• Korean Journal of Veterinary Service
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• v.33 no.3
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• pp.299-302
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• 2010

This study was conducted to determine the content of heavy metals in meats available on the Korean markets. Trace metals (Pb, As and Cd) were detected in 4 kinds, 172 samples by inductively coupled plasma-mass spectrometry (ICP-MS). The values of heavy metals in meats were as follows; In beef, mean (minimum~maximum) values of the heavy metals were Pb: 0.075 (0.020~0.190)mg/kg, As: 0.010 (0.001~0.050)mg/kg and Cd: 0.43(0.07~2.11)${\mu}g/kg$. In pork, mean (minimum~maximum) values of the heavy metals were Pb: 0.065 (0.012~0.171)mg/kg, As: 0.004 (ND~0.021)mg/kg and Cd: 0.43(0.08~1.09)${\mu}g/kg$. In chiken, mean (minimum~maximum) values of the heavy metals were Pb: 0.060(0.016~0.211)mg/kg, As: 0.008 (ND~0.042)mg/kg and Cd: 0.42 (0.02~3.80)${\mu}g/kg$. In duck, mean (minimum~maximum) values of the heavy metals were Pb: 0.070 (0.011~0.157)mg/kg, As: 0.005 (0.001~0.011)mg/kg and Cd: 0.87 (0.15~3.75)${\mu}g/kg$. This results will be used as a basic data for the future legislation on the regulation and control of heavy metal in meats.

• Communications of Mathematical Education
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• v.24 no.2
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• pp.283-300
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• 2010

It has been recognized for a long time that high school students have difficulty in properly interpreting the form $0^0$. The treatment of $0^0$ was still a subject of a slight controversy among mathematicians until relatively recently. Since the mathematics curriculum in high school does not provide the definite treatment of $0^0$, some students might be inclined to ask what the value of the form is. In this research, we review materials dealing with $0^0$ and analyze historically and mathematically the form, whose true meaning is an indeterminate form. We identify the reality of the mathematics education in high school by conducting simple surveys targeting some high school teachers and the students who graduated from high schools recently. Then we discuss, for teachers and pre-service teachers, how to teach the form $0^0$ in high school mathematics.

• Journal of the Korean Chemical Society
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• v.20 no.4
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• pp.260-265
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• 1976

The conductances of dilute solutions of LiCl, NaCl and KCl in a series of isopropanol-water mixtures were determined at $30^{\circ}C$. The values of equivalent conductance agreed well with Debye-Huckel-Onsager equation and the limiting equivalent conductance was greatly reduced as the isopropanol content of the solvent was increased in accord with predictions based on solvent viscosity and dielectric properties. Also, the limiting equivalent conductance increased in sequence ${\Lambda}_{0,LiCl} < {\Lambda}_{0,NaCl} < {\Lambda}_{0,KCl} in 0.0, 0.1 and 0.2 mole fraction isopropanol, but {\Lambda}_{0,LiCl} < {\Lambda}_{0,KCl} < {\Lambda}_{0,NaCl} in 0.3 mole fraction ispropanol. The maximum Walden product, {\Lambda}_{0{\eta}0}$ was found in 0.1 mole fraction isopropanol for all electrolytes.

• Journal of the Korean Magnetics Society
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• v.8 no.4
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• pp.203-209
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• 1998

Crystallographic and magnetic properties of single phase garnet $Y_{3-x}Bi_xFe_5O_{12}$ (x=0.0, 0.25, 0.5, 0.75, 1.0) were studied by using x-ray diffraction, Mossbauer spectroscopy and vibrating sample magnetometer (VSM). Ultra-fine polycrystalline cubic samples have been prepared by sol-gel method. The lattice constant increase linearly with increasing an amount of Bi. Annealing temperature was larger than 800 $^{\circ}C$ for the growth of a single-phase garnet powder. The second phase of garnet, $(BiFeO_3)$, was at 1000 $^{\circ}C$ for x=0.75, and 950 $^{\circ}C$ for x=1.00. From Mossbauer spectroscopy and VSM measurements, the magnetization and the coercivity were decreased and the Curie temperature $Y_{3-x}Bi_xFe_5O_{12}$(x=0.0, 0.25, 0.5, 0.75, 1.0) was slightly increased as increasing the Bi content.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.9
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• pp.728-732
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• 2011

In this study, piezoelectric and dielectric properties of Lead-free $0.97[(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3]+0.03[(Bi_{0.5}K_{0.5})TiO_3]$ (abbreviated as 0.97NKNS-0.03BKT)ceramics synthesized by conventional solid-state reaction process were investigated as a function of $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition. The results indicated that the $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$ addition significantly improved the sinterability, grain growth and piezoelctric properties of 0.97NKNS-0.03BKT ceramics. The optimum values as planar piezoelectric coupling coefficient ($k_p$= 0.355), piezoelectric constant ($d_{33}$= 207 pC/N) and mechanical quality factor ($Q_m$= 128) were obtained when 0.009KCT was added. The electromechanical coupling factor($k_p$) was slightly decreased according to the increasing temperature.

• Korean Journal of Veterinary Service
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• v.15 no.2
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• pp.144-149
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• 1992

The study was attempted to scrutinize the normal osmotic fragility of erythrocytes in domestic poultry such as chicken, quail and duck making a comparison with that in domestic mammalia such as dog and pig. Osmotic fragility of erythrocytes was determined on blood samples from 10 healthy adult animal in each species. Optical initial hemolysis of erytyrocytes occurred at $0.395{\pm}0.03%$ Nacl for chicken, $0.410{\pm}0.03%$ for duck, $0.440{\pm}0.02%$ for quail, $0.470{\pm}0.05%$ for dog and $0.560{\pm}0.03%$ for pig. Optical complete hemolysis of erytyrocytes occurred at $0.270{\pm}0.02%$ Nacl for chicken, $305{\pm0}.03%$ for duck, $0.360{\pm}0.02%$ for quail, $0.370{\pm}0.03%$ for dog and $0.455{\pm}0.03%$ for p. In other words, erythrocytes of poultry have stronger resistance to osmotic Iysis than that of mammalia, showing the strongest resistance In chicken among the tested poultry.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.320-323
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• 1997

The microwave dielectric properties of X Ba0-$0.15(Nd_{0.87}Bi_{0.13})_2O_3$-(0.85-X) $TiO_2$ ($X=0.13{\sim}0.17$) and 0.16Ba0-$0.15(Bi_xNd_{1-x})_2O_3-0.69TiO_2$ ($X=0.10{\sim}0.16$) ceramics were investigated. Dielectric constant, quality factor and temperature coefficient of resonant frequency of 0.16Ba0-$0.15(Nd_{0.87}Bi_{0.13})_2O_3-0.69TiO_2$ ceramics sintered at $1320^{\circ}C$ for 2 hours were 89.2, 1920(at 4GHz) and 5.2ppm/$^{\circ}C$, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.5 no.3
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• pp.88-96
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• 1972

1. The present paper deals with the contents of heavy metals such as mercury, cadmium, lead and copper in 17 species of edible seaweeds collected from Jumunjin, Pohang, Pusan, Chungmu, Yeosu and Wando areas. 2. The concentration of mercury in the air-dried seaweeds ranged from 0.02 to 0.52 ppm, as shown by the following species: 0.36ppm (0.09-0.50) in Enteromorpha spp., 0.25 ppm (0.14-0.31) in Undaria sp., 0.19 ppm (0.02-0.52) in Porphyra spp., and 0.10ppm (0.02-0.24) in Laminaria spp. in that order. If these concentrations are converted to the wet bases, they will be about 1/4 to 1/5 of the present levels. In general, the samples collected from the east coast showed relatively lower levels than those from the south coast. The mercury concentrations found in the Korean seaweeds are lower than the permissible levels reported. 3. The concentration of cadmium in the air-dried seaweeds ranged from 0.02 to 1.48 ppm, and the levels in the different species showed in the following order: 0.97 ppm (0.41-1.18) in Hizikia sp., 0.33 ppm (0.03-0.63) Undaria sp., and 0.32 ppm (0.04-0.67) in Porphyra spp. The concentration of cadmium in the samples on the wet bases become 1/4 to 1/5 of the present level. The laver Porphyra spp. collected from the east coast showed relatively lower levels than those of the cultured species along the south coast. All of the concentrations are still below than the permissible levels. 4. In general, lead concentration is 0.20-1.31 ppm which is lower than the permissible level. The concentration becomes about 0.05-0.3 ppm on the wet base. 5. Copper concentration ranged from 0.90-17.0 ppn on the dry base which is about 0.2-4.0 ppm on the wet base. It is interesting to note that the samples collected from Busan region showed relatively higher levels than those sampled from other regions.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.1
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• pp.53-64
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• 2020

The Samgwang deposit has been one of the largest deposits in Korea. The deposit consists of series of host rocks including Precambrian metasedimentary rocks and Jurassic Baegunsa formation, which unconformably overlies the Precambrian metasedimentary rocks. The deposit consists of eight lens-shaped quartz veins which filled fractures along fault zones in Precambrian metasedimentary rock, which feature suggest that it is an orogenic-type deposit. Laminated quartz veins are common in the deposit which contain minerals including quartz, ankerite, white mica, chlorite, apatite, rutile, arsenopyrite, sphalerite, chalcopyrite and galena. The structural formulars of white micas from laminated quartz vein and wallrock alteration are determined to be (K_1.02-0.82Na_0.02-0.00Ca_0.00)(Al_1.73-1.58Mg_0.26-0.16Fe_0.23-0.10Mn_0.00Ti_0.03-0.01Cr_0.01-0.00)(Si_3.35-3.22Al_0.79-0.65)O₁₀(OH)₂ and (K_0.75-0.67Na_0.01Ca_0.00) (Al_1.78-1.74Mg_0.16-0.15Fe_0.15-0.13Mn_0.00Ti_0.04-0.02Cr_0.01-0.00)(Si_3.33-3.26Al_0.74-0.67)O₁₀(OH)₂, respectively. It suggest that white mica from laminated quartz vein has higher interlayer cation (K+Na+Ca) and Fe+Mg+Mn+Ti content in octahedral site compared to the white mica from the wallrock alteration. Compositional variations in white mica from laminated quartz vein can be caused by phengitic or Tschermark substitution ((Al³⁺)^VI+(Al³⁺)^IV <-> (Fe²⁺ or Mg²⁺)^VI)+(Si⁴⁺)^IV) and (Fe³⁺)^VI <-> (Al³⁺)^VI substitution. Ankerite from laminated quartz vein has compositional variations of FeO and MgO contents along crystal growth direction. The geochemical and textural features suggest that laminated quartz vein from the Samgwang gold-silver deposit was formed during ductile shear stage, which is an important main gold-silver ore-forming event in orogeinc deposit.

• Korean Journal of Food Science and Technology
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• v.42 no.4
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• pp.383-389
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• 2010

The aim of this study was to determine the methylmercury (MeHg) levels in abyssal fish species. The MeHg in the fishes was extracted with hydrochloric acid and toluene and then purified using an L-cysteine solution. The extract was analyzed with a gas chromatography-electron capture detector (GC-${\mu}ECD$) with a thermon Hg-capillary column. The detection limit and the recovery of the method were 0.002 and 84.2-98.5% (mean, 93.4%), respectively. The MeHg content in 492 abyssal fishes ranged from 0.037 to 2.009 mg/kg. The levels of MeHg [range, mg/kg (mean)] were significantly dependent on fish species and presented as the following; 0.157-2.009 (0.546) in Scalloped hammerhead shark, 0.211-0.878 (0.501) in Blue shark, 0.121-0.993 (0.482) in Spiny dogfish, 0.243-0.658 (0.397) in Salmon shark, 0.074-1.958 (0.353) in Blacktip shark, 0.038-0.807 (0.302) in Southern hake, 0.099-0.511 (0.300) in Scorpion fish, and 0.037-0.133 (0.067) in Ling. The monitoring results showed that the estimated weekly intake of MeHg from sharks, Southern hake, and Ling were lower than the provisional tolerable weekly intake recommended by the Joint FAO/WHO expert committee on food additives.