle size in the reactant powders and oxygen pressure during the combustion reaction increase, coercive force, maximum magnetization, residual magnetization, squareness ratio were changed from 1324 Oe, 43.88 emu/g, 1.27 emu/g, 0.00034 emu/gOe, 37.8$^{\circ}C$ to 11.83 Oe, 68.87 emu/g, 1.23 emu/g, 0.00280 emu/gOe, 43.9 $^{\circ}C$ and 7.99 Oe, 75.84 emu/g, 0.791 emu/g, 0.001937 emu/gOe, 53.8 $^{\circ}C$ respectively. Considering the apparent activation energy changes with oxygen pressure, the combustion reaction significantly depended on initial oxygen pressure and ZnO particle size.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.928-934
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• 2002

Gallium doped Zinc Oxide(GZO) films were deposited by dc magnetron sputtering using a GZO ceramic target at various conditions such as substrate temperature (RT, 400), residual water pressure ($P_{H_2O}$; 1.61${\times}10^{-4}∼2.2{\times}10^{-3}$ Pa), introduction of $H_2$ gas (8.5%) and different magnetic field strengths(250, 1000G). GZO films deposited without substrate heating showed clear degradation in film crystallinity and electrical properties with increasing $P_{H_2O}$. The resistivity increased from 3.0${\times}10^{-3}$ to 3.1${\times}10^{-2}{\Omega}㎝$ and the grain size of the films decreased from 24 to 3 nm when PH2O was increased from 1.61${\times}10^{-4}$ to 2.2${\times}10^{-3}$ Pa. However, degradation in electrical properties with increasing $P_{H_2O}$ was not observed for the films deposited with introduction of 8.5% $H_2$. When magnetic field strength of the cathode increased from 250G to 1000G, crystallinity and electrical properties of GZO films improved remarkably about all the $P_{H_2O}$. This result could be attributed to the decrease in film damage caused by the decrease in plasma impedance.

• Korean journal of applied entomology
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• v.33 no.4
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• pp.230-236
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• 1994

Dicofol susceptible two-spotted spider mite(S) which was selected by 150 times of dicofol treatment showed 27 5-fold increase in resistance as compared to S strain. Inheritance of resistance and crossresistance in selected strain($R_d$) were investigated. There were differences oi susceptibility in the dicofol concentmtion-moltaliity relationships between $F_1$ progenies (R♀, XS♂, R♂, XS♀) obtained from reciprocal cross with the S strain and $R_d$, strain. Degree of dominance of the $F_1$ progenies (R♀, XS♂, R♂, XS♀) were -0.29 and -0.72 in adult females and -0.42 and -0.93 in adult males, respectively. These results suggest that inheritance of dicofol resistance is controlled by an incomplete recessive. $R_d$ strain exhibited a high level of cross resistance to amitraz, and also showed cross resistance to pyrethrotd acaricides, acrinathrin and bifenthnn. $R_d$ strain showed non-cross reslstancz to abamectin, chlolfenson, clofentezine, cyhexatm, fenbutatin oxlde, fenpyroximate, hexythiazox, monocrotophos, propargite and tetradifon, but negatively correlated cross-resistance to azocyclotin and fenbutatin oxide belonging to tin acaricides.

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.47-50
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• 1986

Photodesorption of adsorbed $O_2^-$ on ZnO was investigated in ZnO-$O_2(N_2)$-rubrene-bromobenzene mixture. When the mixture was illuminated with the light having the energy greater than the band gap energy of ZnO (3.2eV), the amount of reacted rubrene increased as the amount of ZnO increased in the experimental condition. For the energy of light less than 3.2eV, however, the reacted amount of rubrene decreased as the amount of ZnO increased. There is a difference in the reacted amount of rubrene between ZnO-$O_2$-rubrene-bromobenzene and ZnO-$N_2$-rubrene-bromobenzene mixtures. From the results, it was suggested that the adsorbed $O_2^-$ on ZnO transform to singlet oxygen in the photodesorption process and the singlet oxygen reacted with rubrene.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.505-513
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• 1993

To make the electrophotographic photoreceptor that srnsirizes for panchromatic matcrial, the dying element of sunfasr yellow which has an absorption ivavclength at near 400nm, and $\alpha,\beta$-copper phthalocyaninc dying elements with 700nm absorption wavelength were adsorbed and then dispersed onto the zine oxide(Zn0). In ordcr to characterize rhe change In sensitivity the various binders and different mole ratio of ZnO to binder were employed in here. It was found rhat the optimum sensitivity was obtained with 5.5 ratio. I;rom the measurements of electrostatic and spectral sensitivity, it was found that the maximum photographic properties were obtained for mixing the sunfast yellow and $\beta$-copper phthalocyaninr. In this case the electrophotographic sensiri\ity was found to he $E{1:2}$= 1440 lux . sec. And also the spectral sensitivity shows that it had a good properties for panchromatic matcrial.

• Restorative Dentistry and Endodontics
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• v.3 no.1
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• pp.17-21
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• 1977

After a vital pulpotomy in dogs' teeth, the responses of the remaining pulp tissue under calcium hydroxide and formocresol were studied histologically. The class I and V cavities were prepared on the teeth and the pulp was amputated. Calcium hydroxide and formocresol were placed over the amputated tissue and the cavities were sealed with zine oxide eugenol cement and zinc phosphate cement. Animals. were sacrifice after 1, 2, and 3 weeks following the operation. The teeth were decalcfied, sectioned and stained with hematoxylin and eosin. Microscopic examination reveals as follows; 1. Healing of the pulp at the amputation site did not occur in the pulps treated with formocresol. 2. At one week, a thin layer of darker staining tissues just below the necrotic zone was presented in the pulps treated with formocresol. In this stage the tissues beneath the darker staining layer were normal. 3. At two weeks, the cells of the palest staining layer were showed indistinct nucleus which suggested the karyolysis and the karyorrhexis in the pulps treated with formocoresol. As reached to the middle third of the pulp, the odontoblasts were scarcely evident or missed in this stage. 4. At three weeks, the necrotic zone was reached to the middle third of the pulp canal. The cells beneath the zone showed massive infiltration of inflammatory cells in the pulps treated with formocresol. 5. Dentin bridge in the control group was deposited below the necrotic zone from the two. weeks later. 6. Normal tissues were observed ill the apical third of all. the dental pulps in all case of calcium hydroxide and formocresol.

• Journal of the Korean Vacuum Society
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• v.17 no.1
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• pp.40-45
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• 2008

We present the effect of Ga-doping on the electrical, structural and optical properties of ZnO layers with a thickness of ${\sim}500nm$ deposited on glass substrates. Polycrystalline ZnO and Ga-doped ZnO (GZO) layers were deposited by radio frequency (rf) magnetron sputtering at room temperature. Based on the X-ray diffraction (XRD) and transmission electron microscopy (TEM) data, the crystalline quality of Ga-doped ZnO film was improved and GZO film has a preferred orientation along with the (002) crystal direction. The transmittance of the GZO film was enhanced by 10% in the visible region from that of the ZnO film. From photoluminescence (PL) data, the ratio of intensity of near band edge (NBE) emission to deep level (DL) emission was as high as 2.65:1 and 1.27:1 in the GZO and ZnO films, respectively. The res istivities of GZO and ZnO films were measured to be 1.27 and 1.61 $\Omega{\cdot}cm$, respectively. The carrier concentrations of ZnO and GZO film were approximately 1018 and 1020 $cm^2$/Vs, respectively. Based on our experimental results, the Ga-doping improves the electrical, structural and optical properties of ZnO film with potential application.